Name: employing the forced oscillation technique for the assessment of respiratory mechanics in adults
Uploaded: 2022-02-09T13:30:00.000+00:00
Duration: 6 min 11 s
Description: Watch this Scientific Journal Video about Employing the Forced Oscillation Technique for the Assessment of Respiratory Mechanics in Adults at JoVE.com

This work was supported, in part, by contract award #10010115CN2 from the Electric Power Research Institute. The contents do not represent the views of the U.S. Department of Veterans Affairs or the United States Government.

The following protocol was approved by Rutgers University Institutional Review Board. All volunteers participating in this study provided written informed consent prior to all testing.
1. Pre-test preparation
<ol>
	<li>Assess the individual for allergies or sensitivity to mouthpiece or nose clip materials, for oral or facial pain preventing proper seal on the mouthpiece, for an ability to follow directions, and for known sensitivity to the bronchodilating agent that will be used.</li>
	<li>Ensure that the individual dresses comfortably and refrains from exercising or ingesting a heavy meal before testing. Refer to local laboratory policies regarding the use of caffeine, tobacco products, or inhaler before testing.</li>
	<li>Perform FOT first in situations of multiple pulmonary function tests requiring deep breaths.</li>
	<li>Perform testing in a quiet and comfortable environment. Prepare supplies and materials prior to the individual&#39;s arrival.
	<ol>
		<li>Provide an adjustable chair without wheels to ensure that the individual&#39;s feet are flat against the floor.</li>
		<li>Provide the individual with a disposable anti-bacterial filter and nose clip to be used for testing.</li>
		<li>Adhere to local laboratory procedures for donning personal protective equipment when testing.</li>
	</ol>
	</li>
</ol>
2. Verification with impedance test load
<ol>
	<li>Locate the test load object before testing the individual. 
	NOTE:&#160;Static test loads are manufacturer-supplied objects with known impedance (preferably with resistive, elastic, and inertial components) that are specific to each device. Use a test load with an impedance of approximately 15 hPa&#183;s&#183;L-1, which exceeds the expected Zrs for adults.</li>
	<li>Ensure that the test load is factory calibrated (if applicable). 
	NOTE: Some test loads require annual factory recalibration, so follow the protocol outlined in the device manual.
	<ol>
		<li>Consult the manual or contact the manufacturer if the test load for verification is accidentally dropped or visually appears damaged.</li>
	</ol>
	</li>
	<li>Open the calibration or verification menu within the software.</li>
	<li>Firmly insert the test load device into the FOT device and complete the verification procedure according to the manufacturer&#39;s recommendations.</li>
	<li>Review and save the verification results. 
	NOTE: A successful verification ensures that the measured values match the test load within a tolerance of &#8804;+10% or &#177;0.1 hPa&#183;s&#183;L-1. If the verification fails or gives errors, ensure that the test load was properly seated into the FOT device and there is no obstruction in the flow. Consult the manual for troubleshooting tips.</li>
	<li>Verify the device with the test load daily, or immediately before testing.</li>
</ol>
3. Test procedure
<ol>
	<li>Provide standardized instructions and demonstration for the individual.
	<ol>
		<li>Let the individual know about the approximate duration of a single acquisition and the number of replicates that will be taken (see step 3.2).</li>
		<li>Let the individual know about the sensations that they will experience from the oscillations, e.g., fluttering or vibrations in the chest and mouth.</li>
		<li>Let the individual know that the device will start oscillations after a brief period of observation to regulate breathing.</li>
		<li>Instruct the individual to avoid swallowing during the testing period.</li>
		<li>Instruct the individual to sit upright with the feet flat on the floor and the chin facing up for the duration of the testing period.</li>
		<li>Instruct the individual to create a seal with the lips and teeth on the mouthpiece via a demonstration.</li>
		<li>Instruct the individual to keep the tongue relaxed.</li>
		<li>Instruct the individual to firmly place open palms against cheeks with fingertips near the temple and thumbs following the mandibular line. Instruct the individual to keep the elbows slightly flared in a comfortable position to ensure chest expansion.</li>
		<li>Instruct the individual to maintain regular quiet breathing on the mouthpiece until asked by the technician to stop.</li>
	</ol>
	</li>
	<li>Perform measurement session
	<ol>
		<li>Adhere to hygiene and infection control standards as described for spirometry15.</li>
		<li>Attach the anti-bacterial filter to the device. 
		NOTE: Use filters that meet ATS/ERS guidelines with a resistance &#60;1.5 hPa&#183;s&#183;L-1&#160;at a flow rate less than 14 L/s as verified by the manufacturer.</li>
		<li>Provide instructions as described in step 3.1 and ensure that the individual is positioned correctly with the nose clip in place and mouth tightly sealed around the mouthpiece of the device.</li>
		<li>After the individual completes several respiratory cycles of stable, passive, and comfortable tidal breathing, ensure that the device automatically begins acquiring data. Alternatively, the technician may trigger data acquisition using the software.</li>
		<li>Instruct the individual to come off the mouthpiece after at least three artifact-free breaths are acquired during a single acquisition. 
		NOTE:&#160;To achieve three artifact-free breaths, a minimum recording duration of 30 s is recommended. Some FOT devices&#39; settings will automatically stop at a pre-defined recording duration and/or achievement of a certain number of breaths (see section 4 for details on identifying artifacts).</li>
		<li>Adjust the&#160;rest intervals between replicate measurements (approximately 60-90 s) as needed to avoid any physical discomfort.</li>
	</ol>
	</li>
	<li>Optionally, assess the bronchodilator response.
	<ol>
		<li>Administer salbutamol to the individual in accordance with standard laboratory procedures for aerosol medications (e.g., metered dose inhaler, nebulizer) and wait for 15 min16. 
		NOTE: If using a metered dose inhaler with a spacer, administer four separate doses of 100 &#181;g.</li>
		<li>Repeat the same procedures as before (see step 3.2) to obtain post-bronchodilator replicates.</li>
	</ol>
	</li>
</ol>
4. Determining acceptable measurements
<ol>
	<li>Identify artifacts through visual inspection. To do so, monitor the depth (tidal volume; Vt) and rate of breathing (respiratory frequency; fR) in real-time during acquisition to visually ensure stable and quiet breathing patterns from replicate to replicate. 
	NOTE: For each replicate, the average Vt, fR, or their product (minute ventilation, V&#775;E) will be displayed within the software. Compare this value between replicates in order to provide individual feedback on the depth and rate of breathing, if necessary.</li>
	<li>Inspect the replicate manually to exclude artifacts such as cough, swallowing, leak, or other interruptions to flow and pressure traces that can be viewed in real-time.</li>
	<li>Discard any replicates containing negative resistances.</li>
	<li>Review automatic software detection of artifacts. 
	NOTE:&#160;Manufacturers employ software algorithms for detecting artifacts and excluding whole or partial breaths (i.e., inspiration and expiration). Get familiarized with the algorithms applied and report this when summarizing data from a measurement session. Often, these algorithms involve identifying Rrs, Xrs, and breathing patterns outside of normal physiological ranges as well as outliers when comparing breath-by-breath.</li>
	<li>Assess variability
	<ol>
		<li>Acquire at least three acceptable replicates (i.e., those containing &#8805;3 artifact-free breaths). Calculate the within-session coefficient of variation (CoV) for total Rrs at the lowest frequency (e.g., Rrs at 5 Hz). 
		NOTE: CoV is calculated using the following formula: 
		<img alt="Equation 1" src="/files/ftp_upload/63165/63165eq01.jpg" /></li>
		<li>As the acceptable within-session CoV for adults is &#8804;10%, obtain additional replicates if the CoV is &#62;10% or proceed to step 5 if CoV is &#8804;10%. 
		NOTE: Achieving CoV &#8804;10% may be difficult in individuals with airway disease.</li>
	</ol>
	</li>
</ol>
5. Reporting data
<ol>
	<li>Include the following details when reporting FOT results.
	<ol>
		<li>Include the device name, model, software version, and manufacturer.</li>
		<li>Include input stimulus frequency waveform (e.g., pseudo-random noise, multi-frequency) and associated frequency range.</li>
		<li>Include the details on subjective and automatic quality control procedures used to determine acceptable replicates and the number of artifact-free replicates included.</li>
		<li>Include the repeatability or precision of measurement (CoV) and cut-off.</li>
	</ol>
	</li>
	<li>Report the mean of the replicate measurements that were free of artifact and provided a&#160;CoV &#8804;10% for FOT parameters.
	<ol>
		<li>Adhere to laboratory standards regarding which FOT parameters to report. 
		NOTE: While there is currently no consensus on which FOT variables to include, the ERS Technical Standard provides an example of what parameters might be reported as shown in Table 1 for the case example results presented below.</li>
	</ol>
	</li>
	<li>Utilize reference equations from the population being studied using the same FOT device (if available). 
	NOTE: Many reference equations will assume accurate recording of age, sex, height, and weight14.</li>
	<li>Optionally, report both the absolute and relative difference if FOT was performed before and after a bronchodilator. Also, include the dose of salbutamol.</li>
</ol>
6. Quality control and maintenance
<ol>
	<li>Employ a quality control program using biological controls (i.e., &#8805;2 healthy non-smoking individuals) that involves routine testing on a periodic basis.
	<ol>
		<li>Establish a baseline (mean &#177; SD) through the acquisition of 10-20 artifact-free replicate measurements on different days (acquired within 2 weeks) from each biological control.</li>
		<li>Select a low- (5 Hz) and mid-frequency (20 Hz) parameter for resistance and reactance to follow for quality control. On subsequent routine periodic testing, compare the results to the baseline measures. 
		NOTE: Refer to recommended guidance for pulmonary function laboratories17&#160;for additional details on how to assess and enact quality assurance standards. The frequency of biological control testing (e.g., weekly, monthly) should reflect the volume of testing in the laboratory.</li>
	</ol>
	</li>
	<li>Follow the manufacturers&#39; recommendations on regular maintenance such as cleaning, air filter change, software updates, and factory calibration.</li>
</ol>

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All the authors declared no financial conflicts.

The recent ERS Technical Standard on FOT4&#160;emphasizes&#160;the need for greater rigor and standardization of measurement. Close adherence to several critical steps before, during, and after testing is necessary. It is recommended that FOT be performed prior to more effort-dependent maneuvers requiring deep breaths such as body plethysmography and diffusing capacity. End-user verification of test load with known impedance is required at least daily or immediately prior to testing. Clear, consistent, and precise instructions given by trained personnel can minimize extrinsic variabilities in data collection. Each research or clinical laboratory should develop its own protocol implementing the minimal coaching techniques recommended by the ERS technical guidelines. It is critical that during each maneuver the end-users can observe, identify, and correct potential errors that may be encountered, such as mouth leaks, glottic closure, coughing, and unstable breathing patterns. Although certain errors may be difficult to evaluate in real-time, end-users should not solely depend on automatic detection from the specific device used. Acceptable criteria set by the manufacturer should be thoroughly reviewed, and additional criteria should adhere to the ERS statements. Though each device will generate a unique report, standardized reporting of FOT parameters is possible and can facilitate comparison across laboratories and studies. Lastly, rigorous quality control procedures, including routine assessment of healthy biological control(s), must be performed in both research and clinical settings.
Strict adherence to a standardized protocol will minimize variability in performance. However, achieving a CoV &#8804;10% may still be difficult, and perhaps not always possible in those with airway disease. It is incumbent on the technician to strive toward minimizing variability and there are several strategies to consider when a CoV &#8804;10% cannot be obtained. Firstly, ensure the measurement is acquired under similar circumstances for each replicate. This includes monitoring the individual&#39;s posture, hand placement, and adherence to other instructions. The technician may consider repeating initial instructions, providing additional visual demonstration, and offering the individual a prolonged rest interval. Based on experience, it is found that a common reason for excessive variability includes adopting a different sitting position between replicate measurements whereby individuals may re-position themselves to achieve a more comfortable position or strain to reach the mouthpiece. This is most common when using portable FOT devices designed to be held by the technician where the position of the mouthpiece is not fixed. To address this issue, flexible arm mounts may be purchased, which are designed to hold electronic devices like cameras, that can be quickly secured to a desk or table and accommodate individual positioning. After ensuring performance is appropriate and consistent between replicate measurements, the technician should acquire additional replicates.
Unlike spirometry whereby a maximum of eight attempts is recommended to avoid fatigue, there is no maximum number of replicates recommended for FOT likely because of its effort-independent approach. In practice, some investigators acquire up to eight replicate measurements18, and a similar rule of thumb of up to 10 measurements is used in our laboratory. Establishing an upper limit is practically important to define the end of a testing session. Doing so is particularly relevant for individuals with respiratory disease whereby CoV greater than 10% may reflect underlying disease processes rather than poor effort. Harkness et al.18&#160;recently described their experience with these patient populations and suggested that a more liberal cut-off (CoV up to 20%) may still be reportable for clinical interpretation. Each clinic and research laboratory should balance between practical decisions such as time constraint, examinee&#39;s ability and fatigue level, as well as the likelihood of achieving the CoV cutoff. One approach to consider is the implementation of a grading system. For example, once at least three artifact-free replicate measurements are obtained from a maximum of 10 attempts, apply a letter grade corresponding to CoV levels - i.e., &#39;A&#39; &#8804;10%; &#39;B&#39; &#62; 10% and &#8804;15%; &#39;C&#39; &#62; 15% and &#8804;20%; and &#39;D&#39; &#62; 20%. Additional strategies to be considered may include modification of software and hardware acquisition parameters to achieve more complete breaths. For example, some manufacturers have settings to accommodate greater recording durations and/or extended recording epochs to achieve more than the ERS-recommended minimum of three complete breaths. When reporting FOT results, it is imperative to disclose all acquisition parameters to facilitate interpretation and comparison with other published literature. FOT acquisition parameters continue to be actively investigated and will likely result in future modifications to FOT performance and measurement.
In this paper, the aim is to highlight the latest technology and application of FOT as well as provide a standardized protocol for testing in adults. It is, however, important to recognize FOT&#39;s associated limitations. First, impedance measurements are particularly suspect to artifacts such as extra-thoracic influences4. Therefore, the current protocol focuses on minimizing this influence, such as ensuring proper cheek support during acquisition. Additionally, interruptions in flow (e.g., tongue covering the mouthpiece, swallowing, errant breaths) preclude accurate measurement and result in fewer valid breaths for Zrs calculations19. Second, though FOT is easy to perform from the patient&#39;s perspective, identifying these artifacts as well as interpreting the output is challenging for the technician and clinician20. For example, current FOT devices produce a considerable amount of data to characterize an individual&#39;s respiratory mechanics; however, the paucity of reference values and consensus around key variables are factors that slow its clinical adoption. Similarly, while it is recommended to obtain at least three artifact-free trials4, if more than three trials are performed and found acceptable, there is no current consensus on the recommended methods to select which of these trials are used to represent the test session. As such, the clinical utility of FOT in a variety of airway diseases continues to be actively investigated. Lastly, from a technical perspective, there is heterogeneity across FOT manufacturers with respect to the following: i) frequency waveforms, ii) algorithms for error detection, and iii) inter-and intra-breath analyses2,21,22,23,24. Much of the aforementioned limitations may be addressed by following a standardized protocol as well as transparent reporting of output and recording parameters.
Pulmonary function tests traditionally include measurements of lung volumes and capacities, and effectiveness of gas exchange, which require significant instructions, cooperation, and effort from both examiners and examinees. In addition, a mixture of gases at various concentrations is often inhaled during maneuvers, which some might consider invasive techniques. These contrast with FOT, in which mechanical properties of the lungs such as Rrs, elastance, and inertance are examined using less invasive oscillatory frequencies. Thus, FOT can serve as a useful addition to a comprehensive pulmonary function assessment. For example, FOT may afford unique clinical insight in scenarios where symptoms are disproportionate to traditional pulmonary function testing such as those with occupational exposure and/or unexplained dyspnea9,11. Additionally, FOT may also be important for screening those at higher risk for future lung diseases such as asymptomatic smokers25&#160;and those with environmental exposures26. Lastly, more recent data has identified that FOT may also be uniquely helpful for day-to-day monitoring of certain disease conditions such as exercise-induced bronchoconstriction27&#160;and rheumatoid arthritis-related pulmonary symptoms28. The present article focuses on FOT&#39;s application in the adult population, though FOT&#39;s clinical and research utility has been well described in pediatric populations as well29,30.
Future directions for research should further focus on technical and performance aspects of FOT, such as standardizing data presentation and reporting, as well as characterizing associated variability and repeatability. In clinical settings, FOT can be widely used for the assessment of dyspnea and early detection of chronic airway diseases or systemic disease-associated pulmonary manifestations in all age groups.

The forced oscillation technique (FOT) or oscillometry was first introduced over 60 years ago1&#160;and affords measurement of respiratory mechanics via externally applied pressure oscillations superimposed during tidal breathing. In brief, pressure and airflow are measured at the mouth by transducers across a range of frequencies. Spectral analysis is then used to determine impedance (Zrs) or the amplitude and phase differences between pressure and airflow at each frequency2,3. Zrs represents the sum of forces opposing pressure oscillations and is typically characterized by components of resistance (Rrs) and reactance (Xrs). Rrs reflects the dissipative mechanical properties of the respiratory system (energy dissipation), whereas Xrs reflects dynamic elastance and inertia of the respiratory system (energy storage). Zrs assessment at multiple oscillation frequencies further allows assessment of the uniformity of airflow distribution. For a review of FOT signal processing, physiological principles, and applications: please refer to the European Respiratory Society (ERS) Task Force statements2,4.
FOT is not a substitute for spirometry, rather a complementary assessment of the lung function. It may, however, offer several advantages over spirometric testing including measurements performed during tidal breathing (effort-independent) and potential for assessing the distal or small airways that are not feasible with spirometry5. As a result, FOT has gained considerable popularity in the pediatric setting6,7, as well as for the evaluation of the symptomatic patient with normal or preserved spirometry8,9,10,11. FOT has also demonstrated clinical utility during bronchoprovocation testing whereby symptoms are more strongly associated with FOT than spirometry12. Moreover, FOT necessitates lower doses of bronchoprovocative agents to induce measurable differences in respiratory function13.
In light of these findings, interest in FOT for clinical practice and research has surged in recent years. In fact, according to a Scopus search conducted in July 2021 for the terms &#39;forced oscillation technique&#39; or &#39;impulse oscillometry&#39;, the median number of publications on FOT increased from 35 per year (2000-2010) to 94 per year (2010-2020). Despite this surge of interest, standardization in the acquisition and reporting of FOT data has only recently received greater attention with the recent ERS Technical Standards for Respiratory Oscillometry4. At present, several FOT systems are commercially available that vary by pressure signal type (e.g., pseudorandom, train of impulses), recording epoch, frequency range, and resolution14. Despite these differences, the acquisition and reporting of FOT data as performed by the technician can follow a universal approach which is the focus of the present manuscript. Herein, a standardized protocol is provided that is consistent with the ERS Technical Standards4. This protocol is illustrated through practical examples with research and clinical data acquired in our laboratory. Specifically, the focus is on the application and interpretation of FOT in the clinical evaluation of adult dyspnea.

<table><tbody><tr><td>Quark i2M</td><td>Cosmed</td><td>n/a</td><td>https://www.cosmed.com/en/products/pulmonary-function/quark-i2m&lt;br/&gt; &lt;strong&gt;Software (version):&lt;/strong&gt; PFTSuite (10.0e)&lt;br/&gt; &lt;strong&gt;Signal Type:&lt;/strong&gt; Pseudo-random&lt;br/&gt; &lt;strong&gt;Frequencies (Hz):&lt;/strong&gt; 4, 6, 8, ..., 48</td></tr><tr><td>Resmon Pro</td><td>MGC Diagnostics</td><td>n/a</td><td>https://mgcdiagnostics.com/products/resmon-pro-v3-forced-oscillation-technique&lt;br/&gt; &lt;strong&gt;Software (version):&lt;/strong&gt; Pro Full (v3)&lt;br/&gt; &lt;strong&gt;Signal Type:&lt;/strong&gt; Pseudorandom, relative primes&lt;br/&gt; &lt;strong&gt;Frequencies (Hz):&lt;/strong&gt; 5, 11, 19</td></tr><tr><td>Tremoflo C-100</td><td>Thorasys</td><td>n/a</td><td>https://www.thorasys.com/&lt;br/&gt; &lt;strong&gt;Software (version):&lt;/strong&gt; tremfolo (1.0.43)&lt;br/&gt; &lt;strong&gt;Signal Type:&lt;/strong&gt; Pseudo-random, relative primes&lt;br/&gt; &lt;strong&gt;Frequencies (Hz):&lt;/strong&gt; 5, 11, 14, 17, 19, 23, 29, 31, 37</td></tr></tbody></table>

employing the forced oscillation technique for the assessment of respiratory mechanics in adults

There is increasing interest in the use of the forced oscillation technique (FOT) or oscillometry to characterize respiratory mechanics in healthy and diseased individuals. FOT, a complementary method to traditional pulmonary function testing, utilizes a range of oscillatory frequencies superimposed on tidal breathing to measure the functional relationship between airway pressure and flow. This passive assessment provides an estimate of respiratory system resistance (Rrs) and reactance (Xrs) that reflect airway caliber and energy storage and dissipation, respectively. Despite the recent increase in popularity and updated Technical Standards, clinical adoption has been slow which relates, in part, to the lack of standardization regarding the acquisition and reporting of FOT data. The goal of this article is to address the lack of standardization across laboratories by providing a comprehensive written protocol for FOT and an accompanying video. To illustrate that this protocol can be utilized irrespective of a particular device, three separate FOT devices have been employed in the case examples and video demonstration. This effort is intended to standardize the use and interpretation of FOT, provide practical suggestions, as well as highlight future questions that need to be addressed.

First, a case of a healthy adult is presented as a practical example of data acquisition and how the technician selects individual measurements for reporting (Case Example 1). Second, a clinical example is provided of a patient referred for unexplained dyspnea for FOT acquisition before and after a bronchodilator with emphasis on interpretation (Case Example 2). Note that FOT devices from two different manufacturers have been purposefully used in these case examples to illustrate a universal approach. Additional details are provided in the Table of Materials.
Case Example 1 
FOT was performed in a healthy 25-year-old Hispanic female (Height: 164 cm, Weight: 84.9 kg). The participant was a never-smoker, denied respiratory symptoms, and had no history of lung disease or other significant past medical history. She had abstained from caffeine (&#8805;8 h) and vigorous exercise (&#8805;24 h). She had a recent spirometric examination that was read as normal without signs of obstruction or restriction: FEV1/FVC: 0.88, FEV1: 3.30 L (98% predicted), and FVC: 3.70 L (97% predicted).
After explaining and demonstrating test procedures, three FOT measurements were obtained with approximately 1-2 min between recordings. Visual inspection and the software&#39;s quality control algorithm did not identify any artifacts. Rrs at 5 Hz for the first three measurements was&#160;then examined to confirm within-session CoV (individual measurements: 3.06, 3.79, 3.46 hPa&#183;s &#183;L-1; average: 3.44 hPa&#183;s&#183;L-1, standard Deviation: 0.36 hPa&#183;s L-1, CoV = standard deviation / average = 0.36 / 3.44 = 0.105 * 100 = 10.5%).
Since the CoV of the first three measurements was &#62;10%, additional measurements were&#160;necessary. A fourth measurement was obtained (Rrs at 5 Hz = 3.40 hPa&#183;s&#183;L-1) and within-session CoV was recalculated using all measurements (individual measurements: 3.06, 3.79, 3.46, 3.40 hPa&#183;s&#183;L-1; average: 3.43 hPa&#183;s&#183;L-1; standard Deviation: 0.30 hPa&#183;s&#183;L-1; CoV = standard deviation / average = 0.30 / 3.43 = 0.087 * 100 = 8.7%)
Because the within-session CoV criteria were&#160;met, average FOT indices were calculated as the average of measurements. These measurements are illustrated in Figure 1&#160;and reported in Table 1. Additionally, to facilitate comparison to expected values, Table 2&#160;presents predicted values across all FOT indices (where predicted values are available), lower limits of normal (LLN), upper limits of normal (ULN), % of predicted and Z-scores using standard reference equations that consider age, sex, and weight14.
Case Example 2 
A 48-year-old Caucasian male (Height: 185 cm, Weight: 89 kg) was referred to our center for evaluation of chronic cough and exertional dyspnea without obvious cause (e.g., medication, respiratory or cardiovascular disease, or mental health comorbidity). He was a lifetime never-smoker but endorsed exposure to vapors, gases, dust, and fumes during a 7-month military deployment to Iraq. Complete pulmonary function testing was performed (i.e., body plethysmography, bronchodilator spirometry, and lung diffusing capacity for carbon monoxide) and all results were within normal limits. FOT was performed before and 15 min after administration of bronchodilator (4 puffs of 100 &#181;g salbutamol via metered-dose inhaler with spacer) (Figure 2). The individual trial data and mean values are presented in Table 3&#160;pre- and post-bronchodilator administration; as each trial was technically acceptable, the pre- and post-bronchodilator measurements, as well as their absolute and relative difference, are reported in Table 4. In addition, predicted values, % of predicted, LLN, and ULN are also reported using standard reference equations that consider age, sex, and weight14.
We delimited variables reported in Table 3 and Table 4 to simplify the illustration of two concepts: 1) determining abnormal versus normal responses, and 2) bronchodilator reversibility. For Rrs measurements, values that exceed the ULN (i.e., elevated resistance) are considered abnormal. Here, pre-bronchodilator Rrs at 4 Hz (3.32 hPa&#183;s&#183;L-1) exceeds the ULN (2.59 hPa&#183;s&#183;L-1) and is 155% of the predicted value ([3.32 / 2.14] * 100 = 155.14). Following bronchodilator administration, Rrs at 4 Hz was reduced by 45.78% exceeding the 95th percentile reported by Oostveen et al.14&#160;(i.e., -32% for Rrs at 4 Hz). This response would indicate a positive bronchodilator response in resistance. Additionally, the post-bronchodilator observed value is normalized (i.e., became representative of what is considered a normal value) and is 84.1% of the predicted value ([1.80 / 2.14] * 100 = 84.11).
Xrs at 4 Hz is interpreted differently as observed values are negative. Therefore, abnormal values are those that exceed the LLN (i.e., more negative reactance). Here, the individual had a pre-bronchodilator (-0.98 hPa&#183;s&#183;L-1) and post-bronchodilator (-0.83 hPa&#183;s&#183;L-1) values that are above the LLN (-1.11 hPa&#183;s&#183;L-1). The difference in pre- versus post-bronchodilator was approximately 15%, which is below the 95th percentile reported by Oostveen et al.14&#160;(i.e., +33.8% in Xrs at 4 Hz). Therefore, all Xrs values are considered normal.
Reactance area (or AX) is the integrated area of low-frequency reactance and, therefore, is a positive value. Abnormal AX values are those that exceed the ULN, reflecting more negative reactance. Like Xrs at 4 Hz, pre-bronchodilator AX (2.77 hPa&#183;s&#183;L-1) and post-bronchodilator AX (1.23 hPa&#183;s&#183;L-1) are both below the ULN. Although there was a reduction of -55% from pre- to post-bronchodilator value, this falls below the 95th percentile reported by Oostveen et al.14&#160;(i.e., -56.0% for AX at 4 Hz). Taken together, AX is considered normal as well.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/63165/63165fig01.jpg" /> 
Figure 1: Respiratory resistance (Rrs) and reactance (Xrs) as a function of oscillation frequency (Hz) in a healthy adult. Mean &#177; SD of all replicates are plotted for Rrs (blue circles) and Xrs (red squares)&#160;at each measured frequency. Each data point represents total or whole-breath measurements. Data were collected using a device that employs a pseudorandom, relative primes signal type in the 5-37 Hz range. Please see the Table of Materials for additional details regarding this device. <a href="https://www.jove.com/files/ftp_upload/63165/63165fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/63165/63165fig02.jpg" /> 
Figure 2: Pre- and post-bronchodilator assessment. Respiratory resistance (Rrs; blue) and reactance (Xrs; red) before (open circles) and after (open triangles) bronchodilator administration. Dashed red lines represent the upper and lower limits of normal for Rrs and Xrs, respectively14. Data were collected using a device that employs a pseudorandom signal type in the 4-48 Hz range. Please see the Table of Materials for additional details regarding this device. <a href="https://www.jove.com/files/ftp_upload/63165/63165fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Variable</td>
			<td>T1</td>
			<td>T2</td>
			<td>T3</td>
			<td>T4</td>
			<td>Avg</td>
			<td>SD</td>
		</tr>
		<tr>
			<td>Rrs5</td>
			<td>3.06</td>
			<td>3.79</td>
			<td>3.46</td>
			<td>3.40</td>
			<td>3.43</td>
			<td>0.30</td>
		</tr>
		<tr>
			<td>Rrs5 (insp)</td>
			<td>3.30</td>
			<td>3.45</td>
			<td>3.34</td>
			<td>3.64</td>
			<td>3.43</td>
			<td>0.15</td>
		</tr>
		<tr>
			<td>Rrs11</td>
			<td>2.77</td>
			<td>4.02</td>
			<td>3.08</td>
			<td>2.89</td>
			<td>3.19</td>
			<td>0.57</td>
		</tr>
		<tr>
			<td>Rrs19</td>
			<td>2.92</td>
			<td>3.71</td>
			<td>3.30</td>
			<td>3.13</td>
			<td>3.27</td>
			<td>0.33</td>
		</tr>
		<tr>
			<td>Rrs5-19</td>
			<td>0.14</td>
			<td>0.08</td>
			<td>0.15</td>
			<td>0.26</td>
			<td>0.16</td>
			<td>0.08</td>
		</tr>
		<tr>
			<td>Xrs5</td>
			<td>-0.90</td>
			<td>-0.76</td>
			<td>-0.69</td>
			<td>-0.90</td>
			<td>-0.81</td>
			<td>0.11</td>
		</tr>
		<tr>
			<td>Xrs5 (insp)</td>
			<td>-1.44</td>
			<td>-0.91</td>
			<td>-0.86</td>
			<td>-1.08</td>
			<td>-1.07</td>
			<td>0.26</td>
		</tr>
		<tr>
			<td>Xrs5 (exp)</td>
			<td>-0.63</td>
			<td>-0.46</td>
			<td>-0.55</td>
			<td>-0.77</td>
			<td>-0.60</td>
			<td>0.13</td>
		</tr>
		<tr>
			<td>Delta Xrs5</td>
			<td>-0.81</td>
			<td>-0.45</td>
			<td>-0.31</td>
			<td>-0.31</td>
			<td>-0.47</td>
			<td>0.24</td>
		</tr>
		<tr>
			<td>Xrs11</td>
			<td>-0.04</td>
			<td>-0.09</td>
			<td>0.00</td>
			<td>-0.09</td>
			<td>-0.06</td>
			<td>0.04</td>
		</tr>
		<tr>
			<td>Xrs19</td>
			<td>0.92</td>
			<td>0.86</td>
			<td>1.12</td>
			<td>0.94</td>
			<td>0.96</td>
			<td>0.11</td>
		</tr>
		<tr>
			<td>AX</td>
			<td>2.83</td>
			<td>2.57</td>
			<td>2.05</td>
			<td>2.98</td>
			<td>2.61</td>
			<td>0.41</td>
		</tr>
		<tr>
			<td>Fres</td>
			<td>11.27</td>
			<td>11.62</td>
			<td>10.99</td>
			<td>11.57</td>
			<td>11.36</td>
			<td>0.29</td>
		</tr>
		<tr>
			<td>Vt</td>
			<td>0.90</td>
			<td>0.98</td>
			<td>0.95</td>
			<td>0.61</td>
			<td>0.86</td>
			<td>0.17</td>
		</tr>
	</tbody>
</table>
Table 1: Standard reporting of select FOT parameters: Trials summary. This table illustrates all measurement replicates across trials (T1-T4) and their summary statistics (averages and standard deviations (SD)). The average values across all trials are used to represent the test session. Common parameters are listed under Variable. Resistance (Rrs) and reactance (Xrs) are provided for whole breaths at 5, 11, and 19 Hz, as well as during inspiration at 5 Hz (Rrs5(insp) and Xrs5(insp)). Additional parameters reported include reactance area (AX) at 5 Hz, resonant frequency (Fres), and tidal volume (Vt).
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Variable</td>
			<td>Predicted</td>
			<td>LLN</td>
			<td>ULN</td>
			<td>Baseline Avg</td>
			<td>% of Predicted</td>
			<td>Z Score</td>
		</tr>
		<tr>
			<td>Rrs5</td>
			<td>3.76</td>
			<td>-</td>
			<td>4.11</td>
			<td>3.43</td>
			<td>91%</td>
			<td>-0.34</td>
		</tr>
		<tr>
			<td>Rrs5 (insp)</td>
			<td>-</td>
			<td>-</td>
			<td>-</td>
			<td>3.43</td>
			<td>-</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Rrs11</td>
			<td>2.74</td>
			<td>-</td>
			<td>3.18</td>
			<td>3.19</td>
			<td>116%</td>
			<td>-0.33</td>
		</tr>
		<tr>
			<td>Rrs19</td>
			<td>3.52</td>
			<td>-</td>
			<td>3.92</td>
			<td>3.27</td>
			<td>93%</td>
			<td>-0.3</td>
		</tr>
		<tr>
			<td>Rrs5-19</td>
			<td>0.14</td>
			<td>-</td>
			<td>-</td>
			<td>0.16</td>
			<td>118%</td>
			<td>0.05</td>
		</tr>
		<tr>
			<td>Xrs5</td>
			<td>-1.37</td>
			<td>-1.50</td>
			<td>-</td>
			<td>-0.81</td>
			<td>59%</td>
			<td>1.32</td>
		</tr>
		<tr>
			<td>Xrs5 (insp)</td>
			<td>-</td>
			<td>-</td>
			<td>-</td>
			<td>-1.07</td>
			<td>-</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Xrs5 (exp)</td>
			<td>-</td>
			<td>-</td>
			<td>-</td>
			<td>-0.60</td>
			<td>-</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Delta Xrs5</td>
			<td>-</td>
			<td>-</td>
			<td>-</td>
			<td>-0.47</td>
			<td>-</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Xrs11</td>
			<td>-0.14</td>
			<td>-0.26</td>
			<td>-</td>
			<td>-0.05</td>
			<td>36%</td>
			<td>0.22</td>
		</tr>
		<tr>
			<td>Xrs19</td>
			<td>-</td>
			<td>-</td>
			<td>-</td>
			<td>0.96</td>
			<td>-</td>
			<td>-</td>
		</tr>
		<tr>
			<td>AX</td>
			<td>4.08</td>
			<td></td>
			<td>5.11</td>
			<td>2.61</td>
			<td>64%</td>
			<td>-0.64</td>
		</tr>
		<tr>
			<td>Fres</td>
			<td>12.73</td>
			<td>-</td>
			<td>13.14</td>
			<td>11.36</td>
			<td>89%</td>
			<td>-</td>
		</tr>
	</tbody>
</table>
Table 2: Standard reporting of select FOT parameters: Reference and predicted values. There is currently no consensus on which FOT parameters to include in a basic report; however, the ERS Technical Standard provides an example of what parameters might be reported4, which are included in the accompanying table. This table illustrates the averaged measurement values reported from the test session as well as the accompanying reference values currently available. Common parameters are listed under Variable. Resistance (Rrs) and reactance (Xrs) are provided for whole breaths at 5, 11, and 19 Hz, as well as during inspiration at 5 Hz (Rrs5(insp) and Xrs5(insp)). Additional parameters reported include reactance area (AX) at 5 Hz and resonant frequency (Fres). For those parameters with reference values available14, predicted, % predicted, lower and upper limits of normal (LLN, ULN), and Z-score values are also calculated.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td></td>
			<td colspan="5">Pre-Bronchodilator</td>
			<td colspan="5">Post-Bronchodilator</td>
		</tr>
		<tr>
			<td>Variable</td>
			<td>T1</td>
			<td>T2</td>
			<td>T3</td>
			<td>Avg</td>
			<td>SD</td>
			<td>T1</td>
			<td>T2</td>
			<td>T3</td>
			<td>Avg</td>
			<td>SD</td>
		</tr>
		<tr>
			<td>Rrs</td>
			<td>3.34</td>
			<td>3.21</td>
			<td>3.42</td>
			<td>3.32</td>
			<td>0.11</td>
			<td>1.81</td>
			<td>1.89</td>
			<td>1.69</td>
			<td>1.80</td>
			<td>0.10</td>
		</tr>
		<tr>
			<td>Xrs</td>
			<td>-1.25</td>
			<td>-0.72</td>
			<td>-0.98</td>
			<td>-0.98</td>
			<td>0.26</td>
			<td>-0.42</td>
			<td>-1.32</td>
			<td>-0.74</td>
			<td>-0.83</td>
			<td>0.45</td>
		</tr>
		<tr>
			<td>AX</td>
			<td>2.50</td>
			<td>2.02</td>
			<td>2.79</td>
			<td>2.44</td>
			<td>0.39</td>
			<td>0.73</td>
			<td>1.95</td>
			<td>1.01</td>
			<td>1.23</td>
			<td>0.64</td>
		</tr>
	</tbody>
</table>
Table 3: Interpreting low-frequency resistance (Rrs), reactance (Xrs), and reactance area (AX): Trials summary. This table illustrates all measurement replicates across trials (pre- and post-bronchodilator) and their summary statistics (averages and standard deviations (SD)). The average values across all trials are used to represent the test session&#39;s values for baseline averages (pre-bronchodilator) and post-bronchodilator averages.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Variable</td>
			<td>Predicted</td>
			<td>LLN</td>
			<td>ULN</td>
			<td>Baseline Avg</td>
			<td>% of Predicted</td>
			<td>Post BD Avg</td>
			<td>% of Predicted</td>
			<td>Absolute Change</td>
			<td>% Change</td>
		</tr>
		<tr>
			<td>Rrs</td>
			<td>2.14</td>
			<td>NA</td>
			<td>2.59</td>
			<td>3.32</td>
			<td>155%</td>
			<td>1.80</td>
			<td>84%</td>
			<td>1.52</td>
			<td>-45.78%</td>
		</tr>
		<tr>
			<td>Xrs</td>
			<td>-0.97</td>
			<td>-1.11</td>
			<td>NA</td>
			<td>-0.98</td>
			<td>101%</td>
			<td>-0.83</td>
			<td>86%</td>
			<td>-0.15</td>
			<td>15.31%</td>
		</tr>
		<tr>
			<td>AX</td>
			<td>2.15</td>
			<td>NA</td>
			<td>3.08</td>
			<td>2.44</td>
			<td>113%</td>
			<td>1.23</td>
			<td>57%</td>
			<td>1.21</td>
			<td>-49.59%</td>
		</tr>
	</tbody>
</table>
Table 4: Interpreting low-frequency resistance (Rrs), reactance (Xrs), and reactance area (AX): Reference and predicted values. Low-frequency (4 Hz) Rrs, Xrs, and AX are reported along with the corresponding predicted values, % of predicted, and the lower (LLN) and upper (ULN) limits of normal14. Measurements before (Baseline Avg) and after (Post BD Avg) bronchodilator are presented along with their corresponding absolute and relative change (% Change).

Watch this Scientific Journal Video about Employing the Forced Oscillation Technique for the Assessment of Respiratory Mechanics in Adults at JoVE.com

Employing the Forced Oscillation Technique for the Assessment of Respiratory Mechanics in Adults

As the use of forced oscillation technique (FOT) is increasingly utilized to characterize respiratory mechanics, there is a need to standardize methods with respect to nascent technical guidelines and various manufacturer's recommendations. A detailed protocol is provided including FOT assessment and interpretation for two cases to facilitate the standardization of methods.

There is increasing interest in the use of the forced oscillation technique (FOT) or oscillometry to characterize respiratory mechanics in healthy and ...

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5.4K Views.  VA NJ Health Care System. As the use of forced oscillation technique (FOT) is increasingly utilized to characterize respiratory mechanics, there is a need to standardize methods with respect to nascent technical guidelines and various manufacturer's recommendations. A detailed protocol is provided including FOT assessment and interpretation for two cases to facilitate the standardization of methods.

Video: Employing the Forced Oscillation Technique for the Assessment of Respiratory Mechanics in Adults

Osteopathic Manipulative Treatment as a Useful Adjunctive Tool for Pneumonia

Pneumonia, the inflammatory state of lung tissue primarily due to microbial infection, claimed 52,306 lives in the United States in 20071 and resulted in the hospitalization of 1.1 million patients2. With an average length of in-patient hospital stay of five days2, pneumonia and influenza comprise significant financial burden costing the United States $40.2 billion in 20053. Under the current Infectious Disease Society of America/American Thoracic Society guidelines, standard-of-care recommendations include the rapid administration of an appropriate antibiotic regiment, fluid replacement, and ventilation (if necessary). Non-standard therapies include the use of corticosteroids and statins; however, these therapies lack conclusive supporting evidence4. (Figure 1)

Osteopathic Manipulative Treatment (OMT) is a cost-effective adjunctive treatment of pneumonia that has been shown to reduce patients&#8217; length of hospital stay, duration of intravenous antibiotics, and incidence of respiratory failure or death when compared to subjects who received conventional care alone5. The use of manual manipulation techniques for pneumonia was first recorded as early as the Spanish influenza pandemic of 1918, when patients treated with standard medical care had an estimated mortality rate of 33%, compared to a 10% mortality rate in patients treated by osteopathic physicians6. When applied to the management of pneumonia, manual manipulation techniques bolster lymphatic flow, respiratory function, and immunological defense by targeting anatomical structures involved in the these systems7,8, 9, 10.

The objective of this review video-article is three-fold: a) summarize the findings of randomized controlled studies on the efficacy of OMT in adult patients with diagnosed pneumonia, b) demonstrate established protocols utilized by osteopathic physicians treating pneumonia, c) elucidate the physiological mechanisms behind manual manipulation of the respiratory and lymphatic systems. Specifically, we will discuss and demonstrate four routine techniques that address autonomics, lymph drainage, and rib cage mobility: 1) Rib Raising, 2) Thoracic Pump, 3) Doming of the Thoracic Diaphragm, and 4) Muscle Energy for Rib 1.5,11

Pneumonia is one of the top ten leading causes of death in the U.S. Osteopathic manipulative techniques (OMT) may be utilized as an adjunctive therapy in the treatment of pneumonia to enhance biomechanical and immune function; and ultimately, to reduce hospital stay, duration of antibiotics, incidence of respiratory failure, and mortality. In this video-article, we will review randomized controlled studies on the use of OMT in pneumonia patients, as well as demonstrate specific hands-on techniques that are routinely practiced by osteopathic physicians when treating pulmonary infections.

Pneumonia, the inflammatory state of lung tissue primarily due to microbial infection, claimed 52,306 lives in the United States in 20071 and resulted in ...

Method to Obtain Pattern of Breathing in Senescent Mice through Unrestrained Barometric Plethysmography

Unrestrained barometric plethysmography (UBP) is a method for quantifying the pattern of breathing in mice, where breathing frequency, tidal volume, and minute ventilation are routinely reported. Moreover, information can be collected regarding the neural output of breathing, including the existence of central apneas and augmented breaths. An important consideration for UBP is obtaining a breathing segment with a minimal impact of anxious or active behaviors, to elucidate the response to breathing challenges. Here, we present a protocol that allows for short, quiet baselines to be obtained in aged mice, comparable to waiting for longer bouts of quiet breathing. The use of shorter time segments is valuable, as some strains of mice may be increasingly excitable or anxious, and longer periods of quiet breathing may not be achieved within a reasonable timeframe. We placed 22 month-old mice in a UBP chamber and compared four 15 s quiet breathing segments between minutes 60&#8211;120 to a longer 10 min quiet breathing period that took&#160;2&#8211;3 h to acquire. We also obtained counts of central apneas and augmented breaths prior to the quiet breathing segments, following a 30 min familiarization period. We show that 10 min of quiet breathing is comparable to using a much shorter 15 s duration. Additionally, the time leading up to these 15 s quiet breathing segments can be used to gather data regarding apneas of central origin. This protocol allows investigators to collect pattern-of-breathing data in a set amount of time and makes quiet baseline measures feasible for mice that may exhibit increased amounts of excitable behavior. The UBP methodology itself provides a useful and noninvasive way to collect pattern-of-breathing data and allows for mice to be tested over several time points.

Unrestrained barometric plethysmography is used to quantify the pattern of breathing in awake mice. We show that 15 s segments under a standardized protocol display similar values to an extended duration of quiet breathing. This methodology also allows for the quantification of apnea and augmented breaths during the first hour in the chamber.

Unrestrained barometric plethysmography (UBP) is a method for quantifying the pattern of breathing in mice, where breathing frequency, tidal volume, and ...

Behavior

Investigation into Deep Breathing through Measurement of Ventilatory Parameters and Observation of Breathing Patterns

In this protocol, two deep breathing patterns were shown to 15 participants to determine an easy yet effective method of breathing exercise for future application in a clinical setting. The women in their twenties were seated comfortably in a chair with back support. They were fitted with an airtight mask connected to a&#160;gas analyzer. Three electrodes were placed on the chest connected to a wireless transmitter for relaying to the electrocardiograph. They executed a 5 min rest phase, followed by 5 min of deep breathing with a natural breathing pattern, terminating with a 5 min rest phase. This was followed by a 10 min intermission before commencing the second instruction phase of substituting the natural breathing pattern with the diaphragmatic breathing pattern. Simultaneously, the following took place: a) continuous collection, measurement and analysis of the expired gas to assess the ventilatory parameters on a breath-by-breath basis; b) measurement of the heart rate by an electrocardiograph; and c) videotaping of the participant&#8217;s thoracoabdominal movement from a lateral aspect. From the video capture, the investigators carried out visual observation of the fast-forward motion-images followed by classification of the breathing patterns, confirming that the participants had carried out the method of deep breathing as instructed. The amount of oxygen uptake revealed that, during deep breathing, the work of breathing decreased. The results from the expired minute ventilation, respiration rate and tidal volume confirmed increased ventilatory efficiency for deep breathing with the natural breathing pattern compared to that with the diaphragmatic breathing pattern. This protocol suggests a suitable method of instruction for assessing deep breathing exercises on the basis of oxygen consumption, ventilatory parameters, and chest wall excursion.

Here, we present a protocol to assess two deep breathing patterns of natural and diaphragmatic breathing for their effectiveness and ease of execution. Fifteen participants were selected, utilizing an electrocardiograph and expired gas analyzer for measurement of the ventilatory parameters, together with visual assessment by video capture of thoracoabdominal movement.

In this protocol, two deep breathing patterns were shown to 15 participants to determine an easy yet effective method of breathing exercise for future ...

Evaluation of Respiratory System Mechanics in Mice using the Forced Oscillation Technique

The forced oscillation technique (FOT) is a powerful, integrative and translational tool permitting the experimental assessment of lung function in mice in a comprehensive, detailed, precise and reproducible manner. It provides measurements of respiratory system mechanics through the analysis of pressure and volume signals acquired in reaction to predefined, small amplitude, oscillatory airflow waveforms, which are typically applied at the subject's airway opening. The present protocol details the steps required to adequately execute forced oscillation measurements in mice using a computer-controlled piston ventilator (flexiVent; SCIREQ Inc, Montreal, Qc, Canada). The description is divided into four parts: preparatory steps, mechanical ventilation, lung function measurements, and data analysis. It also includes details of how to assess airway responsiveness to inhaled methacholine in anesthetized mice, a common application of this technique which also extends to other outcomes and various lung pathologies. Measurements obtained in na&iuml;ve mice as well as from an oxidative-stress driven model of airway damage are presented to illustrate how this tool can contribute to a better characterization and understanding of studied physiological changes or disease models as well as to applications in new research areas.

The present protocol provides a detailed step-by-step description of the procedures required to execute measurements of respiratory system mechanics as well as the assessment of airway responsiveness to inhaled methacholine in mice using the forced oscillation technique (flexiVent; SCIREQ Inc, Montreal, Qc, Canada).

The  forced oscillation technique (FOT) is a powerful, integrative and translational  tool permitting the experimental assessment of lung function in mice ...

Biology

Assessment of Respiratory Function in Conscious Mice by Double-chamber Plethysmography

Air volume changes created by a conscious subject breathing spontaneously within a body box are at the basis of plethysmography, a technique used to non-invasively assess some features of the respiratory function in humans as well as in laboratory animals. The present article focuses on the application of the double-chamber plethysmography (DCP) in small animals. It provides background information on the methodology as well as a detailed step-by-step procedure to successfully assess respiratory function in conscious, spontaneously breathing animals in a non-invasive manner. The DCP can be used to monitor the respiratory function of multiple animals in parallel, as well as to identify changes induced by aerosolized substances over a chosen time period and in a repeated manner. Experiments on control and allergic mice are used herein to demonstrate the utility of the technique, explain the associated outcome parameters, as well as to discuss the related advantages and shortcomings. Overall, the DCP provides valid and theoretically sound readouts that can be trusted to evaluate the respiratory function of conscious small animals both at baseline and after challenges with aerosolized substances.

The objective of the present article is to provide a detailed description of the recommended procedures to evaluate respiratory function in conscious mice by double-chamber plethysmography.

Air volume changes created by a conscious subject breathing spontaneously within a body box are at the basis of plethysmography, a technique used to ...

Measuring Respiratory Function in Mice Using Unrestrained Whole-body Plethysmography

Respiratory dysfunction is one of the leading causes of morbidity and mortality in the world and the rates of mortality continue to rise. Quantitative assessment of lung function in rodent models is an important tool in the development of future therapies. Commonly used techniques for assessing respiratory function including invasive plethysmography and forced oscillation. While these techniques provide valuable information, data collection can be fraught with artefacts and experimental variability due to the need for anesthesia and/or invasive instrumentation of the animal. In contrast, unrestrained whole-body plethysmography (UWBP) offers a precise, non-invasive, quantitative way by which to analyze respiratory parameters. This technique avoids the use of anesthesia and restraints, which is common to traditional plethysmography techniques. This video will demonstrate the UWBP procedure including the equipment set up, calibration and lung function recording. It will explain how to analyze the collected data, as well as identify experimental outliers and artefacts that results from animal movement. The respiratory parameters obtained using this technique include tidal volume, minute volume, inspiratory duty cycle, inspiratory flow rate and the ratio of inspiration time to expiration time. UWBP does not rely on specialized skills and is inexpensive to perform. A key feature of UWBP, and most appealing to potential users, is the ability to perform repeated measures of lung function on the same animal.

The assessment of respiratory physiology has traditionally relied upon techniques, which require restraint or sedation of the animal. Unrestrained whole-body plethysmography, however, provides precise, non-invasive, quantitative analysis of respiratory physiology in animal models. In addition, the technique allows repeated respiratory assessment of mice allowing for longitudinal studies.

Respiratory dysfunction is one of the leading causes of morbidity and mortality in the world and the rates of mortality continue to rise. Quantitative ...

Conducting Respiratory Oscillometry in an Outpatient Setting

Respiratory oscillometry is a different modality of pulmonary function testing that is increasingly used in a clinical and research setting to provide information regarding lung mechanics. Respiratory oscillometry is conducted through three acceptable measurements of tidal breathing and can be performed with minimal contraindications. Young children and patients who cannot perform spirometry due to cognitive or physical impairment can usually complete oscillometry. The main advantages of respiratory oscillometry are that it requires minimal patient cooperation and is more sensitive in detecting changes in small airways than conventional pulmonary function tests. Commercial devices are now available. Updated technical guidelines, standard operating protocols, and quality control/assurance guidelines have recently been published. Reference values are also available. 
We conducted oscillometry test audits before and after implementing a formal respiratory oscillometry training program and standard operating protocol. We observed improvement in the quality of tests completed, with a significant increase in the number of acceptable and reproducible measurements. 
The current paper outlines and demonstrates a standard operating protocol to conduct respiratory oscillometry in an outpatient setting. We highlight the key steps to ensuring acceptable and reproducible quality measurements according to the recommended European Respiratory Society (ERS) guidelines, as quality control is critical to measurement accuracies. Potential problems and pitfalls are also discussed with suggestions to resolve technical errors.

We demonstrate a standard operating protocol to conduct respiratory oscillometry, highlighting key quality control and assurance procedures.

Respiratory oscillometry is a different modality of pulmonary function testing that is increasingly used in a clinical and research setting to provide ...

Oxygenation-sensitive Cardiac MRI with Vasoactive Breathing Maneuvers for the Non-invasive Assessment of Coronary Microvascular Dysfunction

Oxygenation-sensitive cardiac magnetic resonance imaging (OS-CMR) is a diagnostic technique that uses the inherent paramagnetic properties of deoxyhemoglobin as an endogenous source of tissue contrast. Used in combination with standardized vasoactive breathing maneuvers (hyperventilation and apnea) as a potent non-pharmacologic vasomotor stimulus, OS-CMR can monitor changes in myocardial oxygenation. Quantifying such changes during the cardiac cycle and throughout vasoactive maneuvers can provide markers for coronary macro- and microvascular function and thereby circumvent the need for any extrinsic, intravenous contrast or pharmacologic stress agents.
OS-CMR uses the well-known sensitivity of T2*-weighted images to blood oxygenation. Oxygenation-sensitive images can be acquired on any cardiac MRI scanner using a modified standard clinical steady-state free precession (SSFP) cine sequence, making this technique vendor-agnostic and easily implemented. As a vasoactive breathing maneuver, we apply a 4-min breathing protocol of 120 s of free breathing, 60 s of paced hyperventilation, followed by an expiratory breath-hold of at least 30 s. The regional and global response of myocardial tissue oxygenation to this maneuver can be assessed by tracking the signal intensity change. The change over the initial 30 s of the post-hyperventilation breath-hold, referred to as the breathing-induced myocardial oxygenation reserve (B-MORE) has been studied in healthy people and various pathologies. A detailed protocol for performing oxygen-sensitive CMR scans with vasoactive maneuvers is provided.
As demonstrated in patients with microvascular dysfunction in yet incompletely understood conditions, such as inducible ischemia with no obstructive coronary artery stenosis (INOCA), heart failure with preserved ejection fraction (HFpEF), or microvascular dysfunction after heart transplantation, this approach provides unique, clinically important, and complementary information on coronary vascular function.

The assessment of microvascular function by oxygenation-sensitive cardiac magnetic resonance imaging in combination with vasoactive breathing maneuvers is unique in its ability to assess rapid dynamic changes in myocardial oxygenation in vivo and, thus, may serve as a critically important diagnostic technique for coronary vascular function.

Oxygenation-sensitive cardiac magnetic resonance imaging (OS-CMR) is a diagnostic technique that uses the inherent paramagnetic properties of ...

Physical Assessment of the Respiratory Tract II: Inspection

Physical assessment of the respiratory tract through inspection is a crucial step in understanding the patient&#39;s respiratory health. It provides insights into the functioning of the respiratory system, the musculoskeletal structure, and even the patient&#39;s nutritional status. This comprehensive approach involves observing several vital aspects: chest configuration, breathing patterns, respiratory rates, skin color, and use of accessory muscles.
Chest Configuration
The chest configuration can reveal a lot about the patient&#39;s respiratory health. Typically, the ratio of the anteroposterior diameter to the lateral diameter is 1:2. However, certain deformities associated with respiratory diseases can alter this relationship. These include the barrel chest, funnel chest (pectus excavatum), pigeon chest (pectus carinatum), and kyphoscoliosis.
Barrel chest, characterized by an increased anteroposterior diameter due to lung overinflation, is often seen in patients with emphysema and COPD. A funnel chest is a depression in the lower portion of the sternum that can compress the heart and great vessels, possibly leading to murmurs. The pigeon chest is an anterior sternum displacement, increasing the anteroposterior diameter. Kyphoscoliosis is defined by an elevated scapula and an S-shaped spine, limiting lung expansion.
When inspecting the posterior chest, any spinal curvatures such as kyphosis, scoliosis, and kyphoscoliosis should be noted, as they can affect breathing.
Breathing Patterns and Respiratory Rates
Breathing patterns and respiratory rates provide vital information about a patient&#39;s respiratory health. The average adult at rest takes 12 to 20 breaths per minute. In older adults, it is between 16 to 25 breaths/minute. The length of inspiration should be half as long as expiration (a ratio of 1:2). However, pathologic conditions may alter these patterns. For example, wheezing is common in patients with asthma, while irregular breathing patterns can indicate Kussmaul, Cheyne-Stokes, or Biot&#39;s respirations.
<ul>
	<li>&#8226; Kussmaul Respiration: Characterized by deep, rapid breathing, often seen in diabetic ketoacidosis or severe metabolic acidosis. It helps the body expel carbon dioxide to reduce acidosis.</li>
</ul>
<ul>
	<li>&#8226; Cheyne-Stokes Respiration: Involves a cycle of increasing and decreasing breathing depth, leading to temporary apnea, and can indicate heart failure, stroke, or brain injury.</li>
</ul>
<ul>
	<li>&#8226; Biot&#39;s Respiration: Marked by quick, shallow breaths followed by periods of apnea, often associated with medulla oblongata damage, stroke, or opioid use.</li>
</ul>
Skin Color
The color of the patient&#39;s skin can provide clues about their respiratory status. Cyanosis, a late sign of hypoxemia, is best observed in the conjunctivae, lips, palms, and under the tongue. It can be caused by hypoxemia or decreased cardiac output. Long-standing hypoxemia may lead to nail clubbing, which increases the angle between the base of the nail and its tip to 180 degrees or more.
Use of Accessory Muscles
During periods of exertion or specific disease conditions, accessory muscles like the sternocleidomastoid, scalene, and trapezius during inspiration, and the abdominal and internal intercostal muscles during expiration, can provide additional support to assist the breathing effort. Observing how the patient uses these muscles can provide important information about the patient&#39;s respiratory health.
In conclusion, physical assessment of the respiratory tract through inspection is a comprehensive approach that provides vital insights into a patient&#39;s respiratory health. By carefully observing the chest configuration, breathing patterns and rates, skin color, and use of accessory muscles, healthcare professionals can more effectively diagnose and treat respiratory diseases.

Inspection is the initial step in assessing the respiratory system. It involves observing the following components.
Initially, the chest configuration is ...

Medical-Surgical Nursing

An Overview of the Respiratory System: Anatomy, Physiology, Assessment, and Abnormalities

KEY TERMS AND CONCEPTS

Assessment of Ventilation II: Respiratory Depth and Rhythm

Respiratory Depth
Respiratory depth measures the volume of air inhaled or exhaled during a breath. It can vary from shallow to deep and typically remains consistent when a person is at rest or asleep. Occasionally, individuals will automatically inhale deeply, known as sighing, which inflates the lungs with more air than normal breathing.
To assess respiratory depth, observe the degree of chest excursion or movement:
<ul>
	<li>&#8226; Deep Respiration: Involves full lung expansion and complete exhalation, significantly increasing air intake.</li>
	<li>&#8226;&#160;Shallow Respiration: Characterized by minimal air passage through the lungs, making it less noticeable.</li>
</ul>
Specific clinical terms related to respiratory depth include:
<ul>
	<li>&#8226;&#160;Apnea: A cessation of breathing that, if sustained beyond 4 to 6 minutes, can lead to brain damage or death.</li>
	<li>&#8226;&#160;Dyspnea: Difficult or labored breathing, often rapid and shallow, where the patient may appear anxious. Dyspneic individuals usually find breathing easier when sitting upright, a condition known as orthopnea.</li>
</ul>
Respiratory Rhythm
Respiratory rhythm refers to the pattern of breathing, encompassing timing, regularity, and effort:
<ul>
	<li>&#8226;&#160;Diaphragmatic Breathing: Characterized by the contraction and relaxation of the diaphragm, this type of breathing is often seen in healthy men and children and is best observed by watching abdominal movements.</li>
	<li>&#8226;&#160;Thoracic Breathing: More common in women, this involves using thoracic muscles and is visible through movements in the upper chest.</li>
</ul>
Labored respirations may involve the use of accessory muscles in the neck. Signs of obstructed air movement, such as foreign body interference, include:
<ul>
	<li>&#8226;&#160;Retraction of Intercostal Spaces: Visible during inspiration when air movement is restricted.</li>
	<li>&#8226;&#160;Prolonged Exhalation is typical in conditions like COPD or asthma, where there is an obstruction to the outward flow of air.</li>
</ul>
Conclusion
Assessing the depth and rhythm of a patient&#39;s respiration is not just about identifying potential issues early. It&#39;s about tailoring interventions accordingly, ensuring that changes in respiratory patterns are promptly addressed. This thorough approach enhances patient care and outcomes and is a testament to your commitment to professional development and patient well-being.

Respiratory Depth
Respiratory depth measures the volume of air inhaled or exhaled during a breath. It can vary from shallow to deep and typically remains ...