Name: combining volumetric capnography and barometric plethysmography to measure the lung structure-function relationship
Uploaded: 2019-01-08T13:00:00
Description: Watch this Scientific Journal Video about Combining Volumetric Capnography And Barometric Plethysmography To Measure The Lung Structure-function Relationship at JoVE.com

This work was funded by the Departments of Health and Human Physiology and Internal Medicine at the University of Iowa. This work was also supported by the Old Gold Fellowship (Bates) and Grant IRG-15-176-40 from the American Cancer Society, administered through The Holden Comprehensive Cancer Center at The University of Iowa (Bates)

This protocol has been previously approved by and follows the guidelines set by the University of Iowa Institutional Review Board. Data shown were collected as part of a project approved by the Institutional Review Board at the University of Iowa. Participants gave informed consent and the studies were performed in accordance with the Declaration of Helsinki.
1. Equipment
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	<li>Check the equipment table to verify that all required equipment is available. Double check the configuration us...

<ol>
	<li>Robinson, P. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Consensus+statement+for+inert+gas+washout+measurement+using+multiple-+and+single-+breath+tests.">Consensus statement for inert gas washout measurement using multiple- and single- breath tests.</a> European Respiratory Journal. 41 (3), 507-522 (2013).</li><li>Verbanck, S., Paiva, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gas+mixing+in+the+airways+and+airspaces.">Gas mixing in the airways and airspaces.</a> Comprehensive Physiology. 1 (2), 809-834 (2011).</li><li>Bates, M. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pulmonary+function+responses+to+ozone+in+smokers+with+a+limited+smoking+history.">Pulmonary function responses to ozone in smokers with a limited smoking history.</a> Toxicology and Applied Pharmacology. 278 (1), 85-90 (2014).</li><li>Bates, M. L., Brenza, T. M., Ben-Jebria, A., Bascom, R., Ultman, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Longitudinal+distribution+of+ozone+absorption+in+the+lung:+comparison+of+cigarette+smokers+and+nonsmokers.">Longitudinal distribution of ozone absorption in the lung: comparison of cigarette smokers and nonsmokers.</a> Toxicology and Applied Pharmacology. 236 (3), 270-275 (2009).</li><li>Reeser, W. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Uptake+of+ozone+in+human+lungs+and+its+relationship+to+local+physiological+response.">Uptake of ozone in human lungs and its relationship to local physiological response.</a> Inhalation Toxicology. 17 (13), 699-707 (2005).</li><li>Taylor, A. B., Lee, G. M., Nellore, K., Ben-Jebria, A., Ultman, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changes+in+the+carbon+dioxide+expirogram+in+response+to+ozone+exposure.">Changes in the carbon dioxide expirogram in response to ozone exposure.</a> Toxicology and Applied Pharmacology. 213 (1), 1-9 (2006).</li><li>Baker, L. G., Ultman, J. S., Rhoades, R. 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The Respiratory Dead Space.</a> American Journal of Physiology-Legacy Content. 154 (3), 405-416 (1948).</li><li>Eberlein, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supranormal+Expiratory+Airflow+after+Bilateral+Lung+Transplantation+Is+Associated+with+Improved+Survival.">Supranormal Expiratory Airflow after Bilateral Lung Transplantation Is Associated with Improved Survival.</a> American Journal of Respiratory and Critical Care Medicine. 183 (1), 79-87 (2011).</li><li>Eberlein, M., Schmidt, G. A., Brower, R. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chest+wall+strapping.+An+old+physiology+experiment+with+new+relevance+to+small+airways+diseases.">Chest wall strapping. An old physiology experiment with new relevance to small airways diseases.</a> Annals of the American Thoracic Society. 11 (8), 1258-1266 (2014).</li><li>Taher, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chest+wall+strapping+increases+expiratory+airflow+and+detectable+airway+segments+in+computer+tomographic+scans+of+normal+and+obstructed+lungs.">Chest wall strapping increases expiratory airflow and detectable airway segments in computer tomographic scans of normal and obstructed lungs.</a> Journal of Applied Physiology. , (2017).</li><li>Verscheure, S., Massion, P. B., Verschuren, F., Damas, P., Magder, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Volumetric+capnography:+lessons+from+the+past+and+current+clinical+applications.">Volumetric capnography: lessons from the past and current clinical applications.</a> Critical Care. 20 (1), 184 (2016).</li><li>Suarez-Sipmann, F., Bohm, S. H., Tusman, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Volumetric+capnography:+the+time+has+come.">Volumetric capnography: the time has come.</a> Current Opinion in Critical Care. 20 (3), 333-339 (2014).</li><li>Wanger, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Standardisation+of+the+measurement+of+lung+volumes.">Standardisation of the measurement of lung volumes.</a> European Respiratory Journal. 26 (3), 511-522 (2005).</li><li>Culver, B. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recommendations+for+a+Standardized+Pulmonary+Function+Report.+An+Official+American+Thoracic+Society+Technical+Statement.">Recommendations for a Standardized Pulmonary Function Report. An Official American Thoracic Society Technical Statement.</a> American Journal of Respiratory and Critical Care Medicine. 196 (11), 1463-1472 (2017).</li><li>Goldman, H. I., Becklake, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Respiratory+function+tests;+normal+values+at+median+altitudes+and+the+prediction+of+normal+results.">Respiratory function tests; normal values at median altitudes and the prediction of normal results.</a> Am Rev Tuberc. 79 (4), 457-467 (1959).</li><li>Shim, S. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lumen+area+change+(Delta+Lumen)+between+inspiratory+and+expiratory+multidetector+computed+tomography+as+a+measure+of+severe+outcomes+in+asthmatic+patients.">Lumen area change (Delta Lumen) between inspiratory and expiratory multidetector computed tomography as a measure of severe outcomes in asthmatic patients.</a> J The Journal of Allergy and Clinical. , (2018).</li><li>Smith, B. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+airway+branch+variation+and+chronic+obstructive+pulmonary+disease.">Human airway branch variation and chronic obstructive pulmonary disease.</a> Proceedings of the National Academy of Sciences of the United States of America. 115 (5), E974-E981 (2018).</li><li>Farmery, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Volumetric+Capnography+and+Lung+Growth+in+Children+-+a+Simple-Model+Validated.">Volumetric Capnography and Lung Growth in Children - a Simple-Model Validated.</a> Anesthesiology. 83 (6), 1377-1379 (1995).</li><li>Scherer, P. W., Neufeld, G. R., Aukburg, S. J., Hess, G. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+Effective+Peripheral+Bronchial+Cross-Section+from+Single-Breath+Gas+Washout.">Measurement of Effective Peripheral Bronchial Cross-Section from Single-Breath Gas Washout.</a> Journal of Biomechanical Engineering-Transactions of the Asme. 105 (3), 290-293 (1983).</li><li>Sinha, P., Soni, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+volumetric+capnography+and+mixed+expired+gas+methods+to+calculate+physiological+dead+space+in+mechanically+ventilated+ICU+patients.">Comparison of volumetric capnography and mixed expired gas methods to calculate physiological dead space in mechanically ventilated ICU patients.</a> Intensive Care Medicine. 38 (10), 1712-1717 (2012).</li><li>Bourgoin, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+Bohr+and+Enghoff+Dead+Space+Equations+in+Mechanically+Ventilated+Children.">Assessment of Bohr and Enghoff Dead Space Equations in Mechanically Ventilated Children.</a> Respiratory Care. 62 (4), 468-474 (2017).</li></ol>

Here, a protocol for the measurement of VD and airways homogeneity (slope) is provided. These measurements can be made at FRC, or as a function of lung volume. Measuring FRC before the start of the experiment and after a perturbation allows VD and slope to be plotted as a function of lung volume and may provide useful information about the structure-function relationship of the lung that is not obtained from capnography at FRC alone.
Airways volume and high-resolution str...

Gas washout techniques have been used for decades to provide important information about the structure and uniformity of the airway tree. The lung is classically described as having two compartments &#8211; a conducting zone that is comprised of the anatomic dead space and the respiratory zone where gas exchange occurs in the alveoli. The conducting airways are termed as &#8220;dead space&#8221; because they do not participate in the exchange of oxygen and carbon dioxide. In the single breath gas washout method, the concentration profile of an exhaled gas can be used to determine the volume of the anatomic dead space and to derive information about the uniformity of ventilation. Some methods rely on the breathing of inert gases to make these measures (N2, argon, He, SF6, etc.). The use of inert gas is well-established, supported by scientific consensus statements1, and there are available commercial equipment with user friendly interfaces. However, the exhaled profile of carbon dioxide (CO2) can be used to derive similar information. Evaluating the profile of CO2 as a function of the exhaled volume, or volumetric capnography, does not require the participant to breathe special gas mixtures and allows the investigator to gather additional information flexibly about metabolism and gas exchange with minimal adjustment to the technique.
During a controlled exhalation, the concentration of CO2 can be plotted against the total exhaled volume. At the beginning of an exhalation, the dead space is filled with atmospheric gas. This is reflected in Phase I of the exhaled CO2 profile where there is an undetectable amount of CO2 (Figure 1, top). Phase II marks the transition to the alveolar gas, where gas exchange occurs and CO2 is abundant. The volume at the midpoint of Phase II is the volume of the anatomic dead space (VD). Phase III contains alveolar gas. Because airways with different diameters empty at different rates, the slope (S) of Phase III provides information about airways uniformity. A steeper slope of Phase III suggests a less uniform airway tree proximal to the terminal bronchioles, or convection-dependent inhomogeneity2. In the case where a perturbation may change the rate of CO2 production, and to make comparisons between individuals, the slope can be divided by the area under the curve to normalize for differences in metabolism (NS or normalized slope). Volumetric capnography has been used previously to evaluate the changes in airways volume and uniformity following air pollutant exposure3,4,5,6.
Gas transport in the lung is governed by both convection and diffusion. Single breath washout measures are highly dependent on air flow and the measured value of VD occurs at the convection-diffusion boundary. Changing the flow rate of the exhalation or preceding inhalation changes the location of that boundary7. Capnography is also highly dependent on the volume of the lung immediately preceding the maneuver. Larger lung volumes distend the airways, resulting in larger values of VD8. One solution is to consistently make the measurement at the same lung volume &#8211; usually functional residual capacity (FRC). An alternative, described here, is to couple volumetric capnography with barometric plethysmography, in order to obtain the relationship between VD and lung volume. The participant then performs the maneuver at constant flow rates, while varying the lung volume. This still allows for classic capnographic measures to be made at FRC, but also for the relationship between the lung volume and dead space volume and between the lung volume and homogeneity to be derived. Indeed, the added value of coupling capnography with plethysmography comes from the ability to test hypotheses about the distensibility of the airways tree and the structure-function relationship of the lung. This may be a valuable tool for investigators aiming to quantify the influence of airways mechanics versus lung compliance and elastance on pulmonary function in healthy and diseased populations9,10,11. Furthermore, accounting for the absolute lung volume at which the volumetric capnographic measurements are being performed allows investigators to characterize the effects of conditions that can alter the inflation state of the lung, such as obesity, lung transplant, or interventions like chest wall strapping. Volumetric capnography may ultimately have clinical utility in the intensive care setting12,13.

<table>
	<tbody>
		<tr>
			<td>Computer with dual monitor</td>
			<td>Dell Instruments</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PowerLab 8/35*</td>
			<td>AD Instruments</td>
			<td>PL3508</td>
			<td></td>
		</tr>
		<tr>
			<td>LabChart Data Acquisition Software*</td>
			<td>AD Instruments</td>
			<td>Version 8</td>
			<td></td>
		</tr>
		<tr>
			<td>Gemini Respiratory Gas Analyzer* (upgraded option)</td>
			<td>CWE, Inc</td>
			<td>GEMINI 14-10000</td>
			<td>*indicates that part is available in the Exercise Physiology package from AD Instruments</td>
		</tr>
		<tr>
			<td>Heated Pneumotach with Heater Controller* (upgraded option)</td>
			<td>Hans Rudolph, Inc</td>
			<td>MLT3813H-V</td>
			<td></td>
		</tr>
		<tr>
			<td>3L Calibration Syringe</td>
			<td>Vitalograph</td>
			<td>36020</td>
			<td></td>
		</tr>
		<tr>
			<td>Nose Clip*</td>
			<td>VacuMed</td>
			<td>Snuffer 1008</td>
			<td></td>
		</tr>
		<tr>
			<td>Pulse Transducer*</td>
			<td>AD Instruments</td>
			<td>TN1012/ST</td>
			<td></td>
		</tr>
		<tr>
			<td>Barometer</td>
			<td>Fischer Scientific</td>
			<td>15-078-198</td>
			<td></td>
		</tr>
		<tr>
			<td>Flanged Mouthpiece*</td>
			<td>AD Instruments</td>
			<td>MLA1026</td>
			<td></td>
		</tr>
		<tr>
			<td>Nafion drying tube with three-way stopcock*</td>
			<td>AD Instruments</td>
			<td>MLA0343</td>
			<td></td>
		</tr>
		<tr>
			<td>Desiccant cartridge (optional for humid environments)*</td>
			<td>AD Instruments</td>
			<td>MLA6024</td>
			<td></td>
		</tr>
		<tr>
			<td>Resistor</td>
			<td>Hans Rudolph, Inc</td>
			<td>7100 R5</td>
			<td></td>
		</tr>
		<tr>
			<td>Flow head adapters*</td>
			<td>AD Instruments</td>
			<td>MLA1081</td>
			<td></td>
		</tr>
		<tr>
			<td>Modified Tubing Adapter (optional)</td>
			<td>AD Instruments</td>
			<td>SP0145</td>
			<td></td>
		</tr>
		<tr>
			<td>Two way non-rebreather valve (optional)*</td>
			<td>AD Instruments</td>
			<td>SP0146</td>
			<td></td>
		</tr>
		<tr>
			<td>Plethysmograph</td>
			<td>Vyaire</td>
			<td>V62J</td>
			<td></td>
		</tr>
		<tr>
			<td>High Purity Helium Gas</td>
			<td>Praxair</td>
			<td>He 4.8</td>
			<td></td>
		</tr>
		<tr>
			<td>6% CO2 and 16% O2 Calibration Gas</td>
			<td>Praxair</td>
			<td>Custom</td>
			<td></td>
		</tr>
		<tr>
			<td>Microsoft Excel</td>
			<td>Microsoft</td>
			<td>Office 365</td>
			<td></td>
		</tr>
	</tbody>
</table>

combining volumetric capnography and barometric plethysmography to measure the lung structure-function relationship

Tools to measure lung and airways volume are critical for pulmonary researchers interested in evaluating the impact of disease or novel therapies on the lung. Barometric plethysmography is a classic technique to evaluate the lung volume with a long history of clinical use. Volumetric capnography utilizes the profile of exhaled carbon dioxide to determine the volume of the conducting airways, or dead space, and provides an index of airways homogeneity. These techniques may be used independently, or in combination to evaluate the dependence of airways volume and homogeneity on lung volume. This paper provides detailed technical instructions to replicate these techniques and our representative data demonstrates that the airways volume and homogeneity are highly correlated to lung volume. We also provide a macro for the analysis of capnographic data, which can be modified or adapted to fit different experimental designs. The advantage of these measures is that their advantages and limitations are supported by decades of experimental data, and they can be made repeatedly in the same subject without expensive imaging equipment or technically advanced analysis algorithms. These methods may be particularly useful for investigators interested in perturbations that change both the functional residual capacity of the lung and airways volume.

Representative plethysmography results are given in Figure 4. This participant required four attempts in order to collect three FRC values with &#60;5% variability from the mean.%Ref reflects the percent of the predicted value for each variable based on population regression equations that take into account sex, age, race, height and weight
Figure 1 (top) shows a repres...

Watch this Scientific Journal Video about Combining Volumetric Capnography And Barometric Plethysmography To Measure The Lung Structure-function Relationship at JoVE.com

Combining Volumetric Capnography And Barometric Plethysmography To Measure The Lung Structure-function Relationship

Here, we describe two measures of pulmonary function &#8211; barometric plethysmography, which allows the measurement of lung volume, and volumetric capnography, a tool to measure the anatomic dead space and airways uniformity. These techniques may be used independently or combined to assess airways function at different lung volumes.

Tools to measure lung and airways volume are critical for pulmonary researchers interested in evaluating the impact of disease or novel therapies on the ...

This method can help answer key questions in pulmonary physiology, particularly about how the structure-function relationship in the lung contributes to disease pathology. The main advantage of this technique is that it allows measures to be made repeatedly, within the same subject, without expensive imaging equipment or technically advanced analysis algorithms. The implications of measuring the lung structure-function relationship extend toward understanding the development of lung diseases, using classic, well-established physiological tools to evaluate novel interventions.Though this method provides insights into human lung physiology, it can also be applied to animal models of lung disease. Generally, individuals new to this method may struggle with the correct coaching of participants to follow the outlined maneuvers. Several practice runs are often necessary with a first-time participant.Visual demonstration of this method is critical, as the capnographic maneuver can be difficult to learn and the flow and volume of the maneuver must be controlled carefully. Procedures involving human subjects has been approved by the Institutional Review Board of the University of Iowa. Before beginning the calibration, use a standard barometer to measure the temperature, barometric pressure, and relative humidity, and enter these values into the plethysmograph software as correction factors.To calibrate the flow sensor, use a calibrated three liter syringe at variable flow rates and use a 50 milliliter pump to calibrate the box pressure. Immediately prior to the plethysmography measurement, have the participant enter the whole-body plethysmograph and close the door. After 30 to 60 seconds of thermal equilibration, instruct the participant to place their mouth on the mouthpiece, put on the nose clips, and place their hands on their cheeks.Instruct the participant to breathe normally, allowing at least four tidal breaths to be acquired, and a functional residual capacity to be established. At the end of a normal exhalation, close the shutter and coach the participant to pant lightly at 0.5 to one breaths per second for three to four seconds. Evaluate the relationship between the mouth pressure and plethysmograph pressure to ensure that it is a series of overlapping, straight lines, without thermal drift, and open the shutter and allow the participant to take a normal breath.Then coach the participant to exhale to the residual volume. Followed by a maximal inspiratory maneuver to total lung capacity. Before the participant arrives, address and modify the variables in the table, as necessary.To calibrate the gas analyzer, attach the drying tube to the mixing chamber and flush the bag with inert gas at a rate of at least 10 liters per minute, taking care not the pressurize the system. Once the displayed concentrations of the displaced carbon dioxide and oxygen have stabilized, adjust the zero knobs until they both read zero. Next, repeat the flush with 6%carbon dioxide and room air containing 20.93%oxygen as the calibration gases, matching the concentration of the calibration gases with the span knob when the concentration of the gases stabilizes.Then, recheck the inert gas and calibration gas concentrations and adjust the zero and span knobs until both are accurate to plus or minus 0.1%To calibrate the heated pneumotach, allow the pneumotach to warm to 37 degrees Celsius for at least 20 minutes, and open the Flow Channel menu in the system software. Select Spirometer and click Zero to zero the pneumotach. Then select OK.Use a flow head adaptor to connect a three liter syringe to the pneumotach and highlight the calibration breath.Under the Flow Channel menu, select Spirometer Flow, and Calibrate, and enter three liters. Click OK.And use the syringe the inject three liters of room air into the pneumotach at varying flow rates. The difference from three liters should be less than 5%When the system is ready, coach the participant to perform a single maneuver consisting of two pairs of breaths:a coaching breath and a breath for analysis.Because we have inspiration and expiration, with inspiration. During the maneuver, coach the participant to follow the flow guide on the computer monitor. Consider adding a resistor in line with the mouthpiece to make the exhaled flow easier to control.To measure the functional residual capacity, instruct the participant to sit straight with both feet on the floor, put on nose clips, and place their mouth on the mouthpiece. Coach the participant to complete at least one minute of tidal breathing to measure the metabolic function and to allow the participant to become familiar with the mouthpiece. Stop the data collection after one minute.Before beginning the maneuver, participants should vary their tidal volume, taking either normal, smaller, or larger than normal tidal breaths, to ensure that capnograms are obtained at different lung volumes. Coach the participant to transition to performing a capnogram maneuver as soon as the flow tracings appear on the screen, and resume the data collection at a random point in the participant's respiratory cycle, to allow measurements to be obtained at different lung volumes. Finally, coach to perform a sigh at the end of each maneuver, so that the muscles of respiration are completely relaxed, to allow the functional respiratory capacity to be determined.The single most important step, is the correct measurement and completion of the maneuver performed with volumetric capnography. Then, stop the data collection and have the participant repeat the capnogram maneuvers at least six to eight more times, to obtain 12 to 16 pairs of breaths for analysis. Here, a representative single capnogram used in an analysis, and the raw data for the entire sequence of the maneuver, are shown.In the raw data, the capnogram and the flow tracing were not aligned to account for the time delay. In these representative cases, the dead space and the slope were significantly correlated to the lung volume, suggesting that the dead space and airway homogeneity increase as the lung volume increases. While attempting this procedure, it's important to remember that it is highly dependent on the participant's exhaled flow rate and the delay between the analyzer and the spirometer.The accuracy of these vales should be checked carefully. After its development, this technique paved the way for researchers in the field of pulmonology to explore the structure-volume relationship of the lung in various patient populations, and this could potentially be integrated into the standard bedside care of respiratory diseases.

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Ischemia-reperfusion (IR) was surgically performed in murine hearts which were then subjected to repeated imaging to monitor temporal changes in ...

Bronchial Thermoplasty:  A Novel Therapeutic Approach to Severe Asthma

Bronchial thermoplasty is a non-drug procedure for severe persistent asthma that delivers thermal energy to the airway wall in a precisely controlled manner to reduce excessive airway smooth muscle. Reducing airway smooth muscle decreases the ability of the airways to constrict, thereby reducing the frequency of asthma attacks. Bronchial thermoplasty is delivered by the Alair System and is performed in three outpatient procedure visits, each scheduled approximately three weeks apart. The first procedure treats the airways of the right lower lobe, the second treats the airways of the left lower lobe and the third and final procedure treats the airways in both upper lobes. After all three procedures are performed the bronchial thermoplasty treatment is complete.
Bronchial thermoplasty is performed during bronchoscopy with the patient under moderate sedation. All accessible airways distal to the mainstem bronchi between 3 and 10 mm in diameter, with the exception of the right middle lobe, are treated under bronchoscopic visualization. Contiguous and non-overlapping activations of the device are used, moving from distal to proximal along the length of the airway, and systematically from airway to airway as described previously. Although conceptually straightforward, the actual execution of bronchial thermoplasty is quite intricate and procedural duration for the treatment of a single lobe is often substantially longer than encountered during routine bronchoscopy. As such, bronchial thermoplasty should be considered a complex interventional bronchoscopy and is intended for the experienced bronchoscopist. Optimal patient management is critical in any such complex and longer duration bronchoscopic procedure. This article discusses the importance of careful patient selection, patient preparation, patient management, procedure duration, postoperative care and follow-up to ensure that bronchial thermoplasty is performed safely.
Bronchial thermoplasty is expected to complement asthma maintenance medications by providing long-lasting asthma control and improving asthma-related quality of life of patients with severe asthma. In addition, bronchial thermoplasty has been demonstrated to reduce severe exacerbations (asthma attacks) emergency rooms visits for respiratory symptoms, and time lost from work, school and other daily activities due to asthma.

Bronchial thermoplasty is a non-drug procedure for severe persistent asthma that delivers thermal energy to the airway wall in a precisely controlled manner to reduce excessive airway smooth muscle. Reducing airway smooth muscle decreases the ability of the airways to constrict, thereby reducing the frequency of asthma attacks.

Bronchial thermoplasty is a non-drug procedure for severe persistent asthma that delivers thermal energy to the airway wall in a precisely controlled ...

Cardiac Catheterization in Mice to Measure the Pressure Volume Relationship: Investigating the Bowditch Effect

Animal models that mimic human cardiac disorders have been created to test potential therapeutic strategies. A key component to evaluating these strategies is to examine their effects on heart function. There are several techniques to measure in vivo cardiac mechanics (e.g., echocardiography, pressure/volume relations, etc.). Compared to echocardiography, real-time left ventricular (LV) pressure/volume analysis via catheterization is more precise and insightful in assessing LV function. Additionally, LV pressure/volume analysis provides the ability to instantaneously record changes during manipulations of contractility (e.g., &#946;-adrenergic stimulation) and pathological insults (e.g., ischemia/reperfusion injury). In addition to the maximum (+dP/dt) and minimum (-dP/dt) rate of pressure change in the LV, an accurate assessment of LV function via several load-independent indexes (e.g., end systolic pressure volume relationship and preload recruitable stroke work) can be attained. Heart rate has a significant effect on LV contractility such that an increase in the heart rate is the primary mechanism to increase cardiac output (i.e., Bowditch effect). Thus, when comparing hemodynamics between experimental groups, it is necessary to have similar heart rates. Furthermore, a hallmark of many cardiomyopathy models is a decrease in contractile reserve (i.e., decreased Bowditch effect). Consequently, vital information can be obtained by determining the effects of increasing heart rate on contractility. Our and others data has demonstrated that the neuronal nitric oxide synthase (NOS1) knockout mouse has decreased contractility. Here we describe the procedure of measuring LV pressure/volume with increasing heart rates using the NOS1 knockout mouse model.

This article describes the measurement of murine left ventricular function via pressure/volume analysis at different heart rates.

Animal models that mimic human cardiac disorders have been created to test potential therapeutic strategies. A key component to evaluating these ...

Evaluation of Capnography Sampling Line Compatibility and Accuracy when Used with a Portable Capnography Monitor

Capnography is commonly used to monitor patient&#8217;s ventilatory status. While sidestream capnography has been shown to provide a reliable assessment of end-tidal CO2 (ETCO2), its accuracy is commonly validated using commercial kits composed of a capnography monitor and its matching disposable nasal cannula sampling lines. The purpose of this study was to assess the compatibility and accuracy of cross-paired capnography sampling lines with a single portable bedside capnography monitor. A series of 4 bench tests were performed to evaluate the tensile strength, rise time, ETCO2 accuracy as a function of respiratory rate, and ETCO2 accuracy in the presence of supplemental O2. Each bench test was performed using specialized, validated equipment to allow for a full evaluation of sampling line performance. The 4 bench tests successfully differentiated between sampling lines from different commercial sources and suggested that due to increased rise time and decreased ETCO2 accuracy, not all nasal cannula sampling lines provide reliable clinical data when cross-paired with a commercial capnography monitor. Care should be taken to ensure that any cross-pairing of capnography monitors and disposable sampling lines is fully validated for use across respiratory rates and supplemental O2 flow rates commonly encountered in clinical settings.

The goal of this study was to evaluate the accuracy of capnography sampling lines used in conjunction with a portable bedside capnography monitor. Sampling lines from 7 manufacturers were evaluated for tensile strength, rise time, and ETCO2 accuracy as a function of respiratory rate or supplemental oxygen flow rate.

Capnography is commonly used to monitor patient&#8217;s ventilatory status. While sidestream capnography has been shown to provide a reliable assessment ...

A Rat Lung Transplantation Model of Warm Ischemia/Reperfusion Injury: Optimizations to Improve Outcomes

From our experience with rat lung transplantation, we have found several areas for improvement. Information in the existing literature regarding methods for choosing appropriate cuff sizes for the pulmonary vein (PV), pulmonary artery (PA), or bronchus (Br) are varied, thus making the determination of proper cuff size during rat lung transplantation an exercise of trial and error. By standardizing the cuffing technique to use the smallest effective cuff appropriate for the size of the vessel or bronchus, one can make the transplantation procedure safer, faster, and more successful. Since diameters of the PV, PA, and Br are related to the body weight of the rat, we present a strategy to choosing an appropriate size using a weight-based guide. Since lung volume is also related to body weight, we recommend that this relationship should also be considered when choosing the proper volume of air for donor lung inflation during warm ischemia as well as for the proper volume of PBS to be instilled during bronchoalveolar lavage (BAL) fluid collection. We also describe methods for 4th intercostal space dissection, wound closure, and sample collection from both the native and transplanted lobes.

Here, we present optimizations to a rat lung transplantation model that serve to improve outcomes. We provide a size guide for cuffs based on body weight, a measurement strategy to ascertain the 4th intercostal space, and methods of wound closure and BAL (bronchoalveolar lavage) fluid and tissue collection.

From our experience with rat lung transplantation, we have found several areas for improvement. Information in the existing literature regarding methods ...

Echocardiographic Characterization of Left Ventricular Structure, Function, and Coronary Flow in Neonate Mice

Echocardiography is a non-invasive procedure that enables the evaluation of structural and functional parameters in animal models of cardiovascular disease and is used to assess the impact of potential treatments in preclinical studies. Echocardiographic studies are usually conducted in young adult mice (i.e., 4-6 weeks of age). The evaluation of early neonatal cardiovascular function is not usually performed because of the small size of the mouse pups and the associated technical difficulties. One of the most important challenges is that the short length of the pups&#39; limbs prevents them from reaching the electrodes in the echocardiography platform. Body temperature is the other challenge, as pups are very susceptible to changes in temperature. Therefore, it is important to establish a practical guide for performing echocardiographic studies in small mouse pups to help researchers detect early pathological changes and study the progression of cardiovascular disease over time. The current work describes a protocol for performing echocardiography in mouse pups at the early age of 7 days old. The echocardiographic characterization of cardiac morphology, function, and coronary flow in neonatal mice is also described.

The present protocol describes the echocardiographic assessment of left ventricular morphology, function, and coronary blood flow in 7-day old neonate mice.

Echocardiography is a non-invasive procedure that enables the evaluation of structural and functional parameters in animal models of cardiovascular ...

Combining 3D-Printing and Electrospinning to Manufacture Biomimetic Heart Valve Leaflets

Electrospinning has become a widely used technique in cardiovascular tissue engineering as it offers the possibility to create (micro-)fibrous scaffolds with adjustable properties. The aim of this study was to create multilayered scaffolds mimicking the architectural fiber characteristics of human heart valve leaflets using conductive 3D-printed collectors.
Models of aortic valve cusps were created using commercial computer-aided design (CAD) software. Conductive polylactic acid was used to fabricate 3D-printed leaflet templates. These cusp negatives were integrated into a specifically designed, rotating electrospinning mandrel. Three layers of polyurethane were spun onto the collector, mimicking the fiber orientation of human heart valves. Surface and fiber structure was assessed with a scanning electron microscope (SEM). The application of fluorescent dye additionally permitted the microscopic visualization of the multilayered fiber structure. Tensile testing was performed to assess the biomechanical properties of the scaffolds.
3D-printing of essential parts for the electrospinning rig was possible in a short time for a low budget. The aortic valve cusps created following this protocol were three-layered, with a fiber diameter of 4.1 &#177; 1.6 &#181;m. SEM imaging revealed an even distribution of fibers. Fluorescence microscopy revealed individual layers with differently aligned fibers, with each layer precisely reaching the desired fiber configuration. The produced scaffolds showed high tensile strength, especially along the direction of alignment. The printing files for the different collectors are available as Supplemental File 1, Supplemental File 2, Supplemental File 3, Supplemental File 4, and Supplemental File 5.
With a highly specialized setup and workflow protocol, it is possible to mimic tissues with complex fiber structures over multiple layers. Spinning directly on 3D-printed collectors creates considerable flexibility in manufacturing 3D shapes at low production costs.

The presented method offers an innovative way for engineering biomimetic fiber structures in three-dimensional (3D) scaffolds (e.g., heart valve leaflets). 3D-printed, conductive geometries were used to determine shape and dimensions. Fiber orientation and characteristics were individually adjustable for each layer. Multiple samples could be manufactured in one setup.

Electrospinning has become a widely used technique in cardiovascular tissue engineering as it offers the possibility to create (micro-)fibrous scaffolds ...

Network Pharmacology Prediction and Experimental Validation of Trichosanthes-Fritillaria thunbergii Action Mechanism Against Lung Adenocarcinoma

We aimed to study the mechanism of Trichosanthes-Fritillaria thunbergii in treating lung adenocarcinoma (LUAD) based on network pharmacology and experimental verification. The effective components and potential targets of Trichosanthis and Fritillaria thunbergii were collected by high-throughput experiment and reference-guided (HERB) database of traditional Chinese medicine and a similarity ensemble approach (SEA) database, and the LUAD-related targets were queried by the GeneCards and Online Mendelian Inheritance in Man (OMIM) databases. A drug-component-disease-target network was constructed by Cytoscape software. Protein-protein interaction (PPI) network, gene ontology (GO) function, and Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analyses were conducted to obtain core targets and key pathways. An aqueous extract of Trichosanthes-Fritillaria thunbergii and A549 cells were used for the subsequent experimental validation. Through the HERB database and literature search, 31 effective compounds and 157 potential target genes of Trichosanthes-Fritillaria thunbergii were screened, of which 144 were regulatory targets of Trichosanthes-Fritillaria thunbergii in the treatment of lung adenocarcinoma. The GO functional enrichment analysis showed that the mechanism of action of Trichosanthes-Fritillaria thunbergii against lung adenocarcinoma is mainly protein phosphorylation. The KEGG pathway enrichment analysis suggested that the treatment of lung adenocarcinoma by Trichosanthes-Fritillaria thunbergii mainly involves the PI3K/AKT signaling pathway. The experimental validation showed that an aqueous extract of Trichosanthes-Fritillaria thunbergii could inhibit the proliferation of A549 cells and the phosphorylation of AKT. Through network pharmacology and experimental validation, it was verified that the PI3K/AKT signaling pathway plays a vital role in the action of Trichosanthes-Fritillaria thunbergii in treating lung adenocarcinoma.

Network Pharmacology Prediction and Experimental Validation of Trichosanthes-Fritillaria thunbergii Action Mechanism Against Lung Adenocarcinoma

This study reveals the mechanism of Trichosanthes-Fritillaria thunbergii in treating lung adenocarcinoma based on network pharmacology and experimental verification. The study also demonstrates that the PI3K/AKT signaling pathway plays a vital role in the action of Trichosanthes-Fritillaria thunbergii in treating lung adenocarcinoma.

We aimed to study the mechanism of Trichosanthes-Fritillaria thunbergii in treating lung adenocarcinoma (LUAD) based on network pharmacology and ...

Assessing Lung Function with Hyperpolarized Xenon-129 MRI

Quantitative Measure of Lung Structure and Function Obtained from Hyperpolarized Xenon Spectroscopy

Hyperpolarized Xenon-129 (HXe) magnetic resonance imaging (MRI) provides tools for obtaining 2- or 3-dimensional maps of lung ventilation patterns, gas diffusion, Xenon uptake by lung parenchyma, and other lung function metrics. However, by trading spatial for temporal resolution, it also enables tracing of pulmonary Xenon gas exchange on a ms timescale. This article describes one such technique, chemical shift saturation recovery (CSSR) MR spectroscopy. It illustrates how it can be used to assess capillary blood volume, septal wall thickness, and the surface-to-volume ratio in the alveoli. The flip angle of the applied radiofrequency pulses (RF) was carefully calibrated. Single-dose breath-hold and multi-dose free-breathing protocols were employed for administering the gas to the subject. Once the inhaled Xenon gas reached the alveoli, a series of 90&#176; RF pulses was applied to ensure maximum saturation of the accumulated Xenon magnetization in the lung parenchyma. Following a variable delay time, spectra were acquired to quantify the regrowth of the Xenon signal due to gas exchange between the alveolar gas volume and the tissue compartments of the lung. These spectra were then analyzed by fitting complex pseudo-Voigt functions to the three dominant peaks. Finally, the delay time-dependent peak amplitudes were fitted to a one-dimensional analytical gas-exchange model to extract physiological parameters.

Author Spotlight: Advancing Lung Disease Research with Free-Breathing Hyperpolarized Xenon-129 MRI

The manuscript presents a detailed protocol for using hyperpolarized Xenon-129 chemical shift saturation recovery (CSSR) to trace pulmonary gas exchange, assess the apparent alveolar septal wall thickness, and measure the surface-to-volume ratio. The method has the potential to diagnose and monitor lung diseases.

Hyperpolarized Xenon-129 (HXe) magnetic resonance imaging (MRI) provides tools for obtaining 2- or 3-dimensional maps of lung ventilation patterns, gas ...

Investigating HFpEF Pathophysiology in a Hyperlipidemia&amp;#45;Induced Mouse Model

A Murine Model of Hyperlipidemia&#45;Induced Heart Failure with Preserved Ejection Fraction

The pathophysiology of heart failure with preserved ejection fraction (HFpEF) driven by lipotoxicity is incompletely understood. Given the urgent need for animal models that accurately mimic cardio-metabolic HFpEF, a hyperlipidemia-induced murine model was developed by reverse engineering phenotypes seen in HFpEF patients. This model aimed to investigate HFpEF, focusing on the interplay between lipotoxicity and metabolic syndrome. Hyperlipidemia was induced in wild-type (WT) mice on a 129J strain background through bi-weekly intraperitoneal injections of poloxamer-407 (P-407), a block co-polymer that blocks lipoprotein lipase, combined with a single intravenous injection of adeno-associated virus 9-cardiac troponin T-low-density lipoprotein receptor (AAV9-cTnT-LDLR). Extensive assessments were conducted between 4 and 8 weeks post-treatment, including echocardiography, blood pressure recording, whole-body plethysmography, echocardiography (ECG) telemetry, activity wheel monitoring (AWM), and biochemical and histological analyses. The LDLR/P-407 mice exhibited distinctive features at four weeks, including diastolic dysfunction, preserved ejection fraction, and increased left ventricular wall thickness. Notably, blood pressure and renal function remained within normal ranges. Additionally, ECG and AWM revealed heart blocks and reduced activity, respectively. Diastolic function deteriorated at eight weeks, accompanied by a significant decline in respiratory rates. Further investigation into the double treatment model revealed elevated fibrosis, wet/dry lung ratios, and heart weight/body weight ratios. The LDLR/P-407 mice exhibited xanthelasmas, ascites, and cardiac ischemia. Interestingly, sudden deaths occurred between 6 and 12 weeks post-treatment. The murine HFpEF model offers a valuable and promising experimental resource for elucidating the intricacies of metabolic syndrome contributing to diastolic dysfunction within the context of lipotoxicity-mediated HFpEF.

Author Spotlight: Exploring the Relationship Between Lipotoxicity and HFpEF 

This protocol presents a detailed approach to replicating a murine model of hyperlipidemia-induced heart failure with preserved ejection fraction (HFpEF). The design combines the administration of adeno-associated virus 9-cardiac troponin T-low-density lipoprotein receptor (AAV9-cTnT-LDLR) and poloxamer-407 (P-407).

The pathophysiology of heart failure with preserved ejection fraction (HFpEF) driven by lipotoxicity is incompletely understood. Given the urgent need for ...