Name: surfactant depletion combined with injurious ventilation results in a reproducible model of the acute respiratory distress syndrome (ards)
Uploaded: 2021-04-07T14:00:00
Description: Watch this Scientific Journal Video about Surfactant Depletion Combined with Injurious Ventilation Results in a Reproducible Model of the Acute Respiratory Distress Syndrome ARDS at JoVE.com

We gratefully acknowledge the excellent technical assistance of Birgit Brandt. This study was supported by a grant of the German Federal Ministry of Education and Research (FKZ 13GW0240A-D).

The experiments were conducted at the Department of Experimental Medicine, Charit&#233; - University Medicine, Berlin, Germany (certi&#64257;ed according to the EN DIN ISO 9001:2000) and were approved by the federal authorities for animal research in Berlin, Germany, prior to the experiments (G0229/18). The principles of laboratory animal care were used in all experiments and are in accordance with the guidelines of the European and German Society of Laboratory Animal Sciences.
1. Laboratory ani...

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This article describes the induction of experimental ARDS in pigs combining surfactant depletion by repeated lung lavages and ventilation with high tidal volumes, low PEEP, and complete inflation/deflation of the lungs. This combination causes a reproducible and comparable deterioration in gas exchange and the resulting hemodynamic compromise but limits the recruitability of the lungs. Thus, this model mimics clinical ARDS with low recruitability and allows the investigation of new ventilation regimes.
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The mortality of the acute respiratory distress syndrome (ARDS) remains high with values above 40%1 despite intensive research since its first description by Ashbough and Petty in 19672. Naturally, the investigation of novel therapeutic approaches is limited in the clinic due to ethical concerns and the lack of standardization of the underlying pathologies, ambient conditions, and co-medications, whereas animal models enable systematic research under standardized conditions.
Thus, experimental ARDS has been induced in either large animals (e.g., pigs) or small animals (e.g., rodents) using various methods such as pulmo-arterial infusion of oleic acid, intravenous (i.v.) infusion of bacteria and endotoxins, or cecal ligation and puncture (CLP) models causing sepsis-induced ARDS. In addition, direct lung injuries caused by burns and smoke inhalation or lung ischemia/reperfusion (I/R) are used3. One frequently used model of direct lung injury is surfactant depletion with lung lavages as first described by Lachmann et al. in guinea pigs4.
Surfactant depletion is a highly reproducible method that results rapidly in compromises in gas exchange and hemodynamics5. A major advantage is the possibility to apply surfactant depletion in large species which enable support research with clinically used mechanical ventilators, catheters, and monitors. However, a major disadvantage of the surfactant depletion model is the instant recruitment of atelectatic lung areas whenever high airway pressures or recruiting maneuvers, such as prone positioning, are applied. Thus, the model is not suitable to investigate, e.g., automated ventilation with high PEEP levels for prolonged times6. Yoshida et al. described a combination of surfactant depletion and ventilation with high inspiratory airway pressures to induce&#160;experimental ARDS7, but their model requires an elaborate maintenance of partial pressure of oxygen (PaO2) in a predefined corridor via repeated blood gas sampling and adjustment of the driving pressure according to a sliding table of inspiratory pressure and PEEP.
Overall, a model with an overly aggressive injurious ventilation or a laborious, repeated adjustment of the ventilation regime can result in structural damage of the lungs, which is too severe and results in subsequent multiple organ failure. Thus, this article provides a detailed description of an easily feasible model of surfactant depletion plus injurious ventilation with high Tv/low PEEP for induction of experimental ARDS, which supports research with clinically used ventilation parameters for prolonged periods.

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	<tbody>
		<tr>
			<td>Evita Infinity V500</td>
			<td>Dr&#228;ger</td>
			<td></td>
			<td>intensive care ventilator</td>
		</tr>
		<tr>
			<td>Flow through chamber thermistor</td>
			<td>Baxter</td>
			<td>93-505</td>
			<td>for measuring cardiac output</td>
		</tr>
		<tr>
			<td>Leader Cath Set</td>
			<td>Vygon</td>
			<td>1,15,805</td>
			<td>arterial catheter</td>
		</tr>
		<tr>
			<td>Mallinckrodt Tracheal Tube Cuffed</td>
			<td>Covidien</td>
			<td>107-80</td>
			<td>&#160;8.0 mm ID</td>
		</tr>
		<tr>
			<td>MultiCath3</td>
			<td>Vygon</td>
			<td>1,57,300</td>
			<td>3 lumen central venous catheter, 20 cm length</td>
		</tr>
		<tr>
			<td>Percutaneus Sheath Introducer Set</td>
			<td>Arrow</td>
			<td>SI-09600</td>
			<td>introducer sheath for pulmonary artery catheter of 4-6 Fr., 10 cm length</td>
		</tr>
		<tr>
			<td>Swan-Ganz True Size Thermodilution Catheter</td>
			<td>Edwards</td>
			<td>132F5</td>
			<td>pulmonary artery catheter, 75 cm length</td>
		</tr>
		<tr>
			<td>urinary catheter</td>
			<td></td>
			<td></td>
			<td>no specific model requiered</td>
		</tr>
		<tr>
			<td>Vasofix Braun&#252;le 20G</td>
			<td>B Braun</td>
			<td>4268113B</td>
			<td>peripheral vein catheter</td>
		</tr>
		<tr>
			<td>Vigilance I&#160;</td>
			<td>Edwards</td>
			<td></td>
			<td>monitor</td>
		</tr>
	</tbody>
</table>

surfactant depletion combined with injurious ventilation results in a reproducible model of the acute respiratory distress syndrome (ards)

Various animal models exist to study the complex pathomechanisms of the acute respiratory distress syndrome (ARDS). These models include pulmo-arterial infusion of oleic acid, infusion of endotoxins or bacteria, cecal ligation and puncture, various pneumonia models, lung ischemia/reperfusion models and, of course, surfactant depletion models, among others. Surfactant depletion produces a rapid, reproducible deterioration of pulmonary gas exchange and hemodynamics and can be induced in anesthetized pigs using repeated lung lavages with 0.9% saline (35 mL/kg body weight, 37 &#176;C). The surfactant depletion model supports investigations with standard respiratory and hemodynamic monitoring with clinically applied devices. But the model suffers from a relatively high recruitability and ventilation with high airway pressures can immediately reduce the severity of the injury by reopening atelectatic lung areas. Thus, this model is not suitable for investigations of ventilator regimes that use high airway pressures. A combination of surfactant depletion and injurious ventilation with high tidal volume/low positive end-expiratory pressure (high Tv/low PEEP) to cause ventilator induced lung injury (VILI) will reduce the recruitability of the resulting lung injury. The advantages of a timely induction and the possibility to perform experimental research in a setting comparable to an intensive care unit are preserved.

The PaO2/FIO2-ratio decreased during surfactant washout in all animals (Figure 3). The resulting hypoxemia, hypercapnia, and atelectasis caused an increase in pulmonary artery pressure. The details of the lung lavages are already described elsewhere6.
The surfactant depletion was repeated until the PaO2/FIO2 ratio remained below 100 mmHg despite mechanic...

Watch this Scientific Journal Video about Surfactant Depletion Combined with Injurious Ventilation Results in a Reproducible Model of the Acute Respiratory Distress Syndrome ARDS at JoVE.com

Surfactant Depletion Combined with Injurious Ventilation Results in a Reproducible Model of the Acute Respiratory Distress Syndrome ARDS

A combination of surfactant washout using 0.9% saline (35 mL/kg body weight, 37 &#176;C) and high tidal volume ventilation with low PEEP to cause moderate ventilator induced lung injury (VILI) results in experimental acute respiratory distress syndrome (ARDS). This method provides a model of lung injury with low/limited recruitability to study the effect of various ventilation strategies for extended periods.

Surfactant Depletion Combined with Injurious Ventilation Results in a Reproducible Model of the Acute Respiratory Distress Syndrome (ARDS)

Various animal models exist to study the complex pathomechanisms of the acute respiratory distress syndrome (ARDS). These models include pulmo-arterial ...

The combination of surfactant wash-out with injurious ventilation reduces the recruitability of the lung injury as compared to models with exclusive surfactant wash-out. The model is reproducible and does not require additional techniques. Furthermore, a two-hit model closely mimics the realistic clinical situation.The low recruitability of this model supports the experimental investigation of new ventilation strategies, paving the way for the translation of experimental lung research into clinical practice. To begin, set the mechanical ventilation parameters as described in the text manuscript, and target an end expiratory partial pressure of carbon dioxide of 35 to 40 millimeters of mercury and an oxygen saturation above 95%Use a continuous intravenous infusion of thiopentone and fentanyl to maintain the anesthesia, and administer a muscle relaxant if required. Cannulate the external jugular vein with a central venous catheter, and insert the introducer sheath of the pulmonary arterial catheter into the same vein.Then, cannulate the femoral artery for invasive blood pressure monitoring. Calibrate the transducers against the atmosphere, which is zero millimeters of mercury and 200 millimeters of mercury for the arterial line, and 50 millimeters of mercury for the central venous line, and start monitoring by connecting them to the arterial catheter and the central venous line. Connect the pulmonary artery catheter to the pressure transducer system and calibrate the transducer against the atmosphere and 100 millimeters of mercury.Then, introduce the pulmonary artery catheter through the introducer sheath with a deflated balloon for 10 to 15 centimeters, depending on the sheath length. Once the balloon has left the sheath, inflate it and advance the pulmonary artery catheter further while monitoring the pressure. Push the pulmonary artery catheter forward when the right atrium, the right ventricle, and the pulmonary artery pressure waves appear on the monitor, and stop when the pulmonary capillary wedge pressure wave is seen.Then, record the pulmonary capillary wedge pressure at end expiration and deflate the balloon. Calculate the pressure parameters described in the text manuscript, and record the required respiratory settings and measurements to complete the dataset. Ventilate the animal with a fraction of inspired oxygen of one, then disconnect the animal from the ventilator.Fill the lungs with pre-warmed saline using a funnel connected to the endotracheal tube. Stop if the mean arterial pressure decreases below 50 millimeters of mercury. Drain the lavage fluid by lowering the funnel to the ground level, and monitor the wave.Reconnect to the animal to the ventilator for oxygenation and wait until the animal recuperates, then repeat lavages until the Horowitz index decreases below 100 millimeters of mercury for at least five minutes at a fraction of inspired oxygen of one, and a positive end expiratory pressure above five millibar. Take an arterial blood gas sample after five minutes following each lavage. Keep the fraction of inspired oxygen at one, and set the ventilator on the volume-guaranteed, pressure-controlled ventilation mode.Increase the alarm threshold for peak inspiratory pressure to 60 millibar. Lower the respiratory rate, and set the inspiration-to-expiration ratio, then increase the tidal volume slowly up to 17 milliliters per kilogram body weight over at least two minutes. Do not increase the tidal volume further if an inspiratory pressure of 60 millibar is reached.Reduce the positive end expository pressure to two millibar and ventilate the animal for up to two hours. The Horowitz index decreased during the surfactant washout in all animals, but the recruitment maneuver resulted in a notable increase in oxygenation after the surfactant wash-out. The injurious ventilation of two hours diminished lung recruitability with respect to gas exchange and the mean pulmonary arterial pressure.The gas exchange parameters were improved with high tidal volumes due to the cyclic recruitment, while mean pulmonary arterial pressure was elevated due to high intrathoracic pressures and hypercapnia. Computer tomographic imaging of the lungs showed extensive atelectasis of the dependent areas of the lung during the ventilation, with a positive end expiratory pressure of six millibar, which resolved largely when the ventilation was escalated to a positive end expiratory pressure of 15 millibar. However, the substantial ubiquitous ground glass opacities did not resolve.The alveolar opacities observed with a positive end expiratory pressure of 15 millibar indicated structural damage of the lungs. They were also observed in the post-mortem examination of the lungs. When attempting this protocol, it is important to adjust the duration of injurious ventilation because structural lung damage cannot be recruited, and an animal might die prematurely if the injury is too extensive.The combination of surfactant depletion and injurious ventilation supports the investigation of therapies resulting in fast recruitment of atelectatic lung regions, such as ventilation modes with high ventilatory pressures.

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Pressure Controlled Ventilation to Induce Acute Lung Injury in Mice

Murine models are extensively used to investigate acute injuries of different organs systems (1-34). Acute lung injury (ALI), which occurs with prolonged mechanical ventilation, contributes to morbidity and mortality of critical illness, and studies on novel genetic or pharmacological targets are areas of intense investigation (1-3, 5, 8, 26, 30, 33-36). ALI is defined by the acute onset of the disease, which leads to non-cardiac pulmonary edema and subsequent impairment of pulmonary gas exchange (36). We have developed a murine model of ALI by using a pressure-controlled ventilation to induce ventilator-induced lung injury (2). For this purpose, C57BL/6 mice are anesthetized and a tracheotomy is performed followed by induction of ALI via mechanical ventilation. Mice are ventilated in a pressure-controlled setting with an inspiratory peak pressure of 45 mbar over 1 - 3 hours. As outcome parameters, pulmonary edema (wet-to-dry ratio), bronchoalveolar fluid albumin content, bronchoalveolar fluid and pulmonary tissue myeloperoxidase content and pulmonary gas exchange are assessed (2). Using this technique we could show that it sufficiently induces acute lung inflammation and can distinguish between different treatment groups or genotypes (1-3, 5). Therefore this technique may be helpful for researchers who pursue molecular mechanisms involved in ALI using a genetic approach in mice with gene-targeted deletion.

A murine model for ventilator induced lung injury is an important tool to study an acute lung injury in vivo. Here, we report an easy applicable in situ model for acute lung injury using high-pressure mechanical ventilation to induce acute failure of the lung.

Murine models are extensively used to investigate acute injuries of different organs systems (1-34). Acute lung injury (ALI), which occurs with prolonged ...

A Research Method For Detecting Transient Myocardial Ischemia In Patients With Suspected Acute Coronary Syndrome Using Continuous ST-segment Analysis

Each year, an estimated 785,000 Americans will have a new coronary attack, or acute coronary syndrome (ACS). The pathophysiology of ACS involves rupture of an atherosclerotic plaque; hence, treatment is aimed at plaque stabilization in order to prevent cellular death. However, there is considerable debate among clinicians, about which treatment pathway is best: early invasive using percutaneous coronary intervention (PCI/stent) when indicated or a conservative approach (i.e., medication only with PCI/stent if recurrent symptoms occur).
There are three types of ACS: ST elevation myocardial infarction (STEMI), non-ST elevation MI (NSTEMI), and unstable angina (UA). Among the three types, NSTEMI/UA is nearly four times as common as STEMI. Treatment decisions for NSTEMI/UA are based largely on symptoms and resting or exercise electrocardiograms (ECG). However, because of the dynamic and unpredictable nature of the atherosclerotic plaque, these methods often under detect myocardial ischemia because symptoms are unreliable, and/or continuous ECG monitoring was not utilized.
Continuous 12-lead ECG monitoring, which is both inexpensive and non-invasive, can identify transient episodes of myocardial ischemia, a precursor to MI, even when asymptomatic. However, continuous 12-lead ECG monitoring is not usual hospital practice; rather, only two leads are typically monitored. Information obtained with 12-lead ECG monitoring might provide useful information for deciding the best ACS treatment.
Purpose. Therefore, using 12-lead ECG monitoring, the COMPARE Study (electroCardiographic evaluatiOn of ischeMia comParing invAsive to phaRmacological trEatment) was designed to assess the frequency and clinical consequences of transient myocardial ischemia, in patients with NSTEMI/UA treated with either early invasive PCI/stent or those managed conservatively (medications or PCI/stent following recurrent symptoms). The purpose of this manuscript is to describe the methodology used in the COMPARE Study.
Method. Permission to proceed with this study was obtained from the Institutional Review Board of the hospital and the university. Research nurses identify hospitalized patients from the emergency department and telemetry unit with suspected ACS. Once consented, a 12-lead ECG Holter monitor is applied, and remains in place during the patient's entire hospital stay. Patients are also maintained on the routine bedside ECG monitoring system per hospital protocol. Off-line ECG analysis is done using sophisticated software and careful human oversight.

Continuous 12-lead electrocardiographic (ECG) monitoring can identify transient myocardial ischemia, even when asymptomatic, among patients with suspected acute coronary syndrome (ACS). In this article we describe our method for initiating patient monitoring using a Holter device, downloading the ECG data for off-line analysis, and how to utilize the ECG software to identify transient ischemia.

Each year, an estimated 785,000 Americans will have a new coronary attack, or acute coronary syndrome (ACS). The pathophysiology of ACS involves rupture ...

Lavage-induced Surfactant Depletion in Pigs As a Model of the Acute Respiratory Distress Syndrome (ARDS)

Various animal models of lung injury exist to study the complex pathomechanisms of human acute respiratory distress syndrome (ARDS) and evaluate future therapies. Severe lung injury with a reproducible deterioration of pulmonary gas exchange and hemodynamics can be induced in anesthetized pigs using repeated lung lavages with warmed 0.9% saline (50 ml/kg body weight). Including standard respiratory and hemodynamic monitoring with clinically applied devices in this model allows the evaluation of novel therapeutic strategies (drugs, modern ventilators, extracorporeal membrane oxygenators, ECMO), and bridges the gap between bench and bedside. Furthermore, induction of lung injury with lung lavages does not require the injection of pathogens/endotoxins that impact on measurements of pro- and anti-inflammatory cytokines. A disadvantage of the model is the high recruitability of atelectatic lung tissue. Standardization of the model helps to avoid pitfalls, to ensure comparability between experiments, and to reduce the number of animals needed.

Lavage-induced Surfactant Depletion in Pigs As a Model of the Acute Respiratory Distress Syndrome ARDS

Repeated pulmonary lavages in anesthetized pigs induce lung injury resembling major aspects of human acute respiratory distress syndrome (ARDS). For this purpose the lungs are repeatedly lavaged with 0.9% saline at 37 &#176;C. The goal of the protocol is a reproducible mitigation of gas exchange and hemodynamics for research in ARDS.

Various animal models of lung injury exist to study the complex pathomechanisms of human acute respiratory distress syndrome (ARDS) and evaluate future ...

Primary Outcome Assessment in a Pig Model of Acute Myocardial Infarction

Mortality after acute myocardial infarction remains substantial and is associated with significant morbidity, like heart failure. Novel therapeutics are therefore required to confine cardiac damage, promote survival and reduce the disease burden of heart failure. Large animal experiments are an essential part in the translational process from experimental to clinical therapies. To optimize clinical translation, robust and representative outcome measures are mandatory. The present manuscript aims to address this need by describing the assessment of three clinically relevant outcome modalities in a pig acute myocardial infarction (AMI) model: infarct size in relation to area at risk (IS/AAR) staining, 3-dimensional transesophageal echocardiography (TEE) and admittance-based pressure-volume (PV) loops. Infarct size is the main determinant driving the transition from AMI to heart failure and can be quantified by IS/AAR staining. Echocardiography is a reliable and robust tool in the assessment of global and regional cardiac function in clinical cardiology. Here, a method for three-dimensional transesophageal echocardiography (3D-TEE) in pigs is provided. Extensive insight into cardiac performance can be obtained by admittance-based pressure-volume (PV) loops, including intrinsic parameters of myocardial function that are pre- and afterload independent. Combined with a clinically feasible experimental study protocol, these outcome measures provide researchers with essential information to determine whether novel therapeutic strategies could yield promising targets for future testing in clinical studies.

Reliable and accurate outcome assessment is the key for translation of preclinical therapies into clinical treatment. The current paper describes how to assess three clinically relevant primary outcome parameters of cardiac performance and damage in a pig acute myocardial infarction model.

Mortality after acute myocardial infarction remains substantial and is associated with significant morbidity, like heart failure. Novel therapeutics are ...

Open Tracheostomy Gastric Acid Aspiration Murine Model of Acute Lung Injury Results in Maximal Acute Nonlethal Lung Injury

Acid pneumonitis is a major cause of sterile acute lung injury (ALI) in humans. Acid pneumonitis spans the clinical spectrum from asymptomatic to acute respiratory distress syndrome (ARDS), characterized by neutrophilic alveolitis, and injury to both alveolar epithelium and vascular endothelium. Clinically, ARDS is defined by acute onset of hypoxemia, bilateral patchy pulmonary infiltrates and non-cardiogenic pulmonary edema. Human studies have provided us with valuable information about the physiological and inflammatory changes in the lung caused by ARDS, which has led to various hypotheses about the underling mechanisms. Unfortunately, difficulties determining the etiology of ARDS, as well as a wide range of pathophysiology have resulted in a lack of critical information that could be useful in developing therapeutic strategies.
Translational animal models are valuable when their pathogenesis and pathophysiology accurately reproduce a concept proven in both in vitro and clinical settings. Although large animal models (e.g., sheep) share characteristics of the anatomy of human trachea-bronchial tree, murine models provide a host of other advantages including: low cost; short reproductive cycle lending itself to greater data acquisition; a well understood immunologic system; and a well characterized genome leading to the availability of a variety of gene deletion and transgenic strains. A robust model of low pH induced ARDS requires a murine ALI that targets mainly the alveolar epithelium, secondarily the vascular endothelium, as well as the small airways leading to the alveoli. Furthermore, a reproducible injury with wide differences between different injurious and non-injurious insults is important.
The murine gastric acid aspiration model presented here using hydrochloric acid employs an open tracheostomy and recreates a pathogenic scenario that reproduces the low pH pneumonitis injury in humans. Additionally, this model can be used to examine interaction of a low pH insult with other pulmonary injurious entities (e.g., food particles, pathogenic bacteria).

This protocol induces acute lung injury in a mouse that has close fidelity to the pathogenesis of acid pneumonitis observed in humans. We generate a maximal acute nonlethal low pH lung injury and account for differences in rodent-human anatomic respiratory structure using an open tracheostomy coupled with circumferential pressure release.

Acid pneumonitis is a major cause of sterile acute lung injury (ALI) in humans. Acid pneumonitis spans the clinical spectrum from asymptomatic to acute ...

Repeated Measurement of Respiratory Muscle Activity and Ventilation in Mouse Models of Neuromuscular Disease

Accessory respiratory muscles help to maintain ventilation when diaphragm function is impaired. The following protocol describes a method for repeated measurements over weeks or months of accessory respiratory muscle activity while simultaneously measuring ventilation in a non-anesthetized, freely behaving mouse. The technique includes the surgical implantation of a radio transmitter and the insertion of electrode leads into the scalene and trapezius muscles to measure the electromyogram activity of these inspiratory muscles. Ventilation is measured by whole-body plethysmography, and animal movement is assessed by video and is synchronized with electromyogram activity. Measurements of muscle activity and ventilation in a mouse model of amyotrophic lateral sclerosis are presented to show how this tool can be used to investigate how respiratory muscle activity changes over time and to assess the impact of muscle activity on ventilation. The described methods can easily be adapted to measure the activity of other muscles or to assess accessory respiratory muscle activity in additional mouse models of disease or injury.

This paper introduces a method for repeated measurements of ventilation and respiratory muscle activity in a freely behaving amyotrophic lateral sclerosis (ALS) mouse model throughout disease progression with whole-body plethysmography and electromyography via an implanted telemetry device.

Accessory respiratory muscles help to maintain ventilation when diaphragm function is impaired. The following protocol describes a method for repeated ...

A Component-resolved Diagnostic Approach for a Study on Grass Pollen Allergens in Chinese Southerners with Allergic Rhinitis and/or Asthma

Sensitization to grass pollen imposes a global risk for allergic airway diseases. Although prevention relies on local investigation of the pollen allergens, data on this topic are limited in southern China. Any available data were obtained by self-report questionnaires, skin prick tests, and total or specific IgE tests using crude extracts. For many reasons, these methods are unreliable. Serum sIgE reactivity to Bermuda grass, Timothy grass, and Humulus scandens allergens in a cohort of patients from Greater Guangzhou (southern China&#39;s largest city and its outskirts) with allergic rhinitis and/or asthma were examined using a fully-automated immunoassay analyzer as a component-resolved diagnostics (CRD) tool.
For the first time, a considerably high prevalence of Bermuda grass sIgE positivity was demonstrated in Chinese southerners with allergic rhinitis and/or asthma. In these patients, a subtle prevalence of sensitization to Timothy grass and Humulus scandens was also noted, which may arise from cross-reactivity, as the latter two are not common in the region. This was also supported by the detection of allergen components.
Fully-automated immunoassay analyzers may offer satisfactory consistency between regions, laboratories, and institutions and over time. The automaticity of the instrument may enable a standardized detection that would not have been readily revealed before the advent of CRD.
This is a study that uses a CRD approach to investigate sensitization to grass pollen allergens in southern China. It adds to current evidence in the literature. Future studies are needed to validate these findings. However, although CRD is a useful tool, the findings made with the fully-automated immunoassay analyzer should not substitute for other laboratory investigations, clinical evaluations, and physician expertise.

This work describes a protocol that uses a component-resolved approach to study sensitization to grass pollen allergens in a cohort of patients from southern China with allergic rhinitis and/or asthma.

Sensitization to grass pollen imposes a global risk for allergic airway diseases. Although prevention relies on local investigation of the pollen ...

Invasive Hemodynamic Monitoring of Aortic and Pulmonary Artery Hemodynamics in a Large Animal Model of ARDS

One of the leading causes of morbidity and mortality in patients with heart failure is right ventricular (RV) dysfunction, especially if it is due to pulmonary hypertension. For a better understanding and treatment of this disease, precise hemodynamic monitoring of left and right ventricular parameters is important. For this reason, it is essential to establish experimental pig models of cardiac hemodynamics and measurements for research purpose. 
This article shows the induction of ARDS by using oleic acid (OA) and consequent right ventricular dysfunction, as well as the instrumentation of the pigs and the data acquisition process that is needed to assess hemodynamic parameters. To achieve right ventricular dysfunction, we used oleic acid (OA) to cause ARDS and accompanied this with pulmonary artery hypertension (PAH). With this model of PAH and consecutive right ventricular dysfunction, many hemodynamic parameters can be measured, and right ventricular volume load can be detected. 
All vital parameters, including respiratory rate (RR), heart rate (HR) and body temperature were recorded throughout the whole experiment. Hemodynamic parameters including femoral artery pressure (FAP), aortic pressure (AP), right ventricular pressure (peak systolic, end systolic and end diastolic right ventricular pressure), central venous pressure (CVP), pulmonary artery pressure (PAP) and left arterial pressure (LAP) were measured as well as perfusion parameters including ascending aortic flow (AAF) and pulmonary artery flow (PAF). Hemodynamic measurements were performed using transcardiopulmonary thermodilution to provide cardiac output (CO). Furthermore, the PiCCO2 system (Pulse Contour Cardiac Output System 2) was used to receive parameters such as stroke volume variance (SVV), pulse pressure variance (PPV), as well as extravascular lung water (EVLW) and global end-diastolic volume (GEDV). Our monitoring procedure is suitable for detecting right ventricular dysfunction and monitoring hemodynamic findings before and after volume administration.

We present a protocol of creating right ventricular dysfunction in a pig model by inducing ARDS. We demonstrate invasive monitoring of left and right ventricular cardiac output using flow probes around the aorta and the pulmonary artery, as well as blood pressure measurements in the aorta and pulmonary artery.

One of the leading causes of morbidity and mortality in patients with heart failure is right ventricular (RV) dysfunction, especially if it is due to ...

Oleic Acid-Injection in Pigs As a Model for Acute Respiratory Distress Syndrome

The acute respiratory distress syndrome is a relevant intensive care disease with an incidence ranging between 2.2% and 19% of intensive care unit patients. Despite treatment advances over the last decades, ARDS patients still suffer mortality rates between 35 and 40%. There is still a need for further research to improve the outcome of patients suffering from ARDS. One problem is that no single animal model can mimic the complex pathomechanism of the acute respiratory distress syndrome, but several models exist to study different parts of it. Oleic acid injection (OAI)-induced lung injury is a well-established model for studying ventilation strategies, lung mechanics and ventilation/perfusion distribution in animals. OAI leads to severely impaired gas exchange, deterioration of lung mechanics and disruption of the alveolo-capillary barrier. The disadvantage of this model is the controversial mechanistic relevance of this model and the necessity for central venous access, which is challenging especially in smaller animal models. In summary, OAI-induced lung injury leads to reproducible results in small and large animals and hence represents a well-suited model for studying ARDS. Nevertheless, further research is necessary to find a model that mimics all parts of ARDS and lacks the problems associated with the different models existing today.

In this article, we present a protocol to induce acute lung injury in pigs by central-venous injection of oleic acid. This is an established animal model for studying the acute respiratory distress syndrome (ARDS).

The acute respiratory distress syndrome is a relevant intensive care disease with an incidence ranging between 2.2% and 19% of intensive care unit ...

The Left Pneumonectomy Combined with Monocrotaline or Sugen as a Model of Pulmonary Hypertension in Rats

In this protocol, we detail the correct procedural steps and necessary precautions to successfully perform a left pneumonectomy and induce PAH in rats with the additional administration of monocrotaline (MCT) or SU5416 (Sugen). We also compare these two models to other PAH models commonly used in research. In the last few years, the focus of animal PAH models has moved towards studying the mechanism of angioproliferation of plexiform lesions, in which the role of increased pulmonary blood flow is considered as an important trigger in the development of severe pulmonary vascular remodeling. One of the most promising rodent models of increased pulmonary flow is the unilateral left pneumonectomy combined with a "second hit" of MCT or Sugen. The removal of the left lung leads to increased and turbulent pulmonary blood flow and vascular remodeling. Currently, there is no detailed procedure of the pneumonectomy surgery in rats. This article details a step-by-step protocol of the pneumonectomy surgical procedure and post-operative care in male Sprague-Dawley rats. Briefly, the animal is anesthetized and the chest is opened. Once the left pulmonary artery, pulmonary vein, and bronchus are visualized, they are ligated and the left lung is removed. The chest then closed and the animal recovered. Blood is forced to circulate only on the right lung. This increased vascular pressure leads to a progressive remodeling and occlusion of small pulmonary arteries. The second hit of MCT or Sugen is used one week post-surgery to induce endothelial dysfunction. The combination of increased blood flow in the lung and endothelial dysfunction produces severe PAH. The primary limitation of this procedure is that it requires general surgical skills.

The rodent left pneumonectomy is a valuable technique in pulmonary hypertension research. Here, we present a protocol to describe the rat pneumonectomy procedure and postoperative care to ensure minimal morbidity and mortality.

In this protocol, we detail the correct procedural steps and necessary precautions to successfully perform a left pneumonectomy and induce PAH in rats ...