The authors would like to thank Dr. Jos&#233; A. Diaz, Jamie Adcock, Mary Susan Fultz and the S.R. Light Laboratory at Vanderbilt University Medical Center for their assistance and support. This work was supported by a grant from the National Heart, Lung, and Blood Institute of the National Institutes of Health (BA; R01HL148244). The content is the sole responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

The protocol received approval from the Vanderbilt University Institutional Animal Care and Use Committee (protocol M1800176-00) and strictly adhered to the National Institute of Health Guidelines for the Care and Use of Laboratory Animals. Male and female Yorkshire pigs, weighing approximately 40-45 kg, were utilized in this experiment. The animals were obtained from a commercial source (see Table of Materials). The current practice does not involve screening for any pre-existing medical conditions in the acquired swine. While it is acknowledged that this practice could potentially interfere with or mask intended results, it is considered unlikely according to the vendor, and this limitation is accepted.
1. Animal preparation
<ol>
	<li>Anesthesia and ventilation
	<ol>
		<li>Anesthetize the pig with intramuscular injection of ketamine (2.2 mg/kg) / xylazine (2.2 mg/kg) / telazol (4.4 mg/kg) and position the animal in a supine (lying down) posture on the operating table.</li>
		<li>Maintain general anesthesia by initiating inhalational anesthetic, 1% isoflurane.</li>
		<li>Expose the vocal cords through the mouth using a laryngoscope and intubate12 with a 6.5 mm endotracheal tube (see Table of Materials). Inflate the tube cuff with 3-5 mL of air using a syringe without a needle attached. 
		NOTE: Immediately perform carbon dioxide (CO2) capnography post-tracheal cannulation to ensure proper tube placement, and measure CO2 with ventilation indicating appropriate ventilation.</li>
		<li>Use an 18 G to 24 G intravenous (IV) catheter placed in the central or marginal ear vein on the posterior side of the auricle to administer intraoperative (as needed) and euthanasia drugs to the pig.&#160; Secure the IV catheter with 1-inch adhesive tape.</li>
		<li>Set mechanical ventilation to volume-controlled ventilation settings with a tidal volume of 8 mL/kg. 
		NOTE: Anesthesia monitoring is conducted throughout the experiment. Vital signs, response to stimulus, presence/absence of movement, jaw tone laxity, changes in heart rate, end-tidal CO2, and respiratory rate variation are monitored by an independent animal lab technician. Adjustments to the inhaled anesthetic dose are made based on these assessments. Analgesic administration of buprenorphine via bolus is performed. Adjust the respiratory rate on the mechanical ventilator to maintain an end-tidal CO2 of 35-40 mmHg throughout the experiment.</li>
	</ol>
	</li>
	<li>Cannulation and monitoring
	<ol>
		<li>Disinfect the entire anterior neck with a 2% chlorhexidine scrub solution, followed by a spray of 5% providone-iodine solution.</li>
		<li>Surgically expose both the right and left internal and external jugular (IJ and EJ) veins and&#160;carotid arteries (CA) with a vertical incision, approximately 7-8 cm, immediately lateral to the trachea on either side using a No. 23 blade to the sternum13. 
		NOTE: A surgical cut-down approach is chosen for vascular access due to the challenges of a percutaneous, ultrasound-guided Seldinger technique14 in swine. The tough skin and vascular size make a cut-down approach more feasible. Cervical vessels are preferred for bilateral pulmonary artery catheters (PAC), though femoral access is an option. The choice which jugular vein (IJ or EJ) is at the discretion of procedurelist. Which ever has the larger diameter can be cannulated and used for heart catheterization.</li>
		<li>Dissect the strap muscles and tract as needed using Kelly tissue scissors and Lahey retractors13 (see Table of Materials).</li>
		<li>After exposure, place two 8.5 Fr&#160;cannulas and two PACs using the Seldinger technique14. 
		NOTE: Right jugular vein&#160;catheter and PAC are dedicated for volume administration and hemodynamic monitoring. Left jugular vein&#160;catheter and corresponding PAC are used for oleic acid administration. Dual-PAC placement is confirmed using fluoroscopy.</li>
		<li>Using the Seldinger technique, place an arterial line in the right CA for invasive blood pressure monitoring throughout the experiment.</li>
		<li>Attach all desired monitoring equipments. Monitor heart rate (HR) with telemetry leads. Monitor systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) by connecting a pressure transducer to the CA catheter. Monitor mean pulmonary artery pressure (MPAP) and central venous pressure (CVP) using an independent pressure transducer/amplifier system set-up. 
		&#8203;NOTE: Calculate pulse pressure as the difference between SBP and DBP, and pulse pressure variability (PPV) by calculating the difference between peak pulse pressure at inspiration and expiration during the respiratory cycle. Perform thermodilution cardiac output (CO) using device-specific volume temperature/volume calibration. To obtain a pulmonary capillary wedge pressure (PCWP), inflate the PAC balloon with 1.5 mL of air, advance the catheter until visualization of both &#34;v&#34; and &#34;a&#34; waves, representing restricted right-to-left blood flow, and record the PCWP as the pressure value of the &#34;a&#34; wave at end expiration16.</li>
		<li>To monitor urine output, place a Foley catheter (see Table of Materials) in the pig&#39;s urethra. For male pigs, surgical suprapubic catheterization is required17.</li>
		<li>Administer crystalloids (PlasmaLyte, see Table of Materials) at a rate of 100 mL over 10 min to achieve a PCWP of 8-12 mmHg (euvolemia) before initiating oleic acid. Check PCWP every 100 mL until 10 mmHg is achieved.</li>
	</ol>
	</li>
</ol>
2. Oleic acid infusion
<ol>
	<li>Oleic acid preparation
	<ol>
		<li>Prepare the oleic acid solution (16%) by combining 16 mL of oleic acid with 84 mL of normal saline. 
		NOTE: Handle oleic acid with care, ensuring personnel wear protective gloves, safety goggles, and masks to prevent direct skin contact, inhalation, or eye exposure. Frequent agitation is necessary to prevent separation, and dimethyl sulfoxide may be added if separation occurs.</li>
		<li>Prime the oleic acid solution into an IV fluid line and connect it to the distal port of the left&#160;jugular pulmonary artery catheter (see Table of Materials).</li>
	</ol>
	</li>
	<li>Oleic acid initiation
	<ol>
		<li>Start the oleic acid infusion at a rate of 0.2 mL/kg/h, marking the official start time18,19,20(Figure 1). 
		NOTE: Confirm hemodynamic monitoring and catheter placement before starting the oleic acid infusion. Techniques such as fluoroscopy or transthoracic echocardiography can ensure proper placement21,22.</li>
		<li>Immediately after starting oleic acid, set ventilator settings to mimic room air conditions (FiO2 = 21%, PEEP = 0 cm H2O).</li>
	</ol>
	</li>
	<li>Hemodynamic and respiratory monitoring during oleic acid infusion
	<ol>
		<li>Continuously monitor heart rate (HR), fraction of oxygen-saturated hemoglobin (SpO2), respiratory rate (RR), end-tidal carbon dioxide (ETCO2), central venous pressure (CVP), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), pulse pressure variability (PPV), and mean pulmonary artery pressure (MPAP).
		<ol>
			<li>Measure partial arterial oxygen pressure (PaO2), pH, lactate, base excess, cardiac output (CO), and pulmonary capillary wedge pressure (PCWP) every 30 min over the first 60-90 min and then every 15 min thereafter until sacrifice (Figure 1). Record peak airway pressure and plateau pressure at the same time PaO2 is measured. 
			NOTE: Typical starting values for continuously monitored variables are 95%-100%, 15-20 breaths per minute, 25-35 mmHg, 70-80 mmHg, 40-50 mmHg, 55-65 mmHg, 1%-4%, and 10-20 mmHg, respectively. Starting values for intermittent variables are 10 mmHg, 7.4, 0-2 mg/dL, -2 +2 mEq/L, &#62;5 L/min, and 8-10 mmHg, respectively.</li>
		</ol>
		</li>
		<li>Consider the experiment complete once arterial PaO2/fraction of inspired O2 (P/F) is less than &#60;10023. 
		&#8203;NOTE: At this point, animal can be euthanized (see below), and pulmonary pathology samples can be obtained, if needed (Figure 2).</li>
	</ol>
	</li>
</ol>
3. Venous waveform analysis and ventilator management procedure
<ol>
	<li>Respiratory non-Invasive Venous waveform Analysis 
	&#160;- Respiratory Index (RIVA-RI) 
	NOTE: Our research team employs this model to investigate changes in venous waveforms during respiratory distress. Peripheral venous waveforms are noninvasively captured at the upper arm of a pig using a piezoelectric sensor (see Table of Materials). Signal processing and amplification are required for analysis of these low-amplitude waveforms. Fourier transformation is then applied to present the data in the frequency domain, revealing a low-amplitude waveform at approximately 0.2 Hz (termed &#34;fR0&#34;) corresponding to respiration. This hypothesis suggests that this wave results from retrograde propagation of negative intrathoracic pressure during inspiration from the right atrium/vena cava throughout the venous system. The weighted contributions of the amplitudes of the respiratory signal (fR0) can be ratiometrically normalized to compare data on a common scale and improve performance, and to the amplitude of the frequency of the pulse rate (f0) to produce a RIVA-RI7.
	<ol>
		<li>Place the piezoelectrode on the anterior upper extremity venous plexus immediately proximal to the elbow. 
		NOTE: Ensure recording and uploading abilities with the piezoelectrode device. Examples of previous recording prototypes can be found in referenced literature7,24,25,26,27.</li>
		<li>Start recording venous waveforms with LabChart software (see Table of Materials) whenever venous waveforms are desired during experimentation.</li>
	</ol>
	</li>
	<li>Euthanasia
	<ol>
		<li>Confirm the maintenance of isoflurane at 1%.</li>
		<li>Induce cardiac arrest by IV injection of sodium pentobarbital (125 mg/kg) (following institutionally approved protocols).</li>
		<li>Confirm the lack of vitals post-injection to verify demise.</li>
	</ol>
	</li>
</ol>

Oleic Acid&#45;Induced Acute Respiratory Decompensation in Pigs

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A provisional patent on intellectual property associated with respiratory non-invasive venous waveform analysis has been filed by the authors (BA, CB, and KH).

The key element in this protocol is to closely monitor the hemodynamic condition of the pig during the administration of oleic acid to induce respiratory distress15. It is of the utmost importance for researchers to take the necessary time to appropriately position the hemodynamic monitoring devices. One specific drawback of this model is the potential hemodynamic instability that may arise as a result of inflammation and injury to the respiratory vasculature8,<s...

The utilization of porcine models in translational research holds significant importance in advancing our understanding of human medicine1. Porcine models, due to their physiological and anatomical similarities to humans, provide a valuable platform for studying complex diseases and therapeutic interventions1. In the context of acute respiratory failure, porcine models offer a unique opportunity to investigate the pathophysiological mechanisms, evaluate treatment strategies, and assess potential interventions1,2,3. The ability to replicate key aspects of human respiratory physiology and responses to various stimuli in porcine models allows for a comprehensive evaluation of therapeutic modalities before progressing to human trials1,2,3. This research paradigm enables researchers to bridge the gap between preclinical investigations and clinical application, facilitating the development of novel therapies and improving patient outcomes1. Therefore, the establishment of an efficient, effective, and reproducible acute respiratory failure porcine model serves as a crucial tool in advancing the knowledge of respiratory diseases and guiding the development of effective interventions in human medicine1.
Respiratory distress, a critical medical condition, has witnessed limited advancements in its diagnosis and management over the past three decades4. The currently employed evaluation and triage metrics, which include subjective symptoms, physical examination findings, SpO2, and respiratory rate, often exhibit limitations in detecting acute pulmonary conditions at an early stage5,6,7. This inadequacy not only hampers efficient triage and resource allocation but also fails to provide effective, quantitative monitoring of disease progression and treatment response in patients with chronic pulmonary diseases. The emerging landscape of chronic respiratory conditions, such as long COVID, along with the burden of acute respiratory insufficiencies on hospital resources, underscores the urgent need to expand translational research and foster innovation in respiratory disease management.
The direct infusion of oleic acid into a pig&#39;s bloodstream has been recognized as a robust method to induce acute respiratory distress8. Oleic acid, a monounsaturated fatty acid, has demonstrated the ability to trigger significant pulmonary injury and compromise respiratory function when introduced into the pulmonary circulation8. Upon infusion, oleic acid provokes vasoconstriction, resulting in increased pulmonary arterial pressure and resistance, leading to impaired gas exchange and oxygenation9. Furthermore, oleic acid promotes the activation of inflammatory pathways, including the release of pro-inflammatory mediators and recruitment of immune cells, which contribute to the development of lung injury and respiratory distress10. All of this results in severe hypoxemia, increases in pulmonary arterial pressures, and the accumulation of extravascular lung water11. Histological evaluation of the lung parenchyma has demonstrated injury that is indistinguishable from human acute respiratory distress9.
This article details a method involving the direct administration of oleic acid into the pulmonary artery to induce acute respiratory distress, avoiding untreatable, severe hemodynamic compromise. The described method is anticipated to be a valuable tool for future researchers exploring the underlying pathophysiological mechanisms of acute respiratory failure and assessing potential therapeutic interventions and innovations.

<table><tbody><tr><td>1% Isoflurane</td><td>Primal, Boston, MA, USA</td><td>26675-46-7</td><td>https://www.sigmaaldrich.com/US/en/product/aldrich/792632?gclid=Cj0KCQjw9fqnBhDSARIsAHl&lt;br/&gt; cQYS_W-q6tS2s6LQw2Qn7Roa3T&lt;br/&gt; GIpTLPf52351vrhgp44foEcRozPqt&lt;br/&gt; YaAtvfEALw_wcB</td></tr><tr><td>Arterial Catheter</td><td>Merit Medical, South Jordan, UT, USA</td><td>MAK401</td><td>MAK Mini Access Kit 4F</td></tr><tr><td>Blood Pressure Amp</td><td>AD Instruments, Colorado Springs, CO, USA</td><td>FE117</td><td>https://www.adinstruments.com/products/bp-blood-pressure-amp</td></tr><tr><td>Central Venous Catheter</td><td>Arrow International, Cleveland, OH, USA</td><td>AK-09800</td><td>8.5 Fr. x 4&quot; (10 cm) Arrow-Flex</td></tr><tr><td>Disposable Pressure Transducers</td><td>AD Instruments, Colorado Springs, CO, USA</td><td>MLT0670</td><td>https://www.adinstruments.com/products/disposable-bp-transducers</td></tr><tr><td>Edwards Lifesciences Triple Stage Venous Cannulas</td><td>Edwards Life Sciences, Irvine, CA</td><td>TF293702</td><td>https://www.graylinemedical.com/products/edwards-lifesciences-triple-stage-venous-cannulas-venous-dual-stage-cannula-tf293702?variant=31851942576185&amp;amp;gad=1&amp;amp;&lt;br/&gt; gclid=Cj0KCQiAr8eqBhD3ARIsAIe&lt;br/&gt; -buNdmkzavUBaIx-1be7boWn2kW&lt;br/&gt; hbUR6QCjaobB08uuK9qJW66JvY&lt;br/&gt; TM4aAufGEALw_wcB</td></tr><tr><td>Kelly Scissors</td><td>MPM Medical Supply, Freehold, NJ 07728</td><td>104-5516</td><td>https://www.mpmmedicalsupply.com/products/kelly-scissors</td></tr><tr><td>Kendall 930 FoamElectrodes</td><td>Covidien, Mansfield, MA, USA</td><td>22935</td><td>https://www.cardinalhealth.com/en/product-solutions/medical/patient-monitoring/electrocardiography/monitoring-ecg-electrodes/radiolucent-electrodes/kendall-930-series-radiolucent-foam-electrodes.html</td></tr><tr><td>Ketamine Hydrochloride 100 mg/mL, Injectable Solution, 10 mL</td><td>Patterson Veterinary, Loveland, CO 80538</td><td>07-894-8462</td><td>https://www.pattersonvet.com/ProductItem/078948462?omni=ketamine</td></tr><tr><td>LabChart 8 software</td><td>AD Instruments, Colorado Springs, CO, USA</td><td>N/A</td><td>https://www.adinstruments.com/products/labchart</td></tr><tr><td>Lahey Retractor</td><td>BOSS Instruments LTD, Gordonsville, VA 22942</td><td>18-1210</td><td>https://bossinstruments.com/product/7-3-4-lahey-thyroid-retractor-6mmx28mm/</td></tr><tr><td>Oleic Acid</td><td>Sigma-Aldrich, Merck, Darmstadt, Germany</td><td>O1008</td><td>https://www.sigmaaldrich.com/US/en/product/sial/o1008?gclid=CjwKCAjwzJmlBhBBEiwAEJy&lt;br/&gt; Lu2047wRpXqF_Z2BegUyhgZJ&lt;br/&gt; _WygsWfErhgrGCIyMp8PxwNH&lt;br/&gt; sTZ8qARoCl1QQAvD_BwE&amp;amp;gcl&lt;br/&gt; src=aw.ds</td></tr><tr><td>Peripheral IV Catheter Angiocath 18-24 G 1.16 inch</td><td>McKesson, Irving, TX, USA</td><td>329830</td><td>https://mms.mckesson.com/product/329830/Becton-Dickinson-381144</td></tr><tr><td>Piezoelectrode</td><td>MuRata Manuractoring Co, Ltd., Nagaokakyo, Kyoto, Japan</td><td>7BB-12-9</td><td>https://www.murata.com/en-us/products/productdetail?partno=7BB-12-9</td></tr><tr><td>PlasmaLyte</td><td>Baxter International, Deerfield, IL, USA</td><td>2B2544X</td><td>https://www.ciamedical.com/baxter-2b2544x-each-solution-plasma-lyte-a-inj-ph-7-4-1000ml</td></tr><tr><td>Pulmonary Artery Catheter</td><td>Edwards Life Sciences, Irvine, CA</td><td>131F7</td><td>Swan Ganz 7F x 110cm&amp;nbsp;</td></tr><tr><td>Standard Endotracheal Tubes</td><td>Teleflex, Morrisville, NC 27560</td><td>5-10313</td><td>https://www.teleflex.com/usa/en/product-areas/anesthesia/airway-management/endotracheal-tubes/standard-tubes/index.html</td></tr><tr><td>SurgiVet Clearview Foley Catheter, 8 Fr, 55 cm Silicone</td><td>Penn Veterinary Supply, Inc, West Rendering, PN 13971</td><td>SVCFC1030</td><td>https://www.pennvet.com/customer/portal/catalog/home?urile=wcm:path%3APennVet+Catalog/Super+Sku+Catalog/SS0672/Surgivet+Clearview+Silicone+Foley+Catheters</td></tr><tr><td>Telazol (Tiletamine HCl and Zolazepam HCl), Injectable Solution, 5 mL</td><td>Patterson Veterinary, Loveland, CO 80538</td><td>07-801-4969</td><td>https://www.pattersonvet.com/ProductItem/078014969?omni=telazol</td></tr><tr><td>Welch Allyn E-MacIntosh Standard Laryngoscope Blade</td><td>MFIMedical, San Diego, CA 92131</td><td>WLA-69242</td><td>https://mfimedical.com/products/welch-allyn-e-macintosh-standard-laryngoscope-blade?variant=12965771870285&amp;amp;currency&lt;br/&gt; =USD&amp;amp;utm_medium=product_sync&lt;br/&gt; &amp;amp;utm_source=google&amp;amp;utm_content&lt;br/&gt; =sag_organic&amp;amp;utm_campaign=sag&lt;br/&gt; _organic&amp;amp;gclid=Cj0KCQiAr8eqBhD&lt;br/&gt; 3ARIsAIe-buMhpgM96qRXkCUKA&lt;br/&gt; 6Mhmdat0p93JbecCGTaLStexhV&lt;br/&gt; pkUVa9VkWUzgaAr-iEALw_wcB</td></tr><tr><td>Xylazine HCl 100 mg/mL, Injectable Solution, 50 mL</td><td>Patterson Veterinary, Loveland, CO 80538</td><td>07-894-5244</td><td>https://www.pattersonvet.com/ProductItem/078945244</td></tr><tr><td>Yorkshire Pigs</td><td>Oak Hill Genetics, Ewing, IL, USA</td><td>138274</td><td>Female/Male Swine- Yorkshire/Landrace 81-100lbs</td></tr></tbody></table>

a porcine model of acute respiratory failure with a continuous infusion of oleic acid

This protocol outlines an acute respiratory distress model utilizing centrally administered oleic acid infusion in Yorkshire pigs. Prior to experimentation, each pig underwent general anesthesia, endotracheal intubation, and mechanical ventilation, and was equipped with bilateral&#160;jugular vein central vascular access catheters. Oleic acid was administered through a dedicated pulmonary artery catheter at a rate of 0.2 mL/kg/h. The infusion lasted for 60-120 min, inducing respiratory distress. Throughout the experiment, various parameters including heart rate, respiratory rate, arterial blood pressure, central venous pressure, pulmonary artery pressure, pulmonary capillary wedge pressure, end-tidal carbon dioxide, peak airway pressures, and plateau pressures were monitored. Around the 60 min mark, decreases in partial arterial oxygen pressure (PaO2) and fraction of oxygen-saturated hemoglobin (SpO2) were observed. Periodic hemodynamic instability, accompanied by acute increases in pulmonary artery pressures, occurred during the infusion. Post-infusion, histological analysis of the lung parenchyma revealed changes indicative of parenchymal damage and acute disease processes, confirming the effectiveness of the model in simulating acute respiratory decompensation.

Early single pig, pilot data demonstrates an increase in RIVA-RI prior to changes in other respiratory monitoring measures (RR and SpO2), in line with changes in PaO2 (Figure 3). The drop in PaO2 is the &#34;positive&#34; result this model intends to achieve. Preliminary data also shows that RIVA-RI increases and the PaO2 decreases with disease progression starting at the 30-min&#160;mark (Figure 3; red arrow). PaO<sub...

Watch this Scientific Journal Video about Author Spotlight: Exploring Venous Waveforms for Non-Invasive Respiratory Monitoring in Pigs at JoVE.com

Author Spotlight: Exploring Venous Waveforms for Non&#45;Invasive Respiratory Monitoring in Pigs

Infusing oleic acid continuously into the pulmonary artery of an anesthetized adult pig induces acute respiratory failure, enabling controlled experimentation during acute respiratory decompensation.

A Porcine Model of Acute Respiratory Failure with a Continuous Infusion of Oleic Acid

This protocol outlines an acute respiratory distress model utilizing centrally administered oleic acid infusion in Yorkshire pigs. Prior to ...

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370 Views.  Vanderbilt University Medical Center. Infusing oleic acid continuously into the pulmonary artery of an anesthetized adult pig induces acute respiratory failure, enabling controlled experimentation during acute respiratory decompensation.

Video: Author Spotlight: Exploring Venous Waveforms for Non-Invasive Respiratory Monitoring in Pigs

A Model of Chronic Nutrient Infusion in the Rat

Chronic exposure to excessive levels of nutrients is postulated to affect the function of several organs and tissues and to contribute to the development of the many complications associated with obesity and the metabolic syndrome, including type 2 diabetes. To study the mechanisms by which excessive levels of glucose and fatty acids affect the pancreatic beta-cell and the secretion of insulin, we have established a chronic nutrient infusion model in the rat. The procedure consists of catheterizing the right jugular vein and left carotid artery under general anesthesia; allowing a 7-day recuperation period; connecting the catheters to the pumps using a swivel and counterweight system that enables the animal to move freely in the cage; and infusing glucose and/or Intralipid (a soybean oil emulsion which generates a mixture of approximately 80% unsaturated/20% saturated fatty acids when infused with heparin) for 72 hr. This model offers several advantages, including the possibility to finely modulate the target levels of circulating glucose and fatty acids; the option to co-infuse pharmacological compounds; and the relatively short time frame as opposed to dietary models. It can be used to examine the mechanisms of nutrient-induced dysfunction in a variety of organs and to test the effectiveness of drugs in this context.

A protocol for chronic infusions of glucose and Intralipid in rats is described. This model can be used to study the impact of nutrient excess on organ function and physiological parameters.

Chronic exposure to excessive levels of nutrients is postulated to  affect the function of several organs and tissues and to contribute to the  ...

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 ...

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 ...

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 ...

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 ...

Induction and Phenotyping of Acute Right Heart Failure in a Large Animal Model of Chronic Thromboembolic Pulmonary Hypertension

The development of acute right heart failure (ARHF) in the context of chronic pulmonary hypertension (PH) is associated with poor short-term outcomes. The morphological and functional phenotyping of the right ventricle is of particular importance in the context of hemodynamic compromise in patients with ARHF. Here, we describe a method to induce ARHF in a previously described large animal model of chronic PH, and to phenotype, dynamically, right ventricular function using the gold standard method (i.e., pressure-volume PV loops) and with a non-invasive clinically available method (i.e., echocardiography). Chronic PH is first induced in pigs by left pulmonary artery ligation and right lower lobe embolism with biological glue once a week for 5 weeks. After 16 weeks, ARHF is induced by successive volume loading using saline followed by iterative pulmonary embolism until the ratio of the systolic pulmonary pressure over systemic pressure reaches 0.9 or until the systolic systemic pressure decreases below 90 mmHg. Hemodynamics are restored with dobutamine infusion (from 2.5 &#181;g/kg/min to 7.5 &#181;g/kg/min). PV-loops and echocardiography are performed during each condition. Each condition requires around 40 minutes for induction, hemodynamic stabilization and data acquisition. Out of 9 animals, 2 died immediately after pulmonary embolism and 7 completed the protocol, which illustrates the learning curve of the model. The model induced a 3-fold increase in mean pulmonary artery pressure. The PV-loop analysis showed that ventriculo-arterial coupling was preserved after volume loading, decreased after acute pulmonary embolism and was restored with dobutamine. Echocardiographic acquisitions allowed to quantify right ventricular parameters of morphology and function with good quality. We identified right ventricular ischemic lesions in the model. The model can be used to compare different treatments or to validate non-invasive parameters of right ventricular morphology and function in the context of ARHF.

We present a protocol to induce and phenotype an acute right heart failure in a large animal model with chronic pulmonary hypertension. This model can be used to test therapeutic interventions, to develop right heart metrics&#160;or to improve the understanding of acute right heart failure pathophysiology.

The development of acute right heart failure (ARHF) in the context of chronic pulmonary hypertension (PH) is associated with poor short-term outcomes. The ...

Generation of a Rat Model of Acute Liver Failure by Combining 70% Partial Hepatectomy and Acetaminophen

Acute liver failure (ALF) is a clinical condition caused by various etiologies resulting in the loss of metabolic, biochemical, synthesizing, and detoxifying functions of the liver. In most irreversible liver damage cases, orthotropic liver transplant (OLT) remains the only available treatment. To study the therapeutic potential of a treatment for ALF, its prior testing in an animal model of ALF is essential. In the current study, an ALF model in rats was developed by combining 70% partial hepatectomy (PHx) and injections of acetaminophen (APAP) that provides a therapeutic window of 48 h. The median and left lateral lobes of the liver were removed to excise 70% of the liver mass and APAP was given 24 h postsurgically for 2 days. Survival in ALF-induced animals was found to be severely decreased. The development of ALF was confirmed by altered serum levels of the enzymes alanine amino transferase (ALT), aspartate amino transferase (AST), alkaline phosphatase (ALP); changes in prothrombin time (PT); and assessment of the international normalized ratio (INR). Study of the gene expression profile by qPCR revealed an increase in expression levels of genes involved in apoptosis, inflammation, and in the progression of liver injury. Diffused degeneration of hepatocytes and infiltration of immune cells was observed by histological evaluation. The reversibility of ALF was confirmed by the restoration of survival and serum levels of ALT, AST, and ALP after intrasplenic transplantation of syngeneic healthy rat hepatocytes. This model presents a reliable alternative to the available ALF animal models to study the pathophysiology of ALF as well as to evaluate the potential of a novel therapy for ALF. The use of two different approaches also makes it possible to study the combined effect of physical and drug-induced liver injury. The reproducibility and feasibility of current procedure is an added benefit of the model.

The acute liver failure animal model developed in the current study presents a feasible alternative for the study of potential therapies. The current model employs the combined effect of physical and drug-induced hepatic injury and provides a suitable time window to study the potential of novel therapies.

Acute liver failure (ALF) is a clinical condition caused by various etiologies resulting in the loss of metabolic, biochemical, synthesizing, and ...

Bronchoalveolar Lavage and Oleic Acid-Injection in Pigs as a Double-Hit Model for Acute Respiratory Distress Syndrome (ARDS)

The treatment of ARDS continues to pose major challenges for intensive care physicians in the 21st century with mortality rates still reaching up to 50% in severe cases. Further research efforts are needed to better understand the complex pathophysiology of this disease. There are different well-established animal models to induce acute lung injury but none has been able to adequately mimic the complex pathomechanisms of ARDS. The most crucial factor for the development of this condition is the damage to the alveolar capillary unit. The combination of two well-established lung injury models allow us to mimic in more detail the underlying pathomechanism. Bronchoalveolar lavage (BAL) leads to surfactant depletion as well as alveolar collapse. The repeated instillation of fluid volumes causes subsequent hypoxemia. Surfactant depletion is a key factor of ARDS in humans. BAL is often combined with other lung injury approaches, but not with a second hit followed by oleic acid injection (OAI) yet. Oleic acid injection leads to severely impaired gas exchange, a deterioration of lung mechanics and disruption of the alveolo-capillary barrier. The OAI mimics most of the expected effects of ARDS consisting of extended inflammation of lung tissue with an increase of alveolar leakage and gas exchange impairment. A disadvantage of the combination of different models is the difficulty to determine the influence to the lung injury caused by BAL alone, OAI alone or both together. The model presented in this report represents the combination of BAL and OAI as a new double-hit lung injury model. This new model is easy to implement and an alternative to study different therapeutic approaches in ARDS in the future.

Bronchoalveolar Lavage and Oleic Acid-Injection in Pigs as a Double-Hit Model for Acute Respiratory Distress Syndrome ARDS

Different, complex animal models exist to study the pathophysiology of acute respiratory distress syndrome (ARDS). Bronchoalveolar lavage and oleic acid injection induced lung injury is suitable as a new double-hit animal model for studying the acute respiratory distress syndrome.

The treatment of ARDS continues to pose major challenges for intensive care physicians in the 21st century with mortality rates still reaching up to 50% ...

Halogenated Agent Delivery in Porcine Model of Acute Respiratory Distress Syndrome via an Intensive Care Unit Type Device

Acute respiratory distress syndrome (ARDS) is a common cause of hypoxemic respiratory failure and death in critically ill patients, and there is an urgent need to find effective therapies. Preclinical studies have shown that inhaled halogenated agents may have beneficial effects in animal models of ARDS. The development of new devices to administer halogenated agents using modern intensive care unit (ICU) ventilators has significantly simplified the dispensing of halogenated agents to ICU patients. Because previous experimental and clinical research suggested potential benefits of halogenated volatiles, such as sevoflurane or isoflurane, for lung alveolar epithelial injury and inflammation, two pathophysiologic landmarks of diffuse alveolar damage during ARDS, we designed an animal model to understand the mechanisms of the effects of halogenated agents on lung injury and repair. After general anesthesia, tracheal intubation, and the initiation of mechanical ventilation, ARDS was induced in piglets via the intratracheal instillation of hydrochloric acid. Then, the piglets were sedated with inhaled sevoflurane or isoflurane using an ICU-type device, and the animals were ventilated with lung-protective mechanical ventilation during a 4 h period. During the study period, blood and alveolar samples were collected to evaluate arterial oxygenation, the permeability of the alveolar-capillary membrane, alveolar fluid clearance, and lung inflammation. Mechanical ventilation parameters were also collected throughout the experiment. Although this model induced a marked decrease in arterial oxygenation with altered alveolar-capillary permeability, it is reproducible and is characterized by a rapid onset, good stability over time, and no fatal complications.
We have developed a piglet model of acid aspiration that reproduces most of the physiological, biological, and pathological features of clinical ARDS, and it will be helpful to further our understanding of the potential lung-protective effects of halogenated agents delivered through devices used for inhaled ICU sedation.

We describe a model of hydrochloric acid-induced acute respiratory distress syndrome (ARDS) in piglets receiving sedation with halogenated agents, isoflurane and sevoflurane, through a device used for inhaled intensive care sedation. This model can be used to investigate the biological mechanisms of halogenated agents on lung injury and repair.

Acute respiratory distress syndrome (ARDS) is a common cause of hypoxemic respiratory failure and death in critically ill patients, and there is an urgent ...

Dosage-Dependent Induction of Endotoxemia in Pigs via LPS Infusion

Lipopolysaccharide Infusion as a Porcine Endotoxemic Shock Model

Sepsis and septic shock are frequently encountered in patients treated in intensive care units (ICUs) and are among the leading causes of death in these patients. It is caused by a dysregulated immune response to an infection. Even with optimized treatment, mortality rates remain high, which makes further insights into the pathophysiology and new treatment options necessary. Lipopolysaccharide (LPS) is a component of the cell membrane of gram-negative bacteria, which are often responsible for infections causing sepsis and septic shock. 
The severity and high mortality of sepsis and septic shock make standardized experimental studies in humans impossible. Thus, an animal model is needed for further studies. The pig is especially well suited for this purpose as it closely resembles humans in anatomy, physiology, and size. 
This protocol provides an experimental model for endotoxemic shock in pigs by LPS infusion. We were able to reliably induce changes frequently observed in septic shock patients, including hemodynamic instability, respiratory failure, and acidosis. This will allow researchers to gain valuable insight into this highly relevant condition and evaluate new therapeutic approaches in an experimental setting.

Author Spotlight: Induction of Experimental Endotoxemic Shock in Pigs for Studying Hemodynamic and Respiratory Failure

We provide a protocol for an experimental endotoxemic shock model in pigs by infusion of lipopolysaccharide.

Sepsis and septic shock are frequently encountered in patients treated in intensive care units (ICUs) and are among the leading causes of death in these ...