Читать книгу Surgical Critical Care and Emergency Surgery - Группа авторов - Страница 8

Anne Warner, MD, Harsh Desai, MD, and Frederick Giberson, MD

Department of Surgery, Christiana Care Health Care System, Newark, DE, USA

1 In a patient who develops ARDS, the addition of PEEP in optimizing ventilatory support has which of the following effects?Maximal alveolar recruitment with inspiration.Decreasing mean airway pressure.Decreased right ventricular afterload.Improvement of functional residual capacity (FRC).Increasing left ventricular afterload.The use of positive end‐expiratory pressure (PEEP) as part of the ARDS ventilatory strategy has been shown to improve the functional residual capacity (FRC) above the closing pressure of alveoli, thereby preventing alveolar collapse. PEEP maximizes alveolar recruitment at end expiration, not inspiration. The addition of PEEP increases inflation pressure, thereby increasing peak alveolar pressure and ultimately mean airway pressure. Increased PEEP increases pulmonary vascular resistance impeding right vascular stroke volume and thereby left ventricular filling. It also decreases the transmural pressure – the pressure needed to be overcome in order to eject stroke volume – thereby decreasing left ventricular afterload.Answer: DBriel M, Meade M, Mercat A, et al. Higher vs lower positive end‐expiratory pressure in patients with acute lung injury and acute respiratory distress syndrome. JAMA. 2010; 303 (9): 865–873.Schmitt JM, Viellard‐Baron A, Augarde R, et al. Positive end‐expiratory pressure titration in acute respiratory distress syndrome patients: impact on right ventricular outflow impedance evaluated by pulmonary artery Doppler flow velocity measurements. Crit Care Med. 2001; 29: 1154–1158.

2 Which of the following is NOT a component of the inflammatory cascade leading to lung injury in ARDS?Injury to type I and type II epithelial cells within the alveoli.Capillary endothelial dysregulation resulting in recruitment of neutrophils.Sequestration of predominantly lymphocytes within the pulmonary microcirculation.Release of cytoplasmic granules from neutrophil degranulation.Exudation of protein‐rich fluid into the distal airspaces.The inflammatory cascade in ARDS is thought to be initiated by activation of circulating neutrophils by the release of IL‐1 and TNF by macrophages and monocytes. Endothelial dysregulation attracts and retains neutrophils with subsequent sequestration within the pulmonary microcirculation. This occurs through adhesion of neutrophils to endothelial cells and neutrophil stiffening. Neutrophils then move into lung parenchyma and degranulate propagating injury to the type I and II epithelial cells within the alveoli allowing for exudation of protein‐rich fluid, erythrocytes, and platelets into the distal airspaces.Answer: CAbraham E. Neutrophils and acute lung injury. Crit Care Med. 2003; 31(supp): S195–S199.

3 A 27‐year‐old man is undergoing exploratory laparotomy after presenting with a gunshot wound to the left flank. He is currently hemodynamically stable. The operative team has concern for possible ureteral injury and asks that methylene blue be administered for identification of possible urine leak. Shortly after administration, the patient desaturates to SpO2 of 82% with remaining hemodynamics remaining appropriate. What is the management for the etiology of this patient’s desaturation event?Perform a left tube thoracostomy.Immediate bronchoscopy.Abort the procedure.Manual bag mask ventilation.Watch and wait without immediate intervention.The multiple uses of methylene blue have been established including use in methemoglobinemia treatment as well as potential use in vasoplegic syndrome. In the operating room, methylene blue is often used to evaluate renal function and for potential leak in urologic procedures. However, one of the adverse effects of methylene blue is to decrease pulse oximetry readings.Pulse oximeters are made up of a side containing two light emitting diodes that emit at 660nm and 940nm detecting deoxygenated and oxygenated hemoglobin, respectively. The light is captured after passing through the arteries in the finger by a probe on the other side of the oximeter. This is then passed through and alternating current amplifier to block nonpulsatile wave forms from veins. The ratio of oxygenated to total hemoglobin is used to calculate SpO2. When administered, methylene blue transiently decreases the detected oxygenated hemoglobin as the methemoglobin fraction, usually a small percentage of total circulating hemoglobin, increases until processed out through the renal system. Therefore, for this patient, aborting the procedure is not necessary. The desaturation is transient and not caused by mucus plugging, which may require bronchoscopy, pneumothorax, which would require tube thoracostomy, or significant atelectasis, which may require bag mask ventilation.Answer: EClifton J and Leikin JB . Methylene blue. Am J Ther. 2003; 10(4): 289–291.Rong LQ, Mauer E, Mustapich TL, et al. Characterization of the rapid drop in pulse oximetry reading after intraoperative administration of methylene blue in open thoracoabdominal aortic repairs. Anesth Analg. 2019; 129(5): 142–145.

4 A 65‐year‐old woman is in the post‐anesthesia care unit following elective inguinal hernia surgery. Shortly after arriving, she is noted to have increasing shortness of breath and wheezing requiring administration of a nebulized beta agonist. The patient has a known history of COPD. Which of the following pulmonary function test patterns would be expected in a patient with COPD?FEV1 decreased; FVC decreased/normal; FEV1/FVC ratio decreased.FEV1 increased; FVC decreased; FEV1/FVC ratio increased.FEV1 decreased/normal; FVC decreased; FEV1/FVC ratio normal.FEV1 increased; FVC increased; FEV1/FVC ratio increased.FEV1 decreased; FVC decreased; FEV1/FVC ratio decreased.Pulmonary function testing is often used in preoperative evaluation, particularly prior to thoracic procedures. These can be used, in addition to history and exam, to identify obstructive versus restrictive lung processes. Three of the important measures are the forced vital capacity (FVC) – the total volume forcefully expired after maximal inspiratory effort; forced expiratory volume in 1 second (FEV1) – the volume of air forcefully expired after maximal inspiratory effort in 1 second; the FEV1/FVC ratio. In evaluating spirometry results, first step is to interpret the FEV1/FVC ratio. If less than the lower limit of normal, an obstructive pattern is suspected. If greater than lower limit of normal, the FVC is evaluated and if less than lower limit of normal, a restrictive process is considered. Obstructive diseases include COPD, asthma, and emphysema while restrictive lung diseases include neuromuscular disorders and interstitial lung diseases.Answer: ABarreiro TJ and Perillo I . An approach to interpreting spirometry. Am Fam Physician. 2004; 69(5): 1107–1115.Pellegrino R, Viegi G, Brurasco V, et al. Interpretative strategies for lung function tests. Eur Respir J. 2005; 26:948–968.

5 You are caring for a patient in your SICU who is post total abdominal colectomy and end ileostomy. Ileostomy output has been in excess of 1.5L daily with concomitant acute kidney injury noted on basic metabolic panel with continued required resuscitation. Which of the following represents the primary relationships between alveolar pressure (PA), pulmonary arterial pressure (Pa), and pulmonary venous pressure (Pv) within the lung in a state of hypovolemia?Pa > Pv > PA and PA > Pv > PaPA > Pv > Pa and Pa > PA > PvPa > PA > Pv and PA > Pa > Pv PA > Pa > Pv and Pv > Pa > PAPa > PA > Pv and Pa > Pv > PAThe relationship between alveolar pressure, pulmonary arterial pressure, and pulmonary venous pressure represents the West zones of the lung. Zone 1, not seen in normal physiology, signifies alveolar dead space secondary to increased alveolar pressure causing arterial collapse (PA > Pa > Pv). Zone 2 represents pulsatile perfusion (Pa > PA > Pv) typically the upper portions of lung in a typical, upright person. Zone 3 represents the bulk of healthy lung tissue with continuous blood flow without extrinsic compression (Pa > Pv > PA). In a hypovolemic individual, as in this patient, decreased circulating volume converts Zone 3 tissue to Zone 1 and 2, increasing dead space.Answer: CWest JB and Dollery CT . Distribution of blood flow and the pressure‐flow relations of the whole lung. J Appl Physiol. 1965; 20(2): 175–183.For questions 7–10, use the following figure to match the clinical scenario to the appropriate flow volume loop:

6 A 42‐year‐old man presents to the ICU following intubation for COPD exacerbation.

7 An 18‐year‐old woman diagnosed on bronchoscopy with intratracheal lipoma.

8 A recovered COVID‐19 patient who develops tracheal stenosis following a 2 week intubation.

9 A 75‐year‐old male who undergoes emergent intubation following development of angioedema found to have R vocal cord paralysis.Flow volume loops involve plotting inspiratory and expiratory flow on the Y‐axis with volume on the X‐axis, ideally during maximally forced inspiratory and expiratory effort. Flow volume loops are component of the information presented on mechanical ventilators as well and can aid in the diagnosis of airway obstruction. The normal loop is seen in loop A above representing a complete inspiratory and expiratory breath. Loop B demonstrates variable extrathoracic obstruction with a flattening of the inspiratory component. This is due to a combination of atmospheric extraluminal pressure and negative intraluminal pressure exacerbating extrathoracic obstruction as in vocal cord dysfunction and mobile tumors such as lipoma. Intrathoracic variable obstruction, such as with bronchogenic cysts or intrathoracic tracheomalacia, is demonstrated by flattening of the expiratory component, as seen in loop C. Pleural pressure becomes positive relative to airway pressure exacerbating obstruction during expiration. Loop D demonstrates fixed airway obstruction, as with tracheal stenosis, causing flattening of both components of the loop. Finally, loop E demonstrates lower airway obstruction as seen in COPD and asthma. A scooped‐out appearance to the loop comes from premature airway closure as heterogeneity of flow in expiration, i.e., areas with higher elastic recoil and lower airway resistance empty faster than diseased areas.Answers: 6‐E, 7‐B, 8‐C, 9‐BLoutfi SA and Stoller JK . Flow‐volume loops. UpToDate. Retrieved November 16, 2020 from https://www.uptodate.com/contents/flow‐volume‐loops?search=flow%20volume%20loops&source=search_result&selectedTitle=1~59&usage_type=default&display_rank=1Pellegrino R, Viegi G, Brusasco V, et al. Interpretative strategies for lung function tests. Eur Respir J. 2005; 26(5): 948–968.

10 A 72‐year‐old woman is admitted to the trauma ICU after presentation following high‐speed MVC. A pulmonary artery catheter is placed given the patient’s refractory hypotension. Which of the following is consistent with cardiogenic shock?PCWP (mmHg)CO (L/min)SVR (dyne‐sec/cm5)MVO2 (%)A85120070B43180050C143180050D88120070E86180070Though used infrequently within the surgical ICU setting, the Swan‐Ganz catheter is a useful adjunct in the diagnosis of undifferentiated shock. Normal values obtained, as in option A, show a pulmonary capillary wedge pressure (PCWP) 8–12 mmHg, cardiac output (CO) 5–7 L/min, systemic vascular resistance (SVR) 900–1300dyne‐sec/cm5, and mixed venous oxygen (MVO2) approximately 65%. Option B indicates severe hypovolemic shock with decreased PCWP, decreased CO, increased SVR, and decreased MVO2. Option C indicates cardiogenic shock with increased PCWP, decreased CO, increased SVR, and decreased MVO2. Option D indicates distributive shock with normal PCWP, increased CO, decreased SVR, and increased MVO2. Option E indicates obstructive shock with normal PCWP, normal CO, increased SVR, and increased MVO2.Answer: CCecconi M, De Backer D, Antonelli M, et al. Consensus on circulatory shock and hemodynamic monitoring. Task force of the European Society of Intensive Care Medicine. Intensive Care Med. 2014; 40: 1795–1815.

11 A 73‐year‐old female with past medical history of significant peripheral vascular disease, hypertension, and diabetes is admitted to the ICU with significant hypotension following a myocardial infarction in PACU after undergoing EVAR of a 6 cm AAA. STAT echocardiogram shows right‐sided heart failure. Swan‐Ganz catheter is placed with PCWP of 10 mmHg. What is the next appropriate intervention?Inotrope initiation.Vasopressor initiation.Placement of intra‐aortic balloon pump.Volume resuscitation.Diuretic therapy.The initial treatment of choice following acute right heart failure following MI is fluid resuscitation until PCWP > 15 mmHg is reached. Following this, initiation of inotropes, such as dobutamine, is done. Diuretic therapy may play a role in normotensive individuals. Vasopressors may be used in hypotensive patients with the goal of increasing systemic vascular resistance without increasing pulmonary vascular resistance. Fluid resuscitation should be adequate before continuing to increase vasopressor use. The intra‐aortic balloon pump is used in left heart failure, not right heart failure.Answer: DVentetuolo CE and Klinger JR . Management of acute right ventricular failure in the intensive care unit. Ann Am Thorac Soc. 2014; 11(5): 811–822.

12 An 83‐year‐old woman with past medical history of significant peripheral vascular disease, ESRD on peritoneal dialysis admitted following below knee amputation for acute limb ischemia. You are called to bedside for patient’s mean arterial pressure of 55 mmHg. You note the systolic pressure is appropriate, but diastolic pressure remains low. Which of the following is part of the pathophysiology of diastolic heart failure?Adaptive myocyte remodeling.Volume overload of the ventricle.Cell loss secondary to increased oxygen demand.Impaired ventricular wall relaxation.Change of ventricle from elliptical to globular.Diastolic heart failure stems from incomplete relaxation of the ventricle. Three pathophysiologic pathways include impaired ventricular wall relaxation, as left atrial pressure exceeds left ventricular pressure causing pulmonary edema; increased stiffness of the ventricle secondary to increased wall thickness and decreased internal diameter often seen with poorly controlled hypertension; excess collagen deposition as myofibrils are laid in parallel secondary to ischemia, as seen with MI, impairing contractility. The pathophysiology of systolic failure involves adaptive myocyte remodeling, as occurs with CAD, changing ventricular shape resulting in an increasingly overloaded ventricle with decreasing contractility resulting in cell loss due to increased oxygen demand and eventual change of the ventricle from elliptical to globular.Answer: DZile MR, Baicu CF and Gaasch WH . Diastolic heart failure – abnormalities in active relaxation and passive stiffness of the left ventricle. NEJM. 2004; 350: 1953–1959.

13 You are utilizing central venous pressure monitoring to guide resuscitation of a patient with a 60% TBSA burn injury in your ICU. Which of the following components of the CVP waveform represents isovolumic contraction?c wavex descenta wavey descentv waveCVP Waveform componentMechanical eventa waveAtrial contractionc waveIsovolumic contractionv waveSystolic filling of the atriumx descentAtrial relaxation, systolic collapsey descentEarly diastolic filling, diastolic collapseAnswer: AMagder S . Central venous pressure: a useful but not so simple measurement. Crit Care Med. 2006; 34: 2224–2227.

14 Which component of the cardiac cycle is represented by the answer given above?Early diastoleEarly systoleEnd diastoleMid‐systoleEnd systoleThe a wave occurs from right atrial contraction increasing venous pressure. Right ventricular contraction displaces the tricuspid valve into the right atrium, represented by the c wave. With the emptying of right ventricle, the right atrium relaxes and begins to fill, represented by the x descent. The v wave demonstrates the filled right atrium with increased atrial pressure. Finally, the y descent shows right ventricular filling as the tricuspid valve opens.CVP Waveform componentCardiac cycle eventa waveEnd diastolec waveEarly systolev waveLate systolex descentMid‐systoley descentEarly diastoleAnswer: BMagder S . Central venous pressure: a useful but not so simple measurement. Crit Care Med. 2006; 34: 2224–2227.

15 Which of the following is NOT a physiologic effect of minimally invasive left ventricular assist device?Decreased left ventricular end diastolic pressure.Decreased left ventricular wall tension.Increased diastolic pressure.Increased mean arterial pressure.Increased pulmonary capillary pressure.A minimally invasive left ventricular assist device is a miniature axial pump that allows blood to be aspirated from the left ventricle into the cannula component of the pump and expelled above the aortic valve into the ascending aorta. The device has been used for support in high‐risk percutaneous coronary intervention as well as cardiogenic shock. The device works to unload the left ventricle reducing left ventricular end diastolic pressure and wall tension. This allows for decreased oxygen demand. Furthermore, it increased mean arterial pressure, diastolic pressure, and cardiac output, thereby improving both systemic and coronary blood flow. Finally, it decreases pulmonary capillary pressure and thereby right ventricular afterload.Answer: EBurzotta F, Trani C, Doshi S, et al. Impella ventricular support in clinical practice: collaborative viewpoint from a European expert user group. Int J Cardiol. 2015; 201: 684–691.

16 Which of the following is a physiologic impact of intra‐aortic balloon pumps during systole?Increased systolic blood pressure.Decreased pre‐systolic aortic pressure.Increase in the isometric phase of left ventricular contraction.Increased left ventricular wall tension.Decreased left ventricular ejection fraction.The intra‐aortic balloon pump follows the principle of counterpulsation i.e. inflation during diastole with deflation during systole. The physiologic impacts during the systolic phase include a decrease in aortic systolic pressure as well pre‐systolic (end‐diastolic) aortic pressure both of which contribute to decreased afterload by 10% and 30%, respectively; decrease in the isometric phase of left ventricular contraction, thereby reducing myocardial oxygen consumption; decreased left ventricular wall tension by 20%; increased left ventricular ejection fraction by up to 30%.Answer: BParissis H, Graham V, Lampridis S, et al. IABP: history‐evolution‐pathophysiology‐indications: what we need to know. J Cardiothorac Surg. 2016; 11(1): 122.

17 Which of the following is an expected cardiovascular change during pregnancy?Decreased heart rate.Decreased cardiac output.Increased peripheral vascular resistance.Decreased ventricular distension.Decreased systemic vascular resistance.Pregnancy results in increased heart rate, increased cardiac output, decreased peripheral vascular resistance, increased ventricular distension, and decreased systemic vascular resistance.Answer: EHill CC and Pickinpaugh J . Physiologic changes in pregnancy. Surg Clin N Am. 2008; 88: 391–401.

18 Which of the following is a mechanism by which vasodilators improve cardiac function in acute decompensated heart failure?Increased ventricular preload.Decreased stroke volume.Increased ventricular afterload.Increased cardiac output.Increased ventricular filling pressure.The pathophysiology of acute heart failure involves increased myocardial oxygen demand with increased ventricular filling pressures, low cardiac output, and increased systemic vascular resistance. Nitroprusside and nitroglycerin remain two of the most potent vasodilators used in therapy. Nitrogylcerin is a venodilator working to decrease preload, decrease afterload, and myocardial oxygen demand. Nitroprusside is an arterial and venous dilator decreasing preload, afterload, myocardial oxygen demand as well as increasing stroke volume and cardiac output.Answer: DCarlson MD and Eckman PM . Review of vasodilators in acute decompensated heart failure: the old and new. J Card Fail 2013; 19(7): 478–493.

19 Which of the following is an expected effect of increased intrapleural pressure from positive pressure ventilation?Increased venous return.Increased aortic pressure.Baroreceptor dampening.Increased systemic vascular resistance.Increased preload.With positive pressure ventilation, increased intrapleural pressure results in initially increased aortic pressure causing compensatory reduction in systemic vascular resistance and left ventricular afterload by activated baroreceptors, thereby increasing cardiac output. Positive pressure additionally decreases venous return and, therefore, preload.Answer: BAlviar CL, Miller PE, McAreavey D, et al. Positive pressure ventilation in the cardiac intensive care unit. J Am Coll Cardiol. 2018; 72: 1532–1553.

20 A 70‐year‐old woman in a motor vehicle collision undergoes a splenectomy for Grade IV laceration and receives four units of whole blood in the OR but arrives in the ICU tachycardiac and hypotensive. Point of care hemoglobin is 14.3 mg/dL 2 hours post‐transfusion. Her abdomen was left open and minimal output is coming from her negative pressure abdominal dressing. She has multiple rib fractures and a radius fracture. Which of the following therapies would promote end‐organ perfusion?Decrease vasoactive drug doses (decrease peripheral vascular resistance).Increase sedation and pain medications to decrease her heart rate.Increase end‐diastolic volume with volume resuscitation.Increase contractility with positive inotrope.Increase end‐systolic volume.This patient has evidence of blunt chest trauma with multiple rib fractures and tachycardia. While she could have hypovolemic shock from her splenic injury and intraoperative blood loss, she remains hypotensive despite transfusions with a hemoglobin of 14.3 mg/dL making this less likely and no evidence of ongoing bleeding from her abdomen. This makes it less likely that further volume resuscitation with blood or crystalloid would be helpful. Blunt cardiac injury can occur with blunt chest trauma and is initially screened for with EKG and troponin assessment, followed by an echocardiogram. Blunt cardiac injury may be improved with positive inotropic medications.Decreasing vasoactive drug doses would worsen hypotension and worsen end‐organ perfusion. Vasopressors are often used in supportive treatment for blunt cardiac injury and may need to be increased to promote end‐organ perfusion. Increasing sedation and pain medications may improve her tachycardia but would worsen her hypotension and end‐organ perfusion. Increasing end‐systolic volume would decrease her stroke volume and cardiac output further, worsening her end‐organ perfusion.Remember: Answer: DLevick JR. An Introduction to Cardiovascular Physiology. Butterworth and Co., London, 2013.Clancy K, Velopulos C, Bilaniuk JW, et al. Screening for blunt cardiac injury: An Eastern Association for the Surgery of Trauma practice management guideline. J Trauma Acute Care Surg. 2012; 73 5: S301–S306.

21 A 39‐year‐old man presents with a cold right leg and complains of nine days of symptoms. Following a thromboembolectomy and fasciotomy, he develops hypoxia with saturation of 87% and respiratory distress. An arterial blood gas shows: pH 7.47, paO2 = 50 mm Hg, HCO3 = 22 mmol/L, pCO2 = 30 mm Hg. Chest x‐ray shows patchy consolidations bilaterally and he reports fever prior to admission and that he works in a skilled nursing facility during the pandemic.Based on the above results, his A‐a gradient is (at sea level, water vapor pressure = 47 mm Hg):150 mm Hg10 mm Hg38 mm Hg50 mm Hg62 mm HgA‐a gradient equals PAO2−PaO2. His PaO2 from the ABG is 50. The PAO2 can be calculated from this equation: Therefore, A‐a gradient (PaO2−PAO2) = 62.5 mm Hg.Answer: EMarino P. The ICU Book , 3rd ed., Lippincott Williams & Wilkins, Philadelphia, PA, chapter 19 2007.

22 The patient above is placed on a nonrebreather mask with minimal improvement. What is the most likely etiology of the above patient’s respiratory failure and appropriate intervention?Pulmonary embolism, anticoagulation.Hyperventilation from anxiety, benzothiazines.COVID‐19 pneumonia, dexamethasone, and high‐flow nasal canula.Neuromuscular weakness, reversal of paralytic.Pulmonary edema, acute kidney injury from rhabdomyolysis.Hypoxemia occurs in four conditions: low inspired oxygen, shunt, V/Q mismatch, and hypoventilation.Hypoventilation would present with high CO2 and normal A‐a gradient. This could occur with oversedation, neuromuscular weakness, and residual anesthesia. Hyperventilation would cause tachypnea, low CO2, but not hypoxia, so A‐a gradient should be normal. Low inspired oxygen should have a low PO2 and normal gradient. An acute PE or asthma exacerbation presents with V/Q mismatch with elevated A‐a gradient and normal PCO2. It should correct with administration of oxygen. Shunting (pulmonary edema or pneumonia) has an elevated A‐a gradient that does not improve with oxygen administration. The patient is young for postoperative MI and has risk factors and a chest x‐ray consistent with COVID‐19 pneumonia, which could also increase his risk of thrombotic events since as an arterial thrombus.Answer: CWeinberger SE, Cockrill BA and Mande J. Principles of Pulmonary Medicine , 5th ed., W.B. Saunders, Philadelphia, PA, (2008).NIH COVID‐19 Treatment Guidelines. Therapeutic management of patients with COVID‐19. www.covid19treatmentguidelines.nih.gov/therapeutic‐management/ (accessed 15 December 20).

23 A 63‐year‐old patient with history of hypertension and type 2 diabetes presents with acute respiratory distress syndrome from pneumococcal pneumonia and is being managed by the ICU team for severe ARDS. After appropriate sedation and analgesia, which of the following is NOT an appropriate strategy for management?Low tidal volume ventilation (4–8ml/kg IBW).Prone positioning <6 hours/day.Use of recruitment maneuvers.Higher PEEP levels with plateau pressures <30 cm H2O.Very select use of high‐frequency oscillatory ventilation.Acute respiratory distress syndrome management guidelines target management with low tidal volume ventilation, low inspiratory pressures with plateau pressures <30 cm H20, high PEEP levels are better than low PEEP levels, and prone positioning for at least 12‐hour periods per day with improved mortality. Less than 6 hours of prone position per day would not be recommended as it is too short a time period.Answer: BFan E., Del Sorbo L, Goligher EC, et al. An Official American Thoracic Society/European Society of Intensive Care Medicine/Society of critical care medicine clinical practice guideline: mechanical ventilation in adult patients with acute respiratory distress syndrome. Am J Respir Crit Care Med. 2017; 195 9: 1253–1263. https://www.thoracic.org/statements/resources/cc/ards‐guidelines.pdf.