Critical Care Medicine-Neurologic Disorders>>>>>Mechanical Ventilation
Question 1#

A 45-year-old previously healthy woman presents to the emergency department with 3 days of fevers and progressive dyspnea and is admitted to the intensive care unit (ICU) for influenza infection complicated by severe hypoxemia. She is intubated, and chest radiograph following intubation demonstrates an appropriately placed endotracheal tube with bilateral patchy opacities and interstitial markings throughout all lung fields, without effusions. Her bedside echocardiogram reveals a left ventricular ejection fraction of 0.75 with otherwise normal findings. Her ventilator settings are:

• volume control
• tidal volume (VT) 500 mL
• respiratory rate (RR) 14 breaths per minute
• FiO₂ 1.0
• positive endexpiratory pressure (PEEP) 5 cm H₂O

An initial arterial blood gas (ABG) is:

• pH 7.30
• PCO₂ 45 mm Hg
• PO₂ 80 mm Hg

Which of the following therapies has been best shown to improve the survival of patients such as this woman?

A. Diuresis to maintain a negative fluid balance
B. Ventilation at a TV of 6 mL/kg of ideal body weight (IBW)
C. Initiation of inhaled pulmonary vasodilator for severe hypoxemia
D. Bronchoscopy to rule out additional infections
E. Titration of PEEP with recruitment maneuver to optimize lung compliance

Correct Answer is B

Comment:

Correct Answer: B

This patient is presenting with severe ARDS, as defined by the Berlin criteria: onset within 1 week or presentation, bilateral opacities on imaging, edema not fully explained by cardiogenic etiology, and PaO₂ :FiO₂ ratio of <100. The ARDSnet trial demonstrated a significant mortality benefit with lung protective, low-TV ventilation (6 mL/kg IBW) (answer B is correct). Diuresis to an even fluid balance increases ventilator-free days in patients with ARDS but has not been found to have a mortality benefit (answer A is incorrect). Similarly, while inhaled nitric oxide and PEEP titration may improve oxygenation, neither intervention has been demonstrated to improve survival (answers C and E are incorrect). Invasive respiratory cultures are not recommended in patients with severe community acquired pneumonia (answer D is incorrect).

References:

1. Ranieri VM, Rubenfeld GD, Thompson BT, et al. Acute respiratory distress syndrome: the Berlin definition. JAMA. 2012;307(23):2526-2533.
2. The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory disress syndrome. N Engl J Med. 2000;342:1301-1308.
3. Gebistorf F, Karam O, Wetterslev J, Afshari A. Inhaled nitric oxide for acute respiratory distress syndrome (ARDS) in children and adults. Cochrane Database Syst Rev. 2016;(6):CD002787.
4. Writing Group for the Alveolar Recruitment for Acute Respiratory Distress Syndrome Trial (ART) Investigators. Effect of lung recruitment effect of lung recruitment and titrated positive endexpiratory pressure (PEEP) vs low peep on mortality in patients with acute respiratory distress syndrome. JAMA. 2017;318(14):1335-1345.