Critical Care Medicine Mechanical Ventilation: Review Questions Karthikeyan Kanagarajan, MD, and John M. Oropello, MD, FCCP, FCCM Dr. Kanagarajan is a fellow in critical care medicine, and Dr. Oropello is a program director of critical care medicine and an associate professor of surgery and medicine; both are at Mount Sinai School of Medicine, New York, NY. Choose the single best answer for each question.
	1. A 24-year-old woman presents to the ICU with acute respiratory distress syndrome (ARDS) caused by urosepsis. She is intubated, started on mechanical ventilation, sedated, and then paralyzed. The ventilator settings are: pressure control-inverse ratio ventilation (PC-IRV) mode with an inspiratory pressure of 25 cm H2O; respiratory rate (RR), 15 breaths/min; inspiratory time, 2.5 s; Fio2, 80%; and positive end-expiratory pressure (PEEP), 8 cm H2O. On these settings, her peak inspiratory pressure (PIP) and plateau pressures (Pp) are 33 cm H2O, and tidal volume (VT) is 350 mL. Sao2 is 92% on pulse oximetry. Thirty minutes later, she becomes hypotensive, desaturates, and has decreased breath sounds over the left lung. Chest radiography shows a left-sided pneumothorax. What changes in ventilator parameters do you expect to find at this time? PIP, 60 cm H2O; Pp, 60 cm H2O; VT, 350 mL; RR, 15 breaths/min PIP, 60 cm H2O; Pp, 60 cm H2O; VT, 200 mL; RR, 15 breaths/min PIP, 33 cm H2O; Pp, 33 cm H2O; VT, 200 mL; RR, 15 breaths/min PIP, 33 cm H2O; Pp, 33 cm H2O; VT, 350 mL; RR, 40 breaths/min Click here to compare your answer. 2. A 35-year-old asthmatic man develops acute respiratory failure requiring mechanical ventilation. A mucous plug develops acutely. Ventilator graphics at baseline and following the mucous plug are shown in the Figure. According to the Figure, what mode of mechanical ventilation is this patient receiving? Assist/control mode ventilation Pressure-control ventilation Pressure-support ventilation Pressure regulated volume control ventilation (PRVC) Click here to compare your answer.		3. A 64-year-old man presents to the ED with an exacerbation of COPD. He is intubated and mechanically ventilated on: assist/control mode; RR, 16 breaths/min; VT, 600 mL; inspiratory flow rate (IFR), 60 L/min; PEEP, 0 cm H2O; and Fio2, 40%. Physical examination reveals: an anxious man in severe respiratory distress; heart rate, 120 bpm; blood pressure, 80/40 mm Hg; RR, 36 breaths/min; and Sao2, 85%. Cardiac examination is normal; lung examination reveals bilateral expiratory wheezing with equal breath sounds. PIP is 45 cm H2O, Pp is 35 cm H2O, and ventilator graphics show that the expiratory flow waveform does not return to zero before the next ventilator breath is delivered. Chest radiography reveals hyperinflated lung fields. Despite intravenous fluids, bronchodilators, and sedation, the patient remains in respiratory distress and is hypoxic and hypotensive. Which ventilator changes would be most beneficial? Decrease VT, increase IFR, add PEEP Increase VT, decrease IFR, add PEEP Decrease VT, decrease IFR, continue zero PEEP Increase VT, increase IFR, continue zero PEEP Click here to compare your answer.
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