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A 77-year-old man on chronic hemodialysis is evaluated in the emergency department for severe dyspnea. He is in respiratory distress, but is alert and responsive. His blood pressure is 216/92 mm Hg, pulse rate 122/min, and respiration rate 44/min. He is using accesssory muscles to breath. He has jugular venous distention; examination of the lungs reveals bilateral crackles, and cardiac examination reveals a summation gallop with a 3/6 systolic ejection murmur. There is no edema. Arterial blood gases on 50% oxygen by high-flow mask are PO2 64 mm Hg, PCO2 50 mm Hg, and pH 7.24. Electrocardiography shows sinus tachycardia with nonspecific STT wave abnormalities, and chest radiograph is pending. He receives oxygen supplementation, nitroglycerin, furosemide, and small doses of morphine, but remains very dyspneic.
Which of the following intervention would most likely avoid intubation in this patient?
A Increasing the dose of morphine; continue nitroglycerin and furosemide
B Starting noninvasive continuous positive airway pressure (4 cm H2O)
C Starting noninvasively administered pressure support (8 cm H2O) and PEEP (4 cm H2O)
D Increase the FiO2 via face mask
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Correct Answer = C)
Key Point
In patients with cardiogenic pulmonary edema, continuous positive airway pressure (CPAP) and noninvasive positive pressure ventilation (NPPV) more rapidly improve dyspnea, vital signs and gas exchange, and avoid intubation more effectively than oxygen supplementation plus standard therapy.
This patient presents with typical features of acute cardiogenic pulmonary edema. Randomized, controlled trials on such patients have demonstrated that both continuous positive airway pressure (CPAP) and noninvasive positive pressure ventilation (NPPV) more rapidly improve dyspnea, vital signs and gas exchange, and avoid intubation more effectively than oxygen therapy plus standard therapy. NPPV would be the preferred initial therapy “ to œbuy time until hemodialysis can started. It is important to understand that bilevel ventilation using portable noninvasive devices and pressure support plus PEEP administered by a critical ventilator (used mainly in intubated patients) are essentially the same but use different terminology. With bilevel devices, the inspiratory pressure is the total inspiratory pressure, whereas with critical ventilators, the pressure support is added to the PEEP. Thus, a pressure support of 10 cm H2O and PEEP of 5 cm H2O using critical care ventilator terminology is the same as an inspiratory pressure (IPAP) of 15 cm H2O and expiratory pressure (EPAP) of 5 cm H2O using bilevel terminology. A recent meta-analysis concluded that neither CPAP nor NPPV was superior to the other in patients with acute pulmonary edema, although some individual trials have suggested that NPPV can more rapidly reduce the sensation of dyspnea and improve gas exchange compared to CPAP alone. Thus, CPAP alone would be a reasonable choice here, except that a level of 4 cm H2O would be considered inadequate (10 to 12.5 cm H2O was used in the randomized studies). Additional medical therapy or more supplemental oxygen would be unlikely to help much because the patient has not responded to adequate doses of medication and PaO2 is in an acceptable range. Furthermore, the patient is on chronic hemodialysis and the definitive therapy is emergent dialysis.
