The term hypoxemic respiratory failure refers to a subgroup of patients whose acute respiratory failure is characterized by severe hypoxemia (ie, Pao2/fraction of inspired oxygen [Fio2] ratio, ≤ 200), severe respiratory distress (ie, respiratory rate, > 35 breaths/min), and a non-COPD diagnosis including pneumonia, ARDS, trauma, or cardiogenic pulmonary edema.17
Studies on this subgroup of patients have yielded conflicting results. Meduri et al25–
have reported success with NPPV in all four patients with hypoxemic respiratory failure in their early trial. Later, however, Wysocki et al26
observed no significant benefit that was attributable to NPPV among patients with hypoxemic respiratory failure, unless patients were hypercapnic. In a large, uncontrolled series of 158 patients with various forms of respiratory failure who had been treated with NPPV, Meduri et al17
identified 41 with hypoxemic respiratory failure, 66% of whom avoided endotracheal intubation. Subsequently, Antonelli et al27–
randomized 64 patients with hypoxemic respiratory failure to receive therapy with NPPV or prompt intubation. Baseline characteristics including the Pao2/Fio2 ratio (which was approximately 120) and therapies for the conditions precipitating the respiratory failure were similar in both groups, with the exception of baseline pH, which was lower in control subjects than in the NPPV group (7.37 vs 7.45, respectively; p = 0.002). NPPV was as effective as invasive mechanical ventilation in improving oxygenation within the first hour, and only 10 of the 32 NPPV patients required intubation. Patients in the NPPV group had significantly fewer septic complications, and exhibited strong trends toward shorter stays in the ICU and lower mortality rates. In another randomized trial of patients with various forms of respiratory failure,28
therapy with NPPV lowered intubation and mortality rates in the subgroup of patients with hypoxemic respiratory failure.