Noninvasive Ventilation Intolerance: Characteristics, Predictors, and Outcomes

Noninvasive ventilation (NIV) intolerance is one reason for NIV failure. However, the characteristics, predictors, and outcomes of NIV intolerance are unclear. A prospective observational study was performed in the respiratory intensive care unit of a teaching hospital. Subjects with acute respiratory failure who used NIV were enrolled. Initially, continuous use of NIV was encouraged. However, if the subject could not tolerate NIV, it was used intermittently. NIV intolerance was defined as termination of NIV due to subject refusal to receive it because of discomfort, even after intermittent use was attempted. A total of 961 subjects were enrolled in the study. Of these, 50 subjects (5.2%) experienced NIV intolerance after a median 2.4 h of NIV support. Age (OR = 0.98, 95% CI 0.963-0.996) and heart rate (OR = 1.02, 95% CI 1.006-1.030) measured before NIV were 2 independent risk factors of NIV intolerance. After 1-2 h of NIV, independent risk factors of NIV intolerance were heart rate (OR = 1.03, 95% CI 1.016-1.044) and breathing frequency (OR = 1.06, 95% CI 1.027-1.099). Intolerant subjects had no improvement in mean arterial pressure, heart rate, or breathing frequency after the NIV intervention. Moreover, intolerant subjects had a higher intubation rate (44.0% vs 25.8%, P = .008) and higher mortality (34.0% vs 22.4%, P = .08). The three most common complaints were that NIV worsened subjects' distress (46%), that NIV resulted in dyspnea (26%), and that the flow or pressure of NIV was too strong to bear (16%). NIV intolerance worsened subjects' outcomes. Younger subjects with a high heart rate and breathing frequency may be more likely to experience NIV intolerance.