Noninvasive ventilation in life-threatening asthma: A case series

The use of noninvasive ventilation (NIV) in severe acute asthma is controversial. A pH < 7.25, PaCO₂ > 60 mmHg, and altered mental status have been described as contraindications to NIV in acute asthma. We hypothesized that NIV was safe and effective in asthma patients with a pH < 7.25 or PaCO₂ > 60 mmHg.

Following institutional review board approval, the medical records of subjects who received NIV for acute asthma in the emergency department between January 2010 and July 2012 were reviewed. Subjects were included if they had a pH < 7.25 or PCO₂ > 60 mmHg on either an arterial or venous blood gas. Primary outcome was need for endotracheal intubation.

Sixty-two subjects received NIV for asthma, with 20 (mean age 42 ± 12 years, 62% male) meeting the inclusion criteria. Intubation was avoided in all 20 subjects, including nine (45%) with prior history of intubation due to asthma, eight (40%) who were obtunded, and three (15%) who were unresponsive upon arrival. Results are described as medians (ranges). Initial blood gas (80% venous) results were: pH 7.16 (6.89-7.27), PCO₂ 77 (65-144) mmHg, and HCO₃ ^- 27 (20-32) mmol/L. Repeat blood gases (45% venous) performed a median of 117 minutes later were: pH 7.31 (7.22-7.45), PCO₂ 48 (31-63) mmHg, and HCO3 23 (19-31). Vomiting occurred in one patient; no other adverse events were noted.

We identified a small series of asthma patients with severe respiratory acidosis or altered mental status in whom NIV was safe and effective.