Uncontrolled oxygen administration and respiratory failure in acute asthma

Study objectives: To determine if 100% oxygen administration adversely influences gas exchange in acutely ill asthmatic subjects. Design: Prospective preinterventional and postinterventional comparison. Setting: University hospital emergency department. Patients: Thirty-seven asthmatic subjects seeking care for symptomatic exacerbations. Interventions: Twenty minutes of 100% oxygen administration by face mask. Measurements and results: Arterial blood gases and FEV1 were measured before and during the last minute of oxygen administration, On presentation, the subjects had moderately severe airway obstruction (FEV1, 49.1 +/- 3.6% of predicted); hypocarbia (PaCO2, 36.8 +/- 1.1 mm Hg); hypoxemia (PaO2, 70.2 +/- 2.5 mm E-Ig); and respiratory alkalosis (pH, 7.43 +/- 0.01), During oxygen breathing, 25 patients (67.6%) experienced elevations in PaCO2 ranging from 1 to 10 mm Hg (mean, 4.1 +/- 0.6 mm IIE;; p = 0.0003), The increase was considered to be a physiologic manifestation of the Haldane effect (ie, less than or equal to 2 mm Hg) in 10 subjects, but in the remaining 15 subjects (40.5% of the total studied), the elevation represented worsening gas exchange, In se ren of these patients (46.7%), hypercapnic respiratory failure developed (PaCO2 before oxygen, 39.6 +/- 0.6; during oxygen, 44.7 +/- 0.7 mm Hg; p = 0.005), and in sis patients (40%), it worsened. (PaCO2 before oxygen, 46.8 +/- 1.9; during oxygen, 52.0 +/- 3.1 min IIE;; p = 0.03), In general, the tendency toward hypercarbia was the greatest in the participants with the most severe airway obstructions. Conclusions: Our data demonstrate that the administration of 100% oxygen to acutely ill asthmatics may adversely influence cal bon dioxide elimination.