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* From the Division of Pulmonary and Critical Care Medicine of University Hospitals of Cleveland (Drs. Ciufo, Novak, McFadden, Ms. Nelson, and Mr. Coreno), and the Department of Medicine of Case Western Reserve University School of Medicine, Cleveland, OH; the Division of Pulmonary and Critical Care (Dr. Chien), Harborview Medical Center, Seattle, WA; and Asthma Clinical Management and Research Center (Ms. Nelson), MetroHealth Medical Center, Cleveland, OH.
Correspondence to: E. R. McFadden Jr., MD, Division of Pulmonary and Critical Care Medicine, University Hospitals of Cleveland, 11100 Euclid Ave, Cleveland, OH 44106-5067; e-mail: erm2{at}po.cwru.edu
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 Hg); 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 Hg; p = 0.0003). The increase was considered to be a
physiologic manifestation of the Haldane effect (ie,
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 seven 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
six patients (40%), it worsened (PaCO2 before
oxygen, 46.8 ± 1.9; during oxygen, 52.0 ± 3.1 mm Hg; 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 carbon dioxide elimination.
Key Words: acute asthma carbon dioxide retention gas exchange respiratory failure uncontrolled oxygen administration
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