Effects of short-term 28% and 100% oxygen on PaCO2 and peak expiratory flow rate in acute asthma: a randomized trial.
OBJECTIVE
We conducted the first randomized controlled study to assess the effects of short-term 28% and 100% oxygen on PaCO(2) and peak expiratory flow rate (PEFR) in patients with acute severe asthma.


METHODS
Seventy-four patients (mean age, 37.9 +/- 9.7 years [+/- SD]; PEFR, 41.0 +/- 12.1% of predicted) from two emergency departments were randomized to receive 28% or 100% oxygen during 20 min.


RESULTS
The administration of 100% oxygen significantly increases PaCO(2) (p = 0.03) and decreases PEFR (p = 0.001) as compared with administration of 28% oxygen. PaCO(2) before and during oxygen administration correlated significantly (p = 0.001) in both groups. Patients breathing 28% oxygen experienced a PaCO(2) fall; on the contrary, patients who received 100% oxygen showed an increase in PaCO(2), particularly those with PaCO(2) before oxygen treatment > 40 mm Hg.


CONCLUSIONS
This study confirmed previous observations that oxygen dose should be variable and based on achieving and maintaining target arterial oxygen saturation measured by pulse oximetry > or = 92% rather than on prescribing predetermined concentrations or flow rates of inspired oxygen.
Rodrigo
Gustavo J
GJ
Departamento de Emergencia, Hospital Central de las Fuerzas Armadas, Montevideo, Uraguay. gurodrig@adinet.com.uy
Rodriquez Verde
Mario
M
Peregalli
Virginia
V
Rodrigo
Carlos
C
D000208:Acute Disease; D000328:Adult; D001249:Asthma / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology*; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D010100:Oxygen / Q000008:administration & dosage* / Q000494:pharmacology; D010366:Peak Expiratory Flow Rate / Q000187:drug effects; D012720:Severity of Illness Index; D013997:Time Factors
D002245:Carbon Dioxide; D010100:Oxygen