Effects of short-term 28% and 100% oxygen on PaCO2 and peak expiratory flow rate in acute asthma -: A randomized trial

Study objective: We conducted the first randomized controlled study to assess the effects of short-term 28% and 100% oxygen on PaCO2 and peak expiratory flow rate (PEFR) in patients with acute severe asthma. Patients and interventions: 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 PaCO2 (p = 0.03) and decreases PEFR (p = 0.001) as compared with administration of 28% oxygen. PaCO2 before and during oxygen administration correlated significantly (p = 0.001) in both groups. Patients breathing 28% oxygen experienced a PaCO2 fall; on the contrary, patients who received 100% oxygen showed an increase in PaCO2, particularly those with PaCO2 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 greater than or equal to 92% rather than on prescribing predetermined concentrations or flow rates of inspired oxygen.