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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 ≥ 92% rather than on prescribing predetermined concentrations or flow rates of inspired oxygen.

      Key words

      Abbreviations:

      CI (confidence interval), PEFR (peak expiratory flow rate), Spo2 (pulse oximetric saturation), V˙/ Q˙ (ventilation/perfusion)
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