The Effect of Supplemental Oxygen on Hypercapnia in Subjects with Obesity-associated Hypoventilation: A Randomized, Crossover, Clinical Study: Wijesinghe M, Williams M, Perrin K, Weatherall M, Beasley R. Chest 2011;139:1018–24.

Abstract

It is well known that supplemental oxygen can cause worsening hypercapnia in patients with chronic obstructive pulmonary disease. This study sought to determine if the same effect is seen in patients with obesity-associated hypoventilation (OAH). In this double-blind, randomized, controlled, crossover trial of 24 patients newly diagnosed with OAH, subjects inhaled either 100% oxygen or room air via full-face continuous positive airway pressure mask, without positive airway pressure, for 20 min on 2 separate days. Baseline measurements of transcutaneous carbon dioxide tension (PtCO2), minute ventilation, and volume of dead-space-to-tidal-volume ratio were compared to the same values at 20 min by mixed linear model to determine differences between the two treatments. All subjects who completed the study (23 of 24) participated in both of the treatments on separate days within 7 days. Testing was terminated early in 3 subjects while breathing 100% oxygen secondary to a rise in PtCO2 of ≥ 10 mm Hg, whereas none of the patients breathing room air required early termination of the treatment protocol. PtCO2 increased by 5.0 mm Hg (95% confidence interval [CI] 3.1–6.8, P < 0.001) with oxygen compared to room air. Minute ventilation decreased by 1.4 L/min (95% CI 0.11–2.6 L/min; p < 0.03), and volume-of-dead-space-to-tidal-volume ratio increased by 0.067 (95% CI 0.035–0.1; p < 0.001), with oxygen compared to room air. This study demonstrated that breathing 100% oxygen worsens hypercapnia in stable patients with OAH.