Background: It is unknown whether oxygen therapy causes worsening hypercapnia in patients with obesity-associated hypoventilation (OAH), similar to the response observed in COPD. The objectives of this study were to investigate whether breathing 100% oxygen results in an increase in hypercapnia in patients with OAH and the mechanisms of any effect.
Methods: In this double-blind, randomized, controlled, crossover trial, 24 outpatients with newly diagnosed OAH inhaled 100% oxygen or room air for 20 min on 2 separate days. Transcutaneous CO(2) tension (Ptco(2)), minute ventilation, and volume of dead space to tidal volume ratio were measured at baseline and at 20 min. A mixed linear model was used to determine differences between the two treatments.
Results: The study was terminated in three subjects breathing 100% oxygen due to a Ptco(2) increase ≥ 10 mm Hg, which occurred after 10:35, 13:20, and 15:51 min. Ptco(2) increased by 5.0 mm Hg (95% CI, 3.1-6.8; P < .001) with oxygen compared with room air. Minute ventilation decreased by 1.4 L/min (95% CI, 0.11-2.6 L/min; P = .03), and volume of dead space to tidal volume ratio increased by 0.067 (95% CI, 0.035-0.10; P < .001) with oxygen compared with room air.
Conclusions: Breathing 100% oxygen causes worsening hypercapnia in stable patients with OAH.
Trial registry: Australia New Zealand Clinical Trials Registry; No.: ACTRN 12608000592347; URL: www.anzctr.org.au.