RT Journal Article
SR Electronic
T1 Effects of supplemental O<sub>2</sub> on PCO<sub>2</sub> and ventilation in people with obesity hypoventilation syndrome
JF European Respiratory Journal
JO Eur Respir J
FD European Respiratory Society
SP P3186
VO 40
IS Suppl 56
A1 Carly Hollier
A1 Alison Harmer
A1 Lyndal Maxwell
A1 Collette Menadue
A1 Gunnar Unger
A1 Grant Willson
A1 Amanda Piper
YR 2012
UL http://erj.ersjournals.com/content/40/Suppl_56/P3186.abstract
AB Breathing 100% O2 increases PCO2 in some people with obesity hypoventilation syndrome (OHS). It is not known how lower concentrations of O2 affect people with OHS. This study investigated the effect of clinically relevant O2 concentrations on PCO2, pH and minute ventilation (VE) in stable OHS patients pre and post treatment with positive airway pressure (PAP), and in controls. In a double-blind randomised crossover study, 14 subjects with OHS and 14 age- and gender-matched controls breathed inspired O2 fractions (FiO2) of 0.28 and 0.5, each for 20min, separated by a 45min washout. The OHS group were retested after 3 months of nocturnal PAP. Arterialised-venous PCO2 and pH, and VE were measured every 5min. Data were analysed with repeated measures ANOVA. In OHS pre-PAP, small rises in PCO2 of 2.0±1.7mmHg; 3.7±3.2mmHg (both p&lt;0.01) occurred after 20min of breathing FiO2 0.28 and 0.5, respectively, with no significant difference between concentrations. pH fell accordingly, with FiO2 0.5 inducing mild acidaemia (7.346±0.030, p&lt;0.01). VE fell below the room air baseline for both FiO2 0.28 (-5±11%, p&lt;0.01) and FiO2 0.5 (-7±20%, p&lt;0.01). The controls' responses differed significantly from the OHS group (p&lt;0.01). PCO2 and pH did not change significantly with either FiO2 and mild hyperventilation occurred (VE +1.3±19%, FiO2 0.28; +12±17%, FiO2 0.5). In OHS, O2-induced PCO2 rises tended to be smaller after PAP (1.3±2.3mmHg, FiO2 0.28; and 0.9±1.7mmHg, FiO2 0.5). Commonly used concentrations of O2 caused hypoventilation, small PCO2 rises and mild acidaemia in stable OHS. When providing supplemental O2 for people with stable OHS, close monitoring and targeting of O2 saturations is recommended.