Validity of arterialised-venous PCO2, pH and bicarbonate in obesity hypoventilation syndrome

This prospective study investigated the validity of arterialised-venous blood gases (AVBG) for estimating arterial carbon dioxide (PCO2 ), pH and bicarbonate (HCO3 −) in people with obesity hypoventilation syndrome (OHS). AVBGs were obtained from an upper limb vein, after heating the skin at 42–46 ◦C. Arterial blood gas (ABG) and AVBG samples were taken simultaneously and compared using Bland Altman analysis. Between-group differences were assessed with independent t-tests or Mann–Whitney U tests. Forty-two viable paired samples were analysed, including 27 paired samples from 15 OHS participants, and 15 paired samples from 16 controls. AVBG–ABG agreement was not different between groups, or between dorsal hand, forearm and antecubital AVBG sampling sites, and was clinically acceptable for PCO2 : mean difference (MD) 0.4 mmHg (0.9%), limits of agreement (LOA) −2.7–3.6 mmHg (±6.6%); pH: MD −0.008 (−0.1%), LOA −0.023–0.008 (±0.2%); and HCO3 −: MD −0.3 mmol L−1 (−1.0%), LOA −1.8–1.2 mmol L−1 (±5.3%). AVBG provides valid measures of PCO2 , pH, and HCO3 − in OHS.