Fig. 4. Pearson correlation coefficients between end-tidal carbon dioxide pressure (Etco2) and arterial carbon dioxide pressure (Paco2) with each device/cannula and patient group. Patient groups are normal weight patients (defined as a body mass index < 30 kg/m2) without a diagnosis of obstructive sleep apnea (Non-obese non-OSA), obese patients (body mass index > 35 kg/m2) without a diagnosis of obstructive sleep apnea (Obese non-OSA), and obese patients (body mass index > 35 kg/m2) with obstructive sleep apnea (Obese OSA). ** P < 0.01.