Role of obstructive events and carbon dioxide accumulation in obesity hypoventilation syndrome

Schematic illustration of the primary end-point data obtained in the present study.
(A) Spirometry tracing illustrating a postevent increase in ventilation to levels above control periods with stable ventilation. The immediate postevent ventilation was assessed by summing the tidal volumes for all breaths initiated within the first 10 seconds of the interevent period.
(B) Graph illustrating the calculation of CO₂ load during respiratory events. Thin line, average metabolic CO₂ production over time; thick line, varying breath-by-breath CO₂ excretion measured during changes in ventilation. CO₂ load during event (shaded areas) is calculated by integrating the difference between breath-by-breath CO₂ excretion and average metabolic CO₂ production during the event.