[Inspiratory intrathoracic pressure changes in obstructive and mixed sleep apnea]

Oesophageal pressure swings were analysed during complete occlusion of the upper airways in 8 patients with obstructive sleep apnoea. We hypothesed that in dependence of the apnoea type, there is a significant decrease in oesophageal inspiratory effort in REM vs. NREM that is caused by a decrease of the respiratory drive. We analysed in each patient 40 apnoeas in which the respiratory timing (Ti) and the inspiratory effort (Pin) were calculated and compared with the type of apnoea and the degree of oxygen desaturation. A significant decrease in inspiratory effort in REM vs NREM occurred only in mixed apnoeas but not in patients with mainly obstructive apnoeas. Additionally, all apnoeas with a decrease of inspiratory effort at the end of apnoea during NREM were seen in obstructive apnoeas only, whereas none occurred in mixed apnoeas. Due to the significant lower inspiratory timing during obstructive apnoeas vs mixed apnoeas we assume a decrease in respiratory drive in the patients suffering mainly from obstructive apnoeas.