Constancy of the nCPAP pressure values in the long-term monitoring of patients with obstructive sleep apnea

A retrospective study was undertaken to discover how often mask pressures had to be adjusted over time in patients treated for sleep apnoea by continuous positive airway pressure (nCPAP). Data were analysed on 106 such patients (95 men, 11 women; mean age 55.6 [33-74] years). Their body-mass index was 31.5 +/- 5.5 kg/m2, the apnoea hypopnea index before adjustment 7.6 +/- 2.2 mbar. At the first control, after a median of 7.5 months, the pressure had to be adjusted in 55% of patients, by an average of 8.3 +/- 2.4 mbar (P < 0.001). At the second and third follow-ups (after 19.5 and 31.5 months, respectively), no further significant adjustment in mean pressure was necessary, while changes had to be made in 34.0% and 17.9%, respectively. Changes in body weight correlated with changes in pressure level (r = 0.4614 for difference between initial setting and first control; r = 0.6708 for first and second controls; r = 0.7013 for second and third controls). 61% of patients in whom mask pressure had to be altered had symptoms. Of those in whom the pressure had to be increased 82% had symptoms. Only 17% of patients requiring no change had symptoms. These findings indicate that patients on nCPAP must be monitored by polysomnography about 6 months after the initial setting, and further tests should be performed about a year apart. If body weight and feeling of well being are maintained, non-laboratory monitoring should be adequate.