[Machine-assisted detection of individually effective minimal CPAP pressure using the Vitalog HMS 5000 monitor]

Continuous positive airway pressure ventilation (CPAP) has been proven to be highly effective in the elimination of sleep-related breathing disorders (SRBD) in the last couple of years. The titration of the effective airway pressure should be carried out under continuous polysomnographic supervision in the sleep laboratory. The CPAP ventilation may result in potential hazards through the positive airway pressure and each patient needs an individually adjusted pressure for therapy. In a prospective study we investigated under polysomnographic supervision the effectivity and the hazards of a machine-controlled CPAP calibration in 22 male patients (pts) (age: 53.6 +/- 8.9 years, BMI: 29.9 +/- 5.0 kg/m2) with obstructive SRBD (RDI: 50.6 +/- 1/h). Automatic CPAP-calibrations were carried out using the Vitalog HMS-5000 monitor and the Respironics BiPAP-STD ventilator. An algorithm determined the cyclical changes of the airway pressure. The following night we controlled the assessed pressure through manual adjustment during conventional polysomnography.

The CPAP-levels assessed through the automatic calibrations (8.36 +/- 2.36 cmH2O) showed in 19 pts a good agreement with the CPAP-levels of the control nights (8.15 +/- 2.36 cmH2O), the difference was statistically nonsignificant (p < 0.5). The CPAP-levels of the automatic titrations and the control nights agreed exactly in 12 pts (63%). 3 pts of the 22 failed the automatic CPAP-titration process because of functional or psychical reasons. 14 pts (64% of 22 pts) showed a good functional tolerance to the cyclical changes of the airway pressure. 3 pts were unable to fall asleep under the increasing airway pressure, but after falling asleep at a constant pressure of 2 or 4 cmH2O they could tolerate the automatic pressure titration. A reset of the actual pressure to the baseline was necessary in 13 pts to enable them falling asleep, in 2 pts because of increase of the airway pressure due to movement artifacts, in 2 pts because of central apneas and in one patient because of ventricular extrasystoles. 35 increases of the baseline level (48% of altogether 73 increases) occurred due to clinically irrelevant desaturations. We found a direct hazardous effect of the machine-controlled CPAP-titration (central apneas, secondary alveolar hypoventilation, ventricular extrasystole) in 7 pts with chronic obstructive pulmonary disease and/or cardiovascular disorder.

The machine-controlled CPAP-titration should be carried out only in a selected group of patients. Nevertheless, despite of the good agreement of the assessed pressure levels with the polysomnographic controls, this method seems to be not suitable for the clinical routine because of its potential hazards and contraindications in high risk patients.