[Heated humidification during CPAP with and without tube insulation]

Patients with obstructive sleep apnoea syndrome (OSAS) under continuous positive pressure (CPAP) often complain about drying-up of the throat and nasal mucosa. In many cases the problem can be eliminated with a heated humidifier (WLB). Especially in a cold environment condensation forming on cooling of the air in the tube and the mask can be observed. To avoid this, some patients use an insulating tube covering. We investigated the effect of temperature (T) and relative humidity (rH) of the environment, the ventilation pressure, mask leaks, insulation of tubing on the T and rH% of the delivered air at the end of the tube or in the mask in OSAS patients.

All measurements were performed with a conventional WLB (S8, Resmed Fa) and a temperature and humidity sensor (Fa Testo, Lenzkirch).

8 patients with OSAS were examined during the day at a room temperature of 16.4 degrees C.

The temperature at the outlet of the WLB increased with a higher ambient temperature. Through isolation with a hose cover the temperature drop in the tube was reduced by 2.3 degrees C. By tube insulation a mean increase in temperature between 1.6 and 1.0 C during normal breathing in dependence on the leakage flow in the mask was found.

Due to additional insulation with a tube cover the mask temperature can be increased, albeit slightly, and the formation of condensation is reduced.