G. Wenzel

Charakteristik mehrerer Befeuchter für die CPAP- sowie invasive und nicht invasive Beatmungstherapie und Sauerstofflangzeittherapie unter standardisierten Bedingungen in einer Klimakammer

INTRODUCTION Patients receiving mechanical ventilation and oxygen therapy frequently complain about the dryness of their airways. Humidifiers increase air humidity by generating water vapour and thus preventing the mucosa from desiccation. In this bench study, we compared the efficiency of several humidifiers. METHODS Two identical humidifiers of each type (HC 602, HumiCare 200, Humid Aire 2i, minni-Max, MR 730 AGM, REMstar, Sirius, Somnia2, Somno Comfort2, VENTIclick, VIVO 30) were measured at three different heating intensities (low, medium, high) and three different flow rates (20, 55 and 90 l/min). The relative humidity at the exit of the tube and the temperature of the water in the heating chamber were registered. Additionally, we measured the humidity of the oxygen humidifier Respiflo at 1 - 5 l/min, the Respiflo was filled with either NaCl 0.9% or Aqua dest. Measurements were taken in a climatic chamber at 20 degrees C and 50% relative humidity. The atmospheric pressure was taken into consideration. RESULTS The MR 730 AGM and Humicare 200 generated a constant relative humidity of 100%. Among the remaining humidifiers, only the HC 602, HumidAire 2i and REMstar reached a humidity of about 95% at high flow rates. The Minni-Max, Somnia2 and VIVO 30 generated a humidity of 95% still at a flow rate of 55 l/min. The Sirius, Somno Comfort2 and the VENTIclick generated this amount of humidity only at low flow rates of 20 l/min. The three humidifiers mentioned last generated a relative humidity of only 68 - 76 at high flow rates of 90 l/min. The Respiflo generates a humidity of about 90% at each flow rate (1 - 5 l/min.), independent of being filled with NaCl 0.9% or Aqua dest. CONCLUSION Factors determinating the efficacy of humidifiers are the velocity of the airstream, the temperature of the water, the contact surface of the air and water compartments and the turbulence of the airstream. In vivo the amount of leakage is a very important determinant for the velocity of the airstream. In the care of mechanically ventilated patients one should have an approximate idea of the magnitude of the applied air flows. The limitations of some humidifiers should be known. The simple presence of a humidifier in combination with a respirator does not mean that the problem of dryness of the airway mucosa is eliminated.

Poststationäre Nachsorge und probatorische CPAP-Therapie schlafbezogener obstruktiver Atemstörungen steigern die Langzeitcompliance

INTRODUCTION Since the implementation of CPAP therapy in the treatment of obstructive sleep apnoea in the 1980 s researchers have been looking for predictors and possibilities to improve long-term compliance. In a prospective randomised trial we examined the influence of a follow-up examination two weeks after the start of probatory CPAP therapy compared to immediate prescription of the CPAP device. METHODS 249 new patients with a newly diagnosed obstructive sleep apnoea (OSA) started with a CPAP therapy. These patients were prospectively randomised depending on the dates of admission (even/uneven). The CPAP device for the first group was immediately prescribed. Patients of the second group were seen in our sleep laboratory ambulance after a probatory usage of the CPAP therapy over a period of fourteen days. After 433 +/- 138 days we measured the compliance by reading off the operating hours counter. In order to collect these data all patients received written simple instructions how to read off the operating hours counter. They sent back the results via a prepaid return envelope. In addition, we obtained the information as to whether a hot water bath humidifier was used. RESULTS 171 of the initially 249 patients sent back the evaluation form. The randomisation of the groups was successful concerning: age, sex as well as the apnoea-hypopnoea index before and under CPAP therapy. 226 patients were treated with the fix-CPAP mode (mean pressure 8.1 +/- 1.8 cm H(2)O), 23 patients received auto CPAP therapy. The patients with a probatory CPAP therapy and follow-up examination showed a significantly (p = 0.01) better compliance of nocturnal CPAP use with 4.5 +/- 1.8 h/night versus those who had their CPAP device immediately prescribed with a use of 3.8 +/- 2.1 h/night. The percentage of patients with a use of CPAP more than 4 h/night was significantly higher in the group with probatory therapy (66.3 % vs. 45.6 %; p = 0.008). Patients with probatory CPAP therapy made more use of humidifiers than the immediate prescription group; however, the use of a humidifier did not have any significant influence on the long-term compliance (p = 0.58). CONCLUSION The combination of probatory CPAP therapy and follow-up examination increases the long-term compliance significantly in the treatment of obstructive sleep apnoea.