A new prototype of an electronic jet-ventilator and its humidification system

Background: Adequate humidification in long-term jet ventilation is a criti cal aspect in terms of clinical safety. Aim: To assess a prototype of an electronic jet-ventilator and its humidifi cation system. Methods: Forty patients with respiratory insufficiency were randomly alloca ted to one of four groups. The criterion for inclusion in this study was re spiratory insufficiency exhibiting a Murray score above 2. The four groups of patients were ventilated with three different respirators and four diffe rent humidification systems. Patients in groups A and B received superimpos ed high-frequency jet ventilation (SHFJV) by an electronic jet-ventilator e ither with (group A) or without (group B) an additional humidification syst em. Patients in group C received high-frequency percussive ventilation (HFP V) by a pneumatic high-frequency respirator, using a hot water humidifier f or warming and moistening the inspiration gas. Patients in group D received conventional mechanical ventilation using a standard intensive care unit r espirator with a standard humidification system. SHFJV and HFPV were used f or a period of 100 h (4 days). Results: A significantly low inspiration gas temperature was noted in patie nts in group B, initially (27.2 +/- 2.5 degrees C) and after 2 days (28.0 /- 1.6 degrees C) (P< 0.05). The percentage of relative humidity of the ins piration gas in patients in group B was also initially significantly low (6 9.8 +/- 4.1%; P< 0.05) but rose to an average of 98 +/- 2.8% after 2 h. The average percentage across all four groups amounted to 98 +/- 0.4% after 2 h. Inflammation of the tracheal mucosa was found in patients in group B and the mucosal injury score (MIS) was significantly higher than in all the ot her groups. Patients in groups A, C and D showed no severe evidence of airw ay damage, exhibiting adequate values of relative humidity and temperature of the inspired gas. Conclusion: The problems of humidification associated with jet ventilation can be fully prevented by using this new jet-ventilator. These data were su stained by nondeteriorating MIS values at the end of the 4-day study period in groups A, C and D.