A new management of humidification under superimposed high-frequency jet-ventilation in combination with a new prototype of a jet-ventilator

Background and goal of study

This study introduces a new prototype of an eletronic jet ventilator which is capable of simultaneously delivering two separate jet streams with different frequencies to the patient. This ventilation technique is called superimposed high-frequency jet-ventilation (SHFJV). We want to show, in a prospective, randomized, observational study, that the problems of humidification, under SHFJV can be prevented, using this new jet-ventilator (Alexander 1, Fa. Fesco, Vienna, Austria).

Material and methods

After institutional approval forty patients, 16 female, 24 male with a median age of 67 years (range 55 to 79 years) were randomly allocated to one of four groups (A, B, C, D) ten in each group, receiving either SHFJV by the Alexander 1 (group A and group B), or high frequency oscillation (HFO) by a VDR 4 (group C), or conventional mechanical ventilation (CMV) by an Evita (Group D). All patients were ventilated for more than 100 h because of respiratory insufficiency [1]. The relative humidity (RH) of the inspiration gas (FM-C1, E u E. Elektronic, Unterwiesen, Austria) and its temperature (temperature sensor line 21076 A, Hewlett Packard, Palo Alto, CA) were measured twice a day. Bronchoscopy (Olympus BF Type 20D, Olympus Optical Co., LTD, Shirikawa, Japan) was performed twice a day too. Humidification and warning of the ventilation gas was done using three different humidification systems. In group A, we used a combined form of a humidification and warming-system. Whereas the entrained gas (bias flow) was humidified by a hot water humidifier (Aquapor, Type 8406640 Fa. Dräger, Corp., Lübeck, Germany), humidification of the jet gas was achieved by a continuous infusion of 0.9% saline via a special jet adapter into the high pressure jet line. The instilled saline infusion was warmed by a fluid warmer (HL-90 INT, Level 1 Technologies Corp., Rockland, MA, USA) up to 37°C before it reached the jet gas. In group B, we used the same system without the fluid warmer. In group C and D, we used a hot water humidifier. In all four groups, several patients were exposed to intermittent prone position in case of extremely severe ARDS. Data were statistically analyzed using t-test and Fischer-test (rectification according to Yates).

Results and discussion

To evaluate the amount of tracheobronchial mucosal injury, a scoring system was used, taking into account the size of the area and the extent of macroscopic epithelial damage. Group A, C and D had a mucosal injury score of zero, no significant pathologic evidence could be seen. The temperature values (group A: 31.4°C; group C: 32.1°C; group D: 34.2°C:) were insignificantly different. In group B, the temperature was significantly lower (27°C) than in all other groups. Inflammation of the tracheal mucosa was found and the mucosal injury score was significantly higher.

Conclusion

Using the ALEXANDER 1 for SHFJV with high humidity, almost all the problems, which are associated to this ventilation technique, like tracheal epithelial inflammation, necrotizing tracheobronchits (NT), etc can be prevented.