The Science Journal of the American Association for Respiratory Care

2001 OPEN FORUM Abstracts


DavidWillms MD, Jodette Brewer RRT, Melissa Brown RRT, Ashlynn LeBlanc RN.Sharp Memorial Hospital, San Diego, California. Sharp Mary Birch Hospital forWomen, San Diego, California.

Background:We hypothesized that heliox administered to early ARDS patients would improvegas exchange by improving ventilation of partially atelectatic regions and augmentingdiffusive gas mixing. A pilot study was initiated and the results in the first5 patients reported here.

Methods:Five ARDS patients intubated < 96 h, and with FiO2 < .80 wereentered after informed consent. Subjects were ventilated with a Servo 300 inPRVC or PCV mode, with VT 6-8 ml/kg. A Novametrix Co2smoPlus respiratory mechanics monitor, calibrated to the heliox concentration,was attached at the patient Y and used for VT, expired CO2and VD/VT monitoring. Heliox was begun with FiO2equal to baseline; reduction in FiO2 was accomplished if feasiblebased on oxygenation. ABGs and physiologic measurements were obtained at baselineand at 1, 4, and 8 h of heliox, whereupon subjects were returned to nitrogen-oxygenbreathing. Efforts were made to maintain stable VT, PEEP, and respiratoryfrequency throughout. One patient required reduction in set rate due to hypocapnea.Four patients were pharmacologically paralyzed at the time of study.

Results:Baseline characteristics (mean values) were: Age 42 y; FiO2 0.54;PEEP 11.8 cmH2O; PaO2 82 torr; PCO2 43.8 torr;VD/VT 0.74; PaO2/FiO2 ratio 156.Mean values for the gas exchange values were not significantly changed duringthe 8 h study (see Table); however two individual patients experienced a notablereduction in AaDO2 from baseline to 8 h (292 to 171, and 162 to 73).No adverse events from heliox therapy were noted.

Baseline1 h4 h8 hp value*
AaDO2260 2792222200.23

*Paired Student?s t-test, baselinevs. 8 h values

Conclusion:In this short-term heliox trial, no significant change in gas exchange was noted.However 2 patients had a substantial reduction in AaDO2. It is possiblethat some individual patients may benefit from heliox, or that a longer durationof heliox inhalation may have an effect. Future study is planned.



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