Effectiveness of a heat and moisture exchanger in preventing hyperpnoea induced bronchoconstriction in subjects with asthma.
The effect of a heat and moisture exchanger, a device with hygroscopic material for conditioning inspired air, on hyperpnoea induced bronchoconstriction was studied in nine non-smoking volunteers with asthma, aged 19-32 years. Each had previously shown an increase of at least 100% in specific airways resistance (sRaw) to isocapnic hyperpnoea with dry air. On two separate days the subject performed isocapnic hyperpnoea with dry air at 60-70 l min-1 for five minutes. Before, immediately after, and five minutes after completion of a test sRaw measurements were made. Heat and moisture exchangers were placed in the breathing circuit on one of the two days. All subjects had an increase in sRaw of 100% or more without the heat and moisture exchangers (average increase 300%) but were protected from bronchoconstriction with the devices in place (average increase 7%) (p less than 0.005). The exchanger's resistance to airflow was less than 1 cm H2O for flow rates of 100 l min-1. A heat and moisture exchanger designed as a facemask or mouthpiece may allow a person with asthma to exercise without the need for prophylactic drugs.
Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109-0026.
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Gravelyn
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Capper
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Eschenbacher
D000328:Adult; D000403:Airway Resistance; D001249:Asthma / Q000503:physiopathology / Q000517:prevention & control*; D001985:Bronchial Provocation Tests; D005260:Female; D006358:Hot Temperature; D006801:Humans; D006813:Humidity; D008297:Male; D012119:Respiration; D012138:Respiratory Therapy / Q000295:instrumentation*