The quality of evidence is downgraded by study limitations (unclear allocation concealment and lack of blinding), by inconsistency (variability in results), and by imprecise results (few patients).
A Cochrane review [Abstract] 1 included 2 studies with a total of 160 subjects. The first open-label study compared an intervention consisting of mechanical ventilation heat recovery system with or without high efficiency vacuum cleaner fitted in 40 homes of patients with asthma who had positive tests for sensitivity to house dust mite (13 adults and 27 children). No clinical benefit to asthma patients was observed. There was a decline in the house dust mite count and the antigen level.
The second double-blind study compared a mechanical ventilation heat recovery system with a placebo machine in the homes of 119 asthmatic adults with allergy to house dust mite. The study showed no significant difference in morning peak flow (MD 13.59, 95% CI -2.66 to 29.84) but there was a statistically significant improvement in evening peak flow (MD 24.56, 95% CI 8.97 to 40.15). There was no significant difference in quality of life, rescue medication, requirement for oral corticosteroids, visits to the GP, emergency department (ED) or hospitalisations for asthma. There was no significant difference in the house dust mite count and the antigen levels.
Primary/Secondary Keywords