title: Effect of improved home ventilation on asthma control and house dust mite allergen levels.
abstract: BACKGROUND
  The warm, humid environment in modern homes favours the dust mite population, but the effect of improved home ventilation on asthma control has not been established. We tested the hypothesis that a domestic mechanical heat recovery ventilation system (MHRV), in addition to allergen avoidance measures, can improve asthma control by attenuating re-colonization rates.
  
  
  METHODS
  We conducted a randomized double-blind placebo-controlled parallel group trial of the installation of MHRV activated in half the homes of 120 adults with asthma, allergic to Dermatophagoides pteronyssinus. All homes had carpets steam cleaned and new bedding and mattress covers at baseline. The primary outcome was morning peak expiratory flow (PEF) at 12 months.
  
  
  RESULTS
  At 12 months, the primary end-point; change in mean morning PEF as compared with baseline, did not differ between the MHRV group and the control group (mean difference 13.5 l/min, 95% CI: -2.6 to 29.8, P = 0.10). However, a secondary end-point; evening mean PEF, was significantly improved in the MHRV group (mean difference 24.5 l/min, 95% CI: 8.9-40.1, P = 0.002). Indoor relative humidity was reduced in MHRV homes, but there was no difference between the groups in Der p 1 levels, compared with baseline.
  
  
  CONCLUSIONS
  The addition of MHRV to house dust mite eradication strategies did not achieve a reduction in mite allergen levels, but did improve evening PEF.
authors: Department of Respiratory Medicine, Division of Immunology, Infection and Inflammation, University of Glasgow, Glasgow, UK.
authors: G R
authors: GR
authors: Wright
authors: S
authors: S
authors: Howieson
authors: C
authors: C
authors: McSharry
authors: A D
authors: AD
authors: McMahon
authors: R
authors: R
authors: Chaudhuri
authors: J
authors: J
authors: Thompson
authors: I
authors: I
authors: Donnelly
authors: R G
authors: RG
authors: Brooks
authors: A
authors: A
authors: Lawson
authors: L
authors: L
authors: Jolly
authors: L
authors: L
authors: McAlpine
authors: E M
authors: EM
authors: King
authors: M D
authors: MD
authors: Chapman
authors: S
authors: S
authors: Wood
authors: N C
authors: NC
authors: Thomson
mesh_terms: D000328:Adult; D000485:Allergens / Q000032:analysis* / Q000276:immunology; D000818:Animals; D039741:Antigens, Dermatophagoides / Q000032:analysis / Q000276:immunology; D001249:Asthma / Q000517:prevention & control*; D040002:Dermatophagoides pteronyssinus / Q000276:immunology; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000276:immunology; D008297:Male; D008875:Middle Aged; D010366:Peak Expiratory Flow Rate; D039981:Pyroglyphidae / Q000276:immunology*; D016896:Treatment Outcome; D014691:Ventilation / Q000379:methods*
chemical_list: D000485:Allergens; D039741:Antigens, Dermatophagoides