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Dehumidifiers for chronic asthma

  1. Meenu Singh1,*,
  2. Nishant Jaiswal2

Editorial Group: Cochrane Airways Group

Published Online: 13 JUN 2013

DOI: 10.1002/14651858.CD003563.pub2


How to Cite

Singh M, Jaiswal N. Dehumidifiers for chronic asthma. Cochrane Database of Systematic Reviews 2013, Issue 6. Art. No.: CD003563. DOI: 10.1002/14651858.CD003563.pub2.

Author Information

  1. 1

    Post Graduate Institute of Medical Education and Research, Department of Pediatrics, Chandigarh, India

  2. 2

    Advanced Pediatrics Centre, Post Graduate Institute of Medical Education and Research, ICMR Advanced Centre for Evidence-Based Child Health, Chandigarh, India

*Meenu Singh, Department of Pediatrics, Post Graduate Institute of Medical Education and Research, Sector 12, Chandigarh, 160012, India. meenusingh4@gmail.com. meenusingh@rediffmail.com.

Publication History

  1. Publication Status: Edited (no change to conclusions)
  2. Published Online: 13 JUN 2013

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Characteristics of included studies [ordered by study ID]

MethodsDesign of study: randomised controlled trial, parallel group.
Method of randomisation: not stated.
Concealment of randomisation: not stated.
Blinding: none.
Description of withdrawals or dropouts: not stated.


ParticipantsTotal number of participants enrolled into trial = 40 (13 adults and 27 children).
Total number of participants in each randomised group: not given; final number of adults in each group is given (group 1 = 5; group 2 = 4; group 3 = 2; group 4 = 2).
Age: 13 adults (range 20-67 years, mean 40.1 years).
27 children (range 4-16 years, mean 9.7 years).
Sex: Adults - 9 men and 4 women.
Children - 17 boys and 10 girls.
Physician diagnosed asthma, with moderate to severe asthma.
Inclusion criteria: Ability to perform peak flow measurements, flow-volume loop, histamine bronchial challenge, and reacting positive to a skin-prick test at least 5 mm in diameter for D pteronyssinus. Moderate to severe asthmatics requiring prophylactic medications.
Participants also had to live in homes fulfilling pre-determined inclusion criteria, information for which was gathered by questionnaires.
Source of participants: hospital asthma clinics.


InterventionsSetting: home.
Interventions: (four randomised groups):
Group 1: Mechanical ventilation and heat recovery (MVHR) and high efficiency vacuum cleaning (HEVC).
Group 2: MVHR only.
Group 3: HEVC only.
Group 4: Control group (no intervention).
Duration of trial: 12 months.


OutcomesDaily symptom diaries recording:
wheeze, cough and activity; medication use; PEF (am and pm).
FEV1 and histamine challenge tests.


NotesRandomisation was inadequate due to re-allocation of homes which were not considered suitable for installation of mechanical ventilators.
Authors have been contacted for additional data.


Risk of bias

BiasAuthors' judgementSupport for judgement

Allocation concealment (selection bias)Unclear riskInformation not available.

Blinding (performance bias and detection bias)
All outcomes
High riskNone

Random sequence generation (selection bias)Unclear riskInformation not available.

Blinding of participants and personnel (performance bias)
All outcomes
High riskNone

Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskInformation not available.

Incomplete outcome data (attrition bias)
All outcomes
Unclear riskInformation not available.

Selective reporting (reporting bias)Unclear riskInformation not available.


MethodsDesign of study: randomised controlled trial, parallel group, placebo control, double-blind

Method of randomisation: Random number generator

Concealment of randomisation : concealed from patient and clinical research team.

Blinding : Double-blinding

Description of withdrawals and dropouts: 18 protocol violators and 1 withdrawal.


ParticipantsTotal no. of participants included: 119

Total no. of participants in each randomised group: MHRV (Mechanical heat recovery ventilation system)-60 & Placebo control-59

Age: 16-60 yrs (Mean age for MHRV (41.6) and Placebo control (42.3) if had asthma for more than 1 year and on regular inhaled corticosteroids and had daily symptoms.

Gender : No. of males in MHRV:41 and in placebo control:32

No. of females in MHRV :19 and in placebo control :27

Inclusion criteria: Variable air flow obstruction of >=12% on spirometry or >= 15% on peak expiratory flow (PEF) or symptom score of >=0.86% on Asthma Control Questionnaire (ACQ).

Participants had a minimum forced expiratory volume (FEV 1) of >50% and had not had an exacerbation in the previous month.

Allergy to D. pteronyssinus was determined by positive skin test defined as a wheal diameter of >=3mm greater than that of negative control at 15 min.

Subjects also had to live in homes fulfilling pre-determined inclusion criteria.

Source of participants: general practice and hospital clinics.


InterventionsSetting : home

Group I: MHRV (Mechanical heat recovery ventilation system)

Group II: Placebo control

Duration of trial: 12 months


OutcomesDaily symptom dairies recording : sneezing, nasal blockage and nasal discharge.

PEF (morning and evening)

FEV1 : Baseline and 12 months


NotesThe study was insufficiently powered to demonstrate a clinical response; only 100 of 119 participants completed follow-up.

The reduced relative humidity was insufficient to impact on Der p1 burden, and there was also no difference between the groups in change in serum house dust mite specific IgE antibody. Domestic dehumidification has reduced mite allergen burden in some.


Risk of bias

BiasAuthors' judgementSupport for judgement

Allocation concealment (selection bias)Low riskUnit activation device was concealed from the patient and the clinical research team.

Blinding (performance bias and detection bias)
All outcomes
Low riskDouble-blinded study.

Random sequence generation (selection bias)Low riskRandomisation was created using the random number generator.

Blinding of participants and personnel (performance bias)
All outcomes
Low riskDouble-blinded study.

Blinding of outcome assessment (detection bias)
All outcomes
Low riskClinical research team & the patients were unaware of the intervention.

Incomplete outcome data (attrition bias)
All outcomes
Low riskOutcome data are complete.

Selective reporting (reporting bias)Low riskNo selective reporting.

 
Characteristics of excluded studies [ordered by study ID]

StudyReason for exclusion

Arlian 1999Laboratory based controlled observation

Burr 2007Randomised study of strategies to reduce indoor mould & complications of asthma. Humidification was not provided as standard across the intervention group

Cabrera 1995Not a randomised controlled trial

Chivato 1997Not a randomised controlled trial but an observational study.

Crane 1998Not a randomised controlled trial.

Emenius 1993Not a randomised controlled trial, observational study reported as an abstract.

Harving 1994Not a randomised controlled trial.

Hyndman 2000A randomised study where dehumidification has been used to control house dust mite. No patient outcomes have been studied.

Kercsmar 2006Randomised study of numerous environmental remediation strategies to reduce indoor mould. Humidification was not provided as standard across the intervention group.

Korsgaard 1983Not a randomised controlled trial

Morgan 2004The focus of study was in the reduction of level of cockroach allergen & dust mite & complication of asthma. No outcome was recorded regarding dehumidification.

Mosbech 1988Controlled study with no mention about randomisation.

 
Comparison 1. MHRV versus placebo

Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size

 1 Change in morning PEF at 12 months (% predicted)1Mean Difference (Fixed, 95% CI)Totals not selected

 2 Change in evening PEF at 12 months (% predicted)1Mean Difference (Fixed, 95% CI)Totals not selected

 3 Change in FEV1 at 12 months (% predicted)1Mean Difference (Fixed, 95% CI)Totals not selected

 4 Change in rescue medication (puffs/day) after 12 months1Mean Difference (Fixed, 95% CI)Totals not selected

 5 Change in ACQ score after 12 months1Mean Difference (Fixed, 95% CI)Totals not selected

 6 Change in SGRQ score after 12 months1Mean Difference (Fixed, 95% CI)Totals not selected

 7 Exacerbations needing oral steroids1Odds Ratio (M-H, Random, 95% CI)Totals not selected

 8 Exacerbation needing GP visit1Odds Ratio (M-H, Random, 95% CI)Totals not selected

 9 Exacerbation needing GP out of hours1Odds Ratio (M-H, Random, 95% CI)Totals not selected

 10 Exacerbations needing ED visit1Odds Ratio (M-H, Random, 95% CI)Totals not selected

 11 Exacerbations needing hospitalisation1Odds Ratio (M-H, Random, 95% CI)Totals not selected

 
Summary of findings for the main comparison. MHRV compared to placebo for asthmatics with sensitivity to house dust mite

MHRV compared with placebo for asthmatics with sensitivity to house dust mite

Patient or population: asthmatics with sensitivity to house dust mite
Settings: Community
Intervention: MHRV
Comparison: placebo

OutcomesIllustrative comparative risks* (95% CI)Relative effect
(95% CI)
No of Participants
(studies)
Quality of the evidence
(GRADE)
Comments

Assumed riskCorresponding risk

PlaceboMHRV

Change in Morning PEF after 12 months (% predicted)

Follow-up: 12 months
Change of -7% on placeboChange of +6.4% on MHRVMD 13.59 % (-2.66 to 29.84)100
(1 study)
⊕⊕⊕⊝
moderate1

Change in Evening PEF after 12 months (% predicted)

Follow-up: 12 months
Change of -12% on placeboChange of +12% on MHRVMD 24.56 % (8.97 to 40.15)100
(1 study)
⊕⊕⊕⊝
moderate1

Change in FEV1 after 12 months (% predicted)

Follow-up: 12 months
Change of +1.8% on placeboChange of +1.0% on MHRVMD 1.32 % (-2.55 to 5.19)100
(1 study)
⊕⊕⊕⊝
moderate1

Quality of life

SGRQ

Scale from 0 to 100 (0 on the scale is better)

Follow-up: 12 months
Change of -2.1 units on placeboChange of -5.2 units on MHRVMD -2.83 units

(-7.82 to 2.16)
100

(1 study)
⊕⊕⊕⊝
moderate1

Exacerbations needing oral steroids
Follow-up: 12 months
362 per 1000228 per 1000
(111 to 413)
OR 0.52
(0.22 to 1.24)
100
(1 study)
⊕⊕⊕⊝
moderate1

Exacerbations needing ED visit
Follow-up: 12 months
43 per 100076 per 1000
(14 to 319)
OR 1.84
(0.32 to 10.52)
100
(1 study)
⊕⊕⊕⊝
moderate1

Exacerbations needing hospitalisation
Follow-up: 12 months
85 per 10008 per 1000
(0 to 138)
OR 0.09
(0 to 1.72)
100
(1 study)
⊕⊕⊕⊝
moderate1

*The basis for the assumed risk is the mean control group risk. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
CI: Confidence interval; OR: Odds ratio;

GRADE Working Group grades of evidence
High quality: Further research is very unlikely to change our confidence in the estimate of effect.
Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
Very low quality: We are very uncertain about the estimate.

 1 Single study with wide confidence interval
MD: mean difference
MHRV: mechanical heat recovery ventilation system
OR: odds ratio
PEF: peak expiratory flow