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Cochrane Database of Systematic Reviews

Intercambiadores de calor y humedad frente a humidificadores térmicos para adultos y niños ventilados mecánicamente

Information

DOI:
https://doi.org/10.1002/14651858.CD004711.pub3Copy DOI
Database:
  1. Cochrane Database of Systematic Reviews
Version published:
  1. 14 September 2017see what's new
Type:
  1. Intervention
Stage:
  1. Review
Cochrane Editorial Group:
  1. Cochrane Emergency and Critical Care Group

Copyright:
  1. Copyright © 2018 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.

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Authors

  • Donna Gillies

    Correspondence to: Sydney, Australia

    [email protected]

    [email protected]

  • David A Todd

    Neonatal Unit, The Canberra Hospital, Canberra, Australia

  • Jann P Foster

    School of Nursing and Midwifery, Western Sydney University, Penrith DC, Australia

  • Bisanth T Batuwitage

    Department of Anaesthesia, Queen Alexandra Hospital, Portsmouth Hospitals NHS Trust, Portsmouth, UK

Contributions of authors

2017 Update

Co‐ordinating the review: Gillies D.

Screening search results: Gillies D, Todd D, Foster J, Batuwitage B.

Appraising quality of papers: Kelly MT, Gillies D, Todd D, Lockwood C.

Data extraction: Gillies D.

Writing to authors of papers for additional information: Gillies D.

Entering data into Review Manager: Gillies D.

Writing the review: Gillies D, Todd D, Foster J, Batuwitage B, Correia M, Carvalho R.

Guarantor for the review (one author): Gillies D.

People responsible for reading and checking review before submission: Gillies D, Todd D, Foster J, Batuwitage B.

Contributions of authors in original review (Kelly 2010a)

Developing protocol: Kelly MT, Gillies D, Todd D, Lockwood C.

Co‐ordinating the review: Kelly MT, Gillies D.

Screening search results: Kelly MT, Todd D, Lockwood C.

Organizing retrieval of papers: Kelly MT, Gillies D.

Screening retrieved papers against inclusion criteria: Kelly MT, Gillies D, Todd D, Lockwood C.

Data extraction: Kelly MT, Gillies D, Todd D, Lockwood C.

Writing to authors of papers for additional information: Kelly MT, Gillies D.

Entering data into Review Manager: Kelly MT, Gillies D.

Other statistical analysis not using RevMan: Kelly MT, Gillies D.

Writing the review: Kelly MT, Gillies D, Todd D.

Guarantor for the review (one author): Gillies D.

People responsible for reading and checking review before submission: Kelly MT, Gillies D.

Sources of support

Internal sources

  • The Children's Hospital at Westmead, Australia.

  • Sydney West Area Health Service, Australia.

External sources

  • No sources of support supplied

Declarations of interest

Donna Gillies: no conflict of interest.

David A Todd: no conflict of interest.

Jann P Foster: no conflict of interest.

Bisanth T Batuwitage: no conflict of interest.

Acknowledgements

We would like to thank Harald Herkner (content editor), Vibeke E Horstmann (statistical editor), Antonio M Esquinas (peer reviewer), Davide Chiumello (peer reviewer), Odie Geiger (consumer referee) for their help and editorial advice during the preparation of this updated systematic review.

We would like to thank and acknowledge the important role of Margaret Kelly and Catherine Lockwood as authors of the original review (Kelly 2010a). We would also like to thank and acknowledge Mariana Correia and Raul Carvalho for their assistance in translating and extracting data from Alcoforado 2012.

Version history

Published

Title

Stage

Authors

Version

2017 Sep 14

Heat and moisture exchangers versus heated humidifiers for mechanically ventilated adults and children

Review

Donna Gillies, David A Todd, Jann P Foster, Bisanth T Batuwitage

https://doi.org/10.1002/14651858.CD004711.pub3

2010 Apr 14

Heated humidification versus heat and moisture exchangers for ventilated adults and children

Review

Margaret Kelly, Donna Gillies, David A Todd, Catherine Lockwood

https://doi.org/10.1002/14651858.CD004711.pub2

2004 Jan 26

Heated humidification versus heat and moisture exchangers for ventilated adults and children

Protocol

Margaret Kelly, Donna Gillies, David A Todd, Catherine Lockwood

https://doi.org/10.1002/14651858.CD004711

Differences between protocol and review

We made the following changes to the published protocol (Kelly 2004)in the earlier version of the review (Kelly 2010a).

  • Moved mortality and pneumonia from secondary to primary outcomes.

  • In line with the new 'Risk of bias' table, added sequence generation to the assessed quality criteria.

  • There was significant heterogeneity between studies of people who had been ventilated for at least 48 hours compared to people ventilated for less than 48 hours. Therefore, a further analysis was conducted based on the types of HMEs, that is, whether they were hydrophobic or hygroscopic.

  • In the earlier version of the review (Kelly 2010a), we conducted the following subgroup analysis:

    • short‐term ventilation, defined as less than six hours;

    • medium‐term ventilation, defined as between six and 48 hours;

    • long‐term ventilation, defined as greater than 48 hours.

  • However, in this updated version of the review, the following additional changes were made:

  • The title was changed from "Heated humidification versus heat and moisture exchangers for mechanically ventilated adults and children" to "Heat and moisture exchangers versus heated humidifiers for mechanically ventilated adults and children." This was done because it was not clear in the original title that we were only including people who were undergoing invasive ventilation (though it was stated in the inclusion criteria). In addition, the order of heated humidification and heat and moisture exchangers was reversed because heat and moisture exchangers are treated as the intervention group in all analyses and therefore throughout the text.

We made the following changes to the published protocol (Kelly 2004), in the 2017 update:

  • Margaret Kelly and Catherine Lockwood, authors of the protocol and original review were no longer authors on this review update and there are two new authors, Jann P Foster and Bisanth T Batuwitage.

  • Incorporated a 'Summary of findings' table.

  • Modified the subgroup analysis for length of ventilation to the length of humidification, which was often, but not always, the same as the length of ventilation.

Keywords

MeSH

Medical Subject Headings Check Words

Adolescent; Adult; Child; Child, Preschool; Humans; Infant; Infant, Newborn; Young Adult;

PICOs

Population
Intervention
Comparison
Outcome

The PICO model is widely used and taught in evidence-based health care as a strategy for formulating questions and search strategies and for characterizing clinical studies or meta-analyses. PICO stands for four different potential components of a clinical question: Patient, Population or Problem; Intervention; Comparison; Outcome.

See more on using PICO in the Cochrane Handbook.

Study flow diagram.
Figures and Tables -
Figure 1

Study flow diagram.

Methodological quality graph: review authors' judgements about each methodological quality item presented as percentages across all included studies.
Figures and Tables -
Figure 2

Methodological quality graph: review authors' judgements about each methodological quality item presented as percentages across all included studies.

Methodological quality summary: review authors' judgements about each methodological quality item for each included study.
Figures and Tables -
Figure 3

Methodological quality summary: review authors' judgements about each methodological quality item for each included study.

Funnel plot of comparison: 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, outcome: 1.1 Artificial airway occlusion.
Figures and Tables -
Figure 4

Funnel plot of comparison: 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, outcome: 1.1 Artificial airway occlusion.

Funnel plot of comparison: 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, outcome: 1.2 Mortality.
Figures and Tables -
Figure 5

Funnel plot of comparison: 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, outcome: 1.2 Mortality.

Funnel plot of comparison: 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, outcome: 1.3 Pneumonia.
Figures and Tables -
Figure 6

Funnel plot of comparison: 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, outcome: 1.3 Pneumonia.

Comparison 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, Outcome 1 Artificial airway occlusion.
Figures and Tables -
Analysis 1.1

Comparison 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, Outcome 1 Artificial airway occlusion.

Comparison 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, Outcome 2 Mortality.
Figures and Tables -
Analysis 1.2

Comparison 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, Outcome 2 Mortality.

Comparison 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, Outcome 3 Pneumonia.
Figures and Tables -
Analysis 1.3

Comparison 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, Outcome 3 Pneumonia.

Comparison 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, Outcome 4 Atelectasis.
Figures and Tables -
Analysis 1.4

Comparison 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, Outcome 4 Atelectasis.

Comparison 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, Outcome 5 Tracheal aspirations (per day).
Figures and Tables -
Analysis 1.5

Comparison 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, Outcome 5 Tracheal aspirations (per day).

Comparison 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, Outcome 6 Saline instillations (number per day).
Figures and Tables -
Analysis 1.6

Comparison 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, Outcome 6 Saline instillations (number per day).

Comparison 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, Outcome 7 Change in body temperature (absolute data) (ºC).
Figures and Tables -
Analysis 1.7

Comparison 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, Outcome 7 Change in body temperature (absolute data) (ºC).

Comparison 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, Outcome 8 Change in body temperature mean data) (ºC).
Figures and Tables -
Analysis 1.8

Comparison 1 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies, Outcome 8 Change in body temperature mean data) (ºC).

Comparison 2 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ cross‐over studies, Outcome 1 PaO2 (mmHg).
Figures and Tables -
Analysis 2.1

Comparison 2 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ cross‐over studies, Outcome 1 PaO2 (mmHg).

Comparison 2 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ cross‐over studies, Outcome 2 PaCO2 (mmHg).
Figures and Tables -
Analysis 2.2

Comparison 2 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ cross‐over studies, Outcome 2 PaCO2 (mmHg).

Comparison 2 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ cross‐over studies, Outcome 3 Breathing rate (breaths/minute).
Figures and Tables -
Analysis 2.3

Comparison 2 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ cross‐over studies, Outcome 3 Breathing rate (breaths/minute).

Comparison 2 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ cross‐over studies, Outcome 4 Tidal volume (L).
Figures and Tables -
Analysis 2.4

Comparison 2 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ cross‐over studies, Outcome 4 Tidal volume (L).

Comparison 2 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ cross‐over studies, Outcome 5 Minute ventilation (L/minute).
Figures and Tables -
Analysis 2.5

Comparison 2 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ cross‐over studies, Outcome 5 Minute ventilation (L/minute).

Comparison 2 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ cross‐over studies, Outcome 6 Body temperature (ºC).
Figures and Tables -
Analysis 2.6

Comparison 2 Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ cross‐over studies, Outcome 6 Body temperature (ºC).

Comparison 3 Subgroup analysis ‐ children versus adults, Outcome 1 Artificial airway occlusion.
Figures and Tables -
Analysis 3.1

Comparison 3 Subgroup analysis ‐ children versus adults, Outcome 1 Artificial airway occlusion.

Comparison 3 Subgroup analysis ‐ children versus adults, Outcome 2 All‐cause mortality.
Figures and Tables -
Analysis 3.2

Comparison 3 Subgroup analysis ‐ children versus adults, Outcome 2 All‐cause mortality.

Comparison 4 Subgroup analysis ‐ length of ventilation, Outcome 1 Artificial airway occlusion.
Figures and Tables -
Analysis 4.1

Comparison 4 Subgroup analysis ‐ length of ventilation, Outcome 1 Artificial airway occlusion.

Comparison 4 Subgroup analysis ‐ length of ventilation, Outcome 2 All‐cause mortality.
Figures and Tables -
Analysis 4.2

Comparison 4 Subgroup analysis ‐ length of ventilation, Outcome 2 All‐cause mortality.

Comparison 4 Subgroup analysis ‐ length of ventilation, Outcome 3 Pneumonia.
Figures and Tables -
Analysis 4.3

Comparison 4 Subgroup analysis ‐ length of ventilation, Outcome 3 Pneumonia.

Comparison 5 Subgroup analysis ‐ hygroscopic versus hydrophobic heat and moisture exchanger (HME), Outcome 1 Artificial airway occlusion.
Figures and Tables -
Analysis 5.1

Comparison 5 Subgroup analysis ‐ hygroscopic versus hydrophobic heat and moisture exchanger (HME), Outcome 1 Artificial airway occlusion.

Comparison 5 Subgroup analysis ‐ hygroscopic versus hydrophobic heat and moisture exchanger (HME), Outcome 2 All‐cause mortality.
Figures and Tables -
Analysis 5.2

Comparison 5 Subgroup analysis ‐ hygroscopic versus hydrophobic heat and moisture exchanger (HME), Outcome 2 All‐cause mortality.

Comparison 5 Subgroup analysis ‐ hygroscopic versus hydrophobic heat and moisture exchanger (HME), Outcome 3 Pneumonia.
Figures and Tables -
Analysis 5.3

Comparison 5 Subgroup analysis ‐ hygroscopic versus hydrophobic heat and moisture exchanger (HME), Outcome 3 Pneumonia.

Comparison 6 Heat and moisture exchanger (HME) with and without filters, Outcome 1 Artificial airway occlusion.
Figures and Tables -
Analysis 6.1

Comparison 6 Heat and moisture exchanger (HME) with and without filters, Outcome 1 Artificial airway occlusion.

Comparison 6 Heat and moisture exchanger (HME) with and without filters, Outcome 2 All‐cause mortality.
Figures and Tables -
Analysis 6.2

Comparison 6 Heat and moisture exchanger (HME) with and without filters, Outcome 2 All‐cause mortality.

Comparison 6 Heat and moisture exchanger (HME) with and without filters, Outcome 3 Pneumonia.
Figures and Tables -
Analysis 6.3

Comparison 6 Heat and moisture exchanger (HME) with and without filters, Outcome 3 Pneumonia.

Comparison 7 Sensitivity analyses ‐ selection bias, Outcome 1 Mortality.
Figures and Tables -
Analysis 7.1

Comparison 7 Sensitivity analyses ‐ selection bias, Outcome 1 Mortality.

Comparison 7 Sensitivity analyses ‐ selection bias, Outcome 2 Pneumonia.
Figures and Tables -
Analysis 7.2

Comparison 7 Sensitivity analyses ‐ selection bias, Outcome 2 Pneumonia.

Comparison 8 Sensitivity analyses ‐ detection bias, Outcome 1 Artificial airway occlusion.
Figures and Tables -
Analysis 8.1

Comparison 8 Sensitivity analyses ‐ detection bias, Outcome 1 Artificial airway occlusion.

Comparison 8 Sensitivity analyses ‐ detection bias, Outcome 2 Pneumonia.
Figures and Tables -
Analysis 8.2

Comparison 8 Sensitivity analyses ‐ detection bias, Outcome 2 Pneumonia.

Summary of findings for the main comparison. Heat and moisture exchangers (HME) compared to heated humidifiers (HH) for ventilated adults and children

Heat and moisture exchangers (HME) compared to heated humidifiers (HH) for ventilated adults and children

Patient or population: ventilated adults (18 trials) and children (1 trial)

Settings: ICUs (17), NICU (1), and hospitals (1) in France (7), USA (3), Australia (2), Brazil (2), Denmark (1), Italy (1), Saudi Arabia (1), Spain (1), Switzerland (1)

Intervention: HME

Comparison: HH

Outcomes

Illustrative comparative risks* (95% CI)

Relative effect
(95% CI)

No of participants
(studies)

Quality of the evidence
(GRADE)

Comments

Assumed risk

Corresponding risk

HH

HME

Artificial airway occlusion

(measured over 3‐15 days (median 4 days))

23 per 1000

37 per 1000

RR 1.59
(0.6 to 4.19)

2171
(15 studies)

⊕⊕⊝⊝ 1

L ow

Allocation and blinding unclear in 13 studies; moderate heterogeneity.

Mortality ‐ all cause

(Measured over 3‐15 days (median 8 days))

247 per 1000

257 per 1000

RR 1.03
(0.89 to 1.20)

1951
(12 studies)

⊕⊕⊝⊝ 2

L ow

Allocation and blinding unclear in 9 and 11 studies; low heterogeneity.

Pneumonia

(Measured over 4‐21 days (median 4 days))

32 per 1000

30 per 1000

RR 0.93
(0.73 to 1.19)

2251
(13 studies)

⊕⊕⊝⊝ 3

L ow

Allocation and blinding unclear in more than half of studies; moderate heterogeneity though this was due to only 1 study.

*The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. 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: 95% confidence interval; HH: heated humidification; HME: heat and moisture exchanger; ICU: intensive care unit; NICU: neonatal intensive care unit; RR: risk 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.

The assumed and corresponding risks were calculated from data in included trials.

1 Quality downgraded two levels for serious indirectness because participants may not have been considered suitable for HME in three studies and could be taken out of the HME group in three studies.

2 Quality downgraded two levels for serious indirectness because participants may not have been considered suitable for HME in two studies and could be taken out of the HME group in three studies.

3 Quality downgraded two levels for serious indirectness because participants may not have been considered suitable for HME in two studies and could be taken out of the HME group in three studies.

Figures and Tables -
Summary of findings for the main comparison. Heat and moisture exchangers (HME) compared to heated humidifiers (HH) for ventilated adults and children
Table 1. Length of stay ‐ intensive care unit (mean days)

Study

HH

HME

No of participants

Boots 2006

9

7

381

Diaz 2002

4

4

43

Hurni 1997

13.80

11.10

104

Kollef 1998

5.30

5.70

310

Lacherade 2005

25.3

21.4

369

Roustan 1992

9.30

13.90

116

HH: heated humidification; HME: heat and moisture exchangers.

Figures and Tables -
Table 1. Length of stay ‐ intensive care unit (mean days)
Table 2. Length of stay ‐ hospital (mean days)

Study

HH

HME

No of participants

Diaz 2002

11

10

43

Kollef 1998

16.50

16.50

310

HH: heated humidification; HME: heat and moisture exchangers.

Figures and Tables -
Table 2. Length of stay ‐ hospital (mean days)
Table 3. Cost

Study

HME

HH

Units

Participants

Boots 1997

6.72

8.20

AUD/day

83

Boots 2006

8.62

9.27

AUD/day

381

Branson 1996

4.70

8.97

USD/day

99

Dreyfuss 1995

5.00

11.00

USD/day (France)

131

Kirton 1997

17.46

27.80

USD/participant

280

Kollef 1998

15.98

38.26

USD/participant

310

HH: heated humidification; HME: heat and moisture exchangers.

Figures and Tables -
Table 3. Cost
Table 4. Work of breathing (joules/minute ‐ mean)

Study

HH

HME

Participants

Girault 2003

9.86

16.50

11

Iotti 1997

13.6

20.8

10

HH: heated humidification; HME: heat and moisture exchangers.

Figures and Tables -
Table 4. Work of breathing (joules/minute ‐ mean)
Comparison 1. Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Artificial airway occlusion Show forest plot

15

2171

Risk Ratio (M‐H, Random, 95% CI)

1.59 [0.60, 4.19]

2 Mortality Show forest plot

12

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

2.1 All cause

12

1951

Risk Ratio (M‐H, Random, 95% CI)

1.03 [0.89, 1.20]

2.2 Pneumonia‐related

3

484

Risk Ratio (M‐H, Random, 95% CI)

1.09 [0.39, 3.01]

3 Pneumonia Show forest plot

13

2251

Risk Ratio (M‐H, Random, 95% CI)

0.93 [0.73, 1.19]

3.1 Throughout ventilation

7

1090

Risk Ratio (M‐H, Random, 95% CI)

0.94 [0.69, 1.27]

3.2 ≥ 48 hours after ventilation

6

1161

Risk Ratio (M‐H, Random, 95% CI)

0.96 [0.64, 1.46]

4 Atelectasis Show forest plot

3

303

Risk Ratio (M‐H, Random, 95% CI)

0.85 [0.52, 1.40]

5 Tracheal aspirations (per day) Show forest plot

3

290

Mean Difference (IV, Random, 95% CI)

‐0.47 [‐1.41, 0.47]

6 Saline instillations (number per day) Show forest plot

3

276

Std. Mean Difference (IV, Random, 95% CI)

‐0.40 [‐0.64, ‐0.17]

7 Change in body temperature (absolute data) (ºC) Show forest plot

6

321

Mean Difference (IV, Random, 95% CI)

‐0.49 [‐0.96, ‐0.02]

8 Change in body temperature mean data) (ºC) Show forest plot

3

78

Mean Difference (IV, Random, 95% CI)

‐0.59 [‐0.82, ‐0.36]

Figures and Tables -
Comparison 1. Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ parallel studies
Comparison 2. Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ cross‐over studies

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 PaO2 (mmHg) Show forest plot

4

Mean Difference (Random, 95% CI)

Subtotals only

1.1 r = 0.3

4

Mean Difference (Random, 95% CI)

‐3.24 [‐16.08, 9.60]

1.2 r = 0.5

4

Mean Difference (Random, 95% CI)

‐3.87 [‐16.73, 9.00]

1.3 r = 0.7

4

Mean Difference (Random, 95% CI)

‐4.41 [‐17.09, 8.27]

2 PaCO2 (mmHg) Show forest plot

5

Mean Difference (Random, 95% CI)

Subtotals only

2.1 r = 0.3

5

Mean Difference (Random, 95% CI)

1.93 [0.27, 3.59]

2.2 r = 0.5

5

Mean Difference (Random, 95% CI)

2.02 [0.19, 3.85]

2.3 r = 0.7

5

Mean Difference (Random, 95% CI)

2.21 [0.33, 4.09]

3 Breathing rate (breaths/minute) Show forest plot

4

Mean Difference (Random, 95% CI)

Subtotals only

3.1 r = 0.3

4

Mean Difference (Random, 95% CI)

1.40 [0.33, 2.46]

3.2 r = 0.5

4

Mean Difference (Random, 95% CI)

1.15 [‐0.13, 2.44]

3.3 r = 0.7

4

Mean Difference (Random, 95% CI)

1.02 [‐0.38, 2.41]

4 Tidal volume (L) Show forest plot

5

Mean difference (Random, 95% CI)

Subtotals only

4.1 r = 0.3

5

Mean difference (Random, 95% CI)

0.02 [‐0.00, 0.03]

4.2 r = 0.5

5

Mean difference (Random, 95% CI)

0.02 [0.00, 0.04]

4.3 r = 0.7

5

Mean difference (Random, 95% CI)

0.03 [0.01, 0.06]

5 Minute ventilation (L/minute) Show forest plot

5

Mean difference (Random, 95% CI)

Subtotals only

5.1 r = 0.3

5

Mean difference (Random, 95% CI)

1.20 [0.78, 1.61]

5.2 r = 0.5

5

Mean difference (Random, 95% CI)

1.19 [0.63, 1.75]

5.3 r = 0.7

5

Mean difference (Random, 95% CI)

1.18 [0.55, 1.80]

6 Body temperature (ºC) Show forest plot

2

Mean Difference (Random, 95% CI)

Subtotals only

6.1 r = 0.3

2

Mean Difference (Random, 95% CI)

‐1.12 [‐3.77, 1.52]

6.2 r = 0.5

2

Mean Difference (Random, 95% CI)

‐1.13 [‐3.77, 1.52]

6.3 r = 0.7

2

Mean Difference (Random, 95% CI)

‐1.13 [‐3.78, 1.51]

Figures and Tables -
Comparison 2. Heat and moisture exchanger (HME) versus heat humidifier (HH) ‐ cross‐over studies
Comparison 3. Subgroup analysis ‐ children versus adults

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Artificial airway occlusion Show forest plot

15

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

1.1 Children

1

56

Risk Ratio (M‐H, Random, 95% CI)

0.64 [0.33, 1.26]

1.2 Adults

14

2115

Risk Ratio (M‐H, Random, 95% CI)

1.94 [0.65, 5.76]

2 All‐cause mortality Show forest plot

12

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

2.1 Children

1

56

Risk Ratio (M‐H, Random, 95% CI)

2.79 [0.62, 12.67]

2.2 Adults

11

1895

Risk Ratio (M‐H, Random, 95% CI)

1.02 [0.88, 1.19]

Figures and Tables -
Comparison 3. Subgroup analysis ‐ children versus adults
Comparison 4. Subgroup analysis ‐ length of ventilation

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Artificial airway occlusion Show forest plot

15

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

1.1 Medium‐term

8

1031

Risk Ratio (M‐H, Random, 95% CI)

1.74 [0.41, 7.30]

1.2 Long‐term

7

1140

Risk Ratio (M‐H, Random, 95% CI)

1.47 [0.34, 6.36]

2 All‐cause mortality Show forest plot

11

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

2.1 Medium‐term

5

860

Risk Ratio (M‐H, Random, 95% CI)

1.01 [0.78, 1.31]

2.2 Long‐term

6

1048

Risk Ratio (M‐H, Random, 95% CI)

1.03 [0.85, 1.25]

3 Pneumonia Show forest plot

11

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

3.1 Medium‐term

5

892

Risk Ratio (M‐H, Random, 95% CI)

1.06 [0.77, 1.47]

3.2 Long‐term

6

1036

Risk Ratio (M‐H, Random, 95% CI)

0.91 [0.59, 1.43]

Figures and Tables -
Comparison 4. Subgroup analysis ‐ length of ventilation
Comparison 5. Subgroup analysis ‐ hygroscopic versus hydrophobic heat and moisture exchanger (HME)

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Artificial airway occlusion Show forest plot

15

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

1.1 Hydrophobic

5

540

Risk Ratio (M‐H, Random, 95% CI)

2.86 [0.65, 12.62]

1.2 Hygroscopic

11

1638

Risk Ratio (M‐H, Random, 95% CI)

0.89 [0.32, 2.48]

2 All‐cause mortality Show forest plot

11

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

2.1 Hydrophobic

2

189

Risk Ratio (M‐H, Random, 95% CI)

0.79 [0.46, 1.35]

2.2 Hygroscopic

9

1719

Risk Ratio (M‐H, Random, 95% CI)

1.05 [0.89, 1.23]

3 Pneumonia Show forest plot

12

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

3.1 Hydrophobic

3

469

Risk Ratio (M‐H, Random, 95% CI)

0.48 [0.28, 0.82]

3.2 Hygroscopic

9

1678

Risk Ratio (M‐H, Random, 95% CI)

0.95 [0.77, 1.17]

Figures and Tables -
Comparison 5. Subgroup analysis ‐ hygroscopic versus hydrophobic heat and moisture exchanger (HME)
Comparison 6. Heat and moisture exchanger (HME) with and without filters

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Artificial airway occlusion Show forest plot

15

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

1.1 With filter

8

1203

Risk Ratio (M‐H, Random, 95% CI)

1.25 [0.41, 3.80]

1.2 No filter

7

968

Risk Ratio (M‐H, Random, 95% CI)

2.46 [0.33, 18.47]

2 All‐cause mortality Show forest plot

12

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

2.1 With filter

5

1080

Risk Ratio (M‐H, Random, 95% CI)

1.00 [0.82, 1.22]

2.2 No filter

7

871

Risk Ratio (M‐H, Random, 95% CI)

1.08 [0.85, 1.36]

3 Pneumonia Show forest plot

13

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

3.1 With filter

5

979

Risk Ratio (M‐H, Random, 95% CI)

0.97 [0.76, 1.24]

3.2 no filter

8

1272

Risk Ratio (M‐H, Random, 95% CI)

0.88 [0.55, 1.38]

Figures and Tables -
Comparison 6. Heat and moisture exchanger (HME) with and without filters
Comparison 7. Sensitivity analyses ‐ selection bias

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Mortality Show forest plot

12

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

1.1 Low risk of bias

2

286

Risk Ratio (M‐H, Random, 95% CI)

1.31 [0.91, 1.90]

1.2 Unknown risk of bias

10

1665

Risk Ratio (M‐H, Random, 95% CI)

0.98 [0.83, 1.16]

2 Pneumonia Show forest plot

13

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

2.1 Low risk of bias

3

566

Risk Ratio (M‐H, Random, 95% CI)

0.72 [0.41, 1.28]

2.2 Unknown risk of bias

9

1582

Risk Ratio (M‐H, Random, 95% CI)

1.01 [0.77, 1.33]

2.3 High risk of bias

1

103

Risk Ratio (M‐H, Random, 95% CI)

1.10 [0.23, 5.21]

Figures and Tables -
Comparison 7. Sensitivity analyses ‐ selection bias
Comparison 8. Sensitivity analyses ‐ detection bias

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Artificial airway occlusion Show forest plot

15

2171

Risk Ratio (M‐H, Random, 95% CI)

1.59 [0.60, 4.19]

1.1 Low risk of bias

2

590

Risk Ratio (M‐H, Random, 95% CI)

0.14 [0.01, 2.74]

1.2 Unclear risk of bias

13

1581

Risk Ratio (M‐H, Random, 95% CI)

1.92 [0.69, 5.34]

2 Pneumonia Show forest plot

12

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

2.1 Low risk of bias

4

648

Risk Ratio (M‐H, Random, 95% CI)

0.84 [0.52, 1.36]

2.2 Unknown risk of bias

8

1500

Risk Ratio (M‐H, Random, 95% CI)

0.97 [0.70, 1.33]

Figures and Tables -
Comparison 8. Sensitivity analyses ‐ detection bias