Physiological effects of Heated Humidifiers versus Heat and Moisture Exchangers in Adult ARDS Patients Receiving...

In acute respiratory distress syndrome (ARDS), increased dead space with Heat and moisture exchangers (HMEs) may impair carbon dioxide elimination during lung-protective ventilation. To assess its impact, we conducted a systematic review and meta-analysis.

After registration with the International Prospective Register of Systematic Reviews (CRD420261368917), PubMed, EMBASE, and Scopus were searched for studies of ARDS patients receiving IMV comparing HHs and HMEs. Random-effects meta-analyses of paired physiological outcomes were conducted using inverse-variance models, and standardised mean change (SMCs) with 95% confidence intervals (CIs) were calculated. Risk of bias was assessed using ROBINS-I or the NIH Before-After Quality Assessment Tool, as appropriate.

Ten studies were included in the systematic review; quantitative synthesis included paired physiological studies evaluating PaO₂ (4 studies), PaCO₂ (5 studies), pH (4 studies), and physiological dead-space fraction (2 studies). Compared with HMEs, HHs significantly reduced PaCO₂ (SMC -0.76, 95% CI -1.03 to -0.49; p<0.001; I²=0) and increased arterial pH (SMC 0.66, 95% CI 0.38-0.95; p<0.001; I²=0%). No significant differences were observed for PaO₂ (SMC -0.00, 95% CI -0.26 to 0.25; p=0.98; I²=0%) or physiological dead-space fraction (SMC -0.45, 95% CI -0.98 to 0.08; p=0.09; I²=43%). No eligible comparative data were available for the prespecified primary outcome of artificial airway occlusion or other patient-centered clinical outcomes.

Compared with HMEs, HHs were associated with lower PaCO₂ and higher arterial pH, without a significant difference in PaO₂. However, no comparative evidence was available for the prespecified primary outcome of artificial airway obstruction, and evidence regarding patient-centered clinical outcomes remains insufficient."