Effect of inspired gas temperature on lung mechanics and gas exchange in neonates in normothermia or therapeutic hypothermia.
prospective_cohort · Level II
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- Record sourced from PubMed, PMID 33895234.
- Also identified by DOI 10.1016/j.resuscitation.2021.04.015.
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Abstract
Respiratory critical care guidelines suggest heating the air/oxygen mixture but do not recommend a specific temperature target. We aimed to clarify if the inspired gas temperature influences lung mechanics and gas exchange in intubated patients treated with whole body hypothermia (WBH) or normothermia (NT). Prospective cohort study enrolling neonates ventilated for perinatal asphyxia resuscitation (no lung disease) or acute hypoxemic respiratory failure. Patients were divided between those ventilated in NT or WBH. Compliance (C<sub>dyn</sub>), airway resistances (R<sub>aw</sub>), oxygenation index (OI), PaO<sub>2</sub>/FiO<sub>2</sub>, A-a gradient, a/A ratio, estimated alveolar dead space (VD<sub>alv</sub>), ventilatory index (VI) and CO<sub>2</sub> production (VCO<sub>2</sub>) were registered at the study beginning (inspired gas at 37°C). Then, gas temperature was decreased (32 °C) and variables were recorded again after 1 and 3 h. Data were analysed with univariate and multivariate repeated measures-ANOVA. C<sub>dyn</sub>, R<sub>aw</sub>, OI, PaO<sub>2</sub>/FiO<sub>2</sub>, A-a gradient, a/A ratio, VD<sub>alv</sub>, VI and V<sub>CO2</sub> are similar between WBH and NT at any timepoint (between-subjects effect); these results do not change adjusting for the presence of respiratory failure. When this is considered in multivariate ANOVA (within-subjects effect), C<sub>dyn</sub> (p = 0.016), R<sub>aw</sub> (p = 0.034) and VD<sub>alv</sub> (p < 0.001) were worse in patients with respiratory failure than in those without lung disease. Decreasing the gas temperature from 37 °C to 32 °C for 3 h does not change lung mechanics and gas exchange, neither in neonates with, nor in those without respiratory failure and in those treated in NT or WBH. These findings fill a knowledge gap regarding the effect of inspired gas temperature during WBH: they may inform future respiratory critical care guidelines.