Capnodynamic end‐expiratory lung volume assessment in anesthetized healthy children

Abstract

AbstractBackgroundCapnodynamic lung function monitoring generates variables that may be useful for pediatric perioperative ventilation.AimsEstablish normal values for end‐expiratory lung volume CO2 in healthy children undergoing anesthesia and to compare these values to previously published values obtained with alternative end‐expiratory lung volume methods. The secondary aim was to investigate the ability of end‐expiratory lung volume CO2 to react to positive end‐expiratory pressure‐induced changes in end‐expiratory lung volume. In addition, normal values for associated volumetric capnography lung function variables were examined.MethodsFifteen pediatric patients with healthy lungs (median age 8 months, range 1–36 months) undergoing general anesthesia were examined before start of surgery. Tested variables were recorded at baseline positive end‐expiratory pressure 3 cmH2O, 1 and 3 min after positive end‐expiratory pressure 10 cmH2O and 3 min after returning to baseline positive end‐expiratory pressure 3 cmH2O.ResultsBaseline end‐expiratory lung volume CO2 was 32 mL kg−1 (95% CI 29–34 mL kg−1) which increased to 39 mL kg−1 (95% CI 35–43 mL kg−1, p < .0001) and 37 mL kg−1 (95% CI 34–41 mL kg−1, p = .0003) 1 and 3 min after positive end‐expiratory pressure 10 cmH2O, respectively. End‐expiratory lung volume CO2 returned to baseline, 33 mL kg−1 (95% CI 29–37 mL kg−1, p = .72) 3 min after re‐establishing positive end‐expiratory pressure 3 cmH2O. Airway dead space increased from 1.1 mL kg−1 (95% CI 0.9–1.4 mL kg−1) to 1.4 (95% CI 1.1–1.8 mL kg−1, p = .003) and 1.5 (95% CI 1.1–1.8 mL kg−1, p < .0001) 1 and 3 min after positive end‐expiratory pressure 10 cmH2O, respectively, and 1.2 mL kg−1 (95% CI 0.9–1.4 mL kg−1, p = .08) after 3 min of positive end‐expiratory pressure 3 cmH2O. Additional volumetric capnography and lung function variables showed no major changes in response to positive end‐expiratory pressure variations.ConclusionsCapnodynamic noninvasive and continuous end‐expiratory lung volume CO2 values assessed during anesthesia in children were in close agreement with previously reported end‐expiratory lung volume values generated by alternative methods. Furthermore, positive end‐expiratory pressure changes resulted in physiologically expected end‐expiratory lung volume CO2 responses in a timely manner, suggesting that it can be used to trend end‐expiratory lung volume changes during anesthesia.