Effect of Low-Flow versus Conventional-Flow Inhalational Anaesthesia on Pulmonary and Oxygenation Outcomes in Adult Surgical Patients
A Systematic Review and Meta-Analysis of Randomised Controlled Trials
DOI:
https://doi.org/10.25751/rspa.49390Keywords:
Anesthesia, General, Anesthetics, Inhalation, Respiratory Function Tests, Oxygenation, Postoperative ComplicationsAbstract
Introduction: Low-flow inhalational anaesthesia reduces volatile anaesthetic consumption, cost, and environmental emissions, but its effects on postoperative pulmonary function and oxygenation remain uncertain.
We aimed to evaluate the effect of low-flow compared with conventional- or high-flow inhalational anaesthesia on pulmonary and oxygenation outcomes in adult surgical patients.
Methods: A systematic review and meta-analysis of randomised controlled trials was performed. Eligible studies included adult surgical patients undergoing general anaesthesia and compared low-flow or minimal-flow inhalational anaesthesia with conventional-, medium-, or high-flow techniques. Primary outcomes were postoperative pulmonary function parameters, particularly FEV₁ and FVC. Secondary outcomes included SpO₂, PaO₂, ORI, respiratory mechanics, and postoperative pulmonary complications. Mean differences with 95% confidence intervals were pooled when outcomes were sufficiently comparable. Risk of bias was assessed using the Cochrane RoB 2 tool, and certainty of evidence was evaluated using GRADE.
Results: Nine randomised controlled trials were included. Two studies provided sufficient data for meta-analysis of postoperative spirometric outcomes at 24 hours. There was no statistically significant difference between low-flow and high-flow anaesthesia in FEV₁ at 24 hours (MD 0.18 L, 95% CI −0.09 to 0.44; p = 0.19; I² = 24%) or FVC at 24 hours (MD 0.19 L, 95% CI −0.19 to 0.58; p = 0.32; I² = 54%). Seven studies were narratively synthesised because of heterogeneity in outcome definitions, instruments, and timing. Across these studies, no consistent clinically important differences were observed in SpO₂, PaO₂, ORI, or respiratory mechanics. No study formally reported postoperative pulmonary complications as a predefined outcome. Certainty of evidence was very low for FEV₁ and FVC and low to very low for other outcomes.
Conclusion: Low-flow inhalational anaesthesia appears comparable to conventional- or high-flow anaesthesia for short-term postoperative pulmonary function and oxygenation outcomes in adult surgical patients. However, certainty of evidence is low to very low because of small sample sizes and heterogeneous outcome reporting. Larger standardised trials are needed to evaluate clinically meaningful postoperative pulmonary complications.
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Copyright (c) 2026 Carlos Neto, Emre Adalier, Ines Shopi, Ana Luiza Alves de Castilho, Alina Akural, Ingridy Sodre da Costa Bonfim, Jacopo Bagnoli, Nicola Khoury , Nur Barlas
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