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Associations of a positive intra-operative air-test with postoperative pulmonary complications in general surgery
Liselotte Hol1, Tom D Vermeulen, Rozemarijn S de Kruijk
1From the Department of Anaesthesiology & The Department of Intensive Care, Amsterdam UMC, AMC, Amsterdam, The Netherlands (LH, TDV, RSdeK, AT, GRMK, JSB, DMPvM, MWH, MJS), Mahidol-Oxford Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand (MJS), The Nuffield Department of Medicine, University of Oxford, Oxford, UK (MJS), The Department of Anaesthesiology, General Intensive Care and Pain Medicine, Division of Cardiac Thoracic Vascular Anaesthesia and Intensive Care Medicine, Medical University Vienna, Vienna, Austria (MJS).
Background:
The air-test, which involves reducing the fraction of inspiratory oxygen (FiO 2 ) to 21% and monitoring pulse oximetry haemoglobin saturation (SpO 2 ), has previously been used to guide intra-operative ventilation strategies. However, it is unclear how often the air-test is positive (defined as an SpO 2 decrease below 97% during ventilation with an FiO 2 of 21%) in general surgery patients, and if a positive air-test is associated with the development of postoperative pulmonary complications (PPCs).
Objectives:
To assess the incidence of a positive air-test in general surgery patients, and to determine the association of a positive air-test with development and severity of PPCs.
Design:
An observational study.
Setting:
Single-centre study performed in the Amsterdam University Medical Centre, the Netherlands.
Patients:
Adult patients undergoing intra-operative ventilation during general anaesthesia for general surgery.
Main Outcome Measure:
The primary endpoint is a previously used composite of PPCs.
Results:
Out of 632 patients, 328 (52%) had a positive air-test. Patients with a positive air-test were older, had a higher BMI, were more often smokers and were more often diagnosed with chronic obstructive pulmonary disease. Patients with a positive air-test were ventilated with a higher PEEP and FiO 2 and they developed PPCs more often (18.6 vs. 12.5%; P = 0.038). The air-test had a sensitivity of 62% and a specificity of 50% for predicting PPCs. The PPV was 19% and the NPV was 88%.
Conclusion:
The intra-operative air-test is often positive in general surgery patients and is associated with a higher incidence of PPCs. Given the high NPV, the air-test is mainly useful in identifying patients at a low risk of PPCs.
Trial Registration:
NCT05345743.
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