• Carlos Ferrando, Carolina Romero, Gerardo Tusman, Fernando Suarez-Sipmann, Jaume Canet, Rosa Dosdá, Paola Valls, Abigail Villena, Ferran Serralta, Ana Jurado, Juan Carrizo, Jose Navarro, Cristina Parrilla, Jose E Romero, Natividad Pozo, Marina Soro, Jesús Villar, and Francisco Javier Belda.
• Anesthesiology and Critical Care, Hospital Clínico Universitario Valencia, Valencia, Spain.
• BMJ Open. 2017 May 29; 7 (5): e015560.

ObjectiveTo assess the diagnostic accuracy of peripheral capillary oxygen saturation (SpO2) while breathing room air for 5 min (the 'Air-Test') in detecting postoperative atelectasis.DesignProspective cohort study. Diagnostic accuracy was assessed by measuring the agreement between the index test and the reference standard CT scan images.SettingPostanaesthetic care unit in a tertiary hospital in Spain.ParticipantsThree hundred and fifty patients from 12 January to 7 February 2015; 170 patients scheduled for surgery under general anaesthesia who were admitted into the postsurgical unit were included.InterventionThe Air-Test was performed in conscious extubated patients after a 30 min stabilisation period during which they received supplemental oxygen therapy via a venturi mask. The Air-Test was defined as positive when SpO2 was ≤96% and negative when SpO2 was ≥97%. Arterial blood gases were measured in all patients at the end of the Air-Test. In the subsequent 25 min, the presence of atelectasis was evaluated by performing a CT scan in 59 randomly selected patients.Main Outcome MeasuresThe primary study outcome was assessment of the accuracy of the Air-Test for detecting postoperative atelectasis compared with the reference standard. The secondary outcome was the incidence of positive Air-Test results.ResultsThe Air-Test diagnosed postoperative atelectasis with an area under the receiver operating characteristic curve of 0.90 (95% CI 0.82 to 0.98) with a sensitivity of 82.6% and a specificity of 87.8%. The presence of atelectasis was confirmed by CT scans in all patients (30/30) with positive and in 5 patients (17%) with negative Air-Test results. Based on the Air-Test, postoperative atelectasis was present in 36% of the patients (62 out of 170).ConclusionThe Air-Test may represent an accurate, simple, inexpensive and non-invasive method for diagnosing postoperative atelectasis.Trial RegistrationNCT02650037.© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

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