The accuracy of postoperative, non-invasive Air-Test to diagnose atelectasis in healthy patients after surgery: a prospective, diagnostic pilot study

• Published in: BMJ open 2017-05, Vol.7 (5), p.e015560-e015560
• Main Authors: Ferrando, Carlos, Romero, Carolina, Tusman, Gerardo, Suarez-Sipmann, Fernando, Canet, Jaume, Dosdá, Rosa, Valls, Paola, Villena, Abigail, Serralta, Ferran, Jurado, Ana, Carrizo, Juan, Navarro, Jose, Parrilla, Cristina, Romero, Jose E, Pozo, Natividad, Soro, Marina, Villar, Jesús, Belda, Francisco Javier
• Format: Article
• Language: English
• Subjects: Abdomen; Abdominal surgery; Accuracy; Adult; Aged; Air - analysis; Anaesthesia; Anesthesia; Anesthesia, General - adverse effects; Anesthesiology; Blood Gas Analysis; Clinical trials; False Negative Reactions; Female; General anesthesia; Hemoglobin; Humans; Intensive care; Linear Models; Male; Medical diagnosis; Medical imaging; Middle Aged; Oximetry; Oxygen Inhalation Therapy; Oxygen saturation; Oxygen therapy; Patients; Pilot Projects; Postoperative Complications - diagnosis; Postoperative Complications - etiology; Postoperative Complications - therapy; Postoperative period; Prospective Studies; Pulmonary Atelectasis - diagnosis; Pulmonary Atelectasis - etiology; Pulmonary Atelectasis - therapy; Pulse oximetry; Respiratory therapy; Sensitivity and Specificity; Spain; Surgery; Tertiary Care Centers; Tomography, X-Ray Computed; Ventilators
• ISSN: 2044-6055; 2044-6055
• DOI: 10.1136/bmjopen-2016-015560

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.