Feasibility and efficacy of lung ultrasound to investigate pulmonary complications in patients who developed postoperative Hypoxaemia-a prospective study

Abstract

Background: Postoperative pulmonary complications (PPCs) and hypoxaemia are associated with morbidity and mortality. We aimed to evaluate the feasibility and efficacy of lung ultrasound (LUS) to diagnose PPCs in patients suffering from hypoxaemia after general anaesthesia and compare the results to those of thoracic computed tomography (CT).

Methods: Adult patients who received general anaesthesia and suffered from hypoxaemia in the postanaesthesia care unit (PACU) were analysed. Hypoxaemia was defined as an oxygen saturation measured by pulse oximetry (SPO₂) less than 92% for more than 30 s under ambient air conditions. LUS was performed by two trained anaesthesiologists once hypoxaemia occurred. After LUS examination, each patient was transported to the radiology department for thoracic CT scan within 1 h before returning to the ward.

Results: From January 2019 to May 2019, 113 patients (61 men) undergoing abdominal surgery (45 patients, 39.8%), video-assisted thoracic surgery (31 patients, 27.4%), major orthopaedic surgery (17 patients, 15.0%), neurosurgery (10 patients, 8.8%) or other surgery (10 patients, 8.8%) were included. CT diagnosed 327 of 1356 lung zones as atelectasis, while LUS revealed atelectasis in 311 of the CT-confirmed zones. Pneumothorax was detected by CT scan in 75 quadrants, 72 of which were detected by LUS. Pleural effusion was diagnosed in 144 zones on CT scan, and LUS detected 131 of these zones. LUS was reliable in diagnosing atelectasis (sensitivity 98.0%, specificity 96.7% and diagnostic accuracy 97.2%), pneumothorax (sensitivity 90.0%, specificity 98.9% and diagnostic accuracy 96.7%) and pleural effusion (sensitivity 92.9%, specificity 96.0% and diagnostic accuracy 95.1%).

Conclusions: Lung ultrasound is feasible, efficient and accurate in diagnosing different aetiologies of postoperative hypoxia in healthy-weight patients in the PACU.

Trial registration: Current Controlled Trials NCT03802175 , 2018/12/05, www.ClinicalTrials.gov.

Keywords: Atelectasis; Lung ultrasound; Pleural effusion; Pneumothorax; Thoracic computed tomography.

Fig. 1

Hemithorax partition during lung ultrasound examination. a, b Each hemithorax was divided into 6 quadrants by anterior and posterior axillary lines. Abbreviations: AAL, anterior axillary line; PAL, posterior axillary line

Fig. 2

Lung ultrasound signs with different scores. a score 0, healthy lung, equidistant A-lines parallel to the sliding pleura; b score 1, moderate aeration loss, no fewer than 3 dispersive B lines originated from the pleura; c score 2, serious aeration loss, presence of coalescent B lines with irregular pleura; d, score 3, absolute aeration loss, subpleural consolidation

Fig. 3

Flowchart of patient recruitment. Abbreviations: LUS, lung ultrasound; CT, computed tomography

Fig. 4

Typical pulmonary pathologies on both LUS and thoracic CT in the same regions. (a1) Typical LUS signs of atelectasis in the dorsal quadrant of the lung presented as tissue-like patterns (left, white arrow), (a2) CT signs of corresponding regions presented as a crescent shape (right, white arrow) (b1) Typical LUS on M-mode of pneumothorax in the anterior quadrant of the lung presented as a bar code sign, (b1) CT signs of corresponding regions presented as very-low-density gas window (right, white arrow). (c1) Typical LUS of pleural effusion in the dorsal quadrant of the lung presented as anechoic area (left, white arrow), (c2) CT signs of corresponding regions presented as a half-moon (right, white arrow). Abbreviations: LUS, lung ultrasound; CT, computed tomography.