From January to May 2019, 138 adult patients were evaluated for eligibility. Twenty-five patients (breast operation, haemodynamic instability, etc.) were excluded, and 113 patients were ultimately enrolled (Figure 3). During the study, all the LUS examinations and CT scans were performed successfully, and a total of 1356 pairs of ultrasound cine-loops and CT images were stored for all patients. Table 1 summarizes the demographic data of the enrolled patients.
Flowchart of patient recruitment. Abbreviations: LUS, lung ultrasound; CT, computed tomography
Postoperative hypoxaemia in the PACU mainly occurred in patients after abdominal surgery (45 patients, 39.8%) and VATS (31 patients, 27.4%), followed by major orthopaedic surgery (17 patients, 15.0%), neurosurgery (10 patients, 8.8%) and other types of surgery (10 patients, 8.8%). Eighty-two patients (72.6%) were diagnosed with atelectasis by both CT and LUS. CT scan diagnosed 327 of 1356 quadrants as atelectasis, while LUS revealed the same diagnosis in 311 of the 327 CT-diagnosed quadrants. In patients undergoing nonthoracic surgery, atelectasis was found to be in the posterior zones of both lungs, while the remaining atelectasis was discovered only in the operative lungs of VATS patients. Among the 82 patients with postoperative atelectasis, 19 patients showed signs of atelectasis on preoperative routine chest imaging examinations, while the remaining atelectasis was diagnosed only after surgery.
Twenty-eight patients (24.8%) (75 quadrants) were diagnosed with pneumothorax by CT scan, whereas 72 quadrants of these 75 quadrants were also diagnosed with pneumothorax with LUS. The majority of these pneumothorax patients (26 patients) were in the VATS group, and the pneumothorax was mainly distributed in anterior and lateral quadrants. In VATS patients, 11 cases of pneumothorax were small, while fifteen were medium in size. The other two patients underwent partial hepatectomy surgery. Regarding the last 2 patients, one was diagnosed with small pneumothorax both by LUS and CT scan, while another was diagnosed with medium pneumothorax, and CT reported an approximate 50% prevalence of tension pneumothorax.
Pleural effusion was found in 144 quadrants on CT scan in 39 patients (34.5%), which was primarily exhibited in posterior quadrants. LUS examination detected 131 quadrants with effusion among these CT-diagnosed zones. Nineteen patients (48.7%) received a diagnosis of pleural effusion on preoperative chest radiographs. The other 20 patients were newly diagnosed in the VATS group, all on the operative sides. One patient was diagnosed with massive pleural effusion on the left side, with visible anechoic effusion in the six quadrants.
One patient was diagnosed with diffuse interstitial syndrome due to multiple B-lines in all 12 lung quadrants, and a CT scan led to the same diagnosis. Both LUS examination and CT scan showed no abnormalities in 12 patients.
The time needed for the LUS examination was significantly shorter than that needed for the CT scan (10.8 ± 1.8 min versus 26.8 ± 4.2 min, P < 0.001). Kappa values for the agreement between the first two observers of atelectasis, pneumothorax and pleural effusion were 0.951 (P < 0.001), 0.858 (P < 0.001) and 0.964 (P < 0.001), respectively. To resolve this disagreement, the third reviewer was mainly devoted to evaluating the diagnosis of pneumothorax. Table 2 shows the findings of LUS and CT scans for diagnosing atelectasis, pneumothorax and pleural effusion. LUS was reliable in the diagnosis of atelectasis (with a sensitivity of 98.0%, specificity of 96.7%, positive predictive value of 93.3%, negative predictive value of 99.1% and diagnostic accuracy of 97.2%), pneumothorax (with a sensitivity of 90.0%, specificity of 98.9%, positive predictive value of 96.0%, negative predictive value of 96.9% and diagnostic accuracy of 96.7%) and pleural effusion (sensitivity of 92.9%, specificity of 96.0%, positive predictive value of 91.0%, negative predictive value of 96.9% and diagnostic accuracy of 95.1%). Among the data we collected, post hoc analyses revealed no correlative factor that significantly influenced LUS scores (Table 3). Postoperative typical LUS and corresponding thoracic CT images of atelectasis, pneumothorax, and pleural effusion are displayed in Figure 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.
BMC Anesthesiol. 2020;20(220) © 2020 BioMed Central, Ltd.