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Background
It is unclear whether postoperative pulmonary complications (PPC) can be early predicted by lung ultrasound (LUS) score in older adults undergoing thoracoscopic lobectomy. This study aimed to evaluate the validity of lung ultrasound application.
Methods
Two physicians performed lung ultrasonography on patients preoperatively, 30 min postoperatively and 72 h postoperatively to obtain LUS score. Pulmonary complications occurred within 10 days postoperatively were recorded. The correlation between lung ultrasound results and PPC was analyzed using logistic regression model. ROC curve were applied to assess the prediction accuracy.
Results
PPC occurred in 115 of 292 patients (39.38%) in this study. Independent risk factors for PPC included higher age (OR 1.16, 95% CI 1.04–1.29, p = 0.007), COPD comorbidity (OR 5.03, 95% CI 1.29–19.59, p = 0.020), lower preoperative hemoglobin level (OR 0.96, 95% CI 0.93–1.00, p = 0.043), and higher postoperative 30 min LUS score (OR 1.32, 95% CI 1.22–1.43, p < 0.001). Postoperative 30 min lung ultrasound score (AUC: 0.811, cut-off: 14) shown in the ROC curve analysis was effective in predicting postoperative outcomes.
Conclusions
Postoperative 30 min lung ultrasound score is a risk factor for PPC in older adults undergoing thoracoscopic lobectomy in this study. The value of lung ultrasound as a predictive tool for PPC is warranted.
Trial Registry: This study was registered in China Clinical Trial Registry (ChiCTR2100053449).
Highlights
Older adults undergoing thoracoscopic lobectomy showed a high rate of PPC (39.38%).
Postoperative 30 min lung ultrasound score was a significant risk factor for PPC. (OR 1.32 95% CI 1.22–1.43 p < 0.001).
A highly predictive indicator of PPC was the postoperative 30 min lung ultrasound score (AUC 0.811).
Introduction
Patients undergoing thoracic surgery often face poor prognoses due to postoperative pulmonary complications (PPC) [1, 2] and are considered to prolong hospitalization and increase the risk of death [3]. Because of variations in definitions and populations studied, the incidence varies. It is generally recognized that PPC occurs relatively frequently, with an incidence of approximately 31.2% [4]. Common PPC [2, 5, 6] include the following: respiratory failure, pneumonia [7], atelectasis, pneumothorax, bronchospasm, pleural effusion, pulmonary edema, etc. Despite the significant advances that have been made in anesthesia and surgery, PPC remains an important issue in clinical practice. On the other hand, aging is increasing worldwide, and patients undergoing lung cancer surgery are older, with decreased respiratory muscle function and mucociliary clearance ability [6], and comorbidities with underlying diseases that lead to decreased cardiac and pulmonary function. And it is possible that surgery, anesthesia, and pain factors [8] contribute to the occurrence of PPC.
Methods for the evaluation and diagnosis of PPC have been extensively reported, but early identification of high-risk PPC patients remains a challenge [9]. Traditional computed tomography (CT) and chest X-ray (CXR) are still routinely examinations in thoracic surgery, but they have certain limitations [10, 11]. We are seeking more simple and effective methods of evaluation. The technique of lung ultrasound (LUS) is highly reproducible rapid, non-invasive, and has become an important tool for evaluating lung status with a high degree of accuracy [12], such as pneumonia [13], pleural effusion [14], atelectasis [15], and pneumothorax [16]. There are better results if clinically relevant PPC was detected by lung ultrasound [10]. Previous studies have quantified lung ventilation loss corresponding to lung ultrasound images [17]. LUS score was valuable in predicting PPC after major abdominal surgery [9], and its applicability has been improved, enabling routine monitoring.
This study aims to evaluate the value of lung ultrasound in thoracoscopic lobectomy for older adults, help early detection of high-risk patients, and to take appropriate perioperative protection measures.
Methods
Study design
The Medical Ethics Committee of the First Affiliated Hospital of Bengbu Medical University approved this study (2020KY060). It was registered in the China Clinical Trial Registry (ChiCTR2100053449) before the study started. All patients signed a written informed consent.
This study was a prospective observational research, including 292 older adults who underwent elective thoracoscopic lobectomy between November 2021 and October 2023 at the First Affiliated Hospital of Bengbu Medical University. In this study, we defined older adults as individuals aged 65 years or older [18]. Inclusion criteria were as follows: American Society of Anesthesiologists (ASA) classification I-III and age ≥ 65 years. Exclusion criteria were as follows: refusal to participate in this study; severe heart, liver, and renal dysfunction before operation; poor visualization of lung ultrasound; withdrawal consent midway; and change in surgical approach.
Anesthesia and surgical protocols
Anesthesia induction, maintenance, ventilation strategy, and analgesia postoperatively were standardized and identical for every patient. Anesthesia induction used sufentanil (0.5 μg/kg), midazolam (0.03 mg/kg), etomidate (0.3 mg/kg), and rocuronium (0.6 mg/kg). After induction a double-lumen endotracheal tube or bronchial occluder was inserted for single-lung ventilation, and the correct position was verified using fiberoptic bronchoscopy. Anesthesia was maintained using remifentanil (0.05–0.2 μg/kg/min), propofol (4–6 mg/kg/h), sevoflurane (1–2%), and cisatracurium was added if necessary. The dose was adjusted based on anesthesia depth, maintaining the bispectral index at 40–60, and controlling the fluctuation of MAP within 20% of the baseline. The protective lung ventilation strategy was volume control mode, with a tidal volume of 6–8 ml/kg for two-lung ventilation and 5–6 ml/kg for single-lung ventilation, peak pressure of < 30 cm H2O, inspired oxygen concentration of 0.4–0.8, and positive end-expiratory pressure of 6 cm H2O. To keep the end-tidal carbon dioxide at 35–45, respiratory rate and the inspired oxygen concentration were adjusted. Alveolar recruitment maneuvers (ARMs) were performed every 30 min (30 cm H2O pressure for 30 s). After the surgery, sputum was thoroughly suctioned, and ARM was performed. Patients were then moved to the post-anesthetic care unit (PACU) or extubated in the operating room. They was provided with standardized patient-controlled analgesia with the following protocol: sufentanil 2 μg/kg diluted to 100 mL with normal saline, administered as a background infusion at 2 mL/h with a bolus dose of 2 mL, and a lockout interval of 15 min. Postoperative pain control was assessed using Numeric Rating Scale (NRS, ranging from 0 for no pain to 10 for the worst pain imaginable).
All surgeries were performed using a uniportal video-assisted thoracic surgery (uniportal VATS) approach through a single incision at the 4th or 5th intercostal space on the midaxillary line. After surgery, a 26 Fr chest tube was placed in all patients, with its tip positioned near the pleural apex, and immediately connected to a water seal drainage system.
Lung ultrasonography protocol
Shenzhen Wisonic ultrasonic diagnostic instrument (Clover 60, C5-1 convex array probe, frequency 1.0–5.5 MHz) was used for lung ultrasonography. Each patient underwent lung ultrasound at three time points: preoperatively when entering the anesthesia preparation room (preoperative), 30 min after extubation in the PACU (postoperative 30 min), and 72 h after returning to the ward from the PACU (postoperative 72 h). Twelve areas were demarcated according to the patient's anterior and posterior axillary line, parathoracic line, paravertebral line, and nipple plane (Fig. 1). A comprehensive lung ultrasound was performed on the patient, with at least one complete breath in each region. Strict aseptic protocols were maintained in the management of the drainage tube area to avoid contamination. All patients were performed by the same two physicians and re-examined if the results were inconsistent. These two physicians only performed lung ultrasonography and were not involved in other processes of this study. If there were multiple ultrasound manifestations within a sub-region, the maximum value was taken. All regions were totaled to give a final score (0–36). Scoring criteria (Fig. 2): clear A-lines or a few B-lines (≤ 2) were 0 points, clearly spaced B-lines were 1 points, diffuse fusion B-lines were 2 points, and lung consolidation were 3 points [19, 20–21].
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Fig. 1
Zone setting of lung ultrasound examination. Twelve areas were demarcated according to the patient's anterior and posterior axillary line, parathoracic line, paravertebral line, and nipple plane
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Fig. 2
Typical ultrasound images with different scores. Clear A-lines or a few B-lines (≤ 2) were scored as 0 ( aor b), well-spaced clear B-lines were scored as 1 (c), diffuse fusion B-lines were scored as 2 (d), and lung consolidation was scored as 3 (e, f) [19, 20–21]
Definition and diagnosis of PPC
PPC was followed and recorded by the same physician who followed the patient daily for 10 days postoperatively and was not involved in other processes of this study. PPC was diagnosed using clinical presentation, imaging studies, and laboratory tests. PPC [2, 5, 6] in this study included the following: respiratory failure, pneumonia [7], atelectasis, pneumothorax, bronchospasm, pleural effusion, acute exacerbation of interstitial pneumonia (AE-IP) [22], and pulmonary edema. The definition and diagnosis of PPC are presented in Supplementary Table 1.
Data collection
Data collection checklist: age, sex, body mass index (BMI), tumor pathological type, tumor clinical stage, resected lobe, American Society of Anesthesiologists (ASA) classification, smoking status, comorbidities (coronary heart disease, diabetes, hypertension, cerebral infarction, chronic obstructive pulmonary disease [COPD], interstitial pneumonia), pulmonary function test (FEV1/FVC, FEV1 percent predicted [FEV1%pred]), lung ultrasound score (preoperative, postoperative 30 min, postoperative 72 h), hemoglobin level (preoperative, postoperative day 1), single-lung ventilation time, intraoperative blood loss, NRS score (postoperative 30 min, postoperative 24 h, postoperative 72 h), hospital stay (preoperative, postoperative, total), and PPC occurrence.
Statistical analysis
Statistical analysis and picture drawing were performed using the R version 4.4.1 and GraphPad Prism 10.0 software. The Shapiro–Wilk test was used to assess normality. Data with normal distribution are presented as mean ± standard deviation (SD) and analyzed using t-test. Data not following normal distribution are shown as median (M) and interquartile range (IQR) and analyzed using the Mann–Whitney U test. Counting data were shown as cases (%) and analyzed using χ2 test or Fisher exact probability method. Factors from the univariate analysis with p < 0.1 were included in logistic regression analysis model, to obtain independent risk factors for PPC, and the Hosmer–Lemeshow test was used to assess model fit. The Yoden index was calculated to derive the cut-off value using the ROC curve. Statistical significance was determined by p < 0.05.
Sample size calculation
Previous study results showed the incidence of PPC was approximately 31.2% [4]. Multivariate analysis was expected to include 4 variables according to the 15EPV principle, resulting in 15*4/0.312 = 193. Considering a 20% dropout rate, at least 242 patients needed to be included in this study.
Results
Patient perioperative characteristics
A total of 323 patients were included, and the final data of 292 patients eligible for enrollment were analyzed (Fig. 3). The perioperative characteristics of patients are shown in Table 1. Age, tumor clinical stage, ASA classification, diabetes, COPD, postoperative 30 min LUS score, single-lung ventilation time, and postoperative hospital stay were higher in PPC group than those in non-PPC group. FEV1/FVC, preoperative hemoglobin level, postoperative day 1 hemoglobin level, and preoperative hospital stay were lower in PPC group than those in non-PPC group.
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Fig. 3
Study flow chart
Table 1. Perioperative characteristics of patients
Variables | PPC (n = 115) | Non-PPC (n = 177) | Total (n = 292) | p |
|---|---|---|---|---|
Age (years) | 71 (68, 74) | 69 (67, 71) | 70 (67, 72) | < 0.001 |
Sex | 0.777 | |||
Male | 57 (50) | 92 (52) | 149 (51) | |
Female | 58 (50) | 85 (48) | 143 (49) | |
BMI (kg/m2) | 23.44 (21.45, 25.97) | 23.88 (22.19, 26.18) | 23.69 (21.78, 26.17) | 0.310 |
Tumor pathological type | 0.291 | |||
Benign tumor | 21 (18) | 23 (13) | 44 (15) | |
Carcinoma in situ | 12 (10) | 19 (11) | 31 (11) | |
Adenocarcinoma | 66 (57) | 120 (68) | 186 (64) | |
Squamous cell carcinoma | 14 (12) | 14 (8) | 28 (10) | |
Small cell carcinoma | 2 (2) | 1 (1) | 3 (1) | |
Tumor clinical stage | 0.037 | |||
0 | 33 (29) | 42 (24) | 75 (26) | |
I | 52 (45) | 107 (60) | 159 (54) | |
II | 18 (16) | 13 (7) | 31 (11) | |
III | 12 (10) | 15 (8) | 27 (9) | |
Resected lobe | 0.655 | |||
Left upper lobe | 19 (17) | 33 (19) | 52 (18) | |
Left lower lobe | 24 (21) | 29 (16) | 53 (18) | |
Right upper lobe | 34 (30) | 64 (36) | 98 (34) | |
Right middle lobe | 12 (10) | 14 (8) | 26 (9) | |
Right lower lobe | 26 (23) | 37 (21) | 63 (22) | |
ASA classification | 0.004 | |||
I | 26 (23) | 70 (40) | 96 (33) | |
II | 46 (40) | 66 (37) | 112 (38) | |
III | 43 (37) | 41 (23) | 84 (29) | |
Comorbidities | ||||
Hypertension | 59 (51) | 89 (50) | 148 (51) | 0.959 |
Diabetes | 20 (17) | 14 (8) | 34 (12) | 0.023 |
Cerebral infarction | 34 (30) | 45 (25) | 79 (27) | 0.52 |
Coronary heart disease | 10 (9) | 14 (8) | 24 (8) | 0.983 |
COPD | 37 (32) | 21 (12) | 58 (20) | < 0.001 |
Interstitial pneumonia | 3 (3) | 2 (1) | 5 (2) | 0.341 |
Smoking status | 27 (23) | 25 (14) | 52 (18) | 0.059 |
FEV1/FVC | 73.54 (64.56, 78.2) | 75.42 (70.93, 78.6) | 74.71 (69.6, 78.25) | 0.02 |
FEV1%pred | 96.33 ± 24.19 | 98.96 ± 20.93 | 97.92 ± 22.27 | 0.34 |
Lung ultrasound score | ||||
Preoperative | 6 (4, 10) | 6 (4, 8) | 6 (4, 9) | 0.46 |
Postoperative 30 min | 16 (12, 18) | 9 (6, 13) | 11 (8, 15) | < 0.001 |
Postoperative 72 h | 9 (6, 12) | 8 (6, 11) | 8 (6, 12) | 0.066 |
Hemoglobin level (g/L) | ||||
Preoperative | 126.97 ± 13.7 | 134.55 ± 11.54 | 131.57 ± 12.95 | < 0.001 |
Postoperative day 1 | 121 (113.5, 129) | 128 (119, 134) | 125 (117, 132) | < 0.001 |
Single-lung ventilation time (min) | 119 (91, 148.5) | 102 (79, 135) | 108 (83, 138) | 0.01 |
Intraoperative blood loss (mL) | 100 (80, 150) | 100 (80, 100) | 100 (80, 100) | 0.464 |
NRS score | ||||
Postoperative 30 min | 1 (1, 2) | 1 (0, 2) | 1 (0, 2) | 0.592 |
Postoperative 24 h | 3 (2, 3) | 3 (1, 4) | 3 (2, 3) | 0.273 |
Postoperative 72 h | 1 (0, 1) | 1 (0, 1) | 1 (0, 1) | 0.935 |
Hospital stay (day) | ||||
Preoperative | 5 (4, 7) | 6 (4, 8) | 6 (4, 8) | 0.038 |
Postoperative | 6 (5, 8) | 6 (4, 7) | 6 (4, 7) | 0.004 |
Total | 12 (10, 16) | 12 (9, 15) | 12 (10, 15) | 0.847 |
PPC postoperative pulmonary complications, BMI Body mass index, ASA American Society of Anesthesiologists, COPD Chronic obstructive pulmonary disease, FEV1 Forced expired volume at 1 s, FVC Forced vital capacity, %pred Percent predicted, NRS Numeric rating scale
Changes in LUS score
The changes in LUS score of the two groups are shown in Fig. 4. The preoperative LUS score were 6 (IQR 4–10) and 6 (IQR 4–8), respectively, with no significant difference (p = 0.46). At 30 min postoperatively, LUS score increased significantly in both groups, with more obvious increase in patients in PPC group (median 16; IQR 12–18) compared to non-PPC group (median 9; IQR 6–13) (p < 0.001). At 72 h postoperatively, LUS score began to decrease to 9 (IQR 6, 12) and 8 (IQR 6, 11), respectively, but remained significantly higher compared to preoperatively. LUS score tended to be higher in PPC group, but the difference was not significant (p = 0.066).
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Fig. 4
Lung ultrasound scores at different time points in the PPC and non-PPC groups. Median values with interquartile ranges. **: p < 0.001 (Mann–Whitney U)
Incidence of PPC
The incidence of PPC was 39.38% (115/292). Specifically, 40.87% (47/115) had respiratory failure, 37.39% (43/115) had atelectasis, 27.83% (32/115) had pneumonia, 11.30% (13/115) had pleural effusion, 9.57% (11/115) had pulmonary edema, 8.70% (10/115) had bronchospasm, 3.48% (4/115) had pneumothorax, and 0.00%(0/115) and 23.48% (27/115) had two or more types of PPC (Table 2).
Table 2. Type and frequency of PPC
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PPC Postoperative pulmonary complications, AE-IP Acute exacerbation of interstitial pneumonia
Univariate analysis of risk factors
Univariate analysis showed that age (OR 1.18, 95% CI 1.10–1.26, p < 0.001), tumor clinical stage I (OR 0.62, 95% CI 0.35–1.09, p = 0.095), ASA classification II (OR 1.88, 95% CI 1.04–3.37, p = 0.035), ASA classification III (OR: 2.82, 95% CI: 1.52–5.25, p = 0.001), diabetes (OR 2.45, 95% CI 1.18–5.08, p = 0.016), COPD comorbidity (OR 3.52, 95% CI 1.93–6.42, p < 0.001), smoking status (OR 1.87, 95% CI 1.02–3.41, p = 0.043), FEV1/FVC (OR 0.97, 95% CI 0.94–0.99, p = 0.011), postoperative 30 min LUS score (OR 1.33, 95% CI 1.24–1.43, p < 0.001), and preoperative hemoglobin level (OR 0.95, 95% CI 0.93–0.97, p < 0.001), postoperative day 1 hemoglobin level (OR 0.97, 95% CI 0.95–0.98, p < 0.001), and single-lung ventilation time (OR 1.01, 95% CI 1.00–1.01, p = 0.038) were correlated with the occurrence of PPC (Table 3).
Table 3. Univariate and multivariate logistic regression analysis of risk factors associated with PPC
Variables | OR (univariate) | p | OR (multivariate) | p |
|---|---|---|---|---|
Age (years) | 1.18 (1.10–1.26) | < 0.001 | 1.16 (1.04–1.29) | 0.007 |
Sex | ||||
Male | 1.0 (reference) | |||
Female | 1.10 (0.69–1.76) | 0.687 | ||
BMI (kg/m2) | 0.97 (0.90–1.04) | 0.400 | ||
Tumor pathological type | ||||
Benign tumor | 1.0 (reference) | |||
Carcinoma in situ | 0.69 (0.27–1.76) | 0.439 | ||
Adenocarcinoma | 0.60 (0.31–1.17) | 0.134 | ||
Squamous cell carcinoma | 1.10 (0.42–2.83) | 0.851 | ||
Small cell carcinoma | 2.19 (0.18–25.96) | 0.534 | ||
Tumor clinical stage | ||||
0 | 1.0 (reference) | 1.0 (reference) | ||
I | 0.62 (0.35–1.09) | 0.095 | 0.55 (0.26–1.18) | 0.124 |
II | 1.76 (0.76–4.11) | 0.190 | 0.91 (0.30–2.78) | 0.873 |
III | 1.02 (0.42–2.47) | 0.968 | 0.67 (0.20–2.26) | 0.519 |
Resected lobe | ||||
Left upper lobe | 1.0 (reference) | |||
Left lower lobe | 1.44 (0.66–3.14) | 0.363 | ||
Right upper lobe | 0.92 (0.46–1.86) | 0.822 | ||
Right middle lobe | 1.49 (0.57–3.87) | 0.414 | ||
Right lower lob | 1.22 (0.57–2.60) | 0.605 | ||
ASA classification | ||||
I | 1.0 (reference) | 1.0 (reference) | ||
II | 1.88 (1.04–3.37) | 0.035 | 0.88 (0.39–1.99) | 0.753 |
III | 2.82 (1.52–5.25) | 0.001 | 0.61 (0.21–1.77) | 0.361 |
Comorbidities | ||||
Hypertension | 1.04 (0.65–1.67) | 0.865 | ||
Diabetes | 2.45 (1.18–5.08) | 0.016 | 1.89 (0.71–5.05) | 0.202 |
Cerebral infarction | 1.23 (0.73–2.08) | 0.437 | ||
Coronary heart disease | 1.11 (0.48–2.59) | 0.811 | ||
COPD | 3.52 (1.93–6.42) | < 0.001 | 5.03 (1.29–19.59) | 0.020 |
Interstitial pneumonia | 2.34 (0.39–14.25) | 0.355 | ||
Smoking status | 1.87 (1.02–3.41) | 0.043 | 1.37 (0.57–3.27) | 0.482 |
FEV1/FVC | 0.97 (0.94–0.99) | 0.011 | 1.01 (0.95–1.07) | 0.855 |
FEV1%pred | 0.99 (0.98–1.01) | 0.324 | ||
Lung ultrasound score | ||||
Preoperative | 1.05(0.97–1.12) | 0.214 | ||
Postoperative 30 min | 1.33 (1.24–1.43) | < 0.001 | 1.32 (1.22–1.43) | < 0.001 |
Postoperative 72 h | 1.05(0.99–1.12) | 0.124 | ||
Hemoglobin level (g/L) | ||||
Preoperative | 0.95 (0.93–0.97) | < 0.001 | 0.96 (0.93–1.00) | 0.043 |
Postoperative day 1 | 0.97 (0.95–0.98) | < 0.001 | 0.99 (0.96–1.03) | 0.665 |
Single-lung ventilation time (min) | 1.01 (1.00–1.01) | 0.038 | 1.00 (1.00–1.01) | 0.249 |
Intraoperative blood loss (mL) | 1.00 (1.00–1.01) | 0.349 | ||
NRS score | ||||
Postoperative 30 min | 1.08 (0.89–1.30) | 0.435 | ||
Postoperative 24 h | 0.96 (0.81–1.14) | 0.672 | ||
Postoperative 72 h | 0.98 (0.71–1.36) | 0.902 | ||
PPC Postoperative pulmonary complications, BMI Body mass index, ASA American Society of Anesthesiologists, COPD Chronic obstructive pulmonary disease, FEV1 forced expired volume at 1 s, FVC Forced vital capacity, %pred Percent predicted, NRS Numeric rating scale
Multivariate analysis of risk factors
Higher age (OR 1.16, 95% CI 1.04–1.29, p = 0.007), COPD comorbidity (OR 5.03, 95% CI 1.29–19.59, p = 0.020), lower preoperative hemoglobin level (OR 0.96, 95% CI 0.93–1.00, p = 0.043), and higher postoperative 30 min LUS score (OR 1.32, 95% CI 1.22–1.43, p < 0.001) were independently associated with PPC in this study according to multivariate analysis (Table 3).
ROC curve analysis of risk factors
Age (AUC: 0.656, cut-off: 71.5, sensitivity: 45.2%, specificity: 78.5%), COPD (AUC: 0.602, cut-off: 0.5, sensitivity: 32.2%, specificity: 88.1%), preoperative hemoglobin level (AUC: 0.665, cut-off: 123.5, sensitivity: 83.6%, specificity: 44.3%), and postoperative 30 min LUS score (AUC: 0.811, cut-off: 14.5, sensitivity: 57.4%, specificity: 90.9%) were effective in predicting PPC after lobectomy in older adults in the ROC curve analysis (Table 4 and Fig. 5).
Table 4. ROC curve analysis of age, COPD, preoperative hemoglobin level, and postoperative 30 min LUS score in predicting the occurrence of PPC
Variable | Cut-off | Sensitivity | Specificity | PPV | NPV | Accuracy | 95CI | p-value |
|---|---|---|---|---|---|---|---|---|
Age | 71.5 | 0.452 | 0.785 | 0.578 | 0.688 | 0.654 | 0.590–0.720 | 1.000 |
COPD | 0.5 | 0.322 | 0.881 | 0.638 | 0.667 | 0.661 | 0.550–0.650 | 1.000 |
Preoperative hemoglobin level | 123.5 | 0.836 | 0.443 | 0.638 | 0.698 | 0.682 | 0.600–0.730 | < 0.001 |
Postoperative 30 min LUS score | 14.5 | 0.574 | 0.909 | 0.805 | 0.767 | 0.777 | 0.760–0.860 | 1.000 |
COPD Chronic obstructive pulmonary disease, LUS Lung ultrasound, PPC Postoperative pulmonary complications, PPV Positive predictive value, NPV Negative predictive value, CI Confidence interval
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Fig. 5
Predictive values of risk factors. The occurrence of PPC was predicted using AUC and 95% CI for age, COPD, preoperative hemoglobin level, and postoperative 30 min lung ultrasound score. COPD Chronic obstructive pulmonary disease
Discussion
This study's main purpose was to assess the predictive value of lung ultrasound score for PPC. The analysis showed that postoperative 30 min lung ultrasound score > 14 had a significant effect on the occurrence of PPC.
Lung ultrasound used widely in multiple disciplines and was believed to enhance clinical decision making [10, 17, 23]. In acute lung injury experiment in pigs, extravascular lung water increased due to exudation, which could be detected by ultrasound before the gas produces an impaired exchange [24]. B-lines are widely recognized as a sign of interstitial and alveolar edema. Many studies have shown a high correlation between interstitial injury and B-lines in lung disease [25, 26, 27–28]. Loss and change in ventilation during treatment can be detected by changes in ultrasound images [29, 30]. It has been found that LUS score > 13 measured after the recovery of spontaneous breathing can predict extubation failure [17]. Among patients with ICU admissions following major surgery, LUS score and atelectasis detection can predict postoperative pulmonary outcomes. Lower PaO2/FiO2 was observed in patients whose LUS score ≥ 10 and more respiratory support was required after surgery, and the specificity was high for LUS score ≥ 14 [31]. In major abdominal surgery, postoperative day 1 LUS score was an early and accurate predictor of PPC [9, 21]. After cardiothoracic surgery, lung ultrasound is earlier and more valuable in detecting PPC [10], and is thought to frequently change the diagnosis of clinical respiratory lesions [32]. Study suggested that daily LUS examination postoperatively can be used for early detection of PPC and help accelerate surgical rehabilitation [33]. The AUC of postoperative 30 min LUS score in this study was 0.811 and LUS score > 14 had a very high specificity (90.9%), which is worthwhile as a predictive tool for PPC. Similar to previous study [21], the AUC of their model was 0.896, identifying postoperative LUS score > 5 as a predictor of PPC. Our cut-off value is higher than them, and the reason is that the population included in this study was older and underwent lobectomy, resulting in greater postoperative lung ventilation injury. In the multivariate analysis, LUS score did not show a difference at 72 h postoperatively, which may be related to the fact that ventilation has begun to improve, but has not yet returned to normal. On the other hand, lung ultrasound may be too sensitive to changes in ventilation injury. Theoretically, early treatment based on lung ultrasound may lead to the problem of overtreatment of PPC. This requires us to combine clinical symptoms with lung ultrasound signs. Since we performed lung ultrasound 30 min after extubation, we emphasize the important role of our protocol for early prediction of PPC.
Lung air content change model has shown that LUS results correlate with progressive changes in pulmonary ventilatory status [34]. Atelectasis underlies postoperative pulmonary ventilatory dysfunction and respiratory complications [6]. Atelectasis and pneumonia are closely linked because changes due to atelectasis may induce pulmonary complications [35, 36]. Tissue compression, gas absorption, and surfactant injury may all contribute to the development of perioperative atelectasis [36, 37]. The increase in intrathoracic pressure during single-lung ventilation leads to impaired venous return and decreases cardiac output, resulting in an imbalance in ratio of air to blood flow, and the lung will collapse again within a short time after discontinuing PEEP. Initial findings showed that LUS-guided personalized PEEP improved pulmonary ventilation and oxygenation in elderly patients undergoing laparoscopic surgery, resulting in reduced severity of atelectasis within 7 days after surgery. [38]. There was also a high correlation between LUS score and postoperative quantification of atelectasis volume [39]. During induction of anesthesia, the application of PEEP (6 cm H2O) was efficient at preventing the occurrence of atelectasis [40], but they only measured twice using CT before anesthesia initiation and after intubation, which could be examined on multiple occasions if lung ultrasound was introduced without worrying about radiation and cost. PPC prevention by strategies such as low tidal volume, low inspired oxygen concentration, pulmonary recruitment, and PEEP (6–8 cm H2O) have been reported to be beneficial [41, 42], and we applied these anesthesia protocols. In this study, we observed a lower incidence of atelectasis (37.39%) than earlier study (67.2%) [16], due to more strict implementation of lung-protective ventilation and more frequent ARM. In this study, we observed that LUS score was higher than preoperative at 30 min postoperatively, and the score began to decrease but still higher than preoperative at 72 h postoperatively, which was consistent with the recovery process of perioperative lung trauma. Therefore, we concluded that early LUS score can effectively assess lung function in elderly patients undergoing lobectomy.
The observed increase in the LUS score within 30 min postoperatively serves as an early warning signal requiring immediate clinical intervention. Based on our observations and clinical experience, when the LUS score is > 14 at 30 min postoperatively, we recommend an immediate clinical reassessment, commencing with a rapid evaluation that integrates the patient's vital signs, body temperature, and clinical symptoms, followed by a targeted etiological investigation to identify underlying causes. Additionally, monitoring frequency should be increased through upgraded surveillance at shorter intervals to track disease progression and evaluate treatment response. This must include enhanced pulmonary physiotherapy and planning for bronchoscopic suction or empirical antibiotic therapy, as clinically indicated.
Lung ultrasonography requires adequate training for better clinical application, and basic skills can be acquired by physicians without professional knowledge of lung ultrasound after 25 supervised tutorials [19, 43], which is also influenced by the motivation of learner, typically between 5 weeks and 5 months [43]. In this study, to minimize inter-operator variability, all lung ultrasound examinations were performed by two physicians who underwent unified and rigorous training. Furthermore, previous studies have demonstrated good inter-observer agreement in lung ultrasound [10]. Each standard lung ultrasound examination in this study required approximately 10–20 min on average. The duration may vary slightly depending on the patient’s body habitus, cooperation level, and the complexity of any detected abnormalities. When we first started learning lung ultrasound, we would perform long, high-pressure scans in one area in order to get clearer images, resulting in varying degrees of muscle pain in patients, but of course this was no longer a problem after we became proficient. It is also inspiring for beginners to not insist on getting the clearest images when first learning, to extend the learning time appropriately, and to optimize the images dynamically during the scanning process. We believe that the protocol and results of this study possess strong potential for generalization. The essence of promoting lung ultrasound examination lies not in disseminating the skill of an individual operator, but rather in establishing a standardized training protocol and operational procedure. Any clinician with basic ultrasound knowledge can acquire the ability to execute the protocol described in this study, provided that a structured training system is in place.
Limitations
For patients with obesity and subcutaneous emphysema, visualization of lung ultrasound is difficult. The accuracy of lung ultrasound results mainly depends on the operator's skills, and effective training is required to accurately recognize lung ultrasound images.
We only performed lung ultrasound examinations at three time points, and in the future we can choose more time points to describe the process of pulmonary function regression after lobectomy in more detail.
As this is a single-center study with a limited number of patients with comorbid interstitial pneumonia, the analysis of AE-IP was underpowered. The primary objective of this study was to investigate the relationship between lung ultrasound scores and postoperative pulmonary complications; therefore, specific associations between individual sonographic signs and particular complications may not have been fully explored. In addition, this study focused primarily on complications of the pulmonary system and did not extensively investigate complications involving other organ systems. Future studies with larger sample sizes are needed to address these limitations.
Conclusion
The lung ultrasound score at postoperative 30 min is a powerful predictor of postoperative pulmonary complications in older adults undergoing thoracoscopic lobectomy. When the lung ultrasound score is > 14 points at this time point, the risk of PPC increases significantly; therefore, necessary measures should be taken for perioperative protection.
Acknowledgements
We are very grateful to Professor Xiaohong Li for his expert guidance on this study and manuscript revision. We would like to thank all medical staff for their cooperation.
Author contributions
Research design and conception: Dongsheng Wang, Xiaohong Li. Patient recruitment: Dongsheng Wang, Xiaohong Li. Lung ultrasonography: Yang Zhang, Qin Zhuang. Postoperative pulmonary complications follow-up and recording: Shasha Wang. Data collection: Dongsheng Wang, Yanan Xue, Jiaojiao Gao, Ru Yu. Data analysis: Dongsheng Wang, Xiaohong Li, Erdeng Cheng, Xiaoyi Hu. Writing of the manuscript: Dongsheng Wang, Xiaohong Li. All authors reviewed the manuscript.
Funding
No funding was received for this study.
Data availability
The datasets used and analyzed during this study are available from the corresponding author.
Declarations
Ethics approval and consent to participate
All patients provided written informed consent before they were enrolled. No information in this report can be used to identify patients personally. The patients' personal information has been deleted.
Competing interests
The authors declare no competing interests.
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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