Effect of the tubeless approach on the non-operative lung in thoracic surgery: a retrospective cohort study

Introduction

Video-assisted thoracic surgery (VATS) has become a widely used minimally invasive approach in thoracic surgery; however, it is still associated with a spectrum of postoperative pulmonary complications (PPCs), which remain major contributors to postoperative morbidity and mortality (1,2). While expected complications primarily occur on the operative side of lung, PPCs can also develop in the non-operative lung (3-5). One-lung ventilation (OLV) during thoracic surgery may induce barotrauma on the non-operative lung within minutes to hours (6,7), involving alveolar damage and inflammatory responses, potentially leading to prolonged postoperative recovery periods (8). Although enhanced recovery after surgery (ERAS^®) guidelines emphasize lung-protective ventilation strategies (9), risks associated with positive pressure ventilation still occur occasionally.

Minimally invasive thoracic surgery has undergone remarkable advancement over the past few decades, with tubeless anesthesia emerging as an innovative approach (10-12). This surgical and anesthetic technique has demonstrated numerous advantages including reduced anesthetic dosage, enhanced recovery and improved surgical accessibility (12,13). During surgery, negative pressure in the non-operative hemithorax allows active gas inhalation via diaphragmatic and intercostal muscle movements, preserving lung compliance, reducing postoperative declines in pulmonary function, and promoting efficient gas-perfusion balance (14). This mechanism has been validated in animal studies (15), demonstrating that the non-operative lung is not inferior to that under OLV in terms of lung injury. However, supporting evidence in humans remains lacking.

Understanding the potential protective effects of the tubeless approach on the non-operative lung is crucial for elucidating its mechanisms and further optimizing postoperative recovery. Despite the growing adoption of tubeless techniques, there remains a critical knowledge gap regarding their physiological impact on the non-operative lung during and after surgery, specifically in terms of outcomes measurable via computed tomography (CT) imaging and intraoperative respiratory parameters. Clarifying these mechanisms could not only validate current practices, but also guide the optimization of anesthetic protocols to enhance patient outcomes.

This study aims to investigate the impact of tubeless approach for VATS on non-operative lung changes, comparing it with double-lumen tube (DLT) intubated anesthesia through a retrospective cohort study. We present this article in accordance with the STROBE reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1024/rc).

Methods

Study design and data source

From January 2020 to March 2025, surgical cases at The First Affiliated Hospital of Guangzhou Medical University were screened. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study protocol was approved by the institutional ethics committee of The First Affiliated Hospital of Guangzhou Medical University (Ethics Approval No. ES-2025-082-02). Written informed consent was obtained from all patients prior to their inclusion in the study, ensuring that participants were fully aware of the study objectives, procedures, potential risks, and benefits. All patient data were anonymized and handled confidentially to protect patient privacy throughout the research process. Figure 1 illustrates the procedure of patient selection and analysis. Inclusion criteria were as follows: (I) elective VATS thoracic surgery; (II) undergoing either left or right partial pulmonary resection; (III) American Society of Anesthesiologists (ASA) grading I to III; (IV) using either a DLT or a laryngeal mask as the airway tool; (V) successful removal of the airway tool was achieved, following which the patient was transferred to the designated ward; (VI) surgical duration ranging from 60 to 240 minutes; and (VII) available CT scans within 3 months before and 1 month after surgery. Exclusion criteria were as follows: (I) patients with missing information; (II) patients who declined to provide informed consent; and (III) patients who developed non-surgery-related pulmonary abnormalities within one month after the procedure. Follow-up data were collected through comprehensive electronic medical record reviews. All data were collected and checked by three researchers (Z.L., H.L. and R.W.), and the authors had no access to information that could identify individual participants during or after data collection. For the purpose of this research, clinical data were accessed in April 2025. To ensure the accuracy of the data, endpoints and outcomes were verified by two independent reviewers (H.Y. and C.W.).

Figure 1 Flow chart of patient inclusion and data processing. ^†, conditions may overlap. ASA, American Society of Anesthesiologists; CT, computed tomography; DLT, double-lumen tube; VATS, video-assisted thoracic surgery.

Anaesthesia protocols for surgery

Following previous expert consensus (13), the choice between tubeless and intubated approach was determined by multiple factors including the patient’s body mass index (BMI), airway anatomy, pulmonary function, surgical complexity, and anticipated operative duration. The final decision was reached through consensus among anesthesiologists, surgeons and patients, with patient safety as the paramount consideration.

Tubeless group: The anesthetic strategy emphasized spontaneous ventilation and regional nerve blocks (13). A laryngeal mask was used as the airway device to better control lung inflation, while maintaining spontaneous breathing in the non-operated lung for most of the surgical period. After confirming proper placement of the laryngeal mask, synchronized intermittent mandatory ventilation (SIMV) was initiated as a bridge to support ventilation until the resume of spontaneous breathing. During the initial phase of surgery, patients are expected to achieve stable spontaneous ventilation with minute ventilation ranging from 0.5 to 1.0 L/min, which was adjusted using anesthetic agents to maintain adequate gas exchange and depth of anesthesia. Regional anesthesia comprises pre-incisional local infiltration, vagus nerve block (to suppress the cough reflex) and intercostal nerve blocks (to enhance analgesia), all performed by surgeons under direct visualization. 2.5 mL of 0.5% ropivacaine + 2.5 mL of 2% lidocaine is injected at each site using a needle connected to an extension tube (13).

Intubated group: Patients received full-depth general anesthesia with DLT intubation. The DLT was inserted after adequate preoxygenation and induction of anesthesia, with depth confirmed by fiberoptic bronchoscopy. OLV was initiated at the start of surgery using a lung-protective ventilation strategy (16,17). Specific parameters included: tidal volume of 4–6 mL/kg (ideal body weight), positive end-expiratory pressure (PEEP) of 0–5 cmH₂O, and the choice of volume-controlled or pressure-controlled ventilation mode, which was determined according to each patient’s clinical condition. The fraction of inspired oxygen (FiO₂) was kept at the lowest level necessary; additionally, lung recruitment maneuvers were performed after the end of OLV. Intercostal nerve blocks were performed intraoperatively under direct visualization to alleviate postoperative pain.

Data collection and processing

Non-operative lung abnormalities were meticulously identified through a comprehensive manual review of both preoperative (within 3 months before surgery, using the last available scan) and postoperative (within 1 month after surgery, using the first available scan) CT reports (18). In cases of discrepancies, a consensus was reached through discussion, or advice was sought from a senior radiologist. Newly detected findings were categorized into four distinct groups (19): consolidation, diagnosed by terms such as “exudation”, “infiltrates”, “inflammation”, or “fibrotic changes” in CT reports (Figure 2A); hyperlucency, defined by “air trapping”, “pneumothorax”, “bullae”, “emphysema”, or “pneumomediastinum”, indicating presence of air (Figure 2B); pleural effusion is defined as the imaging finding of new-onset fluid accumulation in the pleural cavity (Figure 2C); and atelectasis, categorized based on radiological descriptions of lung collapse or partial collapse (Figure 2D). Patients with one or more types of these injuries were classified as having a single case of overall postoperative lung abnormalities.

Figure 2 Examples of CT images showing the manifestations of contralateral lungs in consolidation (A), hyperlucency (B), pleural effusion (C) and atelectasis (D). Green arrows indicate the abnormal findings. CT, computed tomography.

Intraoperative mechanical ventilation data, including tidal volume, minute ventilation, plateau pressure, mean pressure, PEEP, FiO₂, and respiratory rate, were derived from the anesthesia electronic records and calculated as the average values of all data points recorded throughout each surgery.

Clinical data were extracted from the electronic medical record system (Neusoft, version 5.0, Shenyang, China). CT imaging data were obtained from the picture archiving and communication system (Neusoft, version 5.5, Shenyang, China). Intraoperative vital signs and ventilation parameters were recorded at 5-minute intervals in the surgery and anesthesia record system (MedicalSystem, version 6, Suzhou, China). All data were stored in a MySQL database (version 5.7, Oracle, US) and preprocessed using Python (version 3.10). The accuracy and completeness of all data were verified by independent reviewers.

Statistical analysis

Continuous data are reported as the mean ± standard deviation (SD) if they follow a normal distribution, or as the median and interquartile range (IQR) if they are non-normally distributed. Categorical data are reported as counts and percentages. The Pearson Chi-squared test and Fisher’s exact test were conducted to compare the distribution of categorical variables. All analyses were performed using R software (R Foundation for Statistical Computing, Vienna, Austria), version 4.4.1. A two-sided P value of less than 0.05 was considered statistically for all analyses. Kaplan-Meier curves were generated using the R package Survival (version 3.8.3).

We employed propensity score matching (PSM) to mitigate selection bias arising from non-random assignment to the tubeless or intubated group. Using the MatchIt package (version 4.5.3) in R, logistic regression was applied to calculate propensity scores, with airway management approach (intubated vs. tubeless) as the dependent variable. The covariates included age, sex, BMI, surgery duration, preoperative pulmonary comorbidities (presence of emphysema, bullae, chronic obstructive pulmonary disease), intraoperative rescue events, and postoperative mechanical ventilation requirements. We performed nearest-neighbor matching at a 2:1 ratio without replacement, using a caliper width of 0.05 standard deviations of the logit-transformed propensity score (20,21).

A conditional logistic regression model was constructed to analyze matched pairs, with non-operative CT abnormality as the dependent variable. The model accounted for the matched nature of the data by stratifying on the matched pairs. Results were expressed as conditional odds ratios (ORs) with 95% confidence intervals (CIs) and visualized using a forest plot. The forest plot displays point estimates indicating effect sizes, with horizontal lines representing 95% CIs.

Results

Demographic characteristics before and after PSM

A total of 140,036 surgical cases were initially screened for eligibility. After applying the predefined inclusion and exclusion criteria, 1,294 patients were included in the final analysis. Among these, 1,045 patients underwent intubated approach and 249 underwent tubeless approach. After PSM, 427 patients in the intubated group were matched with 234 patients in the tubeless group (Table 1). The matching process successfully balanced all baseline characteristics between groups, with no significant differences in age, sex, BMI, ASA, duration of surgical procedure, surgical side, preoperative abnormal pulmonary function, time of CT scans (all P>0.05). The proportion of anatomical resection was comparable between the two groups (29.3% vs. 27.4%, P=0.67). The intubated group had a higher proportion of lobar resection (38.2% vs. 15.4%, P<0.001), while the tubeless group had a higher proportion of wedge resection (53.9% vs. 70.1%, P<0.001). The distribution of airway tools for each group is reported in Table S1.

Intraoperative characteristics

Intraoperative ventilation parameters differed markedly between groups (Table 2). The tubeless group showed lower average airway pressures: peak pressure (19.39 vs. 6.80 H₂O, P<0.001), mean pressure (7.28 vs. 3.23 cmH₂O, P<0.001), and plateau pressure (17.88 vs. 8.03 cmH₂O, P<0.001). Other respiratory parameters were also lower in the tubeless group, including respiratory rate (14.59 vs. 13.61 breaths/min, P<0.001), tidal volume (320.42 vs. 279.90 mL, P<0.001), and minute ventilation (4.65 vs. 3.47 L, P<0.001). PEEP was lower in the tubeless group (2.74 vs. 3.20 cmH₂O, P<0.001). FiO₂ and the intraoperative average SpO₂ were comparable between two groups (P>0.05). Intraoperative average EtCO₂ was higher in the tubeless group (33.58 vs. 42.22 mmHg, P<0.01). Intraoperative blood loss showed equal median values across the two groups, yet tubeless group exhibited a smaller IQR [10.00 (10.00, 20.00) vs. 10.00 (5.00, 10.00), P<0.001]. Intraoperative fluid infusion of the tubeless group was less (1,123.68 vs. 1,050.25 mL, P=0.04). The time from surgery completion to airway device removal was shorter in the tubeless group (41.50 vs. 37.42 minutes, P=0.007). Notably, the tubeless group had a 1-day reduction in median postoperative hospital stay (P<0.001), whereas no differences were observed in survival rate (Figure S1).

CT image changes in the non-operative lung

CT image changes in the non-operative lung varied by operative time (Table 3). For surgeries lasting 60–120 minutes, the tubeless group had lower rates of overall changes (15.6% vs. 8.2%, P=0.04) and consolidation (12.6% vs. 5.7%, P=0.03). For surgeries lasting >120–180 minutes, the overall changes were 16.4% in the intubation group versus 10.2% in the tubeless group (P=0.37), with hyperlucency showing higher rates in the intubated group though not statistically significant. In surgeries over 180 minutes, overall changes (33.3% vs. 17.6%) and consolidation (30.0% vs. 17.6%) decresed in the tubeless group, but not statistically significant. Similar to the >120–180-minute group, consolidation rates were higher in the intubated group but did not reach statistical significance. No significant differences were found between groups in the occurrence of pleural effusion or atelectasis.

Factors influencing CT image changes on the non-operative side

Among ventilation parameters, average respiratory rate (OR 1.36, 95% CI: 1.07–1.74, P=0.01) and minute ventilation (OR 1.32, 95% CI: 0.91–1.90, P=0.14) showed the strongest correlation with CT changes. Peak airway pressure (OR 1.06, 95% CI: 1.01–1.12, P=0.03), mean airway pressure (OR 1.15, 95% CI: 0.99–1.35, P=0.07), and plateau pressure (OR 1.08, 95% CI: 1.01–1.16, P=0.03) showed positive associations. Surgical duration demonstrated a small but significant effect (OR 1.01, 95% CI: 1.00–1.02, P=0.007). Other ventilation parameters, including tidal volume (OR 1.00, 95% CI: 1.00–1.01, P=0.72), PEEP (OR 1.05, 95% CI: 0.78–1.43, P=0.73), FiO₂ (OR 1.02, 95% CI: 0.97–1.06, P=0.46), and minute ventilation (OR 1.32, 95% CI: 0.91–1.90, P=0.14) did not show statistically significant associations with CT image changes. Patient age did not demonstrate a significant effect (OR 0.99, 95% CI: 0.96–1.01, P=0.32), and BMI showed a positive but non-significant association (OR 1.07, 95% CI: 0.96–1.19, P=0.24) (Figure 3).

Figure 3 Conditional odds ratios for factors associated with contralateral CT abnormality. BMI, body mass index; CT, computed tomography; InO₂, inspired oxygen concentration; MV, minute ventilation; PEEP, positive end-expiratory pressure; Pmean, mean pressure; Ppeak, peak pressure; Pplat, plateau pressure; RR, respiratory rate; TV, total volume.

Discussion

While postoperative changes in the operative-side lung are anticipated and well-documented, postoperative changes in the non-operative lung have received far less attention (22,23). CT imaging provides a non-invasive method to evaluate postoperative conditions. Despite the substantial number of thoracic surgeries performed at our center each year, many cases did not meet the inclusion criteria for this study. With the help of big data technologies, we were able to identify sufficient eligible cases from our patient database. Our retrospective cohort study demonstrates that tubeless approaches are associated with reduced mechanical ventilation pressures and a lower incidence of non-operative lung imaging abnormalities, thus providing novel insights into the impact of tubeless approaches when compared to traditional intubation approaches.

Mechanical ventilation, while essential in intubated anesthesia, imposes non-physiological positive pressure on lung tissue, potentially causing overdistension of alveoli and airways (24,25). In contrast, spontaneous breathing maintains negative intrathoracic pressure through diaphragmatic descent and intercostal muscle activity, which better facilitates even alveolar expansion and maintains cardiac output (26). These decreases in mechanical forces on the lung tissue were accompanied by gentler ventilation parameters, with lower tidal volumes and reduced minute ventilation. This reduction in mechanical stress parameters suggests that tubeless anesthesia, by allowing spontaneous breathing, may help preserve the natural mechanics of the non-operative lung during surgery.

Lung injury during OLV occurs through multiple mechanisms, including mechanical strain from large tidal volumes, oxidative stress from increased perfusion, and inflammatory responses from surgical manipulation (27-29). Despite the adoption of protective ventilation strategies, some degree of injury appears inevitable, especially in patients with heterogeneous or acutely injured lungs (30,31). In our cohort, patients with higher peak, mean, and plateau pressures showed increased incidence of non-operative lung changes. This relationship between elevated mechanical forces and lung injury provides empirical support for the proposed mechanisms of ventilator-induced damage to the non-operative lung during OLV.

Lung injury during OLV increases progressively with longer exposure times (32). OLV can lead to barotrauma within minutes to hours, depending on the applied mechanical forces and individual patient susceptibility (5,32,33). In shorter surgeries (60–120 minutes), the tubeless approach demonstrated lower rates of consolidation changes, suggesting an effect against lung injury. However, both groups showed progressively increasing injury patterns with longer surgical time, with surgeries exceeding 180 minutes having the highest rates of overall CT abnormalities. While the tubeless group maintained a trend toward lower consolidation even in longer cases, the differences between groups became less significant, indicating that extended surgical duration may overshadow the benefits of anesthesia approach.

It was believed that muscle relaxants and positive pressure ventilation reduce functional residual capacity (FRC) during anesthesia, potentially leading to atelectasis if PEEP is not maintained (34,35). The tubeless approach, which uses minimal or no muscle relaxants, has less impact on diaphragm function and thus better preserves FRC in the non-operative lung. However, in our observations, the incidence of atelectasis was comparable between the tubeless and intubated groups with protective ventilation strategies, suggesting that the tubeless approach did not demonstrate a significant effect against atelectasis formation when compared to well-managed intubated approach.

Limitations of this study should be acknowledged. Although we used PSM to minimize selection bias, as a single-center retrospective study, unmeasured confounding factors may exist. These factors limit our ability to identify other relevant variables with lung injuries. Nevertheless, our findings provide preliminary evidence for the potential advantages of tubeless anesthesia in reducing non-operative lung injury. Future prospective randomized controlled trials would be valuable to further validate these findings and establish causal relationships between anesthesia approaches and non-operative lung injuries.

Conclusions

In conclusion, when compared to intubated anesthesia in thoracic surgeries, the tubeless approach is associated with lower mechanical ventilation pressures and fewer CT imaging alterations in the non-operative lung, which suggests potential correlations with non-operative lung preservation and improved patient recovery outcomes. This not only further highlights the tubeless thoracic surgery’s potential in lung protection but also underscores its advantage in mitigating PPCs. Further prospective and blinded studies are needed to confirm the causal relationship between tubeless anesthesia and reduced non-operative lung injury.

Acknowledgments

The authors acknowledge physiotherapists, nurses involved in the study at The First Affiliated Hospital of Guangzhou Medical University, National Clinical Research Center for Respiratory Disease for their obliging and invaluable support.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1024/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1024/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1024/prf

Funding: This work was funded by R&D Program of Guangzhou National Laboratory (grant No. SRPG22-017) and National Natural Science Foundation of China (grant No. 82300462).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1024/coif). H.L. serves as an unpaid editorial board member of Journal of Thoracic Disease. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study protocol was approved by the institutional ethics committee of The First Affiliated Hospital of Guangzhou Medical University (Ethics Approval No. ES-2025-082-02). Written informed consent was obtained from all patients prior to their inclusion in the study, ensuring that participants were fully aware of the study objectives, procedures, potential risks, and benefits.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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