Introduction

Postoperative pulmonary complications (PPCs) are highly prevalent complications during the perioperative period, affecting many patients [1, 2]. These complications significantly influence patients’ outcome, prolong hospital stay, and increase perioperative mortality. PPCs, including respiratory infection, pleural effusion, respiratory failure, atelectasis, bronchospasm, pneumothorax and aspiration pneumonitis, can be caused by various factors such as patient health status, surgical trauma and anesthetic effects [3, 4].

PPCs can occur following any type of surgery, but certain surgeries carry higher risk. The incidence of PPCs is particularly high in major abdominal surgery, thoracic surgery, cardiac surgery and spinal surgery, which seriously threatens the perioperative safety of these patients [5, 6]. Previous studies have focused on these high-risk surgeries and identified several independent risk factors for PPCs. However, there still lack of study on PPCs following thoracic surgery, especially on the risk factors for PPCs after pulmonary lobectomy. It is reported that the incidence of PPCs in thoracic surgery can be as high as 20 ∼ 50%, posing a significant threat to patients undergoing high-risk thoracic surgeries [7, 8]. Identifying and mitigating these risk factors is essential for improving outcomes in thoracic patients.

Pulmonary lobectomy is a common surgical treatment for lung diseases such as lung cancer and emphysema. In thoracic surgery, lobectomy involves a large resection range and significant trauma, which can have substantial impacts on pulmonary function [9]. In recent years, video-assisted thoracoscopic surgery (VATS) has been widely applied due to its advantages such as less tissue trauma and enhanced postoperative recovery [10, 11]. However, PPCs are still common following VATS lobectomy. These complications range from mild atelectasis and pneumonia to severe respiratory failure and sepsis, posing a considerable threat to the perioperative safety of patients [5]. Previous studies have shown that advanced age is one of the independent risk factors for PPCs [12]. This may be related to the age-related decline in pulmonary function and immune responsiveness in elderly patients [13]. Age-related physiological changes can lead to a decrease in pulmonary function, weakened immune response, reduced tolerance to surgery, and increased risk of PPCs [21]. This may be due to differences in the study population and surgical type in different studies.

In recent years, obesity has become one of the major global epidemics, affecting the health of individuals worldwide. Previous studies have shown that obesity is closely associated with PPCs [22, 23]. Obese patients often face greater surgical challenges and have poorer postoperative recovery of cardiopulmonary function [24]. According to the WHO standards for Asians, BMI ≥ 28 is considered obese. However, there was no significant statistical difference in the incidence of PPCs between the BMI ≥ 28 group and the BMI < 28 group in the current study. The possible reasons may be that the sample size is still relatively small, or there are differences in the surgical types and the studied population. Clinically, obese patients may have the increased risk of PPCs due to impaired oxygen exchange function, elevated risk of hypoxemia and delayed recovery of cardiopulmonary function. Therefore, preoperative assessment and preparation for obese patients are very importance, with a specific focus on maintaining pulmonary function during the perioperative period.

In previous studies, smoking has been identified as a significant risk factor for the development of PPCs [25, 26]. This study also confirms this point. The harmful substances present in tobacco, including tar and nicotine, have the potential to cause damage to the airway epithelium, leading to a reduction in the airway’s ability to clear debris effectively. This damage results in an increase in mucus production and a decrease in lung compliance, ultimately compromising pulmonary function. Furthermore, smokers exhibit shorter and irregularly shaped cilia on the bronchial epithelium, which impairs mucus clearance and predisposes them to postoperative pulmonary infections [27]. Previous study has shown that patients who continue to smoke within two weeks prior to surgery are at a significantly increased risk of develo** postoperative pulmonary infections compared to those who quit smoking at least two weeks prior to surgery [26]. It suggests that smoking cessation prior to surgery may be a feasible strategy to reduce the risk of PPCs and improve outcomes following thoracic surgery. Unfortunately, the detail information relating whether smoking patients had quitted smoking before surgery could not be obtained in our retrospective electronic records. Prospective studies remain to be conducted to further determine the correlation of smoking cessation and PPCs for smoking patients.

Previous studies have investigated the duration of operation and found that longer operation time is closely related to the increase of pulmonary complications [3, 28]. In addition to studying the duration of operation, this study also includes the duration of OLV intraoperatively. The results showed that the duration of operation and the duration of OLV were significantly associated with PPCs in univariate analysis. However, multivariate analysis showed that only the duration of OLV was the independent risk factor for PPCs, while the duration of operation was not. Since the main surgical steps of pulmonary lobectomy are performed under OLV, it seems to indicate that the longer duration of OLV is one of the main causes of intraoperative potential lung injury and PPCs. OLV is a commonly used lung isolation technique in thoracic surgery. OLV often leads to the significant increase in airway pressure and excessive ventilation pressure. Prolonged higher-pressure ventilation time may cause lung contusion, edema, exacerbation of inflammatory reactions and even cause pulmonary hemorrhage. Besides, previous studies have shown that continuous OLV during surgery produces a large amount of oxygen free radicals and the longer the operation time, the longer the OLV time, and the more oxygen free radicals produced [29]. In addition, the potential damage of OLV includes hypoxemia, atelectasis and pulmonary edema [30]. The quality and duration of intraoperative OLV are mainly related to the anesthetic and surgical techniques. Therefore, it is important to develop a rigorous and meticulous surgical plan before surgery and strengthen team cooperation to minimize the duration of OLV. Pulmonary protection strategies during OLV are also topics that require further exploration in the future.

Previous studies have shown that the effect of postoperative analgesia is correlated with the occurrence of PPCs [31]. Moderate to severe postoperative pain may lead to respiratory restrictions for patients. The pain may make patients unwilling to take deep breaths or cough, which may result in the retention of pulmonary secretions, increasing the risk of atelectasis and pulmonary infection. However, there was no statistically significant difference in postoperative analgesia and VAS scores between the PPCs group and the None-PPCs group in the univariate analysis of this study. One of the possible reasons is that the surgeons have administered additional analgesic drugs to relieve their pain for most patients with moderate to severe pain. Patients who experienced moderate to severe pain on the first day after surgery mostly received good pain management subsequently.

In this study, we collected preoperative pulmonary comorbidities including chronic bronchitis, COPD and asthma. The results of regression analysis showed that COPD is one of the independent risk factors for PPCs. This is consistent with previous studies [32, 33]. Elderly patients over 70 years old who undergo thoracic surgery often have multiple comorbidities. The results demonstrate that pulmonary comorbidities have the closest relationship with PPCs compared to other system comorbidities. This is primarily because patients with pulmonary comorbidities may have poorer baseline pulmonary function. Additionally, surgical trauma, anesthesia and mechanical ventilation can all exacerbate ventilatory and gas exchange dysfunction, as well as affect airway mucosal secretions and expectoration [13]. COPD is a prevalent respiratory disorder that is typically marked by persistent airflow limitation, with main symptoms including chronic cough, sputum production and dyspnea. Due to the impaired pulmonary function in patients with COPD, they face the higher risk of PPCs following surgical procedures [34]. Therefore, there is a close relationship between COPD and PPCs. For patients with COPD, preoperative evaluation and postoperative management are crucial.

There are certain limitations of this study. Firstly, this study is a retrospective study conducted in a single center with a relatively small sample size (322 cases), some uncertainty may exist. Secondly, the time and severity of PPCs were not further stratified. The observation indicators of this study were PPCs within 7 days, while short-term pulmonary complications after discharge were not included. This may affect the statistical analysis of the incidence and risk factors of PPCs. The time and severity of pulmonary complications are important for patient prognosis. We can further collect the detailed time and severity of PPCs for deeper analysis in the future. Thirdly, in terms of case data collection, due to the hospital’s electronic case system constraints, some important clinical examination indicators were not fully collected, so they were not discussed in this study. Further conclusions require multi-center, prospective clinical studies for verification.

Conclusions

In summary, PPCs in elderly patients (≥ 70 years old) who undergo VATS lobectomy are affected by multiple factors. The present study has identified ASA ≥ III, duration of OLV, smoking and COPD as potential independent risk factors for PPCs. The analysis of risk factors for PPCs in high-risk individuals provides valuable and reliable indicators for assessing the risk of these complications. This information can assist in identifying high-risk patients in clinical practice and taking targeted preparations and interventions before surgery to proactively prevent PPCs. It is particularly important to perform rigorous and cautious preoperative assessments, personalized perioperative management and multidisciplinary comprehensive treatment for these high-risk patients.