Evaluation of Recovery Efficacy of Inspiratory Muscle Training After Lobectomy Based on Computed Tomography 3D Reconstruction

Abstract

BACKGROUND:

Progressive resistance inspiratory muscle training is the principle of inspiratory air-flow resistance loading training to restore diaphragm function, increase alveolar compliance, and further improve respiratory function. However, there is a lack of research on the effectiveness of progressive resistance inspiratory training in post-lobectomy rehabilitation and the accurate assessment of lung volumes.

METHODS:

In this study, 79 subjects diagnosed with lung cancer and undergoing thoracoscopic lobectomy were retrospectively analyzed. The subjects were divided into a control group (n = 40) and an observation group (n = 39) according to the different training modalities. The control group received conventional respiratory training. The observation group received progressive resistance inspiratory muscle training based on conventional breathing training. The primary outcome indicators were the following: lung function and lung volume. The secondary outcome indicators were the following: the number of postoperative hospital days, duration of drain retention, and incidence of postoperative pulmonary complications.

RESULTS:

Baseline data on age, sex, body mass index, smoking history, education level, underlying disease, type of pathology, lung cancer stages, surgical site, preoperative lung volume, and preoperative lung function were not statistically different between the 2 groups (P > .05). The subjects in the observation group had median (interquartile range [IQR]) lung volumes at 1 month after surgery (3.22 [3.12–3.37] L vs 3.14 [2.95–3.24] L; P = .031), median (IQR) FEV₁ (2.11 [1.96–2.21] L vs 2.01 [1.81–2.12] L; P = .031), and mean ± SD peak expiratory flow (5.07 ± 0.62 L/s vs 4.66 ± 0.64 L/s; P = .005) were higher than those in the control group. The median (IQR) postoperative hospital stays (5 [4–5] d vs 5 [4–6] d; P = .030) and the median (IQR) chest drain retention times were shorter in the observation group versus the control group (74 [72–96] h vs 96 [84–96] h; P = .02). There was no significant difference in the incidence of postoperative atelectasis (5.1% vs 10.0%; P = .41) and pneumonia (7.7% vs 12.5%; P = .48).

CONCLUSIONS:

Progressive resistance inspiratory muscle training was effective in improving lung volume and lung function, and in reducing the length of hospital stay and chest drain closure time after lobectomy.

Introduction

At present, video-assisted thoracoscopic surgery, is common for the treatment of lung cancer. The procedure has the advantages of less trauma, quicker recovery, and less postoperative pain, but it still affects lung capacity and respiratory muscle strength to a certain extent, causing clinical manifestations in patients such as dyspnea, cough, and lung infection.^1–3 Therefore, it is important to choose an effective rehabilitation method to improve lung function and promote recovery of patients after thoracoscopic lobectomy.⁴ Studies have shown that inspiratory muscle training is widely used in the rehabilitation of various diseases, especially COPD and asthma, and it has been shown to be effective in improving lung function, inspiratory muscle strength, and dyspnea symptoms.^5,6 In contrast to inspiratory training, progressive resistance inspiratory training involves gradually increasing the inspiratory resistance according to the patient's tolerance level, which thus allows the patient's respiratory muscles to gradually adapt to higher loads and thereby increasing the patient's respiratory muscle strength and endurance.⁷ However, there is a lack of research on the effectiveness of progressive resistance inspiratory muscle training in post-lobectomy rehabilitation and the accurate assessment of lung volumes.

In recent years, computed tomography (CT) 3-dimensional (3D) reconstruction techniques have been widely used in the diagnosis of lung diseases and the evaluation of treatment options. Compared with traditional lung volume measurement methods, CT 3D reconstruction technology can generate highly accurate 3D lung models based on lung CT image data without adding an additional radiation dose and assess the change in lung volume by calculating the volume, thus providing a more visual and accurate assessment of lung volume.^8,9 However, the effectiveness of progressive resistance inspiratory training in post-lobectomy rehabilitation has been evaluated mainly on the basis of traditional lung volume measurements, for example, spirometry,¹⁰ which have disadvantages such as complex operation, limited accuracy, and long testing time, and do not provide information on lung morphology. Therefore, we need a more accurate and comprehensive method of lung volume assessment to evaluate the effect of inspiratory muscle training in post-lobectomy rehabilitation. In this context, this study constructed a 3D model of the lung based on 64-row spiral CT to assess the effect of progressive resistance inspiratory muscle training after lobectomy to investigate whether inspiratory muscle training can promote lung volume recovery.

QUICK LOOK.

Current Knowledge

Previously, the effects of inspiratory muscle training on lung function have been assessed mainly based on lung function tests. Few studies have assessed the effect of progressive resistance inspiratory muscle training on lung volume and postoperative rehabilitation after lobectomy based on CT 3D reconstruction.

What This Paper Contributes to Our Knowledge

In this retrospective study, progressive resistance training by using a portable breathing trainer was more effective in improving postoperative lung volumes and lung function in patients undergoing lobectomy compared with conventional breathing training. The duration of chest drain placement and postoperative hospital stay was shorter in patients who underwent progressive resistance inspiratory training compared with conventional breathing training, but there was no statistical difference in the incidence of postoperative complications between the 2 groups.

Methods

In this retrospective, single-center cohort study, we included 79 subjects who underwent thoracoscopic lobectomy in thoracic surgery and had a confirmed diagnosis of lung cancer. Patients from October 2021 to February 2022 were included in the control group and those from March 2022 to September 2022 were in the observation group. Previously, the focus was on a conventional respiratory training program. However, beginning in March 2022, progressive resistance inspiratory muscle training was added to the conventional respiratory training program.

Patients were excluded if they had poor adherence to treatment, were unable to cooperate with the training, did not complete the follow-up 1 month after the procedure (lack of CT data or failure to perform pulmonary function tests), or had other heart or lung conditions that prevented exercise. The project was reviewed and approved by our college's ethics committee (LDYYLL2023-62). The subjects in the control group received conventional respiratory training for 1 month after surgery, and the subjects in the observation group received progressive inspiratory muscle training in addition to conventional breathing training.

Conventional breathing training included the following: effective coughing and coughing training plus abdominal breathing training plus simple respirator training:

1. Effective coughing and sputum coughing training: instruct the patient to cross his or her arms in front of the chest during deep breathing, continuously exhale loudly, and cough out sputum forcefully when it accumulates in the throat; the training process can be supplemented with empty palm tapping or vibration of the chest to expel sputum, the frequency of the exercise is 10 minutes per session, 3 times a day.

2. Abdominal breathing training: instruct the patient to place the left hand on the abdomen and the right hand on the chest, inhale forcefully and deeply, hold the breath for 2–5 s when the abdomen is felt to be raised to the highest point and then exhale slowly through the mouth (at this time, the abdomen is actively inward), the frequency of abdominal breathing exercises is 15–20 minutes each time, 3 times a day.

3. Simple respiratory inspiratory muscle training (model KI-8001, Shanghai Boyi Industrial, Shanghai, China). The patient was instructed to connect the respiratory trainer to the inspiratory tubing, then hold the trainer in one hand while inhaling slowly and forcefully until maximum inspiration with a 5 – 10–s pause. The patient then exhaled slowly, observing the number and rise of the floating balls, adjusting the resistance value according to the individual patient. The maneuver was repeated after the 3 balls had returned to baseline, followed by a 30-set repetition, 3 times a day.

The subjects were guided and monitored on a weekly basis after discharge through follow-up visits by instant messaging (WeChat, Tencent Holdings, Shenzhen, China) or telephone, and the above training program continued until 1 month after surgery.

Subjects in the observation group underwent conventional breathing training plus progressive resistance inspiratory muscle training.

Progressive resistance inspiratory muscle training included the following: 5 d a week during hospitalization, 30 sets twice a day, with 30 s rest every 5 sets. After discharge, follow-up training is supervised 3 d a week in the out-patient clinic until 1 month after surgery. one-to-one training was performed by using a PF810 portable multifunctional pulmonary function instrument (model CS711, Zhejiang Yiliankang Medical Technology, Hangzhou, China), which is equipped with a pressure valve head, and the size of the pressure valve head resistance can be determined by adjusting the size of the machine resistance value. Specific operation included the following: (1) connect the respiratory trainer to the portable spirometer with the USB connection cable; (2) The patient is instructed to use a special nasal clip for pulmonary function training to hold both sides of the nose so that the lips of the mouth completely wrap around the lip contact area of the trainer to avoid air leakage, connect the respiratory trainer to the inspiratory hose, and the patient holds the respiratory trainer with one hand; (3) inspiratory testing was performed to assess the patient's maximum inspiratory pressure and to develop an individualized pulmonary function training plan; (4) on the first postoperative day of training, the resistance value of the respiratory trainer was set to 30% of the maximum inspiratory pressure; (5) a breathing pattern of fast inhalation and slow exhalation with the best effort was used, with one inhalation lasting 2–3 s and a slow exhalation of 4.5 s until the training requirements were met; and (6) then re-evaluate the patient's maximum inspiratory pressure daily and gradually increase the patient's inspiratory resistance value according to the patient's tolerance level, adjusting the resistance value by 5% of maximum inspiratory pressure. If symptoms such as chest tightness, dizziness, or tachycardia occurred during training, then the training was stopped immediately, waiting until the situation returned to normal before continuing the training.

CT images of the subjects before and 1 month after surgery were uploaded to the computer and imported into Mimics 21.0 software (Materialise NV, Leuven, Belgium). The software automatically identified and removed structures except lung parenchyma and trachea through the preset examination threshold, and automatically completed the identification of interlobar fissure, and obtained the reconstructed 3D lung model and quantitative index of lung volume (Fig. 1). Pulmonary function was measured by using cardiopulmonary function devices in strict accordance with quality control requirements for pulmonary function testing. FVC, FEV₁, and peak expiratory flow were measured before surgery, 5 d after surgery, and 1 month after surgery for comparative analysis.

Fig. 1.

Preoperative (A) and 1-month postoperative (B) lung volume measurements based on Mimics 21.0 software.

Statistical analysis was performed by using SPSS Statistics (version 25.0, IBM, Armonk, New York.). An intention-to-treat analysis was performed. Normality of the data was checked by using the Kolmogorov-Smirnov test. Two independent groups of numerical variables were analyzed by using the Student t test or the Mann–Whitney U test, as appropriate. The chi-square test was used for categorical comparisons. Baseline values were compared by using the Student t test. The descriptive level of significance was set at P < .05.

Results

A total of 105 subjects were enrolled. Of these, 50 subjects were initially included in the control group and 10 were unable to complete the final assessment because they did not complete the follow-up. There were 55 subjects in the observation group, of whom 7 dropped out midway through the training and 9 were unable to complete the final assessment because they did not complete the follow-up visits. Therefore, 40 subjects in the control group and 39 subjects in the observation group were included in the final assessment (Fig. 2). The mean ages of the subjects in the control and observation groups were 57.3 years and 56.8 years, respectively. There were 17 men and 23 women in the control group and 21 men and 18 women in the observation group. The mean body mass indexes were 23.9 and 23.4 kg/m² in the control and observation groups, respectively.

Fig. 2.

Flow chart. CT = computed tomography.

There were no significant differences (P > .05) between the 2 groups in terms of age, sex, body mass index, smoking history, education level, history of hypertension, history of diabetes, type of pathology, lung cancer stage, site of surgery, preoperative lung volume, and baseline characteristics of preoperative lung function indicators (FEV₁, FVC, peak expiratory flow) (Table 1). At 1 month after surgery, median (IQR) lung volumes in the observation group (3.22 [3.12–3.37] L vs 3.14 [2.95–3.24] L; P = .031), median (IQR) pulmonary function parameters FEV₁ (2.11 [1.96–2.21] L vs 2.01 [1.81–2.12] L; P = .031), and mean ± SD peak expiratory flow (5.07 ± 0.62 L/s vs 4.66 ± 0.64 L/s; P = .005) were greater than the control group. The median (IQR) postoperative hospital length of stay (5 [4–5] d vs 5 [4–6] d; P = .030) and median (IQR) chest drain retention times were shorter in the observation group than in the control group (74 [72–96] h vs 96 [84–96] h; P = .02). There was no significant difference in the incidence of postoperative atelectasis (5.1% represents the incidence of pulmonary atelectasis in the observation group vs 5.1% represents the incidence of pulmonary atelectasis in the observation group; P = .41) or pneumonia (7.7% represents the incidence of pneumonia in the observation group after surgery vs 12.5% represents the incidence of pneumonia in the control group after surgery; P = .48) (Table 2). Pulmonary function and lung volumes decreased from preoperative baseline to 1 month after surgery in both groups. By 1 month after surgery, the peak expiratory flow in the observation group was closer to baseline values compared with the control group (Fig. 3).

Table 1.

Baseline Data for Both Groups

Table 2.

Postoperative Lung Volumes, Lung Function, and Prognosis in Both Groups

Fig. 3.

Changes in lung function in both groups 1 month after surgery. *P < .05 the observation group versus the control group data at the same time.

Discussion

Lobectomy results in a reduction in the volume of the affected thoracic cavity, and this reduction can affect ventilation and circulation in the remaining lung tissue and may also lead to a reduction in the elasticity of the lung and collapse of the lung tissue. These changes can lead to a variety of respiratory symptoms and can affect the overall function of the lung.¹¹ The expansion of the lung during lobectomy can cause mechanical stress and trauma to the lung tissue, which leads to inflammation, oxidative stress, and cellular damage. This can further contribute to decreased lung function and volume, and potentially increase the risk of postoperative complications such as lung infection or respiratory failure.^12,13 Therefore, postoperative lung function recovery in patients undergoing lung surgery is crucial. In this study, we evaluated the effect of postoperative progressive resistance inspiratory muscle training in subjects undergoing thoracoscopic lobectomy based on the CT 3D reconstruction technique, and verified its effectiveness in increasing lung volume, lung function, and shortening postoperative hospital stay and chest drain retention time.

Currently, CT 3D reconstruction technology is widely used in clinical practice to provide more accurate and comprehensive information on lung structure and function, including lung volume, airway diameter, blood vessel structure, and more.^14,15 The use of CT 3D reconstruction to assess lung volumes in patients with a postoperative lobectomy is a novel approach that has several advantages over conventional methods. CT 3D reconstruction allows rapid and accurate measurement of lung volumes without the limitations of conventional measurement methods. In addition, CT 3D reconstruction is based on an objective representation of lung tissue and is relatively unaffected by external factors and patient cooperation. The combination of pulmonary function testing and CT 3D reconstruction can provide a more comprehensive assessment of the patient's lung condition, which can help improve the clinical diagnosis and guide the next steps of rehabilitation treatment. Overall, the use of CT 3D reconstruction technology for lung volume assessment is an important tool for assessing lung disease and can provide valuable information for patient management and treatment.

Previous studies have shown a correlation between lung volume and lung function, with reduced lung volume after lobectomy being the main cause of reduced lung function in patients.^16–18 The results of this study showed that progressive resistance inspiratory muscle training after lobectomy was effective in improving lung volume and lung function. Compared with the control group, the lung volume and lung function increased in the observation group at 1 month after surgery. The reason for this was that, after lobectomy, the uneven distribution of ventilation in the remaining lung tissue tends to create ventilation dead zones and shunts that affect lung volume, whereas inspiratory muscle training improves the ventilation distribution in the lung, which allows better exchange of oxygen and carbon dioxide, thus increasing lung volume. Inspiratory muscle training improves lung ventilation distribution, which allows for better exchange of oxygen and carbon dioxide, thus increasing lung volume. In addition, the increased load on the remaining lung tissue after lobectomy results in reduced ventilation, whereas progressive inspiratory muscle training increases lung ventilation, which allows the remaining lung tissue to better participate in gas exchange, thereby increasing lung volume.

Also, progressive inspiratory muscle training improves hemodynamics by enhancing respiratory muscle strength and endurance.¹⁹ This increases the surface area of gas exchange and lung volume to improve lung function. Consistent with the present study, previous studies found that postoperative pulmonary rehabilitation improved early lung function and shortened the duration of hospitalization for chest drain retention in subjects after thoracoscopic lobectomy.²⁰ A within-group comparison revealed that lung volume and lung function decreased at 28 d after surgery compared with preoperative levels, and were much less than preoperative levels. This is mainly due to the changes in the thorax caused by the surgery, which reduced the elasticity and compliance of the lung tissue on the affected side, which results in a decrease in lung volume and thus lung function. The study group believes that a longer follow-up period is needed to determine whether lung function can be restored to preoperative levels after a lobectomy.

This study found that the use of a portable respiratory trainer for progressive resistance inspiratory training had advantages over other types of inspiratory muscle training. Subjects could easily grasp the key points of its use, the exercise was simple, and the resistance value could be set according to a physiologic standard (30% of maximum inspiratory pressure) for personalized training. Patients could also observe the training value on the device, which was convenient to control the inspiratory speed and volume. Training adherence was higher with this intervention, which was more conducive to improving postoperative lung function.²¹

Previous studies found that pulmonary rehabilitation 7 d before and > 4 weeks after surgery accelerates the recovery of respiratory function and reduces the duration of chest tube placement and postoperative hospital length of stay.^22,23 Consistent with previous studies, this study found that the duration of chest drain retention and postoperative hospital length of stay was shorter in the observation group than in the control group. Other research has shown that routine perioperative pulmonary function training helps to reduce the incidence of postoperative complications such as pneumonia and atelectasis in subjects with lung cancer.^24,25 In the present study, the incidence of atelectasis and pneumonia in the observation group was 5.1% and 7.7%, respectively, which was slightly lower than that in the control group, but the difference was not statistically significant. It may be related to the small sample size and needs to be further investigated in depth in the follow-up study.

Limitations

Study limitations include a small sample size and retrospective design, and, although the results showed that progressive inspiratory muscle training was effective in the subjects undergoing lobectomy, the reliability and generalizability of the results are thus relatively limited. Also, the relatively short follow-up period of the study limits the assessment of the long-term effects of progressive inspiratory muscle training. Therefore, future multi-center studies are needed with a larger sample size and long-term follow-up to more comprehensively assess and confirm the long-term effects and benefits of progressive inspiratory muscle training in patients undergoing lobectomy.

Despite these limitations, the results of this study are useful as a guide for clinicians. First, the results provide a basis for the development of a rehabilitation program that can be individualized according to the training methods and parameters used in the study to help patients recover lung function and improve lung volumes. Second, the study highlights the importance of early intervention. By starting progressive inspiratory muscle training as early as possible, patients can regain lung function and lung volumes earlier. However, clinicians need to establish a long-term follow-up program with patients to monitor the rehabilitation process and adjust the training program to ensure lasting improvements in lung function and lung volumes.

Conclusions

The changes in lung volume after inspiratory muscle training in patients undergoing lobectomy can be accurately evaluated based on CT 3D reconstruction, which can guide the next step of rehabilitation treatment. Meanwhile, progressive resistance inspiratory muscle training is an effective rehabilitation training method that can improve lung volume and lung function, shorten postoperative hospital length of stay, and chest tube retention time in patients after lobectomy.