Comparison of Postoperative Respiratory Function Between Patients After Thoracoscopic and Open Lobectomy

Introduction

Surgical resection is generally performed in patients with congenital lung disease (CLD) to prevent recurrent respiratory infection and malignant transformation ¹ and in cases of existing malignancy. ² However, no consensus on the timing of the procedure has been reached yet. Various factors, such as technical difficulties in performing procedures in neonates, presence of previous infections, ³ or compensatory growth of the residual lung, must be considered to determine the best timing of surgical intervention. From the perspective of residual lung function, surgical intervention before the age of 1 year is recommended because the values of pulmonary function test were better in the group of patients operated during the first year of life ⁴ and emphysematous change of the remaining lung, which was not an ideal status as compensatory lung growth by alveolar proliferation, was shown on radionuclide imaging when the surgery was performed at the age of 1 year or older. ⁵ On the other hand, no correlation was identified between age at lobectomy and postoperative respiratory function. ⁶

The thoracoscopic approach has gained popularity due to its safety and feasibility. The group from Hong Kong showed that mid-term pulmonary function of cases after thoracoscopic lobectomy (TS) was comparable to that of the normal control, ⁷ and the long-term pulmonary function after TS was better than that of the open group. ⁸ However, little is known about the effects of minimally invasive approach on postoperative pulmonary function because studies are scarce regarding this topic.

Therefore, this study aimed to compare respiratory functions of patients after TS with those after thoracotomy (TR).

Materials and Methods

This retrospective observational study was conducted at two centers, one of which (Saitama Children's Medical Center; 2022-03-003) adapted TS as a standard procedure in 2009 and the other (National Center for Child Health and Development; 2022-175) performs it via TR. The data on patients who underwent lobectomy for CLD between January 2009 and October 2021 and underwent pulmonary function test (spirometry) were collected. The test was recommended to patients whose age was 6 years or older and who were judged as being able to follow instructions during the test by outpatient clinicians. Cases with extra lobar sequestration and those who were treated by segmentectomy or wedge resection were not included in this study. Prenatally diagnosed cases which required surgical intervention immediately after birth due to respiratory distress were also excluded.

Patients' personal information including sex, histological and prenatal diagnoses, age and weight at the time of the procedure, duration of the procedure, length of hospital stay (all cases were discharged from the hospitals after removal of chest tubes), pathological diagnoses, resected lung lobe, age at respiratory function test, and the results of the test such as the ratio of forced vital capacity compared to predicted one (%FVC) and the ratio of forced expiratory volume in 1 second against predicted (FEV1.0%) were extracted from the medical records and compared between the patients who underwent TS (group TS) and those who underwent TR (group TR). Regarding parameters of pulmonary test, each value less than 80% of predicted one was regarded as abnormal.^7,8

Statistical analysis was performed using Steel–Dwass method for multiple nonparametric comparisons and Fisher's exact test for contingency tables using commercially available software (JMP Pro 11.0.0; SAS Institute Japan Ltd., Tokyo, Japan). Statistical significance was set at P < .05. All data are shown as median (interquartile range).

This study was approved by the research ethics committee of National Center for Child Health and Development and Saitama Children's Medical Center, and the requirement for written informed consent was waived because of the retrospective nature of this study.

Results

Table 1 shows patient characteristics and the results of pulmonary function test. We enrolled a total of 46 patients: 10 in group TS and 36 in group TR. Male patients accounted for around 40% in both groups with no significant difference. The ratio of patients with prenatal diagnosis in TS and TR groups was 10% and 22%, respectively, but no significant difference was found between the two groups. Distribution of pathological diagnosis and resected lobe was similar between the two groups. The median [interquartile interval] age at procedure in the TR group was significantly smaller than that in the TS group (TR: 13 [11–18] months versus TS: 38 [13–79] months, P = .03), but there was no significant difference in the weight at procedure (TR: 9.1 [8.3–11.0] kg versus TS: 13.9 [9.0–18.1] kg, P = .07). The procedure time in the TR group was significantly shorter than that in the TS group (230 [171–264] minutes versus 264 [226–420] minutes, P = .02). No conversion to open TR was reported in the TS group.

Table 2 shows the results of pulmonary function test. The test was conducted at the age of eight in both groups, but the interval between the procedure and the test was significantly shorter in the TS group (TR: 7 [5–8] years versus TS: 5 [2–7] years, P = .03). There was no significant difference in the ratio of %FVC (TR: 86.6 [76.6–95.3] versus TS: 88.7 [86.8–89.1], P = .58) and the ratio of FEV1.0% (TR: 84.0 [80.5–88.7] versus TS: 88.7 [86.8–89.1], P = .08) between the two groups.

Discussion

This retrospective observational study showed no difference in the results of postoperative pulmonary test between patients who underwent TS and those who underwent open resection. Although the procedure time was longer in the thoracoscopic group, its shorter length of hospital stays, and the noninferiority of postoperative respiratory function justify encouraging pediatric surgeons to perform TS for CLD.

The results of pulmonary test of the TS group were within normal limits, which are consistent with those of a previous study. ⁷ However, this study showed no superiority of minimally invasive approach on postoperative respiratory function compared to lobectomy via TR. Long-term musculoskeletal sequelae after TR, such as rib fusion, scoliosis, and winged scapula, has been pointed out, ⁹ and these restrictive impairments might worsen the outcomes of pulmonary function test in the open group and showed significant differences in the long run compared to the thoracoscopic group. ⁸

The age at procedure was older in the TS group (38 months) than that in the TR group (13 months). The primary reason for this would be because more cases without prenatal diagnosis, whose disease tend to be identified after pulmonary infection and undergo surgery later than antenatally diagnosed cases, were included in the TS group. Although our treatment strategy for cases with CLD being prenatally diagnosed and asymptomatic after birth is to plan an elective thoracoscopic approach between 6 and 12 months of age, ³ and the discrepancy in antenatal diagnosis between the two groups resulted in the difference in the timing of surgical intervention. Regarding the ratio of prenatal diagnosis, cases which required surgical intervention immediately after birth due to respiratory distress were excluded from this study. This might have resulted in the low values in both groups.

Alveolar proliferation, which mainly contributes to compensatory change of residual lung, continues until the age of eight. ¹⁰ In this study, procedures were performed before the completion of lung growth leaving the time for residual lung growth; however, as previously mentioned, the interval between the procedure and the pulmonary test, which was performed at the age of eight, was significantly shorter in the TS group than that in the TR group due to the aforementioned difference in timing of the procedure. If the patients in the TS group could undergo surgery earlier, better outcomes might be seen as they could have a longer time for compensatory residual lung growth.

This study has some limitations. The number of patients included in this analysis was small, and the data were collected retrospectively from only two institutions. Moreover, each institution performed a specific approach, one with only minimally invasive surgery and the other with only TR, and various surgeons were in charge of procedures. These issues might have introduced bias into the outcomes of this study. The length of stay after the procedure was longer than that reported in the literature because of the cultural difference in medical treatment between other countries and Japan. Patients are discharged from hospitals after complete recovery from surgeries and this unique Japanese style could have affected the results.

Despite these limitations, this study showed that respiratory function after TS was similar to that after open lobectomy, even though the interval between the procedure and the test was shorter in the thoracoscopic group than that in the TR group. A future study, in which this background is matched between the two groups, might prove the positive impact of minimally invasive procedure on postoperative pulmonary function.