Factors Affecting a Change in Pulmonary Function Following Laparoscopic Sleeve Gastrectomy: A 1-Year Observational Study

Abstract

Background:

Obesity may lead to impaired pulmonary function because of both the condition itself and its associated comorbidities. The change in pulmonary function following laparoscopic sleeve gastrectomy (LSG) and the factors affecting it were evaluated in our study.

Methods:

A retrospective study was carried out on 61 patients undergoing LSG between January 2014 and January 2015 for morbid obesity (body mass index [BMI] ≥40 kg/m²), who were at least 12 months post-op. Our analysis considered pre- and 12-month postoperative demographic data; the presence of comorbidities; smoking habit; American Society of Anesthesiologists (ASA) scores; weight; BMI values and spirometry results.

Results:

The study comprised 61 cases: 8 men (13%) and 53 women (87%), with a mean age of 36.08 ± 8.47 years. Preoperative and 12-month postoperative values for weight and BMI differed significantly (both p < 0.001). The spirometry results 12 months postoperatively revealed a significant reduction in forced expiratory volume in the first second (FEV1): p < 0.001; an increase in FEV1%: p < 0.001 and reductions in FEV1/forced vital capacity (FVC) and FEV1/FVC% values: p < 0.001 compared with preoperative values. Smoking, ASA scores and the presence of comorbidities were also seen to affect pulmonary function; whereas obesity onset age (childhood or adulthood) showed no impact.

Conclusions:

In morbidly obese patients, weight loss following LSG, the presence of comorbidity, smoking and the ASA score may affect pulmonary function.

Introduction

Morbid obesity is a significant risk factor for type 2 diabetes mellitus, hypertension, cardiovascular and pulmonary diseases and is associated with an increase in morbidity and mortality.¹ With the increasing prevalence of obesity, there has recently been a steady increase in the number of bariatric surgical interventions performed.¹ Morbid obesity is frequently accompanied by comorbidities, causing an increase in perioperative risk during bariatric surgery; however, surgery can provide a cure for obesity and comorbid diseases, thereby reducing mortality in the long term.²

In obese individuals, pulmonary function decreases and the prevalence of respiratory diseases, such as asthma, obstructive sleep apnea syndrome and obesity hypoventilation syndrome increases.^3,4 Morbid obesity is reported to have a greater impact on pulmonary function than would be expected, even in patients without a known pulmonary disorder.^5,6 Increased fatty tissue in the abdominal and thoracic regions leads to an increase in intra-abdominal pressure and limits movement of the thoracic wall and motion of the diaphragm.⁷ The respiratory impairment associated with central obesity is caused by increased intra-abdominal pressure, which pushes up the diaphragm, raises intrathoracic pressure, and compresses the lungs.⁸ As intra-abdominal pressure decreases following bariatric surgery, particularly in patients with marked central or abdominal obesity, an improvement in pulmonary function could also be expected.^9,10

Preoperative pulmonary function tests are not indicated for bariatric surgery candidates without documented pulmonary conditions; although the American Society for Metabolic and Bariatric Surgery has recommended that spirometry be performed during the preoperative period in the presence of risk factors.^11,12 In fact, the value and prognostic importance of pulmonary function tests before and after laparoscopic bariatric surgery remain ambiguous.¹³

Therefore, the aim of this study was to evaluate whether weight loss after laparoscopic sleeve gastrectomy (LSG) procedure in morbidly obese patients had any effect on pulmonary function. If the results showed any change in pulmonary function, a further aim was to determine which other related factors, besides weight loss, were associated with this change.

Materials and Methods

Participants and procedures

Data from 61 patients who underwent LSG for morbid obesity at the University of Medical Sciences, Bursa Y.I. Teaching and Research Hospital, Turkey between January 2014 and January 2015 and who completed 12 months of follow-up was retrospectively assessed. The patients enrolled in the study were aged 20–60 years, had a body mass index (BMI) ≥40 kg/m², and were considered suitable for laparoscopic surgery. Preoperative assessment by a pulmonologist excluded patients with acute or chronic pulmonary disease or previous thoracic surgery, or those who had not undergone (or had not wished to undergo) a respiratory function test, as well as patients with previous bariatric surgery. All procedures were conducted in accordance with the ethical standards of the 1964 Declaration of Helsinki and its later amendments; written informed consent was obtained from all participants; and the study was approved by the local ethics committee of Bursa Y.I. Training and Research Hospital.

Evaluation methods and diagnostic techniques

The following data was recorded for each patient: demographic data; the presence of comorbidities obesity onset age (childhood or adulthood); smoking habit (smoker or nonsmoker); American Society of Anesthesiologist (ASA) score; preoperative and postoperative 12-month weight; and BMI data. Pulmonary function test data was also recorded: forced expiratory volume in the first second (FEV1), FEV1%, forced vital capacity (FVC), FVC%, FEV1/FVC and FEV1/FVC% values. Obesity onset age was investigated preoperatively, with the patients divided into two: childhood or adult onset age. Those who smoked during the preoperative 12-month period were defined as smokers; whereas those who had quit smoking 12 months before the operation and those who had never smoked were defined as nonsmokers. Respiratory function values were compared to other parameters.

The patients were assessed during the preoperative period by a team consisting of endocrinologist, psychiatrist, general surgeon and pulmonologist. Spirometry was performed using a computerized spirometer (Spirothor Wavefront), with the patient in a sitting position and using a nose clip. The patient performed at least three forced expiratory maneuvers that met the acceptability and reproducibility criteria required by the current recommendations of the American Thoracic Society/The European Respiratory Society statement, and the best of the three calculations was selected.¹⁴ In Turkey, we routinely use equations formulated for Caucasian (white) people, in accordance with the European Respiratory Society's recommendations. The spirometry used here utilizes the patient's age, sex, height and weight in the calculations.

All LSG procedures were performed by the same surgeon. Operations were conducted in the Lloyd Davies position and no cases required transition to open surgery. All patients received low molecular weight heparin (enoxaparin) subcutaneously to prevent deep vein thrombosis and wore pneumatic compression stockings. All patients were administered a fluid diet before the operation; during the postoperative period, the fluid diet was restarted following gas discharge. Patients who tolerated oral intake and developed no morbidity were discharged 4 days after operation. Patients underwent weight monitoring at 1, 3, 6 and 12 months, with the spirometry and biochemical tests repeated at 12 months.

Statistical analysis

Statistical analyses were performed using IBM SPSS for Windows version 21.0 (IBM Corp., Armonk, NY). The distribution of continuous numerical variables was assessed using histograms and the Shapiro–Wilk test. Continuous numerical variables of mean, standard deviation (SD) and range and categorical variables of number of cases and percentage were used. The Wilcoxon test for paired samples was used to compare the mean values of preoperative and postoperative FEV1, FEV1%, FVC, FVC%, FEV1/FVC and FEV1/FVC%. Paired and independent samples t tests were used to compare the mean values of the other parameters. Pearson correlation analysis was applied to continuous numerical variables. Linear regression was performed to establish the relationship between variables, with the F-test for the significance of the model and the t-test for the significance of the model coefficients used in the regression significance tests. Results were considered statistically significant if the p-value was <0.05. To adequately address variables separately, multivariate analyses were performed for the changes in BMI, FEV1 and FEV1/FVC.

Results

The study comprised 61 cases: 8 men (13.1%) and 53 women (86.9%) with a mean age of 36.08 ± 8.47 years. Table 1 presents their demographic data, the presence of comorbidities, obesity onset, smoking status and ASA scores. Seven patients (11.47%) suffered from hypertension and six had type 2 diabetes mellitus (9.83%); with four patients (6.55%) suffering from both these comorbidities. Childhood onset obesity was recorded in 37 patients (60.7%) and adult onset in 24 patients (39.3%). Forty-six patients were nonsmokers or ex-smokers (75.4%) on the other hand 15 (24.6%) patients were current smokers. During the follow up period of 1 year, none of the nonsmokers or ex-smokers started smoking and two patients in the current smoking group quit smoking.

Table 1.

Demographics, Comorbidity, Obesity Onset, Smoking and the American Society of Anesthesiologist Scores

Age
Male/Female	38.38 ± 7.28/35.68 ± 8.65
Gender
Male/Female, n (%)	8 (13.1)/53(86.9)
Comorbidity
(−)/(+), n (%)	44 (72.1)/17 (27.9)
Obesity onset
Childhood, n (%)	37 (60.7)
Adulthood, n (%)	24 (39.3)
Smoking
(−)/(+), n (%)	46 (75.4)/15 (24.6)
ASA
1/2, n (%)	27 (44.3)/34 (55.7)

ASA, American Society of Anesthesiologist.

Changes in weight and BMI, which were measured preoperatively and 12 months postoperatively, along with respiratory function values, are presented in Table 2. A comparison of the pre- and postoperative values revealed statistically significant differences in weight and BMI (both p < 0.001). Compared to the preoperative period, spirometry at 12 months showed a reduction in FEV1 (p < 0.001), an increase in FEV1% (p < 0.001), an increase in FVC (p < 0.001), an increase in FVC% (p < 0.001) and reduction in the FEV1/FVC and FEV1/FVC% values (p < 0.001).

Table 2.

Weight, Body Mass Index and Spirometry Data Obtained Preoperatively and at Postoperative 12 Months

	Preoperative period	Postoperative period (12th month)	p
kg	131.82 ± 19.97	81.57 ± 16.01	<0.001
BMI	48.05 ± 6.17	29.73 ± 5.38	<0.001
FEV1	3.26 ± 2.76	3.18 ± 0.56	<0.001
FEV1%	94.3 ± 15.2	104.5 ± 11.63	<0.001
FVC	3.18 ± 0.67	3.56 ± 0.65	<0.001
FVC%	86.2 ± 14.28	98.45 ± 10.93	<0.001
FEV1/FVC	93.91 ± 7.52	89.5 ± 5.13	<0.001
FEV1/FVC%	108.21 ± 7.43	106.5 ± 6.21	<0.001

BMI, body mass index; FEV1, forced expiratory volume in first second; FVC, forced vital capacity.

The correlations between pre- and post-op respiratory function test results and smoking, comorbidity, ASA scores and obesity onset data are presented in Tables 3 and 4.

Table 3.

Correlation Between Spirometry Results and Smoking, Comorbidity

	Preoperative period	Postoperative period (12th month)	p
Smoker (n = 15)
FEV1	2.9 ± 0.58	3.21 ± 0.61	<0.001
FEV1%	93.5 ± 15.13	105.9 ± 11.41	<0.001
FVC	3.14 ± 0.7	3.59 ± 0.7	<0.001
FVC%	85 ± 15.03	99.9 ± 10.52	<0.001
FEV1/FVC	93.6 ± 0.61	89.3 ± 4.79	<0.001
FEV1/FVC%	108.1 ± 7.88	106.2 ± 5.82	0.241
Nonsmoker (n = 46)
FEV1	4.31 ± 5.41	3.11 ± 0.42	0.382
FEV1%	96.7 ± 15.67	100.26 ± 11.62	0.206
FVC	3.29 ± 0.57	3.47 ± 0.51	0.083
FVC%	89.4 ± 11.87	94 ± 11.34	0.015
FEV1/FVC	94.7 ± 10.02	89.9 ± 6.19	0.127
FEV1/FVC%	108.4 ± 6.26	107.4 ± 7.39	0.751
Comorbidity (−) (n = 44)
FEV1	3.5 ± 3.18	3.32 ± 0.49	<0.001
FEV1%	96.28 ± 15.47	105.45 ± 12.65	<0.001
FVC	3.33 ± 0.63	3.7 ± 0.58	<0.001
FVC%	88.5 ± 13.7	96.31 ± 11.38	<0.001
FEV1/FVC	93.6 ± 8.35	89.75 ± 5.29	<0.001
FEV1/FVC%	107.7 ± 7.37	106.65 ± 6.31	<0.001
Comorbidity (+) (n = 17)
FEV1	2.6 ± 0.51	2.81 ± 0.6	0.040
FEV1%	88.71 ± 13.30	101.87 ± 7.95	0.006
FVC	2.77 ± 0.63	3.17 ± 0.7	0.015
FVC%	79.1 ± 13.8	96.06 ± 9.52	0.003
FEV1/FVC	94.7 ± 4.65	88.8 ± 4.72	0.002
FEV1/FVC%	109.5 ± 7.75	106.25 ± 6.11	0.285

Table 4.

Correlation Between Spirometry Results American Society of Anesthesiologist Scores and Obesity Onset

	Preoperative period	Postoperative period (12th month)	p
ASA 1 (n = 27)
FEV1	3.14 ± 0.63	3.34 ± 0.55	0.003
FEV1%	100.6 ± 0.21	106.8 ± 0.89	0.009
FVC	3.38 ± 0.73	3.73 ± 0.63	<0.001
FVC%	91.7 ± 11.27	100.7 ± 10.22	<0.001
FEV1/FVC	95.6 ± 6.87	89.7 ± 5.02	<0.001
FEV1/FVC%	109 ± 6.73	106.4 ± 6.03	0.183
ASA 2 (n = 34)
FEV1	3.35 ± 3.7	3.05 ± 0.55	0.635
FEV1%	88.5 ± 16.87	102.5 ± 12.02	<0.001
FVC	301 ± 0.58	3.43 ± 0.65	<0.001
FVC%	81 ± 15.03	96.5 ± 11.28	<0.001
FEV1/FVC	92.4 ± 7.83	89.3 ± 5.28	0.060
FEV1/FVC%	107.4 ± 8.07	106.6 ± 6.44	0.689
Obesity onset
FEV1	3.51 ± 3.48	3.17 ± 0.49	0.546
FEV1%	96.2 ± 14.6	105.5 ± 11.57	<0.001
Childhood (n = 37)
FVC	3.22 ± 0.68	3.53 ± 0.58	<0.001
FVC%	88.1 ± 14.22	99.2 ± 11.07	<0.001
FEV1/FVC	93.9 ± 6.78	89.9 ± 4.98	0.005
FEV1/FVC%	107.4 ± 6.68	106.8 ± 5.9	0.802
Obesity onset
FEV1	2.86 ± 0.57	3.21 ± 0.67	<0.001
Adulthood (n = 24)
FEV1%	91.5 ± 15.9	102.8 ± 11.79	<0.001
FVC	3.1 ± 0.66	3.61 ± 0.78	<0.001
FVC%	83.1 ± 14.16	97.7 ± 10.8	<0.001
FEV1/FVC	93.8 ± 8.74	88.8 ± 5.41	0.015
FEV1/FVC%	109.4 ± 8.47	106 ± 6.66	0.146

Nonsmokers showed statistically significant increases in FEV1, FEV1%, FVC and FVC% (all p < 0.001) and a statistically significant reduction in FEV1/FVC (p < 0.001; Table 3). However, for smokers the only statistically significant increase was in FVC% (p = 0.015).

At 12 months postoperatively, the patients with comorbidity showed increases in FEV1, FEV1%, FVC and FVC% values (p = 0.04, p = 0.006, p = 0.015 and p = 0.003, respectively) and a reduction in FEV1/FVC (p = 0.002; Table 3). However, there was no statistically significant change in FEV1/FVC% (p = 0.285). On the other hand, patients without comorbidity showed reductions in FEV1, FEV1/FVC and FEV1/FVC% (all p < 0.001) and an increase in FEV1%, FVC and FVC% (all p < 0.001). When comparing the preoperative spirometry results of the comorbidity subgroups, patients with no comorbidities had significantly higher FEV1, FVC and FVC% values (p = 0.03, p = 0.004 and p = 0.031, respectively); while 12 months postoperatively, the patients without any comorbidity had significantly higher FEV1 and FVC values (p = 0.002 and p = 0.005, respectively).

ASA 1 patients showed significant increases in FEV1, FEV1%, FVC and FVC% values (p = 0.003, p = 0.009, p < 0.001 and p < 0.001, respectively) and a reduction in the FEV1/FVC value (p < 0.001; Table 4). In ASA 2 patients, FEV1%, FVC and FVC% increased (all p < 0.001). A comparison of the spirometry values between the ASA 1 and ASA 2 patients showed that FEV1%, FVC and FVC% were significantly higher in the ASA 1 patients in the preoperative period (p < 0.001, p = 0.03 and p = 0.004, respectively), but only FEV1 was significantly higher in the ASA 1 patients postsurgery (p = 0.049).

With regard to the onset of obesity, childhood onset patients showed significant increases in FEV1%, FVC and FVC% (all p < 0.001) and a reduction in FEV1/FVC (p = 0.005; Table 4). Meanwhile, in adulthood onset patients FEV1, FEV1%, FVC and FVC% all increased (all p < 0.001) and FEV1/FVC decreased (p = 0.015).

In addition, female patients had higher FEV1%, FVC% and FEV1/FVC values than male patients during the preoperative period (p = 0.03, p = 0.039 and p = 0.028, respectively). However, during the postoperative period, the male patients were observed to have higher FEV1 and FVC (p = 0.02 and p = 0.02, respectively), with the female patients having higher FEV1/FVC (p = 0.04).

The change in FEV1 12 months after the operation correlated with the change in BMI (R² = 0.115, SD ±0.066, p = 0.038). Also, linear regression analysis showed a relationship between the ASA score and the difference in FEV1/FVC that was close to statistical significance (R² = 0.10, SD ±2.45, p = 0.057); with a higher sample size, we believe that statistical significance could have been achieved. A history of smoking and the presence of comorbidities were both associated with a lower difference in BMI at 12 months (smoking: R² = 0.290, SD ±1.01, p = 0.007; and comorbidity: R² = 0.290, SD ±1.54, p = 0.013).

Discussion

This study clearly demonstrated the effect smoking can have on the change in pulmonary function 12 months after LSG. After 1 year, the nonsmokers showed statistically significant increases in FEV1, FEV1%, FVC and FVC% values (all p < 0.001); with smokers showing a statistically significant increase only in the FVC% value (p = 0.015). Mannino et al. reported in the U.S. National Health and Nutrition Examination Survey I that current smokers have an increased risk for spirometric restriction (reduced FVC in the absence of airflow obstruction) compared to nonsmokers, but that former smokers had no increased risk; while associations with cumulative smoking (pack-years) were not reported.¹⁵ Undoubtedly, tobacco use should be avoided at all times by all patients; but, in particular, patients about to undergo bariatric surgery should give up smoking at least 6 weeks pre-op. In addition, tobacco use should be completely avoided after bariatric surgery, given the increased risk of poor wound healing, anastomotic ulcer and overall health impairment.¹⁶ We believe that evaluating smoking habits among patients who are scheduled for obesity surgery and encouraging current smokers to quit before the operation would lead to a more marked improvement in pulmonary function following surgery.

Evaluating the effect of comorbidity on pulmonary function, we observed that patients without any comorbidity had significantly higher preoperative FEV1, FVC and FVC% values than those with comorbidity (p = 0.03, p = 0.004 and p = 0.031, respectively). However, the postoperative FEV1 and FVC values were significantly higher in the group with comorbidities (p = 0.002 and p = 0.005, respectively). Although there have been studies on comorbidity resolution following bariatric surgery, data on the effect of comorbidities on pulmonary function after LSG are quite limited.^17,18 The LSG procedure used in our study is reported to be an increasingly popular method for the management of obesity with restrictive and hormonal effects, delivering effective weight loss, along with the resolution of comorbidities.^17,19,20

In the literature, data on the relationship between ASA scores and changes in pulmonary function following LSG are limited. In our study, we found that FEV1%, FVC and FVC% values were significantly higher in ASA 1 patients than in ASA 2 patients during the preoperative period (p < 0.001, p = 0.03 and p = 0.004, respectively); and, similarly, during the postoperative period, FEV1 in ASA 1 patients was significantly higher (p = 0.049). This difference, shown in ASA scores that are directly associated with comorbidities, suggests that comorbidities affected the change in pulmonary function.^17,18

On the other hand, the age of obesity onset had no significant effect on spirometry results during the preoperative or postoperative periods. This may be partly because of the relatively small number of cases in our trial. In fact, very few studies have tracked changes in body weight from childhood to adulthood, investigating correlations between these periods.^21–23 Reports have shown that physical activity from 17 to 25 years of age is important in preventing obesity²¹ and, conversely, that reduced physical activity during this transition from childhood to adulthood is an important cause of obesity.²⁴ However, there have been no previous studies showing a correlation between the time of obesity onset and changes in pulmonary function.

Although FEV1%, FVC and FVC% increased during the postoperative period in our study, we did observe reductions in FEV1, FEV1/FVC and FEV1/FVC%. In addition, after a year we detected significant increases in FEV1% from 94.3% to 104.5% and in FVC from 86.2% to 98.45%. This supports the literature, suggesting that an improvement in pulmonary functions such as FEV1 and FVC may follow effective weight loss after bariatric surgery.²⁵ Additionally, in this study, the decline in FEV1 12 months after surgery is a new finding worthy of attention; although, a possible reason for this interesting result may have been the size of our study cohort, which was smaller than those of previous studies. Further studies are needed to evaluate this association.

In our study, we observed a more marked improvement in pulmonary function among the male patients (FEV1 p = 0.02, FVC p = 0.02). Surgically induced weight loss is associated with a marked increase in all lung volumes, most dramatically in residual lung volüme.²⁶ Reports show that obese patients who are male and over 40 years of age exhibit a greater loss in pulmonary function, with significantly reduced FVC and FEV1/FVC values.²⁷ By reducing FEV1 and FVC levels, weight gain seems to lead to more marked pulmonary dysfunction in male patients.^27,28

Clearly, obesity increases the risk of morbidity and mortality, and patients can experience significant medical and physiological comorbidities.²⁹ Bariatric surgical procedures are indicated in the case of clinically severe obesity, providing effective and sustainable weight control and the resolution of comorbidities.³⁰ Indeed, none of our cases developed pulmonary complications during the postoperative period.

The main limitation of our study is the relatively small number of cases. In addition, it is a single-center study and retrospective in design.

Conclusion

In this study, the loss of excess weight, the presence of comorbidities, a smoking habit and the patient's ASA scores were seen to affect the change in pulmonary function following LSG. In the absence of any comorbidity, patients classified as ASA 1 and nonsmokers showed a more marked improvement in pulmonary function. On the other hand, the age of the onset of patient obesity (childhood or adulthood) was not observed to affect pulmonary function. The weight loss in morbidly obese patients following LSG affected the improvement in FVC and FVC% values. Well-planned, prospective studies with a larger sample size are needed to demonstrate the effect of comorbidity, smoking and ASA score on pulmonary function.

Footnotes

Author Disclosure Statement

No competing financial interests exist.

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