Obesity Surgery

, Volume 24, Issue 5, pp 705–711

Long-Term Improvements in Pulmonary Function 5 Years After Bariatric Surgery

Authors

    • Department of Morbid Obesity and Bariatric Surgery, Department of Endocrinology, Obesity and Preventive Medicine, Medical ClinicOslo University Hospital, Aker
  • Sjur Humerfelt
    • Department of Pulmonary Medicine, Medical ClinicOslo University Hospital, Aker
  • Torgeir T. Søvik
    • Department of Gastrointestinal Surgery, Clinic of Surgery, Medical ClinicOslo University Hospital, Aker/Ullevål
  • Erlend T Aasheim
    • Department of Morbid Obesity and Bariatric Surgery, Department of Endocrinology, Obesity and Preventive Medicine, Medical ClinicOslo University Hospital, Aker
  • Hilde Risstad
    • Department of Morbid Obesity and Bariatric Surgery, Department of Endocrinology, Obesity and Preventive Medicine, Medical ClinicOslo University Hospital, Aker
  • Jon Kristinsson
    • Department of Morbid Obesity and Bariatric Surgery, Department of Endocrinology, Obesity and Preventive Medicine, Medical ClinicOslo University Hospital, Aker
  • Tom Mala
    • Department of Morbid Obesity and Bariatric Surgery, Department of Endocrinology, Obesity and Preventive Medicine, Medical ClinicOslo University Hospital, Aker
    • Department of Gastrointestinal Surgery, Clinic of Surgery, Medical ClinicOslo University Hospital, Aker/Ullevål
Original Contributions

DOI: 10.1007/s11695-013-1159-9

Cite this article as:
Hewitt, S., Humerfelt, S., Søvik, T.T. et al. OBES SURG (2014) 24: 705. doi:10.1007/s11695-013-1159-9

Abstract

Background

Obesity is associated with reduced pulmonary function. We evaluated pulmonary function and status of asthma and obstructive sleep apnoea syndrome (OSAS) before and 5 years after bariatric surgery.

Methods

Spirometry was performed at baseline and 5 years postoperatively. Information of asthma and OSAS were recorded. Of 113 patients included, 101 had undergone gastric bypass, 10 duodenal switch and 2 sleeve gastrectomy.

Results

Eighty (71 %) patients were women, mean preoperative age was 40 years and preoperative weight was 133 kg in women and 158 kg in men. Five years postoperatively, weight reduction was 31 % (42 kg; p < 0.001) in women and 24 % (38 kg; p < 0.001) in men. Forced expiratory volume in 1 s (FEV1) increased 4.1 % (116 ml; p < 0.001) in women and 6.7 % (238 ml; p = 0.003) in men. Forced vital capacity (FVC) increased 5.8 % (209 ml; p < 0.001) in women and 7.6 % (349 ml; p < 0.001) in men. Gender and weight loss were independently associated with the improvements in FEV1 and FVC. At follow-up, FEV1 had increased 36 % of the difference towards the estimated normal FEV1, and there was a corresponding 70 % recovery of FVC. These improvements occurred despite an expected decline in pulmonary function by age during the study period. Of the asthmatics and OSAS patients, 48 and 80 %, respectively, were without symptoms 5 years postoperatively.

Conclusions

Pulmonary function measured with spirometry was significantly improved 5 years after bariatric surgery, despite an expected age-related decline during this period. Symptoms of asthma and OSAS also improved.

Keywords

Bariatric surgeryGastric bypassObesityWeight lossPulmonary functionFEV1FVCSpirometryAsthmaObstructive sleep apnoea

Introduction

The prevalence of obesity has increased worldwide in the last decades with a wide impact on morbidity and mortality [16]. Obese people have reduced pulmonary function and increased prevalence of respiratory diseases such as asthma and obstructive sleep apnoea syndrome (OSAS) [46]. Thoracic and abdominal fat accumulation increases thoracic wall stiffness, moves the diaphragm upward, increases intrathoracic pressure and infiltrates the lungs. All these act in concert to reduce pulmonary function [5, 7]. Fat in the pharyngeal region also obstructs the upper airways predisposing to OSAS [46]. In such a context, obesity is associated with impaired pulmonary function [5, 811].

Weight loss studies have shown improvements in pulmonary function [1218]. After bariatric surgery, weight loss is often considerable and sustained, with body weight typically at the lowest 1–2 years after surgery [19, 20]. Studies of pulmonary function have shown outcomes during the first 2 years after bariatric surgery. To our knowledge, this manuscript is the first to report long-term results of pulmonary function measured with spirometry before and 5 years after bariatric surgery.

In this study, we evaluated changes in pulmonary function 5 years after bariatric surgery and possible explanatory factors for these changes. Furthermore, pulmonary function was explored in relation to normal values of the general population, which includes an expected decline in pulmonary function by age. We also report data on self-reported changes in asthma and OSAS.

Materials and Methods

Inclusion

This study was a 5-year follow-up study of pulmonary function including patients who underwent bariatric surgery at the Department of Morbid Obesity and Bariatric Surgery, Oslo University Hospital and who met consecutively for a 5-year follow-up between June 2010 and October 2011. Five years earlier, between June 2005 and October 2006, 140 patients had received bariatric surgery. Of the 125 patients who met for follow-up, 113 (81 % of 140) had performed a valid spirometry before surgery and 5 years postoperatively and were included. Of these, 101 patients had undergone gastric bypass, 10 bilipancreatic diversion with duodenal switch (duodenal switch) and 2 sleeve gastrectomy.

Surgical Procedures

The eligibility criteria for surgery were a body mass index (BMI) ≥40 kg/m2 or BMI ≥35 kg/m2 in patients who had one or more obesity-related comorbidities [20]. A Roux-en-Y gastric bypass was performed by constructing a gastric pouch of about 25 ml, an alimentary limb length of 150 cm and a biliopancreatic limb of 50 cm. In some patients with a BMI ≥50 kg/m2, duodenal switch was applied, with a sleeve gastrectomy along a nasogastric tube of 30–32 F, an alimentary limb of 200 cm and a common channel of 100 cm. Sleeve gastrectomy alone was performed in two patients, one due to ulcerative colitis and one had satisfactory weight loss with sleeve gastrectomy alone in a planned two-step procedure. All procedures were performed laparoscopically as described previously [21].

Measurements and Registrations

At baseline and 5-year follow-up, the patients were weighed with light clothing without shoes on a platform weight, Seca 635, III (0–300 kg). Height was measured standing with a wall-fixed adjustable steel measure. Spirometry was performed with a Jaeger Master Screen Pulmonary Function Test spirometer according to the American Thoracic Society criteria [22]. The spirometer was calibrated twice daily using automatic procedures. All tests were performed by the same laboratory technicians following a standardized procedure with the patients sitting upright using a nose clip and with a minimum forced exhalation time of 6 s after maximum inhalation. The best values of each forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and peak expiratory flow (PEF) from at least three acceptable forced expiration manoeuvres were used for analysis. The FEV1 and FVC values, expressed in litres, were compared with estimated normal values of the general population in Norway [23].

Preoperatively and at the 5-year follow-up, patients were asked about symptoms and current doctors' diagnosis of asthma and OSAS and the use of anti-asthmatic medication and non-invasive ventilation (NIV; CPAP or BiPAP). The information was recorded prospectively on designated 5-year follow-up forms, and medical records were reviewed retrospectively for relevant information of each patient. Smoking status was categorized into never smokers, continuous ex-smokers, continuous smokers and others (“others” refers to patients who had unknown smoking status at baseline or postoperatively and to patients who changed smoking status between baseline and 5-year follow-up). Some of our long-term data 5 years postoperatively have been published previously [24, 25].

Patient data were recorded in a database approved by The Norwegian Data Inspectorate. Each patient allowed the use of their data by signed informed consent.

Statistics

Statistics were performed with SPSS version 15. Student's t test was used for comparisons of continuous variables. Proportions were compared with the chi-square test or McNemar test as appropriate. A two-tailed p value <0.05 was considered significant. Factors assumed to influence the spirometric pulmonary function variables were included in one-way ANOVA and univariate linear regression analyses. These factors were also entered in the multiple linear regression analyses, with stepwise eliminations of non-significant (p > 0.05) variables.

Results

Baseline characteristics are shown in Table 1. Age was lower in women than in men, but BMI did not differ significantly. Weight loss was 42 kg (31 % of total body weight) in women and 38 kg (24 %) in men.
Table 1

Baseline characteristics in morbidly obese patients prior to bariatric surgery (n = 113)

 

All (n = 113)

Women (n = 80)

Men (n = 33)

Age (years)

40

±9

38

±9

43

±10

Height (cm)

172

±10

167

±7

182

±9

Weight (kg)

140

±25

133

±22

158

±22

BMI (kg/m2)

47.4

±6.3

47.3

±6.6

47.7

±5.4

Daily smokers (n, %)

37

33

28

35

9

28

 Cigarettesa

13.3

±7.1

13.0

±7.1

14.0

±7.5

Results are reported as mean ± standard deviation, unless otherwise stated

n numbers, BMI body mass index

aMean number of cigarettes in smokers

Figure 1 illustrates FEV1 and FVC at baseline and 5-year follow-up in women and men separately. FEV1 increased 4.0 % (117 ml; p < 0.001) from 2.91 to 3.02 l in women and 6.7 % (238 ml; p = 0.003) from 3.57 to 3.81 l in men. FVC increased 5.8 % (209 ml; p < 0.001) from 3.63 to 3.84 l in women and 7.6 % (349 ml; p < 0.001) from 4.59 to 4.94 l in men. The changes in FEV1/FVC ratio were very small, with a significant decrease only in women from 0.802 to 0.788 (p = 0.001). In men, there was a small but significant increase in PEF from 513 to 571 l/min (p = 0.021).
https://static-content.springer.com/image/art%3A10.1007%2Fs11695-013-1159-9/MediaObjects/11695_2013_1159_Fig1_HTML.gif
Fig. 1

Mean ± SE forced expiratory volume in 1 s (FEV1; upper figure) and mean ± SE forced vital capacity (FVC; lower figure) in litres in 80 women (black circle) and 33 men (black square) at baseline and 5 years after bariatric surgery

Table 2 describes changes in FEV1 and FVC according to factors assumed to affect pulmonary function. FEV1 improved significantly by percent weight reduction, while FVC improved by percent weight reduction, male gender and a high baseline BMI. We found no differences in the pulmonary function changes between the groups of smoking status. Categories of asthma status did not show differences in the FEV1 and FVC improvements. There were differences in the FEV1 improvements by OSAS status, but this was not found for FVC. Smoking status showed no differences in the pulmonary function changes.
Table 2

Changes in FEV1 and FVC from baseline to 5 years after bariatric surgery in 113 patients by factors thought to influence pulmonary function

 

Number

ΔFEV1 (l)

ΔFVC (l)

Mean

SD

pa

Mean

SD

pa

All patients

113

0.15

0.32

 

0.25

0.37

 

Gender

   

ns

  

0.017

 Men

33

0.24

0.42

 

0.35

0.46

 

 Women

80

0.12

0.27

 

0.21

0.32

 

Preoperative age (years)

   

ns

  

ns

 19–34

39

0.13

0.27

 

0.25

0.32

 

 35–45

41

0.18

0.05

 

0.27

0.05

 

 46–59

33

0.14

0.41

 

0.22

0.47

 

Preoperative height (cm)

   

ns

  

ns

 <1.65

32

0.09

0.23

 

0.18

0.32

 

 1.65–1.75

44

0.20

0.31

 

0.30

0.36

 

 >175

37

0.15

0.40

 

0.25

0.42

 

Preoperative BMI (kg/m2)

   

ns

  

0.041

 35.0–39.9

7

−0.08

0.29

 

−0.01

0.27

 

 40.0–44.9

43

0.12

0.30

 

0.22

0.37

 

 45.0–49.9

24

0.15

0.36

 

0.19

0.37

 

 ≥50

39

0.23

0.31

 

0.37

0.36

 

Weight reduction (%)

   

0.005

  

0.001

 <25

37

0.02

0.27

 

0.08

0.26

 

 25–35

41

0.18

0.31

 

0.28

0.38

 

 >35

35

0.26

0.35

 

0.40

0.39

 

Procedureb

   

ns

  

ns

 Gastric bypass

101

0.14

0.32

 

0.23

0.37

 

 Duodenal switch

10

0.27

0.32

 

0.44

0.29

 

Smoking status

   

ns

  

ns

 Never smokers

26

0.11

0.30

 

0.26

0.36

 

 Continuous ex-smokers

17

0.12

0.31

 

0.20

0.29

 

 Continuous smokers

29

0.18

0.41

 

0.28

0.46

 

 Othersc

41

0.18

0.27

 

0.25

0.34

 

Asthmad

   

ns

  

ns

 No asthma history

86

0.18

0.30

 

0.27

0.34

 

 Resolved asthma

13

0.09

0.46

 

0.11

0.49

 

 Persistent asthma

14

0.06

0.33

 

0.24

0.42

 

OSASd

   

0.027

  

ns

 No OSAS history

88

0.12

0.30

 

0.22

0.35

 

 Resolved OSAS

20

0.31

0.36

 

0.39

0.42

 

 Persistent OSAS

5

0.03

0.35

 

0.14

0.41

 

BMI body mass index, FEV1 forced expiratory volume in 1 s, FVC forced vital capacity, l litre, OSAS obstructive sleep apnoea syndrome, ns not significant

aOne-way ANOVA

bGastric sleeve patients (n = 2) excluded in this analysis

c“Others”; patients with unknown smoking status preand postoperatively, and patients who changed smoking category during the study

dStatus of asthma and OSAS 5 years postoperatively compared with preoperative status

In multivariate regression analyses, weight reduction appeared as the single most important variable predicting the improvements in FEV1 and FVC, with men achieving greater improvements than women. Neither age nor height was associated with the improvements in FEV1 and FVC. The following equations for the improvements in pulmonary function were derived:
$$ \begin{array}{l}\varDelta FEV1\left(\mathrm{l}\right)=0.012\kern-.30em \times \kern-.28em \mathrm{weight}\ \mathrm{loss}\left(\%\right)+0.204\kern-.30em \times \kern-.30em \mathrm{gender}-0.242\hfill \\ {}\varDelta FVC\left(\mathrm{l}\right)=0.015\kern-.35em \times \kern-.30em \mathrm{weight}\ \mathrm{loss}\left(\%\right)+0.247\kern-.30em \times \kern-.30em \mathrm{gender}-0.258\hfill \\ {}\left(\mathrm{gender}=0\ \mathrm{for}\ \mathrm{women}\ \mathrm{and}\ 1\ \mathrm{for}\ \mathrm{men}\right).\hfill \end{array} $$
Figure 2 illustrates change in mean FEV1 and FVC from baseline to 5 years postoperatively (continuous lines) for three categorized age groups (as in Table 2) separately in women and men. The corresponding normal values for the groups studied at each time point are illustrated with broken lines. For all subgroups except in women >45 years and men <35 years, the improvements in FEV1 and FVC were significant (not shown). The improvements in FEV1 and FVC were observed despite a decline in the expected pulmonary function values as the patients became older during the study period (broken lines). The mean estimated decline in pulmonary function during these 5 years was 3.3 % for FEV1 and 2.6 % for FVC, corresponding to values in the range 30–240 ml for FEV1 and FVC depending on age group and gender. On average, there was a 36 % recovery of the difference between FEV1 at baseline and the estimated normal FEV1 at follow-up, and FVC had a corresponding 70 % recovery.
https://static-content.springer.com/image/art%3A10.1007%2Fs11695-013-1159-9/MediaObjects/11695_2013_1159_Fig2_HTML.gif
Fig. 2

Observed changes (continuous lines) in mean ± SE forced expiratory volume in 1 s (FEV1; upper figure) and mean ± SE forced vital capacity (FVC; lower figure) in litres before and 5 years after bariatric surgery in three age groups (19–34, 35–45, and 46–59 years at baseline), and in women (black circle) and men (black square), separately. Corresponding values of expected FEV1 and FVC in the general population at the different age points are also illustrated (broken line) according to age, height and gender

There were also significant improvements in both asthma and OSAS 5 years after surgery (Table 3). Compared with baseline, 48 % of the asthma patients and 80 % of the OSAS patients reported no such symptoms and no need of treatment after 5 years. The reductions in the use of anti-asthmatic medications and non-invasive ventilation were also significant.
Table 3

Asthma and OSAS and treatment before and 5 years after bariatric surgery (n = 113)

 

Baseline

5 years postop

Reduction

n

% of total

n

% of total

%

pa

Asthma

27

23.9

14

12.4

48

<0.001

 With anti-asthmatic medication

25

22.1

13

11.5

48

<0.001

 Number of asthma medicationsb

13

2.2

13

1.4

36

0.001

OSAS

25

22.1

5

4.4

80

<0.001

 NIV

18

15.9

3

2.7

83

<0.001

OSAS obstructive sleep apnoea syndrome, NIV non-invasive ventilation (CPAP or BiPAP)

ap for change in % of total

bMean number of anti-asthmatic medications in persistent asthmatics

Discussion

This study showed long-term improvements in FEV1 and FVC 5 years after bariatric surgery in morbidly obese patients. The improvements were greater in men than in women. The improved pulmonary function was primarily associated with the extent of weight loss and occurred despite the expected age-related decline in the FEV1 and FVC values during the study period. There were also considerable improvements in symptomatic asthma and OSAS, with large proportions of patients reporting less medical treatment for these conditions 5 years postoperatively.

Spirometry

Previous studies of pulmonary function performed within the first 2 years after bariatric surgery have reported improvements in FEV1 and FVC in the range 5–15 %, corresponding to values in the range 190–330 ml for FEV1 and 280–700 ml for FVC [1418]. To our knowledge, this is the first long-term study showing improvements in FEV1 and FVC, which occurred despite an expected age-related decline of these values during the 5 years. As shown, there was an obvious trend towards normalization of FEV1 and FVC compared with the estimated normal values of the general Norwegian population. Consistent with other studies [26], there were very small changes in the FEV1/FVC ratio and PEF.

Asthma and OSAS

Several studies have shown a decrease in the prevalence of asthma and OSAS after weight loss [2732]. We observed that asthma had resolved in 48 % of the asthmatics 5 years postoperatively. Other studies of obese asthmatics have reported remission rates in the range of 40–100 % with weight loss [29, 33]. Data are insufficient to determine whether the improvements in asthma symptoms primarily are due to ventilatory mechanics with relief of pulmonary restriction or other causes, such as airway inflammation and bronchial hyperreactivity [34]. Of our OSAS patients, 80 % experienced remission of their OSAS 5 years postoperatively, which is in accordance with previous bariatric studies [32, 35, 36]. A reduction in the apnoea-hypopnoea index of 26 % per 10 % reduction in body weight has been indicated, with an approximate decrease of 70 % in the apnoea-hypopnoea index after bariatric surgery [36, 37].

Strengths and Limitations

This study provides data of bariatric patients with a high percentage follow-up 5 years postoperatively. The methods of spirometry and measurements of weight and height were standardized with the same procedures both preoperatively and 5 years postoperatively in all patients included. Patients lost to follow-up may have a less weight loss than those who attended [38]. However, given the expected decline in pulmonary function by age, the observed improvements are probably underestimations of the real situation. Measures of expiratory reserve volume and residual capacity would improve our evaluations of restrictive changes.

The doctors' diagnoses of asthma and OSAS in Norway are generally based on spirometry prior to the initiation of anti-asthmatic treatment and polysomnography prior to the initiation of NIV treatment, respectively. The spirometric pulmonary function tests in our study were in general performed without a bronchodilatation test. At follow-up, our study provided information on asthma and OSAS diagnoses based on symptoms and self-reports, without routinely objective measurements. A misdiagnosis of asthma could potentially appear in obese people [39, 40]. However, a population-based study in Norway indicated comparable results between self-reported information of asthma and physician-based diagnoses [41].

Conclusions

Sustained weight loss 5 years after bariatric surgery was associated with improved pulmonary function, expressed by FEV1 and FVC, and with a trend towards normalization. Symptomatic asthma and OSAS also improved significantly.

Conflict of Interest

Jon Kristinsson and Tom Mala received travel support via payments to their institution, given by Covidien and Ethicon Endo-Surgery. Stephen Hewitt, Sjur Humerfelt, Torgeir T Søvik, Erlend T Aasheim and Hilde Risstad did not report any disclosures.

Copyright information

© Springer Science+Business Media New York 2014