The effects of mild obesity on lung function

Bioelectrical impedance and lung function-associations with gender and central obesity: results of the EpiHealth study

BACKGROUND

Obesity is a major public health concern associated with various health problems, including respiratory impairment. Bioelectrical impedance (BIA) is used in health screening to assess body fat. However, there is no consensus in healthcare on how body fat should be assessed in relation to lung function. In this study, we aimed to investigate how BIA in relation to waist circumference contribute, using data from a large Swedish population study.

METHODS

A total of 17,097 participants (aged 45-75 years) were included in the study. The relationships between fat mass, waist circumference, and lung function were analysed using weighted quantile sum regression.

RESULTS

Increased fat mass was significantly associated with decreased lung function (FEV1, FVC) in both sexes. Also, the influence of trunk fat and waist circumference on FVC and FEV1 differed by sex: in males, waist circumference and trunk fat had nearly equal importance for FVC (variable weights of 0.42 and 0.41), whereas in females, trunk fat was significantly more important (variable weights 0.84 and 0.14). For FEV1, waist circumference was more important in males, while trunk fat was more significant in females (variable weights male 0.68 and 0.28 and 0.23 and 0.77 in female).

CONCLUSIONS

Our results suggest that trunk fat should be considered when assessing the impact of adipose tissue on lung function and should potentially be included in the health controls.

Predictive Roles of Basal Metabolic Rate and Muscle Mass in Lung Function among Patients with Obese Asthma: A Prospective Cohort Study

BACKGROUND

The metabolic-status-related mechanisms underlying the deterioration of the lung function in obese asthma have not been completely elucidated.

OBJECTIVE

This study aimed to investigate the basal metabolic rate (BMR) in patients with obese asthma, its association with the lung function, and its mediating role in the impact of obesity on the lung function.

METHODS

A 12-month prospective cohort study (n = 598) was conducted in a real-world setting, comparing clinical, body composition, BMR, and lung function data between patients with obese (n = 282) and non-obese (n = 316) asthma. Path model mediation analyses for the BMR and skeletal muscle mass (SMM) were conducted. We also explored the effects of the BMR on the long-term lung function in patients with asthma.

RESULTS

Patients with obese asthma exhibited greater airway obstruction, with lower FEV1 (1.99 vs. 2.29 L), FVC (3.02 vs. 3.33 L), and FEV1/FVC (65.5 vs. 68.2%) values compared to patients with non-obese asthma. The patients with obese asthma also had higher BMRs (1284.27 vs. 1210.08 kcal/d) and SMM (23.53 vs. 22.10 kg). Both the BMR and SMM mediated the relationship between obesity and the lung function spirometers (FEV1, %FEV1, FVC, %FVC, and FEV1/FVC). A higher BMR or SMM was associated with better long-term lung function.

CONCLUSIONS

Our study highlights the significance of the BMR and SMM in mediating the relationship between obesity and spirometry in patients with asthma, and in determining the long-term lung function. Interventions for obese asthma should focus not only on reducing adiposity but also on maintaining a high BMR.

Pulse oximetry values from 33,080 participants in the Apple Heart & Movement Study

Wearable devices that include pulse oximetry (SpO₂) sensing afford the opportunity to capture oxygen saturation measurements from large cohorts under naturalistic conditions. We report here a cross-sectional analysis of 72 million SpO₂ values collected from 33,080 individual participants in the Apple Heart and Movement Study, stratified by age, sex, body mass index (BMI), home altitude, and other demographic variables. Measurements aggregated by hour of day into 24-h SpO₂ profiles exhibit similar circadian patterns for all demographic groups, being approximately sinusoidal with nadir near midnight local time, zenith near noon local time, and mean 0.8% lower saturation during overnight hours. Using SpO₂ measurements averaged for each subject into mean nocturnal and daytime SpO₂ values, we employ multivariate ordinary least squares regression to quantify population-level trends according to demographic factors. For the full cohort, regression coefficients obtained from models fit to daytime SpO₂ are in close quantitative agreement with the corresponding values from published reference models for awake arterial oxygen saturation measured under controlled laboratory conditions. Regression models stratified by sex reveal significantly different age- and BMI-dependent SpO₂ trends for females compared with males, although constant terms and regression coefficients for altitude do not differ between sexes. Incorporating categorical variables encoding self-reported race/ethnicity into the full-cohort regression models identifies small but statistically significant differences in daytime SpO₂ (largest coefficient corresponding to 0.13% lower SpO₂, for Hispanic study participants compared to White participants), but no significant differences between groups for nocturnal SpO₂. Additional stratified analysis comparing regression models fit independently to subjects in each race/ethnicity group is suggestive of small differences in age- and sex-dependent trends, but indicates no significant difference in constant terms between any race/ethnicity groups for either daytime or nocturnal SpO₂. The large diverse study population and study design employing automated background SpO₂ measurements spanning the full 24-h circadian cycle enables the establishment of healthy population reference trends outside of clinical settings.

The effects of a structured physiotherapy program on pulmonary function and walking capacity in obese and non-obese adults undergoing cardiac surgery

BACKGROUND: Obesity is thought to be a risk factor for cardiopulmonary diseases due to changed pulmonary mechanics. It also drastically lowers functional capability in both males and females. A routine physiotherapy program has been shown to be effective in the prevention and treatment of cardiopulmonary diseases. It also significantly increases functional capacity following coronary artery bypass grafting. However, the effect of a structured physiotherapy program in obese and non-obese patients has not been well explored. As such, the objective of this study is to determine the effect of a standardized physiotherapy program on pulmonary function and walking capacity in obese and non-obese patients undergoing coronary artery bypass grafting. METHODS: A prospective study was conducted on 50 obese (age 57.2 ± 6.3 Y) and non-obese (age 56.6 ± 5.7 Y) adults who were schedule for coronary artery bypass grafting. Their body mass index was used to separate them into two groups. Both groups followed a structured physiotherapy program from day 1 to day 7 post cardiac surgery. Both groups underwent spirometry test at baseline (preoperatively) and after day 4 and day 7 postoperatively as well as a six-minute walk test at baseline and on day 7 postoperatively. RESULTS: At baseline, obese individuals had significantly lower pulmonary and physical functioning. On postoperative day 4, both groups deteriorated, although the obese group deterioration was worse, in most of the pulmonary parameters. On postoperative day 7, both groups improved, though the non-obese group improved at a faster rate. In contrary, it was observed that the obese group improved more rapidly in terms of functional capacity. CONCLUSIONS: The study indicated that the outcomes of a structured physiotherapy program following coronary artery bypass grafting were different for persons who were obese compared to those who were not. Adipose tissue variations surrounding the rib cage, diaphragm, and visceral cavity may account for the observed rate of change between the two groups. Therefore, it is apparent that a new strategy for managing obese individuals who have undergone CABG is required.

Changes in Thoracic Cavity Volume After Bilateral Lung Transplantation

Purpose

End-stage lung diseases result in anatomical changes of the thoracic cavity. However, very few studies have assessed changes in the thoracic cavity after lung transplantation (LTx). This study aimed to evaluate the relationships between thoracic cavity volume (TCV) changes after LTx and underlying lung disease.

Methods

We reviewed 89 patients who underwent a pre-LTx pulmonary function test (PFT), chest computed tomography (CT) scan, and 1-year follow-up CT after LTx. These patients were classified into two groups according to pre-LTx PFT as follows: obstructive group [forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) ratio < 70%] and restrictive group (FEV1/FVC ratio > 70%). We measured TCV using CT scan before and at 1 year after LTx and compared the TCV change in the two groups.

Results

In the restrictive group, TCV increased after LTx (preop: 2,347.8 ± 709.5 mL, 1-year postop: 3,224.4 ± 919.0 mL, p < 0.001). In contrast, in the obstructive group, it decreased after LTx (preop: 4,662.9 ± 1,296.3 mL, 1-year postop: 3,711.1 ± 891.7 mL, p < 0.001). We observed that restrictive lung disease, taller stature, lower body mass index, and larger donor lung were independently associated with increased TCV after LTx.

Conclusion

The disease-specific chest remodeling caused by restriction and hyperinflation is at least, in part, reversible. After LTx, the chest remodeling appears to occur in the opposite direction to the disease-specific remodeling caused by the underlying lung disease in recipients.

Obesity and asthma

Obesity has been well recognized as an important comorbidity in patients with asthma, representing a unique phenotype and endotype. This association indicates a close relationship between metabolic and inflammatory dysregulation. However, the detailed organ-organ, cellular, and molecular interactions are not completely resolved. Because of that, the relationship between obesity and asthma remains unclear. In this article, clinical and epidemiological studies, as well as data from experimental animal work, are being summarized to provide a state of the art update on this important topic. Much more work is needed, particularly mechanistic, to fully understand the interaction between obesity and asthma and to develop novel preventive and therapeutic strategies.

The effect of sex and body weight on lung volumes during sleep

Study Objectives

Low lung volumes are thought to contribute to obstructive sleep apnea (OSA). OSA is worse in the supine versus lateral body position, men versus women, obese versus normal-weight (NW) individuals and REM versus NREM sleep. All of these conditions may be associated with low lung volumes. The aim was to measure FRC during wake, NREM, and REM in NW and overweight (OW) men and women while in the supine and lateral body positions.

Methods

Eighty-one healthy adults were instrumented for polysomnography, but with nasal pressure replaced with a sealed, non-vented mask connected to an N2 washout system. During wakefulness and sleep, repeated measurements of FRC were made in both supine and right lateral positions.

Results

Two hundred eighty-five FRC measures were obtained during sleep in 29 NW (body mass index [BMI] = 22 ± 0.3 kg/m2) and 29 OW (BMI = 29 ± 0.7 kg/m2) individuals. During wakefulness, FRC differed between BMI groups and positions (supine: OW = 58 ± 3 and NW = 68 ± 3% predicted; lateral OW = 71 ± 3, NW = 81 ± 3% predicted). FRC fell from wake to NREM sleep in all participants and in both positions by a similar amount. As a result, during NREM sleep FRC was lower in OW than NW individuals (supine 46 ± 3 and 56 ± 3% predicted, respectively). FRC during REM was similar to NREM and no sex differences were observed in any position or sleep stage.

Conclusions

Reductions in FRC while supine and with increased body weight may contribute to worsened OSA in these conditions, but low lung volumes appear unlikely to explain the worsening of OSA in REM and in men versus women.

Gender- and Age-Specific Associations Between Body Fat Composition and C-Reactive Protein with Lung Function: A Cross-Sectional Study

Lung function deterioration is frequently observed in overweight and obese patients. In the current study, we explored the contribution of body fat (BF) composition, particularly visceral and nonvisceral adiposity, to lung function deterioration. In addition, we examined gender- and age-specific differences in the association between the joint effects of BF% and C-reactive protein (CRP) concentrations with lung function. This cross-sectional study involved 17,802 subjects undergoing health check-up. Clinical characteristics, body composition using bioelectrical impedance analysis (BIA), and lung function were evaluated and compared between genders. Subjects were stratified by gender-specific BF% cut-offs for evaluating the association of body composition and the risk of restrictive lung disease (RLD). Gender differences in the joint effects of BF% and CRP on lung function were observed. Visceral obesity increased the risk of RLD in women aged ≥45 years, but nonvisceral obesity reduced the risk of RLD in women aged <45 years. Our findings suggest that visceral fat per se can be used as an effective parameter to assess the association between lung function and obesity.

Classical regression equations of spirometric parameters are not applicable for diagnosing spirometric abnormalities in adipotic adults

The prevalence of overweighing and obese adults (defined as “adipotic” adults), has markedly increased over the world. A remarkable increase in the adipotic population urgently needs developing the regression equations for predicting spirometric parameters (SPs), which are specifically applicable to adipotic adults. Unfortunately, however, the reliable equations suitable for adipotic adults have not been reported to date. Recently, Yamaguchi et al have proposed the quantitative method to estimate the effects of adiposity on deciding the SPs incorporating with age-specific contributions of various explanatory, independent variables such as age (A), standing height (H), body weight (BW), and fat fraction of body mass (F). Extending the method proposed by Yamaguchi et al, we attempted to elaborate the novel regression equations applicable for diagnosing the spirometric abnormality in adipotic adults. For accomplishing this purpose, never-smoking, adipotic adults with body mass index (BMI) over 25 kg/m² and no respiratory illness were recruited from the general population in Japan (n = 3696, including men: 1890 and women: 1806). Introducing the four explanatory variables of A, H, BW, and F, gender-specific and age-dependent regression equations that allowed for prescribing the SPs in adipotic adults were constructed. Comparing the results obtained for non-adipotic adults (i.e., those with normal BMI), the negative or positive impact of height on SPs was preserved in adipotic adults, as well. However, the negative impact of age on SPs was blunted in adipotic men and the positive effect of BW on SPs was impeded in adipotic men and women. The fat fraction of body mass-elicited negative impact on SPs vanished in adipotic women. These results indicate that the regression equations of SPs for adipotic adults differ significantly from those for non-adipotic adults, leading to the conclusion that the regression equations for non-adipotic adults should not be used while judging the spirometric abnormalities in adipotic adults.

Respiratory Effects of Thoracic Load Carriage Exercise and Inspiratory Muscle Training as a Strategy to Optimize Respiratory Muscle Performance with Load Carriage

Many occupational and recreational settings require the use of protective and/or load-bearing apparatuses worn over the thoracic cavity, known as thoracic load carriage (LC). Compared to normal, unloaded exercise, thoracic LC exercise places an additional demand on the respiratory and limb locomotor systems by altering ventilatory mechanics as well as circulatory responses to exercise, thus accelerating the development of fatigue in the diaphragm and accessory respiratory muscles compared to unloaded exercise. This may be a consequence of the unique demands of thoracic LC, which places an additional mass load on the thoracic cavity and can restrict chest wall expansion. Therefore it is important to find effective strategies to ameliorate the detrimental effects of thoracic LC. Inspiratory muscle training is an intervention that aims to increase the strength and endurance of the diaphragm and accessory inspiratory muscle and may therefore be a useful strategy to optimize performance with thoracic LC.

Obesity modulates diaphragm curvature in subjects with and without COPD

Obesity is a common comorbidity of chronic obstructive pulmonary disease (COPD) and has been associated with worse outcomes. However, it is unknown whether the interaction between obesity and COPD modulates diaphragm shape and consequently its function. The body mass index (BMI) has been used as a correlate of obesity. We tested the hypothesis that the shape of the diaphragm muscle and size of the ring of its insertion in non-COPD and COPD subjects are modulated by BMI. We recruited 48 COPD patients with postbronchiodilator forced expiratory volume in 1 s (FEV1)-to-forced vital capacity (FVC) < 0.7 and 29 age-matched smoker/exsmoker control (non-COPD) subjects, who underwent chest computed tomography (CT) at lung volumes ranging from functional residual capacity (FRC) to total lung capacity (TLC). We then computed maximum principal diaphragm curvature in the midcostal region of the left hemidiaphragm at the end of inspiration during quiet breathing (EI) and at TLC. The radius of maximum curvature of diaphragm muscle increased with BMI in both COPD and non-COPD subjects. The size of diaphragm ring of insertion on the chest wall also increased significantly with increasing BMI. Surprisingly, COPD severity did not appear to cause significant alteration in diaphragm shape except in normal-weight subjects at TLC. Our data uncovered important factors such as BMI, the size of the diaphragm ring of insertion, and disease severity that modulate the structure of the ventilatory pump in non-COPD and COPD subjects.

The change of longitudinal relaxation rate in oxygen enhanced pulmonary MRI depends on age and BMI but not diffusing capacity of carbon monoxide in healthy never-smokers

OBJECTIVE

Oxygen enhanced pulmonary MRI is a promising modality for functional lung studies and has been applied to a wide range of pulmonary conditions. The purpose of this study was to characterize the oxygen enhancement effect in the lungs of healthy, never-smokers, in light of a previously established relationship between oxygen enhancement and diffusing capacity of carbon monoxide in the lung (DL,CO) in patients with lung disease.

METHODS

In 30 healthy never-smoking volunteers, an inversion recovery with gradient echo read-out (Snapshot-FLASH) was used to quantify the difference in longitudinal relaxation rate, while breathing air and 100% oxygen, ΔR1, at 1.5 Tesla. Measurements were performed under multiple tidal inspiration breath-holds.

RESULTS

In single parameter linear models, ΔR1 exhibit a significant correlation with age (p = 0.003) and BMI (p = 0.0004), but not DL,CO (p = 0.33). Stepwise linear regression of ΔR1 yields an optimized model including an age-BMI interaction term.

CONCLUSION

In this healthy, never-smoking cohort, age and BMI are both predictors of the change in MRI longitudinal relaxation rate when breathing oxygen. However, DL,CO does not show a significant correlation with the oxygen enhancement. This is possibly because oxygen transfer in the lung is not diffusion limited at rest in healthy individuals. This work stresses the importance of using a physiological model to understand results from oxygen enhanced MRI.

Worsening of pulmonary sarcoidosis

PURPOSE OF REVIEW

Despite the frequent occurrence of worsening pulmonary symptoms in pulmonary sarcoidosis patients, there is little available information concerning this topic.

RECENT FINDINGS

In this review, we outline the various causes for these symptoms. We propose to partition the various causes for these symptoms into specific categories.

SUMMARY

We believe that these categories will provide the clinician a framework to evaluate pulmonary sarcoidosis patients with such symptoms in a rigorous way that may be useful in optimizing their care.

Six-month intragastric balloon treatment for obesity improves lung function, body composition, and metabolic syndrome

BACKGROUND

The purpose of this study is to establish whether the use of an intragastric balloon (IGB) for 6 months improves lung function, metabolic parameters, and body fat distribution in patients with overweight/obesity and metabolic syndrome (MS).

METHODS

This is a longitudinal and interventional study on 40 adults, whose anthropometric, laboratory, and lung function parameters were assessed and who underwent dual-energy X-ray absorptiometry (DXA) before implantation and after removal of IGB.

RESULTS

The total lung capacity (TLC) (p = 0.0001), functional residual capacity (FRC) (p = 0.0001), residual volume (p = 0.0005), and expiratory reserve volume (ERV) (p = 0.0001) were significantly reduced by IGB. The body mass index (BMI) significantly decreased from a median of 39.1 kg/m(2) at the beginning of the study to 34.5 kg/m(2) at the end of the 6-month period (p = 0.0001). At the end of the study, 31 participants (77.5%) no longer met the diagnostic criteria of MS. The percentage of truncal, android, gynoid, and total fat investigated by DXA exhibited significant reductions (p = 0.0001). Significant correlations were found between delta TLC and delta waist circumference (ρ = -0.34; p = 0.03), delta FRC and delta IMC (ρ = -0.39; p = 0.01), delta ERV and delta BMI (ρ = -0.44; p = 0.005), and delta ERV and delta high-density lipoprotein (HDL) (ρ = -0.37; p = 0.02). Significant correlations were also found between delta ERV and delta truncal (ρ = -0.51; p = 0.004), android (ρ = -0.46; p = 0.01), gynoid (ρ = -0.55; p = 0.001), and total fat (ρ = -0.59; p = 0.0005).

CONCLUSIONS

IGB efficiently induced weight loss and promoted the improvement of lung function parameters, with a reduction of the restrictive ventilatory defect. It also promoted improvements of MS and the pattern of body fat distribution.

Pathogenesis of hyperinflation in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a preventable and treatable lung disease characterized by airflow limitation that is not fully reversible. In a significant proportion of patients with COPD, reduced lung elastic recoil combined with expiratory flow limitation leads to lung hyperinflation during the course of the disease. Development of hyperinflation during the course of COPD is insidious. Dynamic hyperinflation is highly prevalent in the advanced stages of COPD, and new evidence suggests that it also occurs in many patients with mild disease, independently of the presence of resting hyperinflation. Hyperinflation is clinically relevant for patients with COPD mainly because it contributes to dyspnea, exercise intolerance, skeletal muscle limitations, morbidity, and reduced physical activity levels associated with the disease. Various pharmacological and nonpharmacological interventions have been shown to reduce hyperinflation and delay the onset of ventilatory limitation in patients with COPD. The aim of this review is to address the more recent literature regarding the pathogenesis, assessment, and management of both static and dynamic lung hyperinflation in patients with COPD. We also address the influence of biological sex and obesity and new developments in our understanding of hyperinflation in patients with mild COPD and its evolution during progression of the disease.

Association of Body Mass Index (BMI) with Lung Function Parameters in Non-asthmatics Identified by Spirometric Protocols

INTRODUCTION

Association between obesity and asthma has been reported widely, with disparity between males and females. Epidemiological data which indicate that obesity precedes development of asthma and increases the prevalence and incidence of asthma, raises the possibility of a causal association.

AIM

To find out the association, including gender differences, between Body Mass Index (BMI) and lung functions in non-asthmatics identified by spirometric protocols.

METHODS

A retrospective analysis was conducted of the spirometry results obtained between October 2012 and March 2013 for six months. Participants were referred by a variety of medical specialties to the pulmonary function laboratory in Physiology department, R.G. Kar Medical College, Kolkata, India of the 590 test results recorded in the study database 424 non-asthmatic subjects were reviewed.

RESULTS

Significant differences in the spirometric parameters, measured as a percentage of predicted were evident between male and female. Among obese subjects significant correlation is found between BMI and pulmonary function values, FEV1(r = -0.531, p=0.009); FEF25-75% (r= -0.653, p=0.001); FEV1/FVC (r= - 0.603, p=0.002). Significant association was found between BMI and lung function in obese female but not in obese male.

CONCLUSION

Association was found between indices of spirometry and BMI in non-asthmatic obese group along with a gender disparity.

Anesthetic drugs and bariatric surgery

The prevalence of obesity is increasing worldwide. For severely obese patients, bariatric surgery is the only effective option for sustained weight loss and associated health improvement. As a consequence, the number of bariatric surgical procedures being performed is growing exponentially. Systematic knowledge regarding the effect of obesity on the pharmacokinetics and pharmacodynamics of anesthetic agents is generally lacking, and data for morbidly obese (body mass index [BMI] 40-49 kg/m2)) and super-obese patients (BMI > 50 kg/m2) are almost completely non-existent. Most drug-dosing guidelines are based on results from relatively small studies in moderately obese patients. Future systematic pharmacological research is needed for improved and more rational peri-operative care of morbidly obese patients.

A large cohort study concerning age-dependent impacts of anthropometric variables on spirometric parameters in nonsmoking healthy adults

BACKGROUNDS

Although height (H) has been considered the principal anthropometric variable governing lung function, the age-dependent differences in its influences on determining spirometric parameters (SPs) have not been conclusively investigated. Moreover, there has been no study centered on age-dependent effects of other anthropometric variables, including body weight (BW) and body fat mass (BFM) on SPs. In addition, the age-dependent influences of these anthropometric variables are anticipated to differ quantitatively between male and female participants.

METHODS

A total of 16,919 nonsmoking healthy Japanese adults (men: 6,116, women: 10,803) were partitioned into six groups stratified by gender and age at intervals of 20-years: young-, middle-, and advanced-age groups of either gender. Using a model in which a SP was described by a logarithmic additive function of age, H, BW, and BFM, we determined the partial regression coefficients of the respective anthropometric variables to predict the reference means of SPs, including FVC, FEV1, FEV1/FVC, PEF, FEF50, and FEF75, in the six groups.

RESULTS/DISCUSSION

Although the impact of H on FVC and FEV1 was relatively homogeneous irrespective of gender and age, its homogeneity faded for flow parameters, particularly in the female middle- and advanced-age groups, indicating that the age-dependent contribution of H to SPs was enhanced more in women. The impact of BW on SPs differed depending on age, and this effect was also more conspicuous for female participants. H and BW generally exerted positive effects on SPs, whereas BFM had negative effects. Opposite effects of BW and BFM were observed in the female middle-age group in particular.

CONCLUSIONS

The effects of anthropometric variables on spirometric parameters are highly age-dependent, particularly in women, leading to the conclusion that the assumption of age-independent, constant partial regression coefficients of anthropometric variables while predicting the reference mean of a certain spirometric parameter may result in substantial errors.

Environmental perturbations: Obesity

Obesity currently affects about one-third of the U.S. population, while another one-third is overweight. The importance of obesity for certain conditions such as heart disease and type 2 diabetes is well appreciated. The effects of obesity on the respiratory system have received less attention and are the subject of this article. Obesity alters the static mechanical properties of the respiratory system leading to a reduction in the functional residual capacity (FRC) and the expiratory reserve volume (ERV). There is substantial variability in the effects of obesity on FRC and ERV, at least some of which is related to the location rather than the total mass of adipose tissue. Obesity also results in airflow obstruction, which is only partially attributable to breathing at low lung volume, and can also promote airway hyperresponsiveness and asthma. Hypoxemia is common is obesity and correlates well with FRC, as well as with measures of abdominal obesity. However, obese subjects are usually eucapnic, indicating that hypoventilation is not a common cause of their hypoxemia. Instead, hypoxemia results from ventilation-perfusion mismatch caused by closure of dependent airways at FRC. Many obese subjects complain of dyspnea either at rest or during exertion, and the dyspnea score also correlates with reductions in FRC and ERV. Weight reduction should be encouraged in any symptomatic obese individual, since virtually all of the respiratory complications of obesity improve with even moderate weight loss.

Lung Function before and Two Days after Open-Heart Surgery

Reduced lung volumes and atelectasis are common after open-heart surgery, and pronounced restrictive lung volume impairment has been found. The aim of this study was to investigate factors influencing lung volumes on the second postoperative day. Open-heart surgery patients (n = 107, 68 yrs, 80% male) performed spirometry both before surgery and on the second postoperative day. The factors influencing postoperative lung volumes and decrease in lung volumes were investigated with univariate and multivariate analyses. Associations between pain (measured by numeric rating scale) and decrease in postoperative lung volumes were calculated with Spearman rank correlation test. Lung volumes decreased by 50% and were less than 40% of the predictive values postoperatively. Patients with BMI >25 had lower postoperative inspiratory capacity (IC) (33 ± 14% pred.) than normal-weight patients (39 ± 15% pred.), (P = 0.04). More pain during mobilisation was associated with higher decreases in postoperative lung volumes (VC: r = 0.33, P = 0.001; FEV₁: r = 0.35, P ≤ 0.0001; IC: r = 0.25, P = 0.01). Patients with high BMI are a risk group for decreased postoperative lung volumes and should therefore receive extra attention during postoperative care. As pain is related to a larger decrease in postoperative lung volumes, optimal pain relief for the patients should be identified.

Effect of carrying a weighted backpack on lung mechanics during treadmill walking in healthy men

Weighted backpacks are used extensively in recreational and occupational settings, yet their effects on lung mechanics during acute exercise is poorly understood. The purpose of this study was to determine the effects of different backpack weights on lung mechanics and breathing patterns during treadmill walking. Subjects (n = 7, age = 28 ± 6 years), completed two 2.5-min exercise stages for each backpack condition [no backpack (NP), an un-weighted backpack (NW) or a backpack weighing 15, 25 or 35 kg]. A maximal expiratory flow volume curve was generated for each backpack condition and an oesophageal balloon catheter was used to estimate pleural pressure. The 15, 25 and 35 kg backpacks caused a 3, 5 and 8% (P < 0.05) reduction in forced vital capacity compared with the NP condition, respectively. For the same exercise stage, the power of breathing (POB) requirement was higher in the 35 kg backpack compared to NP (32 ± 4.3 vs. 88 ± 9.0 J min(-1), P < 0.05; respectively). Independent of changes in minute ventilation, end-expiratory lung volume decreased as backpack weight increased. As backpack weight increased, there was a concomitant decline in calculated maximal ventilation, a rise in minute ventilation, and a resultant greater utilization of maximal available ventilation. In conclusion, wearing a weighted backpack during an acute bout of exercise altered operational lung volumes; however, adaptive changes in breathing mechanics may have minimized changes in the required POB such that at an iso-ventilation, wearing a backpack weighing up to 35 kg does not increase the POB requirement.

Preoperative physical activity levels and postoperative pulmonary complications post-esophagectomy

Postoperative pulmonary complications (PPCs) after esophagectomy have been reported to occur in 15-30% of patients and are the most common causes of major morbidity and mortality. Risk factors for the development of PPCs include impairment in lung function, cardiac reserve, aerobic capacity, and body composition. Physical activity is associated with these factors but has not been examined in relation to the risk of developing a PPC. The aim of this cross-sectional study was to investigate if there was a difference in physical activity levels, lung function, and body composition in patients who developed a PPC post-esphagectomy compared with those who did not. Consecutive patients were studied preoperatively: (i) lung function with a portable micro-medical spirometer; (ii) body composition analysis using a Tanita BC 418 machine (Tanita Corp., Tokyo, Japan); and (iii) physical activity with an accelerometer (RT3, (StayHealthy, Monrovia, CA, USA)). Thirty-seven patients were studied, mean age 61 ± 9 years. PPCs developed in 10 patients (27%). Smoking status, lung function, and body composition were similar in both groups. For physical activity, there were significant differences in the time spent sedentary (20.0 ± 1.5 h/day [PPC], 18.4 ± 2.1 h/day [non-PPC]; P < 0.05) and in moderate activity (20 ± 13.7 min/day [PPC], 36 ± 20.7 min/day [non PPC]; P < 0.01). Patients who developed a PPC engaged in less physical activity than those who did not; hence, targeting physical activity preoperatively may result in less PPCs.

Obesity and post-operative complications in patients undergoing non-bariatric surgery

As the prevalence of obesity continues to rise in society, an increasing number of patients undergoing non-bariatric surgery will be obese. Obesity is known to increase morbidity and mortality in the general population and thus is perceived as a risk factor for adverse post-surgical outcomes. This association is not clear-cut, however, and there is a lack of consensus in the literature on the risk between obesity and specific complications, in particular relating to infection, wound healing, respiratory and venous thromboembolism. The paucity of studies, as well as a lack of consistency of definition of obesity, with an over-reliance on body mass index rather than body composition analysis, may underlie this confusion. Emerging concepts position central/visceral adipose tissue as potentially key to the pathogenesis of the comorbidities associated with obesity, thus this article reviews emerging research investigating the association between visceral obesity, the metabolic syndrome and resulting post-operative complications. It is hypothesized that the state of chronic inflammation and dysmetabolism observed in visceral obese patients negatively influences post-operative outcomes and represents a potential target for pharmaconutrition. The need for further research investigating the influence of visceral adiposity on immune function post surgery and its impact on post-operative morbidity and mortality is highlighted.

Operative and early results of coronary artery bypass grafting in female patients in different body mass indexes

BACKGROUND

Female gender has been reported to be an independent risk factor for coronary artery bypass grafting (CABG) in European System for Cardiac Risk Evaluation. The effect of the body size on the CABG outcome is less clear. There is ongoing debate about obesity as a risk factor for adverse outcomes after cardiovascular procedures. The goal of this retrospective study is to evaluate the in hospital and early postoperative outcomes in severe obese, obese and normal-slightly obese female patients after CABG.

METHODS

In a four year period a total of 427 female patients underwent isolated CABG under cardiopulmonary bypass. The patients were allocated into three groups according to the Body Mass Index (BMI) as follows; group 1: severe obese patients; BMI > 35, group 2: obese patients; 30≤BMI≤35, group 3: normal-slightly obese patients; BMI < 30.

RESULTS

The patients in group 3 were older than the group1 and group 2 (65,6 ± 8,3 year vs 63,01 ± 8,0 and 63,57 ± 8,4 year p < 0,05). In group 1 diabetic patients were more than in group 2 and group 3 respectively (54,4% vs 43,4% and 40%, p < 0,05). Urgent operation was more in group 1 than in group 2 and 3 respectively (37,6% vs 17,2% and 21,2% p < 0,05). The patients in group 3 had significantly greater postoperative drainage at 24 h compared with values in group 1 and group 2 (647 ± 142 ml vs. 539 ± 169 ml and 582 ± 133 ml, p < 0,05). Mortality rate in group 1 was 0,8%, 0% in group 2 and 1,2% in group 3 respectively. Wound problem has occurred in 41 patients (9,6%).The percentage of postoperative wound problems was higher in group 1 but did not show statiscially difference. Following discharge a total of 43 (10,1%) patients re-hospitalized within 30 days. Re-hospitalization rate was 16,1% in group1, 9,8% in group 2 and 6,5% in group 3 (p < 0,05).

CONCLUSION

This study may give an aspect for evaluations of the inhospital-early mortality and morbidity after CABG in female patients in different BMI. Severe obesity is not a risk factor in-hospital mortality in female patients. However, severe obese female patients appear to have more wound problems and re-hospitalization rate after CABG compared to obese and normal-slightly obese patients.

Assessment of physical fitness for esophageal surgery, and targeting interventions to optimize outcomes

This review examines how higher levels of physiological reserve and fitness can help the patient endure the demands of esophageal surgery. Lung function, body composition, cardiac function, inflammatory mediators and exercise performance are all determinants of fitness. Physical fitness, both as an independent risk factor and through its effect on other risk factors, has been found to be significantly associated with the risk of developing postoperative pulmonary complications (PPCs) in patients following esophagectomy. Respiratory dysfunction preoperatively poses the dominant risk of developing complications, and PPCs are the most common causes of morbidity and mortality. The incidence of PPCs is between 15 and 40% with an associated 4.5-fold increase in operative mortality leading to approximately 45% of all deaths post-esophagectomy. Cardiac complications are the other principal postoperative complications, and pulmonary and cardiac complications are reported to account for up to 70% of postoperative deaths after esophagectomy. Risk reduction in patients planned for surgery is key in attaining optimal outcomes. The goal of this review was to discuss the risk factors associated with the development of postoperative pulmonary complications and how these may be modified prior to surgery with a specific focus on the pulmonary complications associated with esophageal resection. There are few studies that have examined the effect of modifying physical fitness pre-esophageal surgery. The data to date would indicate a need to develop targeted interventions preoperatively to increase physical function with the aim of decreasing postoperative complications.

Obesity induced bronchopulmonary hyperresponsiveness in Tunisian women

OBJECTIVE

The specific objective of this investigation was to determine whether bronchopulmonary responsiveness (BPR) to methacholine (MCH) was associated with the body mass index (BMI) of Tunisian women.

SUBJECTS

In all, 160 healthy nonsmoker women (52 lean, 45 overweight and 63 obese) were recruited and examined in the Clinical Laboratory of Physiology located in the Medical School of Sousse. The average ages (+/-s.e.) of the three categories of lean, overweight and obese subjects were 27.7+/-1.1, 33.2+/-1.7 and 37.5+/-1.3 years, respectively. Their corresponding mean BMIs (+/-s.e.) were 21.9+/-0.3, 27.7+/-0.2 and 36.5+/-0.8 kg m(-2), respectively.

MEASUREMENTS

Before their inclusion into the study, subjects were screened for their lung status by measuring their pulmonary function testing parameters using a whole body plethysmograph. BPR was assessed, using a cumulative concentration response curve technique, by measuring with a spirometer the decrease in forced expiratory volume in 1 s (FEV(1)) in response to a cumulative dose of MCH.

RESULTS

After adjusting for age, significant differences in both FEV(1) and forced vital capacity (VC) were found between the obese and lean groups (P<0.01), as well as between the obese and overweight groups (P<0.01). In addition, forced expiratory flow between 25 and 75% of VC was significantly different between the obese and lean groups (P<0.001), as well as between the lean and overweight groups (P=0.015). The mean maximum fall of FEV(1) in response to MCH challenge was significantly higher for the obese group (12.0%) than for the overweight (9.8%) or the lean (6.6%) group (P<0.01). Furthermore, the efficacy of the MCH agonist promoting the maximal response (E(max)) and its potency or effective dose producing 50% of the maximal response (ED(50)) were both associated with BMI (the higher the BMI, the higher the E(max) and the lower the ED(50)).

CONCLUSION

Our data clearly show that obesity affects pulmonary function performance in Tunisian women by potentially promoting their bronchial hyperreactivity as suggested by the significant correlation between their BMI and the efficacy of the MCH, as well as its potency.

Altered resting and exercise respiratory physiology in obesity

Obesity, particularly severe obesity, affects resting and exercise-related respiratory physiology. Severe obesity classically produces a restrictive ventilatory abnormality characterized by reduced expiratory reserve volume. Obstructive ventilatory abnormality may also be associated with abdominal obesity. Decreased peak work rates are usually seen among obese subjects in a setting of normal or decreased ventilatory reserve and normal cardiovascular response to exercise. Weight loss may reverse many adverse physiologic consequences of severe obesity on the respiratory system.

Obesity and aging

In this article, the combined effects of aging and obesity on the respiratory system are examined. Following a concise epidemiologic overview of the prevalence of obesity among older adults, the occurrence of prospective, often variable, health consequences related to this trend are considered as well as the observed effects of the association of both aging and obesity on respiratory anatomy, physiology, and diseases. Last, findings of research related to weight loss on respiratory function in obese older adults are summarized.

Combined effects of obesity and chronic obstructive pulmonary disease on dyspnea and exercise tolerance

RATIONALE

Severity of lung hyperinflation is known to influence the extent of dyspnea and exercise intolerance among patients with chronic obstructive pulmonary disease (COPD) with similar degrees of airway obstruction. Lung volume components are consistently affected by body mass index (BMI) in health and in disease.

OBJECTIVES

To explore the complex interactions between obesity, lung hyperinflation, dyspnea, and exercise performance in COPD.

METHODS

We compared dyspnea intensity ratings and ventilatory responses (breathing pattern, operating lung volumes, and gas exchange) during symptom-limited incremental cycle exercise in well-characterized groups of 18 obese (mean BMI +/- SD, 35 +/- 4 kg/m(2)) and 18 normal-weight (mean BMI +/- SD, 22 +/- 2 kg/m(2)) patients with moderate to severe COPD.

MEASUREMENTS AND MAIN RESULTS

Groups were well matched for FEV(1) (mean 49% predicted) and diffusing capacity (means >70% predicted), but resting lung hyperinflation (end-expiratory lung volume [EELV]) was significantly reduced in association with increasing BMI (P < 0.005). In the obese patients, peak symptom-limited oxygen uptake was increased (P < 0.01) and dyspnea ratings at a standardized ventilation were decreased (P < 0.01) compared with normal-weight patients. Ratings of dyspnea intensity at a standardized ventilation during exercise correlated well with the concurrent dynamic EELV/total lung capacity (TLC) ratio (r = 0.68; P < 0.00001) and with the resting EELV/TLC (r = 0.67; P < 0.00001).

CONCLUSIONS

The combined mechanical effects of obesity and COPD reduced operating lung volumes at rest and throughout exercise with favorable influences on dyspnea perception and peak oxygen uptake during cycle ergometry.

Physiology of obesity and effects on lung function

In obese people, the presence of adipose tissue around the rib cage and abdomen and in the visceral cavity loads the chest wall and reduces functional residual capacity (FRC). The reduction in FRC and in expiratory reserve volume is detectable, even at a modest increase in weight. However, obesity has little direct effect on airway caliber. Spirometric variables decrease in proportion to lung volumes, but are rarely below the normal range, even in the extremely obese, while reductions in expiratory flows and increases in airway resistance are largely normalized by adjusting for lung volumes. Nevertheless, the reduction in FRC has consequences for other aspects of lung function. A low FRC increases the risk of both expiratory flow limitation and airway closure. Marked reductions in expiratory reserve volume may lead to abnormalities in ventilation distribution, with closure of airways in the dependent zones of the lung and ventilation perfusion inequalities. Greater airway closure during tidal breathing is associated with lower arterial oxygen saturation in some subjects, even though lung CO-diffusing capacity is normal or increased in the obese. Bronchoconstriction has the potential to enhance the effects of obesity on airway closure and thus on ventilation distribution. Thus obesity has effects on lung function that can reduce respiratory well-being, even in the absence of specific respiratory disease, and may also exaggerate the effects of existing airway disease.

Exercise-induced bronchospasm in obese adolescents

BACKGROUND

Assess the frequency and severity of exercise-induced bronchospasm (EIB) in obese adolescents.

METHODS

A cross-sectional descriptive study involving 80 adolescents of both genders, aged 10-16 years-old, divided into four groups according to clinical history of asthma and/or allergic rhinitis and body mass index as follows: asthmatic obese (n = 18); asthmatic non-obese (n = 21); obese non-asthmatic (n = 26); and healthy individuals (n = 15). An exercise bronchoprovocation test was used for EIB diagnosis, considered positive when the forced expiratory volume in one second (FEV(1)) decreased > or = 15% in relation to pre-exercise FEV(1). Maximum percent fall in FEV(1) (MF%FEV(1)) and area above the curve (AAC(0-30)) were calculated to evaluate EIB severity and recovery.

RESULTS

No significant difference was found in EIB frequency between asthmatic obese (50.0%) and asthmatic non-obese (38.0%) individuals or between obese non-asthmatics (11.5%) and healthy individuals (6.7%). However, the MF%FEV(1) and AAC(0-30) were significantly greater in the asthmatic obese group compared to the asthmatic non-obese (37.7% and 455 vs 24.5% and 214, p<0.03).

CONCLUSIONS

Obesity did not contribute to increased EIB frequency in asthmatics and non-asthmatics. However, obesity did contribute to increased EIB severity and recovery among asthmatics.

Cigarette smoking is associated with subclinical parenchymal lung disease: the Multi-Ethnic Study of Atherosclerosis (MESA)-lung study

RATIONALE

Cigarette smoking is a risk factor for diffuse parenchymal lung disease. Risk factors for subclinical parenchymal lung disease have not been described.

OBJECTIVES

To determine if cigarette smoking is associated with subclinical parenchymal lung disease, as measured by spirometric restriction and regions of high attenuation on computed tomography (CT) imaging.

METHODS

We examined 2,563 adults without airflow obstruction or clinical cardiovascular disease in the Multi-Ethnic Study of Atherosclerosis, a population-based cohort sampled from six communities in the United States. Cumulative and current cigarette smoking were assessed by pack-years and urine cotinine, respectively. Spirometric restriction was defined as a forced vital capacity less than the lower limit of normal. High attenuation areas on the lung fields of cardiac CT scans were defined as regions having an attenuation between -600 and -250 Hounsfield units, reflecting ground-glass and reticular abnormalities. Generalized additive models were used to adjust for age, gender, race/ethnicity, smoking status, anthropometrics, center, and CT scan parameters.

MEASUREMENTS AND MAIN RESULTS

The prevalence of spirometric restriction was 10.0% (95% confidence interval [CI], 8.9-11.2%) and increased relatively by 8% (95% CI, 3-12%) for each 10 cigarette pack-years in multivariate analysis. The median volume of high attenuation areas was 119 cm(3) (interquartile range, 100-143 cm(3)). The volume of high attenuation areas increased by 1.6 cm(3) (95% CI, 0.9-2.4 cm(3)) for each 10 cigarette pack-years in multivariate analysis.

CONCLUSIONS

Smoking may cause subclinical parenchymal lung disease detectable by spirometry and CT imaging, even among a generally healthy cohort.

Observations on the physiological interactions between obesity and asthma

To explore whether asthma and obesity share overlapping pathogenic features, we examined the impact of each alone, and in combination, on multiple aspects of lung function. We reasoned that if they influenced the lungs through similar mechanisms, the individual physiological manifestations in the comorbid state should interact in a complex fashion. If not, then the abnormalities should simply add. We measured specific conductance, spirometry, lung volumes, and airway responsiveness to adrenergic and cholinergic agonists in 52 normal, 53 asthmatic, 52 obese, and 53 asthmatic and obese patients using standard techniques. Six-minute walks were performed in subsets from each group. Asthma significantly lowered specific conductance and the spirometric variables while increasing airway reactivity and residual volume. Obesity also reduced the spirometric variables as well as total lung capacity and functional residual capacity. Residual volume, specific conductance, and airway responsivity were unaltered. With comorbidity, the disease-specific derangements added algebraically. Features that existed in isolation appeared unchanged in the combination, whereas shared ones either added or subtracted depending on the individual directional changes. Synergistic interactions were not observed. Body mass index weakly correlated with spirometry and lung volumes in asthma, but not with specific conductance or bronchial reactivity. Exercise performance did not aid in differentiation. Our findings indicate asthma and obesity appear to influence the respiratory system through different processes.

Association of expiratory airway dysfunction with marked obesity in healthy adult dogs

OBJECTIVE

To evaluate the effects of obesity on pulmonary function in healthy adult dogs.

ANIMALS

36 Retrievers without cardiopulmonary disease.

PROCEDURES

Dogs were assigned to 1 of 3 groups on the basis of body condition score (1 through 9): nonobese (score, 4.5 to 5.5), moderately obese (score, 6.0 to 6.5), and markedly obese (score, 7.0 to 9.0). Pulmonary function tests performed in conscious dogs included spirometry and measurement of inspiratory and expiratory airway resistance (R(aw)) and specific R(aw) (sR(aw)) during normal breathing and during hyperpnea via head-out whole-body plethysmography. Functional residual capacity (FRC; measured by use of helium dilution), diffusion capacity of lungs for carbon monoxide (DLCO), and arterial blood gas variables (PaO(2), PaCO(2), and alveolar-arterial gradient) were assessed.

RESULTS

During normal breathing, body condition score did not influence airway function, DLCO, or arterial blood gas variables. During hyperpnea, expiratory sR(aw) was significantly greater in markedly obese dogs than nonobese dogs and R(aw) was significantly greater in markedly obese dogs, compared with nonobese and moderately obese dogs. Although not significantly different, markedly obese dogs had a somewhat lower FRC, compared with other dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

In dogs, obesity appeared to cause airflow limitation during the expiratory phase of breathing, but this was only evident during hyperpnea. This suggests that flow limitation is dynamic and likely occurs in the distal (rather than proximal) portions of the airways. Further studies are warranted to localize the flow-limited segment and understand whether obesity is linked to exercise intolerance via airway dysfunction in dogs.

Comparison of pre- and postoperative pulmonary function in obese and non-obese female patients undergoing coronary artery bypass graft surgery

OBJECTIVE AND BACKGROUND

Various studies have suggested that body size and in-hospital mortality are related. However, only a few analysed the effects of obesity on pulmonary complications following coronary artery bypass graft surgery (CABG). The purpose of the present study was to assess early changes in lung volumes, respiratory complications and arterial blood gas tension following CABG in obese women.

METHODS

Pulmonary function tests (PFTs), treadmill exercise capacity tests (TM), arterial blood gases and pulmonary complications were studied in 124 obese (mean age 57.2+/-5.8 years) and 108 non-obese (mean age 58.6+/-5.9 years) female patients undergoing elective CABG. PFT, TM tests, arterial blood gas analyses and CXR were performed in the preoperative and postoperative periods and pulmonary complications were recorded. Breathing and coughing exercises, early ambulation and pulmonary clearing techniques were used by physical therapists to prevent pulmonary complications after CABG surgery.

RESULTS

Postoperative PFT and TM tests deteriorated significantly in both groups (P<0.0001). The deterioration in the obese group was highly significant. The postoperative deterioration of blood gas measurements in obese patients was also statistically significant compared to non-obese patients. Early pulmonary complications developed in 21 (16.94%) of the obese patients and in 10 (9.25%) of non-obese patients. Duration of mechanical ventilation, intensive care unit and hospital stays were longer compared to the non-obese patients (P=0.008, P<0.0001, P=0.0386, respectively).

CONCLUSION

Obesity has a detrimental effect on pulmonary function, exercise capacity, blood gas measurements and complications rates in postoperative period following CABG surgery.

Altered respiratory physiology in obesity

The major respiratory complications of obesity include a heightened demand for ventilation, elevated work of breathing, respiratory muscle inefficiency and diminished respiratory compliance. The decreased functional residual capacity and expiratory reserve volume, with a high closing volume to functional residual capacity ratio of obesity, are associated with the closure of peripheral lung units, ventilation to perfusion ratio abnormalities and hypoxemia, especially in the supine position. Conventional respiratory function tests are only mildly affected by obesity except in extreme cases. The major circulatory complications are increased total and pulmonary blood volume, high cardiac output and elevated left ventricular end-diastolic pressure. Patients with obesity commonly develop hypoventilation and sleep apnea syndromes with attenuated hypoxic and hypercapnic ventilatory responsiveness. The final result is hypoxemia, pulmonary hypertension and progressively worsening disability. Obese patients have increased dyspnea and decreased exercise capacity, which are vital to quality of life. Decreased muscle, increased joint pain and skin friction are important determinants of decreased exercise capacity, in addition to the cardiopulmonary effects of obesity. The effects of obesity on mortality in heart failure and chronic obstructive pulmonary disease have not been definitively resolved. Whether obesity contributes to asthma and airway hyper-responsiveness is uncertain. Weight reduction and physical activity are effective means of reversing the respiratory complications of obesity.