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Journal ArticleDOI

Physiology of obesity and effects on lung function.

01 Jan 2010-Journal of Applied Physiology (American Physiological Society)-Vol. 108, Iss: 1, pp 206-211
TL;DR: 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.
Abstract: 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.
Citations
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Journal ArticleDOI
TL;DR: The considerable growth in the science and application of pulmonary rehabilitation since 2006 adds further support for its efficacy in a wide range of individuals with chronic respiratory disease.
Abstract: Background: Pulmonary rehabilitation is recognized as a core component of the management of individuals with chronic respiratory disease. Since the 2006 American Thoracic Society (ATS)/European Respiratory Society (ERS) Statement on Pulmonary Rehabilitation, there has been considerable growth in our knowledge of its efficacy and scope. Purpose: The purpose of this Statement is to update the 2006 document, including a new definition of pulmonary rehabilitation and highlighting key concepts and major advances in the field. Methods: A multidisciplinary committee of experts representing the ATS Pulmonary Rehabilitation Assembly and the ERS Scientific Group 01.02, “Rehabilitation and Chronic Care,” determined the overall scope of this update through group consensus. Focused literature reviews in key topic areas were conducted by committee members with relevant clinical and scientific expertise. The final content of this Statement was agreed on by all members. Results: An updated definition of pulmonary rehabilitation is proposed. New data are presented on the science and application of pulmonary rehabilitation, including its effectiveness in acutely ill individuals with chronic obstructive pulmonary disease, and in individuals with other chronic respiratory diseases. The important role of pulmonary rehabilitation in chronic disease management is highlighted. In addition, the role of health behavior change in optimizing and maintaining benefits is discussed. Conclusions: The considerable growth in the science and application of pulmonary rehabilitation since 2006 adds further support for its efficacy in a wide range of individuals with chronic respiratory disease Read More: http://www.atsjournals.org/doi/abs/10.1164/rccm.201309-1634ST

2,734 citations

Journal ArticleDOI
TL;DR: Although they do not meet the current criteria for COPD, symptomatic current or former smokers with preserved pulmonary function have exacerbations, activity limitation, and evidence of airway disease.
Abstract: BackgroundCurrently, the diagnosis of chronic obstructive pulmonary disease (COPD) requires a ratio of forced expiratory volume in 1 second (FEV1) to forced vital capacity (FVC) of less than 0.70 as assessed by spirometry after bronchodilator use. However, many smokers who do not meet this definition have respiratory symptoms. MethodsWe conducted an observational study involving 2736 current or former smokers and controls who had never smoked and measured their respiratory symptoms using the COPD Assessment Test (CAT; scores range from 0 to 40, with higher scores indicating greater severity of symptoms). We examined whether current or former smokers who had preserved pulmonary function as assessed by spirometry (FEV1:FVC ≥0.70 and an FVC above the lower limit of the normal range after bronchodilator use) and had symptoms (CAT score, ≥10) had a higher risk of respiratory exacerbations than current or former smokers with preserved pulmonary function who were asymptomatic (CAT score, <10) and whether those w...

489 citations


Additional excerpts

  • ...Nonwhite 62 (31) 93 (22) 177 (42) 45 (13) 113 (18)...

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  • ...(%) 35/195 (18) 112/421 (27) 142/422 (34) 89/335 (27) 221/622 (36)...

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Journal ArticleDOI
TL;DR: It is shown that sneezing is rare and not important for—and that coughing is not required for—influenza virus aerosolization, and that upper and lower airway infection are independent and that fine-particle exhaled aerosols reflect infection in the lung.
Abstract: Little is known about the amount and infectiousness of influenza virus shed into exhaled breath. This contributes to uncertainty about the importance of airborne influenza transmission. We screened 355 symptomatic volunteers with acute respiratory illness and report 142 cases with confirmed influenza infection who provided 218 paired nasopharyngeal (NP) and 30-minute breath samples (coarse >5-µm and fine ≤5-µm fractions) on days 1–3 after symptom onset. We assessed viral RNA copy number for all samples and cultured NP swabs and fine aerosols. We recovered infectious virus from 52 (39%) of the fine aerosols and 150 (89%) of the NP swabs with valid cultures. The geometric mean RNA copy numbers were 3.8 × 104/30-minutes fine-, 1.2 × 104/30-minutes coarse-aerosol sample, and 8.2 × 108 per NP swab. Fine- and coarse-aerosol viral RNA were positively associated with body mass index and number of coughs and negatively associated with increasing days since symptom onset in adjusted models. Fine-aerosol viral RNA was also positively associated with having influenza vaccination for both the current and prior season. NP swab viral RNA was positively associated with upper respiratory symptoms and negatively associated with age but was not significantly associated with fine- or coarse-aerosol viral RNA or their predictors. Sneezing was rare, and sneezing and coughing were not necessary for infectious aerosol generation. Our observations suggest that influenza infection in the upper and lower airways are compartmentalized and independent.

432 citations


Cites background from "Physiology of obesity and effects o..."

  • ...Alternatively, increasing BMI is associated with increased frequency of small airways closure, and the resulting increased aerosol generation during airway reopening as described above may explain the stronger association of BMI with fine than coarse aerosols and lack of association with NP swabs (31)....

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Journal ArticleDOI
TL;DR: Obesity has long been recognized as having significant effects on respiratory function, and some clear patterns have emerged, but the distribution of fat, that is, upper versus lower body, may be more important than body mass index.
Abstract: Obesity has long been recognized as having significant effects on respiratory function The topic has been studied for at least the last half century, and some clear patterns have emerged Obese patients tend to have higher respiratory rates and lower tidal volumes Total respiratory system compliance is reduced for a variety of reasons, which will be discussed Lung volumes tend to be decreased, especially expiratory reserve volume Spirometry, gas exchange and airway resistance all tend to be relatively well preserved when adjusted for lung volumes Patients may be mildly hypoxaemic, possibly due to ventilation-perfusion mismatching at the base of the lungs, where microatelectasis is likely to occur Weight loss leads to a reversal of these changes For all of these changes, the distribution of fat, that is, upper versus lower body, may be more important than body mass index

274 citations

Journal ArticleDOI
TL;DR: Understanding of the underlying mechanism of adult-onset asthma and identification of specific phenotypes may further the understanding of pathophysiology and treatment response, leading to better targeting of both existing and new approaches for personalised management.
Abstract: Asthma that starts in adulthood differs from childhood-onset asthma in that it is often non-atopic, more severe and associated with a faster decline in lung function. Understanding of the underlying mechanism of adult-onset asthma and identification of specific phenotypes may further our understanding of pathophysiology and treatment response, leading to better targeting of both existing and new approaches for personalised management. Pivotal studies in past years have led to sustained progress in many areas, ranging from risk factors for development, identification of different phenotypes, and introduction of new therapies. This review highlights and discusses literature on adult-onset asthma, with special focus on the differences from childhood-onset asthma, risk factors for development, phenotypes of adult-onset asthma and new approaches for personalised management.

238 citations

References
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Journal ArticleDOI
01 Sep 2006-Chest
TL;DR: It was showed that BMI has significant effects on all of the lung volumes, and the greatest effects were on FRC and ERV, which occurred at BMI values < 30 kg/m2, which will assist clinicians when interpreting PFT results in patients with normal airway function.

874 citations

Journal ArticleDOI
TL;DR: It is concluded that obesity does not usually preclude use of usual predictors, and an abnormal pulmonary function test value should be considered as caused by intrinsic lung disease and not by obesity, except in those with extreme obesity.
Abstract: Obesity, because it alters the relationship between the lungs, chest wall, and diaphragm, has been expected to alter respiratory function. We studied 43 massively obese but otherwise normal, nonsmoking, young adults with spirometry, lung volume measurement by nitrogen washout, and single-breath diffusing capacity for carbon monoxide (DLCO). Changes in respiratory function were of two types, those that changed in proportion to degree of obesity--expiratory reserve volume (ERV) and DLCO--and those that changed only with extreme obesity--vital capacity, total lung capacity, and maximal voluntary ventilation. When compared with commonly used predicting equations, we found that mean values of subjects grouped by degree of obesity were very close to predicted values, except in those with extreme obesity in whom weight (kg)/height (cm) exceeded 1.0. In 29 subjects who lost a mean of 56 kg, significant increases in vital capacity, ERV, and maximal voluntary ventilation were found, along with a significant decrease in DLCO. Because most subjects fell within the generally accepted 95% confidence limits for the predicted values, we concluded that obesity does not usually preclude use of usual predictors. An abnormal pulmonary function test value should be considered as caused by intrinsic lung disease and not by obesity, except in those with extreme obesity.

554 citations


"Physiology of obesity and effects o..." refers background in this paper

  • ...increased in extremely obese subjects (42, 44), probably as a...

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  • ...The RV is usually well preserved (5, 11, 48, 63, 67), and the RV-to-TLC ratio remains normal or slightly increased (5, 28)....

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  • ...result of the increase in blood volume (42)....

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  • ...that lung CO-diffusing capacity is normal (15, 42, 53, 57), even...

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  • ...A reduction in the downward movement of the diaphragm, due to increased abdominal mass, is likely to decrease TLC by limiting the room for lung expansion on inflation....

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Journal ArticleDOI
TL;DR: The compliance of the total respiratory system and its components was studied in normal and obese spontaneously breathing unanesthetized subjects and found that the former are more compliant than the latter.
Abstract: The compliance of the total respiratory system and its components was studied in 24 normal and 12 obese spontaneously breathing unanesthetized subjects. The mean compliance of the total respiratory...

511 citations


"Physiology of obesity and effects o..." refers background in this paper

  • ...Obesity is characterized by a stiffening of the total respiratory system (35), which is presumed to be due to a combination of effects on lung and chest wall compliance (41)....

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  • ...Studies of conscious, spontaneously breathing subjects have suggested that there is a reduction in chest wall compliance in obesity (35)....

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Journal ArticleDOI
TL;DR: The effects of body mass index (BMI) on functional residual capacity (FRC), respiratory mechanics, respiratory mechanics (compliance and resistance), gas exchange, and the inspiratory mechanical work done per liter of ventilation during general anesthesia are investigated.
Abstract: We investigated the effects of body mass index (BMI) on functional residual capacity (FRC), respiratory mechanics (compliance and resistance), gas exchange, and the inspiratory mechanical work done per liter of ventilation during general anesthesia.We used the esophageal balloon technique, together

508 citations

Journal ArticleDOI
01 May 1993-Chest
TL;DR: It is suggested that in addition to the elastic load, obese subjects have to overcome increased respiratory resistance resulting from the reduction in lung volumes related to being overweight.

437 citations


"Physiology of obesity and effects o..." refers background in this paper

  • ...However, specific airway resistance, calculated by adjusting for the lung volume at which the measurements were made, is in the normal range (36, 44, 65, 67), so that the apparent reduction in airway caliber in the obese is attributable to the reduction in lung volumes rather than to airway obstruction....

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  • ...Most studies have demonstrated a reduction in lung compliance in obese individuals (21, 40, 41, 53) that appears to be exponentially related to BMI (40)....

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  • ...Similarly, expiratory flows decrease with increasing weight (5, 44), in proportion to the lung volumes (67)....

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  • ...The RV is usually well preserved (5, 11, 48, 63, 67), and the RV-to-TLC ratio remains normal or slightly increased (5, 28)....

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  • ...Lung volumes were only loosely associated with BMI, but both DXA and non-DXA-derived variables reflecting upper body fat had highly significant negative correlations with FRC and ERV in both men and women....

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