Physiology of obesity and effects on lung function

The impact of abdominal adiposity measured by sonography on the pulmonary function of pre-menopausal females

Background

The Body Mass Index (BMI) is a widely used parameter to study obesity; however it does not assess the distribution of body adiposity. Ultrasonography is a reliable method of measuring subcutaneous (SAT), visceral (VAT) and Total adipose tissue of the abdomen (TAT) to determine the influence of abdominal fat on pulmonary function by directly measuring abdominal adipose tissue.

Methods

Eighty pre-menopausal, non-smoker, sedentary females with no history of pulmonary disease were subdivided into three groups: 25 normal-weight, 28 overweight, 27 obese. Absolute and predictive spirometric values were obtained: FVC, FEV₁, FEV₁/FVC, IC, ERV.

Results

A positive correlation between increased %IC and decreased %ERV was observed with increased BMI (p < 0.02; 0.001 respectively); %FVC, %FEV₁ and %ERV decreased significantly as SAT (p = 0.01, p = 0.02; p < 0.001) and TAT (p = 0.01, p = 0.03, p < 0.001) increased, whereas VAT was negatively correlated only with %ERV (p < 0.001). Increments of 5 mm in TAT, VAT and SAT were followed by a reduction of 0.83 %, 0.81 %, 1.90 % in %FVC, respectively, as well as a reduction of 4.25 %, 4.31 % and 9.44 % in %ERV, respectively.

Conclusions

Subcutaneous abdominal adipose tissue deposition in obese females has a greater negative influence on pulmonary function than visceral adipose tissue deposition.

Pulmonary function of adolescents from Tripura, a North-eastern state of India

Objective:

Spirometric evaluation of pulmonary function has been evolved as clinical tool in diagnosis, management, and follow-up of respiratory disorders. There are very few studies on normative reference values of pulmonary function parameters for adolescents from Tripura, a North-eastern state of India. The present study was aimed to evaluate pulmonary function and their predictors in male and female adolescents of Tripura.

Materials and Methods:

A total of 640 (320 from tribal and 320 non-tribal) healthy, non-smoking male and female school children (age 10-14 years) from four different districts of Tripura were randomly sampled for the study. The pulmonary function parameters analysed included forced vital capacity (FVC), forced expiratory volume in 1 second (FEV₁), peak expiratory flow rate (PEFR), forced expiratory flow between 25% and 75% expired volume (FEF_25-75%), ratio of FEV₁/FVC and maximum voluntary ventilation (MVV).

Results:

The results revealed that body weight, body mass index (BMI), PEFR, FEF_25-75% and MVV are significantly high among male tribal children in comparison to non-tribal children. Height, weight, waist-to-hip ratio (WHR), waist-to-height ratio (WHtR), PEFR and MVV were found to be significantly more in tribal girls. In case of adolescents from Tripura, most of the pulmonary function parameters correlated with anthropometric parameters of the subject like height, weight, BMI, WHR, and WHtR.

Conclusion:

From the present study, it can be concluded that both anthropometric and pulmonary function status of tribal and non-tribal adolescents from Tripura are comparable. The computed regression norms may be used to predict pulmonary function of adolescents from Tripura by using anthropometric indices.

Physiological and management implications of obesity in critical illness

Obesity is highly prevalent in the United States and is becoming increasingly common worldwide. The anatomic and physiological changes that occur in obese individuals may have an impact across the spectrum of critical illness. Obese patients may be more susceptible to hypoxemia and hypercapnia. During mechanical ventilation, elevated end-expiratory pressures may be required to improve lung compliance and to prevent ventilation-perfusion mismatch due to distal airway collapse. Several studies have shown an increased risk of organ dysfunction such as the acute respiratory distress syndrome and acute kidney injury in obese patients. Predisposition to ventricular hypertrophy and increases in blood volume should be considered in fluid management decisions. Obese patients have accelerated muscle losses in critical illness, making nutrition essential, although the optimal predictive equation to estimate nutritional needs or formulation for obese patients is not well established. Many common intensive care unit medications are not well studied in obese patients, necessitating understanding of pharmacokinetic concepts and consultation with pharmacists. Obesity is associated with higher risk of deep venous thrombosis and catheter-associated bloodstream infections, likely related to greater average catheter dwell times. Logistical issues such as blood pressure cuff sizing, ultrasound assistance for procedures, diminished quality of some imaging modalities, and capabilities of hospital equipment such as beds and lifts are important considerations. Despite the physiological alterations and logistical challenges involved, it is not clear whether obesity has an effect on mortality or long-term outcomes from critical illness. Effects may vary by type of critical illness, obesity severity, and obesity-associated comorbidities.

Chest wall strapping. An old physiology experiment with new relevance to small airways diseases

Chest wall strapping (CWS) induces breathing at low lung volumes. Mild to moderate obesity can lead to similar changes in lung volumes, due to chest wall and abdominal restriction. Chest wall strapping is also conceptually similar to a mismatch between significantly oversized donor lungs transplanted into a recipient with a smaller chest cavity. Chest wall strapping increases lung elastic recoil, reduces pulmonary compliance, and substantially increases maximal expiratory flows. The interactions between elastic properties of the lung parenchyma and small airways are critical for pulmonary function. Chest wall strapping lowers residual volume and closing volume, likely from the interdependence between increased elastic recoil and airways, leading to greater radial distending forces on small airways and small airway dilation. Chronic obstructive pulmonary disease (COPD) and chronic rejection of the transplanted lung, bronchiolitis obliterans syndrome (BOS), are primarily diseases of the small airways, and are characterized by progressive obstruction and subsequent loss of small airways. In COPD, higher body mass index (BMI) (conceptually like being more tightly strapped) is associated with lower lung volumes, increased airway conductance, and lower risk of progression to emphysema or death. Likewise, in lung transplantation, oversized donor lungs have been linked to higher expiratory airflows, lower risk of bronchiolitis obliterans syndrome, and improved survival. This article reviews the physiology of chest wall strapping and explores how it could enhance the understanding or even the treatment of small airway diseases, such as COPD and bronchiolitis obliterans syndrome.

Ventilation/Perfusion distribution abnormalities in morbidly obese subjects before and after bariatric surgery

BACKGROUND

Obesity is a global and growing public health problem. Bariatric surgery (BS) is indicated in patients with morbid obesity. To our knowledge, the effects of morbid obesity and BS on ventilation/perfusion (V.a/Q.) ratio distributions using the multiple inert gas elimination technique have never before been explored.

METHODS

We compared respiratory and inert gas (V.a/Q. ratio distributions) pulmonary gas exchange, breathing both ambient air and 100% oxygen, in 19 morbidly obese women (BMI, 45 kg/m2), both before and 1 year after BS, and in eight normal-weight, never smoker, age-matched, healthy women.

RESULTS

Before BS, morbidly obese individuals had reduced arterial Po2 (76 ± 2 mm Hg) and an increased alveolar-arterial Po2 difference (27 ± 2 mm Hg) caused by small amounts of shunt (4.3% ± 1.1% of cardiac output), along with abnormally broadly unimodal blood flow dispersion (0.83 ± 0.06). During 100% oxygen breathing, shunt increased twofold in parallel with a reduction of blood flow to low V.a/Q. units, suggesting the development of reabsorption atelectasis without reversion of hypoxic pulmonary vasoconstriction. After BS, body weight was reduced significantly (BMI, 31 kg/m2), and pulmonary gas exchange abnormalities were decreased.

CONCLUSIONS

Morbid obesity is associated with mild to moderate shunt and V.a/Q. imbalance. These abnormalities are reduced after BS.

Asthma and obesity: mechanisms and clinical implications

Obesity is the most common asthma co-morbidity; it has been associated with increased risk for asthma exacerbations, worse respiratory symptoms and poor control. The exact mechanisms remain elusive and are probably multifactorial, stemming from mechanical alterations of the airways and lung parenchyma, to systemic and airway inflammatory and metabolic dysregulation that adversely influences lung function and or response to therapy. However, the fact that not every obese asthmatic is equally affected by weight gain highlights the many challenges and complexities in understanding this association. The factors that determine susceptibility may not depend on being obese alone, but rather the interactions with other phenotypical characteristics, such as age of asthma onset, gender and race to name a few. Inability to account for asthma phenotypes that are differentially affected by increasing body mass index (BMI) may contribute to the lack of consistent results across studies. This review will provide a succinct summary of obesity-related mechanisms and the clinical impact on asthma including highlights on recent progress.

Alterations in Lung Functions Based on BMI and Body Fat % Among Obese Indian Population at National Capital Region

BACKGROUND

In India, non-asthmatic hospital admission case study has been conducted to find out the relationship between obesity and lung functions. The main objective of the present study was to find out the alterations in lung functions due to obesity among Indian population living at National Capital Region (NCR).

MATERIALS AND METHODS

We examined 609 non obese and 211 obese subjects in a cross sectional study from National Capital Region, India with age group ranges between 18-70 years. BMI and body fat % was determined using body fat analyzer. Obese and non-obese subjects were classified based on criteria for BMI and Body fat %. Lung function test viz., FEV1 and PEFR were conducted using portable spirometer (PIKO-1).

RESULTS

A significant correlation (p<0.05) was observed between BMI and PEFR among non-obese male and female subjects. Decline in PEFR and FEV1 values for corresponding increase in body fat % was observed among study subjects. A significant (p<0.01) decline in mean FEV1 and PEFR was observed among non-obese and obese subjects, compared to their Indian reference standards for lung functions. A significant negative correlation (p<0.01) was observed between body fat % and lung functions (FEV1, PEFR).

CONCLUSION

It is concluded that obese subjects are at a risk of lung function impairment, based on the criteria followed for BMI and body fat %. The study also demonstrate that body fat% classification as a better index for determination of obese subjects compared to BMI classification, with respect to lung function impairments.

Chiari malformation and central sleep apnea syndrome: efficacy of treatment with adaptive servo-ventilation

The Chiari malformation type I (CM-I) has been associated with sleep-disordered breathing, especially central sleep apnea syndrome. We report the case of a 44-year-old female with CM-I who was referred to our sleep laboratory for suspected sleep apnea. The patient had undergone decompressive surgery 3 years prior. An arterial blood gas analysis showed hypercapnia. Polysomnography showed a respiratory disturbance index of 108 events/h, and all were central apnea events. Treatment with adaptive servo-ventilation was initiated, and central apnea was resolved. This report demonstrates the efficacy of servo-ventilation in the treatment of central sleep apnea syndrome associated with alveolar hypoventilation in a CM-I patient with a history of decompressive surgery.

Perioperative lung protective ventilation in obese patients

The perioperative use and relevance of protective ventilation in surgical patients is being increasingly recognized. Obesity poses particular challenges to adequate mechanical ventilation in addition to surgical constraints, primarily by restricted lung mechanics due to excessive adiposity, frequent respiratory comorbidities (i.e. sleep apnea, asthma), and concerns of postoperative respiratory depression and other pulmonary complications. The number of surgical patients with obesity is increasing, and facing these challenges is common in the operating rooms and critical care units worldwide. In this review we summarize the existing literature which supports the following recommendations for the perioperative ventilation in obese patients: (1) the use of protective ventilation with low tidal volumes (approximately 8 mL/kg, calculated based on predicted -not actual- body weight) to avoid volutrauma; (2) a focus on lung recruitment by utilizing PEEP (8–15 cmH₂O) in addition to recruitment maneuvers during the intraoperative period, as well as incentivized deep breathing and noninvasive ventilation early in the postoperative period, to avoid atelectasis, hypoxemia and atelectrauma; and (3) a judicious oxygen use (ideally less than 0.8) to avoid hypoxemia but also possible reabsorption atelectasis. Obesity poses an additional challenge for achieving adequate protective ventilation during one-lung ventilation, but different lung isolation techniques have been adequately performed in obese patients by experienced providers. Postoperative efforts should be directed to avoid hypoventilation, atelectasis and hypoxemia. Further studies are needed to better define optimum protective ventilation strategies and analyze their impact on the perioperative outcomes of surgical patients with obesity.

Sleep-Disordered Breathing in Patients with Polycystic Liver and Kidney Disease Referred for Transcatheter Arterial Embolization

BACKGROUND AND OBJECTIVES

Sleep-disordered breathing (SDB) is prevalent among patients with CKD, but its prevalence among patients with symptomatic autosomal dominant polycystic kidney disease (ADPKD) and its association with total liver and kidney volume remain unclear.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study examined the association between height-adjusted total liver and kidney volume (htTLKV) and SDB in a cross-sectional study of 304 adult patients with symptomatic ADPKD who were hospitalized at Toranomon Hospital for transcatheter arterial embolization and who underwent pulse oximetry between April 2008 and November 2013. SDB was defined as having a 3% oxygen desaturation index of ≥15 events per hour of sleep. Logistic regression was performed with sex-specific quartiles of htTLKV as the main predictor, using patient data and comorbidities as covariates.

RESULTS

Overall (54.6% women, mean age 56.2±9.4 years, 83.5% on hemodialysis), 177 of 304 patients (58.2%) had SDB. SDB was strongly associated with htTLKV quartiles, demonstrating that odds ratios (ORs) and 95% confidence intervals (95% CIs) for SDB were 1.63 (0.76 to 3.48), 2.35 (1.09 to 5.06), and 4.61 (1.98 to 10.7) for htTLKV quartiles 2-4 (P for trend, P=0.003), respectively. Older age (OR, 1.81 per 10 years; 95% CI, 1.29 to 2.55), male sex (OR, 3.87; 95% CI, 1.96 to 7.66), receiving hemodialysis (OR, 3.46; 95% CI, 1.62 to 12.1), and higher body mass index (≥25 kg/m(2)) (OR, 3.03; 95% CI, 1.08 to 8.52) were also associated with SDB.

CONCLUSIONS

In this highly selected population of patients with symptomatic ADPKD referred for transcatheter arterial embolization, SDB was highly prevalent and independently associated with higher htTLKV.

Regional chest wall volume changes during various breathing maneuvers in normal men

PURPOSE

The purpose of this study is to investigate the regional chest wall volume changes during various breathing maneuvers in normal men with an optical reflectance system (OR), which tracks reflective markers in three dimensions.

METHODS

Chest wall volume was measured by the OR system [VL(CW)], and lung volume was measured by hot wire spirometry [VL(SP)] in 15 healthy men during quiet breathing (QB), during breathing at a rate of 50 tidal breaths/min paced using a metronome (MT: metronome-paced tachypnea), and during a maximal forced inspiratory and expiratory maneuver (MFIE maneuver).

RESULTS

There were few discrepancies between VL(CW) and VL(SP) for QB and MT. In the MFIE maneuver, however VL(CW) was often underestimated compared with VL(SP), particularly during forced maximal expiration, because of pulmonary rib cage volume changes. Furthermore, the regional chest wall volume changes were affected by breathing maneuver alternation. In the pulmonary and abdominal rib cage, inspiratory reserve volume was larger than expiratory reserve volume, respectively, and in the abdomen, expiratory reserve volume was larger than inspiratory reserve volume.

CONCLUSION

Alternation of breathing maneuvers affects regional chest wall volume changes.

Inflammation, metabolic dysregulation, and pulmonary function among obese urban adolescents with asthma

RATIONALE

Insulin resistance and low high-density lipoprotein (HDL) are associated with pulmonary morbidity, including asthma, but the underlying mechanisms are not well elucidated.

OBJECTIVES

To investigate whether systemic inflammation underlies the association of metabolic abnormalities with pulmonary function among urban adolescents.

METHODS

Th-cell responses and monocyte subsets, and their association with serum homeostatic model assessment of insulin resistance (HOMA-IR) and HDL, and pulmonary function were quantified in 168 adolescents, including 42 obese subjects with asthma, 42 normal-weight subjects with asthma, 40 obese subjects without asthma, and 44 healthy control subjects. Th-cell responses (Th1 [CD4(+)IFNγ(+)] and Th2 [CD4(+)IL4(+)] cells) to stimulation with phytohemagglutinin, leptin, and dust mite, and classical (CD14(+)CD16(-)), resident (CD14(+)CD16(+)), and patrolling (CD14dimCD16(+)) monocytes, and their C-C chemokine receptor type-2 (CCR2) expression were quantified by flow cytometry.

MEASUREMENTS AND MAIN RESULTS

Th1/Th2 ratio to all three stimuli was higher in obese subjects with asthma than normal-weight subjects with asthma and directly correlated with HOMA-IR. Classical monocytes inversely associated with Th1/Th2 ratio to phytohemagglutinin (r = -0.43; P = 0.01) and directly with Asthma Control Test score (β = 1.09; P = 0.04), while patrolling monocytes correlated with Composite Asthma Severity Index score (β = 1.11; P = 0.04) only among obese subjects with asthma. HDL was inversely associated with patrolling monocytes and directly associated with CCR2 expression on resident monocytes. CCR2 expression on patrolling monocytes predicted residual volume (RV), RV/TLC ratio, and FRC, after adjusting for HDL, but not after adjusting for body mass index. Association of Th1/Th2 ratio with RV, FRC, and inspiratory capacity was attenuated after adjusting for HOMA-IR.

CONCLUSIONS

Th1 polarization and monocyte activation among obese subjects with asthma correlates with metabolic abnormalities. Association of monocyte activation with pulmonary function is mediated by body mass index, whereas that of Th1 polarization is mediated by insulin resistance.

Association of pulmonary function with adiposity and metabolic abnormalities in urban minority adolescents

RATIONALE

Childhood obesity is a known risk factor for pulmonary diseases, likely due to obesity-mediated alteration of pulmonary function. Inflammation and mechanical fat load are two proposed causative mechanisms for altered pulmonary function among obese children; however, the association of metabolic abnormalities with pulmonary function among children is poorly understood.

OBJECTIVES

We investigated the independent association of truncal and general adiposity and metabolic abnormalities with pulmonary function in a sample of urban minority adolescents.

METHODS

Spirometry and lung volume indices were compared between adolescents with general (body mass index [BMI] > 95th percentile) or truncal adiposity (waist circumference > 90th percentile) and normal-weight (BMI < 85th percentile or waist circumference ≤ 90th percentile) and between those with metabolic abnormalities (homeostatic model assessment of insulin resistance [HOMA-IR] in the top quartile or high-density lipoprotein [HDL] < 40 mg/dl) and those with a normal metabolic profile.

MEASUREMENTS AND MAIN RESULTS

Obese adolescents had lower lung volumes, including residual volume (RV), RV/TLC ratio, expiratory reserve volume (ERV), and FRC, and higher inspiratory capacity (IC) than normal-weight adolescents, but did not differ in measures of lower airway obstruction, FEV1/FVC ratio, and mid-expiratory flow rate. Adolescents with high HOMA-IR had lower FEV1/FVC ratio, RV, RV/TLC ratio, ERV, and FRC and higher IC, whereas those with low HDL had lower FEV1/FVC and RV/TLC ratios. After adjusting for adiposity, HOMA-IR remained a predictor of ERV (β = -1.4; P = 0.02) and FEV1/FVC ratio (β = -0.5; P = 0.03), and HDL remained a predictor of FEV1/FVC ratio (β = 0.1; P = 0.01). General adiposity was a predictor of FRC (β = -0.5; P < 0.001), IC (β = 0.3; P < 0.001), RV (β = -0.8; P < 0.0001), and RV/TLC ratio (β = -0.2; P < 0.0001), and truncal adiposity was a predictor of RV (β = -20.3; P = 0.03) and FRC (β = -13.8; P = 0.004). Thus, adiposity and metabolic abnormalities were independent predictors of ERV, but only metabolic abnormalities independently predicted FEV1/FVC ratio. Although general adiposity predicted RV and RV/TLC ratio, truncal adiposity was predictive of RV and FRC, conferring additional risk above general adiposity.

CONCLUSIONS

These results suggest that metabolic abnormalities and adiposity are independently associated with pulmonary function deficits among urban adolescents. Metabolic assessment of obese adolescents may identify those at risk of developing obesity-associated pulmonary morbidity.

Association between preterm birth and thoracic musculoskeletal static alterations in adolescents

OBJECTIVE

To compare thoracic musculoskeletal static alterations in adolescents born prematurely with those born at term and investigate neonatal and post-neonatal variables associated with thoracic alterations.

METHOD

This is a cross-sectional study with 57 adolescents aged 10-15 years born prematurely and 57 adolescents born at term paired by gender and age. Photographs of the head and thorax in the front, back, and right side views were studied using a computer program. The two groups were compared in regards to: elevation of clavicles, elevation of shoulders, protrusion of the head, and anteroposterior and mediolateral thoracic length. Factor associated with thoracic disorders were evaluated by linear regression analysis.

RESULTS

The Preterm group had mean gestational age of 32.0±2.8 weeks and the birth weight was 1462±338 and 3342±430 g for the Preterm and Term adolescents, respectively. Preterm adolescents had higher elevation of the left shoulder (22.7±5.4° vs. 20.6±5.3°;sim, p=0.038) and the right shoulder (22.2±4.4° vs. 18.5±5.7°; p<0.001). Smaller protrusion of the head (27.8±6.1° vs. 32.4±7.9°; p=0.008), mediolateral thoracic length (22.9±2.3 cm vs. 25.1±3.1 cm; p<0.001) and anteroposterior thoracic length (19.7±2.2 cm vs. 21.1±3.4 cm; p<0.001) were found in preterm adolescents. By multiple regression analysis, factors associated with higher shoulder elevation were birth weight <1500 g (p<0.001) and mechanical ventilation during neonatal period >5 days (p=0.009).

CONCLUSION

Adolescents born prematurely presented greater thoracic musculoskeletal static alterations compared to those born at term. Factors associated with these alterations were: very low birth weight and longer duration of mechanical ventilation in the neonatal unit.

Respiratory symptoms, spirometric respiratory impairment, and respiratory disease in middle-aged and older persons

OBJECTIVES

To evaluate whether a novel definition of spirometric respiratory impairment from the Global Lung Initiative (GLI) is strongly associated with respiratory symptoms and, in turn, frequently establishes symptomatic respiratory disease.

DESIGN

Cross-sectional.

SETTING

Third National Health and Nutrition Examination Survey.

PARTICIPANTS

Community-dwelling individuals aged 40 to 80 (N = 7,115).

MEASUREMENTS

GLI-defined spirometric respiratory impairment (airflow obstruction and restrictive pattern), dyspnea on exertion (DOE), chronic bronchitis (CB), and wheezing.

RESULTS

Prevalence rates were 12.7% for airflow obstruction, 6.2% for restrictive pattern, 28.6% for DOE, 12.6% for CB, and 12.9% for wheezing. Airflow obstruction was associated with DOE (adjusted odds ratio (aOR) = 1.69, 95% confidence interval (CI) = 1.42-2.02), CB (aOR = 1.92, 95% CI = 1.62-2.29), and wheezing (aOR = 2.50, 95% CI = 2.08-3.00), and restrictive pattern was associated with DOE (aOR = 1.75, 95% CI = 1.36-2.25), CB (aOR = 1.39, 95% CI = 1.08-1.78), and wheezing (aOR = 1.53, 95% CI = 1.15-2.04). Nonetheless, among participants who had airflow obstruction and restrictive pattern, only a minority had DOE (38.6% and 45.5%), CB (23.3% and 15.9%), and wheezing (24.4% and 19.1%), yielding a positive predictive value (PPV) of only 53% for any respiratory symptom in the setting of any spirometric respiratory impairment. In addition, most participants who had DOE (73.0%), CB (67.8%), and wheezing (66.8%) did not have airflow obstruction or restrictive pattern, yielding a PPV of only 26% for any spirometric respiratory impairment in the setting of any respiratory symptom. The results differed only modestly when stratified according to age (40-64 vs 65-80).

CONCLUSION

GLI-defined spirometric respiratory impairment increased the likelihood of respiratory symptoms but was nonetheless a poor predictor of respiratory symptoms. Similarly, respiratory symptoms were poor predictors of GLI-defined spirometric respiratory impairment. Hence, a comprehensive assessment is needed when evaluating respiratory symptoms, even in the presence of spirometric respiratory impairment.

When obesity and chronic obstructive pulmonary disease collide. Physiological and clinical consequences

In many parts of the world, the prevalence of both chronic obstructive pulmonary disease (COPD) and obesity is increasing at an alarming rate. Such patients tend to have greater respiratory symptoms, more severe restriction of daily activities, poorer health-related quality of life, and greater health care use than their nonobese counterparts. Physiologically, increasing weight gain is associated with lung volume reduction effects in both health and disease, and this should be considered when interpreting common pulmonary function tests where lung volume is the denominator, such as FEV1/FVC and the ratio of diffusing capacity of carbon monoxide to alveolar volume, or indeed when evaluating the physiological consequences of emphysema in obese individuals. Contrary to expectation, the presence of mild to moderate obesity in COPD appears to have little deleterious effect on respiratory mechanics and muscle function, exertional dyspnea, and peak symptom-limited oxygen uptake during cardiopulmonary exercise testing. Thus, in evaluating obese patients with COPD reporting activity restriction, additional nonpulmonary factors, such as increased metabolic loading, cardiocirculatory impairment, and musculoskeletal abnormalities, should be considered. Care should be taken to recognize the presence of obstructive sleep apnea in obese patients with COPD, as effective treatment of the former condition likely conveys an important survival advantage. Finally, morbid obesity in COPD presents significant challenges to effective management, given the combined effects of erosion of the ventilatory reserve and serious metabolic and cardiovascular comorbidities that collectively predispose to an increased risk of death from respiratory failure.

Overweight and obesity in patients with cystic fibrosis: a center-based analysis

OBJECTIVE

Cystic fibrosis (CF) has long been associated with malnutrition. However, due to early diagnosis, nutritional supplements, and increased prevalence of obesity in the general population, overweight, and obesity in the CF patient population is becoming a concern. The aim of this study was to determine the prevalence of obesity and overweight in patients with CF seen at our center, to analyze factors associated with nutritional status, to evaluate the relation between nutritional status and lung function, and to document any adverse health outcomes.

METHODS

The CF Patient Registry was queried for patients aged 2-18 who were seen at our center between June 2011 and June 2012. Nutritional statuses of patients were classified in accordance with the CF Foundation guidelines. Analysis of variance was utilized to analyze the differences in lung function between the five weight status groups.

RESULTS

Of the 226 patients with CF aged 2-18 years, 129 (57%) had a BMI percentile consistent with a healthy weight status, 16 (7%) were in nutritional failure, 28 (12%) were at risk of nutritional failure, 35 (15%) were overweight, and 18 (8%) were obese. Based on fecal elastase levels, 50% of the overweight patients and 20% of the obese patients were pancreatic insufficient. FEV1 % predicted was lowest in patients with nutritional failure (P = 0.005). No significant differences were noted between the other four weight groups. In our obese and overweight population, three patients have impaired glucose tolerance, one has CF-related diabetes (CFRD) with fasting hyperglycemia, three have hypertension, and one has obstructive sleep apnea (OSA).

CONCLUSIONS

The prevalence of overweight and obesity in our CF center is noteworthy, and a significant number of the patients were pancreatic insufficient. In our patient population, overweight, and obesity were not associated with further improvement of lung function. Nutritional approaches need to address the adverse outcomes of overweight and obesity.

The longitudinal relationship of changes of adiposity to changes in pulmonary function and risk of asthma in a general adult population

BACKGROUND

Adiposity has been linked to both higher risk of asthma and reduced lung function. The effects of adiposity on asthma may depend on both atopic status and gender, while the relationship is less clear with respect to lung function. This study aimed to explore longitudinal weight changes to changes in forced expiratory volume in first second (FEV1) and forced vital capacity (FVC), as well as to incident cases of asthma and wheezing, according to atopy and gender.

METHODS

A general population sample aged 19-72 years was examined with the same methodology five years apart. Longitudinal changes in weight, body mass index, waist circumference, and fat percentage (bio-impedance) were analyzed with respect to changes of FEV1 and FVC (spirometry), and incidence of asthma and wheezing (questionnaire). Gender, atopy (serum specific IgE-positivity to inhalant allergens) and adipose tissue mass prior to adiposity changes were examined as potential effect modifiers.

RESULTS

A total of 2,308 persons participated in both baseline and five-year follow-up examinations. Over the entire span of adiposity changes, adiposity gain was associated with decreasing levels of lung function, whereas adiposity loss was associated with increasing levels of lung function. All associations were dependent on gender (p-interactions < 0.0001). For one standard deviation weight gain or weight loss, FEV1 changed with (+/-)72 ml (66-78 ml) and FVC with (+/-)103 ml (94-112 ml) in males. In females FEV1 changed with (+/-) 27 ml (22-32 ml) and FVC with (+/-) 36 ml (28-44 ml). There were no changes in the FEV1/FVC-ratio. The effect of adiposity changes increased with the level of adipose tissue mass at the start of the study (baseline), thus, indicating an aggregate effect of the total adipose tissue mass. Atopy did not modify these associations. There were no statistically significant associations between changes in adiposity measures and risk of incident asthma or wheeze.

CONCLUSIONS

Over a five-year period, increasing adiposity was associated with decreasing lung function, whereas decreasing adiposity was associated with increasing lung function. This effect was significantly greater in males than in females and increased with pre-existing adiposity, but was independent of atopy.

Systematic review of pleural plaques and lung function

Context

US EPA proposed a Reference Concentration for Libby amphibole asbestos based on the premise that pleural plaques are adverse and cause lung function deficits.

Objective

We conducted a systematic review to evaluate whether there is an association between pleural plaques and lung function and ascertain whether results were dependent on the method used to identify plaques.

Methods

Using the PubMed database, we identified studies that evaluated pleural plaques and lung function. We assessed each study for quality, then integrated evidence and assessed associations based on the Bradford Hill guidelines. We also compared the results of HRCT studies to those of X-ray studies.

Results

We identified 16 HRCT and 36 X-ray studies. We rated six HRCT and 16 X-ray studies as higher quality based on a risk-of-bias analysis. Half of the higher quality studies reported small but statistically significant mean lung function decrements associated with plaques. None of the differences were clinically significant. Many studies had limitations, such as inappropriate controls and/or insufficient adjustment for confounders. There was little consistency in the direction of effect for the most commonly reported measurements. X-ray results were more variable than HRCT results. Pleural plaques were not associated with changes in lung function over time in longitudinal studies.

Conclusion

The weight of evidence indicates that pleural plaques do not impact lung function. Observed associations are most likely due to unidentified abnormalities or other factors.

Differences in associations between visceral fat accumulation and obstructive sleep apnea by sex

RATIONALE

The difference in mortality from obstructive sleep apnea (OSA) by sex is an important issue. Visceral fat, a significant risk factor for cardiovascular disease, was reported to be closely related to OSA.

OBJECTIVES

To assess the different associations between OSA and visceral fat area (VFA) by sex, which might account for the different prognosis in men and women with OSA.

METHODS

Participants were 271 men and 100 women consecutively hospitalized for examination of OSA from October 2008 to December 2010. Among the 371 participants, relationships were analyzed between fat areas by computed tomography, comorbidity, polysomnographic data, arterial blood gas, pulmonary function, and venous blood data. Multiple regression analyses were performed to identify variables independently associated with VFA and subcutaneous fat area for each sex.

MEASUREMENTS AND MAIN RESULTS

Despite similar body mass index (BMI) and waist circumference, men had larger VFA, more severe OSA, and more severe dyslipidemia than women. Multiple regression analyses revealed that in men, not only age and BMI but also minimal oxygen saturation (contribution rate [R(2)], 4.6%) during sleep, and alveolar-arterial oxygen difference (R(2) = 7.6%) were independently associated with VFA. Conversely, VFA was associated only with BMI in women.

CONCLUSIONS

Only in men was OSA independently associated with VFA. The lesser associations between OSA and visceral fat in women might account for the lower impact of OSA on cardiovascular disease or mortality in women.

The association of weight with the detection of airflow obstruction and inhaled treatment among patients with a clinical diagnosis of COPD

BACKGROUND

Most patients with a clinical diagnosis of COPD have not had spirometry to confirm airflow obstruction (AFO). Overweight and obese patients report more dyspnea than normal weight patients, which may be falsely attributed to AFO. We sought to determine whether overweight and obese patients who received a clinical diagnosis of COPD were more likely to receive a misdiagnosis (ie, lack of AFO on spirometry) and be subsequently treated with inhaled medications.

METHODS

The cohort comprised US veterans with COPD (International Classification of Diseases, 9th Revision, code; inhaled medication use; or both) and spirometry measurements from one of three Pacific Northwest Veterans Administration Medical Centers. The measured exposures were overweight and obesity (defined by BMI categories). Outcomes were (1) AFO on spirometry and (2) escalation or deescalation of inhaled therapies from 3 months before spirometry to 9 to 12 months after spirometry. We used multivariable logistic regression with calculation of adjusted proportions for all analyses.

RESULTS

Fifty-two percent of 5,493 veterans who had received a clinical diagnosis of COPD had AFO. The adjusted proportion of patients with AFO decreased as BMI increased (P < .01 for trend). Among patients without AFO, those who were overweight and obese were less likely to remain off medications or to have therapy deescalated (adjusted proportions: normal weight, 0.69 [95% CI, 0.64-0.73]; overweight, 0.62 [95% CI, 0.58-0.65; P = .014]; obese, 0.60 [95% CI, 0.57-0.63; P = .001]).

CONCLUSIONS

Overweight and obese patients are more likely to be given a misdiagnosis of COPD and not have their inhaled medications deescalated after spirometry demonstrated no AFO. Providers may be missing potential opportunities to recognize and treat other causes of dyspnea in these patients.

Differing associations of BMI and body fat with asthma and lung function in children

BACKGROUND

Current evidence suggests that in children there is a significant, albeit weak, association between asthma and obesity. Studies generally use body mass index (BMI) in evaluating body adiposity, but there are limitations to its use.

METHOD

Children from a population-based study attending follow-up (age 11 years) were weighed, measured and had percent body (PBF) and truncal (PTF) fat assessed using bioelectrical impedance. They were skin prick tested and completed spirometry. Parents completed a validated respiratory questionnaire. Children were defined as normal or overweight according to BMI and PBF cut-offs. We tested the association between these adiposity markers with wheeze, asthma, atopy, and lung-function.

RESULTS

Six hundred forty-six children (339 male) completed follow-up. BMI z-score, PBF, and PTF were all positively associated with current wheeze (odds ratio [95% CI]: 1.27 [1.03, 1.57], P = 0.03; 1.05 [1.00, 1.09], P = 0.03; 1.04 [1.00, 1.08], P = 0.04, respectively). Similar trends were seen with asthma. However, when examining girls and boys separately, significant positive associations were found with PBF and PTF and asthma but only in girls (gender interaction P = 0.06 and 0.04, respectively). Associations between being overweight and wheezing and asthma were stronger when overweight was defined by PBF (P = 0.007, 0.03) than BMI (P > 0.05). Higher BMI was significantly associated with an increase in FEV(1) and FVC, but only in girls. Conversely, increasing body fat (PBF and PTF) was associated with reduced FEV(1) and FVC, but only in boys. No associations between adiposity and atopy were found.

CONCLUSION

All adiposity measures were associated with wheeze, asthma, and lung function. However, BMI and PBF did not have the same effects and girls and boys appear to be affected differently.

Potential role of the airway wall in the asthma of obesity

The pathogenesis of late-onset TH2-low asthma in obesity is thought to be related to weight-related decreases in lung volume, but why only a subset of individuals with obesity develop this condition is unknown. We tested the hypothesis that natural variations in both airway wall stiffness and airway wall thickness could lead to a subpopulation of hyperresponsive individuals exhibiting the symptoms of asthma in the setting of obesity. Increases in airway resistance (Raw) after airway smooth muscle stimulation were simulated using a computational model of an elastic airway embedded in elastic parenchyma. Using a range of randomly chosen values for both airway wall stiffness and thickness, we determined the resulting probability distributions of Raw responsiveness for a variety of different levels of transpulmonary pressure (Ptp). As Ptp decreased from 5 to 1 cmH2O, the resulting distributions of Raw moved toward progressively higher levels of responsiveness. With appropriate choices for the mean and standard deviation of the parameter that controls either airway wall stiffness or thickness, the model predicts a relationship between airway hyperresponsiveness and body mass index that is similar to that which has been reported in populations with obesity. We conclude that natural variations in airway wall mechanics and geometry between different individuals can potentially explain why an increasing percentage of the population exhibits the symptoms of asthma as the obesity of the population increases.

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.

Relationship between lung function and metabolic syndrome

Although the link between impaired lung function and cardiovascular events and type 2 diabetes mellitus has been recognized, the association between impaired lung function and metabolic syndrome has not been comprehensively assessed in the United States (U.S.) population. The aim of our study was to explore the association between impaired lung function and metabolic syndrome in a nationally representative sample of men and women. This cross-sectional population-based study included 8602 participants aged 20–65 years in the Third National Health and Nutrition Examination Survey (NHANES III). We examined the relationship between the different features of metabolic syndrome and lung function, including forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1). After adjusting for potential confounders such as age, body mass index, inflammatory factors, medical condition, and smoking status, participants with more components of metabolic syndrome had lower predicted values of FVC and FEV1 (p for trend <0.001 for both). Impaired pulmonary function was also associated with individual components of metabolic syndrome, such as abdominal obesity, high blood pressure, high triglycerides, and low high density lipoprotein (HDL) cholesterol (p<0.05 for all parameters). These results from a nationally representative sample of US adults suggest that a greater number of features of metabolic syndrome is strongly associated with poorer FVC and FEV1. In clinical practice, more comprehensive management strategies to address subjects with metabolic syndrome and impaired lung function need to be developed and investigated.

Obesity negatively impacts lung function in children and adolescents

OBJECTIVES

To investigate the relationship between weight status (body mass index [BMI] percentile and BMI z-score) and lung volumes in healthy children and adolescents.

HYPOTHESES

We hypothesized that: (a) there would be a significant inverse relationship between age- and sex-specific BMI distribution and functional residual capacity (FRC), and expiratory reserve volume (ERV), respectively; and (b) obese children would have significantly reduced FRC and ERV compared to their non-obese peers.

METHODS

The medical records of all individuals who successfully performed pulmonary function testing between 2000 and 2007 at two university children's hospitals were reviewed. Participants were excluded if they had cardiopulmonary, neuromuscular, or chest wall disease.

RESULTS

Of 1,469 record reviewed, 327 subjects met study criteria. Percent predicted ERV was lowest in the obese group (P < 0.001) while residual volume (RV) was lowest in the overweight and obese groups (P < 0.001). Underweight participants had a lower percent predicted forced vital capacity (FVC) (P = 0.027) and vital capacity (VC; P = 0.039). Obese participants had the lowest FEV1 /FVC (P < 0.001). A positive linear relationship existed between BMI z-score and percent predicted FVC, VC, and diffusing capacity of carbon monoxide (DLCO ). A negative linear relationship was found between BMI z-score and percent predicted FRC, ERV, RV, and absolute FEV1 /FVC.

CONCLUSIONS

Our results show that increasing weight status in children and adolescents is associated with a general reduction in lung volume measurements, which may reflect impaired lung function, increased respiratory symptoms, and decreased functional status.

Obese patients with idiopathic pulmonary fibrosis have a higher 90-day mortality risk with bilateral lung transplantation

BACKGROUND

Obese patients with idiopathic pulmonary fibrosis (IPF) have higher 90-day mortality after lung transplantation. We sought to determine whether body mass index (BMI) differentially modified the effect of transplant procedure type on 90-day mortality in IPF patients.

METHODS

We analyzed data from the Organ Procurement and Transplantation Network (OPTN) for all patients with IPF who were transplanted between 2000 and 2010. Post-transplant survival was examined using Kaplan-Meier estimates. Multivariable logistic regression modeling was used to determine the difference in 90-day survival. The primary variable of interest was the interaction term between body mass index (BMI) and transplant type.

RESULTS

A total of 3,389 (58% single-lung transplant [SLT] and 42% bilateral lung transplant [BLT]) subjects were included. Multivariable logistic regression modeling demonstrated a statistically significant interaction between BMI and transplant type (p = 0.047). Patients with a BMI > 30 kg/m(2) who received a BLT are 1.71 times (95% CI [1.03 to 2.85], p = 0.038) more likely to die within 90 days than BLT recipients with a BMI of 18.5 to 30 kg/m(2).

CONCLUSIONS

Our results suggest that obese patients who receive a BLT may be at higher risk of 90-day mortality compared with patients of normal weight. Further study is needed to obtain more detailed information about comorbidities and other risk factors for early death that are not included in the OPTN database.

Induction of IL-17A Precedes Development of Airway Hyperresponsiveness during Diet-Induced Obesity and Correlates with Complement Factor D

Obesity is a risk factor for the development of asthma. Obese mice exhibit innate airway hyperresponsiveness (AHR), a characteristic feature of asthma, and IL-17A is required for development of AHR in obese mice. The purpose of this study was to examine the temporal association between the onset of AHR and changes in IL-17A during the development of obesity by high-fat feeding in mice. At weaning, C57BL/6J mice were placed either on mouse chow or on a high-fat diet (HFD) and examined 9, 12, 15, 18, or 24 weeks later. Airway responsiveness to aerosolized methacholine (assessed via the forced oscillation technique) was greater in mice fed HFD versus chow for 24 weeks but not at earlier time points. Bronchoalveolar lavage and serum IL-17A were not affected by either the type or duration of diet, but increased pulmonary IL17a mRNA abundance was observed in HFD versus chow fed mice after both 18 and 24 weeks. Flow cytometry also confirmed an increase in IL-17A(+) γδ T cells and IL-17A(+) CD4(+) T (Th17) cells in lungs of HFD versus chow fed mice. Pulmonary expression of Cfd (complement factor D, adipsin), a gene whose expression can be reduced by IL-17A, decreased after both 18 and 24 weeks in HFD versus chow fed mice. Furthermore, pulmonary Cfd mRNA abundance correlated with elevations in pulmonary Il17a mRNA expression and with AHR. Serum levels of TNFα, MIP-1α, and MIP-1β, and classical markers of systemic inflammation of obesity were significantly greater in HFD than chow fed mice after 24 weeks, but not earlier. In conclusion, our data indicate that pulmonary rather than systemic IL-17A is important for obesity-related AHR and suggest that changes in pulmonary Cfd expression contribute to these effects of IL-17A. Further, the observation that increases in Il17a preceded the development of AHR by several weeks suggests that IL-17A interacts with other factors to promote AHR. The observation that the onset of the systemic inflammation of obesity coincided temporally with the development of AHR suggest that systemic inflammation may be one of these factors.

Obesity hypoventilation syndrome in Japan and independent determinants of arterial carbon dioxide levels

BACKGROUND AND OBJECTIVE

Obesity hypoventilation syndrome (OHS) prevalence was previously estimated at 9% in patients with obstructive sleep apnoea (OSA) in Japan. However, the definition of OSA in that study was based on an apnoea-hypopnoea index (AHI) of ≥ 20/h rather than ≥ 5/h. Therefore, the prevalence of OHS in OSA was not measured in the same way as for Western countries. Our study objectives were to investigate the characteristics of Japanese patients with OHS.

METHODS

Nine hundred eighty-one consecutive patients investigated for suspected OSA were enrolled. At least 90% of them were from urban areas, including 162 with obese OSA (body mass index (BMI) ≥ 30 kg/m(2) and AHI ≥ 5/h).

RESULTS

The prevalence of OHS (BMI 36.7 ± 4.9 kg/m(2) ) in OSA and that in obese OSA were 2.3% and 12.3%, respectively. Multiple regression analysis revealed that independent of age and BMI, arterial oxygen pressure (contribution rate (R(2) ) = 7.7%), 4% oxygen desaturation index (R(2)  = 8.9%), carbon monoxide diffusing capacity/alveolar volume (R(2)  = 8.3%), haemoglobin concentration (R(2)  = 4.9%) and waist circumference (R(2)  = 4.9%) were independently associated with arterial carbon dioxide pressure. After 12.3 ± 4.6 months of CPAP treatment, more than 60% of OHS patients no longer had hypercapnia.

CONCLUSIONS

The prevalence of OHS in OSA in Japan was 2.3%. The mean BMI of patients with OHS in Japan was lower than that in Western countries (36.7 kg/m(2) vs 44.0 kg/m(2) ).

Adiposity, fractional exhaled nitric oxide, and asthma in U.S. children

RATIONALE

Whether allergic airway inflammation mediates the association between overweight or obesity and childhood asthma is unknown.

OBJECTIVES

To examine adiposity, asthma, and fractional exhaled nitric oxide (FeNO) in U.S. children.

METHODS

Cross-sectional study of indicators of adiposity or obesity, FeNO (a biomarker of eosinophilic airway inflammation), and asthma in 2,681 children aged 6-17 years in the 2007-2010 National Health and Nutrition Examination Survey. Adiposity measures included body mass index (BMI), percent body fat (PBF), and waist circumference (WC).

MEASUREMENTS AND MAIN RESULTS

BMI, PBF, and WC were associated with asthma among children with low FeNO (odds ratio, 1.54-1.68; P < 0.01), but not among children with increased FeNO. Among children without asthma, BMI, PBF, and WC were associated with higher FEV1 and FVC, and lower FEV1/FVC. Among children with asthma and a high FeNO, all adiposity indicators were associated with decreased FEV1/FVC (β = -1.5% to -1.7% per z score) but not with FEV1 or FVC. Higher BMI or PBF was associated with worse asthma severity or control in children with asthma and increased FeNO, but not in children with asthma and low FeNO. Similar results were obtained in a secondary multivariate analysis of overweight or obesity (defined as BMI ≥85th percentile) and asthma or indicators of asthma severity or control, stratified by FeNO level.

CONCLUSIONS

Adiposity indicators are associated with asthma in children with low FeNO. Among children with asthma, adiposity indicators are associated with worse asthma severity or control in those with high FeNO.

Obesity and its impact on the respiratory system

Obesity has complex and incompletely understood effects upon the respiratory system in childhood, which differs in some aspects to those seen in adults. There is increasing evidence that excess adiposity will impact negatively upon static and dynamic respiratory function as measured through lung volumes, lung compartment mechanics, measures of airway function and exercise capability to varying degrees. Further information is needed to better understand the effects in children, and the importance of onset and duration of obesity on subsequent outcomes. Consensus about how best to express adiposity is also an essential part of this process and fat distribution is another important factor. From a clinical standpoint this creates challenges in distinguishing a deconditioned obese young person from a non-atopic asthmatic because of symptom overlap and lung function testing results, including responses seen during airway challenges. There is evidence to support the role of weight loss in achieving normalisation of lung function parameters, but as always with obesity there are enormous challenges in realising this goal for many subjects.

Obesity in kidney disease: A heavyweight opponent

Obesity is an important worldwide challenge that must be faced in most developed and developing countries because of unhealthy nutritional habits. The consequences of obesity and being overweight are observed in different organs, but the kidney is one of the most affected. Excess adipose tissue causes hemodynamic alterations in the kidney that can result in renal disease. However, obesity is also commonly associated with other comorbidities such as chronic inflammation, hypertension and diabetes. This association of several aggravating factors is still a matter of concern in clinical and basic research because the pathophysiologic mechanisms surrounding chronic kidney disease development in obese patients remain unclear. This review will discuss the consequences of obesity in the context of renal injury.

Evaluation of a semiautomated lung mass calculation technique for internal dosimetry applications

PURPOSE

The authors sought to evaluate a simple, semiautomated lung mass estimation method using computed tomography (CT) scans obtained using a variety of acquisition techniques and reconstruction parameters for mass correction of medical internal radiation dose-based internal radionuclide radiation absorbed dose estimates.

METHODS

CT scans of 27 patients with lung cancer undergoing stereotactic body radiation therapy treatment planning with PET∕CT were analyzed retrospectively. For each patient, free-breathing (FB) and respiratory-gated 4DCT scans were acquired. The 4DCT scans were sorted into ten respiratory phases, representing one complete respiratory cycle. An average CT reconstruction was derived from the ten-phase reconstructions. Mid expiration breath-hold CT scans were acquired in the same session for many patients. Deep inspiration breath-hold diagnostic CT scans of many of the patients were obtained from different scanning sessions at similar time points to evaluate the effect of contrast administration and maximum inspiration breath-hold. Lung mass estimates were obtained using all CT scan types, and intercomparisons made to assess lung mass variation according to scan type. Lung mass estimates using the FB CT scans from PET∕CT examinations of another group of ten male and ten female patients who were 21-30 years old and did not have lung disease were calculated and compared with reference lung mass values. To evaluate the effect of varying CT acquisition and reconstruction parameters on lung mass estimation, an anthropomorphic chest phantom was scanned and reconstructed with different CT parameters. CT images of the lungs were segmented using the OsiriX MD software program with a seed point of about -850 HU and an interval of 1000. Lung volume, and mean lung, tissue, and air HUs were recorded for each scan. Lung mass was calculated by assuming each voxel was a linear combination of only air and tissue. The specific gravity of lung volume was calculated using the formula (lung HU - air HU)∕(tissue HU - air HU), and mass = specific gravity × total volume × 1.04 g∕cm(3).

RESULTS

The range of calculated lung masses was 0.51-1.29 kg. The average male and female lung masses during FB CT were 0.80 and 0.71 kg, respectively. The calculated lung mass varied across the respiratory cycle but changed to a lesser degree than did lung volume measurements (7.3% versus 15.4%). Lung masses calculated using deep inspiration breath-hold and average CT were significantly larger (p < 0.05) than were some masses calculated using respiratory-phase and FB CT. Increased voxel size and smooth reconstruction kernels led to high lung mass estimates owing to partial volume effects.

CONCLUSIONS

Organ mass correction is an important component of patient-specific internal radionuclide dosimetry. Lung mass calculation necessitates scan-based density correction to account for volume changes owing to respiration. The range of lung masses in the authors' patient population represents lung doses for the same absorbed energy differing from 25% below to 64% above the dose found using reference phantom organ masses. With proper management of acquisition parameters and selection of FB or midexpiration breath hold scans, lung mass estimates with about 10% population precision may be achieved.

Influence of diet and obesity on COPD development and outcomes

The global increase in the prevalence and incidence of obesity has called serious attention to this issue as a major public health concern. Obesity is associated with many chronic diseases, including cardiovascular disease and diabetes, and recently the role of overweight and obesity in lung disease has received new interest. Independently of obesity, diet also plays a role as a risk factor for many chronic diseases, and evidence is accumulating to support a role for diet in the prevention and management of several lung diseases. Chronic obstructive lung disease is the third-leading cause of death globally, and both obesity and diet appear to play roles in its pathophysiology. Obesity has been associated with decreased lung-function measures in population-based studies, with increased prevalence of several lung diseases and with compromised pulmonary function. In contrast, obesity has a protective effect against mortality in severe chronic obstructive pulmonary disease (COPD). Nutrient intake and dietary patterns have also been associated with lung-function measures and the development and progression of COPD. Taken together, this suggests that a focus on obesity and diet should be part of public health campaigns to reduce the burden of lung disease, and could have important implications for clinicians in the management of their patients. Future research should also focus on elucidating these relationships in diverse populations and age-groups, and on understanding the complex interaction between behavior, environment, and genetics in the development and progression of COPD. The goal of this article is to review current evidence regarding the role that obesity and diet play in the development of COPD, and in COPD-related outcomes.

Occupational risk factors for COPD phenotypes in the Multi-Ethnic Study of Atherosclerosis (MESA) Lung Study

INTRODUCTION

The contribution of occupational exposure to the risk of chronic obstructive pulmonary disease COPD in population-based studies is of interest. We compared the performance of self-reported exposure to a newly developed JEM in exposure-response evaluation.

METHODS

We used cross-sectional data from Multi-Ethnic Study of Atherosclerosis (MESA), a population-based sample of 45-84 year olds free of clinical cardiovascular disease at baseline. MESA ascertained the most recent job and employment, and the MESA Lung Study measured spirometry, and occupational exposures for 3686 participants. Associations between health outcomes (spirometry defined airflow limitation and Medical Research Council-defined chronic bronchitis) and occupational exposure [self-reported occupational exposure to vapor-gas, dust, or fumes (VGDF), severity of exposure, and a job-exposure matrix (JEM)-derived score] were evaluated using logistic regression models adjusted for non-occupational risk factors.

RESULTS

The prevalence of airflow limitation was associated with self-reported exposure to vapor-gas (OR 2.6, 95%CI 1.1-2.3), severity of VGDF exposure (P-trend < 0.01), and JEM dust exposure (OR 2.4, 95%CI 1.1-5.0), and with organic dust exposure in females; these associations were generally of greater magnitude among never smokers. The prevalence of chronic bronchitis and wheeze was associated with exposure to VGDF. The association between airflow limitation and the combined effect of smoking and VGDF exposure showed an increasing trend. Self-reported vapor-gas, dust, fumes, years and severity of exposure were associated with increased prevalence of chronic bronchitis and wheeze (P < 0.001).

CONCLUSIONS

Airflow limitation was associated with self-reported VGDF exposure, its severity, and JEM-ascertained dust exposure in smokers and never-smokers in this multiethnic study.

Continuous positive airway pressure/pressure support pre-oxygenation of morbidly obese patients

BACKGROUND

Morbidly obese patients are more prone to desaturation of arterial blood during apnea with induction of anesthesia than are non-obese. This study aimed to assess the effect of low-pressure continuous positive airway pressure (CPAP) with pressure support ventilation (PSV) during pre-oxygenation on partial oxygen pressure in arterial blood (PaO2 ) immediately after tracheal intubation (post-intubation PaO2).

METHODS

Forty-four adult patients scheduled for laparoscopic gastric bypass surgery were pre-oxygenated with 80% O2 for 2 min, randomized either to CPAP 5 cm H2O + PSV 5 cm H2O (CPAP/PSV, n = 22) or neutral-pressure breathing without CPAP/PSV (control, n = 22). Anesthesia was induced in a rapid-sequence protocol and the trachea was intubated without prior mask ventilation. Arterial blood gases were measured before pre-oxygenation, before induction of anesthesia, and immediately following intubation, before the first positive pressure breath.

RESULTS

After pre-oxygenation, partial carbondioxide pressure was significantly lower in the CPAP/PSV group (4.9 ± 0.5 kPa), (mean ± standard deviation) than in the control group (5.2 ± 0.7 kPa) (P = 0.025). Post-preoxygenation PaO2 did not differ between the groups, but post-intubation PaO2 was significantly higher in the CPAP/PSV group (32.2 ± 4.1 kPa) than in the control group (23.8 ± 8.8 kPa) (P < 0.001). In the control group, nadir oxygen saturation was lower (median 98%, range 83-99%) than in the CPAP/PSV group (median 99%, range 97-99%, P = 0.011).

CONCLUSIONS

In morbidly obese patients, low-pressure CPAP combined with low-pressure PSV during pre-oxygenation resulted in better oxygenation, compared with neutral-pressure breathing, and prevented desaturation episodes.

Effect of exercise test on pulmonary function of obese adolescents

OBJECTIVE

to investigate the pulmonary response to exercise of non-morbidly obese adolescents, considering the gender.

METHODS

a prospective cross-sectional study was conducted with 92 adolescents (47 obese and 45 eutrophic), divided in four groups according to obesity and gender. Anthropometric parameters, pulmonary function (spirometry and oxygen saturation [SatO2]), heart rate (HR), blood pressure (BP), respiratory rate (RR), and respiratory muscle strength were measured. Pulmonary function parameters were measured before, during, and after the exercise test.

RESULTS

BP and HR were higher in obese individuals during the exercise test (p = 0.0001). SatO2 values decreased during exercise in obese adolescents (p = 0.0001). Obese males had higher levels of maximum inspiratory and expiratory pressures (p = 0.0002) when compared to obese and eutrophic females. Obese males showed lower values of maximum voluntary ventilation, forced vital capacity, and forced expiratory volume in the first second when compared to eutrophic males, before and after exercise (p = 0.0005). Obese females had greater inspiratory capacity compared to eutrophic females (p = 0.0001). Expiratory reserve volume was lower in obese subjects when compared to controls (p ≤ 0,05).

CONCLUSION

obese adolescents presented changes in pulmonary function at rest and these changes remained present during exercise. The spirometric and cardiorespiratory values were different in the four study groups. The present data demonstrated that, in spite of differences in lung growth, the model of fat distribution alters pulmonary function differently in obese female and male adolescents.

Phenotype, endotype and patient-specific computational modelling for optimal treatment design in asthma

Understanding and treatment of asthma is significantly complicated by the heterogeneous spectrum of phenotypes associated with the disease. Recent advances in phenotype classification promise more targeted therapies, but these categories are based on constellations of largely external measurements and are not necessarily indicative of underlying pathophysiology. We propose that computational modelling is a valuable tool that allows the disease spectrum to be decomposed not into phenotypes but rather into groups organized by underlying dysfunction, referred to by some authors as endotypes. By breaking down the asthmatic spectrum in this way, therapies can be targeted more directly to the underlying defects. This would be not only an important improvement in its own right, but also an important step toward the ultimate goal of patient-specific modelling.