Work of breathing and respiratory drive in obesity

Pathophysiology of Chronic Hypercapnic Respiratory Failure

Chronic hypercapnic respiratory failure occurs in several conditions associated with hypoventilation. The mechanisms underlying the development of chronic hypercapnia include a combination of processes that increase metabolic CO2 production, reduce minute ventilation (V'e), or increase dead space fraction (Vd/Vt). Fundamental to the pathophysiology is a mismatch between increased load and a reduction in the capacity of the respiratory pump to compensate. Though neural respiratory drive may be decreased in a subset of central hypoventilation disorders, it is more commonly increased in attempting to maintain the load-capacity homeostatic balance.

Obesity-related reduced spirometry and altered breathing pattern are associated with mechanical disadvantage of the diaphragm

The aim of this study was to characterize the breathing patterns of individuals with obesity during routine activities such as sitting and standing, and to identify potential contributors to alterations in these patterns. Measurements performed in 20 male subjects with obesity (BMI, 31.8±1.5 kg/m2) and 20 controls (BMI, 23.5±1.4 kg/m2) included anthropometric parameters, breathing-patterns in sitting and standing positions, spirometry, maximal respiratory pressures, and diaphragm B-mode ultrasonography. Individuals with obesity exhibited lower tidal volume and increased respiratory rate to maintain a similar minute-ventilation (p<0.05). Subjects with obesity demonstrated impaired spirometry and respiratory muscle strength, with inspiratory functions being notably compromised (p<0.05). Individuals with obesity had a greater diaphragm thickness at end inspiration but lower thickening-fraction at end quiet and forced breathings and reduced diaphragmatic displacement and excursion during maximal breaths (p<0.05). BMI was negatively associated with all respiratory function markers (p<0.05). Individuals with obesity exhibit a higher respiratory rate but lower tidal volume, likely to accommodate decreased compliance and excess thoracic and abdominal fat, further hindering inspiratory function. Moreover, increased adiposity is associated with a thicker but weaker diaphragm, primarily due to the diaphragm's mechanical disadvantage rather than its intrinsic inability to generate force.

Differences in Anthropometric, Sleep and Respiratory Characteristics between Hypercapnic and Normocapnic Patients with COPD-OSA Overlap Syndrome

BACKGROUND

Overlap syndrome (OS), the coexistence of chronic obstructive pulmonary disease and obstructive sleep apnea, is frequently characterized by the presence of daytime hypercapnia (pCO2 ≥ 45 mmHg). The aim of this study was to investigate potential differences in anthropometric, sleep and respiratory characteristics between hypercapnic and normocapnic patients with OS.

METHODS

Consecutive patients who underwent polysomnography, pulmonary function testing and arterial blood gases and had been diagnosed with OS were enrolled in the study.

RESULTS

According to pCO2 levels in wakefulness, the patients were divided into group A, consisting of OS patients without hypercapnia (n = 108) or group B, consisting of OS patients with hypercapnia (n = 55). The majority of included patients in both groups were males (n = 92 in group A vs. n = 50 in group B). Group B had increased BMI (p = 0.001), neck (p = 0.017) and waist circumference (p = 0.013), higher scores in Epworth sleepiness scale (ESS) (p = 0.008), increased sleep efficiency (p = 0.033), oxygen desaturation index (p = 0.004) and time with oxyhemoglobin saturation <90% (p = 0.006) than group A. Also, Group B had decreased average and minimum oxyhemoglobin saturation during sleep (p < 0.001). Hypercapnic patients had lower FEV1% (p = 0.003), FVC% (p = 0.004), pO2 and pCO2 (p < 0.001 for both) values compared with normocapnic patients. In binary regression analysis, which assessed various predictors on the likelihood of having hypercapnia, it was found that BMI (OR: 1.313, 95% CI: 1.048-1.646, p = 0.018) and FVC (OR: 0.913, 95% CI: 0.845-0.986, p = 0.020) were the major determinants of hypercapnia in OS patients.

CONCLUSIONS

Hypercapnic OS patients were more obese and sleepy and presented worse respiratory function in wakefulness and sleep hypoxia characteristics compared with normocapnic OS patients.

The Role of Obstructive Sleep Apnea in Hypercapnic Respiratory Failure Identified in Critical Care, Inpatient, and Outpatient Settings

An emerging body of literature describes the prevalence and consequences of hypercapnic respiratory failure. While device qualifications, documentation practices, and previously performed clinical studies often encourage conceptualizing patients as having a single "cause" of hypercapnia, many patients encountered in practice have several contributing conditions. Physiologic and epidemiologic data suggest that sleep-disordered breathing-particularly obstructive sleep apnea (OSA)-often contributes to the development of hypercapnia. In this review, the authors summarize the frequency of contributing conditions to hypercapnic respiratory failure among patients identified in critical care, emergency, and inpatient settings with an aim toward understanding the contribution of OSA to the development of hypercapnia.

The Metabolic Syndrome, a Human Disease

This review focuses on the question of metabolic syndrome (MS) being a complex, but essentially monophyletic, galaxy of associated diseases/disorders, or just a syndrome of related but rather independent pathologies. The human nature of MS (its exceptionality in Nature and its close interdependence with human action and evolution) is presented and discussed. The text also describes the close interdependence of its components, with special emphasis on the description of their interrelations (including their syndromic development and recruitment), as well as their consequences upon energy handling and partition. The main theories on MS's origin and development are presented in relation to hepatic steatosis, type 2 diabetes, and obesity, but encompass most of the MS components described so far. The differential effects of sex and its biological consequences are considered under the light of human social needs and evolution, which are also directly related to MS epidemiology, severity, and relations with senescence. The triggering and maintenance factors of MS are discussed, with especial emphasis on inflammation, a complex process affecting different levels of organization and which is a critical element for MS development. Inflammation is also related to the operation of connective tissue (including the adipose organ) and the widely studied and acknowledged influence of diet. The role of diet composition, including the transcendence of the anaplerotic maintenance of the Krebs cycle from dietary amino acid supply (and its timing), is developed in the context of testosterone and β-estradiol control of the insulin-glycaemia hepatic core system of carbohydrate-triacylglycerol energy handling. The high probability of MS acting as a unique complex biological control system (essentially monophyletic) is presented, together with additional perspectives/considerations on the treatment of this 'very' human disease.

A history of home mechanical ventilation: The past, present and future

This state-of-the-art review provides an overview of the history of home mechanical ventilation (HMV), including early descriptions of mechanical ventilation from ancient and Renaissance perspectives and the mass development of ventilators designed for long-term use during the poliomyelitis epidemic. Seminal data from key clinical trials supports the application of HMV in certain patients with chronic obstructive pulmonary disease, neuromuscular disease and obesity-related respiratory failure. Innovative engineering coupled with refined physiological understanding now permits widespread delivery of home mechanical ventilation to a global population, using portable devices with advanced ventilatory modes and telemonitoring capabilities. Exponential growth in digital technology continues, and ongoing research is needed to understand how to harness clinical and physiological data to benefit patients and healthcare services in a clinically- and cost-effective manner.

Association of Low Arousal Threshold Obstructive Sleep Apnea Manifestations with Body Fat and Water Distribution

Obstructive sleep apnea (OSA) with a low arousal threshold (low-ArTH) phenotype can cause minor respiratory events that exacerbate sleep fragmentation. Although anthropometric features may affect the risk of low-ArTH OSA, the associations and underlying mechanisms require further investigation. This study investigated the relationships of body fat and water distribution with polysomnography parameters by using data from a sleep center database. The derived data were classified as those for low-ArTH in accordance with criteria that considered oximetry and the frequency and type fraction of respiratory events and analyzed using mean comparison and regression approaches. The low-ArTH group members (n = 1850) were significantly older and had a higher visceral fat level, body fat percentage, trunk-to-limb fat ratio, and extracellular-to-intracellular (E-I) water ratio compared with the non-OSA group members (n = 368). Significant associations of body fat percentage (odds ratio [OR]: 1.58, 95% confident interval [CI]: 1.08 to 2.3, p < 0.05), trunk-to-limb fat ratio (OR: 1.22, 95% CI: 1.04 to 1.43, p < 0.05), and E-I water ratio (OR: 1.32, 95% CI: 1.08 to 1.62, p < 0.01) with the risk of low-ArTH OSA were noted after adjustments for sex, age, and body mass index. These observations suggest that increased truncal adiposity and extracellular water are associated with a higher risk of low-ArTH OSA.

Acute hypercapnic respiratory failure in patients with obesity hypoventilation syndrome during the COVID-19 pandemic: Four case reports

Obesity hypoventilation syndrome (OHS) can cause acute hypercapnic respiratory failure (AHRF). The onset of AHRF in four patients with OHS during the coronavirus disease 2019 (COVID-19) pandemic is reported in this study. Two men (23 and 45 years old) and two women (both 77 years old) presented to our hospital with AHRF. In the two elderly women, a prolonged supine position due to falls seemed to be the cause of AHRF. Treatment was started with bilevel positive airway pressure for all patients. While one patient died, the condition of the other three improved; they were discharged with continuous positive airway pressure. AHRF due to OHS was rarely reported in the rural region of Japan. It is suggested that increased rates of obesity due to lifestyle changes during the COVID-19 pandemic may be responsible for an increase in the prevalence of OHS-associated AHRF.

Respiratory Muscle Interval Training Improves Exercise Capacity in Obese Adolescents during a 3-Week In-Hospital Multidisciplinary Body Weight Reduction Program

The purpose of this study was to determine whether a novel approach of interval training targeted to the respiratory muscles (RMIT; normocapnic hyperpnea with resistance) in addition to a multidisciplinary in-hospital body weight reduction program (BWRP) was able to improve the integrative response to exercise in young patients with obesity. Nine male patients (17.9 ± 4.9 (x ± SD) years; 113.8 ± 16.3 kg) underwent 12 sessions of RMIT and eight age-and sex-matched patients underwent 12 sessions of a sham protocol (CTRL) during the same 3-week BWRP. Before and after the interventions the patients performed an incremental and a heavy-intensity constant work-rate (CWR>GET) cycling exercise to voluntary exhaustion. Body mass decreased by ~4.0 kg after both RMIT (p = 0.0001) and CTRL (p = 0.0002). Peak pulmonary O₂ uptake (V˙O₂) increased after RMIT (p = 0.02) and CTRL (p = 0.0007). During CWR>GET at ISO-time, V˙O₂ (p = 0.0007), pulmonary ventilation (p = 0.01), heart rate (p = 0.02), perceived respiratory discomfort (RPE_R; p = 0.03) and leg effort (p = 0.0003) decreased after RMIT; only RPE_R (p = 0.03) decreased after CTRL. Time to exhaustion increased after RMIT (p = 0.0003) but not after CTRL. In young patients with obesity, RMIT inserted in a 3-week BWRP reduced the cardiorespiratory burden, the metabolic cost, the perceived effort, and improved exercise tolerance during heavy-intensity cycling.

Role of body mass index in outcomes of patients hospitalized with COVID-19 illness

Background

Since the start of coronavirus disease 2019 (COVID-19) pandemic, several studies have linked obesity with severity of illness as well as mortality in patients with COVID-19. Outcomes of patients with overweight or obesity, who develop critical illness, have been studied extensively over the past decade where the studies have shown conflicting results. In this study, we aimed to assess the association between the body mass index (BMI) classes and outcomes among hospitalized patients with COVID-19.

Methods

This was a retrospective chart review of all adults admitted to our hospital with COVID-19 illness between 1 March 2020 and 30 June 2020. Patients were divided into four groups based on their BMI range as follows: patients with underweight (BMI < 18.5 kg/m2), patients with normal weight (BMI 18.5-24.9 kg/m2), patients with overweight (BMI 25-29.9 kg/m2), and patients with obesity (BMI ≥ 30 kg/m2).

Results

1274 patients were admitted during the study period. There were 24 (1.9%) patients with underweight, 268 (21%) patients with normal weight, 445 (34.9%) patients with overweight, and 537 (42.2%) patients with obesity. Patients with obesity were younger (p < 0.001) and there were more females among patients with underweight and patients with obesity (54% and 48% respectively, p < 0.001). There were no differences in subgroup with regards to presence of hypertension, diabetes mellitus, coronary artery disease, congestive heart failure, and dyslipidemia. In a multivariate logistic regression model, patients with overweight and patients with obesity had higher odds of requiring mechanical ventilation. BMI class was not associated with difference in survival time in a multivariate analysis.

Conclusions

In our large single-center study of hospitalized patients with COVID-19, patients with overweight and obesity had higher need for mechanical ventilation but had similar mortality when compared to patients with normal weight and underweight.

Risk factors for acute mountain sickness in travellers to Cusco, Peru: coca leaves, obesity and sex

BACKGROUND

Acute mountain sickness (AMS) may occur after rapid ascents to altitudes >2500 m. Cusco (3350 m) in Peru is a popular destination for altitude inexperienced travellers. This study aimed at evaluating the incidence and risk factors for AMS among a cohort of foreign Spanish language students in Cusco.

METHODS

We performed a cohort study among young healthy foreign Spanish language students arriving to Cusco between 2012 and 2016. Consenting students answered an enrollment questionnaire on demographics, travel history and intended AMS preventive behaviour within 48 h of arrival. At 4-5 days after enrollment participants answered a second questionnaire about actual preventive behaviour before symptoms and the development of symptoms compatible with AMS during their first 48 h in Cusco. We used the 2018 Lake Louise Scoring System for AMS diagnosis. Participants with headache and a score ≥ 3 were considered to have AMS.

RESULTS

We enrolled 142 language students, the median age was 21 years (interquartile range 20-25) and 57% were female. Participants decreased physical activity (38%), increased fluid intake (34%), drank coca leaf tea (34%), took acetazolamide (16%) and acclimatized at a lower altitude (6%) to prevent AMS. Thirty-nine percent had AMS. In the multivariate analysis, obesity [odds ratio (OR) 14.45 (2.33-89.6)] and female sex [OR 4.32 (1.81-10.28)] were associated with increased risk of AMS. Taking acetazolamide [OR 0.13 (0.03-0.56)] was associated with decreased AMS risk. Consumption of coca leaf tea was not associated with decreased risk of AMS.

CONCLUSIONS

In our cohort, AMS affected two out of five travellers. Obesity and female sex were associated with increased risk. Drinking coca leaf tea for prevention did not decrease the risk of AMS. Acetazolamide prophylaxis was associated with decreased risk of AMS.

OSA and Chronic Respiratory Disease: Mechanisms and Epidemiology

Obstructive sleep apnea (OSA) is a highly prevalent disorder that has profound implications on the outcomes of patients with chronic lung disease. The hallmark of OSA is a collapse of the oropharynx resulting in a transient reduction in airflow, large intrathoracic pressure swings, and intermittent hypoxia and hypercapnia. The subsequent cytokine-mediated inflammatory cascade, coupled with tractional lung injury, damages the lungs and may worsen several conditions, including chronic obstructive pulmonary disease, asthma, interstitial lung disease, and pulmonary hypertension. Further complicating this is the sleep fragmentation and deterioration of sleep quality that occurs because of OSA, which can compound the fatigue and physical exhaustion often experienced by patients due to their chronic lung disease. For patients with many pulmonary disorders, the available evidence suggests that the prompt recognition and treatment of sleep-disordered breathing improves their quality of life and may also alter the course of their illness. However, more robust studies are needed to truly understand this relationship and the impacts of confounding comorbidities such as obesity and gastroesophageal reflux disease. Clinicians taking care of patients with chronic pulmonary disease should screen and treat patients for OSA, given the complex bidirectional relationship OSA has with chronic lung disease.

Inflammation and oxidative stress, the links between obesity and COVID-19: a narrative review

COVID-19, an acute respiratory disease caused by SARS-CoV-2, has rapidly become a pandemic. On the other hand, obesity is also reaching dramatic dimensions and it is a risk factor for morbidity and premature mortality. Obesity has been linked to a high risk of serious-associated complications to COVID-19, due to the increased risk of concomitant chronic diseases, which highlights the health public relevance of the topic. Obese subjects have a pro-inflammatory environment, which can further exacerbate COVID-19-induced inflammation and oxidative stress, explaining the increased risk of serious complications in these patients. Another factor that favors infection in obese patients is the high expression of ACE2 receptors in the adipose tissue. The negative impact of COVID-19 in obesity is also associated with a decrease in respiratory function, the concurrence of multiple comorbidities, a low-degree chronic inflammatory state, immunocompromised situation, and therefore a higher rate of hospitalization, mechanical ventilation, in-hospital complications such as pneumonia, and death. In this review, the link between obesity and COVID-19 was analyzed, exploring the potential common mechanisms in both diseases, with special attention to oxidative stress and inflammation, due to the crucial role of both pathways in the development of the disease.

Evaluation of obesity and asthma as risk factors for moderate to severe obstructive sleep apnea in children

STUDY OBJECTIVES

Asthma and obesity are risk factors for obstructive sleep apnea (OSA) in children but their link to OSA severity is uncertain. We aimed at determining whether asthma or obesity were associated with an increased risk of moderate/severe OSA.

METHODS

Children undergoing a one-night polysomnography for suspicion of OSA were retrospectively included. Univariate and multivariate analyses were conducted to assess the clinical and demographic characteristics linked to moderate/severe OSA (obstructive apnea-hypopnea index ≥ 5/h of sleep) with odds ratio (OR) and 95% confidence interval reported.

RESULTS

490 children (311 (64%) boys) were included with a median [25th; 75th percentile] age of 8.7 [5.4; 12.9] years, 164 (33%) non-asthmatics non-obese, 122 (25%) obese non-asthmatics, 125 (26%) asthmatics non-obese, 79 (16%) asthmatics and obese. Moderate/severe OSA was present in 157 (32%) children (75/157 (48%) obese and 52/157 (33%) asthmatics). Independent factors associated with increased or decreased risk of moderate/severe OSA were: obesity and male sex (OR 1.82 [1.16; 2.87], P = 0.01, and 1.55 [1.02; 2.36], P = 0.04, respectively), and current asthma, age >6 years or behavioral disorders (OR 0.45 [0.29; 0.70], P < 0.001; 0.44 [0.27; 0.73], P < 0.001; and 0.55 [0.33; 0.92], P = 0.02, respectively). Abnormal resistance of the respiratory system (measured in 241 children), but not abnormal spirometry (measured in 213 children), increased the risk of moderate/severe OSA (OR 2.95 [1.46-5.96], P = 0.003).

CONCLUSIONS

In our cohort enriched in obese and asthmatic children, obesity was associated with higher risk of moderate/severe OSA whereas current asthma was not.

Intraoperative protective lung ventilation strategies in patients with morbid obesity

Postoperative pulmonary complications (PPCs) occur frequently and are associated with a prolonged hospital stay, increased mortality, and high costs. Patients with morbid obesity are at higher risk of perioperative complications, in particular associated with those related to respiratory function. One of the most prominent concerns of the anesthesiologists while taking care of the patient with obesity in the perioperative setting should be the status of the lung and delivery of mechanical ventilation as its strategy affects clinical outcomes. Negative effects of mechanical ventilation on the respiratory system known as ventilator-induced lung injury include barotrauma, volutrauma, and atelectrauma. However, the optimal regimen of mechanical ventilation still remains a matter of debate. While low tidal volume (VT) strategy has become a widely accepted standard of care, the protective role of PEEP and recruitment maneuvers is less clear. This review focuses on the pathophysiology of respiratory function in patients with morbid obesity, the effects of mechanical ventilation on the lungs, and optimal intraoperative strategy based on the current state of knowledge.

Analysis of Blood Pressure and Ventilation Efficiency in Different Types of Obesity Aged 40-60 Years by Cardiopulmonary Exercise Test

PURPOSE

This study investigated blood pressure and ventilation efficiency by cardiopulmonary exercise test (CPX) in different types of obesity aged 40-60 years.

MATERIAL AND METHODS

The inclusion criteria of this cross-sectional study were adults aged 40-60 years underwent health checks. CPX was measured according to the relevant standards. According to different body mass index (BMI), there were 3 groups, BMI<24 (kg/m²), 24≤BMI<28 (kg/m²) and BMI≥28 (kg/m²). There were two groups in male, waist circumference≥90 (cm) and waist circumference<90 (cm). Similarly, there were two groups in female, waist circumference≥85 (cm) and waist circumference<85 (cm).

RESULTS

There were 543 individuals (64.6% male and 35.4% female) aged 40-60 years in this study. The resting blood pressure (BP) and peak BP have the significant differences in different BMI groups (p < 0.001) and male or female groups (p < 0.001). However, the resting DBP (77.70±9.45 vs 81.16±8.80, p < 0.001) and peak DBP (85.67±10.21 vs 89.03±9.94, p = 0.002) have the significant differences in different male waist circumference groups, and the resting BP (SBP 113.76±14.29 vs 121.86±15.54, p = 0.001, DBP 71.95±10.83 vs 77.27±11.42, p = 0.005) has the significant differences in different female waist circumference groups. Carbon dioxide Ventilation equivalent (VE/VCO₂) has the significant differences in different male waist circumference groups (26.84±3.10 vs 27.68±2.93, p = 0.009), but it has not the significant differences in different BMI groups and different female waist circumference groups. The oxygen pulse (VO₂/HR) is slightly higher in female group than male group (0.93±0.15 vs 0.89±0.15, p = 0.001). Breathing reserve has the statistical significance in BMI ≥28 group compared with the BMI <24 group (0.52±0.13 vs 0.46±0.17, ηp²=0.021).

CONCLUSION

We found that the blood pressure and ventilation efficiency of CPX were different between the obesity and normal. This will provide a basis for accurate cardiopulmonary assessment of obesity.

Cardiopulmonary Pathophysiological Aspects in the Context of COVID-19 and Obesity

Obesity is a significant public health concern associated with high morbidity. Obese patients are at risk of severe COVID-19 infection, and obesity is a high-risk factor for admission to the intensive care unit. We aimed to write a narrative review of cardiac and pulmonary pathophysiological aspects of obese patients in the context of COVID-19 infection. Obesity affects lung volume, with a decrease in expiratory reserve volume, which is associated with a decrease in lung and chest wall compliance, an increase in airway resistance, and an increase in work of breathing. Obesity affects cardiac structure and hemodynamics. Obesity is a risk factor for hypertension and cardiovascular disorders. Moreover, obesity is associated with a low-grade inflammatory state, endothelial dysfunction, hyperinsulinemia, and metabolic disorders. Obesity is associated with severe COVID-19 and invasive mechanical ventilation. These previous cardiopulmonary pathological aspects may explain the clinical severity in obese patients with COVID-19. Obese patients are at risk of severe COVID-19 infection. Understanding cardiorespiratory pathophysiological aspects may help physicians manage patients in hospitals.

Nonlinear relationship between visceral adiposity index and lung function: a population-based study

Background

As one of the critical indicators of obesity, the interaction between visceral fat content and lung disease is the focus of current research. However, the exact relationship between Visceral adipose index (VAI) and lung function is not fully understood. The purpose of this study was to evaluate the relationship between VAI and lung function,

Methods

Our study included all participants from the baseline survey population in Xinjiang in the Natural Population Cohort Study in Northwest China. A field survey was conducted in rural areas of Moyu County, Xinjiang, China, between 35 and 74 years old from June to December 2018. We collected standard questionnaires and completed physical examinations, visceral fat tests, and lung function measurements.

Results

The study included 2367 participants with a mean VAI of 10.35 ± 4.35, with males having a significantly higher VAI than females: 13.17 ± 3.91 vs. 7.58 ± 2.65. The piecewise linear spline models indicated a significant threshold effect between lung function and VAI in the general population and the males population, showing an inverted U-shaped curve. But there was no significant association between VAI and lung function in females. FEV1% predicted and FVC% predicted increased with the increase of VAI (β 0.76; 95% CI 0.30, 1.21) and (β 0.50; 95% CI 0.06, 0.94) in males with VAI ≤ 14, while FEV1% predicted and FVC% predicted decreased with the increase of VAI (β − 1.17; 95% CI − 1.90, − 0.45) and (β − 1.36; 95% CI − 2.08, − 0.64) in males with VAI ≥ 15.

Conclusions

The relationship between lung function and VAI in male participants showed an inverted U-shaped curve, with the turning point of VAI between 14 and 15. The association between visceral fat and lung function was more robust in males than in females.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01751-7.

Ventilatory Response at Rest and During Maximal Exercise Testing in Patients with Severe Obesity Before and After Sleeve Gastrectomy

INTRODUCTION

Sleeve gastrectomy (SG) has become a widespread treatment option in patients affected by severe obesity. However, studies investigating the impact of the subsequent weight loss on the ventilatory response at rest and during physical exercise are lacking.

METHODS

This is an observational study on 46 patients with severe obesity (76% females), comparing parameters of ventilatory function 1 month before and 6 months after SG. Patients were first evaluated by resting spirometry and subsequently with an incremental, maximal cardiopulmonary exercise test (CPET) on treadmill.

RESULTS

The important weight loss of 26.35 ± 6.17% of body weight (BMI from 43.59 ± 5.30 to 32.27 ± 4.84 kg/m2) after SG was associated with a significant improvement in lung volumes and flows during forced expiration at rest, while resting ventilation and tidal volume were reduced (all p ≤ 0.001). CPET revealed decreased ventilation during incremental exercise (p < 0.001), with a less shallow ventilatory pattern shown by a lower increase of breathing frequency (∆BFrest to AT p = 0.028) and a larger response of tidal volume (∆TVAT to Peak p < 0.001). Furthermore, a concomitant improvement of the calculated dead space ventilation, VE/VCO2 slope and peripheral oxygen saturation was shown (all p ≤ 0.002). Additionally, the increased breathing reserve at peak exercise was associated with a lower absolute oxygen consumption but improved exercise capacity and tolerance (all p < 0.001).

CONCLUSION

The weight loss induced by SG led to less burdensome restrictive limitations of the respiratory system and to a reduction of ventilation at rest and during exercise, possibly explained by an increased ventilatory efficiency and a decrease in oxygen demands.

The Influence of Obesity on Treatment and Outcome of Severely Burned Patients

Obesity and the related medical, social, and economic impacts are relevant multifactorial and chronic conditions that also have a meaningful impact on outcomes following a severe injury, including burns. In addition to burn-specific difficulties, such as adequate hypermetabolic response, fluid resuscitation, and early wound coverage, obese patients also present with common comorbidities, such as arterial hypertension, diabetes mellitus, or nonalcoholic fatty liver disease. In addition, the pathophysiologic response to severe burns can be enhanced. Besides the increased morbidity and mortality compared to burn patients with normal weight, obese patients present a challenge in fluid resuscitation, perioperative management, and difficulties in wound healing. The present work is an in-depth review of the current understanding of the influence of obesity on the management and outcome of severe burns.

Correlação da força muscular respiratória com medidas antropométricas e nível de atividade física em adultos da atenção primária

RESUMO O objetivo deste estudo foi correlacionar a força muscular respiratória com as medidas antropométricas e o nível de atividade física de indivíduos adultos da atenção primária. Trata-se de um estudo transversal, realizado em uma unidade básica de saúde, onde foram incluídos indivíduos de ambos os sexos e com idade superior a 18 anos. A força muscular respiratória foi analisada pela pressão inspiratória máxima (PImáx) e pressão expiratória máxima (PEmáx), por meio do manovacuômetro, onde valores pressóricos acima de 80% em relação ao predito foram considerados normais. Utilizou-se balança mecânica, estadiômetro e fita métrica para mensuração das principais medidas antropométricas: índice de massa corporal (IMC), circunferência de pescoço (CP), circunferência abdominal (CA), circunferência de quadril (CQ), relação cintura-quadril (RCQ) e o índice de adiposidade corporal (IAC). O nível de atividade física foi determinado pelo questionário internacional de atividade física (IPAQ), onde os indivíduos foram categorizados como sedentário, irregularmente ativo A, irregularmente ativo B, ativo ou muito ativo, sendo realizada também a estimativa dos equivalentes metabólicos (MET) alcançados. Foram avaliados 110 indivíduos adultos (78,1% do sexo feminino; 51,9±12,3 anos), e com porcentagem em relação ao predito (%) de PImáx de 96,3±32,4% e 98,9±27,3% de PEmáx. A %PImáx apresentou fraca correlação com o IAC (r=0,23; p=0,01) e com a CQ (r=0,20; p=0,03), e a %PEmáx com o IMC (r=0,26; p<0,01) e IAC (r=0,30; p<0,01). Não houve diferença dos valores médios de %PImáx (p=0,61) e %PEmáx (p=0,54) entre as categorias do IPAQ, além de não existirem correlações (p>0,05) com os MET estimados. Em adultos da atenção primária, a força muscular respiratória apresentou fraca correlação com IMC, CQ e IAC, porém sem correlação com o nível de atividade física.

Respiratory Muscle Strengths and Their Association with Lean Mass and Handgrip Strengths in Older Institutionalized Individuals

The study of reduced respiratory muscle strengths in relation to the loss of muscular function associated with ageing is of great interest in the study of sarcopenia in older institutionalized individuals. The present study assesses the association between respiratory muscle parameters and skeletal mass content and strength, and analyzes associations with blood cell counts and biochemical parameters related to protein, lipid, glucose and ion profiles. A multicenter cross-sectional study was performed among patients institutionalized in nursing homes. The respiratory muscle function was evaluated by peak expiratory flow, maximal respiratory pressures and spirometry parameters, and skeletal mass function and lean mass content with handgrip strength, walking speed and bioimpedance, respectively. The prevalence of reduced respiratory muscle strength in the sample ranged from 37.9% to 80.7%. Peak expiratory flow significantly (p < 0.05) correlated to handgrip strength and gait speed, as well as maximal inspiratory pressure (p < 0.01). Maximal expiratory pressure significantly (p < 0.01) correlated to handgrip strength. No correlation was obtained with muscle mass in any of parameters related to reduced respiratory muscle strength. The most significant associations within the blood biochemical parameters were observed for some protein and lipid biomarkers e.g., glutamate-oxaloacetate transaminase (GOT), urea, triglycerides and cholesterol. Respiratory function muscle parameters, peak expiratory flow and maximal respiratory pressures were correlated with reduced strength and functional impairment but not with lean mass content. We identified for the first time a relationship between peak expiratory flow (PEF) values and GOT and urea concentrations in blood which deserves future investigations in order to manage these parameters as a possible biomarkers of reduced respiratory muscle strength.

Sudden death after oxygen toxicity seizure during hyperbaric oxygen treatment: Case report

Acute cerebral oxygen toxicity (ACOT) is a known side effect of hyperbaric oxygen treatment (HBOT), which can cause generalised seizures. Fortunately, it has a low incidence and is rarely harmful. Nevertheless, we present a case of a 37 year-old patient with morbid obesity who died unexpectedly after an oxygen toxicity seizure in the hyperbaric chamber. Considering possible causes, physiologic changes in obesity and obesity hypoventilation syndrome may increase the risk of ACOT. Obesity, especially in extreme cases, may hinder emergency procedures, both in- and outside of a hyperbaric chamber. Physicians in the hyperbaric field should be aware of the possibility of a fatal outcome after ACOT through the described mechanisms and take appropriate preventative measures. Basic airway management skills are strongly advised for involved physicians, especially when specialised personnel and equipment are not immediately available.

Obesity Surgery and Anesthesiology Risks: a Review of Key Concepts and Related Physiology

The obesity epidemic is swelling to epic proportions. Obese patients often suffer from a combination of hypertension, dyslipidemia, and type 2 diabetes mellitus (T2DM), also known as the "metabolic syndrome." The metabolic syndrome is an independent predictor of cardiac dysfunction and cardiovascular disease and a risk factor for perioperative morbidity and mortality. In this paper, we discuss the perioperative risk factors and the need for advanced care of obese patients needing general anesthesia for (bariatric) surgical procedures based on physiological principles.

Obesity and childhood asthma

PURPOSE OF REVIEW

Asthma is a common chronic disease of the airways characterized by recurrent respiratory symptoms, bronchoreactivity, and airway inflammation. The high toll on quality of life has led to sustained efforts to understand the factors leading to asthma inception and poor disease control. Obesity is another increasingly common pediatric disease, which appears to increase the risk for incident asthma and worsened disease severity. Currently, our understanding of how obesity affects asthma risk and affects its phenotypic characteristics remains incomplete. The current review describes our current understanding of the epidemiology, clinical characteristics, and management considerations of obesity-related asthma in children.

RECENT FINDINGS

The epidemiologic relationship between obesity in children and incident asthma remains confusing despite numerous longitudinal cohort studies, and appears to be influenced by early life exposures, patterns of somatic growth and underlying familial risks of allergic disease. Children with comorbid obesity and asthma demonstrate diverse phenotypic characteristics which are still becoming clear.

SUMMARY

Like any child with asthma, a child with comorbid obesity requires an individualized approach adhering to current best-practice guidelines and an understanding of how obesity and asthma may interact.

Total and Compartmental Chest Wall Volumes, Lung Function, and Respiratory Muscle Strength in Individuals with Abdominal Obesity: Effects of Body Positions

Background

Abdominal obesity is a chronic condition that can contribute to impairments in lung function, leading to increased risks for respiratory-related diseases. Body position is an important technique that effectively restores and increases lung function and chest wall volumes. The objective of the current study was to examine the effects of the body positions on total and compartmental chest wall volumes, lung function, and respiratory muscle strength in individuals with and without abdominal obesity.

Methods

Twenty obesity and twenty healthy males performed in four body position including sitting without and with back support, Fowler's, and supine positions. Each position was performed for five minutes. Chest wall volumes, lung function, and respiratory muscle strength were assessed in each position.

Results

Sitting without and with back support resulted in higher total and rib cage compartmental chest wall volumes, lung function, and inspiratory muscle strength than Fowler's and supine positions in both groups (p < 0.001). Abdominal obesity subjects had significantly less total and compartmental chest wall volumes and lung function across four body positions than healthy subjects (p < 0.001). Respiratory muscle strength in the obesity group was less than that in the healthy control group (p > 0.05).

Conclusions

This study provides new information regarding the effect of obesity and body position on chest wall volumes, lung function, and respiratory muscle strength. Among obesity individuals who are bedridden, sitting increases lung function, total and rib cage compartmental chest wall volumes, and inspiratory muscle strength-and would therefore likely to decrease the risk of respiratory-related disease-relative to Fowler's and supine positions.

Effect of continuous positive airway pressure on respiratory drive in patients with obstructive sleep apnea

OBJECTIVE

Patients with obstructive sleep apnea (OSA) have an altered control of breathing during wakefulness. Thus far, whether and how treatment with continuous positive airway pressure (CPAP) may restore these abnormalities has been poorly understood. The aim of this study was to investigate the long-term effects of CPAP on the breathing pattern, ventilatory drive (VDr), and chemoreceptor sensitivity in OSA patients.

PATIENTS AND METHODS

This was a prospective, observational study, carried out in an academic sleep outpatient clinic. A total of 62 patients with OSA (mean age [SD], 51 [11] years) underwent polysomnography (PSG), breathing pattern assessment, mouth occlusion pressure, ventilatory response to hypoxemia (V_e/SaO₂), and hypercapnia (V_e/PETCO₂) before and after CPAP titration and during 12-month follow-up. A total of 48 age-matched healthy subjects served as controls. Patients with good (≥6 h/night) and poor (<6 h/night) compliance with CPAP were also compared.

RESULTS

At baseline, VDr as well as thoracic and inspiratory impedances were greater in patients with OSA compared with controls and were reduced by CPAP treatment, starting from the night of titration (P < 0.01), especially in patients with good compliance with CPAP. Baseline V_e/SaO₂ was higher in OSA patients (P < 0.05) and was progressively normalized during CPAP treatment (P < 0.001). The pathophysiological changes were mainly due to a reduction in tidal volume. The remaining breathing pattern parameters were unaltered by CPAP treatment and were similar between groups.

CONCLUSION

In OSA patients, the mechanics of breathing are inefficient because of an imbalance of the VDr. Regular CPAP treatment improves the efficiency of the respiratory system and normalizes the hypoxemic stimulus.

Respiratory mechanics of patients with morbid obesity

OBJECTIVE

To evaluate the different components of the resistance of the respiratory system, respiratory muscle strength and to investigate the occurrence of expiratory flow limitation (EFL) in patients with morbid obesity (MO) when seated.

METHODS

The sample was composed of MO (BMI≥40 kg/m2) and non-obese individuals (NO) with a BMI between 18 and 30 kg/m2. The protocol consisted of the anthropometric assessment and the following measures of respiratory function: spirometry, maximal inspiratory and expiratory pressures (MIP and MEP, respectively) and impulse oscillometry. The group comparison was performed using T-test for unpaired samples. The correlations were evaluated by the Pearson test with a significance level of 5%.

RESULTS

Fifty MO (age 40±10.4 years, 1.64±0.09 m, 138.8±33.6 kg and 50.7±8.9 kg/m2), and 30 NO (age 37.6±11.5 years, 1.67±0.09 m, 65.2±10.3 kg and 23.2±22 kg/m2) were evaluated. The MO showed higher values of total, peripheral, airways, tissue and central resistance when compared to the NO. No patient showed EFL. The waist circumference was associated with spirometric variables, MIP, and MEP. The waist-to-hip ratio was correlated to respiratory mechanics and spirometric variables, MIP, and MEP.

CONCLUSION

Morbidly obese patients with no obstructive spirometric pattern show increased total, airway, peripheral, and tissue respiratory system resistance when compared to nonobese. These individuals, however, do not present with expiratory flow limitation and reduced respiratory muscles strength.

Associations between sleep conditions and body composition states: results of the EPISONO study

BACKGROUND

Evidence suggests anthropometric indicators of obesity are associated with changes in sleep quality and quantity, and the presence of obstructive sleep apnoea (OSA). Investigations including diverse and objective evaluations of sleep and body composition are scarce. We aimed to evaluate the associations between indicators of sleep impairment and body composition states in a sample from a population-based study.

METHODS

Participants of the first follow-up of the EPISONO (São Paulo, Brazil) >50 years were cross-sectionally evaluated. Sleep was assessed through questionnaires, actigraphy, and polysomnography. Body composition was evaluated by bioelectrical impedance analysis. Appendicular skeletal muscle mass adjusted for body mass index defined sarcopenia (men <0.789 and women <0.512). Total body fat defined obesity (men >30% and women >40%). The overlap between both conditions defined sarcopenic obesity (SO). Final results were obtained by multinomial logistic regression analysis.

RESULTS

Three hundred fifty-nine adults [mean (standard deviation) age, 61 (8.8) years; 212 (59.1%) female] were enrolled. Obesity was detected in 22.6% of the sample, sarcopenia in 5.6%, and SO in 16.2%. After controlling for covariates, OSA was associated with SO [odds ratio = 3.14, 95% confidence interval (CI) = 1.49-6.61]. Additionally, nocturnal hypoxaemia was associated with both obesity (adjusted odds ratio = 2.59, 95% CI = 1.49-4.49) and SO (odds ratio = 2.92, 95% CI = 1.39-6.13). Other indicators of poor sleep/sleep disorders were not associated with body composition states.

CONCLUSIONS

Sarcopenic obesity but not obesity alone was associated with OSA. Both obesity and SO but not sarcopenia were associated with nocturnal hypoxaemia. The findings suggest a complex pathophysiologic relationship between adverse body composition states and OSA. Upcoming research on risk factors and therapeutic interventions for OSA should target synchronically the lean and adipose body tissues.

Modelling the effects of age and sex on the resistive and viscoelastic components of the work of breathing during exercise

NEW FINDINGS

What is the central question of this study? What is the effect of age and sex on the resistive and viscoelastic components of work of breathing (W_b ) during exercise? What is the main finding and its importance? The resistive and viscoelastic components of W_b were higher in older adults, regardless of sex. The resistive, but not viscoelastic, component of W_b was higher in females than in males, regardless of age. These findings contribute to improving our understanding of the effects of ageing and sex on the mechanical ventilatory response to exercise.

ABSTRACT

Healthy ageing and biological sex each affect the work of breathing (W_b ) for a given minute ventilation ( V ̇ E ). Age-related structural changes to the respiratory system lead to an increase in both the resistive and viscoelastic components of W_b ; however, it is unclear whether healthy ageing differentially alters the mechanics of breathing in males and females. We analysed data from 22 older (60-80 years, n = 12 females) and 22 younger (20-30 years, n = 11 females) males and females that underwent an incremental cycle exercise test to exhaustion. V ̇ E and W_b were assessed at rest and throughout exercise. W_b - V ̇ E data for each participant were fitted to a non-linear equation (i.e. W_b  = a V ̇ E ³ + b V ̇ E ² ) that partitions W_b into resistive (i.e. a V ̇ E ³ ) and viscoelastic (i.e. b V ̇ E ² ) components. We then modelled the effects of healthy ageing and biological sex on each component of W_b . Overall, the model fit was excellent (r² : 0.99 ± 0.01). There was a significant main effect of age and sex on the resistive component of W_b (both P < 0.05), and a significant main effect of age (P < 0.001), but not sex (P = 0.309), on the viscoelastic component of W_b . No significant interactions between age and sex on a V ̇ E ³ or b V ̇ E ² were noted (both P > 0.05). Our findings indicate that during exercise: (i) the higher total W_b in females relative to males is due to a higher resistive, but not viscoelastic, component of W_b , and (ii) regardless of sex, the higher W_b in older adults relative to younger adults is due to higher resistive and viscoelastic components of W_b .

Choosing an Adequate Test to Determine Fitness for Air Travel in Obese Individuals

BACKGROUND

Air travel is physically demanding and, because obesity is rising, physicians increasingly need to assess whether such patients can fly safely. Our aim was to compare the diagnostic accuracy of two routinely used exercise tests, 50-m walk test and 6-min walk test, and hypoxic challenge testing (HCT) in obese individuals. We further explored the diagnostic potential of perceived dyspnea as measured with the Borg scale because this is often recorded subsequent to walking tests.

METHODS

In this prospective study, we examined 21 obese participants (10 women, age 51 ± 15 [mean  ±  SD], BMI 36 ± 5  kg/m²). The most prevalent comorbidity was COPD (n = 11). The reference standard for in-flight hypoxia, defined as oxygen saturation below 90%, was established in an altitude chamber. Diagnostic accuracy of each index test was estimated by area under the receiver operating characteristic curve (AUC).

RESULTS

Of the 21 participants, 13 (9 with COPD) were identified with in-flight hypoxia. HCT was the only test separating the reference groups significantly with AUC 0.87 (95% CI,  0.62-0.96). Neither of the walking tests predicted noticeably above chance level: 50 m walk test had an AUC of 0.63 (0.36-0.84) and 6MWT had an AUC of 0.64 (0.35-0.86). We further observed good prognostic ability of subjective dyspnea assessment when recorded after 6MWT with an AUC of 0.80 (0.55-0.93).

CONCLUSIONS

In-flight hypoxia in obese individuals can be predicted by HCT but not by simple walking tests.

More than Heart Failure: Central Sleep Apnea and Sleep-Related Hypoventilation

Central sleep apnea (CSA) comprises a variety of breathing patterns and clinical entities. They can be classified into 2 categories based on the partial pressure of carbon dioxide in the arterial blood. Nonhypercapnic CSA is usually characterized by a periodic breathing pattern, while hypercapnic CSA is based on hypoventilation. The latter CSA form is associated with central nervous, neuromuscular, and rib cage disorders as well as obesity and certain medication or substance intake. In contrast, nonhypercapnic CSA is typically accompanied by an overshoot of the ventilation and often associated with heart failure, cerebrovascular diseases, and stay in high altitude. CSA and hypoventilation syndromes are often considered separately, but pathophysiological aspects frequently overlap. An integrative approach helps to recognize underlying pathophysiological mechanisms and to choose adequate therapeutic strategies. Research in the last decades improved our insights; nevertheless, diagnostic tools are not always appropriately chosen to perform comprehensive sleep studies. This supports misinterpretation and misclassification of sleep disordered breathing. The purpose of this article is to highlight unresolved problems, raise awareness for different pathophysiological components and to discuss the evidence for targeted therapeutic strategies.

Obesity and sarcoidosis: consequence or contributor?

PURPOSE OF REVIEW

Sarcoidosis is a multisystem disease of unknown cause. Obesity can affect many physiological factors. The relationship between obesity and sarcoidosis is unclear, and can been described as posing a 'chicken and egg' scenario for the patient as it is not always clear whether it is a consequence of, or a risk factor for any disease. The purpose of this review is to examine the dual roles of obesity on sarcoidosis morbidity and the incidence.

RECENT FINDINGS

Obesity magnifies the symptoms of sarcoidosis and corticosteroid therapy increases BMI. Prospective epidemiologic studies started to explore the role of obesity as a potential risk factor for sarcoidosis. Three studies in the United States, and one study in Denmark, have demonstrated significantly increased risks of sarcoidosis among obese compared with nonobese patients; risk estimates ranged from 1.42 [95% confidence interval (CI), 1.07-1.89] to 3.59 (95% CI, 2.31-5.57).

SUMMARY

Obesity can be both a consequence of sarcoidosis treatment, and a contributor to disease risk likely through the pro-inflammatory environment of obesity. Prospective epidemiologic cohort studies are needed to explore the cause of sarcoidosis and insight into possible avenues of treatment development and prevention.

Weight loss reduces dyspnea on exertion and unpleasantness of dyspnea in obese men

We hypothesized that weight loss would ameliorate dyspnea on exertion (DOE) and feelings of unpleasantness related to the DOE in obese men. Eighteen men (34 ± 7yr, 35 ± 4 kg/m2 BMI, mean ± SD) participated in a 12-week weight loss program. Body composition, pulmonary function, cardiorespiratory measures, DOE, and unpleasantness (visual analog scale) were assessed before and after weight loss. Subjects were grouped by Ratings of Perceived Breathlessness (RPB, Borg 0-10 scale) during submaximal cycling: Ten men rated RPB ≥ 4 (+DOE), eight rated RPB ≤ 2 (-DOE). Subjects lost 10.3 ± 5.6 kg (9.2 ± 4.5%) of body weight (n = 18). RPB during submaximal cycling was significantly improved in both groups (+DOE: 4.1 ± 0.3-2.8 ± 1.1; -DOE: 1.3 ± 0.7 to 0.8 ± 0.6, p < 0.001). Several submaximal exercise variables (e.g., V˙O2, V˙E) were decreased similarly in both groups (p < 0.01). Unpleasantness associated with the DOE was reduced (p < 0.05). The improved RPB was not significantly correlated with changes in body weight or cardiopulmonary exercise responses (p > 0.05). Moderate weight loss appears to be an effective option to ameliorate DOE and unpleasantness related to DOE in obese men.

Fibro-Adipogenic Remodeling of the Diaphragm in Obesity-Associated Respiratory Dysfunction

Respiratory dysfunction is a common complication of obesity, conferring cardiovascular morbidity and increased mortality and often necessitating mechanical ventilatory support. While impaired lung expansion in the setting of increased adipose mass and reduced central response to hypercapnia have been implicated as pathophysiological drivers, the impact of obesity on respiratory muscles-in particular, the diaphragm-has not been investigated in detail. Here, we demonstrate that chronic high-fat diet (HFD) feeding impairs diaphragm muscle function, as assessed in vivo by ultrasonography and ex vivo by measurement of contractile force. During an HFD time course, progressive adipose tissue expansion and collagen deposition within the diaphragm parallel contractile deficits. Moreover, intradiaphragmatic fibro-adipogenic progenitors (FAPs) proliferate with long-term HFD feeding while giving rise to adipocytes and type I collagen-depositing fibroblasts. Thrombospondin 1 (THBS1), a circulating adipokine, increases with obesity and induces FAP proliferation. These findings suggest a novel role for FAP-mediated fibro-adipogenic diaphragm remodeling in obesity-associated respiratory dysfunction.

Examining Joint Effects of Air Pollution Exposure and Social Determinants of Health in Defining "At-Risk" Populations Under the Clean Air Act: Susceptibility of Pregnant Women to Hypertensive Disorders of Pregnancy

Pregnant women are uniquely susceptible to adverse effects of air pollution exposure due to vulnerabilities and health consequences during pregnancy (e.g., hypertensive disorders of pregnancy [HDP]) compared to the general population. Because the Clean Air Act (CAA) creates a duty to protect at-risk groups, the regulatory assessment of at-risk populations has both policy and scientific foundations. Previously, pregnant women have not been specially protected in establishing the margin of safety for the ozone and particulate matter (PM) standards. Due to physiological changes, pregnant women can be at greater risk of adverse effects of air pollution and should be considered an at-risk population. Women with preexisting conditions, women experiencing poverty, and groups that suffer systematic discrimination may be particularly susceptible to cardiac effects of air pollutants during pregnancy. We rigorously reviewed 11 studies of over 1.3 million pregnant women in the United States to characterize the relationship between ozone or PM exposure and HDP. Findings were generally mixed, with a few studies reporting a joint association between ozone or PM and social determinants or pre-existing chronic health conditions related to HDP. Adequate evidence associates exposure to PM with an adverse effect of HDP among pregnant women not evident among non-gravid populations.

Respiratory muscle endurance training reduces the O2 cost of cycling and perceived exertion in obese adolescents

In obesity, the increased O2 cost of breathing negatively affects the O2 cost of exercise and exercise tolerance. The purpose of the study was to determine whether, in obese adolescents, the addition of respiratory muscle endurance training (RMET) (isocapnic hyperpnea) to a standard body mass reduction program decreases the O2 cost of exercise and perceived exertion. Nine male obese adolescents [16.0 ± 1.4 yr ( x ± SD), body mass 114.4 ± 22.3 kg] underwent 3 wk of RMET (5 days/week) in addition to a standard body mass reduction program. Eight age- and sex-matched obese adolescents underwent only the standard program (CTRL). Before and after interventions, patients performed on a cycle ergometer: incremental exercise; 12-min exercises at a constant work rate (CWR) of 65% and 120% at the gas exchange threshold (GET) determined before the intervention. Breath-by-breath pulmonary ventilation (V̇e) and O2 uptake (V̇o2), heart rate (HR), and ratings of perceived exertion for dyspnea/respiratory discomfort (RPER) and leg effort (RPEL) were determined. Body mass decreased (by ~3.0 kg) after both RMET ( P = 0.003) and CTRL ( P = 0.002). Peak V̇o2 was not affected by both interventions. Peak work rate was slightly, but significantly ( P = 0.04), greater after RMET but not after CTRL. During CWR < GET, no changes were observed after both interventions. During CWR > GET, the O2 cost of cycling at the end of exercise ( P = 0.02), the slope of V̇o2 vs. time (3–12 min) ( P = 0.01), RPER ( P = 0.01), and RPEL ( P = 0.01) decreased following RMET, but not following CTRL. HR decreased after both RMET ( P = 0.02) and CTRL ( P = 0.03), whereas V̇e did not change. In obese adolescents RMET, superimposed on a standard body mass reduction program, lowered the O2 cost of cycling and perceived exertion during constant heavy-intensity exercise.

Ozone Exposure, Cardiopulmonary Health, and Obesity: A Substantive Review

From 1999-2014, obesity prevalence increased among adults and youth. Obese individuals may be uniquely susceptible to the proinflammatory effects of ozone because obese humans and animals have been shown to experience a greater decline in lung function than normal-weight subjects. Obesity is independently associated with limitations in lung mechanics with increased ozone dose. However, few epidemiologic studies have examined the interaction between excess weight and ozone exposure among adults. Using PubMed keyword searches and reference lists, we reviewed epidemiologic evidence to identify potential response-modifying factors and determine if obese or overweight adults are at increased risk of ozone-related health effects. We initially identified 170 studies, of which seven studies met the criteria of examining the interaction of excess weight and ozone exposure on cardiopulmonary outcomes in adults, including four short-term ozone exposure studies in controlled laboratory settings and three community epidemiologic studies. In the studies identified, obesity was associated with decreased lung function and increased inflammatory mediators. Results were inconclusive about the effect modification when data were stratified by sex. Obese and overweight populations should be considered as candidate at-risk groups for epidemiologic studies of cardiopulmonary health related to air pollution exposures. Air pollution is a modifiable risk factor that may decrease lung function among obese individuals with implications for environmental and occupational health policy.

Diaphragmatic function is enhanced in fatty and diabetic fatty rats

Background

Obesity is associated with a decrease in mortality in the intensive care unit (ICU) (the "obesity paradox"). We hypothesized that obesity may paradoxically improve diaphragmatic function.

Methods

Diaphragm contractility was prospectively recorded in vitro in adult male Zucker lean (control), fatty, and diabetic fatty rats, at rest, after 12h mechanical ventilation and after fatigue. We analyzed diaphragm morphology, cytokines, and protein expression of the protein kinase signaling pathways.

Results

Diaphragm active-force (AF) was higher in fatty (96±7mN.mm^-2,P = 0.02) but not in diabetic fatty rats (90±17mN.mm^-2) when compared with controls (84±8mN.mm^-2). Recovery from fatigue was improved in fatty and diabetic fatty groups compared with controls. Ventilator-induced diaphragmatic dysfunction was observed in each group, but AF remained higher in fatty (82±8mN.mm^-2,P = 0.03) compared with controls (70±8mN.mm^-2). There was neutral lipid droplet accumulation in fatty and diabetic fatty. There were shifts towards a higher cross-sectional-area (CSA) of myosin heavy chain isoforms (MyHC)-2A fibers in fatty and diabetic fatty compared with control rats (P = 0.002 and P<0.001, respectively) and a smaller CSA of MyHC-2X in fatty compared with diabetic fatty and control rats (P<0.001 and P<0.001, respectively). The phosphorylated total-protein-kinase-B (pAKT)/AKT ratio was higher in fatty (182±58%,P = 0.03), but not in diabetic fatty when compared with controls and monocarboxylate-transporter-1 was higher in diabetic fatty (147±36%,P = 0.04), but not in fatty.

Conclusions

Diaphragmatic force is increased in Zucker obese rats before and after mechanical ventilation, and is associated with activation of AKT pathway signaling and complex changes in morphology.

The physiological basis and clinical significance of lung volume measurements

From a physiological standpoint, the lung volumes are either dynamic or static. Both subclasses are measured at different degrees of inspiration or expiration; however, dynamic lung volumes are characteristically dependent on the rate of air flow. The static lung volumes/capacities are further subdivided into four standard volumes (tidal, inspiratory reserve, expiratory reserve, and residual volumes) and four standard capacities (inspiratory, functional residual, vital and total lung capacities). The dynamic lung volumes are mostly derived from vital capacity. While dynamic lung volumes are essential for diagnosis and follow up of obstructive lung diseases, static lung volumes are equally important for evaluation of obstructive as well as restrictive ventilatory defects. This review intends to update the reader with the physiological basis, clinical significance and interpretative approaches of the standard static lung volumes and capacities.