Pulmonary function in obese subjects with a normal FEV1/FVC ratio

Static respiratory mechanics are unaltered in males and females with obesity

We tested the hypothesis that independent of the obesity-related shift in lung volume subdivisions, obesity would not reduce the interrelationships of expiratory flow, lung volume, and static lung elastic recoil pressure in males and females. Simultaneous measurements of expiratory flow, volume, and transpulmonary pressure were continuously recorded while flow-volume loops of varying expiratory efforts were performed in a pressure-corrected, volume-displacement body plethysmograph in males and females with obesity. Static compliance curves were collected using the occlusion technique. Flow-volume, static pressure-volume, and static pressure-flow relationships were examined. Isovolume pressure-flow curves were constructed for the determination of the critical pressure for maximal flow. Data were compared with that collected in lean males and females. Individuals with obesity displayed a notable decrease in functional residual capacity. The interrelationships of flow, lung volume, static elastic recoil pressure, and the minimum pressure required for maximal expiratory flow in males and females with obesity were not different from that in lean males and females (all P > 0.05). Obesity does not alter the interrelationships of flow-volume-pressure of the lung in adult males and females (all P > 0.05). We further explored potential sex differences in static mechanics independent of obesity and observed that females have lower maximal expiratory flow due to a combination of smaller lungs and greater upstream flow resistance compared with males (all P ≤ 0.05).NEW & NOTEWORTHY The potential influence of obesity on the interrelationships between maximal expiratory flow, lung volume, and static lung elastic recoil pressure is unclear. These data show that the presence of obesity does not alter the relationship of flow and pressure across the mid-expiratory range in males and females. In addition, independent of obesity, females have smaller lungs and greater upstream flow resistance, which contributes to reduced maximal flow, when compared with males.

Adaptively Integrative Association between Multivariate Phenotypes and Transcriptomic Data for Complex Diseases

Phenotype–gene association studies can uncover disease mechanisms for translational research. Association with multiple phenotypes or clinical variables in complex diseases has the advantage of increasing statistical power and offering a holistic view. Existing multi-variate association methods mostly focus on SNP-based genetic associations. In this paper, we extend and evaluate two adaptive Fisher’s methods, namely AFp and AFz, from the p-value combination perspective for phenotype–mRNA association analysis. The proposed method effectively aggregates heterogeneous phenotype–gene effects, allows association with different data types of phenotypes, and performs the selection of the associated phenotypes. Variability indices of the phenotype–gene effect selection are calculated by bootstrap analysis, and the resulting co-membership matrix identifies gene modules clustered by phenotype–gene effect. Extensive simulations demonstrate the superior performance of AFp compared to existing methods in terms of type I error control, statistical power and biological interpretation. Finally, the method is separately applied to three sets of transcriptomic and clinical datasets from lung disease, breast cancer, and brain aging and generates intriguing biological findings.

Respiratory complications of obesity: from early changes to respiratory failure

Obesity is a significant and increasingly common cause of respiratory compromise. It causes a decrease in static and dynamic pulmonary volumes. The expiratory reserve volume is one of the first to be affected. Obesity is associated with reduced airflow, increased airway hyperresponsiveness, and an increased risk of developing pulmonary hypertension, pulmonary embolism, respiratory tract infections, obstructive sleep apnoea and obesity hypoventilation syndrome. The physiological changes caused by obesity will eventually lead to hypoxic or hypercapnic respiratory failure. The pathophysiology of these changes includes a physical load of adipose tissue on the respiratory system and a systemic inflammatory state. Weight loss has clear, well-defined benefits in improving respiratory and airway physiology in obese individuals.

The Impact of Obesity on Critical Illnesses

ABSTRACT

In the last few decades, obesity became one of the world's greatest health challenges reaching a size of global epidemic in virtually all socioeconomic statuses and all age groups. Obesity is a risk factor for many health problems and as its prevalence gradually increases is becoming a significant economic and health burden. In this manuscript we describe how normal respiratory and cardiovascular physiology is altered by obesity. We review past and current literature to describe how obesity affects outcomes of patients facing critical illnesses and discuss some controversies related to this topic.

Obstructive Sleep Apnea and Subclinical Interstitial Lung Disease in the Multi-Ethnic Study of Atherosclerosis (MESA)

RATIONALE

Obstructive sleep apnea (OSA) has been postulated to contribute to idiopathic pulmonary fibrosis by promoting alveolar epithelial injury via tractional forces and intermittent hypoxia.

OBJECTIVES

To determine whether OSA is associated with subclinical interstitial lung disease (ILD) and with biomarkers of alveolar epithelial injury and remodeling.

METHODS

We performed cross-sectional analyses of 1,690 community-dwelling adults who underwent 15-channel in-home polysomnography and thoracic computed tomographic imaging in the Multi-Ethnic Study of Atherosclerosis. We measured the obstructive apnea-hypopnea index (oAHI) by polysomnography and high-attenuation areas (HAAs) and interstitial lung abnormalities (ILAs) by computed tomography. Serum matrix metalloproteinase-7 (MMP-7) and surfactant protein-A (SP-A) were measured by ELISA in 99 participants. We used generalized linear models to adjust for potential confounders.

RESULTS

The mean age was 68 years, and the mean forced vital capacity was 97% predicted. The median oAHI was 8.4 events/h, and 32% had an oAHI greater than 15. After adjusting for demographics, smoking, and center, an oAHI greater than 15 was associated with a 4.0% HAA increment (95% confidence interval [CI], 1.4-6.8%; P = 0.003) and 35% increased odds of ILA (95% CI, 13-61%; P = 0.001). However, there was evidence that these associations varied by body mass index (BMI) (P for interaction = 0.08 and 0.04, respectively). Among those with a BMI less than 25 kg/m², an oAHI greater than 15 was associated with a 6.1% HAA increment (95% CI, 0.5-12%; P = 0.03) and 2.3-fold increased odds of ILA (95% CI, 1.3-4.1; P = 0.005). Among those with a BMI greater than 30 kg/m², an oAHI greater than 15 was associated with 1.8-fold greater odds of ILA (95% CI, 1.1-2.9; P = 0.01) but was not associated with HAA. There were no meaningful associations detected among those with a BMI of 25-30 kg/m². Greater oAHI was associated higher serum SP-A and MMP-7 levels, particularly among those with a BMI less than 25 kg/m².

CONCLUSIONS

Moderate to severe OSA is associated with subclinical ILD and with evidence of alveolar epithelial injury and extracellular matrix remodeling in community-dwelling adults, an association that is strongest among normal-weight individuals. These findings support the hypothesis that OSA might contribute to early ILD.

The "Complex Restrictive" Pulmonary Function Pattern: Clinical and Radiologic Analysis of a Common but Previously Undescribed Restrictive Pattern

BACKGROUND

Most patients with restriction have a pulmonary function test (PFT) pattern in which total lung capacity (TLC), FVC, and FEV₁ are reduced to a similar degree. This pattern is called "simple restriction" (SR). In contrast, we commonly observe a pattern in which FVC percent predicted (_pp) is disproportionately reduced relative to TLC_pp. This pattern is termed "complex restriction" (CR), and we attempted to characterize its clinical, radiologic, and physiologic features.

METHODS

This study reviewed PFT results of patients tested between November 2009 and June 2013 who had restriction (TLC less than the lower limit of normal). SR was defined as TLC_pp-FVC_pp ≤ 10%, and CR was stratified into four classes based on TLC_pp-FVC_pp discrepancy: Class 1 CR, TLC_pp-FVC_pp > 10% and ≤ 15%; Class 2 CR, TLC_pp-FVC_pp > 15% and ≤20%; Class 3 CR, TLC_pp-FVC_pp > 20% and ≤ 25%; and Class 4 CR, TLC_pp-FVC_pp > 25%. The medical records of 150 randomly selected patients with SR and 50 patients from each CR class were reviewed.

RESULTS

Of 39,277 PFTs completed, we identified 4,532 patients (11.5%) with restriction: 2,407 (6.1%) with SR, 1,614 (4.1%) with CR, and 511 (1.3%) with a mixed pattern. Patients with CR were younger, were more often women, and had a higher prevalence of neuromuscular disease, BMI > 40 kg/m² or < 18.5 kg/m², diaphragmatic dysfunction, bronchiectasis, CT mosaic attenuation, and pulmonary hypertension (P < .0001, < .0001, < .001, .004, .0008, .002, .008, .009, .053, and .01, respectively) and a lower prevalence of interstitial lung disease (P < .0001).

CONCLUSIONS

CR is a common PFT pattern with distinct clinical features. The associated clinical entities share impaired lung emptying (eg, neuromuscular disease, occult obstruction, chest wall limitation). Clinicians should be aware of this novel PFT pattern and how it shapes the differential diagnosis.

Evaluation of Respiratory Muscle Strength in the Acute Phase of Stroke: The Role of Aging and Anthropometric Variables

BACKGROUND

During hospitalization, stroke patients are bedridden due to neurologic impairment, leading to loss of muscle mass, weakness, and functional limitation. There have been few studies examining respiratory muscle strength (RMS) in the acute phase of stroke.

OBJECTIVE

This study aimed to evaluate the RMS of patients with acute stroke compared with predicted values and to relate this to anthropometric variables, risk factors, and neurologic severity.

METHODS

This is a cross-sectional study in the acute phase of stroke. After admission, RMS was evaluated by maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP); anthropometric data were collected; and neurologic severity was evaluated by the National Institutes of Health Stroke Scale. The analysis of MIP and MEP with predicted values was performed by chi-square test, and the relationship between anthropometric variables, risk factors, and neurologic severity was determined through multiple linear regression followed by residue analysis by the Shapiro-Wilk test; P < .05 was considered statistically significant.

RESULTS

In the 32 patients studied, MIP and MEP were reduced when compared with the predicted values. MIP declined significantly by 4.39 points for each 1 kg/m² increase in body mass index (BMI), and MEP declined significantly by an average of 3.89 points for each 1 kg/m² increase in BMI. There was no statistically significant relationship between MIP or MEP and risk factors, and between MIP or MIP and neurologic severity in acute phase of stroke.

CONCLUSION

There is a reduction of RMS in the acute phase of stroke, and RMS was lower in individuals with increased age and BMI.

The effect of obesity on patients with mild chronic obstructive pulmonary disease: results from KNHANES 2010 to 2012

PURPOSE

A low body mass index has been associated with high mortalities in patients with chronic obstructive pulmonary disease (COPD), and studies reveal that obesity aggravates the clinical effects of COPD. We investigated the impact of obesity on patients newly identified with COPD.

PATIENTS AND METHODS

This population-based, cross-sectional study, used data from the Korea National Health and Nutrition Examination Survey (KNHANES) conducted from 2010 to 2012. Through analyses of data from this survey, we compared concurrent comorbid diseases, symptoms, and lung functions between an obese and nonobese group of patients with COPD.

RESULTS

In total, 618 participants were diagnosed with COPD and the average forced expired volume in 1 s (FEV1) was 79.47%±0.69%. Of the total, 30.5% of the subjects were categorized into an obese group. Subjects in the obese group were likely to have metabolic syndrome (P<0.001), hypertension (P=0.02), and a higher number of comorbidities compared to the nonobese group (2.3±0.1 vs 2.0±0.1, P=0.02). In addition, subjects in the obese group showed a lower forced vital capacity (FVC) than subjects in the nonobese group, even after adjusting for covariates (average FVC%, 89.32±1.26 vs 92.52%±0.72%, P=0.037). There were no significant differences in the adjusted FEV1% and adjusted FEV1/FVC between the groups.

CONCLUSIONS

Among subjects newly identified with mild COPD, participants in the obese group had more comorbid conditions and showed a lower FVC compared with subjects in the nonobese group, even after adjustment of covariates. These findings show that a combination of obesity and COPD may be a severe phenotype; therefore, early attention should be paid to obesity for the management of COPD patients.

Obesity and Pulmonary Function in African Americans

Background

Obesity prevalence in United States (US) adults exceeds 30% with highest prevalence being among blacks. Obesity is known to have significant effects on respiratory function and obese patients commonly report respiratory complaints requiring pulmonary function tests (PFTs). However, there is no large study showing the relationship between body mass index (BMI) and PFTs in healthy African Americans (AA).

Objective

To determine the effect of BMI on PFTs in AA patients who did not have evidence of underlying diseases of the respiratory system.

Methods

We reviewed PFTs of 339 individuals sent for lung function testing who had normal spirometry and lung diffusion capacity for carbon monoxide (DLCO) with wide range of BMI.

Results

Functional residual capacity (FRC) and expiratory reserve volume (ERV) decreased exponentially with increasing BMI, such that morbid obesity resulted in patients breathing near their residual volume (RV). However, the effects on the extremes of lung volumes, at total lung capacity (TLC) and residual volume (RV) were modest. There was a significant linear inverse relationship between BMI and DLCO, but the group means values remained within the normal ranges even for morbidly obese patients.

Conclusions

We showed that BMI has significant effects on lung function in AA adults and the greatest effects were on FRC and ERV, which occurred at BMI values < 30 kg/m2. These physiological effects of weight gain should be considered when interpreting PFTs and their effects on respiratory symptoms even in the absence of disease and may also exaggerate existing lung diseases.

Impact of obstructive sleep apnea on lung volumes and mechanical properties of the respiratory system in overweight and obese individuals

BACKGROUND

Even through narrowing of the upper-airway plays an important role in the generation of obstructive sleep apnea (OSA), the peripheral airways is implicated in pre-obese and obese OSA patients, as a result of decreased lung volume and increased lung elastic recoil pressure, which, in turn, may aggravate upper-airway collapsibility.

METHODS

A total of 263 male (n = 193) and female (n = 70) subjects who were obese to various degrees without a history of lung diseases and an expiratory flow limitation, but troubled with snoring or suspicion of OSA were included in this cross-sectional study. According to nocturnal-polysomnography the subjects were distributed into OSA and non-OSA groups, and were further sub-grouped by gender because of differences between males and females, in term of, lung volume size, airway resistance, and the prevalence of OSA among genders. Lung volume and respiratory mechanical properties at different-frequencies were evaluated by plethysmograph and an impulse oscillation system, respectively.

RESULTS

Functional residual capacity (FRC) and expiratory reserve volume were significantly decreased in the OSA group compared to the non-OSA group among males and females. As weight and BMI in males in the OSA group were greater than in the non-OSA group (90 ± 14.8 kg vs. 82 ± 10.4 kg, p < 0.001; 30.5 ± 4.2 kg/m(2) vs. 28.0 ± 3.0 kg/m(2), p < 0.001), multiple regression analysis was required to adjust for BMI or weight and demonstrated that these lung volumes decreases were independent from BMI and associated with the severity of OSA. This result was further confirmed by the female cohort. Significant increases in total respiratory resistance and decreases in respiratory conductance (Grs) were observed with increasing severity of OSA, as defined by the apnea-hypopnea index (AHI) in both genders. The specific Grs (sGrs) stayed relatively constant between the two groups in woman, and there was only a weak association between AHI and sGrs among man. Multiple-stepwise-regression showed that reactance at 5 Hz was highly correlated with AHI in males and females or hypopnea index in females, independently-highly correlated with peripheral-airway resistance and significantly associated with decreasing FRC.

CONCLUSIONS

Total respiratory resistance and peripheral airway resistance significantly increase, and its inverse Grs decrease, in obese patients with OSA in comparison with those without OSA, and are independently associated with OSA severity. These results might be attributed to the abnormally increased lung elasticity recoil pressure on exhalation, due to increase in lung elasticity and decreased lung volume in obese OSA.

Longitudinal pulmonary functional loss in cotton textile workers: a 5-year follow-up study

BACKGROUND

Occupational exposure to cotton dust causes several diseases affecting the lungs, but only limited information is available on effects of long-term exposure. In this study, we aimed to evaluate longitudinal changes in selected parameters of pulmonary function in textile workers.

MATERIAL AND METHODS

This prospective cohort study began with 196 textile workers in 2006 and was completed in 2011 with 49 workers. We used standardized tests for pulmonary function on participants on the first day of the workweek in June of 2006 and 2011. Environmental samples of cotton dust were gathered with a vertical elutriator. Loss of pulmonary function was assessed based on gender and smoking status.

RESULTS

The mean number of years participants worked in the textile factory was 7.61 ± 1.83 years, and the mean age was 35.3+5.8 years. The annual FEV1 loss of all workers was 53.2 ml, giving a ratio of annual FEV1 loss to baseline FEV1 of 1.4%. Pulmonary function parameters of all participants in 2011 were significantly lower than those in 2006 (for all, p<0.05). In both surveys, pulmonary function in current smokers was lower, but this difference was not significant (p>0.05).

CONCLUSIONS

This study provides the first data on pulmonary functional loss in Turkish textile workers and supports the findings of other cohort studies that workers with long-term exposure to cotton dust may lose some pulmonary function. The ratio of annual FEV1 loss to baseline FEV1 appears to be a more accurate and comparable method than annual FEV1 loss for evaluating pulmonary functional loss.

Environmental perturbations: Obesity

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

ProSeal™ LMA increases safe apnea period in morbidly obese patients undergoing surgery under general anesthesia

BACKGROUND

Morbidly obese patients are at risk of hypoxemia at the time of induction of anesthesia. The aim of this study was to assess the possible increase in the safe apnea time with the use of ProSeal laryngeal mask airway (PLMA) as a conduit prior to laryngoscope-guided intubation in morbidly obese patients undergoing surgery under general anesthesia.

METHODS

Hundred patients with BMI greater than 35 kg/m2, undergoing surgery under general anesthesia, were randomly divided to receive either PLMA or facemask with oropharyngeal airway (FM) as the airway device. Following preoxygenation with 100% oxygen with continuous positive airway pressure of 10 cm H2O, in ramp position for 5 min the patients were made apneic. From start of apnea to the time to reach SpO2 to 92% was recorded as safe apnea time. Ventilation was initiated and time to reach SpO2 of 100% was recorded as recovery time.

RESULTS

The mean safe apnea time was 205 (96-320)s in FM vs. 337 (176-456) s in PLMA (P = 0.0000). The mean recovery period was 49 (36-68)s in FM vs. 42(30-56)s in PLMA groups (P = 0.0000). Arterial blood gas analysis showed significant difference in pO2 between the two groups.

CONCLUSION

The use of ProSeal laryngeal mask airway prior to laryngoscope-guided intubation is beneficial in increasing safe apnea period and achieving faster recovery from hypoxemia in morbidly obese patients.

ProSeal laryngeal mask airway improves oxygenation when used as a conduit prior to laryngoscope guided intubation in bariatric patients

Background:

The primary objective of this study was to compare the effect of ventilation using the ProSeal™ laryngeal mask airway (PLMA) with facemask and oropharyngeal airway (FM), prior to laryngoscopy, on arterial oxygenation in morbidly obese patients undergoing bariatric surgery.

Methods:

Forty morbidly obese patients were randomly recruited to either PLMA or FM. After pre-oxygenation (FiO₂ 1.0) in the ramp position with continuous positive airway pressure of 10 cm H₂O for 5 min, anaesthesia was induced. Following loss of jaw thrust oropharyngeal airway, the FM and PLMA were inserted. On achieving paralysis, volume control ventilation with PEEP (5 cm H₂O) was initiated. The difficulty in mask ventilation (DMV) in FM, number of attempts at PLMA and laryngoscopy were graded (Cormack and Lehane) in all patients. Time from onset of laryngoscopy to endotracheal tube confirmation was recorded. Hypoxia was defined as mild (SpO₂ ≤95%), moderate (SpO₂ ≤90%) and severe (SpO₂ ≤85%).

Results:

Significant rise in pO₂ was observed within both groups (P=0.001), and this was significantly higher in the PLMA (P=0.0001) when compared between the groups. SpO₂ ≥ 90% (P=0.018) was seen in 19/20 (95%) patients in PLMA and 13/20 (65%) in FM at confirmation of tracheal tube. A strong association was found between DMV and Cormack Lehane in the FM group and with number of attempts in the PLMA group. No adverse events were observed.

Conclusion:

ProSeal™ laryngeal mask airway as conduit prior to laryngoscopy in morbidly obese patients seems effective in increasing oxygen reserves, and can be suggested as a routine airway management technique when managing the airway in the morbidly obese.

Respiratory physiology and pulmonary complications in obesity

Obesity is generally accepted as a global epidemic and the most common metabolic disorder in the world. Obesity affects every organ system but the consequences on the respiratory system are often underappreciated. While the respiratory consequences of being overweight are predominantly mechanical, an inflammatory element has also been proposed. For this discussion, the components of the respiratory system can be divided into the airways, pulmonary parenchyma, pulmonary vasculature, and the upper respiratory tract. This section will discuss respiratory physiology and the mechanisms leading to breathing difficulties in obesity followed by the impact of obesity on commonly occurring pulmonary disorders.

Assessment of pulmonary functions in obese adolescent boys

BACKGROUND

Obesity is rapidly escalating in India in all age groups. School-based data indicate a prevalence rate between 5.6% and 24% in children and adolescents. Adolescent obesity is associated with a greater long-term risk of hypertension and type 2 diabetes mellitus in adulthood. However, studies investigating pulmonary functions in obese adolescents are few. The present study assesses pulmonary functions in obese adolescent boys from a school in Baroda city, Gujarat.

AIMS

(i) To assess the dynamic lung functions in obese adolescent boys. (ii) To determine the predominant lung function impairment associated with obesity in adolescence.

MATERIALS AND METHODS

Dynamic lung functions were measured in 30 obese adolescent boys and an equal number of age-matched controls using MEDI:SPIRO software (Maestros Mediline Systems Ltd., Navi Mumbai, India).

RESULTS

Forced expiratory volume in the 1(st) second (FEV(1))/forced vital capacity (FVC) and maximum voluntary ventilation (MVV) were significantly decreased in the obese group (P < 0.001). Pulmonary functions in the study population correlated negatively with various indices of obesity, viz. weight, body mass index (BMI), waist circumference, hip circumference, and waist-to-hip ratio. The strongest negative correlation was between BMI and FEV(1)/FVC (P < 0.001) and between BMI, MVV, and Forced Expiratory Flow (FEF(25-75%)) (P < 0.001). Waist-to-hip ratio in the study population correlated negatively with MVV (P < 0.01), but not with FEV(1)/FVC.

CONCLUSIONS

Lung function impairment, particularly decreased MVV and reduced FEV(1)/FVC ratio, is associated with obesity in adolescence. In addition, pulmonary functions deteriorate with increasing obesity in adolescence and correlate negatively with various indices of obesity, viz. weight, BMI, waist circumference, hip circumference, and waist-to-hip ratio. This study reveals another health hazard associated with obesity and highlights the need to aggressively reduce weight at a younger age.

Effects of progressive increase in body weight on lung function in six groups of body mass index

OBJECTIVE

To evaluate the effects of the progressive increase in body weight on lung function by oxygen peripheral saturation, spirometry and maximal respiratory pressures in different degrees of obesity.

METHODS

Cross-sectional study including 140 patients in clinical and surgical evaluation for obesity treatment. The selected patients were divided into six groups of body mass index (BMI), including a control group of non-obese and a subdivision for the morbidly obese into three subgroups.

RESULTS

Significant differences were demonstrated between the groups regarding oxygen peripheral saturation (SpO2) (p < 0.001), forced vital capacity (FVC) (p < 0.002, p < 0.02) and forced expiratory volume in one second (FEV1) (p < 0.001, p < 0.03) in relative and absolute values, respectively. Group VI (BMI > 50.9 kg/m²) showed significant differences (SpO2, FVC and FEV1) when compared with the other groups (except group V) and group V (BMI > 45 to 49.9 kg/m²) with the group control. The other variables (FEV1/FVC ratio, forced expiratory flow 25-75 [FEF25-75] and maximal respiratory pressure) did not show any statistical differences.

CONCLUSION

Lung function is influenced by the progressive increase in BMI, with changes in lung function better demonstrated when BMI > 45 kg/m²; these changes are more evident when BMI > 50.9 kg/m².

Candidates for bariatric surgery: morbidly obese patients with pulmonary dysfunction

Obesity is a well-known major risk factor of cardiovascular disease and is associated with various comorbidities. The impact of obesity on pulmonary function remains unclear. Reductions in chest wall compliance and respiratory muscle strength due to a high percent body fat and localized fat distribution contributes to impaired pulmonary function and the occurrence of adverse respiratory symptoms. Dietary modifications and pharmaceutical agents are not effective in the long-term treatment of obesity. Treatment of morbidly obese patients using bariatric surgery has increased each year, especially after the introduction of video laparoscopic techniques. Effective weight loss after bariatric surgery may improve cardiovascular disease risk factors, including diabetes, hypertension, dyslipidemia, atherosclerosis, inflammation, chronic kidney disease, obstructive sleep apnea, and obesity hypoventilation syndrome. Bariatric surgery has also been associated with significantly improved respiratory symptoms and pulmonary function. We currently present a review of principal studies that evaluated the effects of obesity on pulmonary function and the identification of anthropometric factors of obesity that correspond to the reversal of respiratory symptoms and impaired pulmonary function after bariatric surgery.

Função pulmonar de obesos mórbidos submetidos à cirurgia bariátrica

OBJETIVO: Comparar a função pulmonar de indivíduos obesos mórbidos submetidos à gastroplastia. MÉTODOS: Participaram da pesquisa 25 indivíduos, divididos em grupo experimental com 15 sujeitos (feminino = 13 e masculino = 2) e grupo controle com 10 sujeitos (feminino = 8 e masculino = 2). Foram mensurados os valores espirométricos na fase pré-operatória e na fase pós-operatória, três meses após a cirurgia. RESULTADOS: Verificou-se diferença significante intragrupo na análise inicial e após os três meses de acompanhamento de peso, índice de massa corporal (IMC), Capacidade Vital forçada (CVF), Volume de Reserva Expiratório (VRE), Capacidade Inspiratória (CI) e do Fluxo Expiratório Forçado (FEF25-75%), nos indivíduos que foram submetidos à cirurgia. Para os resultados obtidos da análise de diferença entre os grupos experimental e controle na análise de grupo e tempo, foram considerados significativos a CVF e o VRE. Verificou-se que aqueles que apresentavam distúrbios inespecíficos na fase pré-operatória passaram a ter função pulmonar normal na fase pós-operatória. Não foram verificadas diferenças significativas entre as características de proporções da espirometria entre os grupos e na avaliação intragrupo experimental. CONCLUSÃO: A cirurgia bariátrica influencia na melhora da função pulmonar, observando que um tempo maior de acompanhamento desses indivíduos pode nos mostrar resultados ainda mais confirmatórios sobre a importância da perda de peso para a função pulmonar.

Pericardial fat is associated with impaired lung function and a restrictive lung pattern in adults: the Jackson Heart Study

BACKGROUND

Impaired lung function has been linked to obesity and systemic inflammation. Pericardial fat has been shown to be associated with anomalies in cardiac structure, function, and atherosclerosis. We hypothesized that pericardial fat may have a similar role in the impairment of lung function.

METHODS

Cross-sectional associations of pericardial fat volumes, quantified by multidetector CT scan, with FEV(1) and FVC assessed by spirometry, were investigated in 1,293 participants (54.5 ± 10.8 years; 66.4% women) in the Jackson Heart Study. We also examined whether these associations were independent of visceral adipose tissue (VAT).

RESULTS

Pericardial fat was associated with impaired lung function after multivariable adjustment, but these associations generally did not remain after adjustment for VAT. An exception was the FEV(1)/FVC ratio. Higher pericardial fat volumes were associated with higher odds of a restrictive lung pattern and lower odds of airway obstruction. Participants in the highest quartile had the highest odds of a restrictive lung pattern (OR, 1.85; 95% CI, 1.22-2.79, compared with quartile 1), even after adjustment for VAT. The odds of obstruction decreased across increasing quartiles of pericardial fat. These relationships were generally graded, suggesting dose-response trends.

CONCLUSIONS

Pericardial fat is generally associated with lower lung function and independently associated with a restrictive lung pattern in middle-aged and elderly adults. Further research is needed to fully understand the mechanisms through which pericardial fat contributes to pulmonary anomalies.

Impaired response to deep inspiration in obesity

Deep inspirations modulate airway caliber and airway closure and their effects are impaired in asthma. The association between asthma and obesity raises the question whether the deep inspiration (DI) effect is also impaired in the latter condition. We assessed the DI effects in obese and nonobese nonasthmatics. Thirty-six subjects (17 obese, 19 nonobese) underwent routine methacholine (Mch) challenge and 30 of them also had a modified bronchoprovocation in the absence of DIs. Lung function was monitored with spirometry and forced oscillation (FO) [resistance (R) at 5 Hz (R5), at 20 Hz (R20), R5-R20 and the integrated area of low-frequency reactance (AX)]. The response to Mch, assessed with area under the dose-response curves (AUC), was consistently greater in the routine challenge in the obese (mean ± SE, obese vs. nonobese AUC: R5: 15.7 ± 2.3 vs. 2.4 ± 2.0, P < 0.0005; R20: 5.6 ± 1.4 vs. 1.4 ± 1.2, P = 0.027; R5-R20: 10.2 ± 1.6 vs. 0.9 ± 0.1.4, P < 0.0005; AX: 115.6 ± 22.0 vs. 1.5 ± 18.9, P < 0.0005), but differences between groups in the modified challenge were smaller, indicating reduced DI effects in obesity. Given that DI has bronchodilatory and bronchoprotective effects, we further assessed these components separately. In the obese subjects, DI prior to Mch enhanced Mch-induced bronchoconstriction, but DI after Mch resulted in bronchodilation that was of similar magnitude as in the nonobese. We conclude that obesity is characterized by increased Mch responsiveness, predominantly of the small airways, due to a DI effect that renders the airways more sensitive to the stimulus.

Pulmonary function and quality of life in patients with morbid obesity six months after bariatric surgery

PURPOSE

To investigate the body weight, pulmonary function and quality of life of twenty patients with morbid obesity six months after the Fobi-Capella operation.

METHODS

Patients were evaluated before and six months after surgery. The patients were mainly female (75%), the average age was 40.5 ± 10.27 years; average weight 110.11 kg ± 21.77 and average body mass index (BMI) 39.93 ± 7.13 kg/m² in the postoperative evaluation. Pulmonary function was assessed by spirometry using a Pulmonet/Godart NV Bilt Vetr Hotland spirometer and quality of life was assessed by applying the Moorehead-Ardelt questionnaire. The pre- and postoperative spirometry values were compared by the paired Student t test and the correlation between weight loss and pulmonary function was determined by linear regression, with the level of significance set at p < 0.05.

RESULTS

The spirometry variables Respiratory Frequency (RF), Expiratory Reserve Volume (ERV) and Functional Residual Capacity (FRC) differed significantly between the pre- and postoperative periods, whereas Residual Volume (RV), Vital Capacity (VC), Total Lung Capacity (TLC), FEF25-75 (Forced Expiratory Flow between 25 and 75% FVC) and FEV1/FVC% (Forced Expiratory Volume in the 1st second/ Forced Vital Capacity ratio) did not differ between periods. Only one patient reported worsening of quality of life. There was a positive correlation between weight loss and ERV (p=0.0117, r=0.5514), but no correlations were observed for the other variables.

CONCLUSIONS

There was a significant weight loss and an improvement of pulmonary function as seen by respiratory frequency, reduction and increased expiratory reserve volume and functional residual capacity. The quality of life of the patients also improved after the Fobi-Capella operation.

Association between body composition and pulmonary function in elderly people: the Korean Longitudinal Study on Health and Aging

The age-related increase in body fat and decrease in muscle mass are associated with increased morbidity in elderly populations. Pulmonary function also decreases with age, but no study has investigated whether regional body composition is associated with pulmonary function in an older population. The Korean Longitudinal Study on Health and Aging is a community-based cohort study of people aged > 65 years selected by random stratified sampling. Anthropometrics, biochemical factors, and lung function by spirometry were evaluated in 439 men (mean age of 75.9 ± 8.6 years) and 561 women (mean age of 76.0 ± 8.8 years). Dual-energy X-ray absorptiometry (DXA) was performed to assess the whole and regional body composition. Computed tomography (CT) was also used to measure fat or muscle distribution at the abdominal and mid-thigh levels. Although pulmonary function and muscle mass were inversely related to age, fat mass was not. After adjusting for age, height, BMI, smoking and exercise status, and high sensitivity C-reactive protein (hsCRP), fat mass in trunk or central area was inversely associated with lung function in both sexes (P < 0.01). Men with more muscle in trunk and mid-thigh level had better lung function (P < 0.01). The results of this community-based study show that regional body composition is significantly associated with lung function. Augmentation of muscle in the trunk and low extremity in men, and reduction of fat in the trunk and upper body in men and women may be helpful in maintaining lung function in the elderly population.

Emergency department management of the airway in obese adults

Airway management in obese adults can be challenging, and much of the literature on this subject focuses on elective surgical cases, rather than acutely ill patients. In this article, we review the emergency department evaluation of the airway in obesity, discussing anatomy, physiology, and pharmacology. In addition, we describe techniques and devices used to improve intubating conditions in the obese patient. After our review of the relevant literature, we conclude that research in this particular area of acute care remains in its infancy.

Obesity and acute lung injury

Acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) are common indications for ICU admission and mechanical ventilation. ALI/ARDS also consumes significant health care resources and is a common cause of death in ICU patients. Obesity produces changes in respiratory system physiology that could affect outcomes for ALI/ARDS patients and their response to treatment. Additionally, the biochemical alterations seen in obese patients, such as increased inflammation and altered metabolism, could affect the risk of developing ALI/ARDS in patients with another risk factor (eg, sepsis). The few studies that have examined the influence of obesity on the outcomes from ALI/ARDS are inconclusive. Furthermore, observed results could be biased by disparities in provided care.

Big breathing: the complex interaction of obesity, hypoventilation, weight loss, and respiratory function

Obesity places a significant load on the respiratory system, affecting lung volumes, respiratory muscle function, work of breathing, and ventilatory control. Despite this, most morbidly obese individuals maintain eucapnia. However, a subgroup of morbidly obese individuals will develop chronic daytime hypercapnia, described as the obesity hypoventilation syndrome (OHS). While obesity is obviously a crucial component of this syndrome, the relationship between excess fat accumulation and the development of awake hypercapnia is complex and extends beyond simply impairments of pulmonary mechanics and lung volumes as a consequence of obesity. Various compensatory mechanisms operate to maintain eucapnia even in the presence of extreme obesity. However, if compensation is impaired, hypoventilation will ensue. While obesity alone does not account for the development of hypoventilation, weight loss will produce significant improvements in lung function and awake gas exchange. Such improvements have the potential to substantially reduce morbidity and mortality in these individuals. Nevertheless, many individuals remain overweight despite substantial weight loss, with persistence of upper airway obstruction. Attention to this residual abnormality is important given the high incidence of cardiovascular abnormalities, including pulmonary hypertension, in individuals with OHS.

Physiology of obesity and effects on lung function

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

Lung disease assessment in primary ciliary dyskinesia: a comparison between chest high-field magnetic resonance imaging and high-resolution computed tomography findings

Background

Primary ciliary dyskinesia (PCD) is associated with pulmonary involvement that requires periodical assessment. Chest high-resolution computed tomography (HRCT) has become the method of choice to evaluate chronic lung disease, but entails exposure to ionizing radiation. Magnetic resonance imaging (MRI) has been proposed as a potential radiation-free technique in several chest disorders. Aim of our study is to evaluate whether high-field MRI is as effective as HRCT in identifying PCD pulmonary abnormalities. We also analyzed the relationships between the severity and extension of lung disease, and functional data.

Methods

Thirteen PCD patients (8 children/5 adults; median age, 15.2 yrs) underwent chest HRCT and high-field 3T MRI, spirometry, and deep throat or sputum culture. Images were scored using a modified version of the Helbich system.

Results

HRCT and MRI total scores were 12 (range, 6–20) and 12 (range, 5–17), respectively. Agreement between HRCT and MRI scores was good or excellent (r > 0.8). HRCT and MRI total scores were significantly related to forced vital capacity (r = -0.5, p = 0.05; and r = -0.7, p = 0.009, respectively) and forced expiratory volume at 1 second (r = -0.6, p = 0.03; and r = -0.7, p = 0.009, respectively).

Conclusion

Chest high-field 3T MRI appears to be as effective as HRCT in assessing the extent and severity of lung abnormalities in PCD. MRI scores might be used for longitudinal assessment and be an outcome surrogate in future studies.

Predictors of early mortality in implantable cardioverter-defibrillator recipients

AIMS

Multiple trials have shown that implantable cardioverter defibrillators (ICDs) prolong survival in secondary and primary prevention populations. However, in spite of the efficacy of these devices in terminating life-threatening arrhythmias, total mortality remains high.

METHODS AND RESULTS

We evaluated 1703 patients (mean age: 67 +/- 12 years, 82% male) with conventional ICD indications, who were enrolled and followed between 2001 and 2004 at 128 US centres. Patients were followed for up to a year, and vital status was obtained for 1655 patients (97%, median follow-up: 377 days). There were 183 deaths within 1 year of ICD implantation (1-year mortality rate: 16%). Predictors of mortality included a history of atrial fibrillation (AF, P < 0.0001), diabetes (P = 0.0001), failure to use cholesterol-lowering medications (P < 0.001), use of digitalis and derivatives (P < 0.0001), use of diuretics (P < 0.0001), low body mass index (BMI, P < 0.0001), increasing age (P < 0.0001), low left ventricular ejection fraction (P < 0.0001), low activity hours (P < 0.0001), elevated resting heart rate (P = 0.014), low mean arterial pressure (MAP, P = 0.007), and poor functional status (New York Heart Association class, P < 0.0001). In multivariate modelling, AF (P < or = 0.001), diabetes (P = 0.004), BMI (P = 0.001), MAP (P = 0.040), and functional class (P = 0.006) predicted mortality.

CONCLUSION

In this population undergoing ICD implantation, poor functional status, low MAP, diabetes, low BMI, and AF were strongly associated with death within a year.

Observations on the physiological interactions between obesity and asthma

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

Análise da função respiratória em pacientes obesos submetidos à operação Fobi-Capella

INTRODUÇÃO: O objetivo deste trabalho foi mensurar quantitativamente essas alterações respiratórias desses pacientes comparando-os até 30 dias de pós-operatório. MÉTODO: Foram realizadas avaliações respiratórias nos períodos pré e pós-operatório de cirurgia bariátrica em obesos mórbidos com IMC superior a 39kg/m², através de gasometria arterial, prova de função respiratória, manovacuômetria, incentivador da respiração e cirtometrias. Foram realizadas também orientações fisioterápicas respiratórias e tratamento no pós-operatório, com dados comparativos entre as avaliações feitas no préoperatório, no 1º, 14º·e 30º dia pós-operatórios. RESULTADOS: Até o 30º dia de pós-operatório, esses indivíduos não obtiveram diferença significativa nos parâmetros estudados, não havendo, em decorrência do tratamento fisioterápico, complicações respiratórias. CONCLUSÃO: Não houve alterações dos parâmetros analisados, nem complicações respiratórias neste estudo com intervenção fisioterápica pré e pós-operatório de cirurgia bariátrica. Estudos devem ser realizados, para mensuração de um tempo maior de pós-operatório e de exercícios específicos, podendo, assim apresentar resultados diferentes.

Respiratory muscle strength in obese individuals and influence of upper-body fat distribution

CONTEXT AND OBJECTIVE

Pulmonary dysfunction in obese individuals may be associated with respiratory muscle impairment, and may be influenced by predominance of upper-body fat distribution. The objective of this study was to evaluate the strength of respiratory muscles in obese individuals and to analyze the influence of adipose tissue distribution.

DESIGN AND SETTING

Cross-sectional study on the preoperative period prior to bariatric surgery. Research developed within the Postgraduate General Surgery Program, Faculdade de Medicina de Botucatu, Universidade Estadual Paulista (Unesp).

METHOD

Respiratory muscle strength was quantified by measuring maximum inspiratory and expiratory pressures (PImax and PEmax) in obese candidates for bariatric surgery. Adipose tissue distribution was assessed using the waist-hip circumference ratio (WHR). PImax, PEmax and WHR were compared with normal reference values and also in groups with different body mass index (BMI).

RESULTS

We evaluated 23 men and 76 women. All underwent PImax evaluation and 86 underwent PEmax. The mean BMI was 44.42 kg/m2. PImax and PEmax were within normal values; WHR showed that there was predominance of upper-body fat distribution; and there were no correlations among the variables studied. There was no significant variance among the variables PImax, PEmax and WHR when the study population was divided into groups with different BMI.

CONCLUSION

In the obese population studied, the excess weight did not result in impairment of respiratory muscle strength, and their predominant upper-body fat distribution also did not influence respiratory muscle strength.

Altered respiratory physiology in obesity

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