Relationship between body composition, inflammation and lung function in overweight and obese asthma

Background: The obese-asthma phenotype is not well defined. The aim of this study was to examine both mechanical and inflammatory influences, by comparing lung function with body composition and airway inflammation in overweight and obese asthma. Methods: Overweight and obese (BMI 28-40 kg/m2) adults with asthma (n = 44) completed lung function assessment and underwent full-body dual energy x-ray absorptiometry. Venous blood samples and induced sputum were analysed for inflammatory markers. Results: In females, android and thoracic fat tissue and total body lean tissue were inversely correlated with expiratory reserve volume (ERV). Conversely in males, fat tissue was not correlated with lung function, however there was a positive association between android and thoracic lean tissue and ERV. Lower body (gynoid and leg) lean tissue was positively associated with sputum %neutrophils in females, while leptin was positively associated with android and thoracic fat tissue in males. Conclusions: This study suggests that both body composition and inflammation independently affect lung function, with distinct differences between males and females. Lean tissue exacerbates the obese-asthma phenotype in females and the mechanism responsible for this finding warrants further investigation

Clinical use of pulse oximetry: official guidelines from the Thoracic Society of Australia and New Zealand

Pulse oximetry provides a simple, non-invasive approximation of arterial oxygenation in a wide variety of clinical settings including emergency and critical-care medicine, hospital-based and ambulatory care, perioperative monitoring, inpatient and outpatient settings, and for specific diagnostic applications. Pulse oximetry is of utility in perinatal, paediatric, adult and geriatric populations but may require use of age-specific sensors in these groups. It plays a role in the monitoring and treatment of respiratory dysfunction by detecting hypoxaemia and is effective in guiding oxygen therapy in both adult and paediatric populations. Pulse oximetry does not provide information about the adequacy of ventilation or about precise arterial oxygenation, particularly when arterial oxygen levels are very high or very low. Arterial blood gas analysis is the gold standard in these settings. Pulse oximetry may be inaccurate as a marker of oxygenation in the presence of dyshaemoglobinaemias such as carbon monoxide poisoning or methaemoglobinaemia where arterial oxygen saturation values will be overestimated. Technical considerations such as sensor position, signal averaging time and data sampling rates may influence clinical interpretation of pulse oximetry readings

Trends in anthropometry and severity of sleep-disordered breathing over two decades of diagnostic sleep studies in an Australian adult sleep laboratory

Objective: To document trends in subject demographics, anthropometry and sleep disorder severity over 21 years of diagnostic sleep studies. Design, participants and setting: A retrospective observational study of consecutive subjects undergoing initial diagnostic polysomnography for investigation of possible sleep disorders in a university-affiliated tertiary public metropolitan hospital in the Hunter New England region of New South Wales between 1987 and 2007. Main outcome measures: Body weight, body mass index (BMI) and severity of sleep-related breathing disorders (apnoea-hypopnoea index [AHI]). Results: Between 1987 and 2007, 14 648 new diagnostic sleep studies were performed The median age of subjects (51 years, interquartile range, 41-61 years) did not change over time and the proportion of women increased from 20% to 39% Median body weight increased from 89 kg to 99 kg for men (11%) and from 73 kg to 85 kg for women (16%), equating to a yearly increase in median BMI of 0 15 kg/m(2) for men and 0 14 kg/m(2) for women. The proportion of subjects who were morbidly obese (BMI >= 40) increased from 3% in 1987 to 16% in 2007. Median AHI progressively increased from 1992-1995 to 2004-2007 (from 65 events/h to 143 events/h, P < 0001), indicating increasing disease severity. Over the same period, for every unit increase in BMI, AHI increased by 5 5 events/h for men and by 2 8 events/h for women. About 80% of the observed variance in AHI over this period was attributable to variance in BMI. Conclusion: There is a continuing trend towards increasing body weight and BMI in people undergoing diagnostic sleep studies. Our data do not support the hypothesis that increased accessibility to diagnostic services and increased awareness of sleep disorders are resulting in a decline in disease severity. These findings are consistent with the premise that worsening severity in sleep-disordered breathing is primarily attributable to increasing obesity

Grading the severity of airways obstruction: new wine in new bottles

The objective of this study was to redesign the current grading of obstructive lung disease so that it is clinically relevant and free of biases related to age, height, sex and ethnic group. Spirometric records from 17 880 subjects (50.4% female) from hospitals in Australia and Poland, and 21 191 records (53.0% female) from two epidemiological studies (age range 18–95 years) were analysed. We adopted the American Thoracic Society(ATS)/European Respiratory Society (ERS) criteria for airways obstruction based on an forced expiratory volume in 1 s (FEV₁)/(forced) vital capacity ((F)VC) ratio below the fifth percentile and graded the severity of pulmonary function impairment using z-scores for FEV₁, which signify how many standard deviations a result is from the mean predicted value. Using the lower limit of normal for FEV₁/(F)VC and z-scores for FEV₁ of -2, -2.5, -3 and -4 to delineate severity grades of airflow limitation leads to close agreement with ATS/ERS severity classifications and removes age, sex and height related bias. The new classification system is simple, easily memorised and clinically valid. It retains previously established associations with clinical outcomes and avoids biases due to the use of per cent predicted FEV₁. Combined with the Global Lung Function prediction equations it provides a worldwide diagnostic standard, free of bias due to age, height, sex and ethnic group

Implications of adopting the Global Lungs Initiative 2012 all-age reference equations for spirometry

The aim of this study was to determine the diagnostic and interpretative consequences of adopting the Global Lungs Initiative (GLI) 2012 spirometric prediction equations. We assessed spirometric records from 17 572 subjects (49.5% females), aged 18-85 years, from hospitals in Australia and Poland. We calculated predicted forced expiratory volume in 1 s (FEV1), forced expiratory volume (FVC), FEV1/FVC and lower limits of normal (LLN) using European Community for Steel and Coal (ECSC), National Health and Nutrition Examination Survey (NHANES) III and GLI 2012 equations. Obstruction was defined as FEV1/FVC<LLN and a restrictive pattern as FEV1/FVC>LLN and FVC<LLN. Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage 2 and higher was defined as FEV1/FVC <0.70 and FEV1 <80% pred. GLI 2012 equations produce similar predicted values for FEV1 and FVC compared with NHANES, but produce larger values than ECSC. Differences in the LLN lead to an important increase in the prevalence rate of a low FVC compared to ECSC, and a significant decrease compared to NHANES prediction equations. Adopting GLI 2012 equations has small effects on the prevalence rate of airway obstruction. GOLD stages 2-4 lead to >20% underdiagnosis of airway obstruction up to the age of 55 years and to 16-23% overdiagnosis in older subjects. GLI 2012 equations increase the prevalence of a "restrictive spirometric pattern" compared to ECSC but decrease it compared to NHANES

Measurement of FEF25–75% and FEF75% does not contribute to clinical decision making

The aim of this study was to determine the added value of measuring the forced expiratory flow at 25-75% of forced vital capacity (FVC) (FEF25-75%) and flow when 75% of FVC has been exhaled (FEF75%) over and above the measurement of the forced expiratory volume in 1 s (FEV1), FVC and FEV1/FVC ratio. We used spirometric measurements of FEV1>, FVC and FEF25-75% from 11654 white males and 11113 white females, aged 3-94 years, routinely tested in the pulmonary function laboratories of four tertiary hospitals. FEF75% was available in 8254 males and 7407 females. Predicted values and lower limits of normal, defined as the fifth percentile, were calculated for FEV1, FVC, FEV1/FVC ratio, FEF25-75% and FEF75% using prediction equations from the Global Lung Function Initiative. There was very little discordance in classifying test results. FEF25-75% and FEF75% were below the normal range in only 2.75% and 1.29% of cases, respectively, whereas FEV1, FVC and FEV1/FVC ratio were within normal limits. Airways obstruction went undetected by FEF25-75% in 2.9% of cases and by FEF75% in 12.3% of cases. Maximum mid-expiratory flow and flow towards the end of the forced expiratory manoeuvre do not contribute usefully to clinical decision making over and above information from FEV1, FVC and FEV1/FVC ratio