Body composition in patients with chronic obstructive pulmonary disease: which method to use in clinical practice?

The objective of the present study was to compare anthropometry with bioelectrical impedance (BIA) in relation to densitometry (dual-energy X-ray absorptiometry; DEXA) as methods of nutritional assessment and body composition in out-patients with chronic pulmonary obstructive disease (COPD). We conducted a cross-sectional clinical study with sixty-one patients with COPD (forty-two men and nineteen women), mean age of 66.5 (sd 7.9) years and forced expiratory volume in 1 s of 1.3 (sd 0.6) litres (52.2 (sd 19.8) % predicted), referred to the Pulmonary Rehabilitation Center. The patients were evaluated regarding nutrition status and body composition as determined by anthropometry, BIA and DEXA. In the results, 34.4 % showed mild obstruction, 31.2 %, moderate and 34.4 %, severe obstruction. According to the BMI (mean 24.5 (sd 4.5) kg/m2), 45.9 % of the patients exhibited normal weight, while 27.9 % were underweight and 26.2 % were obese. Related to fat-free mass (FFM), anthropometry and BIA compared with DEXA presented high correlations (r 0.96 and 0.95 respectively; P < 0.001) and high reliability between the methods (alpha 0.98; P < 0.001). Agreement analysis between the methods shows that anthropometry overestimates (0.62 (sd of the difference 2.89) kg) while BIA underestimates FFM (0.61 (sd of the difference 2.82) kg) compared with DEXA. We concluded that according to the nutritional diagnosis, half of our population of patients with COPD showed normal weight, while the other half comprised equal parts obese and underweight patients. Body composition estimated by BIA and anthropometry presented good reliability and correlation with DEXA; the three methods presented satisfactory clinical accuracy despite the great disparity of the limits of agreement.

Peak VO2 correction for fat-free mass estimated by anthropometry and DEXA.

PURPOSE: Anthropometric (ANTHRO) and dual-energy x-ray absorptiometric (DEXA) estimates of total body and leg fat-free masses (FFM) were obtained in 77 randomly selected sedentary men and women, aged 20-80: intermethod limits of agreement and their clinical significance, as inferred from the differences on peak VO2 corrected for FFMANTHRO and FFMDEXA, were determined. METHODS: Limits of agreement were calculated as mean bias +/- 95% confidence intervals: peak VO2 at maximum cycle ergometry was related to FFMANTHRO and FFMDEXA by using both standard (y x x(-1)) and power function ratios (allometry). RESULTS: Data distribution of the ANTHRO-DEXA differences presented significant heteroscedasticity in both sexes, i.e., differences were proportional to the mean (P < 0.05). After logarithmic transformation, the mean bias +/- 95% limits of agreement were expressed as ratios (ANTHRO x DEXA(-1) x// error ratio): these corresponded to 0.95 x// 1.11 or 0.99 x// 1.15 for total body FFM and 0.90 x// 1.10 or 1.02 x// 1.07 for leg FFM in men and women, respectively. In addition, we found different allometric exponents for FFMANTHRO and FFMDEXA: the intermethod differences, therefore, increased after power function expression (P < 0.05). CONCLUSION: Discrepancies between ANTHRO and DEXA measurements of FFM depend on the magnitude of the estimate: differences are typically within 10 to 15%. Importantly, FFM-corrected peak VO2 values can vary according to the method chosen for body composition assessment, especially when allometry is used for peak VO2 correction. These results demonstrate that ANTHRO-DEXA differences in FFM estimation do have relevant practical consequences for the analysis of maximum aerobic capacity in nontrained humans.

Reference values for lung function tests. II. Maximal respiratory pressures and voluntary ventilation.

The strength of the respiratory muscles can be evaluated from static measurements (maximal inspiratory and expiratory pressures, MIP and MEP) or inferred from dynamic maneuvers (maximal voluntary ventilation, MVV). Although these data could be suitable for a number of clinical and research applications, no previous studies have provided reference values for such tests using a healthy, randomly selected sample of the adult Brazilian population. With this main purpose, we prospectively evaluated 100 non-smoking subjects (50 males and 50 females), 20 to 80 years old, selected from more than 8,000 individuals. Gender-specific linear prediction equations for MIP, MEP and MVV were developed by multiple regression analysis: age and, secondarily, anthropometric measurements explained up to 56% of the variability of the dependent variables. The most cited previous studies using either Caucasian or non-Caucasian samples systematically underestimated the observed values of MIP (P < 0.05). Interestingly, the self-reported level of regular physical activity and maximum aerobic power correlates strongly with both respiratory and peripheral muscular strength (knee extensor peak torque) (P < 0.01). Our results, therefore, provide a new frame of reference to evaluate the normalcy of some useful indexes of respiratory muscle strength in Brazilian males and females aged 20 to 80.

Reference values for lung function tests: II. Maximal respiratory pressures and voluntary ventilation

The strength of the respiratory muscles can be evaluated from static measurements (maximal inspiratory and expiratory pressures, MIP and MEP) or inferred from dynamic maneuvers (maximal voluntary ventilation, MVV). Although these data could be suitable for a number of clinical and research applications, no previous studies have provided reference values for such tests using a healthy, randomly selected sample of the adult Brazilian population. With this main purpose, we prospectively evaluated 100 non-smoking subjects (50 males and 50 females), 20 to 80 years old, selected from more than 8,000 individuals. Gender-specific linear prediction equations for MIP, MEP and MVV were developed by multiple regression analysis: age and, secondarily, anthropometric measurements explained up to 56 per cent of the variability of the dependent variables. The most cited previous studies using either Caucasian or non-Caucasian samples systematically underestimated the observed values of MIP (P<0.05). Interestingly, the self-reported level of regular physical activity and maximum aerobic power correlates strongly with both respiratory and peripheral muscular strength (knee extensor peak torque) (P<0.01). Our results, therefore, provide a new frame of reference to evaluate the normalcy of some useful indexes of respiratory muscle strength in Brazilian males and females aged 20 to 80.

Prediction of metabolic and cardiopulmonary responses to maximum cycle ergometry: a randomised study.

All of the most widely-cited studies for the prediction of maximum exercise responses have utilized either volunteers or referred subjects. Therefore, selection bias, with overestimation of the reference values, is a likely consequence. In order to establish a set of predictive equations for the gas exchange, ventilatory and cardiovascular responses to maximum ramp-incremental cycle ergometry, this study prospectively evaluated 120 sedentary individuals (60 males, 60 females, aged 20-80), randomly-selected from >8,000 subjects. Regular physical activity pattern by questionnaire, body composition by anthropometry and dual energy X-ray absorptiometry (n = 75) and knee strength by isokinetic dynamometry were also assessed. Previously reported equations typically overestimated the subjects' peak oxygen uptake (p<0.05). Prediction linear equations for the main variables of clinical interest were established by backward stepwise regression analysis including: sex, age, knee extensor peak torque, bone-free lean leg mass, total and lean body mass, height, and physical activity scores. Reference intervals (95% confidence limits) were calculated: some of these values differed markedly from those formerly recommended. The results therefore might provide a more appropriate frame of reference for interpretation of the responses to symptom-limited ramp incremental cycle ergometry in sedentary subjects; i.e. those usually referred for clinical cardiopulmonary exercise tests.