Brazilian studies on pulmonary function in COPD patients: what are the gaps?

Maximum Voluntary Ventilation and Its Relationship With Clinical Outcomes in Subjects With COPD

BACKGROUND

Previous studies have reported that maximum voluntary ventilation (MVV) may be better associated with commonly used outcomes in COPD than FEV₁ and may provide information on respiratory mechanics. In this study, we aimed to investigate the relationship between MVV and clinical outcomes in COPD and to verify whether MVV predicts these outcomes better than FEV₁.

METHODS

We conducted a cross-sectional study involving individuals with COPD. Lung function was assessed with spirometry; maximum inspiratory and expiratory pressures (P_Imax and P_Emax, respectively) were assessed with manuvacuometry; and functional exercise capacity was assessed with the 6-min-walk test (6MWT). Dyspnea was assessed with the modified Medical Research Council (mMRC) scale; functional status was assessed with the modified Pulmonary Functional Status and Dyspnea Questionnaire (PFSDQ-m); and health status was assessed with the COPD Assessment Test (CAT). Correlations were verified with the Spearman coefficient, and stepwise multiple linear regression models investigated the predictors of clinical outcomes.

RESULTS

Our study included 157 subjects: 82 males; median (interquartile range) age 66 (61-73) y; FEV₁ 46 (33-57) % predicted; 6MWT 86 (76-96) % predicted; PFSDQ-m total score 34 (14-57); and CAT total score 13 (7-19). Moderate correlations were found between MVV and P_Imax (r = 0.40), 6MWT (r = 0.50), mMRC (r = -0.56), and total scores on the PFSDQ-m (r = -0.40) and the CAT (r = -0.54). In the regression models, MVV was a predictor of almost all clinical outcomes, unlike FEV₁.

CONCLUSIONS

MVV correlates moderately with clinical outcomes commonly used in the evaluation of individuals with COPD, and MVV is a better predictor of respiratory muscle strength, functional exercise capacity, and patient-reported outcomes than FEV₁.

Epidemiology of Chronic Obstructive Pulmonary Disease in Brazil: a systematic review and meta-analysis

Chronic Obstructive Pulmonary Disease (COPD) is among the leading causes of morbidity and mortality in developing countries; however, few systematic reviews are available in the literature. This review examines the prevalence of COPD in the Brazilian population. For this purpose, a systematic review and meta-analysis was conducted of epidemiological observational studies indexed in the databases PubMed, Cochrane, Ovid, Scopus, ScienceDirect, SciELO, Lilacs, and Google Scholar published up to May 2018. The prevalence was estimated using a random effects model. Of the 1,182 articles identified, 12 were eligible. The prevalence of COPD in Brazil was 17% (95%CI: 13-22; I2 = 94%) and the region with the highest prevalence of COPD was the Center-western region (25%), followed by the Southeastern region (23%). The Southern region had the lowest prevalence among the studies (12%). We found that Brazil has a high occurrence of COPD, higher than the estimates of Latin American and world population Hence, additional studies are necessary to support intervention strategies, as well as formulation of specific public health policies to control and prevent COPD.

Handgrip Strength and Pulmonary Disease in the Elderly: What is the Link?

Societies in developed countries are aging at an unprecedented rate. Considering that aging is the most significant risk factor for many chronic lung diseases (CLDs), understanding this process may facilitate the development of new interventionist approaches. Skeletal muscle dysfunction is a serious problem in older adults with CLDs, reducing their quality of life and survival. In this study, we reviewed the possible links between handgrip strength (HGS)—a simple, noninvasive, low-cost measure of muscle function—and CLDs in the elderly. Different mechanisms appear to be involved in this association, including systemic inflammation, chronic hypoxemia, physical inactivity, malnutrition, and corticosteroid use. Respiratory and peripheral myopathy, associated with muscle atrophy and a shift in muscle fiber type, also seem to be major etiological contributors to CLDs. Moreover, sarcopenic obesity, which occurs in older adults with CLDs, impairs common inflammatory pathways that can potentiate each other and further accelerate the functional decline of HGS. Our findings support the concept that the systemic effects of CLDs may be determined by HGS, and HGS is a relevant measurement that should be considered in the clinical assessment of the elderly with CLDs. These reasons make HGS a useful practical tool for indirectly evaluating functional status in the elderly. At present, early muscle reconditioning and optimal nutrition appear to be the most effective approaches to reduce the impact of CLDs and low muscle strength on the quality of life of these individuals. Nonetheless, larger in-depth studies are needed to evaluate the link between HGS and CLDs.

Advances in spirometry testing for lung function analysis

Introduction: Spirometry, the most common lung function test, is used to evaluate individuals with respiratory complaints or known respiratory disease. However, its underutilization and the misinterpretation of its parameters are causes for concern. Areas covered: This review describes new spirometry-derived metrics, new reference equations, recent recommendations for presentation of results, recent spirometry-based prevalence studies, and technological advances in spirometry equipment. Expert opinion: The underutilization of spirometry can be overcome by increasing access to portable, hand-held, and user-friendly spirometers, together with strategies that increase awareness of the importance of spirometry. New metrics derived from spirometry, together with traditional spirometric criteria, can identify individuals with structural lung disease and respiratory morbidity. Some problems with the reference equations were solved by the Global Lung Function Initiative (GLI), which covers a wider age range and more ethnic groups and provides limits of normality using the z-score. Despite these advantages, the GLI equations lack data from large populations (especially those from Africa, South Asia, and Latin America) and greater representation of older people. Another disadvantage attributed to the GLI is the lack of predicted values for peak expiratory flow and other airflows, limiting the interpretation of the maximal expiratory flow-volume curve.

Forced oscillation technique for early detection of the effects of smoking and COPD: contribution of fractional-order modeling

Purpose

The aim of the present study was to evaluate the performance of the forced oscillation technique (FOT) for the early diagnosis of the effects of smoking and COPD. The contributions of the integer-order (InOr) and fractional-order (FrOr) models were also evaluated.

Patients and methods

In total, 120 subjects were analyzed: 40 controls, 40 smokers (20.3±9.3 pack-years) and 40 patients with mild COPD.

Results

Initially, it was observed that traditional FOT parameters and the InOr and FrOr models provided a consistent description of the COPD pathophysiology. Mild COPD introduced significant increases in the FrOr inertance, damping factor and hysteresivity (P<0.0001). These parameters were significantly correlated with the spirometric parameters of central and small airway obstruction (P<0.0001). The diagnostic accuracy analyses indicated that FOT parameters and InOr modeling may adequately identify these changes (area under the receiver operating characteristic curve – AUC >0.8). The use of FrOr modeling significantly improved this process (P<0.05), allowing the early diagnosis of smokers and patients with mild COPD with high accuracy (AUC >0.9).

Conclusion

FrOr modeling improves our knowledge of modifications that occur in the early stages of COPD. Additionally, the findings of the present study provide evidence that these models may play an important role in the early diagnosis of COPD, which is crucial for improving the clinical management of the disease.

Nitrogen single-breath washout test for evaluating exercise tolerance and quality of life in patients with chronic obstructive pulmonary disease

Pulmonary function tests (PFTs) traditionally used in clinical practice do not accurately predict exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). The aim of this study was to assess whether the nitrogen single-breath washout (N₂SBW) test explains exercise intolerance and poor quality of life in stable COPD patients. This cross-sectional study included 31 patients with COPD subjected to PFTs (including the N₂SBW test) and a cardiopulmonary exercise test (CPET). Patients were also evaluated using the following questionnaires: the COPD assessment test (CAT), the 36-Item Short Form Health Survey (SF36) and St. George's Respiratory Questionnaire (SGRQ). Peak oxygen uptake (peak VO₂) was negatively correlated with the phase III slope of the N₂SBW (SIII_N2) (r=-0.681, P<0.0001) and positively correlated with forced expiratory volume in one second (FEV₁; r=0.441, P=0.013). Breathing reserve was negatively correlated with SIII_N2, closing volume/vital capacity, and residual volume (RV) (r=-0.799, P<0.0001; r=-0.471, P=0.007; r=-0.401, P=0.025, respectively) and positively correlated with FEV₁, forced vital capacity (FVC) and FEV₁/FVC (r=0.721; P<0.0001; r=0.592, P=0.0004; r=0.670, P<0.0001, respectively). SIII_N2 and CAT were independently predictive of VO₂ and breathing reserve at peak exercise. RV, FVC, and FEV₁ were independently predictive of the SF36-physical component summary, SF36-mental component summary, and breathing reserve, respectively. The SGRQ did not present any independent variables that could explain the model. In stable COPD patients, inhomogeneity of ventilation explains a large degree of exercise intolerance assessed by CPETs and, to a lesser extent, poor quality of life.