Spirometry reference values in the Brazilian population

The aim of the present study was to provide new spirometry reference equations in a sample of the Brazilian population for the following parameters: forced vital capacity (FVC), forced expiratory volume in 1 second (FEV₁), FEV₁/FVC ratio, peak of expiratory flow (PEF), forced expiratory flow at 50% (FEF_50%)_, 75% average vital capacity (FEF_25-75%), and average forced expiratory flow time (FEFT). This was a prospective study using results from chest radiographs, electrocardiograms, and questionnaires to investigate the participants' respiratory symptoms, sedentarism, and comorbidities (Charlson comorbidity index). From December 2010 to July 2014, individuals were randomly selected from various locations in the state of Rio de Janeiro. All individuals were examined by a single technician in the morning at the laboratory, and performed the spirometry with the same spirometer. Spirometry values were tabulated for the creation of three equation models: linear regression, logarithmic regression, and logarithms through a method that incorporates the lambda, median, and coefficient of variation (LMS method). Initially, 7003 individuals from both genders were contacted, and 454 were recruited. The data from the new equations were compared with one Brazilian and eight international equations, resulting in a high correlation (r>0.9). The values derived from the LMS method and linear regression were very similar (P>0.5), and both could be used to acquire the reference values for Brazilian spirometry. Data derived from the equations of this study were different from the current Brazilian equation, which could be justified by the different method used.

Ventilation distribution and small airway function in patients with systemic sclerosis

BACKGROUND

Despite the importance of traditional pulmonary function tests (PFTs) in managing systemic sclerosis (SSc), many patients with pulmonary disease diagnosed by computed tomography (CT) present with normal PFTs.

OBJECTIVE

To evaluate the efficacy of the nitrogen single-breath washout (N₂SBW) test in diagnosing SSc and to correlate N₂SBW parameters with the PFT indexes used in the follow-up of these patients, clinical data, and CT findings.

METHODS

Cross-sectional study in which 52 consecutive SSc patients were subjected to spirometry, body plethysmography, analysis of the diffusing capacity for carbon monoxide (DLCO), analysis of respiratory muscle strength, N₂SBW testing, and CT analysis.

RESULTS

Twenty-eight patients had a forced vital capacity (FVC) that was <70% of the predicted value. In the N₂SBW test, 44 patients had a phase III slope (Phase III slope_N2SBW) that was >120% of the predicted value, while 15 patients had a closing volume/vital capacity (CV/VC) that was >120% of the predicted value. A significant difference in Phase III slope_N2SBW was observed when the patients with predominant traction bronchiectasis and honeycombing were compared to the patients with other CT patterns (p<0.0001). The Phase III slope_N2SBW was correlated with FVC (r_s=-0.845, p<0.0001) and DLCO (r_s=-0.600, p<0.0001), and the CV/VC was correlated with FVC (r_s=-0.460, p=0.0006) and residual volume/total lung capacity (r_s=0.328, p=0.017).

CONCLUSION

Ventilation heterogeneity is a frequent finding in SSc patients that is associated with restrictive damage, changes in pulmonary diffusion, and CT patterns. In addition, approximately one-third of the patients presented with findings that were compatible with small airway disease.

Can we use the 6-minute step test instead of the 6-minute walking test? An observational study

OBJECTIVE

To verify whether or not heart rate is maintained below the calculated submaximal level in healthy, sedentary subjects when they perform the 6-minute step test (6MST) and the 6-minute walking test (6MWT), and to compare the maximal heart rate achieved by the subjects at the end of each test.

DESIGN

Observational, cross-sectional study.

SETTING

One tertiary centre.

PARTICIPANTS

Two hundred and fifty-three participants from a pool of 330 healthy and sedentary subjects between 20 and 80 years of age.

INTERVENTIONS

Both the 6MWT and the 6MST were performed in accordance with the American Thoracic Society's statement. Dyspnoea, blood pressure, oxygen saturation and heart rate were measured before and after each test.

RESULTS

Mean heart rate immediately after the 6MST was significantly higher than mean heart rate immediately after the 6MWT {125 [standard deviation (SD) 19] vs 111 (SD 17) beats/minute; mean difference 13 (95% confidence interval of the difference 10 to 16); P<0.001}. Moreover, mean heart rate during (3minutes after commencement) the 6MST [118 (SD 18) beats/minute] was statistically higher than mean heart rate at the end of the 6MWT [111 (SD 18) beats/minute; P<0.001]. None of the subjects achieved the calculated submaximal heart rate.

CONCLUSIONS

The 6MST and 6MWT are safe and produce submaximal effort in healthy participants. However, they are not interchangeable, and the 6MST requires more energy than the 6MWT.