Evaluation of maximal exercise capacity through the incremental shuttle walking test in lymphangioleiomyomatosis

BACKGROUND

The cardiopulmonary exercise test (CPET) is the gold standard for assessing aerobic fitness; however, it is expensive, not widely available, and requires specialized equipment and staff. The incremental shuttle walking test (ISWT) is an exercise field test used to evaluate exercise capacity and may be an alternative to CPET in patients with lymphangioleiomyomatosis (LAM).

OBJECTIVE

To investigate whether the ISWT can be used to assess maximal aerobic capacity in patients with LAM.

METHODS

Forty-five women were evaluated on two days, and they randomly performed the CPET and ISWT. The maximum oxygen uptake (peak VO2) was evaluated using gas analyzers in both tests. The carbon dioxide production (VCO2), respiratory exchange ratio (RER), and heart rate (HR) were compared during peak exercise. Pearson's correlation and Bland-Altman assessed the association and agreement, respectively. The intraclass correlation coefficient (ICC) was used to assess the reliability of the data.

RESULTS

All patients (46.1 ± 10.2 years) presented similar peak VO2, RER, and peak HR during the CPET and ISWT (15.6 ± 4.6 vs. 15.7 ± 4.4 ml·kg-1·min-1; 1.15±0.09 vs. 1.17±0.12; and 142.2 ± 18.6 vs. 141.5 ± 22.2 bpm, respectively; p>0.05). A good linear correlation (r = 0.79; p<0.001) and ICC (0.86; 95%CI 0.74-0.93) were observed between the peak VO2 in both tests. Predictive peak VO2 equations based on the ISWT performance are also presented.

CONCLUSION

Our results suggest that the ISWT can be used to assess maximal exercise performance in patients with LAM, and it is a valuable option to be used as an alternative to the CPET and predict maximal exercise capacity.

Comparison of two questionnaires which measure the health-related quality of life of idiopathic pulmonary fibrosis patients

The objective of the present study was to determine if there is a health-related quality of life (HRQL) instrument, generic or specific, that better represents functional capacity dysfunction in idiopathic pulmonary fibrosis (IPF) patients. HRQL was evaluated in 20 IPF patients using generic and specific questionnaires (Medical Outcomes Short Form 36 (SF-36) and Saint George's Respiratory Questionnaire (SGRQ), respectively). Functional status was evaluated by pulmonary function tests, 6-min walking distance test (6MWDT) and dyspnea indexes (baseline dyspnea index) at rest and after exercise (modified Borg scale). There was a restrictive pattern with impairment of diffusion capacity (total lung capacity, TLC = 71.5 +/- 15.6%, forced vital capacity = 70.4 +/- 19.4%, and carbon monoxide diffusing capacity = 41.5 +/- 16.2% of predicted value), a reduction in exercise capacity (6MWDT = 435.6 +/- 95.5 m) and an increase of perceived dyspnea score at rest and during exercise (6 +/- 2.5 and 7.1 +/- 1.3, respectively). Both questionnaires presented correlation with some functional parameters (TLC, forced expiratory volume in 1 s and carbon monoxide diffusing capacity) and the best correlation was with TLC. Almost all of the SGRQ domains presented a strong correlation with functional status, while in SF-36 only physical function and vitality presented a good correlation with functional status. Dyspnea index at rest and 6MWDT also presented a good correlation with HRQL. Our results suggest that a specific instead of a generic questionnaire is a more appropriate instrument for HRQL evaluation in IPF patients and that TLC is the functional parameter showing best correlation with HRQL.

The effect of massive weight loss on pulmonary function of morbid obese patients

STUDY OBJECTIVES

To test if morbid obesity causes pulmonary function changes and if massive weight loss have effect on pulmonary function (especially in subjects with BMI>or=60 kg/m(2)).

PARTICIPANTS

Thirty-nine morbid obese subjects before and after massive weight loss.

MEASUREMENTS AND RESULTS

Patients had baseline BMI>or=40 kg/m(2), pulmonary function test (PFT) before and after surgery for gastric volume reduction and massive weight loss, and presented no complaints unrelated to obesity. Based on initial BMI, the patients were divided in groups A (BMI 40-59.9 kg/m(2)) and B (BMI>or=60 kg/m(2)). Initially, group A (n=28) had normal PFT, however group B (n=11) presented FVC and FEV(1) measurements in the lowest limit of normality (with normal FEV(1)/FVC), significantly different from group A. After massive weight loss, the group B compared to A had a significant improvement in FVC (23.7% vs. 9.7%, P=0.012) and FEV(1) (25.6% vs. 9.1%, P=0.006); thus the initial difference in FVC and FEV(1) between groups no longer existed after weight loss.

CONCLUSIONS

These results point out that the severe morbid obesity (BMI>or=60 kg/m(2)) may lead to pulmonary function impairment and presents more prominent pulmonary function gain after massive weight reduction. The possible clinical implications of these results are that PFT abnormalities in subjects with BMI<60 kg/m(2) should probably be interpreted as consequence of intrinsic respiratory disease and that severe morbid obese patients may be encouraged to lose weight to improve their pulmonary function, especially those with concomitant pulmonary disorders.

Air pollution and mortality in elderly people: a time-series study in Sao Paulo, Brazil

The relationship between daily mortality of elderly (65+ y) persons and air pollution in the metropolitan area of Sao Paulo, Brazil, for the period May 1990 to April 1991 was evaluated by time series regression, controlling for season, weather, and other factors. Mortality was associated with respirable particles (PM10), nitrogen oxides (NOx), sulfur dioxide (SO2), and carbon monoxide (CO). The association with PM10 was most statistically significant, robust, and independent of other air pollutants. An increase in PM10 equal to 100 micrograms/m3 was associated with an increase in overall mortality equal to approximately 13%. This association was consistent across various model specifications and estimation techniques. The dose-response relationship between mortality and respirable particulate pollution was almost linear, with no evidence of a "safe" threshold level. The results were similar to those observed in London and several U.S. cities. The results were also supportive of recent animal studies that have observed adverse health outcomes in experimental animals exposed to air pollution in Sao Paulo.