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.

Reproducibility, validity, and reliability of the incremental step test for subjects with moderate to severe asthma

OBJECTIVE

We investigated the measurement properties of the incremental step test in subjects with moderate to severe asthma.

METHODS

Subjects with moderate to severe persistent asthma were recruited from a tertiary university hospital specializing in treating severe asthma. All subjects performed one cardiopulmonary exercise test (CPET) and two incremental step tests (IST) in random sequences. Pulmonary gas exchange was measured during all exercise tests. The measurement properties investigated were reliability by intraclass correlation coefficient (ICC), measurement error by the standard error of measurement and minimum detectable difference, construct validity by Pearson's correlation, and interpretability by the ceiling and floor effects.

RESULTS

Fifty subjects (38 females, mean [SD], age 43.7 [11.6] yr, % FEV1 70 [14.3], BMI 28.5 [5.3] kg/m2) completed the study. The peak oxygen uptake (peak VO2) for the CPET was 27.6 [±6.8] ml/kg/min, for the first IST was 22.3 [±5.3] ml/kg/min and for the second IST was 23.3 [±5.3] ml/kg/min. The IST presented excellent reliability (ICC=0.93, CI95% 0.88-0.96), very good measurement error (2.5%), and construct validity for peak VO2 measurement compared to the CPET (r = 0.85; p < 0.001) to assess exercise capacity in subjects with moderate to severe asthma, with appropriate ceiling (10%) and floor (0%) effects.

CONCLUSION

The IST presented excellent reliability and very good measurement error and validity to assess exercise capacity in subjects with moderate to severe asthma, without ceiling or floor effects.

Exercise deactivates leukocytes in asthma

Leukocytes play a central role in asthma physiopathology. Aerobic training (AT) reduces leukocytes recruitment to the airways, but the effects of AT on some aspects of leukocytes activation in asthma are unknown. Therefore, the effects of 4 weeks of AT on airway inflammation, pulmonary and systemic Th2 cytokines levels, leukocytes expression of pro and anti-inflammatory, pro-fibrotic, oxidants and anti-oxidants mediators in an experimental model of asthma was investigated. AT reduced the levels of IL-4, IL-5, IL-13 in bronchoalveolar lavage fluid (BALF) (p<0.001), serum levels of IL-5, while increased BALF and serum levels of IL-10 (p<0.001). In addition, AT reduced leukocytes activation, showed through decreased expression of Th2 cytokines (IL-4, IL-5, IL-13; p<0.001), chemokines (CCL5, CCL10; p<0.001), adhesion molecules (VCAM-1, ICAM-1; p<0.05), reactive oxygen and nitrogen species (GP91phox and 3-nitrotyrosine; p<0.001), inducible nitric oxide synthase (iNOS; p<0.001), nuclear factor kB (NF-kB; p<0.001) while increased the expression of anti-inflammatory cytokine (IL-10; p<0.001). AT also decreased the expression of growth factors (TGF-beta, IGF-1, VEGF and EGFr; p<0.001). We conclude that AT reduces the activation of peribronchial leukocytes in a mouse model of allergic asthma, resulting in decreased airway inflammation and Th2 response.

Creatine activates airway epithelium in asthma

Airway epithelium plays important roles in the pathophysiology of asthma. Creatine supplementation (Cr) was shown to increase asthma features in a murine model of allergic asthma; however, the role of the airway epithelium in this inflammatory response is not known. BALB/c mice were divided into control, creatine supplementation, ovalbumin-sensitized (OVA) and OVA plus creatine supplementation groups. OVA sensitization occurred on days 0, 14, 28 and 42, and ovalbumin challenge from days 21-53. Cr was also given on days 21-53. Total and differential cells counts in BALF were evaluated. Quantitative epithelial expression of interleukin (IL)-4, IL-5, IL-13, CCL11, CCL5, CCL2, iNOS, VCAM-1, ICAM-1, NF-κB, VEGF, TGF-β, IGF-1, EGFR, TIMP-1, TIMP-2, MMP-9, MMP-12 and arginase II were performed. Cr increased the number of total cells and eosinophils in BALF, the epithelial content of goblet cells and the epithelial expression of IL-5, CCL2, iNOS, ICAM-1, NF-κB, TGF-β, TIMP-1 and MMP-9 when compared to the control group (p<0.05). Creatine supplementation also exacerbated goblet cell proliferation, and IL-5 and iNOS expression by epithelial cells compared to the OVA group (p<0.01). Creatine up-regulates the pro-inflammatory cascade and remodelling process in this asthma model by modulating the expression of inflammatory mediators by epithelial cells.

Aerobic training reverses airway inflammation and remodelling in an asthma murine model

Aerobic training (AT) decreases dyspnoea and exercise-induced bronchospasm, and improves aerobic capacity and quality of life; however, the mechanisms for such benefits remain poorly understood. The aim of the present study was to evaluate the AT effects in a chronic model of allergic lung inflammation in mice after the establishment of airway inflammation and remodelling. Mice were divided into the control group, AT group, ovalbumin (OVA) group or OVA+AT group and exposed to saline or OVA. AT was started on day 28 for 60 min five times per week for 4 weeks. Respiratory mechanics, specific immunoglobulin (Ig)E and IgG(1), collagen and elastic fibres deposition, smooth muscle thickness, epithelial mucus, and peribronchial density of eosinophils, CD3+ and CD4+, IL-4, IL-5, IL-13, interferon-gamma, IL-2, IL-1ra, IL-10, nuclear factor (NF)-kappaB and Foxp3 were evaluated. The OVA group showed an increase in IgE and IgG(1), eosinophils, CD3+, CD4+, IL-4, IL-5, IL-13, NF-kappaB, collagen and elastic, mucus synthesis, smooth muscle thickness and lung tissue resistance and elastance. The OVA+AT group demonstrated an increase of IgE and IgG(1), and reduction of eosinophils, CD3+, CD4+, IL-4, IL-5, IL-13, NF-kappaB, airway remodelling, mucus synthesis, smooth muscle thickness and tissue resistance and elastance compared with the OVA group (p<0.05). The OVA+AT group also showed an increase in IL-10 and IL-1ra (p<0.05), independently of Foxp3. AT reversed airway inflammation and remodelling and T-helper cell 2 response, and improved respiratory mechanics. These results seem to occur due to an increase in the expression of IL-10 and IL-1ra and a decrease of NF-kappaB.

Effects of exercise training on atrophy gene expression in skeletal muscle of mice with chronic allergic lung inflammation

We evaluated the effects of chronic allergic airway inflammation and of treadmill training (12 weeks) of low and moderate intensity on muscle fiber cross-sectional area and mRNA levels of atrogin-1 and MuRF1 in the mouse tibialis anterior muscle. Six 4-month-old male BALB/c mice (28.5 +/- 0.8 g) per group were examined: 1) control, non-sensitized and non-trained (C); 2) ovalbumin sensitized (OA, 20 microg per mouse); 3) non-sensitized and trained at 50% maximum speed _ low intensity (PT50%); 4) non-sensitized and trained at 75% maximum speed _ moderate intensity (PT75%); 5) OA-sensitized and trained at 50% (OA+PT50%), 6) OA-sensitized and trained at 75% (OA+PT75%). There was no difference in muscle fiber cross-sectional area among groups and no difference in atrogin-1 and MuRF1 expression between C and OA groups. All exercised groups showed significantly decreased expression of atrogin-1 compared to C (1.01 +/- 0.2-fold): PT50% = 0.71 +/- 0.12-fold; OA+PT50% = 0.74 +/- 0.03-fold; PT75% = 0.71 +/- 0.09-fold; OA+PT75% = 0.74 +/- 0.09-fold. Similarly significant results were obtained regarding MuRF1 gene expression compared to C (1.01 +/- 0.23-fold): PT50% = 0.53 +/- 0.20-fold; OA+PT50% = 0.55 +/- 0.11-fold; PT75% = 0.35 +/- 0.15-fold; OA+PT75% = 0.37 +/- 0.08-fold. A short period of OA did not induce skeletal muscle atrophy in the mouse tibialis anterior muscle and aerobic training at low and moderate intensity negatively regulates the atrophy pathway in skeletal muscle of healthy mice or mice with allergic lung inflammation.

Exercise reduces effects of creatine on lung

We recently demonstrated that creatine supplementation increased some features of lung allergic sensitization in mice. On the other hand, other studies have shown that aerobic exercise inhibited allergic airway inflammation and remodeling. We hypothesized that aerobic exercise may decrease the exacerbatory effects of the creatine supplementation in a murine model of asthma. Balb/c mice were divided into six groups: Control, Creatine (Cr), Low Intensity Exercise+Creatine (Low+Cr), Ovalbumin (OVA), Ovalbumin+Creatine (OVA+Cr) and Ovalbumin+Creatine+Low Intensity Exercise (OVA+Cr+Low). OVA-sensitized groups were sensitized with OVA intraperitoneal injections (days 0, 14, 28, and 42). Aerosol challenge (OVA 1%) and Cr treatment (0.5 g/kg/day) were initiated on Day 21 until Day 53. Low intensity exercise began on day 22 and was sustained until day 50. Low intensity exercise in the presence of creatine supplementation in sensitized mice resulted in a decreased number of eosinophils in BALF (p<0.001) and in the airways (p<0.001), and a decreased density of inflammatory cells positive to IL-4 (p<0.001) and IL-5 (p<0.001), airway collagen (p<0.001) and elastic fibers (p<0.001) content, airway smooth muscle thickness (p<0.001) and bronchoconstriction index (p<0.05) when compared with OVA+Cr group. These results suggest that aerobic exercise reduces the exacerbatory effects of creatine supplementation in chronically sensitized mice.

Physical training leads to remodeling of diaphragm muscle in asthma model

Matrix metalloproteinases (MMPs) are crucial to the development and maintenance of healthy tissue and are mainly involved in extracellular matrix (ECM) remodeling of skeletal muscle. This study evaluated the effects of chronic allergic airway inflammation (CAAI), induced by ovalbumin, and aerobic training in the MMPs activity in mouse diaphragm muscle. Thirty mice were divided into 6 groups: 1) control; 2) ovalbumin; 3) treadmill trained at 50% of maximum speed; 4) ovalbumin and trained at 50%; 5) trained at 75%; 6) ovalbumin and trained at 75%. CAAI did not alter MMPs activities in diaphragm muscle. Nevertheless, both treadmill aerobic trainings, associated with CAAI increased the MMP-2 and -1 activities. Furthermore, MMP-9 was not detected in any group. Together, these findings suggest an ECM remodeling in diaphragm muscle of asthmatic mice submitted to physical training. This result may be useful for a better understanding of functional significance of changes in the MMPs activity in response to physical training in asthma.

Influence of diaphragmatic mobility on exercise tolerance and dyspnea in patients with COPD

BACKGROUND

Patients with chronic obstructive pulmonary disease (COPD) present increased airway resistance, air trapping, pulmonary hyperinflation, and diaphragm muscle alterations, all of which affect pulmonary mechanics.

PURPOSE

To evaluate the influence diaphragmatic mobility has on exercise tolerance and dyspnea in patients with COPD.

MATERIALS AND METHODS

Fifty-four COPD patients with lung hyperinflation were evaluated to assess pulmonary function, diaphragm mobility, exercise tolerance, and dyspnea (score). Twenty healthy (age- and body mass index-matched) subjects were evaluated as controls.

RESULTS

The COPD patients presented lower diaphragmatic mobility than did the controls (36.27+/-10.96 mm vs. 46.33+/-9.46 mm). Diaphragmatic mobility presented a linear correlation with distance covered on the 6-min walk test (6MWT) (r=0.38; p=0.005) and a negative correlation with dyspnea (r=-0.36; p=0.007). Patients were then divided into two subgroups based on the degree of diaphragmatic mobility: G1 (<or=33.99 mm) and G2 (>or=34 mm). Those in G1 presented poorer 6MWT performance and greater dyspnea upon exertion than did those in G2 (distance covered on the 6MWT: 454.76+/-100.67 m vs. 521.63+/-70.82 m; dyspnea score: 5.22+/-3.06 vs. 3.48+/-2.77). The G1 patients also presented greater residual volume (in liters) and lower maximal voluntary ventilation (in % of predicted values) than did the G2 patients (266.20+/-55.30 vs. 209.74+/-48.49 and 39.00+/-14.94 vs. 58.11+/-20.96).

CONCLUSION

Diaphragmatic mobility influences dyspnea and exercise tolerance in patients with COPD.

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.