Desaturation-Distance Ratio During Submaximal and Maximal Exercise Tests and Its Association With Lung Function Parameters in Patients With Lymphangioleiomyomatosis

A remote monitoring-enabled home exercise prescription for patients with interstitial lung disease at risk for exercise-induced desaturation

RATIONALE

Alternatives to center-based pulmonary rehabilitation are needed to improve patient access to this important therapy. A critical challenge to overcome is how to maximize safety of unsupervised exercise for at-risk patients. We investigated if a novel remote monitoring-enabled mobile health (mHealth) program is safe, feasible, and effective for patients who experience exercise-induced hemoglobin desaturation.

METHODS

An interstitial lung disease (ILD) commonly associated with pronounced exercise desaturation was investigated - the rare, female-predominant ILD lymphangioleiomyomatosis (LAM). Over a 12-week program, hemoglobin saturation (SpO2) was continuously recorded during all home exercise sessions. Intervention effects were assessed with 6-min walk test (6MWT), maximal cardiopulmonary exercise test (CPET), lower extremity computerized dynamometry, pulmonary function tests, and health-related quality of life (QoL) surveys. Safety was assessed by blood biomarkers of systemic inflammation and cardiac wall stress, and incidence of adverse events.

RESULTS

Fifteen LAM patients enrolled and 14 completed the intervention, with high adherence to aerobic (87 ± 15%) and strength (87 ± 12%) training components. An innovative characterization of exercise training SpO2 revealed that while mild-to-moderate desaturation was common during home workouts, participants were able to self-adjust exercise intensity and supplemental oxygen levels to maintain recommended exercise parameters. Significant improvements included 6MWT distance (+36 ± 34 m, p = 0.003), CPET time (p = 0.04), muscular endurance (p = 0.008), QoL (p = 0.009 to 0.03), and fatigue (p = 0.001 to 0.03). Patient acceptability and satisfaction indicators were high, blood biomarkers remained stable (p > 0.05), and no study-related adverse events occurred.

CONCLUSION

A remote monitoring-enabled home exercise program is a safe, feasible, and effective approach even for patients who experience exercise desaturation.

Usefulness of a new parameter in functional assessment in patients with idiopathic pulmonary fibrosis: desaturation - distance ratio from the six-minute walk test

BACKGROUND AND AIM

New parameters in the 6-minute walk test (6MWT) are needed for assessing exercise capacity in patients with idiopathic pulmonary fibrosis (IPF). To our knowledge, no previous study has investigated the potential of using the desaturation distance ratio (DDR) to assess exercise capacity specifically in patients with IPF. This study aimed to investigate whether DDR is a potential tool for assessing the exercise capacity of patients with IPF.

METHODS

This study conducted with 33 subjects with IPF. Pulmonary function tests and a 6MWT were performed. To calculate the DDR, first, the difference between the patient's SpO2 at each minute and the SpO2 of 100% was summed together to determine the desaturation area (DA). Next, DDR was calculated using dividing DA by the 6-minute walk test distance (6MWD) (i.e., DA/6MWD).

RESULTS

When correlations of 6MWD and DDR with changes (Δ) in the severity of perceived dyspnea were examined, 6MWD did not significantly correlate with ΔBorg. Conversely, there was a significant correlation between the DDR and ΔBorg (r= 0.488, p=0.004). There were significant correlations between 6MWD and FVC % (r=0.370, p=0.034), and FEV1 % (r=0.465, p=0.006). However, DDR was significantly more correlated with FVC % (r= -0.621, p< 0.001), FEV1 % (r= -0.648, p< 0.001). Moreover, there was a significant correlation between DDR and DLCO % (r= -0.342, p=0.052).

CONCLUSIONS

The findings of this study suggest that DDR is a promising and more useful parameter for assessing patients with IPF.

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.