Continuous measurements of respiratory muscle blood flow & oxygen consumption using non-invasive FD-NIRS & DCS.

Prior studies of muscle blood flow and muscle specific oxygen consumption have required invasive injection of dye and Magnetic Resonance Imaging, respectively. Such measures have limited utility for continuous monitoring of the respiratory muscles. Frequency domain near-infrared spectroscopy and diffuse correlation spectroscopy (FD-NIRS & DCS) can provide continuous surrogate measures of blood flow index (BFi) and metabolic rate of oxygen consumption (MRO2). This study aimed to validate sternocleidomastoid FD-NIRS & DCS outcomes against electromyography (EMG) and mouth pressure (Pm) during incremental inspiratory threshold loading (ITL). Six females and six male healthy adults (mean±SD; 30±7 years, maximum inspiratory pressure 118±61 cmH2O) performed incremental ITL starting at low loads (8±2 cmH2O) followed by 50g increments every two minutes until task failure. FD-NIRS & DCS continuously measured sternocleidomastoid oxygenated and deoxygenated hemoglobin+myoglobin (oxy/deoxy[Hb+Mb]), tissue saturation of oxygen (StO2), BFi, and MRO2. Ventilatory parameters including inspiratory Pm were also evaluated. Pm increased during incremental ITL (P<0.05), reaching -47[-74 - -34] cmH2O (median[25%-75%IQR] at task failure. Ventilatory parameters were constant throughout ITL (all P>0.05). Sternocleidomastoid BFi and MRO2 increased from the start of the ITL (both P<0.05). Deoxy[Hb+Mb] increased close to task failure, concomitantly with a constant increase in MRO2, and decreased StO2. Sternocleidomastoid deoxy[Hb+Mb], BFi, StO2 and MRO2 obtained during ITL via FD-NIRS & DCS correlated with sternocleidomastoid EMG (all P<0.05). In healthy adults, FD-NIRS & DCS can provide continuous surrogate measures of respiratory BFi and MRO-2. Increasing sternocleidomastoid oxygen consumption near task failure was associated with increased oxygen extraction and reduced tissue saturation.

Physical activity in idiopathic pulmonary fibrosis: Longitudinal change and minimal clinically important difference.

BACKGROUND AND OBJECTIVE: Reference values of physical activity to interpret longitudinal changes are not available in patients with idiopathic pulmonary fibrosis (IPF). This study aimed to define the minimal clinical important difference (MCID) of longitudinal changes in physical activity in patients with IPF. METHODS: Using accelerometry, physical activity (steps per day) was measured and compared at baseline and 6-months follow-up in patients with IPF. We calculated MCID of daily step count using multiple anchor-based and distribution-based methods. Forced vital capacity and 6-minute walk distance were applied as anchors in anchor-based methods. Effect size and standard error of measurement were used to calculate MCID in distribution-based methods. RESULTS: One-hundred and five patients were enrolled in the study (mean age: 68.5 ± 7.5 years). Step count significantly decreased from baseline to 6-months follow-up (-461 ± 2402, p = .031). MCID calculated by anchor-based and distribution-based methods ranged from 570-1358 steps. CONCLUSION: Daily step count significantly declined over 6-months in patients with IPF. MCID calculated by multiple anchor-based and distribution-based methods was 570 to 1358 steps/day. These findings contribute to interpretation of the longitudinal changes of physical activity that will assist its use as a clinical and research outcome in patients with IPF.

Differences in Characteristics Between Physical Frailty Assessments in Chronic Obstructive Pulmonary Disease: A Multicenter Cross-Sectional Observational Study.

Purpose: Assessment for frailty is important as it enables timely intervention to prevent or delay poor prognosis in chronic obstructive pulmonary disease (COPD). The aims of this study, in a sample of outpatients with COPD, were to (i) assess the prevalence of physical frailty using the Japanese version of the Cardiovascular Health Study (J-CHS) criteria and the Short Physical Performance Battery (SPPB) and the degree of agreement between the findings of the two assessments and (ii) identify factors associated with the disparity in the results obtained with these instruments. Patients and Methods: This was a multicenter cross-sectional study of individuals with stable COPD enrolled in four institutions. Frailty was assessed using the J-CHS criteria and the SPPB. Weighted Cohen's kappa (k) statistic was performed to investigate the magnitude of agreement between the instruments. We divided participants into two groups depending on whether there was agreement or non-agreement between the results of the two frailty assessments. The two groups were then compared with respect to their clinical data. Results: A total of 103 participants (81 male) were included in the analysis. The median age and FEV1 (%predicted) were 77 years and 62%, respectively. The prevalence of frailty and pre-frail was 21% and 56% with the J-CHS criteria and 10% and 17% with the SPPB. The degree of agreement was fair (k = 0.36 [95% CI: 0.22-0.50], P<0.001). There were no significant differences in the clinical characteristics between the agreement group (n = 44) and the non-agreement group (n = 59). Conclusion: We showed that the degree of agreement was fair with the J-CHS criteria detecting a higher prevalence than the SPPB. Our findings suggest that the J-CHS criteria may be useful in people with COPD with the aim of providing interventions to reverse frailty in the early stages.

Cutoff Points for Step Count to Predict 1-year All-Cause Mortality in Patients with Idiopathic Pulmonary Fibrosis.

BACKGROUND: Although physical activity is associated with mortality in patients with idiopathic pulmonary fibrosis (IPF), reference values to interpret levels of physical activity are lacking. OBJECTIVES: This study aimed to investigate the prognostic significance of physical activity assessed by step count and its cutoff points for all-cause mortality. METHODS: We measured physical activity (steps per day) using an accelerometer in patients with IPF at the time of diagnosis. Relationships among physical activity and mortality, as well as cutoff points of daily step count to predict all-cause mortality were examined. RESULTS: Eighty-seven patients (73 males) were enrolled. Forty-four patients (50.1%) died during the follow-up (median 54 months). In analysis adjusting for Gender-Age-Physiology stage and 6-min walk distance, daily step count was an independent predictor of all-cause mortality (hazard ratio (HR) = 0.820, 95% confidence interval (CI) = 0.694-0.968, p = 0.019). The optimal cutoff point (receiving operating characteristic analysis) for 1-year mortality was 3,473 steps per day (sensitivity = 0.818 and specificity = 0.724). Mortality was significantly lower in patients with a daily step count exceeding 3,473 steps than in those whose count was 3,473 or less (HR = 0.395, 95% CI = 0.218-0.715, p = 0.002). CONCLUSIONS: Step count, an easily interpretable measurement, was a significant predictor of all-cause mortality in patients with IPF. At the time of diagnosis, a count that exceeded the cutoff point of 3,473 steps/day more than halved mortality. These findings highlight the importance of assessing physical activity in this patient population.

Respiratory Impairment, Limited Activity, and Pulmonary Rehabilitation in Patients with Interstitial Lung Disease.

Interstitial lung disease (ILD) is a diverse group of chronic lung conditions characterized by dyspnea, exercise-induced hypoxemia (EIH), and exercise intolerance. Since activity limitations and impaired health-related quality of life (HRQoL) in ILD are similar to those in other chronic respiratory diseases, including chronic obstructive pulmonary disease (COPD), pulmonary rehabilitation is also indicated for patients with ILD. This rehabilitation program mainly comprises exercise training and self-management education. Exercise training is the most important component of pulmonary rehabilitation. It significantly improves dyspnea and enhances exercise capacity and HRQoL in patients with ILD. The standard exercise prescription used for COPD is also effective for ILD. However, considering that disease progression and exercise-limiting factors are different in patients with COPD is necessary. Severe EIH, the adverse effects of corticosteroid administration, and comorbidities often lead to difficulty in employing a sufficient exercise intensity. Some modifications in the exercise prescription for individual patients or strategies to minimize EIH and dyspnea are required to optimize training intensity. Since EIH is common and severe in patients with ILD, supplemental oxygen should be provided. In advanced and more severe patients, who have difficulty in performing exercises, energy conservation techniques and the use of energy-saving devices to improve and maintain the patients' activities of daily living may be effective．.

Distractive Auditory Stimuli Alleviate the Perception of Dyspnea Induced by Low-Intensity Exercise in Elderly Subjects With COPD.

BACKGROUND: Although recent studies have shown that distractive auditory stimuli (DAS) in the form of music increase adherence to exercise in subjects with COPD, the effect of DAS on dyspnea induced by low-intensity, constant-load exercise in elderly patients with COPD has not been elucidated. Therefore, the purpose of this study was to investigate the effect of DAS on the perception of dyspnea induced by low-intensity, constant-load exercise in elderly subjects with COPD. METHODS: We enrolled 16 male out-patients with COPD. Subjects completed cycling exercises with and without DAS at 40% maximum oxygen consumption. They were asked to rate their perception of dyspnea using the modified Borg scale every 3 min during exercise and every 1 min during the recovery period. RESULTS: Dyspnea perception during low-intensity exercise showed a significant correlation between the exercise condition (DAS and control) and exercise duration (P = .04). Exercise-induced dyspnea perception under the DAS condition was significantly lower than that under the control condition from 18 min after the start of exercise to 3 min after the end of exercise (18, 20, 21, 22, and 23 min, P = .01, P < .001, P = .009, P = .006, and P = .006, respectively). However, oxygen consumption and ventilation in response to low-intensity exercise did not significantly differ in the DAS and control conditions (P = .39 and .14, respectively) CONCLUSIONS: Our results suggest that DAS is a non-pharmacologic therapy that can be used to reduce the dyspneic sensation in elderly patients with COPD.

Effect of Dyspnea Induced by Breath-holding on Maximal Muscular Strength of Patients with COPD.

[Purpose] The purpose of the present study was to clarify the effect of dyspnea induced by breath-holding on maximum muscular strength of patients with COPD. [Subjects] This study recruited 14 COPD subjects via public posting. [Methods] Dyspnea was assessed by the modified Borg scale. The subject asked to stop breathing at end-expiration and to hold their breath with a nose clip for as long as possible. Both total breath-holding time and threshold time of dyspnea were measured with a chronograph. Dyspnea reserve time (DRT) was defined by subtracting the threshold time of perception dyspnea from total breath-holding time in order to calculate the 50% DRT. The muscular strengths of maximal handgrip contraction were measured at baseline, 50% threshold time of dyspnea (subliminal point of dyspnea), and the 50% DRT (supraliminal point of dyspnea). [Results] The maximal handgrip at the supraliminal point of dyspnea was significantly lower than the baseline and subliminal point of dyspnea values. There was no statistically significant difference in maximal muscular strength between baseline and the subliminal point of dyspnea value. [Conclusion] The present results demonstrate that dyspnea induced by breath-holding aggravates weakness in the maximum muscular strength of patients with COPD.