Krebs von den Lungen-6 levels at admission predicts exercise-induced hypoxemia before and after discharge in patients with COVID-19.

BACKGROUND: There are no reports of exercise-induced hypoxemia in patients with coronavirus disease 2019 (COVID-19). Additionally, the predictive factors and prevalence of exercise-induced hypoxemia are unknown. This study investigated the incidence and predictive factors of exercise-induced hypoxemia before and after discharge in patients with COVID-19. METHODS: We enrolled 77 patients diagnosed with COVID-19 who were hospitalized between November 2020 and October 2021 and who underwent a 6-min walk test before and after discharge. Based on the test results, we classified patients into exercise-induced and non-exercise-induced hypoxemia groups and investigated the predictive factors of exercise-induced hypoxemia using logistic regression analysis. RESULTS: The incidences of exercise-induced hypoxemia in patients with COVID-19 were 37.7% and 19.5% before and after discharge, respectively. At admission, the Krebs von den Lungen-6 levels was the associated factor for exercise-induced hypoxemia in patients with COVID-19 before and after discharge, with cut-off values of 314 U/mL and 367 U/mL, respectively. Age and lactate dehydrogenase levels were the associated factors for exercise-induced hypoxemia in patients with COVID-19 before discharge, with cut-off values of 61 years and 492 U/L, respectively. CONCLUSIONS: Some patients with COVID-19 may continue to experience exercise-induced hypoxemia after discharge. Age, lactate dehydrogenase, and Krebs von den Lungen-6 levels at admission could serve as predictive markers of exercise-induced hypoxemia before and after discharge in these patients.

Effects of Pedometer-Based Step-Feedback on Physical Activity of Severe COPD Patients.

Purpose: This study investigated whether adding step-feedback (step-FB) from a pedometer to pulmonary rehabilitation (PR) programs could increase the physical activity (PA) of low-activity patients with severe chronic obstructive pulmonary disease (COPD). Patients and Methods: We included low-activity patients with severe COPD (step-FB group: 14 patients; control group: 17 patients) who underwent PR for the first time. The usual PR program for patients with severe COPD consisted of two 8-week sessions (PR session 1: PR1, PR session 2: PR2). The step-FB group was provided a program with step-FB added to PR2 (PR2+step-FB). Furthermore, all patients were evaluated at pre-intervention (baseline), PR1, and PR2. The primary outcome of this study was the number of daily steps (steps) and energy expenditure from activity (energy expenditure), as measured by a pedometer. The secondary outcomes were dyspnea and exercise tolerance. Results: In PR1, dyspnea, exercise tolerance, steps, and energy expenditure were significantly improved as compared to baseline, in both groups. During PR2, dyspnea and exercise tolerance were significantly improved as compared to PR1, in both groups. Steps and energy expenditure were significantly improved in the step-FB group, but not in the control group. Conclusion: PR improved PA by improving physical function in severe COPD patients. Adding step-FB improved PA in severe COPD patients by presenting an activity goal for improving PA. Therefore, pedometer-based step-FB is a viable addition to PR and has the potential to improve PA continuously in these patients.

Characteristics of Older Patients with Heart Failure Readmitted due to Acute Exacerbations within the Past Year.

OBJECTIVE: We aimed to examine the relationship between physical performance and readmission among older patients with heart failure (HF) over the past year. METHODS: This retrospective cohort study included 325 patients with HF who were aged ≥65 years and were hospitalized for acute exacerbation between November 2017 and December 2021. We investigated age, sex, body mass index, length of hospital stay, initiation of rehabilitation, New York Heart Association (NYHA) class, Charlson comorbidity index (CCI) score, medications, cardiac/renal function, nutrition, maximal quadriceps isometric strength, grip strength, and Short Physical Performance Battery (SPPB) score. Data were analyzed using the χ2 test, Mann-Whitney U test, and logistic regression analysis. RESULTS: Altogether, 108 patients met the inclusion criteria and were divided into the non-readmission (n = 76) and readmission (n = 32) groups. The readmission group exhibited longer hospital stay, more severe NYHA class, higher CCI score, higher brain natriuretic peptide (BNP) levels, lower muscle strength, and lower SPPB score compared to the non-readmission group. In the logistic regression model, BNP level and SPPB score were independent factors associated with readmission. CONCLUSION: BNP level and SPPB score were associated with readmission in patients with HF within the past year.

Brain natriuretic peptide levels and short physical performance battery scores independently influence short-term readmission rates in older patients with heart failure.

The Short Physical Performance Battery (SPPB) is a well-established tool to assess the lower extremity physical performance status. The purpose of this study is to examine the impact of brain natriuretic peptide (BNP) levels and SPPB scores on short-term readmission in older patients with heart failure (HF). This prospective cohort study enrolled 325 patients with HF who were hospitalized for acute decompensated HF between November 2017 and December 2021. Variables were analyzed using the Cox proportional hazards model, receiver operating characteristic (ROC) curve, and Kaplan-Meier analysis. The 107 patients who met the inclusion criteria were divided into readmission (within 90 days of discharge; n = 25) and non-readmission (n = 82) groups. Multivariate analysis revealed that BNP level and SPPB score were independent risk factors for readmission within 90 days after discharge. Patients were classified into three groups according to the BNP and SPPB cutoff values calculated using ROC curves. The risk of readmission was significantly higher in Group 3 (BNP ≥ 384 pg/mL and SPPB ≤ 7 points) than in Group 1 (BNP < 384 pg/mL and SPPB > 7 points; hazard ratio: 27.68, 95% confidence interval: 3.672 - 208.700, P = 0.0012). Our study showed that HF patients with high BNP levels and low SPPB scores have a dramatically increased risk of readmission within 90 days of discharge.

Effect of cognitive impairment at admission on activities of daily living at discharge in older patients with heart failure.

Nonaka Y, Fujii R, Tanaka S, Tabira K. Effect of cognitive impairment at admission on activities of daily living at discharge in older patients with heart failure. Jpn J Compr Rehabil Sci 2023; 14: 78‒83. Objective: Hasegawa's Dementia Scale-Revised (HDS-R) is widely used as a screening test for cognitive function in older adults. In this study, we examined the effect of cognitive impairment (CI) at admission on activities of daily living (ADL) at discharge in older patients with heart failure (HF). Methods: This retrospective observational study included 394 patients hospitalized for acute decompensated HF between April 2016 and December 2022. Data on age, sex, body mass index, length of hospital stay, initiation of rehabilitation, New York Heart Association (NYHA) class, Charlson Comorbidity Index, medication, brain natriuretic peptide levels, left ventricular ejection fraction, renal function, hemoglobin level, serum albumin level, Geriatric Nutritional Risk Index (GNRI), Barthel Index (BI), and HDS-R score were analyzed using the χ2 test, unpaired t test, Mann-Whitney U test, and multiple linear regression. Results: Among 394 patients, 102 who met the final inclusion criteria were included in the study. Based on previous studies, patients were divided into a high BI group (N = 44) and a low BI group (N = 58). Multiple linear regression analysis showed that CI at admission independently affected BI at discharge even after adjusting for confounding effects of age, NYHA class, GNRI, and BI at admission. Conclusions: Our study showed that the presence or absence of CI may influence ADL improvement in rehabilitation interventions aimed at improving ADL in older patients with HF.

Impact of inspiratory muscle strength on exercise capacity after lung transplantation.

BACKGROUND AND PURPOSE: Though inspiratory muscle strength is essential for patients with respiratory disease, it is unclear whether the recovery of inspiratory muscle strength contributes to an exemplary achievement of exercise tolerance after lung transplantation (LTx). We aimed to elucidate the inspiratory muscle strength affects the recovery of exercise capacity after LTx. METHODS: Recipients who underwent LTx between June 2017 and September 2018 were enrolled, and 6-min walking distance (6MWD), quadriceps force, inspiratory muscle strength (maximal inspiratory pressure [MIP]), and spirometry were evaluated at 3, 6, and 12 months after LTx. The relationships between inspiratory muscle strength and changes in physical performance were analyzed. RESULTS: Nineteen recipients (mean age: 44.8 years, male: 32%) who completed all follow-ups were analyzed. At 3 months after LTx, mean MIP (88.4% predicted) and vital capacity (60.9% predicted), quadriceps force (QF; 2.1 N*m/kg), and 6MWD (504 m) were lower than normal values. After LTx, 6MWD significantly improved up to 12 months. From 3 to 6 months after LTx, changes in MIP were significantly associated with increases in 6MWD by univariate (r = 0.55, p = 0.02) and multivariate (ß = 0.59, p = 0.01) regression analyses, whereas changes of QF in place of MIP were significantly associated with the recoveries of 6MWD from 6 to 12 months. DISCUSSION: Improvements in MIP may impact the recovery of exercise capacity in the early phase after LTx. Factors that determine the improvement in exercise capacity following LTx may vary with postoperative time.

Relationship between kyphosis and cough strength and respiratory function of community-dwelling elderly.

BACKGROUND: Kyphosis may reduce the force of coughing by affecting the factors related to cough peak flow (CPF). This study sought to compare cough strength and respiratory function between non-kyphotic and kyphotic elderly individuals and clarify the relationship between these factors. METHODS: The non-kyphotic group comprised 17 elderly individuals with a kyphosis index of less than 15.1, while the kyphotic group comprised 21 elderly individuals with a kyphosis index of 15.1 or higher. Cough strength, respiratory function, respiratory muscle strength, and maximum phonation time were measured, and comparison between two groups and correlation analysis between variables were performed. RESULTS: CPF, vital capacity, maximum expiratory pressure (PEmax), maximum inspiratory pressure (PImax), and chest expansion at the xiphoid process were significantly lower in the kyphotic group than in the non-kyphotic group. There were significant negative correlations between kyphosis index and CPF (r = -0.37, p < 0.05), PEmax (r = -0.45, p < 0.01), PImax (r = -0.44, p < 0.01) and chest expansion at the xiphoid process (r = -0.38, p < 0.05). CONCLUSIONS: Our results demonstrated that cough strength was significantly lower in the kyphotic compared to non-kyphotic individuals. Furthermore, cough strength decreased with increased severity of kyphosis.

Chest physical therapy reduces pneumonia following inhalation injury.

PURPOSE: The purpose of this study was to clarify the efficacy of chest physiotherapy (CPT) in patients with inhalation injury in the acute phase. PATIENTS AND METHODS: This was a single-institution retrospective study of patients with inhalation injury admitted to the Chukyo Hospital Burn Center from April 2004 to March 2014 who required endotracheal intubation for respiratory care. The patients were divided into two groups: the CPT group and the conventional physical therapy group. We compared the two groups according to the incidence of pneumonia, length of ICU/hospital stay, and level of activities of daily living at discharge. To match subject backgrounds, we conducted a propensity score matching analysis, and using a Cox regression analysis, we evaluated the effect of CPT on the first pneumonia event. RESULTS: Of 271 patients admitted to the burn center, 139 patients were included. The incidence of pneumonia in the CPT group was significantly lower and these patients required fewer days until they could sit on the edge of the bed compared with the conventional physical therapy group. In a Cox regression model, the hazard ratio for the first incidence of pneumonia in the CPT group vs. the conventional therapy group was 0.27 (95% confidence interval: 0.13-0.54, P = 0.0002) after propensity score matching. CONCLUSIONS: CPT reduces the incidence of pneumonia and facilitates patient mobilization following inhalation injury.

Effect of pulmonary rehabilitation with assistive use of short-acting ß2 agonist in COPD patients using long-acting bronchodilators.

Background: Assistive use of short-acting ß2 agonists (SABAs) reportedly improves exercise tolerance, activities of daily living, and health-related quality of life (HRQOL) in patients with chronic obstructive pulmonary disease (COPD). However, the effect of SABA on physical activity (PA) is unclear.Objective: This study aimed to determine whether assistive use of SABA increases PA and whether additional pulmonary rehabilitation (PR) can aid further improvement.Methods: Twelve outpatients with COPD and dyspnea during daily activities despite regular use of long-acting bronchodilators were enrolled. This study comprised a 2-week pre-intervention investigation, a 12-week investigation of SABA effects, and an 8-week investigation of the additional effects of PR. Assistive use of SABA was allowed up to 4 times per day after the pre-intervention period. PA was measured for 14 consecutive days using an accelerometer sensor. Dyspnea, exercise tolerance, and HRQOL were evaluated at entry, at 4 and 12 weeks after initiating SABA use, and after completing PR.Results: Assistive use of SABA improved breathlessness during daily activities and increased PA (p < .001). PA and HRQOL were also improved following PR (p < .001 and p = .013, respectively).Conclusions: Combined therapy of SABA and PR can increase PA and HRQOL in COPD patients.

A Prediction Equation to Assess Resting Energy Expenditure in Japanese Patients with COPD.

BACKGROUND: Medical nutrition therapy is important in the management of chronic obstructive pulmonary disease (COPD) patients. Determination of resting energy expenditure is essential to define therapeutic goals for medical nutrition. Previous studies proposed the use of equations to predict resting energy expenditure. No prediction equation is currently available for the Japanese population. The objective of this study was to develop an equation to predict resting energy expenditure in Japanese chronic obstructive pulmonary disease patients. To this end, we investigated clinical variables that correlate with the resting energy expenditure. METHODS: This study included 102 COPD patients admitted at the Matsusaka Municipal Hospital Respiratory Center. We measured resting energy expenditure by indirect calorimetry and explored the relationship of resting energy expenditure with clinical variables by univariate and stepwise linear regression analysis. RESULTS: The resting energy expenditure by indirect calorimetry was significantly correlated with fat-free mass, body weight, body mass index, height, gender, and pulmonary function test by univariate analysis. In the stepwise linear regression analysis, the fat-free mass, body weight, and age remained significantly correlated with indirect calorimetry's resting energy expenditure. The fat-free mass, body weight, and age explained 50.5% of the resting energy expenditure variation. CONCLUSION: Fat-free mass, body weight, and age were significantly correlated with resting energy expenditure by stepwise linear regression analysis, and they were used to define a predictive equation for Japanese COPD patients.

Comparison of respiratory muscle strength in individuals performing continuous and noncontinuous walking exercises in water after the 6-week program.

This study aimed to compare respiratory muscle strength in individuals performing continuous and noncontinuous walking exercises in water after the 6-week program. Twenty-nine healthy men were randomly divided into a continuous group (CG, n=14) and a noncontinuous group (NG, n=15). Firstly, both groups executed the 6-week program which set them to walk for 30 min, 4 times per week, over 6 weeks in a pool with the adjusted intensity that their walking speed increased the heart rate to 60% of the predicted maximum. After the 6-week program, participants in the CG continued the water-walking program for 4 weeks while those in the NG discontinued the water-walking program. In both groups, respiratory muscle strength evaluated by maximum inspiratory pressure (PImax) and maximum expiratory pressure (PEmax) increased significantly after the 6-week program compared with pre-exercise value. Compared to the value after the 6-week program, PEmax increased significantly in the CG after 10 weeks (P<0.05), but the PImax showed no significant change. Compared to the value after the 6-week program, after 10 weeks, in the NG, PEmax decreased significantly, with a considerable decrease after 9 and 10 weeks compared to the CG (P<0.05). The PImax in the NG significantly decreased after 10 weeks from the value observed after the 6-week program. We demonstrated that 6 weeks of walking in water at 60% of the predicted maximum heart rate enhances PImax and PEmax, and that PImax and PEmax decrease in 4 weeks without a water-walking program.

Factors influencing the physical activity in daily life of male patients with different levels of severity of chronic obstructive pulmonary disease.

[Purpose] Physical activity influences the prognosis of chronic obstructive pulmonary disease and is influenced by exercise tolerance, and environmental, psychological, and many other factors, but the influence of these factors on physical activity levels in each stage of chronic obstructive pulmonary disease is unknown. This study aimed to clarify this matter. [Participants and Methods] Seventy-one male patients with chronic obstructive pulmonary disease (aged 72.2 ± 4.5 years) participated in this study. We compared physical activity levels (determined as daily steps), presence or absence of daily routine (e.g., housework or hobby), 6-minute walking distance, psychological factors (using the Hospital Anxiety and Depression Scale), and health-related quality of life (Physical and Mental component summary of the 36-item short-form health survey) between patients in different stages of chronic obstructive pulmonary disease. [Results] When examined at each stage of chronic obstructive pulmonary disease, physical activity levels correlated with the presence or absence of daily routine, 6-minute walking distance, and Physical component summary in all stages, but the scores in the anxiety and depression components of the Hospital Anxiety and Depression Scale and Mental component summary correlated only with stage 4. [Conclusion] Physical functioning was related to physical activity levels at any stage of chronic obstructive pulmonary disease, although psychological functioning was related to the progress of disease severity. The approach to promote an active lifestyle must be selected depending on the stage of chronic obstructive pulmonary disease.

Pulmonary rehabilitation in patients with idiopathic pulmonary fibrosis: comparison with chronic obstructive pulmonary disease.

Background: While the efficacy of pulmonary rehabilitation (PR) in chronic obstructive pulmonary disease (COPD) has been well established, emerging evidence also suggests its benefit in idiopathic pulmonary fibrosis (IPF). However, the differences and similarities between how PR affects diseases with different physiologies remain unknown. Objective: This study aimed to compare the efficacy of PR in COPD and IPF patients by performing multifactorial evaluation with various exercise capacity measurements, and dyspnea and health-related quality of life (QoL) assessment. Methods: Twenty-two IPF patients (%vital capacity: 72%) and 27 COPD patients (%forced expiratory volume1: 43%) were recruited. Subjects who completed a 10-week outpatient PR program were analyzed. We assessed five exercise capacity indicators (6-minute walking distance, incremental shuttle walking distance, endurance time, peak work rate, and peak values for oxygen uptake [peak VO2]), dyspnea (Baseline Dyspnea Index: BDI), and health-related QoL (St. George's Respiratory Questionnaire: SGRQ) at baseline and immediately following completion of the PR program. Results: After 10 weeks of PR, all exercise capacity measurements, except VO2, as well as BDI and SGRQ score improved significantly (p<0.05) in both disease groups. The magnitude of the observed changes in each outcome, assessed by the effect size, was comparable between IPF and COPD patients. This was also true for endurance time, the measurement most responsive to PR, with a large effect size. Conclusions: PR can result in comparable improvements in exercise capacity, including endurance time, and dyspnea and HRQoL in both IPF and COPD patients after 10 weeks of exercise training. (Sarcoidosis Vasc Diffuse Lung Dis 2017; 34: 283-289).

Difference in Physiological Components of VO2 Max During Incremental and Constant Exercise Protocols for the Cardiopulmonary Exercise Test.

[Purpose] VO2 is expressed as the product of cardiac output and O2 extraction by the Fick equation. During the incremental exercise test and constant high-intensity exercise test, VO2 results in the attainment of maximal O2 uptake at exhaustion. However, the differences in the physiological components, cardiac output and muscle O2 extraction, have not been fully elucidated. We tested the hypothesis that constant exercise would result in higher O2 extraction than incremental exercise at exhaustion. [Subjects] Twenty-five subjects performed incremental exercise and constant exercise at 80% of their peak work rate. [Methods] Ventilatory, cardiovascular, and muscle oxygenation responses were measured using a gas analyzer, Finapres, and near-infrared spectroscopy, respectively. [Results] VO2 was not significantly different between the incremental exercise and constant exercise. However, cardiac output and muscle O2 saturation were significantly lower for the constant exercise than the incremental exercise at the end of exercise. [Conclusion] These findings indicate that if both tests produce a similar VO2 value, the VO2 in incremental exercise would have a higher ratio of cardiac output than constant exercise, and VO2 in constant exercise would have a higher ratio of O2 extraction than incremental exercise at the end of exercise.

Effect of modulated-frequency and modulated-intensity transcutaneous electrical nerve stimulation after abdominal surgery: a randomized controlled trial.

PURPOSE: This study aimed to evaluate the effectiveness of transcutaneous electrical nerve stimulation (TENS) for treatment of postoperative pain and pulmonary functions (vital capacity [VC]; cough peak flow, [CPF]) in patients who underwent abdominal surgery. MATERIALS AND METHODS: Forty-eight patients were randomly allocated to receive TENS, placebo TENS, or no TENS (control) 1 hour a day for 3 days postoperatively. A 0-100 visual analog scale was used to assess pain at preintervention, mid-intervention, and postintervention on the third postoperative day. Pulmonary functions (VC, CPF) were evaluated by spirometer at preoperation (baseline) and at preintervention, mid-intervention, and postintervention on the third postoperative day. One-way analysis of variance was used to assess differences between groups at baseline. Mann-Whitney test was used to compare the control group with the placebo-TENS and TENS group, at each assessment timepoint. Two-way analysis of variance and Bonferroni post hoc test assessed the difference between the 2 (placebo-TENS×TENS) groups. A value of P<0.01 was considered statistically significant. RESULTS: The baselines were not significantly different between any groups. The TENS group had significant reductions in postoperative pain compared with the placebo group (P<0.01) and control group (P<0.01). There was also improvement in pulmonary functions (VC, CPF) at mid-TENS and post-TENS, but not in the placebo-TENS (P<0.01) or control groups (P<0.01). CONCLUSIONS: TENS is a valuable treatment to alleviate postoperative pain and improve pulmonary functions (ie, VC, CPF) in patients following abdominal surgery.

Muscle oxygen extraction is higher during constant work exercise than during incremental ramp exercise.

A cardiopulmonary exercise test (CPX) can provide objective measures of exercise capacity. Specifically, incremental ramp exercise (IRE) and constant work-rate exercise (CWE) protocols are frequently used in clinical practice and for research. The CWE endurance time has shown larger increases than other indexes assessed by IRE after rehabilitation intervention. Muscle oxygen extraction is one of the important physiological factors of exercise capacity; however, the differences in muscle oxygen kinetics between IRE and CWE remain unclear. The purpose of this study was to compare the muscle oxygen kinetics during IRE and CWE. Each of the 15 participants performed IRE and CWE to exhaustion on a cycle ergometer. Ventilatory and muscle deoxygenation responses were measured during the tests; muscle deoxygenation was determined using near-infrared spectroscopy. No differences in oxygen uptake and heart rate were observed between the two tests. A comparison of the muscle deoxygenation kinetics between the two tests indicated significantly greater deoxygenation during the CWE than during the IRE at all time points (p < 0.05). The muscle deoxygenation kinetics, as percentages of maximal oxygen uptake (VO2max), were higher during CWE than during IRE, except at 80% of VO2max (p < 0.05). These results suggest that skeletal muscle during CWE extracts oxygen at a rate comparable to that during IRE, and that exercise capacity assessed using CWE might be linked to a higher overall O2 extraction. The fact that endurance time during CWE is more sensitive to rehabilitation intervention may be due to improvements in muscle oxygen extraction.

Endurance time is the most responsive exercise measurement in idiopathic pulmonary fibrosis.

BACKGROUND: Although pulmonary rehabilitation (PR) has been reported to improve exercise capacity in patients with idiopathic pulmonary fibrosis, it is unknown which exercise measurement is the most responsive for evaluation of PR efficacy. The purpose of this study was to compare the responsiveness of 5 exercise measurements by evaluating the efficacy of PR in subjects with idiopathic pulmonary fibrosis. METHODS: We conducted a prospective observational study in which 53 subjects with idiopathic pulmonary fibrosis were enrolled. The PR group underwent a 10-week out-patient PR program. The control group was observed without any additional intervention, including PR. Five exercise measurements (endurance time [ET], peak work rate, peak oxygen consumption [V̇O2 ], 6-min walk distance, and incremental shuttle walk distance) were evaluated at baseline and after 10 weeks. The effect size was used for the assessment of responsiveness. RESULTS: In each group, 24 subjects completed the 5 measurements at baseline and after 10 weeks. The changes in ET (PR: 181.6%; control: -8.2%), peak V̇O2 (PR: 7.6%; control: -5.4%), peak work rate (PR: 15.1%; control: -5.1%), 6-min walk distance (PR: 6.0%; control: -3.8%), and incremental shuttle walk distance (PR: 9.1%; control: -5.1%) were significantly different between the groups after 10 weeks (P < .05). In the PR group, ET showed the most striking improvement among the 5 measurements (P < .05), and its effect size was as large as 2.96, whereas those of the others were all < 0.5. CONCLUSIONS: ET is the most responsive exercise measurement for evaluating PR efficacy in patients with idiopathic pulmonary fibrosis.

Changes in sympathetic nervous system activity in male smokers after moderate-intensity exercise.

OBJECTIVE: To investigate the effects of moderate-intensity exercise on the sympathetic nervous system in male smokers. METHODS: Twenty-eight men (14 smokers and 14 non-smokers, ages 21-46 y) were recruited. The activity of the autonomic nervous system was measured by power spectral analysis of heart rate variability. Spectral power in the frequency domain was quantified by integrating the area under the curve of the very-low-frequency power (0.007-0.035 Hz), low-frequency power (0.035-0.15 Hz), high-frequency power (0.15-0.5 Hz), and total power (0.007-0.5 Hz) bandwidths. We assessed heart rate, thermoregulatory sympathetic nervous system activity (very-low-frequency power/total power), sympathetic nervous system activity (low-frequency-power/high-frequency power or [very-low-frequency power + low-frequency power]/high-frequency power), and parasympathetic nervous system activity (high-frequency power/total power) of the smokers before and after moderate-intensity exercise. RESULTS: The smokers exhibited a greater degree of sympathetic nervous system activity (as quantified by very-low-frequency power/total power). The sympathetic nervous system activity of smokers (as indicated by [very-low-frequency power + low-frequency power]/high-frequency power) also showed a tendency to increase after exercise. Parasympathetic activity, as indicated by high-frequency power/total power, reduced after exercise in the smokers. These findings are contrary to findings previously reported in obese subjects. CONCLUSIONS: Increased sympathetic nervous system activity, including thermoregulatory activity, might contribute to cachexia in smokers.

The relationship between skeletal muscle oxygenation and systemic oxygen uptake during exercise in subjects with COPD: a preliminary study.

BACKGROUND: Muscle oxygenation correlates with systemic oxygen uptake (V(O2)) in normal subjects; however, whether this relationship exists in COPD patients remains unclear. The purpose of this study was to investigate the influence of skeletal muscle oxygenation on V(O2) during exercise in patients with COPD. METHODS: Eight subjects performed an incremental cycle ergometer exercise test. We measured ventilation and pulmonary gas exchange with a metabolic measurement system. We also continuously monitored S(pO2), and measured tissue oxygen saturation (S(tO2)) in the vastus lateralis with continuous-wave near-infrared spectroscopy. We calculated the muscle oxygen extraction rate (MOER) based on S(pO2) and S(tO2). In addition, we calculated Pearson correlation coefficients to examine the relationships between the V(O2) obtained during exercise testing and the mean values of S(pO2), S(tO2), heart rate (HR), and MOER for each 30-second interval of the tests. Finally, we analyzed the relationships between the peak V(O2) and the slopes of HR/V(O2), S(pO2)/V(O2), S(tO2)/V(O2), and MOER/V(O2). RESULTS: With the increasing exercise intensity, many subjects showed a gradual decrease in S(tO2) and S(pO2), but a gradual increase in HR and MOER. V(O2) was negatively correlated with S(tO2) and S(pO2), and was positively correlated with HR and MOER. However, peak V(O2) was not correlated with any of the slopes. CONCLUSIONS: V(O2) is highly influenced by oxygen utilization in exercising muscles, as well as by blood oxygenation levels and cardiac function. However, the impact of skeletal muscle utilization during exercise on peak V(O2) varied greatly among the subjects.

Improvements in quadriceps force and work efficiency are related to improvements in endurance capacity following pulmonary rehabilitation in COPD patients.

BACKGROUND AND OBJECTIVE: The endurance time has been reported to be the most sensitive measure of improved exercise capacity in response to a variety of interventions for COPD. The aim of the present study was to determine whether the improvements in quadriceps force and measures obtained from a symptom-limited maximal test contributed to the improvements in endurance time following pulmonary rehabilitation. METHODS: Fifty-seven consecutive COPD subjects completed a 10-week pulmonary rehabilitation program. The subjects completed a symptom-limited incremental cycle ergometry test and a constant work rate test before and after pulmonary rehabilitation. Peripheral and respiratory muscle strength was also measured. The relationships between the change in endurance time and the changes obtained from the incremental test and muscle strength test were investigated. RESULTS: The endurance time showed the greatest improvement among the exercise capacity indices. The changes in endurance time were significantly correlated to changes in quadriceps force, peak work rate, anaerobic threshold and work efficiency on the incremental load test. In the multiple stepwise regression analysis, changes in quadriceps force and work efficiency measured on the maximal exercise test were selected. CONCLUSION: These findings suggest that the improvements in endurance time after pulmonary rehabilitation may be explained by increased quadriceps force and improvements in peak work rate and work efficiency.