Effects of pulmonary rehabilitation on functional and psychological parameters in post-acute sequelae of SARS-CoV-2 infection (PASC) patients.

BACKGROUND: COVID-19 survivors may develop long-term symptoms of fatigue, dyspnea, mental health issues, and functional limitations: a condition termed post-acute sequelae of COVID-19 (PASC). Pulmonary rehabilitation (PR) is a recommended treatment for PASC; however, there is a lack of data regarding PR's effect on multiple health indices and the factors that influence patient outcomes. The aim of our study is to evaluate the impact of pulmonary rehabilitation on functional and psychological parameters in patients diagnosed with Post-Acute Sequelae of SARS-CoV-2 Infection (PASC), thereby offering insights into the efficacy of such interventions in improving the quality of life and clinical outcomes for these individuals. METHODS: We extracted patient demographic, comorbidity, and outcome data from Allegheny Health Network's electronic medical records. Functionality test results were compared before and after PR, including 6-minute walk test (6MWT), chair rise repetitions (CR reps), timed up and go test (TUG), gait speed (Rehab gait), modified medical research council scale (MMRC), shortness of breath questionnaire (SOBQ), hospital anxiety and depression scale (HADS) and chronic obstructive pulmonary disease assessment test (CAT) scores. Multiple regression analysis was done to evaluate the effect of comorbidities and patient factors on patient responses to PR. RESULTS: The 55 patients included in this study had a mean time of 4 months between the initial COVID-19 diagnosis and the subsequent PASC diagnosis. Following pulmonary rehabilitation (PR), significant improvements were observed across various metrics. The distance covered in the 6-minute walk test (6MWT) increased markedly from a pre-rehabilitation average of 895 feet (SD 290) to 1,300 feet (SD 335) post-rehabilitation, with a mean change of 405 feet (95% CI [333, 477]). Chair rise repetitions (CR reps) saw an increase from 9 (SD 3) reps to 13 (SD 3) reps, with a change of 4 reps (95% CI [3.7, 4.9]). The timed up and go test (TUG) time decreased significantly from 13 s (SD 5) to 10 s (SD 2), reflecting a mean reduction of 3 s (95% CI [-4.5, -2.5]). Rehabilitation gait speed improved from 1.0 m/s to 1.3 m/s, changing by 0.3 m/s (95% CI [0.2, 0.3]). The Modified Medical Research Council (MMRC) dyspnea scale showed a notable decrease from a mean of 2 (SD 1) to 1 (SD 1), a change of -1 (95% CI [-1.5, -1]). The Shortness of Breath Questionnaire (SOBQ) scores reduced significantly from 51 (SD 21) to 22 (SD 18), with a change of -29 (95% CI [-34, -23]). The Hospital Anxiety and Depression Scale (HADS) scores decreased from 11 (SD 7) to 8 (SD 7), a reduction of -4 (95% CI [-5, -2]). Lastly, the Chronic Obstructive Pulmonary Disease (COPD) Assessment Test (CAT) scores significantly dropped from 18 (SD 7) to 9 (SD 7), changing by -10 (95% CI [-11, -8]). However, the presence of hypertension, diabetes, chronic lung diseases, outpatient status, and receipt of specific pharmacologic treatments (decadron, decadron + remdesivir, and decadron + remdesivir + tocilizumab) were identified as factors associated with a poor response to PR. CONCLUSION: Our study supports PR as an integrated model of care for PASC patients to improve several physical and mental health indices. The long-term effects of PR on patients' functional status should be investigated in the future.

Respiratory symptom perception during exercise in patients with heart failure with preserved ejection fraction.

We investigated whether central or peripheral limitations to oxygen uptake elicit different respiratory sensations and whether dyspnea on exertion (DOE) provokes unpleasantness and negative emotions in patients with heart failure with preserved ejection fraction (HFpEF). 48 patients were categorized based on their cardiac output (Q̇c)/oxygen uptake (V̇O2) slope and stroke volume (SV) reserve during an incremental cycling test. 15 were classified as centrally limited and 33 were classified as peripherally limited. Ratings of perceived breathlessness (RPB) and unpleasantness (RPU) were assessed (Borg 0-10 scale) during a 20 W cycling test. 15 respiratory sensations statements (1-10 scale) and 5 negative emotions statements (1-10) were subsequently rated. RPB (Central: 3.5±2.0 vs. Peripheral: 3.4±2.0, p=0.86), respiratory sensations, or negative emotions were not different between groups (p>0.05). RPB correlated (p<0.05) with RPU (r=0.925), "anxious" (r=0.610), and "afraid" (r=0.383). While DOE provokes elevated levels of negative emotions, DOE and respiratory sensations seem more related to a common mechanism rather than central and/or peripheral limitations in HFpEF.

Do Causes Influence Functional Aspects and Quality of Life in Patients with Nonfibrocystic Bronchiectasis?

Background: The denomination of noncystic fibrosis bronchiectasis (NCFB) includes several causes, and differences may be expected between the patient subgroups regarding age, comorbidities, and clinical and functional evolution. This study sought to identify the main causes of NCFB in a cohort of stable adult patients and to investigate whether such conditions would be different in their clinical, functional, and quality of life aspects. Methods: Between 2017 and 2019, all active patients with NCFB were prospectively evaluated searching for clinical data, past medical history, dyspnea severity grading, quality of life data, microbiological profile, and lung function (spirometry and six-minute walk test). Results: There was a female predominance; mean age was 54.7 years. Causes were identified in 82% of the patients, the most frequent being postinfections (n = 39), ciliary dyskinesia (CD) (n = 32), and chronic obstructive pulmonary disease (COPD) (n = 29). COPD patients were older, more often smokers (or former smokers) and with more comorbidities; they also had worse lung function (spirometry and oxygenation) and showed worse performance in the six-minute walk test (6MWT) (walked distance and exercise-induced hypoxemia). Considering the degree of dyspnea, in the more symptomatic group, patients had higher scores in the three domains and total score in SGRQ, besides having more exacerbations and more patients in home oxygen therapy. Conclusions: Causes most identified were postinfections, CD, and COPD. Patients with COPD are older and have worse pulmonary function and more comorbidities. The most symptomatic patients are clinically and functionally more severe, besides having worse quality of life.

Wearing face masks while climbing stairs influences respiratory physiology.

During the COVID-19 pandemic wearing face masks was mandatory. Nowadays, face masks are still encouraged indoors, especially in hospitals. People climbing stairs with masks describe unpredictable dyspnea. In this study, healthy adults climbed 5 floors with and without a mask. Various cardio-respiratory parameters were measured, including O2-saturation (O2-Sat) and end-tidal CO2(EtCO2), at baseline and on the top floor. Subjective indexes, such as Borg's scale, were evaluated. Thirty-two volunteers (16 males), median age 39 years (IQR 32.5-43), median BMI = 23.6 (IQR 21.5-25.1), with good fitness levels, participated. Comparing baseline to end-activity, median (IQR): O2-Sat change was -1.0% (-2-0) without mask, versus -3.0% (-4-0) with mask,p= 0.003; EtCO2+ 7.0 (+3.3-+9) without mask, versus +8.0 (+6-+12) with mask,p= 0.0001. Hypercarbia was seen in 5 (15.6%) participants without mask, median = 48 mmHg (IQR 47.5-51), and in 11 (34%) participants with mask, median = 50 mmHg (IQR 47-54),p< 0.001. Desaturation (O2-Sat < 95%) was seen in 5 (15.6%) participants without mask, median = 94% (IQR 93%-94%), and in 10 (31%) participants with mask, median = 91.5% (IQR 90%-93%),p= 0.06. Regression analysis demonstrated that only male sex was significantly associated with abnormal EtCO2(OR = 26.4, 95% CI = 1.9-366.4,p= 0.005). Ascent duration increased from median (IQR) of 94 s (86-100) without mask to 98 s (89-107) with mask,p< 0.001. Borg's scale of perceived exertion (range 0-10) increased from median (IQR) of 3.0 (2.5-3.87) without mask to 4.0 (3.0-4.37) with mask,p< 0.001. To conclude, during routine daily activities, such as stair-climbing, face masks cause dyspnea, and have measurable influences on ventilation, including true desaturation and hypercapnia, especially in males.

Mechanisms and consequences of excess exercise ventilation in fibrosing interstitial lung disease.

The causes and consequences of excess exercise ventilation (EEV) in patients with fibrosing interstitial lung disease (f-ILD) were explored. Twenty-eight adults with f-ILD and 13 controls performed an incremental cardiopulmonary exercise test. EEV was defined as ventilation-carbon dioxide output (⩒E-⩒CO2) slope ≥36 L/L. Patients showed lower pulmonary function and exercise capacity compared to controls. Lower DLCO was related to higher ⩒E-⩒CO2 slope in patients (P<0.05). 13/28 patients (46.4%) showed EEV, reporting higher dyspnea scores (P=0.033). Patients with EEV showed a higher dead space (VD)/tidal volume (VT) ratio while O2 saturation dropped to a greater extent during exercise compared to those without EEV. Higher breathing frequency and VT/inspiratory capacity ratio were observed during exercise in the former group (P<0.05). An exaggerated ventilatory response to exercise in patients with f-ILD is associated with a blunted decrease in the wasted ventilation in the physiological dead space and greater hypoxemia, prompting higher inspiratory constraints and breathlessness.

Core Function in Adults With Severe Asthma and Its Relationship With Breathing Symptoms.

BACKGROUND: People with asthma may have skeletal muscle dysfunction but data describing core function in severe asthma are limited. OBJECTIVE: To compare core function between people with severe asthma and healthy controls and to determine the difference between males and females. Furthermore, we aimed to investigate the association between core function and breathing symptoms. METHOD: Adults with a diagnosis of severe asthma and healthy controls undertook an assessment that included 3 core function tests: partial sit-up, Biering-Sorensen, and side bridge. Breathing symptoms were assessed by the modified Medical Research Council dyspnea scale, modified Borg scale, and Nijmegen questionnaire. RESULTS: People with severe asthma (n = 136) (38% male, age median [Q1-Q3] 59 y [45-68], body mass index 30 kg/m2 [26-37]) were compared with 66 people without respiratory disease (47% male, age 55 y [34-65], body mass index 25 kg/m2 [22-28]). There was no difference between groups in the partial sit-up (P = .09). However, participants with severe asthma performed worse with the Biering-Sorensen (P < .001), and the left and right side bridge test (P < .001 for both) than the healthy comparison group. Similar results were found when comparing males and females separately. Males with severe asthma had increased function compared with their female counterparts in the left side bridge test. Core function tests correlated with the breathing symptom measures, the modified Medical Research Council, modified Borg scale, and Nijmegen questionnaire (-0.51 > r > -0.19; P ≤ .03). CONCLUSIONS: Adults with severe asthma have worse core function than their control counterparts, independent of sex. Furthermore, as core function decreases, breathing symptoms increase.

Assessment of the cardiac output at rest and during exercise stress using real-time cardiovascular magnetic resonance imaging in HFpEF-patients.

This methodological study aimed to validate the cardiac output (CO) measured by exercise-stress real-time phase-contrast cardiovascular magnetic resonance imaging (CMR) in patients with heart failure and preserved ejection fraction (HFpEF). 68 patients with dyspnea on exertion (NYHA ≥ II) and echocardiographic signs of diastolic dysfunction underwent rest and exercise stress right heart catheterization (RHC) and CMR within 24 h. Patients were diagnosed as overt HFpEF (pulmonary capillary wedge pressure (PCWP) ≥ 15mmHg at rest), masked HFpEF (PCWP ≥ 25mmHg during exercise stress but < 15mmHg at rest) and non-cardiac dyspnea. CO was calculated using RHC as the reference standard, and in CMR by the volumetric stroke volume, conventional phase-contrast and rest and stress real-time phase-contrast imaging. At rest, the CMR based CO showed good agreement with RHC with an ICC of 0.772 for conventional phase-contrast, and 0.872 for real-time phase-contrast measurements. During exercise stress, the agreement of real-time CMR and RHC was good with an ICC of 0.805. Real-time measurements underestimated the CO at rest (Bias:0.71 L/min) and during exercise stress (Bias:1.4 L/min). Patients with overt HFpEF had a significantly lower cardiac index compared to patients with masked HFpEF and with non-cardiac dyspnea during exercise stress, but not at rest. Real-time phase-contrast CO can be assessed with good agreement with the invasive reference standard at rest and during exercise stress. While moderate underestimation of the CO needs to be considered with non-invasive testing, the CO using real-time CMR provides useful clinical information and could help to avoid unnecessary invasive procedures in HFpEF patients.

Contribution of Left Ventricular Diastolic Dysfunction to Survival and Breathlessness in Systemic Sclerosis-Associated Interstitial Lung Disease.

OBJECTIVE: To explore the effect of left ventricular (LV) diastolic dysfunction (LVDD) in systemic sclerosis (SSc)-associated interstitial lung disease (ILD), and to investigate SSc-specific associations and clinical correlates of LVDD. METHODS: There were 102 Australian Scleroderma Cohort Study participants with definite SSc and radiographic ILD included. Diastolic function was classified as normal, indeterminate, or abnormal according to 2016 American Society of Echocardiography/European Association of Cardiovascular Imaging guidelines for assessment of LV diastolic function. Associations between clinical features and patient- and physician-reported dyspnea were evaluated using logistic regression. Survival analyses were performed using Kaplan-Meier survival estimates and Cox regression modeling. RESULTS: LVDD was identified in 26% of participants, whereas 19% had indeterminate and 55% had normal diastolic function. Those with ILD and LVDD had increased mortality (hazard ratio 2.4, 95% CI 1.0-5.7; P = 0.05). After adjusting for age and sex, those with ILD and LVDD were more likely to have severe dyspnea on the Borg Dyspnoea Scale (odds ratio [OR] 2.6, 95% CI 1.0-6.6; P = 0.05) and numerically more likely to record World Health Organization Function Class II or higher dyspnea (OR 4.2, 95% CI 0.9-20.0; P = 0.08). Older age (95% CI 1.0-6.4; P = 0.05), hypertension (OR 5.0, 95% CI 1.8-13.8; P < 0.01), and ischemic heart disease (OR 4.8, 95% CI 1.5-15.7; P < 0.01) were all associated with LVDD, as was proximal muscle atrophy (OR 5.0, 95% CI 1.9-13.6; P < 0.01) and multimorbidity (Charlson Comorbidity Index scores ≥ 4, OR 3.0, 95% CI 1.1-8.7; P = 0.04). CONCLUSION: LVDD in SSc-ILD is more strongly associated with traditional LVDD risk factors than SSc-specific factors. LVDD is associated with worse dyspnea and survival in those with SSc-ILD.

Patient Perceptions of Exertion and Dyspnea With Interleukin-1 Blockade in Patients With Recently Decompensated Systolic Heart Failure.

Interleukin-1 (IL-1) blockade is an anti-inflammatory treatment that may affect exercise capacity in heart failure (HF). We evaluated patient-reported perceptions of exertion and dyspnea at submaximal exercise during cardiopulmonary exercise testing (CPET) in a double-blind, placebo-controlled, randomized clinical trial of IL-1 blockade in patients with systolic HF (REDHART [Recently Decompensated Heart Failure Anakinra Response Trial]). Patients underwent maximal CPET at baseline, 2, 4, and 12 weeks and rated their perceived level of exertion (RPE, on a scale from 6 to 20) and dyspnea on exertion (DOE, on a scale from 0 to 10) every 3 minutes throughout exercise. Patients also answered 2 questionnaires to assess HF-related quality of life: the Duke Activity Status Index and the Minnesota Living with Heart Failure Questionnaire. From baseline to the 12-week follow-up, IL-1 blockade significantly reduced RPE and DOE at 3- and 6-minutes during CPET without changing values for heart rate, oxygen consumption, and cardiac workload at 3- and 6-minutes. Linear regression identified 6-minute RPE to be a strong independent predictor of both physical symptoms (Minnesota Living with Heart Failure Questionnaire; ß = 0.474, p = 0.002) and perceived exercise capacity (Duke Activity Status Index; ß = -0.443, p = 0.008). In conclusion, patient perceptions of exertion and dyspnea at submaximal exercise may be valuable surrogates for quality of life and markers of response to IL-1 blockade in patients with HF.

De-novo development of fragmented QRS during a six-month follow-up period in patients with COVID-19 disease and its cardiac effects.

OBJECTIVE: The aim of this study is to examine the probability of de-novo fQRS in patients with mild COVID-19 disease, as an indicator of cardiac injury. METHODS: Data of 256 patients with normal admission electrocardiography and no comorbidities between 1.12.2020-31.12.2021, were examined retrospectively 6-month after mild COVID-19 disease. Patients were divided into two groups: fQRS+ group (n = 102) and non-fQRS group (n = 154). Relation between fQRS and other electrocardiography, echocardiographic and laboratory findings were investigated. RESULTS: No significant difference was found between the groups among age and gender. Troponin-I and creatine kinase myocardial band values (retrospectively 9.10 ± 1.76 vs 0.74 ± 1.43, 34.05 ± 82.20 vs. 14.68 ± 4.42), COVID-19 IgG levels (45.78 ± 14.82 vs. 36.49 ± 17.68), diastolic dysfunction (39.21% vs. 15.07%), EF value (58.02 ± 1.95 vs. 64.27 ± 3.07), dyspnea (41.17% vs. 6.84%), post-COVID-19 tachycardia syndrome (19.6% vs. 2.74) were more frequent in fQRS+ group compared to non-fQRS group. The EF value was lower in the presence of fQRS in the high lateral leads (57.12 ± 1.99, 58.47 ± 1.79, p:0.018). There was a positive correlation between IgG value and endsystolic diameter, septum thickness and left atrium diameter. In multivariate analysis de-novo fQRS, dyspnea, high troponin and IgG values, diastolic dysfunction, low EF value and left atrial diameter were determined as independent risk factors for post-COVID-19 tachycardia syndrome in follow-up. CONCLUSION: In COVID-19 disease de-novo fQRS, dyspnea, high IgG and troponin value, left atrial diameter, lower EF value, diastolic dysfunction were associated with post-COVID-19 tachycardia syndrome. The de-novo fQRS in SARS-COV-2 may be a predictor of future more important adverse cardiovascular outcomes and this should alert clinicians.

Classification and occurrence of an abnormal breathing pattern during cardiopulmonary exercise testing in subjects with persistent symptoms following COVID-19 disease.

Reduced exercise capacity and several limiting symptoms during exercise have been reported following severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. From clinical observations, we hypothesized that an abnormal breathing pattern (BrP) during exercise may be common in these patients and related to reduced exercise capacity. We aimed to (a) evaluate a method to classify the BrP as normal/abnormal or borderline in terms of inter-rater agreement; (b) determine the occurrence of an abnormal BrP in patients with post-COVID; and (c) compare characteristics of post-COVID patients with normal and abnormal BrP. In a retrospective, cross-sectional study of patients referred for CPET due to post-COVID April 2020-April 2021, we selected subjects without a history of intensive care and with available medical records. Three raters independently categorized patients' BrP as normal, abnormal, or borderline, using four traditional CPET plots (respiratory exchange ratio, tidal volume over ventilation, ventilatory equivalent for oxygen, and ventilation over time). Out of 20 patients (11 male), 10 were categorized as having a normal, 7 an abnormal, and three a borderline BrP. Inter-rater agreement was good (Fleiss' kappa: 0.66 [0.66-0.67]). Subjects with an abnormal BrP had lower peak ventilation, lower exercise capacity, similar ventilatory efficiency and a similar level of dyspnea at peak exercise, as did subjects with a normal BrP. Patients' BrP was possible to classify with good agreement between observers. A third of patients had an abnormal BrP, associated with lower exercise capacity, which could possibly explain exercise related symptoms in some patients with post-COVID syndrome.

Practical guide to cardiopulmonary exercise testing in adults.

Unexplained exertional dyspnoea or fatigue can arise from a number of underlying disorders and shows only a weak correlation with resting functional or imaging tests. Noninvasive cardiopulmonary exercise testing (CPET) offers a unique, but still under-utilised and unrecognised, opportunity to study cardiopulmonary and metabolic changes simultaneously. CPET can distinguish between a normal and an abnormal exercise response and usually identifies which of multiple pathophysiological conditions alone or in combination is the leading cause of exercise intolerance. Therefore, it improves diagnostic accuracy and patient health care by directing more targeted diagnostics and facilitating treatment decisions. Consequently, CPET should be one of the early tests used to assess exercise intolerance. However, this test requires specific knowledge and there is still a major information gap for those physicians primarily interested in learning how to systematically analyse and interpret CPET findings. This article describes the underlying principles of exercise physiology and provides a practical guide to performing CPET and interpreting the results in adults.

Comparison between 20 and 30 meters in walkway length affecting the 6-minute walk test in patients with chronic obstructive pulmonary disease: A randomized crossover study.

BACKGROUND: A 30-m walkway length for the 6-minute walk test (6MWT) is the standard recommendation established by the American Thoracic Society to assess patients with chronic obstructive pulmonary disease (COPD). This study aimed to compare between the distances of 20 and 30 m long corridor affecting 6MWT in COPD patients. METHODS: A randomized crossover study was conducted with patients. COPD patients were randomized 1:1 to either a 20-m or a 30-m walkway in the first test, then switched to the other in the second test. Physiologic parameters and 6-minute walking distance (6MWD) were recorded. RESULTS: Fifty subjects (92% men) were included: age 69.1±7.4 years, body mass index 22.9±5.5 kg/m2, FEV1 63.0±21.3%, and 50% having cardiovascular disease. The 6MWD in a 20-m and a 30-m walkway were 337.82±71.80 m and 359.85±77.25 m, respectively (P<0.001). Mean distance difference was 22.03 m (95% CI -28.29 to -15.76, P<0.001). Patients with a 20-m walkway had more turns than those with a 30-m walkway (mean difference of 4.88 turns, 95% CI 4.48 to 5.28, P<0.001). Also, higher systolic blood pressure was found in patients with a 20-m walkway after 6MWT (4.62 mmHg, P = 0.019). Other parameters and Borg dyspnea scale did not differ. CONCLUSIONS: The walkway length had significant effect on walking distance in COPD patients. A 30-m walkway length should still be recommended in 6MWT for COPD assessment. CLINICAL TRIAL REGISTRATION: Clinicaltrials.in.th number: TCTR20200206003.

A 21-Year-Old Man With Dyspnea, Wheezing, and Cough.

CASE PRESENTATION: A 21-year-old male college student presented for a second opinion with low alpha-1 antitrypsin (AAT) levels and complaints of episodic dyspnea with wheezing and cough. He was a never smoker with a medical history of frequent respiratory tract infections in early childhood and allergy to dander, dust mites, peanuts, and eggs. There was no travel history outside of the continental United States. His mother had asthma. His symptoms were not controlled on inhaled corticosteroids and bronchodilators. His AAT genotype was found to be PI∗SZ, and augmentation therapy (with pooled human-plasma derived AAT) was recommended locally.

The H2FPEF and HFA-PEFF algorithms for predicting exercise intolerance and abnormal hemodynamics in heart failure with preserved ejection fraction.

Exercise intolerance is a primary manifestation in patients with heart failure with preserved ejection fraction (HFpEF) and is associated with abnormal hemodynamics and a poor quality of life. Two multiparametric scoring systems have been proposed to diagnose HFpEF. This study sought to determine the performance of the H2FPEF and HFA-PEFF scores for predicting exercise capacity and echocardiographic findings of intracardiac pressures during exercise in subjects with dyspnea on exertion referred for bicycle stress echocardiography. In a subset, simultaneous expired gas analysis was performed to measure the peak oxygen consumption (VO2). Patients with HFpEF (n = 83) and controls without HF (n = 104) were enrolled. The H2FPEF score was obtainable for all patients while the HFA-PEFF score could not be calculated for 23 patients (feasibility 88%). Both H2FPEF and HFA-PEFF scores correlated with a higher E/e' ratio (r = 0.49 and r = 0.46), lower systolic tricuspid annular velocity (r = - 0.44 and = - 0.24), and lower cardiac output (r = - 0.28 and r = - 0.24) during peak exercise. Peak VO2 and exercise duration decreased with an increase in H2FPEF scores (r = - 0.40 and r = - 0.32). The H2FPEF score predicted a reduced aerobic capacity (AUC 0.71, p = 0.0005), but the HFA-PEFF score did not (p = 0.07). These data provide insights into the role of the H2FPEF and HFA-PEFF scores for predicting exercise intolerance and abnormal hemodynamics in patients presenting with exertional dyspnea.

Relationship between respiratory muscle endurance and dyspnea during high-intensity exercise in trained distance runners.

We hypothesized that the trained distance runners, who have a relatively high respiratory muscle endurance, but not high respiratory muscle strength, have lower dyspneic sensations during submaximal running. Twenty-one male collegiate distance runners participated. Incremental respiratory endurance tests (IRET) and maximal inspiratory mouth pressure (PImax) measurements were performed under resting conditions. A submaximal exercise test was also performed on a treadmill at two different speeds (16 and 18 km/h) for 4 min each, and the subjects reported the rate of dyspnea (range: 0-10). The time to endpoint during the IRET, an index of respiratory muscle endurance, ranged from 9.4 to 18.8 min, and PImax, as an index of inspiratory muscle strength, ranged from 74.1 to 137.0 cmH2O. The dyspnea rating during running at 16 and 18 km/h ranged from 1 to 6 and from 4 to 8, respectively. The relative exercise intensity was approximately 80 % of peak oxygen uptake (VO2peak) at 16 km/h and 90 %VO2peak at 18 km/h. The time to endpoint during the IRET was significantly negatively correlated with dyspnea during running at 18 km/h (r = -0.459, P = 0.040), but not at 16 km/h (r = -0.161, P = 0.470). There was no significant correlation between PImax and dyspnea during running at 16 km/h (r = -0.003, P = 0.989) or 18 km/h (r = 0.070, P = 0.755). These results suggest that dyspneic sensations during high-intensity running are related to respiratory muscle endurance, but not inspiratory muscle strength, in trained distance runners.