Pre-frailty status increases the risk of rehospitalization in patients after elective cardiac surgery without complication.

BACKGROUND AND AIM: It has been demonstrated that patients with pre-frailty have more adverse outcomes after cardiac surgery; however, data on prognosis and long-term evolution in patients with pre-frailty after elective cardiac surgery without postoperative complications are still scarce. To evaluate the impact of pre-frailty status on functional survival in patients after elective cardiac surgery without surgical complications. METHODS: This was a retrospective study with 141 patients over 65 years old, with an established diagnosis of myocardial infarction or valve disease. Patients were evaluated by Clinical Frailty Scale (CFS) before surgery, according to the hospital protocol, and allocated into two groups: non-frail (CFS, 1-3) and pre-frail (CFS = 4). Patients with adverse cardiovascular events during surgery or at intensive care unit (ICU), mechanical ventilation more than 24 hours, ICU length of stay more than 48 hours, and in-hospital complications were excluded. For all analyses, the statistical significance was set at 5% (P < .05). RESULTS: There were no differences in demographic, anthropometric, surgical procedure, or baseline data on ICU. Pre-frail patients had more adverse events during the 3-year follow-up period with rehospitalization compared to non-frail (39.4% vs 14.3%, respectively). Rehospitalizations in pre-frail patients were in the first year after cardiac surgery (P < .05), and higher cumulative events in pre-frail have occurred with increased odds ratio (OR) (2.828, 95% confidence interval [CI]: 1.298-6.160; P = .001) and hazard ratio (HR) (3.560, 95% CI: 1.508-84.04; P = .004). The OR and HR for stroke or death were similar between groups when analyzed separately. CONCLUSION: Pre-frail patients have more adverse events after elective cardiac surgery without complications when compared to non-frail patients.

Heart Failure Impairs Muscle Blood Flow and Endurance Exercise Tolerance in COPD.

Heart failure, a prevalent and disabling co-morbidity of COPD, may impair cardiac output and muscle blood flow thereby contributing to exercise intolerance. To investigate the role of impaired central and peripheral hemodynamics in limiting exercise tolerance in COPD-heart failure overlap, cycle ergometer exercise tests at 20% and 80% peak work rate were performed by overlap (FEV1 = 56.9 ± 15.9% predicted, ejection fraction = 32.5 ± 6.9%; N = 16), FEV1-matched COPD (N = 16), ejection fraction-matched heart failure patients (N = 15) and controls (N = 12). Differences (Δ) in cardiac output (impedance cardiography) and vastus lateralis blood flow (indocyanine green) and deoxygenation (near-infrared spectroscopy) between work rates were expressed relative to concurrent changes in muscle metabolic demands (ΔO2 uptake). Overlap patients had approximately 30% lower endurance exercise tolerance than COPD and heart failure (p < 0.05). ΔBlood flow was closely proportional to Δcardiac output in all groups (r = 0.89-0.98; p < 0.01). Overlap showed the largest impairments in Δcardiac output/ΔO2 uptake and Δblood flow/ΔO2 uptake (p < 0.05). Systemic arterial oxygenation, however, was preserved in overlap compared to COPD. Blunted limb perfusion was related to greater muscle deoxygenation and lactate concentration in overlap (r = 0.78 and r = 0.73, respectively; p < 0.05). ΔBlood flow/ΔO2 uptake was related to time to exercise intolerance only in overlap and heart failure (p < 0.01). In conclusion, COPD and heart failure add to decrease exercising cardiac output and skeletal muscle perfusion to a greater extent than that expected by heart failure alone. Treatment strategies that increase muscle O2 delivery and/or decrease O2 demand may be particularly helpful to improve exercise tolerance in COPD patients presenting heart failure as co-morbidity.

The Effects of Exercise on Cardiogenic Shock with an Intra-Aortic Balloon Pump: A Case Report. / Efeitos do Exercício em Choque Cardiogênico e Balão Intra-Aórtico: Um Relato de Caso.

This case report describes the exercise program on a hospitalized 54-year-old male patient with cardiogenic shock waiting for a heart transplant assisted by an intra-aortic balloon pump, a temporary mechanical circulatory support device. The temporary mechanical circulatory support device, an intra-aortic balloon pump, was placed in the left subclavian artery, enabling the exercise protocol. Measurements and values from Swan-Ganz catheter, blood sample, brain natriuretic peptide (NT-proBNP), and high-sensitivity C-reactive protein (hs-CRP), as well as the six-minute walk test (6MWT) and venous oxygen saturation (SvO2) were obtained before and after an exercise protocol. The exercise training protocol involved the use of an unloaded bed cycle ergometer once a day, for a maximum of 30 minutes, to the tolerance limit. No adverse events or events related to the dislocation of the intra-aortic balloon pump were observed during the exercise protocol. The exercise program resulted in higher SvO2 levels, with an increased 6MWT with lower Borg dyspnea scores (312 meters vs. 488 meters and five points vs. three points, respectively). After completing the ten-day exercise protocol, the patient underwent a non-complicated heart transplant surgery and a full recovery in the ICU. This study showed that exercise is a feasible option for patients with cardiogenic shock who are using an intra-aortic balloon pump and that it is well-tolerated with no reported adverse events.

O presente relato de caso descreve o programa de exercícios aplicado a um paciente do sexo masculino, de 54 anos, internado com choque cardiogênico, aguardando transplante cardíaco e assistido por balão intra-aórtico, um dispositivo de suporte circulatório mecânico temporário. O dispositivo de suporte circulatório mecânico temporário, um balão intra-aórtico, foi colocado na artéria subclávia esquerda, possibilitando o protocolo de exercícios. Antes e após um protocolo de exercícios, foram obtidos dados a partir de cateter de Swan-Ganz, amostra de sangue, peptídeo natriurético cerebral (NT-proBNP), proteína C reativa de alta sensibilidade (PCR-as), teste de caminhada de seis minutos (TC6min) e medição da saturação venosa de oxigênio (SvO2). O protocolo de treinamento físico envolveu a utilização de um cicloergômetro adaptado ao leito, sem carga, uma vez ao dia, por no máximo 30 minutos, até o limite da tolerância. Não foram observados eventos adversos tampouco relacionados ao deslocamento do balão intra-aórtico durante o protocolo de exercícios. O programa de exercícios resultou em maior SvO2 com aumento do TC6min e menores escores de dispneia de Borg (312 metros vs. 488 metros e cinco pontos vs. três pontos, respectivamente). Após completar o protocolo de exercícios de dez dias, o paciente foi submetido a uma cirurgia de transplante cardíaco sem complicações e recuperação total na UTI. O presente estudo demonstrou que o exercício é uma opção viável para pacientes com choque cardiogênico em uso de balão intra-aórtico e que é bem tolerado, além de não haver relatos de eventos adversos.

Heart failure worsens leg muscle strength and endurance in coexistence patients with COPD and heart failure reduced ejection fraction.

Purpose: Exercise intolerance and dyspnoea are clinical symptoms in both heart failure (HF) reduced ejection fraction (HFrEF) and chronic obstructive pulmonary disease (COPD), which are suggested to be associated with musculoskeletal dysfunction. We tested the hypothesis that HFrEF + COPD patients would present lower muscle strength and greater fatigue compared to compared to the COPD group. Methods: We included 25 patients with HFrEF + COPD (100% male, age 67.8 ± 6.9) and 25 patients with COPD alone (100% male, age 66.1 ± 9.1). In both groups, COPD severity was determined as moderate-to-severe according to the GOLD classification (FEV1/FVC < 0.7 and predicted post-bronchodilator FEV1 between 30%-80%). Knee flexor-extensor muscle performance (torque, work, power and fatigue) were measured by isokinetic dynamometry in age and sex-matched patients with HFrEF + COPD and COPD alone; Functional capacity was assessed by the cardiopulmonary exercise test, the 6-min walk test (6MWT) and the four-minute step test. Results: The COPD group exhibited reduced lung function compared to the HFrEF + COPD group, as evidenced by lower FEV1/FVC (58.0 ± 4.0 vs. 65.5 ± 13.9; p < 0.0001, respectively) and FEV1 (51.3 ± 17.0 vs. 62.5 ± 17.4; p = 0.026, respectively) values. Regarding musculoskeletal function, the HFrEF + COPD group showed a knee flexor muscles impairment, however this fact was not observed in the knee extensors muscles. Power peak of the knee flexor corrected by muscle mass was significantly correlated with the 6MWT (r = 0.40; p < 0.05), number of steps (r = 0.30; p < 0.05) and work ratepeak (r = 0.40; p < 0.05) in the HFrEF + COPD and COPD groups. Conclusion: The presence of HFrEF in patients with COPD worsens muscular weakness when compared to isolated COPD.

Mortality in a swiftly repurposed hospital in northeast Brazil during the first and second COVID-19 waves: A retrospective cohort study.

Background: The first months of the coronavirus disease 2019 (COVID-19) pandemic demanded rapid re-organization of available local resources. This study evaluated the performance of a private hospital in the Brazilian state of Ceará that was swiftly repurposed into a public tertiary COVID-19 centre during the first wave of the COVID-19 pandemic, and how it improved in the second wave. Methods: This retrospective cohort study included 2492 patients with COVID-19 at Hospital Estadual Leonardo da Vinci (HELV) during the first and second waves. Demographic, clinical and laboratory data were collected using a dedicated web platform (ResCOVID). A Poisson regression model was used to estimate factors associated with in-hospital mortality. Results: Differences in demographics and clinical features were found between the two waves. There was reduced in-hospital mortality during the second wave (36.2%) in comparison with the first wave (48.8%). Invasive mechanical ventilation showed the strongest association with increased risk of death in both waves {first wave: relative risk (RR) 4.28 [95% confidence interval (CI) 2.86-6.41], P<0.001; second wave: RR 12.94 (95% CI 3.4-49.12), P<0.001}. Conclusions: HELV was a pillar in the strategic public health plan to respond to COVID-19 in Ceará, helping to assist a group of moderate-to-severe cases and reduce the pressure on emergency and primary care facilities. Although mortality in intubated individuals remained high, there was an overall decrease in the in-hospital mortality rate in the second wave.

Sildenafil improves microvascular O2 delivery-to-utilization matching and accelerates exercise O2 uptake kinetics in chronic heart failure.

Nitric oxide (NO) can temporally and spatially match microvascular oxygen (O(2)) delivery (Qo(2mv)) to O(2) uptake (Vo(2)) in the skeletal muscle, a crucial adjustment-to-exercise tolerance that is impaired in chronic heart failure (CHF). To investigate the effects of NO bioavailability induced by sildenafil intake on muscle Qo(2mv)-to-O(2) utilization matching and Vo(2) kinetics, 10 males with CHF (ejection fraction = 27 ± 6%) undertook constant work-rate exercise (70-80% peak). Breath-by-breath Vo(2), fractional O(2)extraction in the vastus lateralis {∼deoxygenated hemoglobin + myoglobin ([deoxy-Hb + Mb]) by near-infrared spectroscopy}, and cardiac output (CO) were evaluated after sildenafil (50 mg) or placebo. Sildenafil increased exercise tolerance compared with placebo by ∼20%, an effect that was related to faster on- and off-exercise Vo(2) kinetics (P < 0.05). Active treatment, however, failed to accelerate CO dynamics (P > 0.05). On-exercise [deoxy-Hb + Mb] kinetics were slowed by sildenafil (∼25%), and a subsequent response "overshoot" (n = 8) was significantly lessened or even abolished. In contrast, [deoxy-Hb + Mb] recovery was faster with sildenafil (∼15%). Improvements in muscle oxygenation with sildenafil were related to faster on-exercise Vo(2) kinetics, blunted oscillations in ventilation (n = 9), and greater exercise capacity (P < 0.05). Sildenafil intake enhanced intramuscular Qo(2mv)-to-Vo(2) matching with beneficial effects on Vo(2) kinetics and exercise tolerance in CHF. The lack of effect on CO suggests that improvement in blood flow to and within skeletal muscles underlies these effects.

Timing to out-of-bed mobilization and mobility levels of COVID-19 patients admitted to the ICU: Experiences in Brazilian clinical practice.

INTRODUCTION: At the beginning of the coronavirus disease 2019 (COVID-19) pandemic, there was scarce data about clinical/functional conditions during hospitalization or after hospital discharge. Little was known about COVID-19 repercussions and how to do early mobilization in intensive care unit (ICU). OBJECTIVE: Identify the time to the initiation of out-of-bed mobilization and the levels of mobility (sitting over the edge of the bed, sitting in a chair, standing, and ambulating) reached by critically ill patients with COVID-19 during hospitalization and the factors that could impact early mobilization. METHODS: This was a retrospective observational study of patients with COVID-19 in the ICU. RESULTS: There were 157 surviving COVID-19 patients included in the study (median age: 61 years; median ICU length of stay: 12 days). The median time to initiate out-of-bed mobilization in the ICU was 6 days; between patients who received mechanical ventilation (MV) compared with those who did not, this time was 8 vs. 2.5 days (p < .001). Most patients who used MV were mobilized after extubation (79.6%). During ICU stays, 88.0% of all patients were mobilized out of bed, and 41.0% were able to ambulate either with assistance or independently. The time to initiate out-of-bed mobilization is associated with sedation time and MV time. CONCLUSION: Despite the pandemic scenario, patients were quickly mobilized out of bed, and most of the patients achieved higher mobility levels in the ICU and at hospital discharge. Sedation time and MV time were associated with delays in initiating mobilization.

Oxygen supplementation increases the total work and muscle damage markers but reduces the inflammatory response in COPD patients.

INTRODUCTION: Oxygen supplementation (O2-Suppl) is recommended for pulmonary rehabilitation with higher exercise intensities. However, high-intensity exercise tends toward muscle damage and a greater inflammatory response. We aimed to investigate the effect of O2-Suppl during exercise test (EET) on CRP level and muscle damage (CPK, LDH, lactate) in non-hypoxemic COPD patients. METHODS: Eleven non-depleted patients with COPD (FEV1 65.5 ± 4.3 %) performed two EET (room-air or O2-Suppl-100 %), through a blind, randomized, and placebo-controlled crossover design. CPK, LDH and CRP were measured before, immediately after and 24 h after EET. RESULTS: Exercise time was higher with O2-Suppl (49.9 ± 37.3 %; p = 0.001) and increases in CPK and LDH were observed compared to basal values in the O2-Suppl (28.4UI/L and 28.3 UI/L). The O2-Suppl protocol resulted in a lower increase in CRP (92.1 ± 112.4 % vs. 400.1 ± 384.9 %; p = 0.003). CONCLUSIONS: O2-Suppl increases exercise-tolerance, resulting in increased muscle injury markers in COPD. However, oxygen supplementation attenuates the inflammatory response, even upon increased physical exercise.

Safety and Efficacy of Aerobic Exercise Training Associated to Non-Invasive Ventilation in Patients with Acute Heart Failure.

BACKGROUND: Exercise training (ET) improves functional capacity in chronic heart failure (HF). However, ET effects in acute HF are unknown. OBJECTIVE: To investigate the effects of ET alone or combined with noninvasive ventilation (NIV) compared with standard medical treatment during hospitalization in acute HF patients. METHODS: Twenty-nine patients (systolic HF) were randomized into three groups: control (Control - only standard medical treatment); ET with placebo NIV (ET+Sham) and ET+NIV (NIV with 14 and 8 cmH2O of inspiratory and expiratory pressure, respectively). The 6MWT was performed on day 1 and day 10 of hospitalization and the ET was performed on an unloaded cycle ergometer until patients' tolerance limit (20 min or less) for eight consecutive days. For all analyses, statistical significance was set at 5% (p < 0.05). RESULTS: None of the patients in either exercise groups had adverse events or required exercise interruption. The 6MWT distance was greater in ET+NIV (Δ120 ± 72 m) than in ET+Sham (Δ73 ± 26 m) and Control (Δ45 ± 32 m; p < 0.05). Total exercise time was greater (128 ± 10 vs. 92 ± 8 min; p < 0.05) and dyspnea was lower (3 ± 1 vs. 4 ± 1; p < 0.05) in ET+NIV than ET+Sham. The ET+NIV group had a shorter hospital stay (17 ± 10 days) than ET+Sham (23 ± 8 days) and Control (39 ± 15 days) groups (p < 0.05). Total exercise time in ET+Sham and ET+NIV had significant correlation with length of hospital stay (r = -0.75; p = 0.01). CONCLUSION: Exercise training in acute HF was safe, had no adverse events and, when combined with NIV, improved 6MWT and reduce dyspnea and length of stay.

Current challenges in managing comorbid heart failure and COPD.

INTRODUCTION: Heart failure (HF) with reduced ejection fraction and chronic obstructive pulmonary disease (COPD) frequently coexist, particularly in the elderly. Given their rising prevalence and the contemporary trend to longer life expectancy, overlapping HF-COPD will become a major cause of morbidity and mortality in the next decade. Areas covered: Drawing on current clinical and physiological constructs, the consequences of negative cardiopulmonary interactions on the interpretation of pulmonary function and cardiopulmonary exercise tests in HF-COPD are discussed. Although those interactions may create challenges for the diagnosis and assessment of disease stability, they provide a valuable conceptual framework to rationalize HF-COPD treatment. The impact of COPD or HF on the pharmacological treatment of HF or COPD, respectively, is then comprehensively discussed. Authors finalize by outlining how the non-pharmacological treatment (i.e. rehabilitation and exercise reconditioning) can be tailored to the specific needs of patients with HF-COPD. Expert commentary: Randomized clinical trials testing the efficacy and safety of new medications for HF or COPD should include a sizeable fraction of patients with these coexistent pathologies. Multidisciplinary clinics involving cardiologists and respirologists trained in both diseases (with access to unified cardiorespiratory rehabilitation programs) are paramount to decrease the humanitarian and social burden of HF-COPD.

Short-term effects of non-invasive ventilation on cerebral blood flow and cognitive function in COPD.

OBJECTIVES: Investigate the acute effects of non-invasive ventilation (NIV) on cerebral blood flow (CBF) and on cognitive functions in COPD. METHODS: Nine non-hypercapnic stable COPD and twelve healthy controls were enrolled. CBF (transcranial Doppler), cognitive tests and cardiorespiratory response were performed at baseline, during one hour of NIV and after 30 min. RESULTS: Both groups had an increase in tidal volume and reduction in respiratory rate during NIV, but only controls showed PaCO2 reductions (41.2 ±â€¯4.6 to 36.5 ±â€¯7.3 in controls vs. 40.9 ±â€¯4.5 to 42.9 ±â€¯5.9 in COPD). During NIV CBF was significantly reduced in healthy controls and COPD, although this effect was less pronounced in the latter. At the same time, healthy controls demonstrated an improvement in cognitive executive function compared to COPD in the Trail Making Test part B (90.5 vs. 180s; respectively). CONCLUSION: NIV application for one hour reversibly reduced CBF in healthy controls and non-hypercapnic stable COPD patients, despite no significant reductions of the PaCO2 in the latter group. It was associated with minor cognitive improvements in the executive function in healthy volunteers, but not in COPD.

Pre-Frailty Increases the Risk of Adverse Events in Older Patients Undergoing Cardiovascular Surgery.

BACKGROUND: Frailty is identified as a major predictor of adverse outcomes in older surgical patients. However, the outcomes in pre-frail patients after cardiovascular surgery remain unknown. OBJECTIVE: To investigate the main outcomes (length of stay, mechanical ventilation time, stroke and in-hospital death) in pre-frail patients in comparison with no-frail patients after cardiovascular surgery. METHODS: 221 patients over 65 years old, with established diagnosis of myocardial infarction or valve disease were enrolled. Patients were evaluated by Clinical Frailty Score (CFS) before surgery and allocated into 2 groups: no-frailty (CFS 1~3) vs. pre-frailty (CFS 4) and followed up for main outcomes. For all analysis, the statistical significance was set at 5% (p < 0.05). RESULTS: No differences were found in anthropometric and demographic data between groups (p > 0.05). Pre-frail patients showed a longer mechanical ventilation time (193 ± 37 vs. 29 ± 7 hours; p<0.05) than no-frail patients; similar results were observed for length of stay at the intensive care unit (5 ± 1 vs. 3 ± 1 days; p < 0.05) and total time of hospitalization (12 ± 5 vs. 9 ± 3 days; p < 0.05). In addition, the pre-frail group had a higher number of adverse events (stroke 8.3% vs. 3.9%; in-hospital death 21.5% vs. 7.8%; p < 0.05) with an increased risk for development stroke (OR: 2.139, 95% CI: 0.622-7.351, p = 0.001; HR: 2.763, 95%CI: 1.206-6.331, p = 0.0001) and in-hospital death (OR: 1.809, 95% CI: 1.286-2.546, p = 0.001; HR: 1.830, 95% CI: 1.476-2.269, p = 0.0001). Moreover, higher number of pre-frail patients required homecare services than no-frail patients (46.5% vs. 0%; p < 0.05). CONCLUSION: Patients with pre-frailty showed longer mechanical ventilation time and hospital stay with an increased risk for cardiovascular events compared with no-frail patients.

Hemodynamics and tissue oxygenation effects after increased in positive end-expiratory pressure in coronary artery bypass surgery.

BACKGROUND: Cardiac surgery is widely used in the treatment of cardiovascular diseases. However, several complications can be observed during the postoperative period. Positive end expiratory pressure (PEEP) improves gas exchange, but it might be related to decreased cardiac output and possible impairment of tissue oxygenation. The aim of this study was to investigate the hemodynamic effects and oxygen saturation of central venous blood (ScvO2) after increasing PEEP in hypoxemic patients after coronary artery bypass (CAB) surgery. METHODS: Seventy post-cardiac surgery patients (CAB), 61 ± 7 years, without ventricular dysfunction (left ventricular ejection fraction 57 ± 2%), with hypoxemia (PaO2/FiO2 ratio <200) were enrolled. Heart rate, mean arterial pressure, arterial and venous blood samples were measured at intensive care unit and PEEP was increased to 12 cmH2O for 30 min. RESULTS: As expected, PEEP12 improved arterial oxygenation and PaO2/FiO2 ratio (p < 0.0001). Reduction in ScvO2 was observed between PEEP5 (63 ± 2%) and PEEP12 (57 ± 1%; p = 0.01) with higher values of blood lactate in PEEP12 (p < 0.01). No hemodynamic effects (heart rate, mean arterial pressure, SpO2; p > 0.05) were related. CONCLUSION: Increased PEEP after cardiac surgery decreased ScvO2 and increased blood lactate, even with higher O2 delivery. PEEP did not interfere in hemodynamics status in CAB patients, suggesting that peripheral parameters must be controlled and measured during procedures involving increased PEEP in post-cardiac surgery patients in the intensive care unit.

Effects of heart failure on cerebral blood flow in COPD: Rest and exercise.

Cerebral blood flow (CBF) and oxygenation (COx) are generally well-preserved in COPD. It is unknown whether prevalent cardiovascular co-morbidities, such as heart failure, may impair CBF and COx responses to exertion. Eighteen males with moderate-to-severe COPD (8 with and 10 without overlapping heart failure) underwent a progressive exercise test with pre-frontal CBF and COx measurements (indocyanine green and near-infrared spectroscopy). Mean arterial pressure and cardiac output were lower from rest to exercise in overlap. Only COPD patients demonstrated an increase in arterialized PCO2 towards the end of progressive exercise. CBF index was consistently higher and increased further by ∼40% during exercise in COPD whereas a ∼10% reduction was observed in overlap. COx was lower in overlap despite preserved arterial oxygenation. In conclusion, heart failure introduces pronounced negative effects on CBF and COx in COPD which may be associated with clinically relevant outcomes, including dyspnea, exercise intolerance, cerebrovascular disease and cognitive impairment.

Alternatives to Aerobic Exercise Prescription in Patients with Chronic Heart Failure.

BACKGROUND: Exercise is essential for patients with heart failure as it leads to a reduction in morbidity and mortality as well as improved functional capacity and oxygen uptake (v̇O2). However, the need for an experienced physiologist and the cost of the exam may render the cardiopulmonary exercise test (CPET) unfeasible. Thus, the six-minute walk test (6MWT) and step test (ST) may be alternatives for exercise prescription. OBJECTIVE: The aim was to correlate heart rate (HR) during the 6MWT and ST with HR at the anaerobic threshold (HRAT) and peak HR (HRP) obtained on the CPET. METHODS: Eighty-three patients (58 ± 11 years) with heart failure (NYHA class II) were included and all subjects had optimized medication for at least 3 months. Evaluations involved CPET (v̇O2, HRAT, HRP), 6MWT (HR6MWT) and ST (HRST). RESULTS: The participants exhibited severe ventricular dysfunction (ejection fraction: 31 ± 7%) and low peak v̇O2 (15.2 ± 3.1 mL.kg-1.min-1). HRP (113 ± 19 bpm) was higher than HRAT (92 ± 14 bpm; p < 0.05) and HR6MWT (94 ± 13 bpm; p < 0.05). No significant difference was found between HRP and HRST. Moreover, a strong correlation was found between HRAT and HR6MWT (r = 0.81; p < 0.0001), and between HRP and HRST (r = 0.89; p < 0.0001). CONCLUSION: These findings suggest that, in the absence of CPET, exercise prescription can be performed by use of 6MWT and ST, based on HR6MWT and HRST.

Cerebral microvascular blood flow and CO2 reactivity in pulmonary arterial hypertension.

Hypocapnia and endothelial dysfunction might impair microvascular cerebral blood flow (CBFmicr) and cerebrovascular reactivity to CO2 (CVRCO2). Pulmonary arterial hypertension (PAH) is characteristically associated with chronic alveolar hyperventilation and microvascular endothelial dysfunction. We therefore determined CBFmicr (pre-frontal blood flow index (BFI) by the indocyanine green-near infrared spectroscopy methodology) during hypocapnia and hypercapnia in 25 PAH patients and 10 gender- and age-matched controls. Cerebral BFI was lower in patients than controls at similar transcutaneous PCO2 (PtcCO2) levels in both testing conditions. In fact, while BFI increased from hypocapnia to hypercapnia in all controls, it failed to increase in 17/25 (68%) patients. Thus, BFI increased to a lesser extent from hypo to hypercapnia ("Δ") in patients, i.e., they showed lower Δ BFI/Δ PtcCO2 ratios than controls. In conclusion, CBFmicr and CVRCO2 are lessened in clinically stable, mildly-impaired patients with PAH. These abnormalities might be associated with relevant clinical outcomes (hyperventilation and dyspnea, cognition, cerebrovascular disease) being potentially amenable to pharmacological treatment.

Does impaired O2 delivery during exercise accentuate central and peripheral fatigue in patients with coexistent COPD-CHF?

Impairment in oxygen (O2) delivery to the central nervous system ("brain") and skeletal locomotor muscle during exercise has been associated with central and peripheral neuromuscular fatigue in healthy humans. From a clinical perspective, impaired tissue O2 transport is a key pathophysiological mechanism shared by cardiopulmonary diseases, such as chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF). In addition to arterial hypoxemic conditions in COPD, there is growing evidence that cerebral and muscle blood flow and oxygenation can be reduced during exercise in both isolated COPD and CHF. Compromised cardiac output due to impaired cardiopulmonary function/interactions and blood flow redistribution to the overloaded respiratory muscles (i.e., ↑work of breathing) may underpin these abnormalities. Unfortunately, COPD and CHF coexist in almost a third of elderly patients making these mechanisms potentially more relevant to exercise intolerance. In this context, it remains unknown whether decreased O2 delivery accentuates neuromuscular manifestations of central and peripheral fatigue in coexistent COPD-CHF. If this holds true, it is conceivable that delivering a low-density gas mixture (heliox) through non-invasive positive pressure ventilation could ameliorate cardiopulmonary function/interactions and reduce the work of breathing during exercise in these patients. The major consequence would be increased O2 delivery to the brain and active muscles with potential benefits to exercise capacity (i.e., ↓central and peripheral neuromuscular fatigue, respectively). We therefore hypothesize that patients with coexistent COPD-CHF stop exercising prematurely due to impaired central motor drive and muscle contractility as the cardiorespiratory system fails to deliver sufficient O2 to simultaneously attend the metabolic demands of the brain and the active limb muscles.

Additive effects of non-invasive ventilation to hyperoxia on cerebral oxygenation in COPD patients with exercise-related O2 desaturation.

BACKGROUND: It is currently unknown whether potential haemodynamic improvements induced by non-invasive ventilation (NIV) would positively impact upon cerebral oxygenation (COx) in patients with moderate-to-severe chronic obstructive pulmonary disease (COPD). OBJECTIVE: To investigate the effects of NIV on exercise COx in COPD patients presenting with exercise-related O(2) desaturation. METHODS: On a double-blind trial, 13 males (FEV1 = 48·8 ± 15·1% predicted) were randomly assigned to NIV (16 cmH(2)O IPS and 5 cmH(2)O PEEP) plus HOx (FiO(2) = 0·4) or sham NIV (7 cmH(2)O IPS and 5 cmH(2)O PEEP to overcome breathing circuit resistance) plus HOx during ramp-incremental exercise performed on different days. Near-infrared spectroscopy and impedance cardiography assessed changes (Δ) in COx and cardiac output (Q(T)), respectively. RESULTS: There were no significant between-intervention differences in peak work rate, ventilation and reported symptoms (P>0·05). Peripheral oxyhaemoglobin saturation remained above 98% throughout the tests. NIV + HOx was associated with larger increases in Δ COx, Δ Q(T) and Δ stroke volume at maximal and submaximal exercise (P<0·05). Increases in the area under the curve (to an iso-work rate) of Δ COx under NIV + HOx were significantly (P<0·01) correlated with improvements in Δ Q(T) (r = 0·82) and Δ stroke volume (r = 0·87). There was, however, no significant correlation between enhancement in these physiological responses with changes in peak work rate with NIV + HOx (P>0·05). CONCLUSIONS: NIV added benefit to HOx in improving central haemodynamics and COx in O(2) 'desaturators' with COPD. The clinical relevance of such beneficial effects on exercise tolerance, however, remains to be demonstrated.