Attenuated Microcirculatory Response to Maximal Exercise in Patients With Chronic Heart Failure

PURPOSE

Exercise training programs improve microcirculatory alternations in patients with chronic heart failure (CHF). However less is known about the acute effect of maximum exercise on the skeletal muscle microcirculation. We aimed to assess the effect of acute exercise on peripheral microcirculation of patients with CHF, as assessed by near-infrared spectroscopy with vascular occlusion technique.

METHODS

Tissue oxygenation was evaluated in 8 stable patients with CHF (7 males; mean age, 60 ± 9 years; body mass index, 26.3 ± 3.8 kg/m) and 8 healthy subjects (matched for age, sex, and body mass index) before and after cardiopulmonary exercise testing. Tissue oxygen saturation (StO2), StO2peak, oxygen consumption rate, and endothelial function (reperfusion rate), before and after maximum exercise, were assessed.

RESULTS

Patients with CHF had lower StO2 and reperfusion rate compared with healthy subjects (71.4% ± 9.8% vs 81.0% ± 5.4% and 9 ± 1 %/min vs 13.9 ± 5.8%/min, respectively; P < .05) at rest. Oxygen consumption rate increased after exercise in patients with CHF and healthy subjects (from -31.7 ± 8.2 to -43.7 ± 12.7 and from -35.7 ± 6.7 to -42.4 ± 6.4, respectively; P < .05). StO2 decreased significantly after maximal exercise in patients with CHF (from 71.4 ± 9.8 to 65.2 ± 12.7; P < .05), whereas it returned to the preexercise values in healthy subjects (from 81.0 ± 5.4 to 80.3 ± 7.0). There was a significant between-group difference (P < .05).

CONCLUSIONS

Patients with CHF present microcirculatory alternations. Acute exercise exerts an effect on microcirculation in peripheral, nonexercising muscles, with altered response in patients with CHF compared with healthy subjects.

Prolonged Oxygen Kinetics During Constant Workload Submaximal Exercise Is Associated With Disease Severity in Adult Subjects With Cystic Fibrosis

BACKGROUND

The goal of this study was to explore the relation between oxygen kinetics during constant work load submaximal cardiopulmonary exercise test (CPET) and disease severity in adult subjects with cystic fibrosis.

METHODS

Fourteen adult subjects with cystic fibrosis (CF; 8 males, 22 ± 4 y old) and a mean Schwachman score of 73 ± 11 and 10 healthy individuals (5 males, 29 ± 4 y old) underwent pulmonary function tests at rest, maximal and constant work load submaximal CPET on a cycloergometer. Breath-by-breath analysis was used for measuring oxygen kinetic parameters and the time constant (tau), expressing phase 2 of submaximal CPET.

RESULTS

Subjects with CF had a significantly prolonged tau compared with healthy subjects (42.3 ± 21.5 vs. 29.3 ± 6.4, s, P < .05). The tau during phase 2 was inversely correlated with FEV1(% pred) (r = -0.77, P = .001), breathing reserve (r = -0.74, P = .003), V̇O2peak (r = -0.53, P = .049), V̇O2/t slope (r = -0.58, P = .03), and Schwachman score (r = -0.80, P = .001). In a multivariate regression model including all the above variables, the Schwachman score (β = -0.697, P = .002) emerged as independent predictor of tau (R2 = 0.719, P = .001).

CONCLUSIONS

We conclude that adult subjects with CF present significant prolonged oxygen kinetics during constant work load submaximal exercise in relation to disease severity. Thus, submaximal exercise should be considered the preferable CPET choice in adult patients with severe CF.

Changes in skeletal muscle microcirculation after a hemodialysis session correlates with adequacy of dialysis

Background

Monitoring of the microcirculation may add additional information in terms of improving the adequacy of hemodialysis (HD) for patients. Withdrawal of liquid and complement activation during a HD session reduces the external pressure on the microcirculation and leads to an increased dilatation of the peripheral capillaries. The purposes of this study were to assess the effect of a single HD or hemodiafiltration session on the thenar microcirculation in patients with end-stage renal disease (ESRD) with or without diabetes, investigate the possible relationship between changes in the microcirculation and adequacy of dialysis (including Kt/V and parameters indicating secondary hyperparathyroidism), and compare microcirculation measurements obtained from patients with ESRD and those from healthy controls.

Methods

This pilot prospective observational study including eleven patients with ESRD on maintenance HD (nine men of mean age 73±10.5 years, ten [91%] with hypertension), nine patients with ESRD on maintenance hemodiafiltration (six men of mean age 65.5±13.2 years, five [55.5%] with diabetes and four [44.5%] with hypertension), and eight healthy volunteers. Two paired microcirculation assessments were recorded for each HD patient before and after a dialysis session. Near infrared spectroscopy and the vascular occlusion test were used to assess the microcirculation, and blood work samples were collected before and after dialysis when the pump slowed down.

Results

Patients with ESRD showed an increase in thenar cell metabolism at rest after a 4-hour HD session, and changes in cell metabolism correlated with the Kt/V of the session. Pre-dialysis tissue oxygen saturation over the 4-hour HD session correlated with pre-dialysis serum calcium and parathyroid hormones. Vascular reactivity was lower in ESRD patients receiving HD or hemodiafiltration than in healthy controls.

Conclusion

Improvement in skeletal muscle microcirculation noted after a HD session was related to adequacy of dialysis. Evaluation of the microcirculation may provide additional information for management of patients on HD and identify novel targets for treatment. These preliminary findings need to be tested using a larger data set.

Attitudes towards euthanasia among Greek intensive care unit physicians and nurses

OBJECTIVES

To investigate the attitudes of Greek intensive care unit (ICU) medical and nursing staff towards euthanasia.

BACKGROUND

ICU physicians and nurses deal with end-of-life dilemmas on a daily basis. Therefore, the exploration of their stances on euthanasia is worthwhile.

METHODS

This was a descriptive quantitative study conducted in three ICUs in Athens. The convenience sample included 39 physicians and 107 nurses.

RESULTS

Of respondents, 52% defined euthanasia inaccurately, as withholding or withdrawal of treatment, while 15% ranked limitation of life-support among the several forms of euthanasia, together with active shortening of the dying process and physician - assisted suicide. Only one third of participants defined euthanasia correctly. While 59% of doctors and 64% of nurses support the legalization of active euthanasia, just 28% and 26% of them, respectively, agree with it ethically.

CONCLUSIONS

Confusion prevails among Greek ICU physicians and nurses regarding the definition of euthanasia. The majority of staff disagrees with active euthanasia, but upholds its legalization.

Lifestyle intervention and one-year prognosis of patients following open heart surgery: a randomised clinical trial

AIMS AND OBJECTIVES

To evaluate the one-year prognosis of a lifestyle counselling intervention (diet, smoking cessation and exercise) among patients who had open heart surgery.

BACKGROUND

Cardiovascular disease is the leading cause of morbidity worldwide in both developing and developed countries. Lifestyle modification plays an important role for patients who are at a high risk of developing cardiovascular disease and for those with an established cardiovascular disease.

DESIGN

Randomised, nonblind and lifestyle counselling intervention study with a one-year follow-up.

METHODS

A randomised, nonblind intervention study was performed on 500 patients who had open heart surgery. After hospital discharge, 250 patients (intervention group) were randomly allocated lifestyle counselling according to the recent guidelines provided by the European Society of Cardiology (European Journal Preventive Cardiology, 19, 2012, 585). The remaining 250 patients (control group) received the regular instructions. Primary end-point was the development of a cardiovascular disease (nonfatal event) during the first year; secondary end-points included fatal events, smoking abstinence, dietary habits and a physical activity evaluation.

RESULTS

According to the primary end-point, the odds of having a nonfatal cardiovascular disease event are 0·56-times (95%CI 0·28, 0·96, p = 0·03) lower for the intervention group compared to the control group. One-year after surgery, it was found that participants in the intervention group were 1·96-times (95%CI 1·31, 2·93, p < 0·001) more likely to achieve dietary recommendations, 3·32-times (95%CI 2·24, 4·91, p < 0·001) more likely to achieve physical activity recommendations and 1·34-times (95%CI 1·15, 1·56, p < 0·001) more likely to return to work.

CONCLUSION

Lifestyle counselling intervention following open heart surgery can improve health outcomes and reduce the risk of a new cardiac event. Health care services must recommend and organise well-structured cardiac rehabilitation programmes adjusted to the patient's needs.

RELEVANCE TO CLINICAL PRACTICE

A well-structured cardiac rehabilitation programme adjusted to the patient's profile is a safe and cost-effective way to improve patients' outcome.

Beneficial effects of combined exercise training on early recovery cardiopulmonary exercise testing indices in patients with chronic heart failure

PURPOSE

Exercise training induces several beneficial effects in patients with chronic heart failure (CHF). This study investigated the effects of high-intensity aerobic interval training (AIT) compared with combined AIT and strength training (COM) on early ventilatory and metabolic recovery pattern after symptom-limited cardiopulmonary exercise testing (CPET) in CHF patients.

METHODS

Stable CHF patients (N = 42; 54 ± 10 years [mean ± SD], 35 males) participated in an exercise training program for 12 weeks, 3 times per week. Participants were randomly assigned to either AIT (n = 20) or COM group (n = 22). Cardiopulmonary exercise testing was performed before and after completion of the program. Primary measurements included absolute and percentage difference of oxygen uptake, carbon dioxide output, minute ventilation ((Equation is included in full-text article.)E), tidal volume (VT), respiratory rate, and the first-degree slope of oxygen uptake ((Equation is included in full-text article.)O2/t slope) and carbon dioxide output ((Equation is included in full-text article.)CO2/t slope) during the first minute of recovery after maximal exercise.

RESULTS

The COM group had a greater improvement in the absolute and the percentage difference of (Equation is included in full-text article.)E (P = .03 and P = .04, respectively) and respiratory rate (P = .02 and P = .01, respectively) during the first minute of recovery period after exercise compared with the AIT group alone. No significant changes were noted for VT measurements. A significant increase in (Equation is included in full-text article.)CO2/t slope was observed in COM compared with the AIT group (P = .01). There was a trend for a greater increase in (Equation is included in full-text article.)O2/t slope in the COM group (P = .07).

CONCLUSIONS

The addition of strength training to AIT induces significant beneficial effects in terms of ventilatory and metabolic recovery kinetics than AIT alone in CHF patients, possibly indicating greater ventilatory efficiency and metabolic improvement.

Neuroticism personality trait is associated with Quality of Life in patients with Chronic Heart Failure

AIM: To evaluate Quality of life (QoL) in chronic heart failure (CHF) in relation to Neuroticism personality trait and CHF severity.

METHODS: Thirty six consecutive, outpatients with Chronic Heart Failure (6 females and 30 males, mean age: 54 ± 12 years), with a left ventricular ejection fraction ≤ 45% at optimal medical treatment at the time of inclusion, were asked to answer the Kansas City Cardiomyopathy Questionnaire (KCCQ) for Quality of Life assessment and the NEO Five-Factor Personality Inventory for personality assessment. All patients underwent a symptom limited cardiopulmonary exercise testing on a cycle-ergometer, in order to access CHF severity. A multivariate linear regression analysis using simultaneous entry of predictors was performed to examine which of the CHF variables and of the personality variables were correlated independently to QoL scores in the two summary scales of the KCCQ, namely the Overall Summary Scale and the Clinical Summary Scale.

RESULTS: The Neuroticism personality trait score had a significant inverse correlation with the Clinical Summary Score and Overall Summary Score of the KCCQ (r = -0.621, P < 0.05 and r = -0.543, P < 0.001, respectively). KCCQ summary scales did not show significant correlations with the personality traits of Extraversion, Openness, Conscientiousness and Agreeableness. Multivariate linear regression analysis using simultaneous entry of predictors was also conducted to determine the best linear combination of statistically significant univariate predictors such as Neuroticism, VE/VCO₂ slope and VO₂ peak, for predicting KCCQ Clinical Summary Score. The results show Neuroticism (β = -0.37, P < 0.05), VE/VCO₂ slope (β = -0.31, P < 0.05) and VO₂ peak (β = 0.37, P < 0.05) to be independent predictors of QoL. In multivariate regression analysis Neuroticism (b = -0.37, P < 0.05), the slope of ventilatory equivalent for carbon dioxide output during exercise, (VE/VCO₂ slope) (b = -0.31, P < 0.05) and peak oxygen uptake (VO₂ peak), (b = 0.37, P < 0.05) were independent predictors of QoL (adjusted R2 = 0.64; F = 18.89, P < 0.001).

CONCLUSION: Neuroticism is independently associated with QoL in CHF. QoL in CHF is not only determined by disease severity but also by the Neuroticism personality trait.

Resuscitation after cardiac arrest in a septic porcine model: adding vasopressin vs epinephrine alone administration

Background

Vasopressin administration has been tested in cardiac arrest. However it has not been tested when cardiac arrest occurs in certain circumstances, as in sepsis, where it may have a major role. The aim of the study was to investigate survival after cardiac arrest in a septic porcine model compared with healthy animals and to explore the effectiveness of adding vasopressin vs epinephrine alone administration.

Methods

Thirty five healthy piglets of both genders were studied. The piglets were randomly assigned into three groups: group A (n = 8), group B (n = 14), group C (n = 13). Animals of groups B and C were given endotoxin to mimic a septic state before arrest. We applied the same resuscitation protocol to all pigs but we replaced the first dose of epinephrine with vasopressin in pigs of group C. Following surgical preparation and 30 min resting period, baseline measurements were recorded. In order to assess tissue oxygenation, we implemented Near Infrared Spectroscopy (NIRS) with the vascular occlusion technique (VOT) in thirteen lipopolysaccharide (LPS)-treated animals, occluding abdominal aorta and inferior vena cava. Afterwards, LPS (100 μg/kg) was infused in a 30 min period to animals of groups B and C and normal saline to group A. New NIRS measurements were obtained again. Subsequently, we provoked ventricular fibrillation (VF). After 3 min of untreated VF, open chest cardiopulmonary resuscitation (CPR) was performed manually. Primary end point was the restoration of spontaneous circulation (ROSC).

Results

The chance of ROSC for the groups A, B and C was 75%, 35.7%, and 30.7% respectively. A significant difference in ROSC was established between septic (group B + C) and non septic piglets (group A) (P = 0.046). Vasopressin administration had no effect in outcome. LPS administration decreased oxygen consumption rate, as assessed by NIRS, in peripheral tissues (22.6 ± 7.2. vs 18.5 ± 7.2, P = 0.07).

Conclusion

Septic piglets have fewer chances to survive after cardiac arrest. No difference in outcome was observed when the first dose of epinephrine was replaced with vasopressin to treat cardiac arrest in the LPS-treated animals.

Changes in thenar muscle tissue oxygen saturation assessed by near-infrared spectroscopy during weaning from mechanical ventilation

BACKGROUND

Tissue oxygen saturation (StO₂) measured by near-infrared spectroscopy (NIRS) has been used to provide information on local tissue oxygenation in different clinical settings. This study aims to determine the effect of weaning from mechanical ventilation on thenar muscle StO₂.

METHODS

In consecutive critically ill mechanically ventilated patients, StO₂ at the thenar eminence, along with a vascular occlusion test (VOT), were measured by NIRS, on mechanical ventilation and during a 2-hour T-piece spontaneous breathing trial (SBT). Hemodynamic, gas exchange and respiratory variables were recorded.

RESULTS

Forty-four patients were included in this study, 25 tolerated the SBT and 19 failed. On mechanical ventilation, no differences in any measured variable were observed between patients who succeeded or failed. Two minutes after SBT start, StO₂ was decreased in patients who failed whereas it did not change in patients who succeeded (P<0.001). For all data, 2 minutes after the start of SBT, StO₂ significantly correlated with SaO₂ (r=0.32, P=0.037) and with the respiratory frequency/tidal volume (f/VT) index (r=-0.34, P=0.023). VOT-derived StO₂ downslope and StO2 upslope did not change significantly along the SBT test. The maximum StO₂ value, its ratio to minimum StO2, and the post-VOT StO₂ value decreased significantly in patients who failed whereas no change was found in those who succeeded the SBT (P=0.003, P=0.025 and P<0.001 respectively). StO₂ and f/VT at the second minute of SBT yielded a receiver operator characteristics curve area value of 0.77 and 0.80, P=0.002, respectively, in detecting the SBT outcome.

CONCLUSION

SBT failure was associated with a significant impairment of thenar muscle StO₂. A decrease of StO₂ at 2 minutes after disconnection from the ventilator was associated with SBT failure. Further validation is warranted.

Exercise intolerance in chronic heart failure: the role of cortisol and the catabolic state

Chronic heart failure (CHF) is a complex clinical syndrome leading to exercise intolerance due to muscular fatigue and dyspnea. Hemodynamics fail to explain the reduced exercise capacity, while a significant skeletal muscular pathology seems to constitute the main underlying mechanism for exercise intolerance in CHF patients. There have been proposed several metabolic, neurohormonal and immune system abnormalities leading to an anabolic/catabolic imbalance that plays a central role in the pathogenesis of the wasting process of skeletal muscle myopathy. The impairment of the anabolic axes is associated with the severity of symptoms and the poor outcome in CHF, whereas increased cortisol levels are predictive of exercise intolerance, ventilatory inefficiency and chronotropic incompetence, suggesting a significant contributing mechanism to the limited functional status. Exercise training and device therapy could have beneficial effects in preventing and treating muscle wasting in CHF. However, specific anabolic treatment needs more investigation to prove possible beneficial effects.

Prediction of the renal replacement therapy requirement in mechanically ventilated critically ill patients by combining biomarkers for glomerular filtration and tubular damage

PURPOSE

Mechanically ventilated critically ill patients with high severity score indices need a very cautious therapeutic approach. Considering that inappropriate decisions on renal replacement therapy (RRT) initiation may promote unwanted adverse effects, we evaluated whether a panel of novel and traditional renal markers is superior to conventional renal marker in predicting RRT requirements in this group of patients.

METHODS

This was a prospective observational study, performed at the two distinct multidisciplinary intensive care units (ICUs) of a 1000-bed tertiary hospital. Of 310 consecutive patients, 106 patients fulfilled the inclusion criteria of the study. Urinary neutrophil gelatinase-associated lipocalin (uNGAL), serum creatinine (sCr) and serum cystatin C (sCysC) were determined on ICU admission. The predictive performance of all markers for first RRT was tested and compared based on the area under the receiver operating characteristic (ROC) curves. Time-dependent ROC curves were used to assess the earlier time point where the markers presented their maximum area under the curve (AUC).

RESULTS

All studied biomarkers and acute physiology and chronic health evaluation (APACHE) II score, were significant independent predictors of RRT (uNGAL-AUC=0.73, sCysC-AUC=0.76, sCr-AUC=0.78, APACHE-AUC=0.73, P<0.0001). sCysC and sCr showed early maximum predictive ability within 10 days of ICU admission, while uNGAL and APACHE II score within 11 days of ICU admission. sCr combined with normalized (n)NGAL and sCysC combined with either nNGAL or uNGAL established best predictors for the RRT initiation (AUC-ROC=0.8). Distinguishing patients without acute kidney injury (AKI) on ICU entry, the combination of sCysC and APACHE II score proved best (AUC-ROC=0.78).

CONCLUSIONS

Specific markers of kidney dysfunction and of kidney damage can be successfully combined to increase the prognostic capability for RRT initiation. The presence of AKI affects diagnostic performance. Without an established AKI on ICU admission, future RRT requirement was better predicted by the combination of illness severity with a marker of glomerular filtration rate. With AKI on ICU admission a combination of the marker of glomerular filtration rate with one of tubular injury proved best.

Glutamine suppresses Hsp72 not Hsp90α and is not inducing Th1, Th2, or Th17 cytokine responses in human septic PBMCs

OBJECTIVE

L-Alanyl-glutamine (L-Ala-Gln) is a pharmaco-nutrient commonly used in nutrition regimens due to its immunomodulatory effects. In critically ill patients who are septic, L-Ala-Gln was associated with an increase in mortality. The aim of this study was to investigate whether L-Ala-Gln modulated heat shock protein (Hsp)-72, 90-α, T helper (Th)1, Th2, and Th17 cytokine expression in the peripheral blood mononuclear cells (PBMC) of patients with severe sepsis.

METHODS

Time-dose effects of L-Ala-Gln were compared with those of L-glutamine (L-Gln) and lipopolysaccharide (LPS) and to healthy controls. PBMCs were incubated with 1 or 10 μg/mL LPS, 5 or 10 mM L-Gln, and 5 or 10 mM L-Ala-Gln for different periods of time (0; 4; 24 h) when culture supernatants were harvested.

RESULTS

In both groups, basal Hsp72 increased over time (P < 0.02); Hsp90-α levels declined in controls (P < 0.02) but remained increased in septic patients (P < 0.02), not exhibiting any significant time-response trend. Both Glns suppressed Hsp72 in septic and controls at 10 mM by 4 h (P < 0.045) and Hsp90-α in the control group by 24 h (P < 0.045). LPS did not induce Hsps in either group. L-Ala-Gln did not induce any of the Th1, Th2, and Th17 cytokines in either group.

CONCLUSION

High doses of L-Gln or L-Ala-Gln do not induce any of the Th1, Th2, and Th17 cytokines in either healthy or septic human PBMCs. High Gln doses suppress Hsp72 in septic and control PBMCs. Hsp90-α time-series expression declines, contrasting the increasing trend of Hsp72 in healthy controls. Hsp90-α sustains increased levels in septic supernatants, showing a characteristic longitudinal behavior needed further elucidation.

Respiratory drive and breathing pattern abnormalities are related to exercise intolerance in chronic heart failure patients

BACKGROUND

Patients with chronic heart failure (CHF) are characterized by exercise intolerance and ventilatory abnormalities that are related to poor prognosis. We hypothesized that CHF patients have increased respiratory drive and abnormal breathing pattern during exercise in relation to disease severity.

MATERIALS AND METHODS

The study population consisted of 219 stable CHF patients and 30 healthy control subjects. All subjects underwent a symptom-limited cardiopulmonary exercise testing (CPET), pulmonary function tests, measurement of the maximal inspiratory pressure (PImax) and respiratory drive (P0.1). Measurements included peak oxygen uptake ( [Formula: see text] peak, ml/kg/min). Respiratory drive was measured by mouth occlusion pressure P0.1 and P0.1/PImax ratio at rest, and by mean inspiratory flow (VT/TI) at rest and during exercise. CHF patients were divided into 3 groups according to [Formula: see text] peak (Group A: >20, Group B: 20-16 and Group C: <16ml/kg/min).

RESULTS

CHF patients presented higher P0.1/PImax (4.1±3.6 vs 3.0±1.5, p=0.007) and VT/TI at rest (0.48±0.14 vs 0.41±0.10, L/s respectively, p=0.004) and lower VT/TI at peak exercise (2.17±0.66 vs 2.56±0.73, L/s, p=0.009) compared to controls. P0.1/PImax was higher in CHF Group C vs B vs A (4.9±2.9 vs 3.6±1.8 vs 3.1±1.8, respectively, p<0.001), while VT/TI at peak exercise was lower (1.71±0.43 vs 2.15±0.52 vs 2.65±0.64, L/s, respectively, p<0.001).

CONCLUSIONS

CHF patients present increased respiratory drive at rest and abnormal breathing pattern during exercise in relation to CHF severity.

Peripheral muscle microcirculatory alterations in patients with pulmonary arterial hypertension: a pilot study

BACKGROUND

Pulmonary microcirculation abnormalities are the main determinants of pulmonary arterial hypertension (PAH) pathophysiology. We hypothesized that PAH patients have peripheral tissue microcirculation alterations that might benefit from hyperoxic breathing. We evaluated peripheral muscle microcirculation with near-infrared spectroscopy, before and after hyperoxic breathing.

METHODS

Eight PAH subjects, 8 healthy subjects (controls) matched for age, sex, and body mass index, and 16 subjects with chronic heart failure and matched for functional capacity with the PAH subjects underwent near-infrared spectroscopy. Tissue O(2) saturation, defined as the hemoglobin saturation (%) in the microvasculature compartments, was measured on the thenar muscle. Then the 3-min brachial artery occlusion technique was applied before, during, and after 15 min of breathing 100% O(2). We calculated the oxygen consumption rate (%/min), the reactive hyperemia time, and the time needed for tissue O(2) saturation to reach its baseline value after the release of the occlusion.

RESULTS

Compared to the controls, the PAH subjects had a significantly lower resting tissue O(2) saturation (65.8 ± 14.9% vs 82.1 ± 4.0%, P = .005), a trend toward a lower oxygen consumption rate (35.3 ± 9.1%/min vs 43.4 ± 19.7%/min, P = .60), and a significantly higher reactive hyperemia time (3.0 ± 0.6 min vs 2.0 ± 0.3 min, P < .001). The PAH subjects also had lower tissue O(2) saturation (P = .08), lower peripheral arterial oxygen saturation (P = .01), and higher reactive hyperemia time (P = .02) than the chronic heart failure subjects. After hyperoxic breathing, the PAH subjects had increased tissue O(2) saturation (65.8 ± 14.9% to 71.4 ± 14.5%, P = .01), decreased oxygen consumption rate (35.3 ± 9.1%/min to 25.1 ± 6.6%/min, P = .01), and further increased reactive hyperemia time (3.0 ± 0.6 min to 4.2 ± 0.7 min, P = .007).

CONCLUSIONS

The PAH subjects had substantial impairments of peripheral muscle microcirculation, decreased tissue O(2) saturation (possibly due to hypoxemia), slower reactive hyperemia time, (possibly due to endothelium dysfunction), and peripheral systemic vasoconstriction. Acute hyperoxic breathing improved resting tissue O(2) saturation (an expression of higher oxygen delivery) and decreased the oxygen consumption rate and reactive hyperemia time during reperfusion, possibly due to increased oxidative stress and evoked vasoconstriction.