Principal component analysis as a novel approach for cardiorespiratory exercise testing evaluation.

OBJECTIVE: Our purpose was to apply a principal component analysis (PCA) approach to cardiorespiratory exercise to test evaluation and its sensitivity to workload accumulation. APPROACH: Twenty-five healthy young adults performed a progressive and maximal cycling test, which was divided into two parts: moderate and high workload intensities, using a ventilatory threshold as a cut point. A PCA of the time series of cardiovascular and respiratory variables was performed in each part and the number of principal components (PCs), the eigenvalues of the first PC (PC1), and the information entropy were calculated. MAIN RESULTS: The number of PCs increased, the eigenvalues of PC1 decreased (t = 5.32; p  < 0.001; d = 1.39) and entropy was significantly higher (Z = 3.10; p  = .002; d = 1.16) at high workload intensities, compared to moderate intensities. SIGNIFICANCE: Results showed the sensitivity of the PCA approach to workload accumulation and corroborates its potential for improving the evaluation and interpretation of cardiorespiratory exercise testing. In particular, it points to being a good candidate to objectively detect qualitative changes or thresholds.

Combined intermittent hypobaric hypoxia and muscle electro-stimulation: a method to increase circulating progenitor cell concentration?

BACKGROUND: Our goal was to test whether short-term intermittent hypobaric hypoxia (IHH) at a level well tolerated by healthy humans could, in combination with muscle electro-stimulation (ME), mobilize circulating progenitor cells (CPC) and increase their concentration in peripheral circulation. METHODS: Nine healthy male subjects were subjected, as the active group (HME), to a protocol involving IHH plus ME. IHH exposure consisted of four, three-hour sessions at a barometric pressure of 540 hPa (equivalent to an altitude of 5000 m). These sessions took place on four consecutive days. ME was applied in two separate 20-minute periods during each IHH session. Blood samples were obtained from an antecubital vein on three consecutive days immediately before the experiment, and then 24 h, 48 h, 4 days, 7 days and 14 days after the last day of hypoxic exposure. Four months later a control study was carried out involving seven of the original subjects (CG), who underwent the same protocol of blood samples but without receiving any special stimulus. RESULTS: In comparison with the CG the HME group showed only a non-significant increase in the number of CPC CD34+ cells on the fourth day after the combined IHH and ME treatment. CONCLUSION: CPC levels oscillated across the study period and provide no firm evidence to support an increased CPC count after IHH plus ME, although it is not possible to know if this slight increase observed is physiologically relevant. Further studies are required to understand CPC dynamics and the physiology and physiopathology of the hypoxic stimulus.

Short-term independent mortality risk factors in patients with cirrhosis undergoing cardiac surgery.

OBJECTIVES: Cirrhosis represents a serious risk in patients undergoing cardiac surgery. Several preoperative factors identify cirrhotic patients as high risk for cardiac surgery; however, a patient's preoperative status may be modified by surgical intervention and, as yet, no independent postoperative mortality risk factors have been identified in this setting. The objective of this study was to identify preoperative and postoperative mortality risk factors and the scores that are the best predictors of short-term risk. METHODS: Fifty-eight consecutive cirrhotic patients requiring cardiac surgery between January 2004 and January 2009 were prospectively studied at our institution. Forty-two (72%) patients were operated on for valve replacement, 9 (16%) for a CABG and 7 (12%) for both (CABG and valve replacement). Thirty-four (58%) patients were classified as Child-Turcotte-Pugh class A, 21 (36%) as class B and 3 (5%) as class C. We evaluated the variables that are usually measured on admission and during the first 24 h of the postoperative period together with potential operative predictors of outcome, such as cardiac surgery scores (Parsonnet, EuroSCORE), liver scores (Child-Turcotte-Pugh, model for end-stage liver disease, United Kingdom end-stage liver disease score) and ICU scores (acute physiology and chronic health evaluation II and III, simplified acute physiology score II and III, sequential organ failure assessment). RESULTS: Seven patients (12%) died in-hospital, of whom 5 were Child-Turcotte-Pugh class B and 2 class C. Comparing survivors vs non-survivors, univariate analysis revealed that variables associated with short-term outcome were international normalized ratio (1.5 ± 0.24 vs 2.2 ± 0.11, P < 0.0001), presurgery platelet count (171 ± 87 vs 113 ± 52 l nl(-1), P = 0.031), presurgery haemoglobin count (11.8 ± 1.8 vs 10.2 ± 1.4 g dl(-1), P = 0.021), total need for erythrocyte concentrates (2 ± 3.4 vs 8.5 ± 8 units, P < 0.0001), PaO(2)/FiO(2) at 12 h after ICU admission (327 ± 84 vs 257 ± 78, P = 0.04), initial central venous pressure (11 ± 3 vs 16 ± 4 mmHg, P = 0.02) and arterial blood lactate concentration 24 h after admission (1.8 ± 0.5 vs 2.5 ± 1.3 mmol l(-1), P = 0.019). Multivariate analysis identified initial central venous pressure as the only independent factor associated with short-term outcome (P = 0.027). The receiver operating characteristic curve showed that the model for end-stage Liver disease score had a better predictive value for short-term outcome than other scores (AUC: 90.5 ± 4.4%; sensitivity: 85.7%; specificity: 83.7%), although simplified acute physiology score III was acceptable. CONCLUSIONS: We conclude that central venous pressure could be a valuable predictor of short-term outcome in patients with cirrhosis undergoing cardiac surgery. The model for end-stage liver disease score is the best predictor of cirrhotic patients who are at high risk for cardiac surgery. Sequential organ failure assessment and simplified acute physiology score III are also valuable predictors.

Respuesta respiratoria al ejercicio físico de baja intensidad en mujeres con síndrome de fatiga crónica / Respiratory response to low-intensity physical exercise in women with chronic fatigue syndrome

IntroducciónEl objetivo del estudio fue evaluar los parámetros cardiorrespiratorios en condiciones de reposo y la respuesta durante ejercicio físico a muy baja intensidad en mujeres con síndrome de fatiga crónica (SFC).Material y métodosUn grupo de 141 mujeres afectadas por el SFC se comparó con un grupo control (C) de 20 mujeres en condiciones de reposo y durante 4min de ejercicio constante en un cicloergómetro sin carga de trabajo (carga de trabajo=0 W).ResultadosSe encontraron diferencias significativas durante el ejercicio: el cociente respiratorio (SFC=0,9±0,09, C=0,8±0,08; p<0,05), equivalente respiratorio para el oxígeno (SFC=34,6±10,1, C=28,0±3,4; p<0,01) y el dióxido de carbono (SFC=37,9±7,7; C=33,4±3,8; p=0,01). Se observaron diferencias en la frecuencia cardíaca durante el período de descanso (SFC=86,8±14,2 lpm−1, C=79,8±8,4lpm−1; p=0,03). No hubo diferencias significativas en la percepción del esfuerzo realizado durante el descanso (SFC=10,3±3,0, C=6,2±0,6; p<0,001) y justo después del ejercicio (SFC=12,5±2,8, C=6,8±1,4; p<0,01).ConclusionesSe concluye que las mujeres con SFC tienen menos eficiencia ventilatoria que las del C durante el esfuerzo físico a baja intensidad. Este aspecto podría ser mejorado a través de programas específicos de rehabilitación(AU)

IntroductionThe aim of the study was to evaluate the cardiorespiratory parameters at rest and and as the response to very low intensity physical exercise in women with chronic fatigue syndrome (CFS).Material and methodsA group of 141 women suffering from chronic fatigue synrdrome (CFS) were compared with a control group (C) of 20 women while at rest and during 4 minutes of constant exercise on a cycloergometer with no work load (work load=0 watts).ResultsSignificant differences were found during the exercise: respiratory quotient (CFS=0.9±0.09, C=0.8±0.08, p<0.05); the respiratory equivalent for oxygen (CFS=34.6±10.1, C=28.0±3.4, p<0.01) and for carbon dioxide (CFS=37.9±7.7, C=33.4±3.8, p=0.01). Differences were observed in the heart rate during the rest period (CFS=86,8±14,2 beatsmin−1, C=79.8±8.4 beatsmin−1, p=0.03). There were no significant differences in the perception of effort made during rest (CFS=10.3±3.0. C=6.2±0.6, p<0.001) and just after exercise (CFS=12.5±2.8, C=6.8±1.4, p<0.01).ConclusionsIt was concluded that women with chronic fatigue syndrome had less ventilatory efficiency than the controls during low intensity physical exercise. This condition could be improved through specific rehabilitation programs(AU)

Combined intermittent hypoxia and surface muscle electrostimulation as a method to increase peripheral blood progenitor cell concentration.

BACKGROUND: Our goal was to determine whether short-term intermittent hypoxia exposure, at a level well tolerated by healthy humans and previously shown by our group to increase EPO and erythropoiesis, could mobilize hematopoietic stem cells (HSC) and increase their presence in peripheral circulation. METHODS: Four healthy male subjects were subjected to three different protocols: one with only a hypoxic stimulus (OH), another with a hypoxic stimulus plus muscle electrostimulation (HME) and the third with only muscle electrostimulation (OME). Intermittent hypobaric hypoxia exposure consisted of only three sessions of three hours at barometric pressure 540 hPa (equivalent to an altitude of 5000 m) for three consecutive days, whereas muscular electrostimulation was performed in two separate periods of 25 min in each session. Blood samples were obtained from an antecubital vein on three consecutive days immediately before the experiment and 24 h, 48 h, 4 days and 7 days after the last day of hypoxic exposure. RESULTS: There was a clear increase in the number of circulating CD34+ cells after combined hypobaric hypoxia and muscular electrostimulation. This response was not observed after the isolated application of the same stimuli. CONCLUSION: Our results open a new application field for hypobaric systems as a way to increase efficiency in peripheral HSC collection.

Heritability of explosive power and anaerobic capacity in humans.

There is a disparity in the information about the heritability of the response of muscle anaerobic metabolism to exercise and the use of explosive power, as well as a lack of information concerning the genetic determinants of this form of work, as measured using different specific physical tests. We applied a battery of some of the commonly employed procedures (Ergojump, Wingate, maximal accumulated oxygen deficit, excess post-exercise oxygen consumption, and delta lactate concentration) to a group of 32 Caucasian male twins, 8 monozygotic and 8 dizygotic pairs, who had similar environmental backgrounds. Results were studied using a heritability index (HI). Zygosity was determined using the identity of erythrocyte antigens, protein and enzyme polymorphism and human leucocyte antigen serologic types between co-twins. Significant HI values (P< 0.05) were found in the following tests: maximal 5 s power (HI = 0.74) and total power in a 30 s interval (HI = 0.84) in the Wingate test, maximal lactate concentration (HI = 0.82) and delta lactate concentration (HI = 0.84) in the maximal progressive test, as well as in the 2nd (HI = 0.93) and in the 3rd min (HI = 0.92) of recovery after the deficit test. In this study, the most relevant findings were: firstly, significant HI values for many of the variables studied; secondly, the HI values of the parameters used to evaluate explosive power were higher than those of lactic acid capacity and thirdly, the HI of certain variables from different tests measuring, in theory, similar qualities, were different.