Effects of acute hypoxic provocation on the autonomic nervous system in 'healthy' young smokers, measured by heart rate variability.

AIM: The aim of this study was to compare the activity of the autonomic nervous system (ANS) using heart rate variability (HRV) in 'healthy' young smokers and non-smokers before, during and after exogenous hypoxic provocation. METHODS: Twenty-one healthy non-smoking males aged 28.0 ± 7.4 years (mean ± SD) and 14 'healthy' smoking males aged 28.1 ± 4.3 years with 9.2 ± 5.6 pack-years were subjected to one-hour hypoxic exposure (FiO2 = 12.3 ± 1.5%) via a hypoxicator. HRV data was derived via Kubios HRV, Finland software by analysing the pre-hypoxic, hypoxic and post-hypoxic periods. RESULTS: Standard deviation of the intervals between normal beats (SDNN) was higher in the non-smokers in the pre-hypoxic period (62.0 ± 32.1 vs 40.3 ± 16.2 ms, p = 0.013) but not in the hypoxic period (75.7 ± 34.8 vs 57.9 ± 18.3 ms, p = 0.167). When comparing intra-group HRV changes, shifting from hypoxic to normoxic conditions, there was an increase in the mean square root of successive R-R interval differences (RMSSD) (65.9 ± 40.2 vs 75.1 ± 45.9 ms, p = 0.011), but these changes were observed in only the group of non-smokers. CONCLUSIONS: Smoking probably impairs autonomic regulation in healthy young males and may lead to decreased HRV, even before subjective clinical signs and symptoms appear.

Response to Pharmacological Treatment in Major Depression Predicted by Electroencephalographic Alpha Power - a Pilot Naturalistic Study.

BACKGROUND: Pharmacological treatment of depression is currently led by the trial and error principle mainly because of lack of reliable biomarkers. Earlier findings suggest that baseline alpha power and asymmetry could differentiate between responders and non-responders to specific antidepressants. AIM: The current study investigated quantitative electroencephalographic (QEEG) measures before and early in treatment as potential response predictors to various antidepressants in a naturalistic sample of depressed patients. We were aiming at developing markers for early prediction of treatment response based on different QEEG measures. MATERIALS AND METHODS: EEG data from 25 depressed subjects were acquired at baseline and after one week of treatment. Mean and total alpha powers were calculated at eight electrode sites F3, F4, C3, C4, P3, P4, O1, O2. Response to treatment was defined as 50% decrease in MADRS score at week 4. RESULTS: Mean P3 alpha predicted response with sensitivity and specificity of 80%, positive and negative predictive values of 92.31% and 71.43%, respectively. The combined model of response prediction using mean baseline P3 alpha and mean week 1 C4 alpha values correctly identified 80% of the cases with sensitivity of 84.62%, and specificity of 71.43%. CONCLUSIONS: Simple QEEG measures (alpha power) acquired before initiation of antidepressant treatment could be useful in outcome prediction with an overall accuracy of about 80%. These findings add to the growing body of evidence that alpha power might be developed as a reliable biomarker for the prediction of antidepressant response.

The effect of continuous positive airway pressure on heart rate variability during the night in patients with chronic heart failure and central sleep apnoea.

Continuous positive airway pressure (CPAP) improves autonomic activity in patients with chronic heart failure (CHF) and central sleep apnoea (CSA), but its effect on heart rate variability (HRV) during therapy has not been reported. We hypothesized that CPAP may decrease HRV, despite its beneficial effects on sympathetic overactivation, due to the expected stabilization of breathing. Sixty-seven CHF patients underwent polysomnography (PSG). Ten of them presented with CSA (age 66.1±8.5 years, apnoea-hypopnea index [AHI]=57.6±23.3, central AHI [cAHI]=41.6±24.6 [mean±SD]) and were subjected to a second PSG with manual CPAP titration. Beat-to-beat heart intervals for a 6-hour period of sleep were extracted from each recording and HRV was analysed. CPAP significantly reduced AHI (AHI=23.1±18.3 P=.004). Standard deviation of normal-normal interbeat interval (SDNN) (61.5±29.0 vs 49.5±19.3 ms, P=.021), root mean square of successive differences (RMSSD) (21.8±9.2 vs 16.4±7.1 ms, P=.042), total power (lnTP=7.8±1.1 vs 7.4±0.8 ms2 , P=.037), low frequency power (lnLF=5.5±1.5 vs 5.0±1.4 ms2 , P=.003) and high frequency power (lnHF=4.6±1.0 vs 4.0±1.0 ms2 , P=.024) were decreased. There was a strong correlation between the decrease in AHI and the decrease in lnHF (Spearman's ρ=.782). CPAP leads to a decrease in spectral and time domain parameters of HRV during therapy in CHF patients with CSA. These changes are best explained by the effect which CPAP-influenced breathing pattern and lowered AHI exert on HRV.

Identifying Predictors of Central Sleep Apnea/Cheyne-Stokes Breathing in Chronic Heart Failure: a Pathophysiological Approach.

Chronic heart failure (CHF) is a major health problem associated with increased mortality, despite modern treatment options. Central sleep apnea (CSA)/Cheyne-Stokes breathing (CSB) is a common and yet largely under-diagnosed co-morbidity, adding significantly to the poor prognosis in CHF because of a number of acute and chronic effects, including intermittent hypoxia, sympathetic overactivation, disturbed sleep architecture and impaired physical tolerance. It is characterized by repetitive periods of crescendo-decrescendo ventilatory pattern, alternating with central apneas and hypopneas. The pathogenesis of CSA/CSB is based on the concept of loop gain, comprising three major components: controller gain, plant gain and feedback gain. Laboratory polysomnography, being the golden standard for diagnosing sleep-disordered breathing (SDB) at present, is a costly and highly specialized procedure unable to meet the vast diagnostic demand. Unlike obstructive sleep apnea, CSA/CSB has a low clinical profile. Therefore, a reliable predictive system is needed for identifying CHF patients who are most likely to suffer from CSA/CSB, optimizing polysomnography use. The candidate predictors should be standardized, easily accessible and low-priced in order to be applied in daily medical routine. The present review focuses on a pathophysiological approach to the selection of some predictors based on parameters reflecting the etiology, the pathogenesis and the consequences of CSA/CSB in CHF.

Heart Rate Variability as a Method for Assessment of the Autonomic Nervous System and the Adaptations to Different Physiological and Pathological Conditions.

The autonomic nervous system controls the smooth muscles of the internal organs, the cardiovascular system and the secretory function of the glands and plays a major role in the processes of adaptation. Heart rate variability is a non-invasive and easily applicable method for the assessment of its activity. The following review describes the origin, parameters and characteristics of this method and its potential for evaluation of the changes of the autonomic nervous system activity in different physiological and pathological conditions such as exogenous hypoxia, physical exercise and sleep. The application of heart rate variability in daily clinical practice would be beneficial for the diagnostics, the outcome prognosis and the assessment of the effect of treatment in various diseases.

Oxygen uptake efficiency slope and chronotropic incompetence in chronic heart failure and chronic obstructive pulmonary disease.

INTRODUCTION: Oxygen uptake efficiency slope (OUES) and chronotropic index (CRI) are measures of cardiorespiratory reserve and chronotropic incompetence, but no direct comparison of OUES and CRI in patients with chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF) has been done. AIM: To compare OUES and CRI in CHF and COPD patients. PATIENTS: Fifty-one subjects divided in three groups--CHF group (n=17) (NYHA II and III functional class), COPD group (n=17) (FEV1% = 49.7 +/- 17.3) and healthy controls (C) (n=17), matched by age and BMI. COPD and CHF patients presented comparable decrease in functional capacity. METHODS: Subjects undertook maximal exercise test on a treadmill by means of Bruce protocol. RESULTS: CHF and COPD patients showed a significant and comparable decrease in exercise capacity (VO2/kg = 18.5 +/- 4.0 vs. 19.5 +/- 4.9 vs. 28.3 +/- 6.2 mL x min(-1) x kg(-1), p < 0.001) and ventilatory efficiency in comparison with controls. COPD patients presented with a typical pattern of exercise limitation due to ventilatory restraints (%breathing reserve = 15.6 +/- 18.0%). OUES was lower than controls in both CHF and COPD groups, being lowest in CHF (1686 +/- 483 vs. 2101 +/- 478 vs. 2481 +/- 398 mL.min(-1) x logL(-1), p < 0.001). Chronotropic index was lower in CHF patients (0.60 +/- 0.15 in CHF vs. 0.72 +/- 0.16 in COPD vs. 0.81 +/- 0.18 in controls, p < 0.001) in comparison with controls. CONCLUSION: OUES is decreased in CHF and COPD patients, but the decline is significantly more pronounced in the CHF group. CRI is lower in CHF patients.

Exercise performance in children with severe beta-thalassemia before and after transfusion.

UNLABELLED: Thalassemia major is associated with impaired exercise tolerance because of the severe anemia and cardiopulmonary dysfunction characteristic of the condition. OBJECTIVE: To assess the exercise performance in thalassemic children before and two hours after hemotransfusion. PATIENTS AND METHODS: The study included eleven children with thalassemia major (12.3 +/- 2.8 years; Hb g/dl = 8.1 +/- 1.3) and 11 matched controls. All subjects underwent comprehensive pulmonary function assessment and incremental exercise test on a treadmill. RESULTS: The thalassemic children were, in general, shorter and lighter than their healthy counterparts; we also found lower absolute values of lung function parameters which did not reach statistical significances. On the other hand the most considerable differences were found in diffusion capacity (uncorrected TL(L,CO) % = 56.8 +/- 12.1 vs. 94.3 +/- 16.1 in controls; p<0.001) and blood oxygen content (ctO2 mmol.L(-1) = 4.7 +/- 1.1 vs. 8.3 +/- 0.8, p<0.05). The thalassemic children had significantly lower exercise capacity compared to controls (VO2/ kg = 27.1 +/- 5.0 vs. 37.1 +/- 3.2 mL.min(-1).kg(-1); p<0.001). In the patients' group hemoglobin was elevated significantly two hours after transfusion (Hb g/L from 80.5 +/- 12.7 to 93.6 +/- 10.6; p<0.001) leading to significant improvement in exercise duration (7.3 +/- 2.8 vs. 10.3 +/- 2.3 min; p<0.05), VO2/kg (28.5 +/- 5.0 vs. 36.2 +/- 7.1 mL.min(-1).kg(-1); p<0.05), and transfer factor (4.27 +/- 1.40 vs. 5.41 +/- 1.08 mmol.min(-1).kPa(-1); p=0.003). There were strong correlations between Hb and TL(L,CO) and VO2 (r = 0.687 and 0.750, respectively; p < 0.01 for both). CONCLUSIONS: Patients with thalassemia major have a seriously reduced transfer factor and exercise impairment. The short-term changes in hemoglobin concentration are associated with significant improvement in exercise performance.