Kiril Terziyski

EXERCISE PERFORMANCE AND VENTILATORY EFFICIENCY IN PATIENTS WITH MILD AND MODERATE LIVER CIRRHOSIS

1 The impact of ventilatory efficiency on reduced exercise capacity and recovery oxygen kinetics has not been addressed in cirrhotic patients. The aim of the present study was to investigate exercise performance and ventilatory efficiency in patients with mild and moderate liver cirrhosis (LC). 2 Nineteen male non‐hypoxic patients with LC (age 51.3 ± 9.1 years; body mass index (BMI) 25.6 ± 3.6 kg/m2) classified by the Child‐Pugh score as class A (n = 7) and class B (n = 12) and 19 age‐ and BMI‐matched controls participated in the study. Subjects undertook maximal incremental exercise testing on a treadmill using the Bruce protocol. 3 Patients with LC showed a reduced diffusion capacity (DL,CO%) compared with controls (74.6 ± 15.2 vs 95.6 ± 12.9%, respectively; P < 0.001), but a comparable volume standardized diffusion coefficient (1.33 ± 0.22 vs 1.45 ± 0.18 mmol/min per kPa per L, respectively; P = 0.74). Patients with LC had a significantly lower exercise capacity compared with controls (VO2max 23.8 ± 3.8 vs 30.6 ± 4.4 mL/min per kg, respectively; P < 0.001).  Recovery oxygen kinetics were also impaired in LC patients compared with controls (104.6 ± 19.3 vs 84.4 ± 22.7 s, respectively; P = 0.012). The chronotropic index was significantly lower in the LC group compared with controls (0.67 ± 0.19 vs 0.82 ± 0.17, respectively; P = 0.030) and LC patients showed higher ventilatory equivalents (30.4 ± 3.8 vs 26.3 ± 2.3, respectively; P < 0.001) and lower oxygen uptake efficiency slope values (2187 ± 445 vs 2745 ± 473 mL/min per log10L, respectively; P < 0.001) compared with controls, which is indicative of decreased ventilatory efficiency. Patients with LC also had a higher standardized maximal exercise perception score (SMEPS) compared with controls (0.62 ± 0.18 vs 0.46 ± 0.15, respectively; P = 0.011). Moderate negative correlations were found between Child‐Pugh score and VO2max% (r = –0.496; P = 0.031). 4 In conclusion, patients with mild and moderate LC have reduced exercise capacity, which correlates with Child‐Pugh score, as well as reduced chronotropic index and prolonged recovery oxygen uptake kinetics. The results suggest worsened ventilatory efficiency during exercise and cardiopulmonary reasons for the higher SMEPS in these patients.

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

Abstract 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.

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

Abstract 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 (Spearmans 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.

Effects of Acute Hypoxic Provocation on Autonomic Nervous System in Young “Healthy” Smokers Measured by Heart Rate Variability

Background and objectives: Smoking leads to autonomic dysfunction. However, the clinical methods for diagnosing this dysfunction are not sufficient. Since exogenous hypoxia leads to changes in the autonomic cardiac control, the aim of our study was to compare the activity of the autonomic nervous system via heart rate variability (HRV) in young “healthy” smokers and non-smokers before, during and after a short-term exogenous hypoxic exposure. Methods: Twenty-one healthy non-smoking males aged 28.0±7.4 (mean±SD) and fourteen healthy smoking males aged 28.1±4.3 with 9.2±5.6 pack-years were subjected to one-hour hypoxic exposure (FiО2=12.3±1.5%) via hypoxicator (AltiPro 8850 Summit+, Altitude Tech, Canada) with simultaneous recording of electrocardiography and pulse oximetry. HRV data was derived via specific software (Kubios HRV, Finland) by analyzing the pre-hypoxic, hypoxic and post-hypoxic periods. Results: Standard deviation of the intervals between normal beats (SDNN) was higher in non-smokers in the pre-hypoxic period (62.0±32.1 vs 40.3±16.2, p=0.013) but not in hypoxia (75.7±34.8 vs 57.9±18.3, p=0.167). When comparing intragroup HRV changes of shifting from hypoxic to post-hypoxic (normoxic) conditions we found that there is a significant increase in the root mean square of successive RR interval differences (RMSSD) (65.9±40.2 vs 75.1±45.9, p=0.011) and in the high frequency (lnHF) (6.8±1.4 vs 7.2±1.3, p=0.014) and a decrease in LF/HF (3.0±2.3 vs 1.9±1.5, p<0.001), but these changes were observed only in the group of non-smokers. Conclusions: Smoking likely impairs autonomic regulation in young healthy males and may lead to a decreased HRV even before subjective clinical signs and symptoms. Hypoxic exposure test could be Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 20 June 2018 doi:10.20944/preprints201806.0325.v1

Effects of individually constructed oral appliance on the polysomnographic parameters in patients with obstructive sleep apnea

https://www.journal-imab-bg.org J of IMAB. 2018 Apr-Jun;24(2) ABSTRACT Background: Obstructive sleep apnea (OSA) is a common sleep disorder, associated with disturbed noxturnal oxygenation profile and altered sleep structure, associated with significant health problems. Oral appliances (OA) are used as an alternative therapeutic option for patients with mild to moderate OSA. Although the application of OA does not always result in a complete resolution of the sleepdisordered breathing, greater patient adherence is demonstrated. We have decided to evaluate the effect of individually constructed OA on sleep disordered breathing and sleep structure in patients with OSA. Materials and methods: 20 patients (18 men) with OSA (age 46.3±8.1 years (mean±SD), body mass index 29.0±4.8 kg.m-2) were subjected to a full-night polysomnography (PSG), at baseline and one month after the introduction of an OA. Results: A significant decrease in AHI (33.4±31.1 vs 45.5±30.8, p<0.001), hypopnea index (10.3±9.1 vs 18.2±11.0, p=0.023), mean duration of apneas (20.9±6.9 vs 24.1±6.4 sec, p=0.005) and average desaturation (5.6±2.4 vs 8.5±3.0 %, p<0.001), after therapy and at baseline, respectively, was registered. Sleep structure was improved as indicated by an increase in REM (16.1±6.2vs 12.3±8.2 % of total sleep time, p=0.016) and a decrease in arousal index (31.0±14.2 vs 46.4±12.0, p<0.001). Conclusion: OA is a reasonable alternative for the treatment of patients with moderate and severe OSA, resulting in an improvement of the polysomnographic parameters and expressed by excellent patient compliance.

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

Abstract 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.

Exercise recovery phase: unrecovered part of the recommendations

To the Editors: As the implications of cardiopulmonary exercise testing (CPET) are continually growing, Palange et al. 1 are to be congratulated for their paper entitled “Recommendations on use of exercise testing in clinical practice”. It has been long awaited, as extensive research in the area simply outdated previous European 2 and American guidelines 3. As Palange et al. 1 mentioned that assessment requires integrative interpretation of a “cluster of response variables”, it seemed surprising that no parameter describing the recovery period was discussed. We would like to highlight the recovery period as an integral part of CPET, which is important for the sufficiency of data 2 …