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Apnea, especially in preterm newborns (AoP) is one of the common problems encountered at neonatal units. Numerous factors are likely to play a role in the etiology of apnea. Recent data sugest a role for genetic predisposition of AoP. It seems, that physiological rather than pathological immaturity of the respiratory, or cardiorespiratory control, play a major part in the pathophysiology of AoP. Immaturity of the brainstem, cerebral cortex, receptors of the lungs and the airways as well as of the chemoreceptors contribute to the development of apnea in preterm newborns. Several neurotransmitters (GABA, adenosin, endorphins) and their maturational changes are including in pathogenesis of apnea, too. The instability of the upper airway in preterm infants, asynchrony of musculature of the upper airway and diaphragm, pathological changes in the upper airway and malformations of the central nervous system might also contribute to the occurrence and severity of AoP. In newborns, apnea occurs more frequently in active sleep than in quiet sleep and the frequency of apnea in active sleep is higher in the warm conditions. Durations of apnea correlate with the body heat loss. Cardiovascular changes during apnea - bradycardia, peripheral vasoconstriction and various changes in peripheral blood flow and pressure occur together with changes in ECG. The standard clinical management of apnea includes non-pharmacological treatment (eliciting arousal reactions and reflex breathing by mechanical skin, or mucosa stimulations), pharmacological treatment (methylxanthines are preferred) and application of continuous positive airway pressure (CPAP) or in severe apnea - mechanical ventilation.

Cough is the most common symptom of many respiratory diseases. Currently, no standardized methods exist for objective monitoring of cough, which could be commercially available and clinically acceptable. Our aim is to develop an algorithm which will be capable, according to the sound events analysis, to perform objective ambulatory and automated monitoring of frequency of cough. Because speech is the most common sound in 24-hour recordings, the first step for developing this algorithm is to distinguish between cough sound and speech. For this purpose we obtained recordings from 20 healthy volunteers. All subjects performed continuous reading of the text from the book with voluntary coughs at the indicated instants. The obtained sounds were analyzed using by linear and non-linear analysis in the time and frequency domain. We used the classification tree for the distinction between cough sound and speech. The median sensitivity was 100% and the median specificity was 95%. In the next step we enlarged the analyzed sound events. Apart from cough sounds and speech the analyzed sounds were induced sneezing, voluntary throat and nasopharynx clearing, voluntary forced ventilation, laughing, voluntary snoring, eructation, nasal blowing and loud swallowing. The sound events were obtained from 32 healthy volunteers and for their analysis and classification we used the same algorithm as in previous study. The median sensitivity was 86% and median specificity was 91%. In the final step, we tested the effectiveness of our developed algorithm for distinction between cough and non-cough sounds produced during normal daily activities in patients suffering from respiratory diseases. Our study group consisted from 9 patients suffering from respiratory diseases. The recording time was 5 hours. The number of coughs counted by our algorithm was compared with manual cough counts done by two skilled co-workers. We have found that the number of cough analyzed by our algorithm and manual counting, as well, were disproportionately different. For that reason we have used another methods for the distinction of cough sound from non-cough sounds. We have compared the classification tree and artificial neural networks. Median sensitivity was increasing from 28% (classification tree) to 82% (artificial neural network), while the median specificity was not changed significantly. We have enlarged our characteristic parameters of the Mel frequency cepstral coefficients, the weighted Euclidean distance and the first and second derivative in time. Likewise the modification of classification algorithm is under our interest

Abstract Objective Although the emotion regulatory difficulties in patients with major depressive disorder (MDD) are predicted to associate with impaired cardiovascular autonomic regulation, the changes of cardiac vagal regulation in MDD are incompletely understood. The aim of the study was to evaluate the respiratory sinus arrhythmia (as an index of cardiac vagal regulation) using the spectral analysis in high frequency band of the heart rate variability and the indices of deep breathing test in adolescent patients with major depressive disorder. Materials and methods Twenty-eight adolescent girls were examined - 14 patients with major depressive disorder without pharmacological treatment (average age: 16.4 ± 0.2 yr) and 14 healthy probands (control group) matched for age and gender. The respiratory sinus arrhythmia was evaluated using the spectral analysis in high frequency band of the heart rate variability (HF-HRV) and the parameters of deep breathing test (I-E, I/E). In addition, mean R-R interval was calculated. Results The adolescent patients with MDD had significantly reduced spectral activity in the HF-HRV and lower I/E, I-E parameters compared to matched healthy subjects (P < 0.05). Conclusions We conclude that the adolescent girls with MDD have reduced respiratory sinus arrhythmia indicating cardiac vagal dysregulation. Since impaired cardiac vagal regulation is associated with increased risk of cardiovascular morbidity, this finding underscores the importance of impaired autonomic neurocardiac integrity already in adolescents with major depressive disorder without pharmacological treatment.

Objective. Non-motor symptoms including those reflecting autonomic cardiovascular dysregulation are often present in Parkinson disease. It is unclear whether it is possible to detect cardiovascular autonomic dysregulation in the very early stage of Parkinson disease potentially supporting the concept of the upstream propagation of nervous system damage through autonomic nerves. We hypothesized that cardiovascular dysregulation should precede the motor symptoms and at the time of their occurrence autonomic dysregulation should be clearly demonstrable. Therefore, the aim of this study was to assess the various aspects of autonomic cardiovascular control in the very early stage of Parkinson disease. Approach. We performed prospective case-control study on 19 patients with Parkinson disease (<6 months after motor signs occurrence) and 19 healthy control subjects. For each phase of study protocol (supine, head-up tilt, supine recovery), we calculated a wide array of cardiovascular control related parameters reflecting cardiac chronotropic, cardiac inotropic and vasomotor control and baroreflex mediated cardiovascular response. Main results. We observed the well-preserved heart rate and blood pressure control in patients with early stage of Parkinson disease. However, causal analysis of interactions between heart rate and blood pressure oscillations revealed subtle differences in baroreflex function and baroreflex mediated vasoconstriction response to orthostasis. Furthermore, a tendency towards a decreased contraction strength in Parkinson disease was observed. Significance. Considering only subtle cardiovascular control impairment in our study employing a wide array of sensitive methods at the time when motor signs were clearly expressed, we suggest that motor signs dominated in this stage of Parkinson disease. [ABSTRACT FROM AUTHOR]

Arterial compliance (AC) decrease with aging is accelerated by factors associated with the progression of atherosclerotic process, including obesity. Prevalence of obesity increases not only in adult population but also in children and adolescents. The results of studies characterizing the effect of obesity on AC (often indirectly estimated by pulse wave velocity (PWV)) are contradictory. Considering the limitations of previously applied methods and the need to interpret AC values in the context of potential confounders or during various physiological states, the aim of this study was to compare AC of control and obese adolescents during four different physiological states: supine rest, head-up tilt (HUT), supine recovery and mental arithmetic (MA). AC was assessed by the method based on two-element Windkessel model as the ratio of a time constant t characterizing diastolic blood pressure decay and total peripheral resistance (TPR). In total, fifty healthy and normotensive subjects (40 females, 10 males, age 17.5 years (SD=1.1 years)) were examined - 25 obese and 25 age- and sex-matched control subjects. We observed significantly increased AC values during all phases in obese group. An increase in AC was also preserved after controlling for blood pressure influence. These results were confirmed using PWV based AC estimation. Interestingly, AC decreased similarly during stress phases (HUT, MA) in both groups. Lastly, TPR was decreased throughout the study protocol in obese subjects. In conclusion, AC is increased in young obese subjects consistently during various physiological states. Furthermore, changes of physiological states evoke similar response of AC in both groups indicating preserved autonomic control of elastic arteries. A decreased TPR in obese subjects points towards the influence of different maturation state of the arterial tree and/or changes in vasomotion possibly counterbalancing acceleration of atherosclerosis process. [ABSTRACT FROM AUTHOR]

The baroreflex (BR) is an important physiological regulatory mechanism which reacts to blood pressure perturbations with reflex changes of target variables such as the heart period (electrocardiogram derived RR interval) or the peripheral vascular resistance (PVR). Evaluation of cardiac chronotropic (RR as a target variable) and vascular resistance (target PVR) BR arms was in previous studies mainly based on the use of the spontaneous variability of the systolic or diastolic blood pressure (SBP, DBP), respectively, as the input signals. The use of other blood pressure measures such as the mean blood pressure (MBP) as an input signal for BR analysis is still under investigation. Making the assumption that the strength of coupling along the BR indicates the more appropriate input signal for baroreflex analysis, we employ partial spectral decomposition to assess in the frequency domain the causal coupling from SBP, MBP or DBP to RR or PVR. Noninvasive beat-to-beat recording of RR, SBP, MBP and DBP and PVR was performed in 39 and 36 volunteers in whom orthostatic and cognitive loads were evoked respectively through head-up tilt and mental arithmetic task. At rest, the MBP was most tightly coupled with RR, in contrast to the analysis of the vascular resistance BR arm where the results showed similar importance of all blood pressure input signals. During orthostasis, the increased importance of SBP as the input signal for BR analysis along the cardiac chronotropic arm was demonstrated. In addition, the gain from MBP to RR was more sensitive to physiological state changes compared to gains with SBP or DBP signal as inputs. We conclude that the coupling strength depends not only on the analysed baroreflex arm but also on the selection of the input blood pressure signal and the physiological state. The MBP signal should be more frequently used for the cardiac baroreflex analysis. [ABSTRACT FROM AUTHOR]

Cardiac stroke volume variation (SVV) measurement is one of the techniques to detect fluid-responsive hypovolemia in patients under mechanical ventilation. There is an ongoing effort to apply SVV for this purpose also in conscious patients. However, the effect of mental stress often occurring in conscious patients as a potential confounding factor on SVV is not known. The aim of our study was to compare effect of simulated hypovolemia and mental stress on SVV in healthy volunteers in the context of potential confounders - breathing pattern, respiratory sinus arrhythmia magnitude and sex. We examined 102 young healthy volunteers (58 females), mean age 18.6 years. Finger arterial blood pressure was recorded by volume-clamp photoplethysmographic method (Finometer Pro, FMS, Amsterdam, Netherland). From the blood pressure curve, a built in Model Flow algorithm calculated stroke volume values (SV) for each heartbeat. Respiratory volume was recorded using calibrated respiratory inductive plethysmography (RespiTrace, NIMS, Miami Beach, FL, USA). During four phases of examination protocol (supine rest, head-up tilt (HUT), supine recovery, mental arithmetic task (MA)) we analyzed SVV related to respiratory activity. While during HUT we found an expected increase in SVV together with mean SV decrease, SVV significantly decreased during MA. The observed changes during MA could be attributed to an increased respiratory rate and/or decreased respiratory sinus arrhythmia. Sex related differences in SVV responses to HUT and MA were observed. We conclude that mental stress together with respiratory sinus arrhythmia and respiratory pattern changes can significantly influence SVV as a potential index of fluid responsiveness in conscious patients. [ABSTRACT FROM AUTHOR]

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