RESUMO O sistema nervoso autônomo está intimamente ligado à frequência cardíaca e se caracteriza como um sistema determinístico caótico. Como o coração é, portanto, controlado por um sistema não linear, essas análises estão sendo cada vez mais usadas. O objetivo deste estudo foi avaliar os índices não lineares dos gráficos de recorrência e os índices lineares em cães saudáveis, doentes e com risco de morte e demonstrar se esses índices apresentam boa acurácia diagnóstica para identificar cães em risco de morte. Sessenta e seis cães foram submetidos à análise da variabilidade da frequência cardíaca por um frequencímetro. Os resultados mostraram que os índices SDNN, RMSSD, PNN50% e DET% apresentaram diferença significativa entre todos os grupos, auxiliando na diferenciação do estado de saúde em termos de homeostase autonômica. Foi observada maior sensibilidade (96,67%) para índices lineares (SDNN, RMSSD e PNN50%) e maior especificidade (100%) para índices não lineares (DET%, REC% e LAM%) no reconhecimento de cães em risco de morte. Índices lineares (SDNN, RMSSD e PNN50%) e índices não lineares (DET% e ShanEnt) apresentaram maior acurácia diagnóstica para identificar cães saudáveis ou em risco de morte. Conclui-se que os índices estudados da variabilidade da frequência cardíaca auxiliam na diferenciação do estado de saúde em cães saudáveis e são excelentes preditores de prognóstico. caótico é portanto linear usadas frequencímetro SDNN PNN50 PNN DET grupos autonômica 96,67% 9667 96 67 (96,67% (SDNN 100% 100 (100% DET%, REC LAM% LAM (DET ShanEnt Concluise Conclui prognóstico PNN5 96,67 966 9 6 (96,67 10 (100 96,6 (96,6 1 (10 96, (96, (1 (96 ( (9

ABSTRACT The autonomic nervous system is closely linked to heart rate and is characterized as a chaotic deterministic system. As the heart is therefore controlled by a non-linear system, these analyzes are being used more and more. The aim of this study was to evaluate nonlinear indices of recurrence graphs and linear indices in healthy, sick and at risk of death dogs and to demonstrate whether these indices have good diagnostic accuracy to identify dogs at risk of death. Sixty-six dogs underwent heart rate variability analysis using a frequency meter. The results showed that the SDNN, RMSSD, PNN50% and DET% indices showed a significant difference between all groups, helping to differentiate the health status in terms of autonomic homeostasis. Greater sensitivity (96.67%) was observed for linear indices (SDNN, RMSSD and PNN50%) and greater specificity (100%) for non-linear indices (DET%, REC% and LAM%) in the recognition of dogs at risk of death. Linear indices (SDNN, RMSSD and PNN50%) and non-linear indices (DET% and ShanEnt) showed greater diagnostic accuracy for identifying healthy or dying dogs. It is concluded that the studied indices of heart rate variability help to differentiate the health status in healthy dogs and are excellent predictors of prognosis. non Sixtysix Sixty six meter SDNN PNN50 PNN DET groups homeostasis 96.67% 9667 96 67 (96.67% (SDNN 100% 100 (100% DET%, REC LAM% LAM (DET ShanEnt prognosis PNN5 96.67 966 9 6 (96.67 10 (100 96.6 (96.6 1 (10 96. (96. (1 (96 ( (9

Meconium aspiration syndrome causes respiratory failure after birth and in vivo monitoring of pulmonary edema is difficult. The objective of the present study was to assess hemodynamic changes and edema measured by transcardiopulmonary thermodilution in low weight newborn piglets. Additionally, the effect of early administration of sildenafil (2 mg/kg vo, 30 min after meconium aspiration) on this critical parameter was determined in the meconium aspiration syndrome model. Thirty-eight mechanically ventilated anesthetized male piglets (Sus scrofa domestica) aged 12 to 72 h (1660 ± 192 g) received diluted fresh human meconium in the airway in order to evoke pulmonary hypertension (PHT). Extravascular lung water was measured in vivo with a PiCCO monitor and ex vivo by the gravimetric method, resulting in an overestimate of 3.5 ± 2.3 mL compared to the first measurement. A significant PHT of 15 Torr above basal pressure was observed, similar to that of severely affected humans, leading to an increase in ventilatory support. The vascular permeability index increased 57%, suggesting altered alveolocapillary membrane permeability. Histology revealed tissue vessel congestion and nonspecific chemical pneumonitis. A group of animals received sildenafil, which prevented the development of PHT and lung edema, as evaluated by in vivo monitoring. In summary, the transcardiopulmonary thermodilution method is a reliable tool for monitoring critical newborn changes, offering the opportunity to experimentally explore putative therapeutics in vivo. Sildenafil could be employed to prevent PHT and edema if used in the first stages of development of the disease.

The aim of the present study was to compare heart rate variability (HRV) at rest and during exercise using a temporal series obtained with the Polar S810i monitor and a signal from a LYNX® signal conditioner (BIO EMG 1000 model) with a channel configured for the acquisition of ECG signals. Fifteen healthy subjects aged 20.9 ± 1.4 years were analyzed. The subjects remained at rest for 20 min and performed exercise for another 20 min with the workload selected to achieve 60% of submaximal heart rate. RR series were obtained for each individual with a Polar S810i instrument and with an ECG analyzed with a biological signal conditioner. The HRV indices (rMSSD, pNN50, LFnu, HFnu, and LF/HF) were calculated after signal processing and analysis. The unpaired Student t-test and intraclass correlation coefficient were used for data analysis. No statistically significant differences were observed when comparing the values analyzed by means of the two devices for HRV at rest and during exercise. The intraclass correlation coefficient demonstrated satisfactory correlation between the values obtained by the devices at rest (pNN50 = 0.994; rMSSD = 0.995; LFnu = 0.978; HFnu = 0.978; LF/HF = 0.982) and during exercise (pNN50 = 0.869; rMSSD = 0.929; LFnu = 0.973; HFnu = 0.973; LF/HF = 0.942). The calculation of HRV values by means of temporal series obtained from the Polar S810i instrument appears to be as reliable as those obtained by processing the ECG signal captured with a signal conditioner.