RESUMO
The autonomic nervous system plays an important role in physiological and pathological conditions, and has been extensively evaluated by parametric and non-parametric spectral analysis. To compare the results obtained with fast Fourier transform (FFT) and the autoregressive (AR) method, we performed a comprehensive comparative study using data from humans and rats during pharmacological blockade (in rats), a postural test (in humans), and in the hypertensive state (in both humans and rats). Although postural hypotension in humans induced an increase in normalized low-frequency (LFnu) of systolic blood pressure, the increase in the ratio was detected only by AR. In rats, AR and FFT analysis did not agree for LFnu and high frequency (HFnu) under basal conditions and after vagal blockade. The increase in the LF/HF ratio of the pulse interval, induced by methylatropine, was detected only by FFT. In hypertensive patients, changes in LF and HF for systolic blood pressure were observed only by AR; FFT was able to detect the reduction in both blood pressure variance and total power. In hypertensive rats, AR presented different values of variance and total power for systolic blood pressure. Moreover, AR and FFT presented discordant results for LF, LFnu, HF, LF/HF ratio, and total power for pulse interval. We provide evidence for disagreement in 23 percent of the indices of blood pressure and heart rate variability in humans and 67 percent discordance in rats when these variables are evaluated by AR and FFT under physiological and pathological conditions. The overall disagreement between AR and FFT in this study was 43 percent.
Assuntos
Animais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Ratos , Adulto Jovem , Sistema Nervoso Autônomo/fisiopatologia , Análise de Fourier , Bloqueio Cardíaco/fisiopatologia , Hipertensão/fisiopatologia , Derivados da Atropina/farmacologia , Bloqueio Cardíaco/induzido quimicamente , Frequência Cardíaca/fisiologia , Ratos Endogâmicos SHR , Ratos Wistar , Índice de Gravidade de Doença , Teste da Mesa Inclinada , Adulto JovemRESUMO
The autonomic nervous system plays an important role in physiological and pathological conditions, and has been extensively evaluated by parametric and non-parametric spectral analysis. To compare the results obtained with fast Fourier transform (FFT) and the autoregressive (AR) method, we performed a comprehensive comparative study using data from humans and rats during pharmacological blockade (in rats), a postural test (in humans), and in the hypertensive state (in both humans and rats). Although postural hypotension in humans induced an increase in normalized low-frequency (LFnu) of systolic blood pressure, the increase in the ratio was detected only by AR. In rats, AR and FFT analysis did not agree for LFnu and high frequency (HFnu) under basal conditions and after vagal blockade. The increase in the LF/HF ratio of the pulse interval, induced by methylatropine, was detected only by FFT. In hypertensive patients, changes in LF and HF for systolic blood pressure were observed only by AR; FFT was able to detect the reduction in both blood pressure variance and total power. In hypertensive rats, AR presented different values of variance and total power for systolic blood pressure. Moreover, AR and FFT presented discordant results for LF, LFnu, HF, LF/HF ratio, and total power for pulse interval. We provide evidence for disagreement in 23% of the indices of blood pressure and heart rate variability in humans and 67% discordance in rats when these variables are evaluated by AR and FFT under physiological and pathological conditions. The overall disagreement between AR and FFT in this study was 43%.
Assuntos
Sistema Nervoso Autônomo/fisiopatologia , Análise de Fourier , Bloqueio Cardíaco/fisiopatologia , Hipertensão/fisiopatologia , Animais , Derivados da Atropina/farmacologia , Feminino , Bloqueio Cardíaco/induzido quimicamente , Frequência Cardíaca/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Ratos , Ratos Endogâmicos SHR , Ratos Wistar , Índice de Gravidade de Doença , Teste da Mesa Inclinada , Adulto JovemRESUMO
Arterial baroreflex sensitivity estimated by pharmacological impulse stimuli depends on intrinsic signal variability and usually a subjective choice of blood pressure (BP) and heart rate (HR) values. We propose a semi-automatic method to estimate cardiovascular reflex sensitivity to bolus infusions of phenylephrine and nitroprusside. Beat-to-beat BP and HR time series for male Wistar rats (N = 13) were obtained from the digitized signal (sample frequency = 2 kHz) and analyzed by the proposed method (PRM) developed in Matlab language. In the PRM, time series were low-pass filtered with zero-phase distortion (3rd order Butterworth used in the forward and reverse direction) and presented graphically, and parameters were selected interactively. Differences between basal mean values and peak BP (deltaBP) and HR (deltaHR) values after drug infusions were used to calculate baroreflex sensitivity indexes, defined as the deltaHR/deltaBP ratio. The PRM was compared to the method traditionally (TDM) employed by seven independent observers using files for reflex bradycardia (N = 43) and tachycardia (N = 61). Agreement was assessed by Bland and Altman plots. Dispersion among users, measured as the standard deviation, was higher for TDM for reflex bradycardia (0.60 +/- 0.46 vs 0.21 +/- 0.26 bpm/mmHg for PRM, P < 0.001) and tachycardia (0.83 +/- 0.62 vs 0.28 +/- 0.28 bpm/mmHg for PRM, P < 0.001). The advantage of the present method is related to its objectivity, since the routine automatically calculates the desired parameters according to previous software instructions. This is an objective, robust and easy-to-use tool for cardiovascular reflex studies.
Assuntos
Barorreflexo/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Reconhecimento Automatizado de Padrão/métodos , Processamento de Sinais Assistido por Computador , Animais , Barorreflexo/fisiologia , Pressão Sanguínea/fisiologia , Cardiotônicos/farmacologia , Frequência Cardíaca/fisiologia , Modelos Lineares , Masculino , Nitroprussiato/farmacologia , Variações Dependentes do Observador , Fenilefrina/farmacologia , Ratos , Ratos WistarRESUMO
Arterial baroreflex sensitivity estimated by pharmacological impulse stimuli depends on intrinsic signal variability and usually a subjective choice of blood pressure (BP) and heart rate (HR) values. We propose a semi-automatic method to estimate cardiovascular reflex sensitivity to bolus infusions of phenylephrine and nitroprusside. Beat-to-beat BP and HR time series for male Wistar rats (N = 13) were obtained from the digitized signal (sample frequency = 2 kHz) and analyzed by the proposed method (PRM) developed in Matlab language. In the PRM, time series were low-pass filtered with zero-phase distortion (3rd order Butterworth used in the forward and reverse direction) and presented graphically, and parameters were selected interactively. Differences between basal mean values and peak BP (deltaBP) and HR (deltaHR) values after drug infusions were used to calculate baroreflex sensitivity indexes, defined as the deltaHR/deltaBP ratio. The PRM was compared to the method traditionally (TDM) employed by seven independent observers using files for reflex bradycardia (N = 43) and tachycardia (N = 61). Agreement was assessed by Bland and Altman plots. Dispersion among users, measured as the standard deviation, was higher for TDM for reflex bradycardia (0.60 ± 0.46 vs 0.21 ± 0.26 bpm/mmHg for PRM, P < 0.001) and tachycardia (0.83 ± 0.62 vs 0.28 ± 0.28 bpm/mmHg for PRM, P < 0.001). The advantage of the present method is related to its objectivity, since the routine automatically calculates the desired parameters according to previous software instructions. This is an objective, robust and easy-to-use tool for cardiovascular reflex studies.
Assuntos
Animais , Masculino , Ratos , Barorreflexo/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Reconhecimento Automatizado de Padrão/métodos , Processamento de Sinais Assistido por Computador , Barorreflexo/fisiologia , Pressão Sanguínea/fisiologia , Cardiotônicos/farmacologia , Frequência Cardíaca/fisiologia , Modelos Lineares , Nitroprussiato/farmacologia , Variações Dependentes do Observador , Fenilefrina/farmacologia , Ratos WistarRESUMO
Designs for a low-cost dual wavelength transducer based on light transmittance and a disposable cuvette for monitoring oxygen saturation (SO2) in extracorporeal arterial and venous blood are presented. The transducer utilizes red and infrared light-emitting diodes and a large photodiode; it is designed to attach to a flow-through cuvette modified from 3/8-in x3/8-in bypass-circuit connectors. A mock extracorporeal circulation system was assembled to evaluate operation of the transducer at a controlled blood SO2 and the relationship between light transmittance and hemodilution. SO2 was calculated based on multiple linear regression analyses. The results show a high correlation between the SO2 obtained with the equipment designed and values measured with commercial gasometric equipment in the range of 50% to 100% (r2 = 0.976, error <2%). The method presented allows continuous and real time measurement of whole blood SO2 with a low-cost transmittance transducer.
Assuntos
Circulação Extracorpórea/instrumentação , Oxigênio/sangue , Transdutores , Animais , Bovinos , Controle de Custos , Desenho de Equipamento , Hemoglobinas , Análise de Regressão , Transdutores/economiaRESUMO
A novel optical reflectance transducer for continuous and real time monitoring of oxygen saturation (So2) in extracorporeal tubings during cardiopulmonary bypass (CPB) is described. The optical transducer integrates 2 light-emitting diodes and a photodiode. The transducer is attached to the extracorporeal tubing by a transparent flow through a 3/8 x 3/8 inch connector/cuvette. Four transducers were built and evaluated in vitro in a mock extracorporeal system at a controlled So2. The correlation index (r2) between the So2 measured by the transducers and values determined by a commercial blood gas analyzer was 0.998 with an absolute difference < 0.5%. The performance of the transducer was also evaluated during 16 CPB surgeries in patients with an r2 of 0.873 and an absolute difference < 3.5%. The results obtained demonstrate the applicability of the optical reflectance transducer for monitoring So2 in the tubings of the CPB circuit.