Ecg100c

The EEG and the electrocardiogram (ECG) data were registered using an MP150 platform with EEG100C and ECG100C amplifiers, respectively, running through the AcqKnowledge 4.4 software (BIOPAC^® Systems, Inc. USA). The EEG data was filtered using a 0.5 Hz high-pass filter and a 35 Hz low-pass notch filter, through which a 50 Hz notch filter was in place. Impedances were checked using the electrode impedance checker (EL-CHECK, BIOPAC^® Systems, Inc. USA), and kept below 5 kΩ. The ECG was recorded following the recommendation of the Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology [23 (link)]. A DII-like lead was composed by placing two Ag/AgCl electrodes: one on the left leg (positive) and other on the right arm (negative), with a third Ag/AgCl electrode (ground) being placed over the right leg. An acquisition sample rate of 1000 Hz was used, and recordings were made in the NORM mode through a 35 Hz low-pass notch filter with a 50 Hz notch filter, and a 0.5 Hz high-pass filter.

The MP150 Data Acquisition System (BIOPAC Systems Inc., USA) was used to record the cardiac activity during the heartbeat-tracking task. Disposable pre-gelled Ag-AgCl electrodes (diameter 35 mm, EL502, Biopac Systems) were placed below the right clavicle and below the left lower rib to perform the standard precordial lead II electrocardiogram (ECG; ECG100C; 0.5 Hz high pass filtering, R-wave output mode, signal gain 500). Subjects were grounded through a similar electrode positioned below the right lower rib. ECG recordings were continuously computed during the heart rate perception measure. Physiological data collection and offline analyses of the frequency of the recorded R-waves were realized with the AcqKnowledge Software package (BIOPAC Systems Inc., USA).

ECG was collected using MP 100 and ECG 100c amplifier (BIOPAC System). Frequency of sampling rates was set at 500 Hz and digitized with NI-DAQ-Pad 9205 (National Instruments). Labview (National Instruments) was used to transfer the recorded signals to a computer and Python was used for data processing. R to R intervals (RRI) were calculated from raw ECG recordings and abnormal RRI were excluded from analysis. This study considered normal RRI is between 400–1333 ms. This range corresponds to 45 beat per minute (BPM) and 150 BPM. Missing RRI values were replaced by mean of former normal RRI values. Sliding window technique (window size 180 s and interval 1 s) was applied to collect signals. RMSSD data were divided by RRI to correct the heart rate. Then, the processed RMSSD data were log transformed to correct the skewness [39 ]. RSA_HF (0.15–0.4 Hz). RSA_HF data were normalization by RRI to reduce the effect of beta adrenergic [40 (link),41 (link)]. The processed RSA_HF data were log transformed to correct the skewness like RSA_HF. RSA_PB was extracted according to [29 (link)]. There were no missing values of vagal responses since the missing RRI values were corrected.

The tail cuff method (CODA) was used to measure the SBP and DBP of the rats once before the administration of ISO and once per week following the administration of ISO. The pulse pressure (PP) was calculated using the formula PP = (SBP − DBP). The MAP was calculated using the formula: MAP = DBP + 1/3(SBP − DBP). For ECG recordings, rats were first anesthetized with ketamine (42 mg/Kg, i.p.) and xylazine (5 mg/Kg, i.p.). The ECG electrodes (BIOPAC System Inc, California, CA, USA) were placed subcutaneously in a bipolar configuration (DII). Measurements were done using the Electrocardiogram Amplifier equipment (ECG100C, BIOPAC System Inc, California, CA, USA) and tracings were recorded using the AcqKnowledge III computer software program (3.9.1., BIOPAC System Inc, California, CA, USA). The QT interval was taken as the time from the beginning of the QRS complex to the end of the T-wave. The RR interval was taken as the time elapsed between two consecutive maxima of the R-waves. The corrected QT interval (QTc) was calculated in accordance with the formula [40 (link),41 (link)]:

Arterial pressure was measured non-invasively using a volume-clamp method (Portapress; Finapres Medical Systems, Enschede, the Netherlands). A cuff was attached to the right index finger and adjusted so that it would be maintained at heart level. HR was calculated using a type II ECG (ECG 100C; BIOPAC Systems, Santa Barbara, CA, USA). We measured the tympanic membrane temperature as the core temperature non-invasively using an earphone-type infrared tympanic thermometer (CE Thermo; Nipro, Osaka, Japan) Kiya et al. (17 (link)). The probe of the thermometer was inserted into the ear canal for measurement.
Arterial pressure was recorded with ECG by outputting the pressure pulse wave as an analog signal from the Portapress. The data of all experiments were stored on a hard disk at a sampling rate of 1,000 Hz through an analog-to- digital converter (MP-150; BIOPAC Systems).

A data set containing ECG, BP, and PPG recordings from 17 healthy subjects (11 men), aged 28.5 ± 2.5 years, during a tilt table test was used for method evaluation. The protocol started with 4 min in supine position (Rest1), followed with 5 min in 70°-tilt-up position (Tilt), and ended with 4 min back to supine position (Rest2). The table took 18 s for automatic transitions between stages.
ECG lead V4 was recorded by Biopac ECG100C with a sampling rate of 1,000 Hz, BP signal (x_BP(n)) was recorded by Finometer system with a sampling rate of 250 Hz, and PPG signal was recorded from the index finger by BIOPAC OXY100C with a sampling rate of F_s = 250 Hz. A low-pass filter with a cut-off frequency of 35 Hz was applied to the PPG in order to attenuate noise. This preprocessed PPG signal is denoted x_PPG(n) in this paper. Several points were measured over the PPG pulses. Some of them were measured directly over the pulse as those described in section 2.1.1, and others over the waves extracted from the pulse by the pulse decomposition analysis (PDA) technique described in section 2.1.2.