Quad bio amp

All rat experiments were approved by the Institutional Animal Care and Use Committee of Seoul National University Hospital [approval number: 19-0116-S1A1(1)]. Animals were maintained in a facility accredited by AAALAC International in accordance with the Guide for the Care and Use of Laboratory Animals (eighth edition, NRC).
Eight-week-old Sprague-Dawley male rats (average body weight, 340 g) were anesthetized with the lowest possible dose of isoflurane inhalant (4% isoflurane mixed with oxygen), followed by endotracheal intubation and maintenance of 2 to 3% isoflurane (31 (link), 32 (link)). Each animal was connected to a small animal ventilator (RoVent Jr., Kent Scientific, USA). Full thoracotomy was performed as previously described for the rabbit model. After thoracotomy, the LAD coronary artery was ligated using a 7-0 black silk suture, accompanied by surface ECG recording using a conventional DAQ system, Quad Bio Amp and PowerLab 8/35 (AD Instruments, New Zealand).

For ECG measurements, conducting gel was applied to the volunteer’s inner wrists, and NC electrodes were attached as working and counter electrodes. An Ag/AgCl electrode (2223H, 3 M, USA) served as the ground electrode on the ankle. The ECG sensor was connected to conventional data acquisition (DAQ) system, Quad Bio Amp, and Powerlab 8/35 (AD Instruments, New Zealand). ECG signals were recorded at a 1,000 Hz sampling rate using the LabChart software (AD Instruments, New Zealand), which included a bandpass filtering (1–20 Hz) and signal analysis capabilities.
For EMG measurements, NC electrodes were affixed to the volunteer's forearm with a 5 mm spacing after applying conductive gel, and the ground electrode was place on the rear hand. A bandpass filter (3–300 Hz) was used, and signals were acquired during fist clenching every 5 s. Signal-to-noise ratio (SNR) was calculated using the formula: SNR_dB =  $20{\text{log}}_{10}\left(\frac{{\text{V}}_{\text{signal}}}{{\text{V}}_{\text{noise}}}\right)$ , (V_noise: the sEMG signal obtained from the settling trial, V_signal: the sEMG signal during fist clenching). Both signals were determined using root mean square calculations.

The skin of the xiphoid process at the lower end of the animal’s sternum was incised, and a small incision of about 2 cm was cut along the linea alba to open the abdominal cavity.
Needle electrodes (MLA1213, ADInstruments, Sydney, Australia) inserted into the exposed diaphragm were connected to the Biological Amplifier (FE234, Quad Bio Amp, ADInstruments, Sydney, Australia) for collection of bilateral EMGdi signals (left EMGdi and right EMGdi).