Evaluation of an Electro-Pneumatic Device for Artificial Capillary Pulse Generation used in a Prospective Study in Animals for Surgical Neck Wound Healing

The paper examines the development and testing of an electro-pneumatic device for wound healing therapy after surgery in the neck area. The device generates air pressure values in a miniaturized cuff using electronic circuitry to drive an electro-valve and air compressor. The device works in two distinct modes: continuous pressure mode and pulsating pressure mode. The pressure value setting can vary from 3 to 11 mmHg, and the pulsating pressure mode’s operating frequency range is approximately 0.1 to 0.3 Hz. Laboratory measurements were conducted to evaluate the device’s correct functioning in both continuous and pulsating pressure modes. A four-day prospective study with animals (n = 10) was also conducted to evaluate neck wound healing therapy using the electro-pneumatic device. Out of the twelve histological parameters analysed to reveal the differences between the experimental and control wounds, only one demonstrated a significant difference. Out of the ten animals treated with the device, three showed a significant difference in terms of benefit after therapy. We can therefore conclude that the device potentially improves the wound healing process in the neck area if the pre-set air pressure value does not exceed 8 mmHg.

. Attenuation of the amplitude of blood pressure oscillation as blood passes from arteries to capillaries.  Table S1 shows the electrical specifications in terms of maximum voltage supply and peak currents, the recommended voltage supply value and the value of current consumption when the set air-pressure in the cuff is approximately 10 mmHg.    Below is the procedure to calculate the values of sensitivity the resolution parameters. It is important to note that the response of calibration curve has a linear trend and a negligible offset in each of the six developed devices (Fig. S3).
The sensitivity value (S) is calculated as follows 2 : S = ΔV out ΔP in .
Since ΔPin = 1 mmHg, sensitivity results in approximately 0.22 V/mmHg. It is the calculated mean value of all values measured in each device. The resolution value (R) can be calculated as follows 2 : The values of V noise are given by the sum of all noise values related to the components used to measure the signal (Fig. Appendix A). The signal crosses ten resistors and two operational amplifiers. In the ten resistors, the root mean square noise voltage is the result of calculating the thermal noise 3 , also called Johnson noise, at a system bandwidth of 10 Hz, while the value of noise of the two operational amplifiers is given by the datasheet. As result, the voltage noise of the analogue circuit for data acquisition is approximately 10 µV.
In the digital circuit, the signal sampling introduces additional noise (i.e. quantization noise). The 10-bit A/D converter divides the reference voltage (i.e. 5 V) into 1023 sub-intervals, each being approximately 5 mV. This is the A/D converter resolution. In practice, the resolution value (Rreal) is obtained from values approximately five times greater than the voltage noise level 4 . Therefore, the resulting resolution value is approximately 0.11 mmHg.  S4a) and air pressure (Fig. S4b).

Appendix B
The results presented in Table 1 and Figure 2 were obtained by the following procedure: A. The following steps were used to filter the signals. The same procedure was used for all the acquired signals.
1. Visualization of the measured signal over the time. Since the device stores data in milliseconds, the signal was re-interpolated to visualize it over seconds.  Figure S5 refers to the signals for tests 1 to 5, and Figure S6 refers to the signals for tests 6 to 10.

Appendix C
The following steps were used to obtain the results presented in Table 2. i. All the measured air pressure signals. ii.

A. Open
The measured voltage values related to the battery level for each performed test. iii.
The measured air pressure signals in the battery voltage value range of 12.3 to 11.5 V. iv.
The results of MATLAB boxplot(X) functions. The selected signals, input as MATLAB boxplot(X) functions, were those signals measured in the of battery voltage value range of 12.3 to 11.5 V. v.