# Hardware-in-Loop Modules for Testing Automated Ventilator Controllers
## 3 Results
### OxyVent Characterization  
The OxyVent module was characterized regarding its DO responsiveness to \(\text{TiO}_{2}\) and PEEP levels. There was minimal variance in the DO during the initialization of each run between the six air-nitrogen ratios. The system had a range of DO between 2.63 (air-nitrogen ratio of Partial air and N\({}_{2}\) Off) and 8.95 (air-nitrogen ratio of Full air and N\({}_{2}\) Off) ppm, with a standard deviation of 0.181 and 1.04, respectively. The ability of the system to achieve both differing \(\text{O}_{2}\) absorption rates and \(\text{O}_{2}\) saturation levels using varying ratios of air-nitrogen is demonstrated in Figure 9. In addition, Figure 9 demonstrates how the DO trends compare to each air-nitrogen ratio when normalized by the minimum value of each respective ratio. DO values for each air-nitrogen ratio, with specific minimum, maximum, and mean values of DO and standard deviations for each respective ratio, are shown in Table 1.  
Figure 8: \(\text{EtCO}_{2}\) and MV relationships in low and high tests. (**A**) Scatter plot with an inverse trend between minute ventilation (MV) and \(\text{EtCO}_{2}\) in low \(\text{EtCO}_{2}\) tests. (**B**) Effects of tidal volume (\(\text{V}_{\text{T}}\)) on \(\text{EtCO}_{2}\) in low \(\text{EtCO}_{2}\) tests. (**C**) Relationship between MV and \(\text{EtCO}_{2}\) in high \(\text{EtCO}_{2}\) tests. (**D**) Effects of respiratory rate (RR) changes on \(\text{EtCO}_{2}\) in high \(\text{EtCO}_{2}\) tests. [PERSON]’s correlation (R) values are shown for each, along with the statistical significance for each data trend. Adding a modification to PEEP, there was minimal variation in the DO values between the three air-nitrogen ratios during the initialization of the runs. Throughout the three varying canister pressures of 0, 5, and 10 psi, the system had a range of DO values between 2.39 \(\pm\) 0.0873 and 9.72 \(\pm\) 0.604 ppm (Figure 10). The pressures were each held for five minutes until the system reached steady-state DO values. At a canister pressure of 0 psi, the steady-state DO was 5.61, 6.72, and 7.24 ppm for air-nitrogen ratios of Partial/Partial, Partial/Off, and Full/Full, respectively. When the canister pressure was increased to 5 psi, the steady-state DO reached values of 6.42, 7.98, and 7.98 ppm for the air-nitrogen ratios previously mentioned. Finally, for the same previously listed air-nitrogen ratios, the steady-state DO values reached 7.26, 9.72, and 9.34 ppm at a canister pressure of 10 psi. In addition to the steady-state (maximum) DO values, the minimum DO values and standard deviation values at each respective pressure step are displayed in Table 2. \begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{2}{c}{**Partial Air/Full N\({}_{2}\)**} & \multicolumn{2}{c}{**Partial Air/Partial N\({}_{2}\)**} & \multicolumn{2}{c}{**Full Air/Full N\({}_{2}\)**} \\ \hline  & DO & Std Dev. & DO & Std Dev. & DO & Std Dev. \\ \hline Min & 2.63 & 0.181 & 2.69 & 0.148 & 2.73 & 0.0153 \\ Max & 5.30 & 0.414 & 5.90 & 0.392 & 6.69 & 0.702 \\ \hline  & \multicolumn{2}{c}{**Full Air/Partial N\({}_{2}\)**} & \multicolumn{2}{c}{**Partial Air/N\({}_{2}\) Off**} & \multicolumn{2}{c}{**Full Air/N\({}_{2}\) Off**} \\ \hline  & DO & Std Dev. & DO & Std Dev. & DO & Std Dev. \\ \hline Min & 2.70 & 0.125 & 2.80 & 0.139 & 2.63 & 0.643 \\ Max & 6.95 & 0.589 & 8.17 & 0.990 & 8.95 & 1.04 \\ \hline \end{tabular}
\end{table} 
Table 1: Summary of the minimum, maximum and mean values of DO (ppm) and the respective minimum and maximum standard deviation values. Figure 9: **Characterization of the OxyVent module FiO\({}_{2}\) functionality**. Average trends for six air–nitrogen ratios (n = 3 each) and their dissolved oxygen (DO, ppm) values over the course of five minutes. (**A**) DO versus time relations for each air–nitrogen ratio not normalized to the starting value; shaded regions denote standard deviation. (**B**) Each air–nitrogen ratio normalized to their minimum value to better illustrate the differences in DO values over the five-minute period.