## 3 Results and Discussion
### Thermophysiological Comfort of the Patient  
The predicted PMV index for the patient, lying under anaesthesia on the operating table, is shown in Figure 1. The predicted percentage of dissatisfied (PPD) is presented in Figure 2. According to the results, the thermal conditions are assessed, following the ISO standard 15265 [24]. The categories for the climatic conditions are shown in Figure 3.  
The simulated temperature interval in which the thermophysiological comfort of the patient was predicted and assessed was between 23 and 32 \({}^{\circ}\)C. Calculations for temperatures below 23 \({}^{\circ}\)C were meaningless, as, after 25 \({}^{\circ}\)C, the PMV index was \(-\)3 and the PPD index was 100% dissatisfied. High OR temperatures were tested (31 \({}^{\circ}\)C and 32 \({}^{\circ}\)C) aiming to reach a climatic conditions category higher than 5 (slight warm discomfort)--Figure 4.  
For moderate thermal environments ISO 7730 [2] suggest the limits \(-\)0.5 \(<\) PMV \(<\) 0.5 and the PPD index is below 10%. In the current predictions these values are obtained for the interval from 29 \({}^{\circ}\)C, 60% RH (PMV = \(-\)0.42) to 31 \({}^{\circ}\)C, 30% RH (PMV = +0.44). The comfort temperature interval for the patient is far away from the prescribed comfort indoor environmental temperature (20-22 \({}^{\circ}\)C) [2]. The low insulation ability of the standard surgical drape and the low metabolic activity of the patient are the two reasons for the need for very high temperatures in the OR to reach a comfortable environment for the patient. This result confirms the findings in [10], which suggest that the temperature in the OR should be even higher than 24 \({}^{\circ}\)C to ensure the thermophysiological comfort of the patient.  
The risk for perioperative hypothermia and its effect on the patient's health, e.g., influence on the blood loss during an operation and special transfusion requirements, are well recognised [25; 26]. The administration of 1 dm\({}^{3}\) fluid intravenously with a temperature equal to room air temperature (21 \({}^{\circ}\)C) decreases the temperature of the core body by 0.25 \({}^{\circ}\)C [25]. Such an effect is not even foreseen when  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Value** & **Thermal Sense** \\ \hline \(-\)3 & cold \\ \(-\)2 & cool \\ \(-\)1 & slightly cool \\ 0 & neutral \\ +1 & slightly warm \\ +2 & warm \\ +3 & hot \\ \hline \hline \end{tabular}
\end{table}
Table 2: PMV index sense scale.  
\begin{table}
\begin{tabular}{c l} \hline \hline
**Category** & **Comfort Related to the Climatic Conditions** \\ \hline
3 & Severe discomfort without health risk \\
4 & Slight cold discomfort without health risk \\
5 & Comfort, no health risk \\
6 & Slight warm discomfort without health risk \\
7 & Severe warm discomfort without health risk \\
8 & Long-term constraint: discomfort and dehydration after several hours of exposure \\
9 & Short-term constraint: health risk after 30–120 min of exposure \\
10 & Immediate constraint: health risk even for exposures of very short duration (less than 30 min) several hours of exposure \\ \hline \hline \end{tabular}
\end{table}
Table 3: Climatic conditions category.  
calculating the PMV index. Therefore, special methods and devices for warming the patient have been developed and have to be used in the OR in any cases of operations under anaesthesia to assure the thermophysiological comfort of the patient and to protect him/her from perioperative hypothermia. According to the review in [27], these could be intravenous fluid warmers, which are widely applied during surgical operations or body warming devices, like water-filled mattresses, electric blankets, heating pads, carbon fibre items, etc.