Variable
Median (IQR)
Age (years)
39.5 (25.0–42.0)
Weight (kg)
73.4 (65.3–82.0)
Height (cm)
171.0 (166.7–180.0)
BMI (kg/m2)
24.5 (22.3–26.7)
Fat mass (%)
25.4 (19.1–30.3)
Fat mass (kg)
19.9 (13.8–23.9)
Muscle mass (%)
71.1 (66.4–77.2)
Muscle mass (kg)
50.2 (45.6–59.3)
Total body water (%)
54.6 (50.9–59.2)
Total body water (kg)
38.7 (35.3–45.4)
3.1 Variability of PtcO2 with Time
The results of transcutaneous PO2 measurements in three different sites and at three time points (after 10, 15, and 20 min) are shown in Table 2.
Table 2
Transcutaneous PO2 at the selected time points in the three measurement locations
Time (min) | PtcO2 on arm | PtcO2 on chest | PtcO2 on abdomen |
|---|---|---|---|
10 | 71.5 (65.5–79.5) | 70.5 (52.5–74.5) | 74.5 (57.0–82.0) |
15 | 75.0 (66.0–80.5) | 72.0 (51.0–78.0) | 78.0 (60.0–85.0) |
20 | 76.5 (71.5–82.0) | 74.0 (55.0–77.0) | 80.5 (63.0–85.5) |
p | <0.05 | NS | <0.05 |
The median PtcO2 tended to increase with time in all the measurement sites and reached the highest value at 20 min. A significant increase in PtcO2 values at 10, 15, and 20 min was found in the arm and abdominal locations (Table 2; p < 0.05). Conversely, only a tendency for increase was found when the electrode was placed on the chest. At each time point, the highest PtcO2 values were noted when the sensor was located in the lateral region of the abdomen, while the lowest were measured by the electrode placed at the chest. Significant differences between the measurements taken in three different locations were found at 15 and 20 min (p < 0.05 for both). These differences were due to a significantly higher PtcO2 on the arm and abdomen vs PtcO2 on the chest.
3.2 Variability of PtcCO2 with Time
The summary of PtcCO2 measurements is demonstrated in Table 3.
Table 3
Transcutaneous PCO2 at the selected time points in the three measurement locations
Time (min) | PtcCO2 on arm | PtcCO2 on chest | PtcCO2 on abdomen |
|---|---|---|---|
10 | 38.0 (37.0–39.0) | 39.0 (38.0–41.5) | 38.5 (36.5–40.5) |
15 | 38.5 (37.0–40.0) | 39.5 (37.0–42.0) | 38.5 (37.0–40.5) |
20 | 38.0 (36.5–39.0) | 38.5 (37.0–41.0) | 39.5 (37.0–40.5) |
p | NS | NS | NS |
In all the sensor locations, the values of PtcCO2 were stable at 10, 15, and 20 min (no significant differences between PtcCO2 at the respective time points). Although the numerical values of PtcCO2 measured in the three different locations at the first time point (10 min) are very similar, there was a significant statistical difference between the value obtained from the sensor on the arm and on the chest (p < 0.05). Comparison of PtcCO2 at 15 and 20 min across the three measurement sites showed no significant differences.
3.3 Transcutaneous PO2 and PCO2 in Relation to SaO2 and Arterial Blood Gases
The value of SaO2 measured by pulse oximetry was stable during the entire measurement period; the median SaO2 was 97.9 %, (IQR 97.4–98.6). The median PaO2 and PaCO2 was 96.3 mmHg (IQR 91.3–109.0) and 38.3 mmHg (IQR 35.9–40.2), respectively (Table 4). Transcutaneous PO2 did not correlate with SaO2 at any of the measurement locations (r = 0.11, NS).
Table 4
Arterial blood gases in the study group
Variable | Median (IQR) |
|---|---|
PaO2 (mmHg) | 96.3 (91.3–109.0) |
PaCO2 (mmHg) | 38.3 (35.9–40.2) |
pH | 7.44 (7.40–7.50) |
HCO− 3 (mmol/l) | 25.7 (25.0–26.8) |
SaO2 (%) | 97.9 (97.4–98.6) |
ctHb (g/dl) | 14.2 (13.3–15.0) |
The median PtcO2 was significantly lower than PaO2 (74.7 mmHg vs. 96.3 mmHg, respectively, p < 0.05). No correlations between the values of PtcO2 and PaO2 were found (r = 0.09, NS). The median PtcCO2 and PaCO2 were comparable in all the three time points and at all the measurement locations. The strongest correlation was demonstrated on the arm and on the chest at 20 min (r = 0.66 and r = 0.66, respectively; p < 0.05).
3.4 Transcutaneous PO2 and PCO2 in Relation to Body Composition
The median BMI in our study group was 24.5 kg/m2. Five subjects were overweight (BMI 25–30 kg/m2) and three were obese (BMI >30 kg/m2). There were no significant correlations between PtcO2 or PtcCO2 and age, BMI, and nutritional parameters assessed by bioimpedance. The highest correlation coefficients between PtcO2 and muscle mass, fat mass, and total body water were 0.32, 0.21, and 0.22, respectively (NS). The respective correlation coefficients for PtcCO2 were 0.37, −0.34, and 0.35 (NS).
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