Transcutaneous oximetry: variability in normal values for the upper and lower limb.

Area of Science:

• Physiology
• Medical Devices
• Dermatology

Background:

• Published normal transcutaneous oxygen partial pressures (PtcO2) for chest and lower limbs have been used to define tissue hypoxia.
• Existing thresholds for hypoxia (e.g., < 40 mmHg) vary among patient groups.

Purpose of the Study:

• To determine 'normal' PtcO2 values for the upper and lower limbs in healthy, non-smoking adults.
• To utilize the Radiometer® TCM400 device with tc Sensor E5250 for accurate measurements.

Main Methods:

• Transcutaneous oxygen measurements (TCOM) were performed on 32 healthy volunteers.
• Measurements were taken on the chest, upper limb, and lower limb under various conditions: breathing air, with limbs elevated, and breathing 100% oxygen.

Main Results:

• Significant variability in room-air PtcO2 was observed across different body sites, including the upper arm, forearm, hand, leg, and foot.
• Nineteen subjects had at least one room-air PtcO2 reading below 40 mmHg.
• A small percentage of lower limb PtcO2 readings were below 100 mmHg when breathing 100% oxygen.

Conclusions:

• The wide dispersion of PtcO2 values in healthy individuals highlights inherent biologic variability in dermal perfusion and oxygen delivery.
• Defining narrow, rigid 'normal' PtcO2 values for the upper or lower limb is not recommended.
• Transcutaneous oxygen measurements should be used as an aid, not an absolute determinant, in patient assessment for hyperbaric oxygen therapy.