RESUMO
INTRODUCTION: Several studies define normal transcutaneous oximetry measurements (TCOM) for the chest and lower limb, but not the upper limb. Standardised healthy-subject reference values for upper limb TCOM would make interpretation of these measurements in disease or injury more meaningful. AIM: To determine 'normal' TCOM values for the upper limb in healthy non-smoking adults. METHOD: Thirty-two healthy volunteers (16 male, 16 female) had TCOM performed on the chest and at five upper limb positions: lateral aspect of the upper arm midway between the shoulder and elbow; lateral aspect of the forearm, dorsum of the hand, thenar and hypothenar eminences. Measurements were taken using the TCM400 Monitoring System (Radiometer) with subjects breathing room air and whilst breathing 100% oxygen. RESULTS: Room-air TCOM values (mean (SD), 95% confidence interval (CI)) were: chest: 50 (11.4) mmHg, 95% CI 46.0 to 54.2; upper arm: 53 (9.3) mmHg, 95% CI 49.7 to 56.4; forearm: 45 (11.3) mmHg, 95% CI 40.4 to 48.6; dorsum of hand: 39 (8.5) mmHg, 95% CI 35.5 to 41.7; thenar eminence: 54 (7.7) mmHg, 95% CI 51.7 to 57.2; and hypothenar eminence: 57 (7.5) mmHg, 95% CI 54.1 to 59.6. All readings showed a substantial increase when subjects breathed 100% oxygen. Using the currently accepted threshold for tissue hypoxia of < 40 mmHg, six forearm and 14 dorsum of the hand TCOM readings would have been classified as hypoxic. CONCLUSION: Normal upper limb TCOM readings are less than those established for the lower limb. Using lower-limb reference standards could result in false-positive determinations of tissue hypoxia. We recommend TCOM ≤ 30 mmHg as indicative of tissue hypoxia in the upper arm, thenar and hypothenar eminences, and < 20 mmHg in the forearm and dorsum of the hand.