Reproducibility of parameters of postocclusive reactive hyperemia measured by near infrared spectroscopy and transcutaneous oximetry.

The purpose of this study was to investigate postocclusive hyperemic response using near infrared spectroscopy (NIRS) and transcutaneous oximetry (TcpO2). Five minute arterial occlusion on the calf muscle was performed in six healthy volunteers (mean age 29, range 23-34 years, mean TcpO2 at rest 53 mm Hg, range 47-58 mmHg, and ankle brachial index between 1 and 1.2). Oxygen partial pressure at rest, oxygen consumption (VO2) during ischemia, recovery times and resaturation rates after arterial occlusion were determined and new parameters for evaluation of the level of vascular disorders of lower limbs are suggested. The reproducibility of the signals was studied by repeating the same protocol on each subject four to six times. Repeated measurements showed no significant difference among trials, indicating that the measurements were reproducible. The mean values of the coefficient of variability for suggested parameters varied between 6% and 30% (mean value 17%). Interindividual variations of parameters are higher and can be explained by differences in fat/muscle ratio and in the measured tissue volume of the NIRS signal. Simultaneous measurements of NIRS and TcpO2 showed different responses to ischemic conditions, due to the different physiological levels of oxygen assessment. The combined use of both methods yields deeper insight into conditions of blood flow and tissue oxygenation.