Please see Bibliography of References for a list of abstracts, manuscripts and posters.
Ubbink D, Koopman B. Vascular Medicine Congress; October 8-10, 2003; Toulouse, France.
Introduction: Near infrared spectroscopy (NIRS) is a non-invasive technique to assess oxygen saturation (sO2), which could be a valuable tool in addition to the various techniques presently available to assess skin blood flow and tissue oxygenation. We compared the responses of a new NIRS device with those of transcutaneous oxygen (TcpO2) and laser Doppler (LD) measurements in their appreciation of the microcirculation in the leg and their reproducibilities.
Patients and methods: Twenty healthy subjects with a mean age of 30 years (range: 21-55 yrs.; 11 males) and normal ankle and brachial blood pressures were studied. A new NIRS device (Inspectra 325; Hutchinson Technology Inc., Hutchinson, MN, USA) with a wavelength range between 650 and 810 nm and a 25 mm probe, and a TcpO2 electrode (TCM400; Radiometer, Copenhagen; heated to 44°C) were applied to the lateral side of the calf. Measurements were taken at rest while supine and during and after a 5 minute, 3.1 km/hr treadmill exercise. Subsequently, the NIRS and TcpO2 were applied to the dorsum of the foot, while the LD (Periflux 4000; Perimed, Stockholm) was attached to the plantar side of the big toe. Measurements were taken while supine at rest, during postocclusive hyperaemia, and after changing to the sitting position. The same measurements were repeated after approximately 2 weeks to assess their reproducibility, which was expressed by the Intraclass Correlation Coefficient (ICC).
Results: Mean NIRS sO2 values at the calf were significantly higher in males than in females (83% vs. 53%, p<0.001). After exercise, sO2 slightly decreased (to 77% and 48%, respectively; p<0.001), while TcpO2 increased from 65 to 72 mmHg (p<0.01). SO2 values at the foot (71%) were similar to those at the calf and between males and females. TcpO2 at the calf (65 mmHg) was higher than on the foot (57 mmHg; p<0.05). After arterial occlusion, sO2 increased to 82% (p<0.001) and LD perfusion showed a 9-fold hyperaemic increase, while TcpO2 remained unchanged (56 mmHg). After changing to the sitting position sO2 decreased significantly to 38% (p<0.001), LD decreased to 20% of its resting value, and TcpO2 increased slightly but significantly (61 mmHg; p<0.001). ICCs of the NIRS, LD and TcpO2 at rest were 0.91 (95% confidence interval: 77-97), 0.60 (0-85), and 0.74 (31-90), respectively.
Conclusion: The new NIRS device is a reproducible tool to assess local oxygen saturation. NIRS, TcpO2 and LD show different responses upon provocation tests, illustrating the different functional areas they appreciate. The clear gender difference as found with NIRS may be due to a different thickness of the subcutis or a difference in muscle ‘fitness’.