Use of light-guide reflectance spectrophotometry in the assessment of peripheral arterial disease

Optical Measurement of Tissue Oxygen Saturation

Advances in opto-electronic systems have meant that optical spectroscopy can now be used for noninvasive measurements in tissue in patients. A number of techniques have evolved over the last 15 years that make use of the characteristic differences in the absorption spectrum of deoxygenated and oxygenated hemoglobin to measure oxygen saturation. This article summarizes, in particular, those techniques that may prove to be applicable to measurements relating to lower extremity wounds. A short introduction is given about existing electrode methods before describing applications of near infrared and visible wavelength spectroscopy to measurements in tissue. The advantages and limitations of these methods are discussed. An example of an area where tissue spectroscopy is now in routine clinical use for tissue healing viability assessment is presented.

Effect of exercise training on clot strength in patients with peripheral artery disease and intermittent claudication: An ancillary study

Objectives:

Patients with peripheral artery disease have walking impairment, greater thrombotic risk, and are often treated with exercise training. We sought to determine the effect of a 3-month-long exercise program on clot strength among patients with peripheral artery disease and intermittent claudication.

Methods:

Twenty-three symptomatic peripheral artery disease patients were randomly assigned to a walking exercise program or to an attention control group who performed light resistance exercise. We investigated the effect of exercise training on clot strength and time to clot formation was assessed by thromboelastography.

Results:

After 3 months of exercise, clot strength (maximal amplitude) and time to clot formation (R) did not change significantly from baseline, even after improvements in claudication onset time (p < 0.01) and peak walking time (p < 0.05). Furthermore, changes in clot formation parameters were not significantly different between groups. Among the 10 individuals demonstrating a reduction in clot strength (reduced maximal amplitude), one was a smoker (10%) compared to 9 of 13 non-responders (69%) whose maximal amplitude was unchanged or increased (p = 0.0097).

Conclusion:

In this ancillary study, a 12-week walking program improved ambulatory function in peripheral artery disease patients with claudication, but does not modify clot strength or time to clot formation. Larger studies are needed to confirm these hypothesis generating findings and to determine whether a different amount or type of exercise may induce a change in clotting in this patient population.

Evaluation of circulatory compromise in the leg in lumbar spinal canal stenosis

To evaluate whether hemoglobin oxygen saturation and hemoglobin concentration of the leg are useful indicators for circulatory compromise in patients with lumbar spinal canal stenosis, we investigated the changes in the indices during level gait using reflectance spectrophotometry. Thirty-three patients with lumbar spinal stenosis were studied. Preoperatively, the hemoglobin oxygen saturation was greater in the 33 patients than in the control subjects. The indices increased in the control subjects more than those in the patients. Postoperatively, the increases in hemoglobin oxygen saturation were greater in the patients with lumbar spinal canal stenosis than before decompression and the hemoglobin concentration tended to approximate that in the control subjects. The results suggest these indices might be useful for monitoring disease severity in patients with lumber spinal canal stenosis. In addition to stenotic ischemia in the spinal canal, it is thought that the neurogenic intermittent claudication is secondarily caused by circulatory failure in the lower extremities attributable to the autonomic nervous dysfunction.

Near-infrared spectroscopy grades the severity of intermittent claudication in diabetics more accurately than ankle pressure measurement

BACKGROUND

The aim of this study was to evaluate near-infrared spectroscopy (NIRS), combined with a treadmill-walking test, as a method of assessment of intermittent claudication (IC) in diabetic patients.

METHODS

Some 208 symptomatic legs in 153 consecutive patients who complained of calf IC due to atherosclerotic disease were studied with NIRS and resting ankle : brachial pressure index (ABPI).

RESULTS

There was good reproducibility of NIRS measurements. Three distinct types of IC were detected by NIRS. ABPI was significantly different between these three types in non-diabetic patients, but could not grade the severity of IC in diabetic patients. Recovery time (RT) of muscle oxygenation differentiated more accurately between severe and moderate claudication than ABPI in diabetics, although RT and ABPI had similar accuracy in non-diabetics. There was a significant correlation between RT and ABPI in non-diabetic patients and patients who had been diabetic for less than 10 years, while there was no correlation in patients who had had diabetes for over 10 years.

CONCLUSION

Measurement of muscle oxygenation during exercise by NIRS graded the severity of IC in diabetic patients more accurately than resting ABPI. An abstract based on this paper was presented to the symposium of the 18th World Congress of the International Union of Angiology in Tokyo, Japan, September 1998

Near infrared spectroscopy for noninvasive assessment of claudication

The purpose of this study was to explore the application of near-infrared spectroscopy (NIRS) to the assessment of peripheral arterial occlusive disease (PAOD). Muscle blood flow, oxygen consumption, arterial inflow capacity, O2 resaturation, and recovery times were determined at rest, under ischemic and hyperemic conditions, and continuously during and after walking exercise in 11 claudicants and 15 nonclaudicants. Blood flow and oxygen consumption (VO2) at rest and blood flow following walking exercise did not differ significantly between claudicants and nonclaudicants. In contrast, VO2 after walking exercise was increased by a factor 4.1 in claudicants compared to a factor of 1.7 in nonclaudicants. The oxygen resaturation rate after arterial occlusion and the oxygen resaturation rate after walking exercise were significantly lower in claudicants. Claudicants showed a higher degree of hemoglobin deoxygenation during walking exercise than nonclaudicants. A high postexercise VO2 is correlated with a low ankle-branchial index (ABI). The resaturation rates and recovery times following walking exercise and arterial occlusion correlated significantly with ABI parameters. A significant negative correlation was found between hemoglobin deoxygenation during exercise and the ABI parameters. A high correlation was observed between the oxygenated hemoglobin (O2Hb) recovery time and the ABI recovery time after walking exercise. NIRS appears to be an effective noninvasive method for assessing the imbalance between oxygen demand and oxygen delivery in the leg muscles of PAOD patients at rest and during exercise.

Amputation level assessment using lightguide spectrophotometry

The aim of this experimental study was to investigate whether lightguide spectrophotometry in the visible wavelength range in skin could be used to predict stump healing viability in patients with critical lower limb ischaemia. Remission spectra recorded at two sites (medial and lateral) on the line of a proposed trans-tibial amputation (TTA) and at 10mm intervals along the leg were analysed to give haemoglobin oxygenation (SO2). Degree of tissue hypoxia (DTH) along the leg was defined as the percentage of values along the leg less than 10% SO2. DTH and mean SO2 values were compared with skin blood flow values ((I125) 4-Iodoantipyrine clearance technique) and clinical outcome of trans-tibial amputation, (TTA) or trans-femoral amputation (TFA), in 41 patients. SO2 histograms were also measured in 12 normal subjects for comparison. The results of the study allowed the establishment of criteria for the accurate prediction of flap healing potential. Successful TTAs all displayed a minimum mean SO2 at the medial and lateral measurement sites of 30%, together with a maximum degree of tissue hypoxia of 15% along the limb. The combination of these criteria gave a sensitivity and selectivity of 1.0 for prediction of a successful outcome of TTA.