Applications

Raynaud’s Phenomenon and Cold Challenge

Raynaud’s Phenomenon

Raynaud’s Disease (RD), also commonly known as Raynaud’s Phenomenon (RP), is a fairly common disorder said to affect approximately 3 – 20% of the population with symptoms including digital vasospasm of the extremities, capillary stagnation (resulting in discolouration), and finally reactive hyperaemia. These symptoms are commonly exacerbated by cold challenge or emotional stress. Endothelial dysfunction plays an important role in the pathogenesis of many vascular diseases, including RD and can be easily assessed using laser Doppler techniques. The combined use of both laser Doppler and nailfold capilliaroscopy can aid the distinction between primary and secondary RD (Cimmino et al, 2008).

Laser Doppler monitoring (moorVMS-LDF) has been previously used in the study of RP, for example to assess the effect of topically applied substances on microvascular function (Tucker et al, 2009). More recently laser Doppler imaging (moorLDI2) has been employed to assess microvascular function in RP (Wu et al, 2008.) and has also been used in combination with iontophoresis (Anderson et al, 2004).

References

Cold Challenge

The Cold Challenge (or cold provocation) test is commonly used to test the severity of Raynaud’s phenomenon (Murray et al, 2006), whether primary or secondary to systemic sclerosis or of occupational origin (‘Vibration White Finger’). The test can be performed by measuring the hand or foot that is cooled or the opposite limb, to test sympathetically mediated vasoconstriction. Vasoconstriction and responses post cold challenge are assessed by laser Doppler assessment of skin blood flow.

The Cold Challenge

Cold is normally applied by submerging the hand or foot in cold water (typically 20°C, although colder challenges have been reported). The hand or foot is normally kept dry with a polythene glove or bag and the patient instructed to keep the hand open and moving slowly to get the full impact of the stimulus.

Microvascular blood flow and its changes can be assessed by moorVMS-LDF monitoring and moorLDI2, moorLDLS2 and moorFLPI imaging.

Laser Doppler Monitoring

The advantage of moorVMS-LDF monitoring is that probes can remain in position, at any site, during the cold challenge so that immediate responses can be recorded (excluding the movement artefact caused by insertion of the hand into and out of gloves and water).

Probes for this type of test include the standard VP1T skin probe with temperature measurement, the multi-fibre VPIT/7 probe for reduced coefficient of variance, low profile probes can be used where size limitations prevail, e.g. VP8c and VP11sc.

Above, the moorVMS-LDF laser Doppler monitor, available as single or dual channel, shown with a small selection of the probes we have available

Laser Doppler Imaging

The advantage of laser Doppler imaging is that all digits and the dorsum can be measured simultaneously, particularly with the moorLDLS2 imager, with which more dynamic recordings are possible.

The moorLDLS2, shown above, can be mounted on a desktop stand as shown, or a mobile stand.

Moor Instruments recommends dorsal measures, with the hand resting palm downwards, are preferable because this prevents fingers from curling and movement is avoided; resting on a highly insulating surface, e.g. polystyrene, avoids heat transfer to the support surface.
When imaging is required during cooling, air cooling is suggested, if a source of cold air is available.

Analysis of Cold Challenge Response

As with any challenge there are many parameters that can be assessed; the simplest are time to full or partial recovery of pre-challenge blood flow or by assessing the area under the reperfusion curve: lower than controls for patients with primary Raynaud’s, lower still for patients with Secondary Raynaud’s (Murray et al, 2009). Another assessment is by calculating the area under the reperfusion curve. Blood flow is likely to be pulsatile, smoothing (increased time constant) or a running average will help to determine baseline and recovery levels more accurately. This can also be applied to finding the minimum blood flow reached if LD monitoring is used.
Oscillatory components, due to vasomotion, can be assessed by FFT or Wavelet analysis.

Additional Information

Cold challenge and alternate heating has been applied by Lafferty et al (1983) to look at the response ‘gain’; this was found to be significantly lower in controls than in Raynaud’s phenomenon.

Iontophoresis of acetylcholine, to assess endothelial function, has also been used to investigate Raynaud’s disorders (Anderson et al, 2004)

References

For additional information on this Application or advice for tailoring Moor Instruments products to your specific application contact us for more information.