Measurement of Peripheral Venous Oxygen Saturation in the Leg Using Near-Infrared Spectroscopy

Background:

It has been suggested that poor healing of wounds may be associated with reduced tissue oxygenation. A non-invasive method of assessing peripheral venous oxygenation has been investigated.

Method:

Changes in oxyhaemoglobin (O2Hb), deoxyhaemoglobin (HHb), oxidized cytochrome aa3 (cyt aa3) and total haemoglobin (tHb) were monitored in the left lower leg of seven healthy volunteers. A short period of venous occlusion was achieved by rapidly inflating a sphygmomanometer cuff placed around the leg to 60 mmHg. The changes in O2Hb and tHb, with respect to the baseline readings, were evaluated. PSvO2 was calculated from (ΔO2Hb/ΔtHb) × 100%.

Results:

From 17 sets of readings on the seven volunteers the median PSvO2 calculated was 64% (range 50–86%).

Conclusion:

This method appears to be a simple means of evaluating PSvO2. A change in cyt aa3 was often seen associated with the venous occlusion.

Changes in Microcirculation in Patients with Atrophie Blanche Visualized by Laser Doppler Perfusion Imaging and Transcutaneous Oxygen Measurements

Objective:

To quantify differences in microcirculation in atrophie blanche (AB) in patients with chronic venous insufficiency (CVI) and in healthy controls before and after venous occlusion.

Design:

Prospective study in a single patient group.

Setting:

Department of Dermatology, University Hospital Maastricht, The Netherlands.

Patients and methods:

Sixteen patients with CVI and large lesions of AB, 10 patients with CVI without AB and 10 healthy controls were enrolled in the study. Laser Doppler perfusion imaging (LDPI) measurements were performed in and outside large lesions of AB and in healthy controls. Transcutaneous oxygen (Tc Po2) measurements were performed in patients with CVI with and without AB and in healthy controls.

Results:

Median basal resting flow was higher in AB than in healthy controls (0.67 mV versus 0.21 mV, p = 0.002). The venoarteriolar response (VAR was increased significantly in AB (58% versus 43%, p = 0.04). A significant decrease in Tc Po2 values occurred in AB lesions with 40 mmHg, in CVI skin with 60 mmHg and in healthy controls with 80 mmHg.

Conclusion:

Basic resting flux in AB measured with LDPI is increased compared with clinically normal skin. The decrease in flux on venous occlusion is larger in AB than in healthy controls.

The Post-Thrombotic Syndrome: A Review

Objective:

A review of the published data on epidemiology, pathophysiology, diagnostic techniques and prevention of the post-thrombotic syndrome (PTS).

Study selection:

Studies, published between 1966 and 1996, identified through the medline database, and references cited in identified articles were included.

Data synthesis:

Deep venous thrombosis (DVT) may cause outflow obstruction and valve incompetence, resulting in venous hypertension. PTS is probably the effect of venous hypertension on the microcirculation. For qualitative anatomical and functional assessment of the venous system, duplex scanning is required, and for quantitative functional assessment, plethysmographic methods are the most suitable. The best treatment of PTS is its prevention by optimizing diagnosis and treatment of DVT and by prescribing and wearing elastic compression stockings. Until valid follow-up studies have been performed, distal DVT should not be neglected when assessing the PTS risk.

Conclusions:

PTS is a serious problem in terms of prevalence, complications (venous ulcers) and treatment with considerable socio-economic consequences. Duplex and plethysmography are valuable tools in its diagnosis and might be appropriate to identify patients at risk of developing PTS.

Cutaneous Blood Flow in Legs with Severe Chronic Venous Insufficiency Recorded before and after a Single Treatment Using Intermittent Pneumatic Compression

Objective:

To investigate the skin laser Doppler flux (LDF) in legs with severe chronic venous insufficiency (CVI).

Design:

Comparison of the legs with severe CVI with the healthy legs and with the patients' contralateral legs.

Setting:

Department of Dermatology, University of Turku, Turku, Finland.

Patients and control subjects:

Ten patients and eight age-matched subjects with healthy legs.

Interventions:

A single treatment using intermittent pneumatic compression (IPC) of 45 min duration.

Main outcome measures:

Laser Doppler flowmetry with the subjects in a recumbent and a sitting position.

Results:

The LDF values were higher for the legs with severe CVI than for the legs of healthy subjects ( p<0.001 in a recumbent and p<0.01 in a sitting position). A single IPC increased the LDF in a recumbent position in the patients' legs with severe CVI ( p=0.019) but had no significant effect on the LDF value in the sitting position. The venoarteriolar response was significantly better in the legs with severe CVI than in the legs of healthy subjects ( p<0.05).

Conclusions:

The LDF is increased in legs with severe CVI and a single IPC further increases it in a recumbent position. The venoarteriolar response is not impaired in legs with severe CVI.

Evaluation of Compression under an Elastic Tubular Bandage Utilised as an Introduction to Compression Therapy in the Treatment of Venous Leg Ulcers

Objective:

To investigate the physical parameters of an elasticated tubular bandage (Tubigrip) on the leg and in durability studies.

Design and setting:

Cohort studies.

Participants:

Six healthy volunteers and 16 patients.

Main outcome measure:

Sub-bandage pressure.

Results:

Median pressures recorded under the Tubigrip bandage system at the lower, middle and upper calf muscle in 6 healthy volunteers, while sitting were 26, 25 and 12.5 mmHg, and for standing were 32, 40 and 16 mmHg. The median pressures recorded at the lower, middle and upper calf muscle in 16 venous leg ulcer patients while sitting were 18, 20 and 14 mmHg, and for standing were 32.5, 29.5 and 18 mmHg. Tubigrip durability studies demonstrated no decrease in sub-bandage compression over 8 days when applied to a model leg and volunteer leg. However, sub-bandage pressure decreased by more than 29% when the bandage was subjected to four wash-dry cycles.

Conclusions:

The pressures measured under Tubigrip were consistent with the ranges seen in other compression therapies. Laundering reduced the applied sub-bandage pressure.

Effect of compression on blood flow in lower limb wounds

Blood flow is believed to be a key parameter in the formation and management of lower limb wounds. Patients with venous leg ulcers (VLUs) have high venous pressures, due to the partial or complete failure of calf muscle pump, which in turn disturbs the local blood flow within the lower limb. Compression has currently been the mainstay for treatment of VLUs and is thought to restore valvular competence and reduce or suppress superficial and deep venous reflux. Efficacy and assessment of compression therapy can be understood in a better way by measuring blood flow in lower limbs. Publications applicable to the effects of compression on lower limb blood flow parameters are summarised. However, they have shown varying results due to the different methodology and assessment techniques used. This article seeks to explore the methods of assessment of blood flow in the lower limb associated with wound management and compression in particular and provides suggestions for future explorations.

Microcirculation Disturbances in Patients with Venous Ulcer before and after Healing as Assessed by Laser Doppler Flux-Metry

BACKGROUND

We studied whether a characteristic pattern of laser Doppler flux (LDF) could be identified in perimalleolar skin of patients with venous ulcer before and after ulcer healing.

METHODS

Nine subjects with venous ulcer that healed after conservative treatment in 1-6 months and nine healthy persons were included in the study. Microcirculation investigations of laser Doppler flux (LDF) were carried out before and after ulcer healing at rest, upon arterial occlusion, during thermal stimulation and during experimental venous hypertension.

RESULTS

Resting LDF expressed as median and range (in arbitrary perfusion units) was significantly higher in patients with venous ulcer in comparison to healthy subjects: 60.6 (40.2-156.5) vs. 9.2 (6.5-19.5), p=0.008. During thermal stimulation and during postischemic reactive hyperemia, absolute values of LDF were slightly but significantly higher in patients with venous ulcer than in healthy subjects, but indices of hyperemic reactivity were very low in patients (median postischemic LDF increase to 101.8 vs. 450.0% in healthy controls, p=0.008; and thermally induced LDF increase to 125.5 vs. 881.5% in healthy controls, p=0.008. Experimental venous hypertension (cuff pressure 40 and 70 mmHg, respectively) led to an equally pronounced relative reduction of LDF in healthy persons as in patients with venous ulcer before and after ulcer healing, but the absolute values of flow remained about six to seven times higher in patients when compared to healthy subjects. Hyperemic reactivity and venoarteriolar response did not change after ulcer healing.

CONCLUSIONS

Elevated basal LDF and preserved maximal LDF during reactive hyperemia were found in perimalleolar skin of patients with venous ulcers that eventually healed. The relative venoarteriolar response was preserved in spite of elevated absolute values of LDF during experimental venous hypertension. These hemodynamic characteristics remained unchanged after epithelialization of venous ulcers.

Measurement of the skin microcirculation through intact bandages using laser Doppler flowmetry

The microcirculation under compression bandages has been assessed by numerous methods; however, the measurement techniques can disrupt the bandage-skin interface, affecting the measurement. In this study, a non-invasive method for measuring cutaneous blood flow using laser Doppler flowmetry (LDF) is presented. Ten volunteers had their microcirculation assessed by a laser Doppler probe being placed on their upper forearm with and without a light-transmissive gel and with a compression bandage plus light-transmissive gel. A circulatory challenge to the bandaged forearm in two of the volunteers was also undertaken. The median (95% confidence interval) perfusion (p.u.) for the skin surface was 24 (15-33) perfusion units (p.u.), and the skin plus light-transmissive gel demonstrated a higher perfusion: 66 (50-82) p.u., (p < 0.012). The addition of the compression bandage, with additional gel allowed to permeate through to the underlying skin, decreased the perfusion to 27 (20-34) p.u. (p < 0.007). In both volunteers, the microcirculatory flow responded to the vascular challenge, resulting in flow changes related to the cuff pressure (45-27 and 14-8 p.u.). This method demonstrated that it may be possible to assess the microcirculation through intact bandages, without the need to place any sensors at the skin-bandage interface.

The use of intermittent pneumatic compression in venous ulceration

Even with the application of four-layer bandaging, the recommended treatment for venous leg ulceration, patients with reduced mobility have delayed ulcer healing. Intermittent pneumatic compression (IPC) has an established role in deep vein thrombosis prophylaxis and has been shown to influence fibrinolysis, tissue oxygenation, oedema and venous return. It has also been suggested, but not yet proven, that IPC may improve the healing of venous leg ulcers. An extensive review of the literature has demonstrated that the use of this treatment on patients with reduced mobility has not been previously studied; yet, analysis of difficult-to-heal ulcer patients would indicate that this method of treatment may be appropriate and requires further study.

The role of low resistance blood flow pathways in the pathogenesis and healing of venous leg ulcers

In an attempt to clarify the pathophysiology of haemodynamics in legs with venous ulcer we investigated the effect of a single intermittent pneumatic compression treatment on the peripheral resistance of leg arteries and the cutaneous laser Doppler flux in the leg. Eight patients with venous leg ulcers and 10 subjects with healthy legs were investigated. Doppler waveforms of the leg arteries and laser Doppler flux of the leg skin were recorded before and after a single intermittent pneumatic compression treatment with the subjects in a recumbent position. In the legs with venous ulcer, the peripheral resistance of the arteries was lower and the laser Doppler flux was greater, compared with healthy legs (p = 0.003 and p = 0.002, respectively). A single intermittent pneumatic compression treatment raised the peripheral resistance in the arteries of legs with ulcer and laser Doppler flux of the skin more in ulcer legs than in healthy legs (p = 0.046 and p = 0.034, respectively). These findings suggest that removal of oedema causes redistribution of skin blood flow in the legs with venous ulcer favouring the superficial capillary perfusion. This could explain why compression treatment promotes the healing of venous leg ulcers.

Venoarteriolar response to experimental venous hypertension in legs with chronic venous insufficiency and in healthy legs, measured using a double-wavelength laser Doppler technique

The venoarteriolar response (VAR) of the skin in legs caused by experimental venous hypertension was measured using a new, double-wavelength laser Doppler probe technique (543 nm and 780 nm). This enables the measurement of the laser Doppler flux in the superficial and deep layers of the skin simultaneously. The recordings were obtained from the leg with the patient in a recumbent position with a sphygmomanometer cuff around the thigh. The VAR was recorded at the cuff pressures of 30 mmHg and 60 mmHg. Ten patients with chronic venous insufficiency (CVI) and 20 control subjects with healthy legs were investigated. The VAR increased in relation to the increase of cuff pressure at both wavelengths. There were no significant differences in the VAR between the cuff pressures within or between the legs with CVI and healthy legs. The VAR measured at 780 nm was very significantly greater than the VAR measured at 543 nm in legs with CVI (p<0.005), as well as in healthy legs (p<0.001). The VAR depends both on the wavelength of the laser Doppler light used and on the degree of venous hypertension. The VAR is not impaired in legs with CVI compared with healthy legs.

Blood flux and venoarteriolar response of the skin in legs with chronic venous insufficiency measured at two different depths by using a double-wavelength laser Doppler technique

The laser Doppler flux (LDF) and the venoarteriolar response (VAR) of the skin in legs with chronic venous insufficiency (CVI) was measured by using a new double-wavelength probe technique (543 nm and 780 nm). The recordings were taken in a recumbent and in a sitting position. Ten patients with CVI and 20 control subjects with healthy legs were investigated. The LDF was found to be significantly enhanced in a recumbent position at 543 nm and in a sitting position at 780 nm in legs with CVI compared with healthy legs (P<0.05 and P=0.02, respectively). The authors could not find the VAR to be impaired in either wavelength in legs with CVI compared with healthy legs. The double-wavelength probe technique makes it possible to record simultaneously the LDF in the superficial and deep layers of the skin on the same place in the leg.