Oxygen inhalation induced changes in the skin as measured by transcutaneous oxymetry

Postischemic Transcutaneous Oxygen Tension Response in Assessment of Peripheral Atherosclerosis

The applicability of transcutaneous oxygen tension measurements (TCpO2) at rest and after a postischemic response test was investigated in a control group and in patients with peripheral atherosclerosis. Three parameters were evalu ated : oxygen reappearance time (ORT), oxygen recovery index (ORI), and rest ing oxygen tension (ROT). ORT distinguished controls and patients, as well as patient groups. An ORT ≥ twenty seconds is indicative of peripheral circulatory insufficiency and seemed to be dependent on the postischemic reappearance of blood flow. ORI did not separate the groups as well as ORT and was signifi cantly reduced only in patients with critical ischemia. It is concluded that mea surement of ORT, ORI, and ROT are easily performed, assessing oxygenation of the skin. ORT probably indicates the function of supplying arteries. ORI is related to compensatory mechanisms and changes in the microcirculation.

Review articles : Pressure sores: methods used for the assessment of patient support surfaces

In the seriously ill, the paralysed and the elderly patient, many factors such as poor skin blood flow, malnutrition and immobility predispose to a high incidence of decubitus ulcers or pressure sores. The development of a sore is a complex process, but skin distortion and localized pressure are considered important precipitating factors. Over the last two decades manufacturers have produced a large variety of support surfaces claiming to be effective in prevention as well as treatment of sores. However, a review of available literature shows that none of the test methods used by different investigators has provided a comprehensive means of determining which device is appropriate for a particular patient.

Oxygen tension assessment: an overlooked tool for prediction of delayed healing in a clinical setting

Successful wound healing requires adequate transcutaneous oxygen tension (tcpO(2) ). TcpO(2) may not commonly be incorporated in clinical assessments because of variable measurement response at different sensory temperatures. This study aims to assess the relationship between changes in tcpO(2) , measured under basal (39°C) and stimulated (44°C) conditions and healing rate of chronic wounds over 4 weeks, to determine whether tcpO(2) measurement can predict delayed wound healing. TcpO(2) (Radiometer TCM400) measurements at sensor temperatures 39 and 44°C were recorded (twice, 4 weeks apart) adjacent to the ulcer site, and at a mirror image site on the contralateral leg. Ulcer outline was traced on clear acetate and perimeter and area measured (Visitrak™, Smith and Nephew). TcpO(2) measured at 44 and 39°C adjacent to all 13 wounds were lower compared to the contralateral site, significant at 44°C (P = 0·008). Significant correlation (r(2) = 0·8) occurred between wound healing rate and increased tcpO(2) at 44°C over 4 weeks. Importantly, the ratio of 39/44°C tcpO(2) , measured at the initial appointment, appeared to predict normal or delayed healing rate. TcpO(2) may provide clinicians with information regarding anticipated healing ability of wounds at the initial appointment, and hence identify wounds requiring early implementation of adjuvant therapies to accelerate healing.

Lower-limb amputations in patients with diabetes mellitus

It is estimated that approximately 23.6 million people in the United States have diabetes mellitus. With adequate control of this disease and appropriate foot care and basic surveillance, many patients can lead active and healthy lifestyles. However, some patients experience complications associated with poorly controlled glucose levels, including lower-extremity ulcerations and infections. When conservative measures have failed in treating these conditions, a lower-extremity amputation is an option for patients seeking to gain maximal functional recovery. A complete preoperative workup includes assessment of healing potential and preoperative ambulatory status, control or optimization of comorbidities when possible, and determination of amputation level using modern diagnostic modalities. Once the decision to proceed with an amputation has been made, it is important to choose an appropriate level of amputation and practice sound surgical technique. This article describes the preoperative evaluation and operative techniques involved in performing amputations on diabetic patients and reviews the current literature on the most common lower-extremity amputations performed in the care of infections in the feet of patients with diabetes mellitus.

Assessment of patient support surfaces: principle, practice and limitations

Pressure ulcers cause great pain and suffering to patients as well as unnecessary strain on nursing staff. Their treatment is both costly and time consuming. Every effort therefore should be directed towards their prevention. Understanding of the aetiology of pressure ulcers is still incomplete and assessment of devices aimed at prevention is difficult. Over the years, numerous parameters, including interface pressure and transcutaneous blood gas measurements, have been used to evaluate mattresses and cushions. However, the quality of the data gathered is variable and its clinical interpretation remains unsatisfactory. It could be said that the science of evaluation of support surfaces is still at a formative stage, as clinical validation of many of the approaches has yet to be carried out.

Use of the sensory nerve stimulator to accelerate healing of a venous leg ulcer with sensory nerve dysfunction: a case study

A new therapy using sensory nerve stimulation [International Patent Application Number PCT/AU2004/001079: "nerve function and tissue healing" (Khalil, Z)] has been developed in our vascular physiology laboratory. This treatment has been found to improve the deficient sensory nerve function and associated deficient wound healing of older persons to levels seen in young people. An 82-year-old man with a small but persistent venous leg ulcer for 18 months, despite apparently appropriate wound dressings and compression therapy, was seen in a specialist wound management service. The patient's sensory and microvascular function was assessed in great detail using the vascular physiology laboratory techniques, and he was provided the sensory nerve stimulation therapy in addition to conventional therapy. His wound healed after 4 weeks. We report the case here. Prior to nerve stimulation therapy, cutaneous sensation, microvascular blood flow and oxygen tension were found to be reduced near the ulcer when compared with the opposite, non ulcerated leg. After therapy, oxygen tension and microvascular blood flow had improved. This case provides further evidence that sensory nerve stimulation therapy at the stipulated parameters improves wound healing. The observation that sensory nerve function improved provides support for the notion that improvement in healing is mediated by improved nerve function.

Transmetatarsal amputations

Transmetatarsal amputation is an excellent procedure in the face of nonhealing ulceration, infection, trauma, peripheral vascular disease, and tumors. This article discusses transmetatarsal amputations, the decision-making process, timing of surgery, operative techniques, postoperative management, and salvage of the failed transmetatarsal amputation.

Age-related changes in microvascular blood flow and transcutaneous oxygen tension under Basal and stimulated conditions

BACKGROUND

Adequate cutaneous microvascular blood flow and tissue oxygen tension are important prerequisites for successful tissue repair. The efficacy of tissue repair decreases with age and is linked to the age-related functional decline of unmyelinated sensory neurons that are important for inflammation and tissue repair. However, available information on the effect of these neuronal changes on microvascular blood flow and tissue oxygen tension is limited, particularly under control and injury conditions. The authors had two aims in this study: (a) to assess age-related changes in the relationship between microvascular blood flow and tissue oxygen perfusion under basal and two different stimulated conditions (sensory dependent and sensory independent), and (b) to clarify the biological meaning of transcutaneous partial pressure of oxygen (tcPO2) measurements.

METHODS

The effects of a sensory-independent vasodilator (acetylcholine) and a sensory-dependent vasodilator (capsaicin) on microvascular blood flow and oxygen perfusion in persons of different ages were measured. Laser Doppler flowmetry and a commercially available transcutaneous oxygen monitor (with sensors set at 39 degrees C and 44 degrees C) were used. Healthy volunteers were recruited: 11 young, 14 middle aged, and 19 older.

RESULTS

Under basal conditions (skin temperature, 37 degrees C to 39 degrees C), both basal blood flow and tcPO2 increased with increasing age. However, with the sensor set at 44 degrees C, tcPO2 showed a significant decrease with age. Acetylcholine increased blood flow approximately equally in the three age groups. Capsaicin increased blood flow and tcPO2 in all age groups, with the young showing a greater increase compared with the older participants.

CONCLUSIONS

The age-associated changes in basal and stimulated microvascular blood flow and tcPO2 could be attributed in part to altered neuronal function. Measuring tcPO2 at 39 degrees C showed a trend toward an increase with age. In contrast, a decrease with age was observed when tcPO2 was measured at 44 degrees C, a temperature sufficient to activate sensory nerve endings. The results may reflect a decline in sensory nerve function with age rather than a decrease in oxygen delivery for vascular reasons. This is supported by the complementary data showing a significant age-related decrease in stimulated blood flow in response to capsaicin, with no change in the response to the sensory-independent vasodilator acetylcholine. Thus, for clinical purposes, data obtained using the tcPO2 monitor should be interpreted with full knowledge of the conditions under which the measurements were made. Furthermore, for scientific purposes, the tcPO2 monitor could be used to assess sensory nerve function when sensors are heated to 44 degrees C.

A guide to evaluating different wheelchair seat cushions

Over the years, there has been a considerable increase in the number and variety of wheelchair seat cushions. People required to select a cushion are faced with a confusing and often misleading array of commercial literature. The cost of these products range from less than £100 to several hundred pounds, so the importance of a logical approach to their selection cannot be overstated. Inappropriate selection not only wastes capital resources, but it can also be very harmful to the patient.

Although the effectiveness of a wheelchair cushion is best evaluated through clinical trials, these are expensive to conduct and in the case of new products, such evidence is not readily available. In order to overcome this drawback, researchers have developed experimental methods of evaluation based upon existing knowledge of pressure ulcer aetiology. This article describes the most common methods, along with a new technique known as pressure relief index.

Assessment of alternating-pressure air mattresses using a time-based pressure threshold technique and continuous measurements of transcutaneous gases

Alternating-pressure air mattresses (APAMs) are used increasingly for the prevention and treatment of pressure sores. Laboratory evaluation techniques have centred largely on interface pressure (IP) measurement, typically analysing discrete maximum and minimum levels, or average pressure. However, since pressure relief varies with time, a time-based analysis technique has been developed for performance assessment. IP was recorded continuously, and the duration of pressures below three thresholds (30, 20 and 10 mmHg) was calculated automatically using a computerized rig. Fifteen healthy volunteers were used to evaluate the pressure-relieving characteristics of four APAMs, including one overlay. Results indicated significant differences (P < 0.001) between products when durations below the 20 and 10 mmHg thresholds were analysed, showing that some devices were only capable of momentarily relieving pressure. Maximum contact pressures on the sacrum were significantly lower (P < 0.0001) on devices whose inflation pressure was adjusted according to subject's body mass. This technique could assist in the selection of alternating or dynamic surfaces of any description with further clinical validation.

The synergistic effect of sympathectomy and hyperbaric oxygen exposure on transcutaneous PO2 in healthy volunteers

The benefit of hyperbaric oxygen (HBO2) exposure is dependent on the oxygen delivery. Such benefit may be limited by the fact that hyperoxia causes vasoconstriction and decreases blood flow. The aim of this study was to determine whether regional sympathectomy attenuates this vasoconstriction response and thus improves oxygen delivery. In a double-blinded manner, healthy volunteers were subjected to HBO2 in a monoplace chamber on two occasions separated by at least 1 wk. Transcutaneous oxygen (tcPO2) and carbon dioxide (tcPCO2) on the forearm were monitored continuously, and blood flow in the axillary artery was measured using angiodynography before and after exposure to HBO2. During one visit, each volunteer received a sympathetic block to the upper extremity by an injection of lidocaine into the brachial plexus at the axilla. During a second visit, the volunteer received a placebo injection of isotonic sodium chloride solution into the brachial plexus of the same side. Skin temperature was recorded on the back of the hand. All subjects exhibited a small but significant increase in skin temperature (2.5%) and in upper limb blood flow (23%) (P < 0.05%) after sympathectomy, but not after isotonic sodium chloride solution injection. Sympathectomy increased tcPO2 marginally while in room air. However, during HBO2, tcPO2 was substantially and significantly higher (409.8+/-98.8 mm Hg) after sympathectomy compared with that after isotonic sodium chloride solution injection (171.3+/-38.1 mm Hg). tcPCO2 did not change significantly after sympathectomy or during HBO2. Thus, sympathectomy presumably improved oxygen delivery by preventing vasoconstriction during hyperoxia. The results suggest that sympathectomy may be a useful adjunct to HBO2 therapy in patients in whom vascular resistance is increased because of sympathetic tone or hyperoxia.

IMPLICATIONS

Sympathetic nerve block of the extremities markedly enhances tissue oxygen delivery during hyperbaric oxygen treatment. Sympathectomy may be a beneficial adjunct treatment to hyperbaric oxygen in peripheral vascular insufficiency.

Comparative diagnostic value of ankle-to-brachial index and transcutaneous oxygen tension at rest and after exercise in patients with intermittent claudication

BACKGROUND

Few studies have compared sensitivities of ankle-to-brachial index (ABI) and transcutaneous oxygen tension (TcPO2) in a large group of patients with Leriche stage II intermittent claudication.

METHOD AND RESULTS

111 patients (138 limbs) with a stable chronic (> three months) intermittent claudication and significant peripheral vascular disease (PVD) proved by angiography were studied. They performed a treadmill test (10%, 3 km/hr) limited by limb pain. ABI and TcPO2 were measured before, just after exercise, and after three and ten minutes of recovery in supine position. Sensitivities per patient for ABI and TcPO2 were respectively at rest: 82.9% and 28.8%, and after exercise: 88.3% and 62.2%. Sensitivities per leg (n = 138) for ABI and TcPO2 were respectively at rest: 73.9% and 26.8%, and after exercise: 82.6% and 34%. The sensitivity of TcPO2 increased to 56.5% after three minutes of recovery but was always less than that of ABI, which was maximal just after exercise (82.6%). The sensitivity of the regional perfusion index was similar to that of TcPO2. The sensitivity of TcPO2 increased with respect to the Leriche stage and the number of lesions but was always lower than that of ABI. There was a weak correlation between TcPO2 and ABI after exercise, but no correlation was noted between maximal walking distance, ABI, and TcPO2.

CONCLUSION

TcPO2 is not required in patients with Leriche stage II intermittent claudication but might be useful either in severely affected patients (Leriche stage III or IV) or in selected patients.

Microvascular investigations in diabetes mellitus

This paper reviews the current literature concerning the different investigative modalities available to assess the microcirculation in diabetic microangiopathy. The advantages and disadvantages of the different invasive and noninvasive methods available are presented objectively. We have concentrated on the tests that provide a quantitative assessment of the microcirculation, including laser Doppler fluxmetry, capillary microscopy, plethysmography, transcutaneous oximetry and radioactive isotope clearance. Some of the invasive methods described are now being replaced by noninvasive equivalents, providing similar information with less discomfort and risk to the patient.

Selection of amputation level: a review

Preservation of the knee joint in a patient undergoing lower limb amputation for critical ischaemia is associated with improved postoperative rehabilitation and mobility. Yet, for most surgeons the below-knee to above-knee amputation ratio remains less than one. Poor wound healing and a high reamputation rate for below knee stumps are important factors mitigating against below-knee amputations. Many tests (Doppler indices, segmental pressures, skin blood flow, skin perfusion pressure, TcpO2, thermography) have been described to predict the likelihood of successful healing of an amputation stump but none appears to have gained widespread acceptance. Clinical judgement alone is insufficient to predict the success or failure of an amputation stump. In this review, we have looked at the evidence in support of these tests, particularly those routinely available to most surgeons.

Developments in transcutaneous blood gas monitoring: a review

Transcutaneous measurements of oxygen (tcPO2) and carbon dioxide (tcPCO2) are useful in the intensive care unit because they provide continuous and non-invasive estimation of arterial blood gases. In patients with compromised peripheral blood flow the cutaneous values will reflect the haemodynamic changes as blood is shunted away. They have been increasingly used in a variety of clinical situations, such as assessment of skin flap viability, drug evaluation, prediction of wound healing and selection of amputation level in peripheral vascular disease. From a review of available literature it appears that transcutaneous monitors have found another application as indicator of local tissue perfusion.

One hundred percent oxygen reverses muscle hypoxia in a rat hindlimb model of acute arterial occlusion

Significant morbidity results from extremity ischemia after acute arterial occlusion. Reestablishment of arterial flow is considered to be the ideal treatment, yet substantial tissue loss can occur before this is accomplished. Using a rat hindlimb model we investigated whether the administration of 100% oxygen would decrease tissue hypoxia from acute arterial occlusion. Adult male Sprague-Dawley rats were used, and Po2 recordings were taken from the gastrocnemius muscle by use of an oxygen electrode. Baseline muscle Po2 was recorded, and then the femoral artery was occluded. Repeat recordings were made after 20 minutes of ventilation with room air and after an additional 20 minutes of ventilation with 100% oxygen (N = 10). Control groups consisted of animals undergoing occlusion but continued on room air (N = 3) and animals undergoing sham occlusion but receiving the period of 100% oxygen ventilation (N = 3). Femoral artery occlusion produced a reduction in muscle Po2 from 28.0 +/- 1.4 to 6.1 +/- 2.0 (mean +/- SEM, p less than 0.001). Ventilation with 100% oxygen reversed the tissue hypoxia produced by occlusion (27.3 +/- 2.0, p less than 0.001). The administration of 100% oxygen without femoral artery occlusion resulted in a higher tissue Po2 than the occluded + oxygen group (94 +/- 12 vs 27.3 +/- 2.0, p less than 0.001). Mean arterial blood pressure increased in the experimental group concomitant with the administration of 100% oxygen, but there was no correlation between final blood pressure and final tissue oxygen tension.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulse oximetry: a new non-invasive assessment of peripheral arterial occlusive disease

Peripheral skin perfusion reflects the level of vascularity and viability of a limb and may help in planning the site of amputation or bypass surgery in patients with vascular disease. This study used peripheral pulse oximetry in 20 healthy volunteers and in 20 patients with limb ischaemia. Pulse oximetry saturation levels (Psa,O2) were compared with ankle artery Doppler pressures and transcutaneous oxygen measurements (Ptc,O2). Recordings were taken at two standard sites distally and referenced to finger and forearm to calculate an index. A significant correlation was found between Ptc,O2 and Psa,O2 in patients with ischaemia (r = 0.68, P less than 0.01). A further group of 12 patients with acute limb ischaemia was similarly assessed before and after revascularization. After revascularization mean(s.d.) Ptc,O2 increased from 38(13) to 44(1) mmHg (P greater than 0.05) and mean(s.d.) Psa,O2 increased from 86(3) to 90(4) per cent (P less than 0.01). These data suggest that pulse oximetry is a more sensitive index of peripheral perfusion than Ptc,O2 or ankle artery Doppler pressure and that, because of its accuracy and simplicity, it merits further use.

The influence of central haemodynamics on transcutaneous oxygen (TcpO2) measurements

Transcutaneous oxygen measurements (TcpO2) have been shown to be an index of tissue perfusion and it has been suggested that the main haemodynamic variable influencing tissue perfusion is cardiac output, assuming that inspired oxygen remains constant. To investigate this hypothesis we studied 23 consecutive patients in order to identify if changes in cardiac output correlated with similar changes in TcpO2 measurements. No correlation was found to suggest that cardiac output was the main haemodynamic determinant of TcpO2 measurements.

Intraoperative transcutaneous oxygen tension criteria for completion arteriography

During the past three years, we studied the value of transcutaneous oxygen monitoring in 28 lower extremity vascular bypass procedures. In 21 reconstructions, a rapid rise in the transcutaneous oxygen tension following reperfusion was indicative of a patent graft and patent runoff vessels. Inadequate revascularization was identified in three of four patients in whom transcutaneous oxygen tension failed to rise following femorodistal arterial bypass (positive predictive value 75%). A normal intraoperative transcutaneous oxygen tension study following femorodistal bypass had a negative predictive value of 95%. The overall accuracy was 91%. Transcutaneous oxygen tension monitoring during lower extremity vascular bypass procedures is useful in assessing the success of revascularization and may be used to select which patients should undergo completion arteriography as opposed to those in whom an arteriogram is not essential.

A multivariate analysis of determinants of wound healing in patients after amputation for peripheral vascular disease

In a prospective study 53 patients undergoing amputations of the lower limb were evaluated for clinical criteria, laboratory results, pulse volume recordings, Doppler pressures, Photoplethysmographic Skin Perfusion Pressures (PPG/SPP) and angiography. The purpose of the study was to analyse which of these techniques predicts wound healing adequately after amputation. Forty-five patients eventually completed all tests. With the exception of PPG/SPP none of these tests were able to predict skin healing. The technique of PPG/SPP proved very reliable in helping to select the level of amputation, if measured anteriorly (P = 0.0001, r = 0.83). Angiographic scoring also correlated significantly (P = 0.0016) with a successful result. This study suggests that surgeons should not rely on their clinical acumen for the selection of the amputation level. In the absence of a reliable non-invasive test, angiography may well be useful but PPG/SPP will enable the surgeon to amputate on an optimal level and thus reduce complications and improve rehabilitation.

Acute lower limb arterial ischaemia: a role for continuous oxygen inhalation

Simultaneous readings of transcutaneous partial pressure of oxygen (Ptc,O2) were obtained from the left anterior chest wall, from 10 cm distal to the medial aspect of the knee joint, and from the first dorsal webspace in 16 patients with acute peripheral arterial ischaemia of the leg. Oxygen was administered at concentrations of 24, 40, 60 and 100 per cent. Mean (s.d.) initial chest Ptc,O2 (53(17)mmHg) was significantly higher than that of the medial lower limb site (37(17)mmHg). After inhalation of 24 per cent oxygen, a statistically significant (P less than 0.025) increase in chest Ptc,O2 was achieved (63(20)mmHg), but the increase in Ptc,O2 (43(19)mmHg) at the medial lower limb site was not statistically significant. Inhalation of 40 per cent oxygen resulted in significant increases at both sites (chest: 83(23)mmHg, P less than 0.01; limb: 53(26)mmHg, P less than 0.05). Ptc,O2 in the limb at this concentration of inhaled oxygen was equal to the initial chest level. Increasing the oxygen concentration to 60 per cent and then to 100 per cent produced further significant (P less than 0.001) increases in Ptc,O2 at both sites. The use of continuous oxygen inhalation during acute ischaemia may improve tissue nutrition before, during and after definitive treatment.

Transcutaneous oxygen tension (TcPO2) measurement as a diagnostic tool in patients with peripheral vascular disease

Transcutaneous oxygen tension (TcPO2) was measured through Clark's electrode at the dorsum of the foot in 52 healthy controls whose ages ranged from twenty to sixty-five years (mean 45.05 +/- 14.09) and 36 nondiabetic patients with peripheral vascular disease (PVD) (5 stage I, 16 stage II, 4 stage III, 11 stage IV), under standardized conditions at rest and during recovery from limb ischemia obtained with pneumatic cuff compression for 3 minutes. At rest the TcPO2 averaged 71.20 +/- 14.26 mm Hg (range 46-92) in the controls and 51.56 +/- 26.38 in the PVD patients (p less than .01). A wide overlap was observed between the two groups and among the different stages of the disease, and consequently, the diagnostic value of TcPO2 at rest was limited (sensitivity equal to 32%). During the recovery from ischemia the time constant (recovery half-time, T1/2) averaged 38.01 +/- 7.23 sec in the controls and 55.84 +/- 19.82 in the PVD patients (p less than .01). The T1/2 added to the diagnostic value of the method, making it more sensitive (55%), especially for stage II patients. The TcPO2 at rest was lower with increasing severity of the disease; both the TcPO2 at rest and the T1/2 correlated with the ankle-arm pressure index in the diseased limbs (r = .48 and -.41 respectively, p less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of peripheral vascular obliterative disease by transcutaneous oxygen tension tests

By repeated measurements in each of ten normal subjects and ten patients with mild intermittent claudication, the performance of three transcutaneous oxygen tension (PtcO2) test in the diagnosis of obliterative peripheral arterial disease was studied. PtcO2 resting value, PtcO2 response to oxygen breathing and PtcO2 reperfusion response after tourniquet obstruction were all measured on the dorsum of the foot. We found that PtcO2 resting values were not different between patients and controls, while responses to 100% oxygen breathing and reperfusion responses differed significantly between the two groups. The most prominent difference between the two groups was observed in the latency of PtcO2 rise after reperfusion. Therefore the reperfusion response test may have a place in the assessment of claudication by PtcO2 measurement.

Oxygen tension measurements using an oxygen polarographic electrode sealed in an implantable silastic tonometer: a new technique

Our new method is comparable to the standard, "open-end" tonometer system and incorporates all its abilities to monitor oxygen tension and perfusion. The new device has the advantage of being completely sealed, providing a true, continuous direct measurement over several days, with freedom of movement for the patient without operator attention and with improved stability of the electrode, which minimizes the drift artifacts previously encountered. These improvements will facilitate routine clinical monitoring of tissue oxygen tension.

The effect of adjuvant oxygen therapy on transcutaneous pO2 and healing in the below-knee amputee

The effects on tissue oxygenation of postoperative adjuvant oxygen have been studied in a group of 20 patients undergoing below-knee (BK) amputation for vascular disease. Ten patients received no therapy, the remainder receiving 28% oxygen for 48 hours following surgery. The results showed that the transcutaneous pO2 in the amputation flaps fell significantly by some 20 mmHg (p less than 0.01) following surgery and that this fall was prevented by the use of adjuvant oxygen. The fall was not observed in the non-amputated limbs. TcpO2 took almost two weeks to reach its pre-operative levels in the amputated limbs. The effect on stump healing of adjuvant oxygen therapy was investigated in a randomized controlled trial in a series of 39 patients undergoing BK amputation. There were 22 patients in the control (untreated) group and 17 in the treated group (adjuvant oxygen for 48 hours). In the treated group 14 patients healed primarily and three amputations failed. In the untreated group 14 limbs healed primarily, one secondarily and there were 7 failures. The pre-operative transcutaneous values in the stumps which failed (26 mmHg +/- 14) was significantly lower (p less than 0.005) than in those which healed (40 mmHg +/- 9). The mean pre-operative TcpO2 in the patients in whom healing occurred in the treated group (35 mmHg +/- 10) was significantly lower (p less than 0.001) than the mean pressure observed in the untreated group (44 mmHg +/- 9).