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O Objective: To investigate the threshold of transcutaneous oxygen tension (TcPO ) values in predicting
ulcer healing in patients with critical limb ischaemia in a prospective study.
O Method: 50 patients suffering from critical limb ischaemia with chronic ischemic ulcers or gangrenous
toes were enrolled in this study between January and December 2008. Their demographic data and
ankle brachial pressure index (ABPI) were collected. Baseline ulcers were measured with a wound
measurement system (Visitrak, Smith & Nephew). TcPO was measured at rest in the supine position
and with 30° leg elevation. The patients with infective and ischemic ulcers underwent debridement and
gangrenous toes were amputated. Ulcer outcome was classified as either: (1) A healing ulcer, showing
good epithelialisation or granulation at both base and edges, or a decrease in ulcer area during the study;
or (2) A non-healing ulcer, showing poor granulation tissue formation or a pale base and necrotic edges,
or deterioration in an ischaemic ulcer.
O Results: The mean age of the patients was 67.6 ± 10.8 years. The most common risk factor was
hypertension (90%). Mean ABPI was 0.75 ± 0.39. 13 patients (26%) had a TcPO of less than 20mmHg, of
which none showed any improvement in ulcer healing (p<0.001). 15 patients (30%) had a TcPO of more than 40mmHg, of which all progressed to complete ulcer healing (p<0.001). In the borderline group (20–40mmHg, 22 patients, 44%), 10 patients (45%) had a TcPO drop of <10mmHg with 30° leg elevation, of which 8 achieved complete ulcer healing (p<0.001). 12 patients (55%) had a TcPO drop of >10mmHg with 30° leg elevation, of which 11 showed no ulcer healing (p<0.001).
O Conclusion: TcPO measurement is an accurate, non-invasive, and good predictor of ischemic ulcer
healing, for cut-off TcPO values of less than 20mmHg and more than 40mmHg. In addition, the leg elevation method for TcPO might provide an important adjunct in the assessment of patients with borderline values.
O Declaration of interest: None.
transcutaneous oxygen tension; critical limb ischaemia; ulcer healing C. Ruangsetakit, MD;
K. Chinsakchai MD;
P. Mahawongkajit, MD;
C. Wongwanit, MD;
P. Mutirangura, MD;
all at the Vascular Surgery
Peripheral arterial occlusive disease such as those with diabetes mellitus or chronic renal (PAOD) is a common manifestation of failure and medial arterial calcification.1,4,5 In addi-systemic atherosclerosis. Most patients tion, both tibial arteries may be occluded, making with PAOD develop chronic ischaemic ankle pressure assessment impractical.6 While toe ulcers, gangrene and rest pain, defined blood pressure measurement can be used with calci- as critical limb ischaemia.1 In 2007, the TransAtlan- fied tibial arteries, its use is limited in patients with tic Inter-Society Consensus (TASC II) defined objec- tive criteria for the diagnosis of critical limb ischae- In contrast, it is much easier to measure the TcPO mia as: ankle pressure <50mmHg, or toe pressure at the dorsum of the foot in patients with critical <30mmHg, or transcutaneous oxygen tension limb ischaemia. This can be used to assess both local arterial blood flow and skin oxygenation.7 Factors influencing ulcer healing include local At present, there is no consensus on the TcPO skin macro- and microcirculation and tissue oxy- value that should be used to determine whether genation surrounding the ulcer.2 Peripheral pulse healing is likely to occur or whether revascularisa-examination and ankle brachial pressure index tion is indicated, with a range of 25–40mmHg being (ABPI) measurement are commonly used in assess- ing limb macrocirculation, but they cannot predict This prospective study aimed to investigate the whether or not the ulcer will heal.3 Furthermore, diagnostic efficacy and threshold of transcutaneous ankle pressure measurement is not easily achieved oxygen tension values in predicting ulcer healing in in patients with poorly compressible tibial arteries, patients with critical limb ischaemia.
J O U R N A L O F WO U N D C A R E VO L 1 9 , N O 5 , M AY 2 0 1 0
utes. An estimated barometric pressure of 730mmHg References
Table 1. Inclusion and exclusion criteria
was used for standard calibration at the geographic 1 Norgren, L., Hiatt, W.R.,
location.
Inclusion criteria
The measuring site was carefully cleaned with management of peripheral saline. Transducers were fixed to the skin with dou- Patients with PAOD diagnosis presenting with chronic ble-sided adhesive rings and contact liquid supplied 2007; 33: (Suppl. 1), S1-75.
by the manufacturer. A reference electrode was 2 Kalani, M., Brismar, K.,
applied to the chest wall in the left second intercos- tal space, in the mid-clavicular line. A second elec- Exclusion criteria
trode was placed on the dorsum of the foot at the pressure as predictors for Patients with conditions that affect the TcPO value periwound site, avoiding any large veins, hair, skin ulcers. Diabetes Care 1999; Electrodes were then heated to 45°C — the heat 3 Ballard JL, Eke CC, Bunt
Unstable vital signs or signs of poor tissue perfusion from electrodes caused the underlying capillaries to TJ, Killeen JD. A prospective dilate, increasing local perfusion and opening the Vasoactive drugs (vasoconstrictor or vasodilator) skin pores. The diffusion of oxygen through the measurements in the skin to electrodes and subsequent changes in partial management of diabetic Patient with asthma or COPD with pulse oximetry oxygen saturation <92% at room temperature pressure (pO ) generated a current. This was meas- ured and TcPO values were generated on a monitor. 4 Al-Qaisi, M., Nott, D.M.,
Drinking caffeine within 2 hours before testing Values were recorded at the 15th minute, resting King, D.H., Kaddoura, S. supine, and at the 5th minute following 30° leg ele- In the present study, we have used the cut-off rest- ing values of transcutaneous pressure measurement 5 Faglia, E., Clerici, G.,
in amputated patients studied by Bacharach et al.7 Caminiti, M. et al. Predictive Inability to lie supine for the period of testing and five-minute 30° leg elevation values, that have values of transcutaneous previously been described as a useful measure in the-ankle amputation in The patients were divided into three groups critical limb ischemia. Eur J according to their resting, supine values: O Group 1: patients with a TcPO value <20mmHg 6 Emanuele, M.A.,
O Group 2: patients with a TcPO of 20–40mmHg Patients
O Group 3: patients with a TcPO value >40mmHg.
Between January 2008 and December 2008, 149 Group 2 was further divided into two subgroups, calcification in diabetic patients at Siriraj Hospital were diagnosed with crit- based on leg elevation values: subgroup 1 comprised occlusive vascular disease. ical limb ischaemia. Of these, 50 were enrolled in patients whose TcPO decreased by <10mmg and 289-292.
this study. The inclusion and exclusion criteria are subgroup 2 as patients whose TcPO decreased by The Siriraj ethical committee for research in After TcPO measurements, all ischaemic and humans approved this study and written informed infected ulcers were debrided, while a vascular sur-consent was received from all participants.
gery care team performed minor amputations on patients with gangrenous toes. Individualised topi- Study procedure
The patients’ demographic data were collected and
physical examinations were performed. ABPI was
measured to determine the site and severity of arte-
rial occlusion. Baseline ulcer characteristics were
measured using Visitrak (Smith & Nephew) each
week during admission and every 4–6 weeks during
regular outpatient visits. Ulcer area was calculated
through manual tracing, as described in previous
studies.10,11
All patients underwent TcPO measurement using a TCM400 (multi-channel TcPO monitor, Radio- meter America). Patients lay supine in a quiet room where the temperature was carefully controlled (21–23°C). During this procedure, the transcutaneous oxygen tension electrode was calibrated for 15 min- Fig 1. An electrode was placed on the periwound area
J O U R N A L O F WO U N D C A R E VO L 1 9 , N O 5 , M AY 2 0 1 0
Fig 2. A 72-year-old female presented with a non-healing ulcer and second gangrenous toe. Her diagnosis was femoropopliteal arterial
occlusive disease; ABPI was 0.70 but TcPO was 32mmHg in the supine position and 26mmHg for leg elevation (a). A 70-year-old female
presented with rest pain and fifth gangrenous toe. Her diagnosis was aorto-iliac arterial occlusive disease; ABPI was 0.20 but TcPO was
50mmHg (b). Both ulcers were successfully complete healing after toe amputation and local wound dressing.
cal treatments and dressing changes were used, The most common risk factor was hypertension. depending on the site and character of ulcers. Most patients (40%) were diagnosed with multilevel Ulcer outcomes were classified within two weeks arterial occlusive disease.
TcPO values are illustrated in Fig 3, which shows O A healing ulcer, defined as having good epitheli- that most patients had values of 11–20mmHg. The alisation or granulation at both base and edges,13,14 outcomes for different groups are presented in Table or a decrease in ulcer area during the study (Fig 2)11 3. None of patients with a TcPO of <20mmHg O A non-healing ulcer, defined as having poor gran- (group 1) showed signs of ulcer healing, whereas all ulation tissue formation or a pale base and necrotic of the patients with a TcPO of >40mmHg (group 3) edges, or deterioration in an ischaemic ulcer.13,14 showed a progression towards healing during the In equivocal cases, ulcers were re-evaluated within study period (p<0.001). In the borderline group (20– two weeks using this same method. However, we 40mmHg, group 2), 10 patients had a decrease in decided to perform urgent revascularisation in TcPO of <10mmHg with leg elevation (subgroup 1), patients who developed ischaemia or rest pain. of whom eight (80%) healed (p<0.001). In contrast, We analysed TcPO values and outcomes in all 12 patients had a decrease in TcPO2 of >10mmHg patients to determine the statistical significance of with leg elevation (subgroup 2), and 11 of these ulcer-healing predictions.
Statistical analysis
Descriptive data analyses are given as mean ± stand- Using peripheral pulses or ankle or toe pressure ard deviation for continuous data or as percentages measurements alone to predict ischaemic ulcer heal-for discrete variables. The Chi-square test was used ing has limitations.3 This has led to numerous efforts to compare TcPO data between the two ulcer out- to find a complementary technique that would comes. A value of p<0.05 was considered to be sta- allow for more accurate predictions. Our results sug- tistically significant. Statistical analysis was con- gest that TcPO values of <20mmHg or >40mmHg ducted with SPSS software version 16 (SPSS Inc, when supine, and leg elevation TcPO values of 20–40mmHg are clinically useful in predicting heal-ing outcomes in patients with critical limb ischae- Fifty patients met the criteria for TcPO measure- ABPI measurement is a simple, non-invasive and ment. Gender, age, presenting symptom, risk factor, reproducible test for evaluating the severity of ABPI and level of occlusion are summarised in Table PAOD.15,16 However, its use is limited in patients 2, which shows that most patients presented with with calcified or distally occluded tibial arteries.1,5,6,8 an ischaemic ulcer on the toes or a gangrenous toe. Furthermore, it may fail to unmask the underlying J O U R N A L O F WO U N D C A R E VO L 1 9 , N O 5 , M AY 2 0 1 0
problem in a high-grade aorto-iliac stenosis, or where an occlusion has a rich collateral network.17 Table 2. Patient demographics and clinical
Therefore, ABPI is not sufficient when making a characteristics
At present, a variety of TcPO values are used to predict whether or not an ulcer will heal.1,2,5,8 In TASC II, it was stated that a TcPO of <30mmHg was a clear sign of a non-healing ischaemic ulcer.1 Kalani et al.2 proposed that the probability of ulcer healing Presenting symptom
was low when TcPO was <25mmHg. In addition, they found that all patients with a TcPO of >38mmHg showed improved ulcer healing and none with a TcPO of <13mmHg improved.2 Anoth- er study concluded that a TcPO of <34 mmHg indi- cated the need for revascularisation.5 Fife et al.8 dem- onstrated that a TcPO of <40mmHg was associated with a reduced likelihood of amputation healing. Based on our data, TcPO values of <20mmHg and Risk factor
>40mmHg can accurately predict ulcer healing out- comes. Furthermore, we have been able to correctly predict more than 80% of outcomes for patients with TcPO values of 20–40mmHg (group 2). Although these values have previously been used to assess amputated patients,7 they may be applicable to outcomes in patients with critical limb ischaemia, chronic ischaemic ulcers and ulcers following gan- grenous toe amputation, as examined here.
Level of occlusion
When assessing ulcers, we have regarded healthy granulation tissue at the base or edges to be an indi- cation of healing.13 In addition, we have evaluated outcomes within 2–4 weeks, which is consistent with Keast et al.,11 who showed that the percentage decrease in ulcer area (measured with the Visitrak system) during that period was a predictor of heal- Most patients with critical limb ischaemia will be at increased operative risk because of diabetes mel- Results are presented as mean ± SD, unless otherwise stated litus, coronary heart disease or chronic renal failure. Nevertheless, some are suitable for revascularisa-tion. This study demonstrates that surgical or endovascular revascularisation is not obligatory, especially in patients with a TcPO >40mmHg. In fact, conservative treatment in this group is not Fig 3. TcPO values of all patients included in the study
only cost-effective, but also free of the risks of intra- or postoperative complications. However, patients with a TcPO of <20mmHg should receive either sur- gical or endovascular treatment, depending on patient status and severity of PAOD. Treatment guidelines for different cut-off TcPO values are A significant limitation of TcPO measurement is that it takes 45 minutes to do, compared with less o. of patients
than 10 minutes for ABPI. In addition, cellulitis or significant foot oedema may confound the accuracy of TcPO measurement. In practice, if TcPO values are <20mmHg in these patients, the test should be repeated following bed rest, leg elevation, intrave- TcPO (mmHg)
nous antibiotics and resolution of any oedema.3 J O U R N A L O F WO U N D C A R E VO L 1 9 , N O 5 , M AY 2 0 1 0
group 2. Therefore, this case may have involved Table 3. Outcome of TcPO measurement.
inadequate microcirculation and tissue oxygenation for successful healing, following toe amputation. Outcome data
Healed Non-healed Total p value
The second case was a 76-year-old male cigarette smoker with hypertension, diabetes mellitus and dyslipidemia, who presented with right femoropop- liteal arterial occlusive disease and a non-healing ischaemic ulcer over the lateral aspect of the right foot. The TcPO was 34mmHg supine and 24mmHg with leg elevation. The TcPO drop (10mmHg) was borderline, and his ulcer did not heal.
Also of note, one of the 12 patients in group 2, subgroup 2, whose TcPO fell by >10mmHg during leg elevation healed. This patient was a 56-year-old male smoker suffering from hypertension, diabetes mellitus and dyslipidemia, who presented with left femoropopliteal arterial occlusive disease and a non- Table 4. Guidelines for elective management of critical limb
healing ischaemic ulcer on the medial aspect of the ischaemia in patients with ischaemic foot ulcers or gangrene of
left foot. The TcPO value was 37mmHg supine and 14mmHg with leg elevation. The resting, supine TcPO value of 37mmHg was near the upper range Group 1: TcPO <20mmHg
for group 2, hence, microcirculation and tissue oxy- Plan for revascularisation, either surgical or endovascular treatment, depending on genation were probably adequate for ulcer healing. the status of patient and severity of disease In future studies, it might be possible to use differ-ent, more accurate TcPO values to evaluate ulcer Group 2: TcPO 20–40mmHg (30° leg elevation)
O Subgroup 1 (TcPO change <10mmHg): local wound care, wound debridement, The present study was limited by its small sample size, lack of randomisation with other investiga-tions, and its relatively short-term nature. In future O Subgroup 2 (TcPO change >10mmHg): plan for revascularisation, either surgical studies, larger sample sizes might be investigated, or endovascular treatment, depending on status of patient and severity of disease with randomisation, and patients should be moni- Group 3: TcPO >40mmHg
Local wound care, wound debridement or minor toe amputation ConclusionTcPO measurement is an accurate, non-invasive, and good predictor of ischemic ulcer healing where Two patients in group 2 had a reduction in TcPO TcPO values are less than 20mmHg or more than of <10mmHg during leg elevation (subgroup 1) but 40mmHg. In addition, the leg elevation method their ischemic ulcers did not heal. The first case was might provide an important adjunct when assessing a 79-year-old female cigarette smoker with diabetes patients with borderline TcPO values. This simple mellitus. She presented with aorto-iliac arterial test can be used to select appropriate treatment for occlusive disease and a gangrenous toe. The TcPO patients with critical limb ischaemia and help avoid value was 20mmHg supine and 17mmHg during leg intra- and postoperative complications in those elevation (TcPO decrease = 3mmHg). The supine with TcPO values greater than 40mmHg, who can TcPO value (20mmHg) was in the lower range of be managed without revascularisation. Q 7 Bacharach, J.M., Rooke, T.W.,
10 Sugama, J., Matsui, Y., Sanada, H.
13 Grey, J.E., Enoch, S., Harding, K.
16 Johnston, K.W., Hosang, M.Y.,
8 Fife, C.E., Smart, D.R., Sheffield,
11 Keast, D.H., Bowering, C.K.,
14 Lazarus, G.S., Cooper, D.M.,
17 Dormandy, J.A. [Epidemiology
9 Bunt, T.J., Holloway, G.A. TcPO2
15 Fowkes, F.G., Housley, E.,
12 Shah, J.B., Ram, D.M., Fredrick,
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Source: http://mss.co.th/pdf/journal/J_WoundCare19_2010_TCM400.pdf