Reliability of Laser Doppler Flowmetry Curve Reading for Measurement of Toe and Ankle Pressures: Intra- and Inter-observer Variation

Digital pressure with laser Doppler flowmetry is better than photoplethysmography to characterize peripheral arterial disease of the upper limbs in end-stage renal disease patients

OBJECTIVE

There is no consensual definition of significant peripheral arterial disease of the upper limbs. Patients with end-stage renal disease are usually explored with Doppler ultrasound, which seems insufficient to characterize and quantify the arterial disease in this anatomic site. Candidates for haemodialysis access tend to be increasingly older and have polyvascular disease, and a better assessment of the vascular status of their upper limbs with finger systolic blood pressure is necessary. Photoplethysmography is simple and currently used in practice, but laser Doppler flowmetry may be more sensitive for low values. Our objective is to investigate additional information in the digit assessment over the ultrasound assessment of the upper limbs of patients awaiting haemodialysis and compare digital pressure values taken by photoplethysmography and laser Doppler.

METHODS

All included patients with end-stage renal disease scheduled for haemodialysis access received a prospective evaluation of their upper limbs with a clinical examination of the hands, an arterial upper limb Doppler ultrasound, and finger systolic blood pressure using photoplethysmography and laser Doppler flowmetry. Significant upper limb arterial disease was defined by a finger systolic blood pressure below 60 mm Hg or a finger brachial pressure index below 0.7.

RESULTS

Twenty-four patients were included in the study. In all, 41.7% of patients (n = 10) had parietal calcifications to the antebrachial arteries on Doppler ultrasound, 8.3% of patients (n = 2) had bilateral finger systolic blood pressure values below 60 mm Hg with laser Doppler flowmetry (but not confirmed with photoplethysmography), and 16.6% of patients (n = 4) had a finger brachial pressure index below 0.7 on both laser Doppler flowmetry and photoplethysmography. While there was an agreement between these two methods, higher values were recorded with photoplethysmography. The Pearson coefficient was 0.493 for the median of basal digital pressures in absolute values and 0.489 for finger brachial pressure index (p < 0.001).

CONCLUSION

Our study confirms the need to evaluate significant upper limb arterial disease in patients with end-stage renal disease not only with Doppler ultrasound but also with an evaluation of the finger systolic blood pressure. The correlation of the finger systolic blood pressure values using laser Doppler flowmetry and photoplethysmography was poor, which was probably due to an overestimation of the pressures with photoplethysmography. Despite the absence of a gold standard, we suggest that Laser Doppler flowmetry should be used rather than photoplethysmography to better characterize significant peripheral arterial disease of the upper limbs in patients with end-stage renal disease, particularly before creation of a new haemodialysis access. Protocol Record on clinical trial 38RC19.285.

Performance of finger systolic blood pressure measurement to detect digital occlusive arterial disease in systemic sclerosis

OBJECTIVE

Digital ulcers (DUs) related to digital occlusive arterial disease (DOAD) are frequent in patients with systemic sclerosis (SSc). Finger systolic blood pressure (FSBP) and digital-brachial pressure index (DBI) using laser Doppler flowmetry constitute a non-invasive means of detecting DOAD in SSc, although thresholds have yet to be established for defining DOAD. The purpose of this study was to ascertain FSBP and DBI thresholds to detect DOAD in SSc patients. The intra/interday reproducibility of curve reading by 4 vascular physicians in relation to finger pressure measurement was also investigated.

METHODS

SSc patients were followed in this single-center study (Rennes University Hospital, France) between November 2017 and October 2019.Theses patients underwent tests before and after heating at two visits spaced 10 days apart. DOAD was diagnosed on the basis of post-warming skin blood flow of ≤ 206 arbitrary units measured by LDF, contingent on previous results validated by arteriography as a gold standard. An interday kappa coefficient with a 95% confidence interval was used to assess reproducibility.

RESULTS

16 (10 females; mean age: 63 ± 9 years) SSc patients were included. Mean time interval between visits was 9 ± 5 days. The best FSBP threshold for DOAD diagnosis was 76 mmHg and DBI was 0.74 after warming. FSBP and DBI sensitivity/specificity were 59.1%[49.6%; 68.5%]/92.5% [85.3%; 99.6%] and 73.3%[64.9%; 81.8%]/83.0% [72.9%; 93.1%] respectively. Intra/interday reproducibility ranged from fair to good.

CONCLUSION

The conclusions drawn from this study suggest that FSBP ≤ 76 mmHg and DBI ≤ 0.74 thresholds are potentially reliable indicators of DOAD and demonstrate fair to good intra and interday reproducibility.

Peripheral arterial disease screening and diagnostic practice: A scoping review

Early reliable, valid screening, diagnosis, and treatment improve peripheral arterial disease outcomes, yet screening and diagnostic practices vary across settings and specialties. A scoping literature review described reliability and validity of peripheral ischaemia diagnosis or screening tools. Clinical studies in the PUBMED database January 1, 1970, to August 13, 2018, were reviewed summarising ranges of reliability and validity of peripheral ischaemia diagnostic and screening tools for patients with non-neuropathic lower leg ischaemia. Peripheral ischaemia screening and diagnostic practices varied in parameters measured such as timing, frequency, setting, ordering clinicians, degree of invasiveness, costs, definitions, and cut-off points informing clinical and referral decisions. Traditional ankle/brachial systolic blood pressure index <0.9 was a reliable, valid lower leg ischaemia screening test to trigger specialist referral for detailed diagnosis. For patients with advanced peripheral ischaemia or calcified arteries, toe-brachial index, claudication, or invasive angiographic imaging techniques that can have complications were reliable, valid screening, and diagnostic tools to inform management decisions. Ankle/brachial index testing is sufficiently reliable and valid for use during routine examinations to improve timing and consistency of peripheral ischaemia screening, triggering prompt specialist referral for more reliable, accurate Doppler, or other diagnosis to inform treatment decisions.

Consistency of Toe Systolic Pressures, Brachial Systolic Pressures, and Toe-Brachial Indices in People with and without Diabetes

BACKGROUND & AIMS

Toe Systolic Blood Pressures (TSPs) and Toe-Brachial Indices (TBIs) have been identified as useful adjuncts in the identification of pedal ischemia, peripheral artery occlusive diseases, and risk for either nonhealing of lower extremity wounds or for amputation. Valid measurement of TSPs and TBIs is therefore essential. However, it could be jeopardized by rater, instrument, and intratestee inconsistency. These three sources of inconsistency were examined in this research.

METHODS

Five publications addressing TSP and TBI consistency were identified and their results were analyzed using intraclass correlation coefficients.

RESULTS

Moderate variability in TSPs was found across all studies; greater variability was evidenced in brachial systolic pressure, particularly for people who had diabetes; and TBI values also exhibited considerable variability, but little difference between people who did and did not have diabetes.

CONCLUSION

These findings provide qualified evidence of consistency regarding measurement of TSPs but challenge TBI as a valid and useful indicator in screening, prognostic, and monitoring contexts, particularly for people who have diabetes. However, there is a prospect that TBI assessment could be improved by adherence to standardized protocols and by obtaining multiple measurements from toes and arms on a single occasion as well as on different occasions.

Temporal (in)stability of suboptimal toe-brachial indices

OBJECTIVE

To be effective in screening, prognostic, and monitoring contexts, the toe-brachial index (TBI) should not be susceptible to large sporadic fluctuations from one time to another. In order to identify whether those fluctuations exist in people who have suboptimal TBIs, the temporal stability of their TBIs was examined in detail across 6 months.

METHODS

TBI readings from SysToe and Omron automated devices were taken from 21 participants at baseline and at 2- and 6-month timepoints subsequently. The primary inclusion criterion was that participants had at least one of three baseline TBIs on either foot ≤0.65 if a standard 25-mm wide occlusion cuff was used, or ≤0.85 if a 15-mm occlusion cuff was used.

RESULTS

After excluding five participants because of their extremely high TBI fluctuations, TBI stability within the remaining 16 participants was examined. Ipsilateral TBIs changed by ≥0.10 on at least one foot for 11 participants across the initial 2-month timespan (maximum difference 0.26) and for same number of participants across the full 6-month timespan (maximum difference 0.36), with the composition of the 11-person groups differing slightly for the two timespans. Contralateral differences were ≥0.10 for five participants across the 2-month timespan (maximum difference 0.26) and for nine participants across the 6-month timespan (maximum difference 0.42), again with some group overlap. The foot with the higher TBI at baseline remained so across the 6 months.

CONCLUSIONS

For many people with suboptimal TBIs there might be inherent ipsilateral and contralateral inconsistency among TBI readings. This threatens the effectiveness of TBIs for screening, prognostic, and monitoring purposes. In order to maximize the prospects of the TBI as a valuable metric, adherence to standard protocols should be observed and other prospects for the TBI to assess vascular supply to the foot more effectively should be considered.

Impairment of microcirculation and vascular responsiveness in adolescents with primary Raynaud phenomenon

BACKGROUND

Raynaud's phenomenon (RP) is a functional vascular disease, presenting with recurrent episodes of ischemia of extremities in response to cold and emotional stress. Investigating cutaneous microcirculation is an important tool in understanding the complex neuro-immuno-vascular interactions in its pathophysiological mechanisms. Since there is no available data on vascular responsiveness in RP in the paediatric population, we investigated skin perfusion and heat-induced hyperaemia in comparison with clinical severity and laboratory parameters of the disease.

METHODS

Fifty two adolescents (27 patients with primary RP and 25 age-matched healthy controls) were investigated in the study. Patients were divided into two groups according to the symptoms existing within the previous 2 months. Following baseline microcirculation measurement with Laser Doppler flowmetry (Periflux 5000 system), all subjects underwent local heating test at 42 °C and 44 °C. Besides routine laboratory parameters, immune-serological tests and the vasoactive sensory neuropeptides somatostatin and pituitary adenylate-cyclase activating polypeptide (PACAP) were measured.

RESULTS

Baseline perfusion measured in perfusion units (PU) at 32 °C was significantly lower in symptomatic RP patients (97.6 ± 22.4 PU) compared with both healthy volunteers (248.3 ± 23.5 PU, p < 0.001) and RP patients without symptoms (187.4 ± 24.9 PU, p < 0.05). After local heating to 42 °C maximum blood flow was significantly reduced in primary RP participants with current symptoms (358.6 ± 43.9 PU, p < 0.001), but not in asymptomatic ones (482.3 ± 28.7 PU, p > 0.05) when compared with healthy subjects (555.9 ± 28.2 PU). Both the area under the response curve and the latency to reach the maximum flow were significantly increased in both RP groups (symptomatic 164.6 ± 7.4 s, p < 0.001, asymptomatic 236.4 ± 17.4 s, p < 0.001) when compared with the control group (101.9 ± 4.7 s). The heat-induced percentage increase from baseline to maximal blood flow was significantly greater in symptomatic RP adolescents in comparison with healthy ones. Laboratory parameters and neuropeptide plasma levels were not altered in any groups.

CONCLUSION

To our knowledge this is the first study in paediatric population to show altered heat-induced cutaneous hyperaemia responses in relation with the clinical severity and symptomatology.

Measurement of Toe-Brachial Indices in People with Subnormal Toe Pressures Complexities and Revelations

BACKGROUND

Insufficient information exists about the nature of toe-brachial indices (TBIs) and how best to obtain them, yet their validity may be particularly important for the identification and management of peripheral artery disease and cardiovascular disease risk. We explore ways in which valid TBI measurements might be obtained.

METHODS

The TBI data were recorded from 97 people with subnormal toe pressures. Most people provided three TBI readings from each foot on six different occasions over a 6-month period. The foot with the lower baseline TBI was noted.

RESULTS

For most people, only small inconsistencies existed among the three readings taken from each foot on a single occasion, and there were no consistent differences based on sequence. However, for some people there were noticeable and unsystematic differences among the measures. Selecting any specific one of the three readings based on its sequential position, or averaging specific readings, did not yield TBIs that were unequivocally typical for a person, and taking the lowest reading of each set seemed to offer the most expedient solution in this context. That permitted baseline descriptive statistics to be produced for both the higher and lower pressure feet, between which there was a statistically significant TBI difference.

CONCLUSIONS

Accurate and consistent TBI readings cannot be assumed for people with subnormal toe pressures, and taking only a single reading or indiscriminately averaging readings seems inadvisable. Two readings and, if they are discrepant, additional readings, are recommended for each foot, ideally on several occasions, and careful consideration should be given to determine the most representative reading for each foot. Cuff sizes and other sources of inaccuracy or distortion should not be ignored, and standardized protocols for obtaining TBIs are recommended.

Subjecting the ankle-brachial index to timely scrutiny: is it time to say goodbye to the ABI?

Although the ankle-brachial index (ABI) has been used as an indicator of peripheral artery disease and vascular supply to the foot for over 50 years, it is now associated with reservations and qualifying empirical evidence to the extent that the provocative step of abandoning it totally might be advisable. In this article, the results of three publications concerning the ABI are initially described in some depth and the results from eight additional publications are then summarized more briefly. Cumulatively, the research indicates that ABIs that seem to be normal, as well as those in the subnormal range, are often inflated by medial arterial calcification and can therefore produce a high proportion of false-negative screening test results for arterial disease as well as a misleadingly high impression of vascular sufficiency to the lower extremity. The toe-brachial index is suggested as being likely to overcome the problems associated with the ABI, and other alternatives to the ABI and TBI are acknowledged.

Comparison of two methods based on photoplethysmography for the diagnosis of peripheral arterial disease

AIM

To examine the interchangeability of two methods for distal pressure measurement based on photoplethysmography using a truncated or full display of the arterial inflow curve, respectively.

METHODS

Toe and ankle pressures were obtained from 69 patients suspected of peripheral arterial disease (PAD). Observer reproducibility of the curve readings was examined by blinded reassessment of the pressure curves in a randomly selected subgroup (60 limbs).

RESULTS

There were no significant differences in mean pressures between the two methods (p for all > .455). The limits of agreement for the differences were -15.0-15.4 mmHg for right toe pressures, -16.3-16.2 mmHg for left toe pressures, -14.2-15.7 mmHg for right ankle pressures, and -18.3-17.7 mmHg for left ankle pressures. Correlation analysis revealed intraclass correlation coefficients ≥0.960 for all measuring sites. Cohen's Kappa showed excellent agreement in diagnostic classification, with κ = 0.930 for the diagnosis of PAD and perfect agreement in the diagnosis of critical limb ischemia (κ = 1.000). The analysis of intra-observer variation for curve reading showed limits of agreement of -3.9-4.0 for toe pressures and -7.6-7.7 for ankle pressures for the method involving truncated display and -3.1-3.2 for toe pressures and -6.3-8.6 for ankle pressures for the method involving full display of the signal.

CONCLUSION

The present study shows minimal differences in diagnostic classification, as well as in ankle and toe pressures, between the full display and the truncated display of the photoplethysmographic pulse signal. Furthermore, the inter-observer variation was low for both of the photoplethysmographic methods investigated.