Sleep Apnea-Specific Hypoxic Burden, Symptom Subtypes, and Risk of Cardiovascular Events and All-Cause Mortality.

Rationale: Data from population-based cohorts suggest that symptom subtypes and obstructive sleep apnea (OSA)-specific hypoxic burden (HB) could help to better identify patients with OSA at high cardiovascular (CV) risk. Objectives: We aimed to evaluate whether those new markers are associated with the risk of major adverse CV events (MACE) in clinical setting. Methods: Data from the Pays de la Loire cohort were linked to health administrative data to identify the occurrence of MACE (a composite outcome including all-cause mortality, acute myocardial infarction, stroke, and unplanned coronary revascularization) in patients with newly diagnosed OSA and no overt CV disease. Latent class analysis was used to identify subtypes based on eight clinically relevant variables. HB was defined as the total area under the respiratory event-related desaturation curve. Cox proportional hazards models were used to evaluate the association of symptom subtypes and HB with MACE. Measurements and Main Results: Four symptom subtypes were identified (minimally symptomatic [22.0%], disturbed sleep [17.5%], excessively sleepy [49.8%], and moderately sleepy [10.6%]). After a median follow-up of 78 months (interquartile range, 52-109), 592 (11.05%) of 5,358 patients experienced MACE. In a fully adjusted model, HB and overall nocturnal hypoxemia assessed by sleep time with oxygen saturation <90% were the only predictors of MACE (hazard ratio, 1.21; 95% confidence interval, 1.07-1.38; and hazard ratio, 1.34; 95% confidence interval, 1.16-1.55, respectively). The association appeared stronger toward younger patients and women. Conclusion: In clinical setting, patients with OSA who demonstrate elevated OSA-specific HB are at higher risk of a CV event and all-cause mortality. Symptom subtypes were not associated with MACE after adjustment for confounders.

Relationship Between the Severity of Exercise Induced Ischaemia and the Prevalence of Exercise Induced Calf Symptoms During Treadmill Testing With Transcutaneous Oximetry.

OBJECTIVE: It was hypothesised that there is a linear relationship between the severity of exercise induced calf ischaemia and the prevalence of calf claudication on a treadmill until a plateau is reached. It was expected that no pain would be present in the absence of ischaemia and all severely ischaemic calves would be symptomatic. METHODS: This was a retrospective analysis of a cross sectional acquired database recording. Transcutaneous oxygen pressure (TcPO2) on the chest and on each calf was used to evaluate calf ischaemia during treadmill tests with simultaneous recording of calf pain in 7 884 subjects (15 768 calves). The minimum value of calf changes from rest minus chest changes from rest (DROPm) was calculated. Regression analyses were used to determine the correlation between the proportion of exercise induced symptoms present in the calves and each unit of DROPm values. Analysis was repeated after objective determination of the cutoff point between the linear increase and the plateau. RESULTS: A linear relationship was found between the degree of ischaemia and the proportion of symptomatic calves for DROPm values ranging from 0 mmHg to -28 mmHg (proportion = -0.014 × DROPm + 0.32, r = 0.961, p <.001). For DROPm values lower than -28 mmHg (severe ischaemia), on average one of three limbs remained asymptomatic. The biphasic relationship between DROPm and prevalence of symptoms persists after exclusion of patients with diabetes mellitus, exercise induced hypoxaemia, and no evidence of lower extremity arterial disease (LEAD). CONCLUSION: The relationship between exercise induced pain and ischaemia is biphasic with a linear increase in the proportion of symptomatic limbs with ischaemia severity, until a plateau is reached for the more severely ischaemic limbs. The presence of exercise related calf symptoms should not automatically be reported as indicating the presence of LEAD; and the absence of exercise induced symptoms is not proof that ischaemia does not occur during exercise.

Calf and non-calf hemodynamic recovery in patients with arterial claudication: Implication for exercise training.

BACKGROUND: Previous studies in patients with arterial claudication have focused on calf hemodynamic recovery. We hypothesized that the duration of hemodynamic recovery with TcpO2 at calf and non-calf levels would be shorter than 10 min. We analyzed the factors that influence the recovery time. METHODS: We monitored limb changes minus chest changes from rest (DROP) of transcutaneous oximetry on buttocks, thighs and calves, during and following a treadmill test (3.2 km/h; 10% grade). We calculated the time required to reach 50% (50%RT) and 10% (90%RT) of minimal DROP value (DROPm) from walking cessation. Regression analyses were used to determine the factors associated to 50%RT and 90%RT. RESULTS: Of the 132 patients studied, 18.2% reported isolated non-calf pain by history. Of the 792 recovery time values, only 3 (0.4%) and 23 (2.9%) were in excess of 10 min for 50%RT and for 90%RT, respectively. A weak correlation was found between each of the 792 DROPm and 50%RT (r = -0.270, p < 0.001) as well as for 90%RT (r = -0.311 p < 0.001). Lowest DROPm and BMI (but not age, sex, the use of beta-blockers, the duration of the walking period) were associated to both 50%RT and 90%RT. CONCLUSION: Although recovery duration correlates significantly with the severity of ischemia of the same location, a wide discrepancy exists and the longest recovery time does not always correlate to the localization of the most severe ischemia. Non-calf ischemia should be measured when one aims at objectifying the biological effects of exercise or the effects of treatments on recovery from exercise.

Kneeling-induced calf ischemia: a pilot study in apparently healthy European young subjects.

PURPOSE: Many tasks, sports or leisure activities require maximal knee flexion. We hypothesized that this position could result in reduced calf perfusion, in young European subjects. METHODS: We quantified calf ischemia resulting from the knee flexion with transcutaneous oxygen pressure (TcpO2) sensors by assessing the decrease from rest of TcpO2 (DROP) defined as limb changes minus chest changes. A minimal DROP (DROPm) <-15 mmHg defines the presence of ischemia. From the crawling position, participants kneeled for 3 min while bending as in prostration/prayer position (P). Thirty-five participants repeated this maneuver a second time, while 7 participants were also required to sit on their heels with the torso in the vertical position to attain knee flexion without significant groin flexion (S). RESULT: In 41 healthy young volunteers (30 males), 25 [20-31] years old, 37 patients showed a DROPm < -15 mmHg from "R" to "P" in one (n = 4) or both (n = 33) calves (90.2%; 95% CI 76.9-97.3). After backward regression of the DROPm, there was no significant association with side, body weight of systolic blood pressure. However, age was strongly associated with DROPm (OR 5.34 [2.45-8.69]) so that DROPm was significantly higher in older, with a correlation ρ = 0.31 (p = 0.003). CONCLUSION: Kneeling dramatically reduces calf perfusion, likely through popliteal artery kinking, possibly through muscle crushing. Eastern lifestyle includes routine flexed position since childhood. Whether or not such a chronic training reduces the risk of kneeling-induced ischemia in adults is unknown to date.

Comparison of exercise oximetry and ankle pressure measurements for patients with intermittent claudication: an observational study of 433 patients.

To study the concordance of exercise-oximetry and of ankle-brachial pressure index (ABI) and ankle pressure (AP) at rest, and after exercise, in patients complaining of vascular-type claudication to diagnose lower extremity artery disease (LEAD). Treadmill test in 433 patients with exercise-oximetry included constant load (3.2 km/h, 10% slope) phase for up to 15 min followed by an increment phase, if necessary. The presence (TcpO2e+) or absence (TcpO2e-) of ischemia was a decrease of limb minus chest oxygen pressure change greater than or less than - 15 mmHg. The post-exercise ABI and AP were measured after another test of a maximum of 5 min except if resting-ABI < 0.90. LEAD was diagnosed (+) based on resting-ABI < 0.90, post-exercise ABI < 0.8∙resting-ABI, or a difference of 30 mmHg between post-exercise and resting AP, or diagnosis was considered negative for all other cases (-). The discrepancies between the exercise-oximetry and pressure results were analyzed. We found 351 patients with resting-ABI+, of whom 52 were classified as TcpO2e-. Of the 82 patients with resting-ABI-, 25 had post-exercise ABI+ or AP+, of whom, 10 had TcpO2e-, while 57 had post-exercise ABI- and AP-, of whom, 28 had TcpO2e+. Discrepancies arose mainly from nonvascular limitations, isolated proximal ischemia, and detection of LEAD in the incremental phase of the exercise-oximetry. Post-exercise pressure measurements were easy and useful, but exercise-oximetry provided additional information for both resting-ABI- and resting-ABI+ patients and can help to prove the vascular origin of walking limitation of LEAD patients.

Automatic identification of sleep and wakefulness using single-channel EEG and respiratory polygraphy signals for the diagnosis of obstructive sleep apnea.

Polysomnography (PSG) is necessary for the accurate estimation of total sleep time (TST) and the calculation of the apnea-hypopnea index (AHI). In type III home sleep apnea testing (HSAT), TST is overestimated because of the lack of electrophysiological sleep recordings. The aim of this study was to evaluate the accuracy and reliability of a novel automated sleep/wake scoring algorithm combining a single electroencephalogram (EEG) channel with actimetry and HSAT signals. The study included 160 patients investigated by PSG for suspected obstructive sleep apnea (OSA). Each PSG was recorded and scored manually using American Academy of Sleep Medicine (AASM) rules. The automatic sleep/wake-scoring algorithm was based on a single-channel EEG (FP2-A1) and the variability analysis of HSAT signals (airflow, snoring, actimetry, light and respiratory inductive plethysmography). Optimal detection thresholds were derived for each signal using a training set. Automatic and manual scorings were then compared epoch by epoch considering two states (sleep and wake). Cohen's kappa coefficient between the manual scoring and the proposed automatic algorithm was substantial, 0.74 ± 0.18, in separating wakefulness and sleep. The sensitivity, specificity and the positive and negative predictive values for the detection of wakefulness were 76.51% ± 21.67%, 95.48% ± 5.27%, 81.84% ± 15.42% and 93.85% ± 6.23% respectively. Compared with HSAT signals alone, AHI increased by 22.12% and 27 patients changed categories of OSA severity with the automatic sleep/wake-scoring algorithm. Automatic sleep/wake detection using a single-channel EEG combined with HSAT signals was a reliable method for TST estimation and improved AHI calculation compared with HSAT.

Identification of new factors associated to walking impairment in patients with vascular-type claudication.

OBJECTIVES: Mechanisms of walking limitation in arterial claudication are incompletely elucidated. We aimed to identify new variables associated to walking limitation in patients with claudication. METHODS: We retrospectively analyzed data of 1120 patients referred for transcutaneous exercise oxygen pressure recordings (TcpO2). The outcome measurement was the absolute walking time on treadmill (3.2 km/h, 10% slope). We used both: linear regression analysis and a non-linear analysis, combining support vector machines and genetic explanatory in 800 patients with the following resting variables: age, gender, body mass index, the presence of diabetes, minimal ankle to brachial index at rest, usual walking speed over 10 m (usual-pace), number of comorbid conditions, active smoking, resting heart rate, pre-test glycaemia and hemoglobin, beta-blocker use, and exercise-derived variables: minimal value of pulse oximetry, resting chest-TcpO2, decrease in chest TcpO2 during exercise, presence of buttock ischemia defined as a decrease from rest of oxygen pressure index ≤15 mmHg. We tested the models over 320 other patients. RESULTS: Independent variables associated to walking time, by decreasing importance in the models, were: age, ankle to brachial index, usual-pace; resting TcpO2, body mass index, smoking, buttock ischemia, heart rate and beta-blockers for the linear regression analysis, and were ankle to brachial index, age, body mass index, usual-pace, decrease in chest TcpO2, smoking, buttock ischemia, glycaemia, heart rate for the non-linear analysis. Testing of models over 320 new patients gave r = 0.509 for linear and 0.575 for non-linear analysis (both p < 0.05). CONCLUSION: Buttock ischemia, heart rate and usual-pace are new variables associated to walking time.

Transcutaneous Exercise Oximetry for Patients With Claudication　- A Retrospective Review of Approximately 5,000 Consecutive Tests Over 15 Years.

BACKGROUND: Exercise transcutaneous oximetry (Ex-tcPO2) is used to argue for the vascular origin of lower limb pain, especially at the proximal level, where the diagnosis of peripheral artery disease can be difficult. This study analyzed the principal indications, mean results, and limitations of Ex-tcPO2, as well as the relationship between the annual number of Ex-tcPO2 tests and internal iliac artery (IIA) revascularizations.Methods and Results:Data from our first 15 years' experience (3,631 patients, 5,080 tests) with Ex-tcPO2 were analyzed retrospectively using the minimal value of the decrease from rest of oxygen pressure (DROPmin). We had 99.7% of expected DROPminresults. The proportion of tests showing isolated proximal unilateral or bilateral ischemia ranged from ~5% to ~20%. A gradual increase with time was observed in both the annual number of Ex-tcPO2 tests (from 0 to ~500 per year) and the annual number of IIA revascularizations performed (from 0 up to 18 per year). At least 85% of patients (77/91) showed function improvement after IIA revascularization. CONCLUSIONS: Ex-tcPO2 (using DROPmin) provides an objective argument for exercise-induced ischemia, bilaterally at the distal and/or proximal level. Using Ex-tcPO2 has improved our diagnostic performance and markedly changed our therapeutic decisions, specifically for proximal claudication. The increased number of Ex-tcPO2 tests is associated with an increased number of IIA revascularizations, although a causal relationship was not proven.

Simultaneous pain intensity rating and quantification of ischemia throughout exercise and recovery in proximal versus distal arterial claudication.

Data on simultaneous hemodynamic changes and pain rating estimation in arterial claudication while walking are lacking. This study was conducted to determine if a difference in transcutaneous oxygen pressure (tc pO2) exists between proximal and distal localization at pain appearance (PAINapp), maximal pain (PAINmax) and pain relief (PAINrel) in proximal or distal claudication and if a relationship exists between tc pO2 changes and pain intensity. We analyzed the pain rating (Visual Analog Scale (VAS)) to lower limb ischemia, measured with the decrease from rest of oxygen pressure (DROP) tc pO2 index during constant-load treadmill tests in patients with calf ( n = 41) or buttock ( n = 19) claudication. Calves versus buttocks results were analyzed with ANOVA tests. The R2 correlation coefficient between individual VAS versus DROP was calculated. Ischemia intensity versus pain rating changes were correlated. Significant ischemia was required for pain appearance, but pain disappeared despite the persistence of ischemia. We observed no statistical difference for DROP at PAINapp, PAINmax or PAINrel between proximal or distal claudication. A significant correlation between pain rating versus DROP was found: from PAINapp to PAINmax, R2 = 0.750 (calves) and 0.829 (buttocks), and from PAINmax to PAINrel, R2 = 0.608 (calves) and 0.560 (buttocks); p<0.05. Pain appeared after a significant decrease of hemodynamic parameters but disappeared while parameters were not normalized. No difference in pain rating was found in proximal versus distal claudication.

Comparison of two devices for measuring exercise transcutaneous oxygen pressures in patients with claudication.

BACKGROUND: We aimed at estimating the agreement between the Medicap" (photo-optical) and Radiometer• (electrochemical) sensors during exercise transcutaneous oxygen pressure ( tcp02) tests. Our hypothesis was that although absolute starting values (tcp02rest: mean over 2 minutes) might)e different, tcpOTchanges over time and the minimal value of the decrease from rest of oxygen pressure (DROPmin) results at exercise shall be concordant between the two systems. taneously, one of each system on the chest, on each buttock and on each calf. RESULTS: Seventeen Medicap" probes disconnected during the tests. tcp02rest and DROPmin values were higher with Medicap• than with Radiometer•, by 13.7 ± 17.1mmHg and 3.4 ± 11.7 mmHg, respectively. Despite the differences in absolute starting values, changes over time were similar between the two systems. The concordance between the two systems was approximately 70% for classification of test results from DROPmin. CONCLUSIONS: Photo-optical sensors are promising alternatives to electro-chemical sensors for exercise oximetry, provided that miniaturization and weight reduction of the new sensors are possible. PATIENTS AND METHODS: Forty seven patients with arterial claudication ( 65 ± 7 years) performed a treadmill test with 5 probes each of the electro-chemical and photo-optical devices simul-

Participation of Arterial Ischemia in Positional-Related Symptoms among Patients Referred for Thoracic Outlet Syndrome.

Objectives: The coexistence of arterial compression with neurogenic thoracic outlet syndrome (TOS) is associated with a better post-surgical outcome. Forearm transcutaneous oxygen pressure (TcpO2) using the minimal decrease from rest of oxygen pressure (DROPmin) can provide an objective estimation of forearm ischemia in TOS. We hypothesized that a linear relationship exists between the prevalence of symptoms (PREVs) and DROPmin during 90° abduction external rotation (AER) provocative maneuvers. Thereafter, we aimed to estimate the proportion of TOS for which arterial participation is present. Methods: Starting in 2019, we simultaneously recorded forearm TcpO2 recordings (PF6000 Perimed®) and the presence/absence of ipsilateral symptoms during two consecutive 30 s AER maneuvers for all patients with suspected TOS. We retrospectively analyzed the relationship between the prevalence of symptoms and DROPmin results. We estimated the number of cases where ischemia likely played a role in the symptoms, assuming that the relationship should start from zero in the absence of ischemia and increase linearly to a plateau of 100% for the most severe ischemia. Results: We obtained 2560 TcpO2 results in 646 subjects (69% females). The correlation between PREVs and DROPmin was 0.443 (p < 0.001). From these results, we estimated the arterial participation in TOS symptoms to be 22.2% of our 1669 symptomatic upper limbs. Conclusions: TcpO2 appears to be an interesting tool to argue for an arterial role in symptoms in TOS. Arterial participation is frequent in TOS. Whether DROPmin could predict treatment outcomes better than the sole presence of compression is an interesting direction for the future.

Lower Extremity Arterial Disease and Lumbar Spinal Stenosis: A Study of Exercise-Induced Arterial Ischemia in 5197 Patients Complaining of Claudication.

Only few studies have analyzed the associations of lower extremity artery disease (LEAD) with lumbar spinal stenosis (LSS), although it is expected to be a frequent association. With exercise-oximetry, we determined the presence of exercise-induced regional blood flow impairment (ischemia) in 5197 different patients complaining of claudication and referred for treadmill testing. We recorded height, weight, age, sex, ongoing treatments, cardiovascular risk factor (diabetes, high blood pressure, current smoking habit), and history of suspected or treated LSS and/or lower limb revascularization. An ankle-brachial index at rest < 0.90 or >1.40 on at least one side was considered indicative of the presence of LEAD (ABI+). Ischemia was defined as a minimal DROP (Limb-changes minus chest-changes from rest) value < −15 mmHg during exercise oximetry. We analyzed the clinical factors associated to the presence of exercise-induced ischemia in patients without a history of LSS, using step-by-step linear regression, and defined a score from these factors. This score was then tested in patients with a history of LSS. In 4690 patients without a history of (suspected, diagnosed, or treated) LSS, we observed that ABI+, male sex, antiplatelet treatment, BMI< 26.5 kg//m2, age ≤ 64 years old, and a history of lower limb arterial revascularization, were associated to the presence of ischemia. The value of the score derived from these factors was associated with the probability of exercise-induced ischemia in the 507 patients with a history of LSS. This score may help to suspect the presence of ischemia as a factor of walking impairment in patients with a history of lumbar spinal stenosis.

Upper arm versus forearm transcutaneous oximetry during upper limb abduction in patients with suspected thoracic outlet syndrome.

Context: Thoracic outlet syndrome (TOS) is common among athletes and should be considered as being of arterial origin only if patients have "clinical symptoms due to documented symptomatic ischemia." We previously reported that upper limb ischemia can be documented with DROPm (minimal value of limb changes minus chest changes) from transcutaneous oximetry (TcpO2) in TOS. Purpose: We aimed to test the hypothesised that forearm (F-) DROPm would better detect symptoms associated with arterial compression during abduction than upper arm (U-) DROPm, and that the thresholds would differ. Methods: We studied 175 patients (retrospective analysis of a cross-sectional acquired database) with simultaneous F-TcpO2 and U-TcpO2 recordings on both upper limbs, and considered tests to be positive (CS+) when upper limb symptoms were associated with ipsilateral arterial compression on either ultrasound or angiography. We determined the threshold and diagnostic performance with a receiver operating characteristic (ROC) curve analysis and calculation of the area under the ROC curve (AUROC) for absolute resting TcpO2 and DROPm values to detect CS+. For all tests, a two-tailed p < 0.05 was considered indicative of statistical significance. Results: In the 350 upper-limbs, while resting U-TcpO2 and resting F-TcpO2 were not predictive of CS + results, the AUROCs were 0.68 ± 0.03 vs. 0.69 ± 0.03 (both p < 0.01), with the thresholds being -7.5 vs. -14.5 mmHg for the detection of CS + results for U-DROPm vs. F-DROPm respectively. Conclusion: In patients with suspected TOS, TcpO2 can be used for detecting upper limb arterial compression and/or symptoms during arm abduction, provided that different thresholds are used for U-DROPm and F-DROPm. Clinical Trial Registration: ClinicalTrials.gov, identifier NCT04376177.

A New Sleep Staging System for Type III Sleep Studies Equipped With a Tracheal Sound Sensor.

Type III sleep studies record cardio-respiratory channels only. Compared with polysomnography, which also records electrophysiological channels, they present many advantages: they are less expensive, less time-consuming, and more likely to be performed at home. However, their accuracy is limited by missing sleep information. That is why many studies present specific cardio-respiratory parameters to assess the causal effects of sleep stages upon cardiac or respiratory activities. For this paper, we gathered many parameters proposed in literature, leading to 1,111 features. The pulse oximeter, the PneaVoX sensor (recording tracheal sounds), respiratory inductance plethysmography belts, the nasal cannula and the actimeter provided the 112 worthiest ones for automatic sleep scoring. Then, a 3-step model was implemented: classification with a multi-layer perceptron, sleep transition rules corrections (from the AASM guidelines), and sequence corrections using a Viterbi hidden Markov model. The whole process was trained and tested using 300 and 100 independent recordings provided from patients suspected of having sleep breathing disorders. Results indicated that the system achieves substantial agreement with manual scoring for classifications into 2 stages (wake vs. sleep: mean Cohen's Kappa κ of 0.63 and accuracy rate Acc of 87.8%) and 3 stages (wake vs. R stage vs. NREM stage: mean κ of 0.60 and Acc of 78.5%). It indicates that the method could provide information to help specialists while diagnosing sleep. The presented model had promising results and may enhance clinical diagnosis.

Relationship Between Inflow Impairment and Skin Oxygen Availability to the Upper Limb During Standardized Arm Abduction in Patients With Suspected Thoracic Outlet Syndrome.

OBJECTIVE: Thoracic outlet syndrome (TOS) should be considered of arterial origin only if patients have clinical symptoms that are the result of documented symptomatic ischemia. Simultaneous recording of inflow impairment and forearm ischemia in patients with suspected TOS has never been reported to date. We hypothesized that ischemia would occur in cases of severely impaired inflow, resulting in a non-linear relationship between changes in pulse amplitude (PA) and the estimation of ischemia during provocative attitudinal upper limb positioning. DESIGN: Prospective single center interventional study. MATERIAL: Fifty-five patients with suspected thoracic outlet syndrome. METHODS: We measured the minimal decrease from rest of transcutaneous oximetry pressure (DROPm) as an estimation of oxygen deficit and arterial pulse photo-plethysmography to measure pulse amplitude changes from rest (PA-change) on both arms during the candlestick phase of a "Ca + Pra" maneuver. "Ca + Pra" is a modified Roos test allowing the estimation of maximal PA-change during the "Pra" phase. We compared the DROPm values between deciles of PA-changes with ANOVA. We then analyzed the relationship between mean PA-change and mean DROPm of each decile with linear and second-degree polynomial (non-linear) models. Results are reported as median [25/75 centiles]. Statistical significance was p < 0.05. RESULTS: DROPm values ranged -11.5 [-22.9/-7.2] and - 12.3 [-23.3/-7.4] mmHg and PA-change ranged 36.4 [4.6/63.8]% and 38.4 [-2.0/62.1]% in the right and left forearms, respectively. The coefficient of determination between median DROPm and median PA-change was r 2 = 0.922 with a second-degree polynomial fitting, but only r 2 = 0.847 with a linear approach. CONCLUSION: Oxygen availability was decreased in cases of severe but not moderate attitudinal inflow impairments. Undertaking simultaneous A-PPG and forearm oximetry during the "Ca + Pra" maneuver is an interesting approach for providing objective proof of ischemia in patients with symptoms of TOS suspected of arterial origin.

Thoracic Outlet Syndrome: Fingertip Cannot Replace Forearm Photoplethysmography in the Evaluation of Positional Venous Outflow Impairments.

Objective: Fingertip photoplethysmography (PPG) resulting from high-pass filtered raw PPG signal is often used to record arterial pulse changes in patients with suspected thoracic outlet syndrome (TOS). Results from venous (low-pass filtered raw signal) forearm PPG (V-PPG) during the Candlestick-Prayer (Ca + Pra) maneuver were recently classified into four different patterns in patients with suspected TOS, two of which are suggestive of the presence of outflow impairment. We aimed to test the effect of probe position (fingertip vs. forearm) and of red (R) vs. infrared (IR) light wavelength on V-PPG classification and compared pattern classifications with the results of ultrasound (US). Methods: In patients with suspected TOS, we routinely performed US imaging (US + being the presence of a positional compression) and Ca + Pra tests with forearm V-PPG IR . We recruited patients for a Ca + Pra maneuver with the simultaneous fingertip and forearm V-PPG R . The correlation of each V-PPG recording to each of the published pattern profiles was calculated. Each record was classified according to the patterns for which the coefficient of correlation was the highest. Cohen's kappa test was used to determine the reliability of classification among forearm V-PPG IR , fingertip V-PPG R , and forearm V-PPG R . Results: We obtained 40 measurements from 20 patients (40.2 ± 11.3 years old, 11 males). We found 13 limbs with US + results, while V-PPG suggested the presence of venous outflow impairment in 27 and 20 limbs with forearm V-PPG IR and forearm V-PPG R , respectively. Fingertip V-PPG R provided no patterns suggesting outflow impairment. Conclusion: We found more V-PPG patterns suggesting venous outflow impairment than US + results. Probe position is essential if aiming to perform upper-limb V-PPG during the Ca + Pra maneuver in patients with suspected TOS. V-PPG during the Ca + Pra maneuver is of low cost and easy and provides reliable, recordable, and objective evidence of forearm swelling. It should be performed on the forearm (close to the elbow) with either PPG R or PPG IR but not at the fingertip level.

Investigation of arterial claudication with transcutaneous oxygen pressure at exercise: Interests and limits.

Transcutaneous oxygen pressure (TcpO2) measurement has been used for years at rest in patients with lower extremity artery disease. It was proposed for exercise testing (Ex-TcpO2) in the 80ies to evaluate regional blood flow impairment (RBFI) at the proximal and distal levels simultaneously and on both sides, in case of claudication. It was suggested that the use of a chest electrode was mandatory to show that decreases in TcpO2 at the limb level result from limb RBFI and not from a systemic pO2 decrease of cardiopulmonary origin (exercise-induced hypoxemia). Unfortunately, a major pitfall of Ex-TcpO2 was the low absolute reliability of the regional perfusion index (RPI: ratio of limb to chest values) and the technique was almost abandoned until 2003, when the DROP index (Decrease from rest of oxygen pressure: limb changes minus chest changes from rest) was proposed. The DROP mathematical formula makes Tcpo2 results independent from the absolute pO2 starting values, improving reliability of Ex-TcpO2 as compared to the RPI. Since then, Ex-TcpO2 has been of renewed interest. The present paper addresses the physiology of Ex-TcpO2, interpretation of its results, and common misunderstandings about its use.

Forearm Volume Changes Estimated by Photo-Plethysmography During an Original Candlestick/Prayer Maneuver in Patients With Suspected Thoracic Outlet Syndrome.

Objective: Hemodynamic investigations in thoracic outlet syndrome (TOS) remain difficult, even in trained hands. Results are generally reported as either presence or absence of venous compression. In fact, in patients with suspected TOS but without chronic venous occlusion, the forearm volume changes may result from various combinations of forearm position from heart level, arterial inflow, and/or venous outflow positional impairment. Design: Cross sectional, retrospective, single center study, accessible on Clinicaltrial.gov under reference NCT04376177. Material: We used venous photo-plethysmography (V-PPG) in 151 patients with suspected TOS. The subjects elevated their arms to the "candlestick" (Ca) position for 30 s and then kept their arm elevated in front of the body for an additional 15 s ("prayer" position; Pra). This CA-Pra procedure was repeated three times by each patient with recording of both arms. Method: We classified V-PPG recordings using an automatic clustering method. Result: The blinded clustering classification of 893 V-PPG recordings (13 missing files) resulted in four out of seven clusters, allowing the classification of more than 99% of the available recordings. Each cluster included 65.73, 6.16, 17.13, and 10.8% of the recordings, respectively. Conclusion: Venous hemodynamic profiles in TOS are not only either normal or abnormal. With V-PPG, four clusters were observed to be consistent with, and assumed to result from, the four possible associations of presence/absence of arterial inflow/venous outflow positional impairment: (1) normal response (maximal emptying in Ca and Pra), (2) isolated inflow impairment (emptying in Ca and filling in Pra due to post-ischemic vasodilation), (3) isolated venous outflow impairment (emptying then filling in Ca due to arterial inflow and emptying in Pra), and (4) simultaneous inflow/outflow impairment (emptying in Ca but no filling due to concomitant inflow impairment and further emptying in Pra).