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

Abstract

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).

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

“…As a routine during each visit, we recorded patient demographics and conditions, including age, sex, weight, height, history of the chest, shoulder or arm trauma or surgery, professional activity, and any ongoing treatments. All patients had bilateral forearm V-PPG IR recording (2–3 cm distal to the elbow crease) with Vasolab320 (ELCAT ® , Germany), as previously described ( Hersant et al, 2021 ). In brief, it is stated that the Ca + Pra maneuver was performed with four consecutive phases: arm elevation to the candlestick position (in <5 s), maintenance of the “candlestick” (Ca) position until 30 s, rapid change to the “prayer” (Pra) position, which is maintained for 15 s, and then arm lowering ( Hersant et al, 2021 ).…”

“…All patients had bilateral forearm V-PPG IR recording (2–3 cm distal to the elbow crease) with Vasolab320 (ELCAT ® , Germany), as previously described ( Hersant et al, 2021 ). In brief, it is stated that the Ca + Pra maneuver was performed with four consecutive phases: arm elevation to the candlestick position (in <5 s), maintenance of the “candlestick” (Ca) position until 30 s, rapid change to the “prayer” (Pra) position, which is maintained for 15 s, and then arm lowering ( Hersant et al, 2021 ). For routine PPG IR , after one training session, we waited for at least 1 min at rest with the arms along the torso before commencing recording ( Hersant et al, 2021 ).…”

“…In brief, it is stated that the Ca + Pra maneuver was performed with four consecutive phases: arm elevation to the candlestick position (in <5 s), maintenance of the “candlestick” (Ca) position until 30 s, rapid change to the “prayer” (Pra) position, which is maintained for 15 s, and then arm lowering ( Hersant et al, 2021 ). For routine PPG IR , after one training session, we waited for at least 1 min at rest with the arms along the torso before commencing recording ( Hersant et al, 2021 ). It should be noted that ELCAT ® starts from zero and records V-PPG IR values in arbitrary units (AUs) at a sample rate of 4 Hz for 60 s and then automatically stops.…”

“…We calculated the coefficient of correlation of each recording to the reference curve of each of the four previously published representative patterns ( Hersant et al, 2021 ). The reference curve was the mean of all recordings included in the cluster.…”

“…It must be kept in mind that PPG is a semiquantitative technique with absolute values or absolute changes, being highly variable in test–retest recordings. We recently reported our experience with low-pass filtered reflectance infrared light forearm PPG (V-PPG IR ) during the Candlestick-Prayer (Ca + Pra) maneuver ( Hersant et al, 2021 ). Our specific interest in the prayer position is because it can completely empty elevated upper limbs by opening the costoclavicular angle and thus might confirm whether venous outflow was impaired during the candlestick position.…”