A pilot study of forearm microvascular impairment and pain while using a telephone.

OBJECTIVE: To determine if using a telephone can induce forearm pain and ischemia. DESIGN: Prospective case-control trial. SETTING: Vascular laboratory in the university hospital in Angers between September 2018 and March 2019. PARTICIPANTS: Fifteen apparently healthy subjects (controls) and 32 patients with suspected thoracic outlet syndrome (TOS) of vascular or non-vascular origin. INTERVENTION: Hand-holding a cellular phone to answer a call from investigators. MAIN OUTCOME MEASURES: Presence of forearm fatigue or pain (primary outcome), ability to hold the phone with each hand for 1 min (secondary outcome 1) and decrease in forearm transcutaneous oxygen pressure DROP index indicating forearm ischemia (secondary outcome 2). A DROP < -15 mm Hg defined ischemia. RESULTS: Answering a phone call resulted in 25(78%) patients with forearm fatigue or pain and in 18 (56%) cases in the inability to hold the phone for 1 min, on one or both arms in patients with suspected TOS, but never occurred in healthy volunteers (p < .05 and p < .001). The presence of ischemia was observed in one or both arms in 10 (31%) patients with proved TOS and was always associated to phone-induced pain. Three (20%) of the controls had phone-induced ischemia. All had asymptomatic TOS and remained asymptomatic during the phone test (p = .42 from suspected-TOS patients). CONCLUSION: The phone conversation resulted in pain in many patients with suspected TOS. Transcutaneous oximetry can document the underlying ischemia. Forearm phone-call-induced pain may be indicative of TOS provided that no earplug or headset is used. Trial registrationClinicalTrials.govNCT03355274.