Disclosures: Stella A. Barth, BA: No financial relationships or conflicts of interest

Objective: The aim of this study was to quantify the integrity of double-blinding in a clinical trial studying the physiological effects of breathing mild bouts of low-oxygen in ten able-bodied adults. Past studies showed that therapeutic intermittent hypoxia (TIH) triggers rapid mechanisms of spinal plasticity and enhances walking function in persons with incomplete spinal cord injury. A general concern is that, despite the double-blinding protocols in previous TIH research, these studies did not record the extent to which subjects or assessors may detect when they are receiving TIH or Placebo. Here, we address this possible confound.

Design: Double-blind, randomized, placebo-controlled, cross-overSetting : Research LabParticipants : 10 healthy, able-bodied individuals participated in 2 sessions of a randomized, balanced, cross-over, placebo-controlled TIH protocol. 5 subjects received TIH for the first session, and 5 subjects received Placebo for the first session. The second session took place at least 2 weeks after the first session for each subject.

Interventions: A TIH session consisted of a single sequence of 15, 90-second episodes of breathing low oxygen (FiO2=0.10) with 60-second room air intervals. A Placebo session consisted of a single sequence of 15, 90-second episodes of breathing room air (FiO2=0.21) with 60-second room air intervals.

Main Outcome Measures: Subjects’ guess accuracy of treatment assignment for each session, sensitivity, and specificity; blood pressure (BP), heart rate (HR), blood oxygen saturation (SpO2)

Results: 3 out of 10 subjects correctly identified a true TIH session (sensitivity = 0.30). 4 out of 10 subjects correctly identified a true Placebo session (specificity = 0.40). Calculated accuracy of guessing treatment assignment was worse than random chance (0.5 expected vs. 0.35 observed).Conclusions: A majority of subjects could not differentiate between treatment types despite experiencing significant decreases in SPO2 and increases in heart rate during TIH. Further study will reveal whether treatment type can be blinded from assessors and neurologically impaired subjects.

Level of Evidence: Level I

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/blinding-integrity-analysis-of-a-randomized-clinical-trial-to-test-the-effects-of-therapeutic-intermittent-hypoxia-in-able-bodied-adults/