Effects of acute intermittent hypoxia on hand use after spinal cord trauma A preliminary study

Objective: To test the hypothesis that daily acute intermittent hypoxia (AIH) combined with hand opening practice improves hand dexterity, function, and maximum hand opening in persons with chronic, motor-incomplete, cervical spinal cord injury. Methods: Six participants completed the double-blind, crossover study. Participants received daily (5 consecutive days) AIH (15 episodes per day: 1.5 minutes of fraction of inspired oxygen [FIO2] = 0.09, 1-minute normoxic intervals) followed by 20 repetitions of hand opening practice and normoxia (sham, FIO2 5 0.21) + hand opening practice. Hand dexterity and function were quantified with Box and Block and Jebsen-Taylor hand function tests. We also recorded maximum hand opening using motion analyses and coactivity of extensor digitorum and flexor digitorum superficialis muscles using surface EMG. Results: Daily AIH + hand opening practice improved hand dexterity, function, and maximum hand opening in all participants. AIH + hand opening practice improved Box and Block Test scores vs baseline in 5 participants (p = 0.057) and vs sham + hand opening practice in all 6 participants (p = 0.016). All participants reduced Jebsen-Taylor Hand Function Test (JTHF) time after daily AIH + hand opening practice (27.2 +/- 1.4 seconds) vs baseline; 4 of 6 reduced JTHF time vs sham + hand opening practice (p=0.078). AIH+hand opening practice improved maximumhand aperture in 5 of 6 participants (8.1 +/- 2.7 mm) vs baseline (p = 0.018) and sham + hand opening practice (p = 0.030). In 5 participants, daily AIH-induced changes in hand opening were accompanied by improved EMG coactivity (p = 0.029). Conclusions: This report suggests the need for further study of AIH as a plasticity "primer" for task-specific training in spinal cord injury rehabilitation. Important clinical questions remain concerning optimal AIH dosage, patient screening, safety, and effect persistence.