Repetitive Intermittent Hypoxia Improves Hand Function in Humans with Incomplete Spinal Cord Injury Open Access

Botezat, Jen (2013)

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Spinal cord injury severs connections between the brain and spinal cord, radically impairing mobility below the level of injury. One promising strategy to increase mobility following SCI is by episodic exposures to low oxygen (repetitive acute intermittent hypoxia (rAIH)). In persons with chronic, incomplete spinal cord injury (iSCI), rAIH breathing increases lower limb muscle activation and overground walking ability. Yet whether comparable rAIH-induced recovery of hand function occurs in persons with cervical injuries remains unknown.

A randomized, double-blind, crossover design was used to test the hypothesis that rAIH (fifteen 90-second low oxygen episodes per day, 1 minute intervals; 5 consecutive days) improves hand function in persons with chronic, cervical iSCI. Six SCI subjects (6 men, 44±11 years old) received rAIH breathing. Hand function was assessed at baseline, after the first and fifth intervention days, and at follow-up (within a week from end of intervention). Primary outcomes were hand dexterity, strength, speed, and maximal opening. Using electromyograms, we also assessed magnitude of muscle activity in two hand flexors and two extensors, as well as level of co-activity between these muscles, during hand opening. Results were compared with those obtained when subjects received a sham intervention (fifteen 90-second normoxia episodes, 1 minute intervals; 5 consecutive days).

We found rAIH safe and effective at improving hand function in persons with chronic iSCI. At rAIH follow-up, participants exhibited increased manual dexterity (p=0.001), pinch strength (p=0.04), and dominant hand speed (p=0.01), as compared to sham. Although maximal hand opening remained similar to baseline at follow-up, finger extensor activity approached significance (p=0.05) in rAIH versus sham. The ratio of flexor and extensor activity indicated increased extensor contribution to hand opening (p<0.001) after rAIH, a strategy more reminiscent of able-bodied muscle activation. Grip strength and non-dominant hand speed did not increase significantly at rAIH follow-up over sham. Sham did not elicit changes relative to baseline in any outcome measure. We conclude that rAIH may be a useful adjuvant to current rehabilitation therapies for people with longstanding hand impairments due to chronic, cervical iSCI.

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Figures and Tables...18

Figure 1. Consort Diagram

Table 1. Subject Demographics

Figure 2. Experimental setup

Table 2. Safety monitoring summary

Figure 3. rAIH breathing and testing protocol

Figure 4. Clinical outcome measures

Table 3. Clinical outcome measure descriptions

Figure 5. Box and Blocks Test outcomes

Figure 6. Pinch strength outcomes

Figure 7. Grip strength outcomes

Figure 8. Jebsen Taylor Hand Function Test outcomes

Figure 9. Maximal Aperture outcomes

Figure 10. Flexor and extensor activity magnitude

Figure 11. Flexor and extensor co-activity outcomes

Table 4. Clinical significance summary



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