Chest Wall Kinematics and Respiratory Muscle Action During Supine Breathing in Individuals With and Without Spinal Cord Injury (SCI)

Main Outcome Measures: The volume changes of chest wall and respiratory electromyographic ( EMG ) muscle activity were measured simultaneously by OEP and surface EMG. The variables included volume changes (ΔV ), ratio of volume changes (ΔVr ), peak velocity of volume changes ( PV ), the percentage of peak velocity occurs ( PPV ) in three compartments (upper thorax, UT; lower thorax, LT; and abdominal compartment, AB), and Root Mean Square EMG ( RMS EMG ) of sternocleidomastoid and diaphragm (combined with intercostalmuscles).

Results: Ttetraplegic individuals had smallerΔVUT andΔVLT than those of control subjects(P< .006 and .006, respectively). Furthermore, the ΔVr of AB was greater than those of UT and LT( P< .006, .006, respectively), PVAB was smaller than PVLT ( P< .006), PPVUT was greater than PPVLT and PPVAB ( P< .008, .008, respectively ). The paraplegic subjects had smallerΔVLT than that of control subjects ( P< .006 ). ΔVr of UT was greater than that of LT, and both PVUT and PVAB were greater than PVLT ( P< .006 and .006, respectively). However, the paraplegic subjects preferred to all three compartments to achieve the maximal inspiration, like control group. In control group, onlyΔVAB was comparable with other compartments. ΔVr of UT was greater than LT, and PVUT was greater than PVLT and PVAB ( P<.006 and .006, respectively). For the RMS EMG, it demonstrated that average RMS EMG of two muscles in both tetraplegic and paraplegic group were greater than that in control group (P< .017 and .017, respectively).

Conclusion: The results applied the three-compartment model of chest wall to investigate the breathing pattern by OEP in individuals with and without SCI during inspiration of vital capacity breathing in supine posture. There were some interesting findings that (1) the tetraplegic subjects used AB contributed most volume changes, they can expand the AB more easily, and the UT took the responsibility to performed the final adjust during the inspiration; (2) the paraplegic subjects used UT contributed the most volume changes, they expanded the both UT and AB more easily, and all three compartment moved together during the inspiration; (3) the control subjects used UT to increase the most volume changes, they can expand UT more than the others, and all three compartments moved together during the inspiration phase, (4) the results of RMS EMG showed that the central neural drive in both tetraplegic and paraplegic subjects were greater than control group.