Respiratory Patterns In Individuals With Moderate-to-Severe Traumatic Brain Injury (msTBI) During Cycling

While damage to the central nervous system following an acute msTBI often results in abnormal breathing patterns, chronic effects are poorly understood particularly when the respiratory system is under stress such as during maximal exercise. PURPOSE: To compare brainstem diameters and exercise ventilation between participants with and without chronic msTBI. We hypothesized that individuals with prior history of msTBI will exhibit brainstem atrophy and greater ventilation irregularity. METHODS: 14 participants were included: 8 msTBI (44 ± 13 years, 75% male), 6 controls (35 ± 11 years; 50% male). Case status was determined by the Glasgow Coma Scale (≤13) and medical records. Breath-by-breath ventilatory parameters (RF, VT, VE, Ti, Te, Ttot, and Ti/Ttot) were obtained during a maximal cardiopulmonary exercise test (CPET), and an anatomical MRI scan was obtained (3.0 T Siemens Skyra scanner). Midbrain, pons and medulla diameters were measured manually using the midsagittal T1-weighted image. Average breathing times and sample entropy were calculated for ventilatory parameters at low/moderate intensity (< 60% peak VO2), moderate/high intensity (≥ 60% peak VO2), and total exercise. Adjusted linear models assessed group differences and the relationship between brainstem size, entropy, and breathing parameters. RESULTS: All measured brainstem areas were significantly smaller for msTBI (p < 0.05). Neither average Ti, Te, Ttot, and Ti/Ttot nor RF, VT, and VE sample entropy were significantly different between groups. However, participants with msTBI had longer Ti, Te and Ttot and lower RF, VT, and VE entropy at all intensities, with corresponding small to moderate effect sizes (d > 0.3). There was a significant positive association between medulla diameter and both RF (β = 3.7, p = 0.05) and VE (β = 5.0, p = 0.01) entropy at moderate/high intensity. CONCLUSIONS: In this pilot study, we found brainstem diameters were reduced in those with msTBI and those with larger medulla diameters may be able to modulate exercise ventilation more efficiently. Our results warrant confirmation in a larger sample. Supported by: NJBCBIR- CBIR23IRG006