Methodological considerations for near-infrared spectroscopy to assess mitochondrial capacity after spinal cord injury

Mitochondrial capacity is determined by the maximal affinity of utilizing oxygen and can be used as a surrogate to assess the overall health in different clinical populations. Mitochondrial disfunction can decrease energy production, increase reactive oxygen species released, alter cellular redox status, or even promote cellular apoptosis. A noninvasive, cost-effective, and relatively simple in vivo technique to assess mitochondrial capacity utilizes near-infrared spectroscopy (NIRS) combined with a series of arterial occlusions. NIRS technology relies on wavelength-dependent absorption of near-infrared light by hemoglobin and myoglobin molecules as it propagates through different tissues to measure tissue oxygenation. The purpose of the current work is to highlight and expand on these limitations and provide some considerations that may enhance applications of NIRS in assessing skeletal muscle mitochondrial capacity after SCI.

• 1
  Only four participants produced data with accepted rate constants of 0.002–0.013 s−1 and r2 of 0.71–0.87.
• 2
  Applications of studentized residuals ≥2.5 resulted in sparing data from another four participants with rate constants of 0.010–0.018 s−1and r2 values ranging from 0.86–0.99.
• 3
  Several limitations may challenge the use of NIRS to assess mitochondrial capacity after SCI. Acknowledging these limitations and applying additional data processing techniques may overcome the discussed limitations and facilitate data sparing.