Association between aging and in vivo mitochondrial oxygen tension and oxygen consumption in healthy volunteers

The Cellular Oxygen METabolism (COMET) device provides validated bedside in vivo measurements of mitochondrial oxygen tension (mitoPO₂) and consumption (mitoV̇o₂). Since mitochondrial function has been shown in experimental in vivo and ex vivo studies to potentially alter with age, it is important to establish whether age itself influences these in vivo measurements. The aim of this single-center prospective observational study was to determine whether mitoPo₂ and mitoV̇o₂ values are influenced by age, thereby ensuring their validity for use across age groups. The aim of the study was not to evaluate COMET as monitor of aging. Using the COMET device, mitoPo₂ and mitoV̇o₂ were measured at the upper arm and sternum in 176 healthy participants aged 18-90 yr. The mean arm mitoPo₂ was 75.3 ± 28.7 mmHg (means ± SD), whereas the mean sternal mitoPo₂ was 65.8 ± 23.6 mmHg. Multivariable linear regression did not demonstrate a significant age-related change in mitoPo₂. Conversely, the mean arm mitoV̇o₂ was 6.37 ± 2.07 mmHg·s^-1 and the median sternal mitoV̇o₂ was 7.16 mmHg·s^-1 [interquartile range (IQR) 5.63-9.17]. Multivariable linear models at both sites demonstrated a significant negative association between age and mitoV̇o₂. No significant sex differences were observed for either parameter. These findings reveal that although mitoPo₂ remains unaffected by age, mitoV̇o₂ shows a significant negative association with increasing age. This distinction suggests that mitoPo₂ can be interpreted independent of age, whereas mitoV̇o₂ requires age-informed consideration. By profiling healthy volunteers across four decades, we establish preliminary age-informed normative ranges for epidermal mitoPo₂ and mitoV̇o₂.<b>NEW & NOTEWORTHY</b> This study measured in vivo mitochondrial oxygen tension (mitoPo₂) and consumption (mitoV̇o₂). mitoPo₂ remained constant across ages, this stability of mitoPO₂ suggests consistent mitochondrial oxygen availability, eliminating the need for age-based adjustments in ongoing research using a low mitoPO₂ threshold to predict adverse events such as cardiac surgery associated acute kidney injury. However, mitoV̇o₂ significantly decreased with age, showing that age must be taken into account when interpreting mitoV̇o₂ values and when defining reference ranges.