Reproducibility of Partial Pressure of Oxygen and Oxygen Depletion Rate in Animal Model

HP MRI measures of regional oxygen tensions provide important insight into a lung’s physiologic state during normal and diseased conditions. This stems from a unique
correlation between the lung’s regional steady state oxygen concentrations and its local
ventilation perfusion ratios. A similar relationship exits between the lung’s local oxygen
depletion rates and its regional alveolar perfusion rates and therefore, makes these measures of great interest to pulmonologists, chest radiologist, and lung physiologist. Despite general interest in these measurements, these techniques are rarely used clinically. A major reason for this is the lack of careful validation and reproducibility studies. In this research, we present, to the best of our knowledge, the first HP ³He MRI oxygen and ventilation perfusion ratio reproducibility study. Since cardiopulmonary systems are dynamic, special efforts were made to maintain the test animals under homeostatic conditions during the measurement process. This minimized scatter in the measurement data due to physiologic variability; furthermore, a highly accurate computer controlled MRI compatible ventilator was constructed to ensure that gas delivery was performed in a precise and reproducible fashion.

Table of PO₂, V/Q , and ODR as a function or measurement number for rabbit number 5. Standard deviations shown as well. Measurement 5 was taken immediately after the HP helium reservoir was changed and may represent an outlying point due to improper mixing of gas during the measurement process.