In this VETgirl podcast, Dr. Lisa Powell, DACVECC reviews a pilot study out of Animal Medical Center that evaluates whether the ratio of pulse oximetry saturation/fraction of inspired oxygen (SpO2 /FiO2 or [SF]) correlates with the ratio of partial pressure of oxygen in arterial blood/FiO2 (PaO2 /FiO2 or [PF]) in dogs. Traditionally, the PF is used to evaluate the severity of acute lung injury (ALI, < 300) or acute respiratory distress syndrome (ARDS, < 200). But can we use our pulse oximetry as a non-invasive way of obtaining assessment? This study found that in dogs spontaneously breathing room air, the SF and PF radio had good correlation. This suggests that you can use your pulse oximeter instead, which is helpful especially in cats and small dogs (where it may be harder to obtain an arterial blood gas sample). Further studies are warranted however, to validate this relationship and to assess the ability of SF to predict outcome in critically ill, hypoxemic patients. References: 1. Calabro JM, Prittie JE, Palma DA. Preliminary evaluation of the utility of comparing SpO2/FiO2 and PaO2/FiO2 ratios in dogs. J Vet Emerg Crit Care 2013;23(3):280-285.