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Evaluation of pulse oximetry as a surrogate for PaO 2 in awake dogs breathing room air and anesthetized dogs on mechanical ventilation
Author(s) -
Farrell Kate S.,
Hopper Kate,
Cagle Laura A.,
Epstein Steven E.
Publication year - 2019
Publication title -
journal of veterinary emergency and critical care
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.886
H-Index - 47
eISSN - 1476-4431
pISSN - 1479-3261
DOI - 10.1111/vec.12898
Subject(s) - medicine , pulse oximetry , hypoxemia , oxygen–haemoglobin dissociation curve , arterial blood , anesthesia , mechanical ventilation , receiver operating characteristic , cutoff , oxygen saturation , room air distribution , ventilation (architecture) , nuclear medicine , oxygen , hemoglobin , mechanical engineering , chemistry , physics , organic chemistry , quantum mechanics , engineering , thermodynamics
Objective To evaluate the ability of arterial hemoglobin oxygen saturation measurement via pulse oximetry (SpO 2 ) to serve as a surrogate for PaO 2 in dogs. Design Two‐part study: prospective observational and retrospective components. Setting University teaching hospital. Animals Ninety‐two dogs breathing room air prospectively enrolled on a convenience basis. Retrospective evaluation of 1,033 paired SpO 2 and PaO 2 measurements from 62 dogs on mechanical ventilation. Interventions Dogs with concurrent SpO 2 and PaO 2 measured on room air had a data sheet completed with blood gas analysis. SpO 2 , PaO 2 , and FiO 2 values were collected from medical records of dogs on mechanical ventilation. Measurements and Main Results Predicted PaO 2 was calculated from SpO 2 using the dog oxyhemoglobin dissociation curve. The correlation coefficient between measured and predicted PaO 2 was 0.49 ( P < 0.0001) in room air dogs and 0.74 ( P < 0.0001) in ventilated dogs. In room air dogs, Bland–Altman analysis between measured minus predicted PaO 2 versus the average showed a mean bias of −6.0 mm Hg (95% limit of agreement, −35 to 23 mm Hg). The correlation coefficient between PaO 2 /FiO 2 and SpO 2 /FiO 2 ratios was 0.76 ( P < 0.0001). After combining data sets, receiver operating characteristic curve analysis showed the optimal cutoff value for detecting hypoxemia (PaO 2 < 80 mm Hg) was an SpO 2 of 95%, with sensitivity and specificity of 77.8% and 89.5%, respectively. Using this cutoff, 6.9% of SpO 2 readings failed to detect hypoxemia, whereas 7.2% predicted hypoxemia that was not present. Conclusions The SpO 2 was not clinically suitable as a surrogate for PaO 2 , though it performed better in mechanically ventilated dogs. As sensitivity for the detection of hypoxemia was poor, pulse oximetry does not appear to be an acceptable screening test. The SpO 2 /FiO 2 ratio may have value for evaluation of anesthetized dogs on supplemental oxygen. Arterial blood gas analysis remains ideal for assessment of oxygenation.