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  • Author or Editor: Valentina De Monte x
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Objective—To evaluate the use of the oxygen content–based index, Fshunt, as an indicator of venous admixture (s/t) at various fractions of inspired oxygen (Fio 2s) in anesthetized sheep undergoing Flung or 2-lung ventilation.

Animals—6 healthy adult female sheep.

Procedures—Sheep were anesthetized and administered 5 different Fio 2s (0.21, 0.40, 0.60, 0.80, and 1.00) in random order during 2-lung mechanical ventilation. Arterial and mixed venous blood samples were obtained at each Fio 2 after a 15-minute stabilization period. Vital capacity alveolar recruitment maneuvers were performed after blood collection. The previously used Fio 2 sequence was reversed for sample collection during Flung ventilation. Blood samples were analyzed for arterial, pulmonary end-capillary, and mixed venous oxygen content and partial pressure and for hemoglobin concentration. Oxygen hemoglobin saturation, s/t, Fshunt, and oxygen tension–based indices (OTIs; including Pao 2:Fio 2, alveolar-arterial difference in partial pressure of oxygen [Pao 2 – Pao 2], [Pao 2 – Pao 2]:Fio 2, [Pao 2 – Pao 2]:Pao 2, and Pao 2:Pao 2) were calculated at each Fio 2; associations were evaluated with linear regression analysis, concordance, and correlation tests. Intermethod agreement between s/t and Fshunt was tested via Bland-Altman analysis.

Results—Strong and significant associations and substantial agreement were detected between Fshunt and s/t. Relationships between OTIs and s/t varied, but overall correlations were weak.

Conclusions and Clinical Relevance—Whereas OTIs were generally poor indicators of s/t, Fshunt was a good indicator of s/t at various Fio 2s, regardless of the magnitude of s/t, and could be potentially used as a surrogate for s/t measurements in healthy sheep.

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in American Journal of Veterinary Research