Montes OSMA, Xóchitl PMA,Olvera GCI, Franco GJ

Language: Spanish
References: 18
Page: 8-12
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ABSTRACT

Hypoxemia is frequent in critically ill patients. It can be produced by hypoventilation, ventilation/perfusion mismatch, right to left shunts, or abnormalities of the diffusion within the capillary-alveoli membrane. It can be produced too as a result of low inspiratory pressures, as in high altitudes. Hypoxemia is one of the key points in the definitions of Acute Respiratory Distress Syndrome (ARDS) and Acute Lung Injury (ALI). PaO₂/FiO₂ (P/F) relation is included in the American-European definition for ARDS (if less than 200) and ALI, if less than 300. Hypobaric hypoxia is a phenomenon that exists, and that has not been considered for the definition of ALI/ARDS. When barometric pressure (PB) diminishes as a consequence of lower atmospheric pressure (P atm), oxygen partial pressure (PO₂) diminishes too. A useful way to determine the P/F, related to barometric pressure is: adjusted PB: PAO₂x PaO₂/FiO₂/100; a similar formula to that, published by West JB and used in the Alveoli study: Adjusted P/F= P/F x (PB /760). P/F relation has to be adjusted according to the barometric pressure.

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