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In the well-known Berlin definition of acute respiratory distress syndrome (ARDS), there is a recommended adjustment for arterial oxygen partial pressure to fractional inspired oxygen (PaO₂/FIO₂) at altitude, but without a reference as to how it was derived. At the same shunt, PaO₂/FIO₂ decreases with altitude, impairing a proper comparison of individuals with similar lung damage if they reside at different altitudes and if the shunt is not directly measured, as is the case in most patients. It is then very important in multicenter studies to correct the PaO₂/FIO₂ by altitude or barometric pressure (i.e. raise the value of PaO₂/FIO₂ obtained at altitude), but unfortunately, the adjustment is not a simple function of altitude or barometric pressure. The correction suggested by the working group does the opposite of what is needed because it requests a multiplication by a fraction: barometric pressure (Pbar)/760. If, instead of multiplying by Pbar/760, we divide by the ratio (to set, for example, varying limits for ARDS severity at different altitudes), the resulting PaO₂/FIO₂ is closer to that expected at sea level for lower shunts (and high PaO₂/FIO₂), but overcorrects at higher shunts and of course does not take into account changes in PaO₂/FIO₂ due to modifications of FIO₂. Our aim was to develop an equation able to take into account the impact of altitude on PaO₂/FIO₂ so that patients from different altitudes could be compared at a more homogeneous degree of lung damage.

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2016-09-13   |   459 visitas   |   Evalua este artículo 0 valoraciones

Vol. 68 Núm.4. Julio-Agosto 2016 Pags. 169-170 Rev Invest Clin 2016; 68(4)