Pulmonary physiology – P/F ratio defining your patient’s pulmonary status

 

PaO2 / FiO2 = P/F ratio.

This simple calculation helps define your patient’s lung status :

P/F ratio                                    pulmonary status

.>600                                              normal

.<300                                               ALI (acute lung injury)

.<200                                                ARDS

.<150                                                AHRF (acute hypoxemic respiratory failure)