High-Frequency Oscillatory Ventilation on Shaky Ground

We thought it was impossible. Physiological principles maintained that ventilation at tidal volumes less than the anatomical deadspace should be ineffective (i.e., inspired air not reaching the alveolae). Data from a 1980 study dispelled that myth, showing unequivocally that ventilation with tidal volumes as small as 20 to 30 ml in dogs, a mere fraction of the anatomical deadspace, could maintain adequate ventilation.1 These unexplained observations sparked transport and mixing theories predicting that CO2 removal should vary in direct proportion to breathing frequency (although the relationship with tidal volume is more complex2,3), and these predictions were later . . .