Human survival depends on the exchange of fresh air with carbon dioxide in the blood. Since this exchange takes place in the alveoli, one of the first concepts taught in respiratory physiology is that the size of each breath, the tidal volume, must exceed the volume of the conducting airways, also known as the dead space. However, this construct is not strictly accurate, since we know that adequate gas exchange can be achieved when tidal volumes smaller than that of the dead space are taken in at sufficiently high frequencies, a technique termed high-frequency ventilation.How can we survive if . . .