Doc 1: There’s a big swing on their A-line, shall I give more fluids?

Doc 2: Well given that they’re spontaneously breathing, there’s no real evidence to support PPV here 🤷‍♂️

- A recently overheard conversation, prompting this 🧵 on PPV in the spontaneously breathing patient. The ∆ between systolic & diastolic pressures is the pulse pressure (PP) & it is determined by the compliance of the aorta and the ventricular stroke volume (SV).

Whilst aortic compliance reduces with age, beat-to-beat changes in PP occur predominately due to changes in SV.