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Comment by sigmaprimus | Hacker News Reader

CPAP stands for continuous positive airway pressure, one of the problem with SARS(Severe acute respitory syndrom) or Wuhan Fever is it stiffens the lungs making it hard to exhale. This in turn allows the lungs to fill up with fluid, a sort of viral pneumonia.

I believe a ventilator uses a negative pressure or vacuum to assist with exhalation and air exchange.

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Actually exhalation is passive, not active, in modern day ICU ventilation.

Interesting. How does that work? Does the pressure drop to let air out or something?

To keep it simple you have a device that increases pressure through a closed circuit to push air into the lungs, when its time to exhale it drops pressure (although is still positive pressure i.e PEEP) that is weaker than the natural recoil/elasticity of the chest wall combined with gravity in a supine patient and allows exhalation.

Agree. I'd add that my comment above about exhalation being passive is true in adult ICU practice. In high frequency oscillatory ventilation (HFOV) exhalation is active (a piston actively creates a negative pressure in the breathing circuit). I understand this is still used quite a bit in neonates (though I don't do NICU, so not an expert) but has gone out of favour in adults in a big way due to the results of trials like OSCILLATE (https://www.nejm.org/doi/full/10.1056/NEJMoa1215554). Probably still used in some centres as a rescue therapy, but I haven't used it in years (we'd use VV ECMO for that purpose).

This infuriates me. It's cutting corners, reducing the quality of care.

There are now portable iron lungs that fit like a turtle shell. They do both inhalation and exhalation. That should be the only acceptable standard of care.

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