So standard pressure at sea level is 29.92inHg, a 737 MAX can sustain 39k ft altitude indefinitely I suppose, where the exterior air pressure would be 7.66inHg. The cabin is normally pressurized to the equivalent of 8k ft, giving 26.63inHg. The fuselage could withstand a pressure differential of 26.63inHg - 7.66inHg = 18.97inHg (at least, possibly more).
That’s 63% higher than regular pressure at sea level. Not bad.
If you gave each patient a full economy row, that’s about 60 patients per plane, so 48k patients across 800 grounded 737 MAXs.