The highest angle at which a hospital bed can be set to can vary depending on the type and model of the bed. Generally speaking, the head section of a hospital bed can typically be adjusted to an angle of up to around 90 degrees (Certainly none the home hospital beds we have ever sold raise to any more than 70 degrees), while the foot section can typically be adjusted to an angle of up to around 45 degrees. (it is really the under the knee section that raises up, not under the foot section, and it goes up to between 30 and 40 degrees depending on the model).
However, some newer models of hospital beds have the ability to adjust the angle of the head section to an angle greater than 90 degrees. (Beds that are able to operate in Trendelberg positions could do this but there is no reason to do so in a home setting).
It's best to check the specifications of the bed or ask the manufacturer for the maximum angle for the specific bed in question. ( Always true, and even better visit our Mississauga showroom to see for yourself)