If medicine used dogs, wouldn't every doctor's office need x different dogs trained in detecting x different diseases? Also, there are ethical considerations in

If medicine used dogs, wouldn't every doctor's office need x different dogs trained in detecting x different diseases? Also, there are ethical considerations in employing living creatures that can not possibly be fairly compensated. Development and use of an artificial nose would be superior, because only one (system) would be required, compared to i don't know how many dogs.