your brother may have been on diuretics since some time.These are drugs which speed up removal of fluids from the body thro' kidney
in conditins like congestive heart failure
.These are known to produce,esp.Lasix sensorineural hearing loss
.Though you have not specified it,you must have done a hearing test to conclude with surety the percentage of his hearing loss.In such case,he is not likely to improve in hearing,will need hearing aid
to help him.It is not due to blowing of nose.