My Dad, Age 80 Was Hospitalized In October For Aspirational

My dad, age 80 was hospitalized in October for aspirational pneumonia and septic shock. Receives all nutrition thru feeding tube. Cannot swallow anything due to scarring from radiation to his throat from cancer 32 years ago. Having problems with low blood pressure and coughing a thick mucus. Very difficult for him to get the mucus up. Could the thick mucus he trying to get up be caused by dehydration?