Why is my husband passing out while coughing?

Could: be an exaggerated vagal response from increased neck pressure caused by coughing. This could be an early symptom of significant atherosclerotic peripheral and/or coronary artery disease. I recommend a cardiologist evaluation ASAP.

Vasovagal vs. other: Many people, especially young ones, get a vasovagal reflex (dizziness, sweating, fainting, etc) with certain procedures or activities that stimulate the vagus nerve. Although this can be very frightening, it is not dangerous and may not recur. However, older people who are experiencing fainting spells should be evaluated by their physician to confirm that more serious conditions are not present

Cough: Its called cough syncope and may imply that there he's having an irregular heartbeat when he does. He needs to check this out ASAP with a cardiologist

Cough syncope: Fainting or syncope may occur during violent coughing spells (especially in men) because of rapid changes in blood pressure. As the bouts of coughing start, the blood pressure drops and blood flow to the brain decreases temporarily causing the patient to pass out for a few seconds. If this is a recurrent problem please see your doctor to rule out other more sinister causes of fainting