Valsalva's maneuver occurs when you hold your breath and lift something or bear down like when straining to have a bowel movement. It's an increase in the pressure inside the chest and abdomen. It also occurs when lifting heavy objects or anytime you cough or sneeze forcibly.
The maneuver causes trapping of blood in the large veins, keeping it from moving into the chest and heart. When the breath is let out, the pressure drops and the blood moves quickly through the heart. This increases the heart rate and blood pressure.
Most patients are advised to avoid this maneuver after any major surgery. It can bring about a heart attack in anyone with heart disease. It can rupture a weak blood vessel. It can also disrupt the spine in patients who have just had back surgery.
Your husband should follow any instructions given about lifting. Whenever lifting he should contract his abdominal muscles by pulling his belly button in toward his spine. He should not hold his breath. A good way to lift is to take a normal breath, pull the abdominals in, and let the breath out while lifting while keeping the abdominal muscles tight until the lift is done.