If you feel like there is a vacuum on your home while your air conditioning system is running, you could have a problem with your duct work. One symptom of a vacuum on your home is your outside doors being more difficult to open out when the air conditioning is running. Most of the time this is caused by an air leak on the supply side of your duct work. This causes your air conditioning system to remove more air from your home than it is putting back in causing a vacuum on your home while the system is running. To fix this your duct system should be inspected and any air leaks be repaired.
Below is a picture where a supply plenu came loose from an air handler.