your doc is right - 7% saline CAN cause bronchospasm, especially for folks who may have reactive airways. It can irritate the airways. In fact, 7% saline is sometimes used for specific pulm testing, testing for reactive airways, e.g. asthma. If bronchospasm occurs, taking a bronchodilator (e.g. Albuterol) can help alleviate the constriction and spasming of the airways. As it's being discussed here, the 7% saline is used to loosen/thin secretions -- it can be safe if rx'd properly -- having a discussion with your doc about it and your specific lung conditions would be advised.