 Children who need to be on a ventilator often have thick secretionsmucus in their lungs. These secretions can obstruct the breathing tube and their windpipe, which can worsen lung function and prolong the need for the ventilator. Hypertonic saline is a medicine that is used to thin out secretions in patients with cystic fibrosis and other conditions. We hypothesize that having children on a ventilator inhale this medication will shorten the amount of time that they need to be on the ventilator. 