CF lung disease is characterized by chronic infection, inflammation, excess mucus and progressive airway obstruction. These processes are often complicated by acute or subacute exacerbations and lead to progressive respiratory impairment and failure. Hypoxemic respiratory failure refers to inadequate transfer of oxygen from the inspired air to the blood as it passes through the lungs. Oxygenation is further impaired by reduced alveolar ventilation and the resultant hypercapnia. Death from hypoxemic or hypercapnic respiratory failure may be due to progressive airway disease that becomes refractory to therapy, or to an acute complication, such as pneumothorax or massive hemoptysis.
More severe hypercapnia can cause coma and hypoxemia that is ultimately fatal.
Assisted ventilation can often reverse such complications, at least temporarily. A number of assistance methods have been developed. These ventilators periodically reduce the pressure around the chest, causing it to expand and draw air into the lungs. Such machines severely limit mobility and access to the chest, and are not suitable for use in CF patients. Other ventilators inflate the lungs by applying positive pressure to the airways, either directly into the trachea or via a nasal or face mask.