Measurement of pharyngeal pressure in patients using nasal CPAP

In patients with obstructive sleep apnea syndrome (OSAS), nasal continuous positive airway pressure (nCPAP) prevents pharyngeal collapse by applying positive pressure transnasally. Currently there are not objective criteria to determine whether surgical improvement of nasal resistance is necessary in patients undergoing nCPAP treatment. In 16 patients with documented OSAS, inspiratory and expiratory pressures in the pharynx were measured during nCPAP with pressures ranging from 5 to 20 mbar. Identical studies were performed in 12 patients with severe nasal obstruction without OSAS and in eight normal patients. The results of each group were compared to the nasal resistance as measured by acoustic rhinometry. The pharyngeal pressures under nCPAP were found to be independent of nasal resistance and of the minimal cross-sectional area of the nose. additionally, nCPAP tvas effective in individuals with severe nasal obstruction. Nasal obstruction has no influence on nasal pressure when using nCPAP. Perhaps other factors, such as collapsing of the pharynx or tone of the pharyngeal muscles, play a role in determining the nasal pressure of the nCPAP.