RESPIRATORY RESISTIVE IMPEDANCE AS AN INDEX OF AIRWAY-OBSTRUCTION DURING NASAL CONTINUOUS POSITIVE AIRWAY PRESSURE TITRATION

Esophageal pressure amplitude (Delta Pes), inspiratory pulmonary resis tance (RLI) and inspiratory flow limitation score (FS) are used as ind ices of upper airway obstruction for the titration of nasal continuous positive airway pressure (nCPAP) in patients with obstructive sleep a pnea syndrome (OSAS). This study was designed to determine whether osc illatory respiratory resistive impedance at 16 Hz (RFO) might be propo sed as an alternative index. Eleven OSAS patients were studied during a night of polysomnography-controlled nCPAP titration. Nasal flow ((V) over dot) and airway opening and esophageal pressures (Pao and Pes, r espectively) were continuously measured during nasal breathing, and fo rced-flow oscillations (FO) were applied for 5 min at each nCPAP level . RLI was calculated by linear regression analysis of resistive pressu re versus (V) over dot over inspiration. RFO was obtained by linear re gression analysis of respiratory resistive impedance versus frequency. Application of FO affected neither sleep nor pulmonary mechanics. RFO correlated with Ru in all patients. RFO did not correlate with Delta Pes in two patients, and was not significantly related to FS in five p atients. This study demonstrates the applicability of the FO technique in sleeping patients receiving nCPAP, and the reliability of RFO for assessing pulmonary resistance. RFO might therefore be proposed as a q uantitative index of airway obstruction for nCPAP titration.