Respiratory Resistive Impedance as an Index of Airway Obstruction during Nasal Continuous Positive Airway Pressure Titration

Esophageal pressure amplitude ( Δ Pes), inspiratory pulmonary resistance (Rli) and inspiratory flow limitation score (FS) are used as indices of upper airway obstruction for the titration of nasal continuous positive airway pressure (nCPAP) in patients with obstructive sleep apnea syndrome (OSAS). This study was designed to determine whether oscillatory respiratory resistive impedance at 16 Hz (Rfo) might be proposed as an alternative index. Eleven OSAS patients were studied during a night of polysomnography-controlled nCPAP titration. Nasal flow (V˙) and airway opening and esophageal pressures (Pao and Pes, respectively) were continuously measured during nasal breathing, and forced-flow oscillations (FO) were applied for 5 min at each nCPAP level. Rli was calculated by linear regression analysis of resistive pressure versus V˙ over inspiration. R fo was obtained by linear regression analysis of respiratory resistive impedance versus frequency. Application of FO affected neither sleep nor pulmonary mechan...