Sensitivity of a simplified forced oscillation technique for detection of upper airway obstruction

The sensitivity of a simplified variant of forced oscillation technique (FO T) was studied for assessment of dynamic upper airway obstruction during na sal continuous positive airway pressure (nCPAP) therapy for obstructive sle ep apnoea (OSA), The airway impedance \P-FOT\ was measured by FOT and the o esophageal pressure (P-oes) was recorded during stable stage II sleep in 11 patients with OSA. The CPAP level was initially set high enough to complet ely abolish upper airway obstruction. To induce gradually increasing upper airway re-obstruction, the CPAP pressure was then lowered stepwise. Thirty six such manoeuvres were analysed, blind, to define the first inspiration a t which upper airway re-obstruction was detectable by analysis of \P-FOT\ ( t(FOT)) and by P-oes (t(oes)), respectively. On seven occasions t(FOT) and t(oes) occurred together, in the remaining 29 cases t(FOT) preceded t(oes) with a mean latency of 6.0 +/- 7.7 (0-32) breath cycles. In no case did t(o es) preceed t(FOT). FOT is a highly sensitive tool for the assessment of in cipient upper airway obstruction during nCPAP therapy. (C) 2001 Elsevier Sc ience B.V. All rights reserved.