RESPIRATORY RESISTANCE BY END-INSPIRATORY OCCLUSION AND FORCED-OSCILLATIONS IN INTUBATED PATIENTS

Measurement of respiratory impedance by the forced oscillation techniq ue (FOT) in intubated patients requires corrections for the flow-depen dent resistance, inertance, and air compression inside the endotrachea l tube (ETT). Recently, we published a method to correct respiratory i mpedance for the mechanical contribution of the ETT. To validate this correction, we compared the respiratory resistance obtained with this method (R(fo)) to the intrinsic (R(min)) and total resistances (RT) me asured by the airway-occlusion technique (OCT) in 16 intubated sedated paralyzed ventilated patients. The FOT was applied at functional resi dual capacity in the 4- to 32-Hz frequency range, whereas the OCT was performed at the end of a normal constant-flow inspiration. R(min), co rrelated with R(fo) measured at 16 and 32 Hz [R(fo)(16) = 1.10 x R(min ) + 0.10 cmH(2)O . s . l(-1), r = 0.96, P < 0.001; R(fo)(32) = 0.93 x R(min) + 0.72 cmH(2)O . s . l(-1), r = 0.97, P < 0.001]. RT correlated with R(fo) at 4 Hz [R(fo)(4) = 1.11 x RT - 1.48 cmH(2)O . s . l(-1); r = 0.92; P < 0.001]. We conclude that the FOT improved by corrections for the behavior of the ETT is in good agreement with the OCT in intu bated patients.