• Robinder G Khemani, Rutger Flink, Justin Hotz, Patrick A Ross, Anoopindar Ghuman, and Christopher J L Newth.
• 1] Department of Anesthesiology and Critical Care Medicine, Children's Hospital Los Angeles, Los Angeles, California [2] Department of Pediatrics, University of Southern California Keck School of Medicine, Los Angeles, California.
• Pediatr. Res. 2015 Jan 1; 77 (1-1): 75-83.

BackgroundWe sought to determine optimal methods of respiratory inductance plethysmography (RIP) flow calibration for application to pediatric postextubation upper airway obstruction.MethodsWe measured RIP, spirometry, and esophageal manometry in spontaneously breathing, intubated Rhesus monkeys with increasing inspiratory resistance. RIP calibration was based on: ΔµV(ao) ≈ M[ΔµV(RC) + K(ΔµV(AB))] where K establishes the relationship between the uncalibrated rib cage (ΔµV(RC)) and abdominal (ΔµV(AB)) RIP signals. We calculated K during (i) isovolume maneuvers during a negative inspiratory force (NIF), (ii) quantitative diagnostic calibration (QDC) during (a) tidal breathing, (b) continuous positive airway pressure (CPAP), and (c) increasing degrees of upper airway obstruction (UAO). We compared the calibrated RIP flow waveform to spirometry quantitatively and qualitatively.ResultsIsovolume calibrated RIP flow tracings were more accurate (against spirometry) both quantitatively and qualitatively than those from QDC (P < 0.0001), with bigger differences as UAO worsened. Isovolume calibration yielded nearly identical clinical interpretation of inspiratory flow limitation as spirometry.ConclusionIn an animal model of pediatric UAO, isovolume calibrated RIP flow tracings are accurate against spirometry. QDC during tidal breathing yields poor RIP flow calibration, particularly as UAO worsens. Routine use of a NIF maneuver before extubation affords the opportunity to use RIP to study postextubation UAO in children.

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