2006 OPEN FORUM Abstracts
MEASUREMENT OF ALVEOLAR LUNG CLEARANCE INDEX IN AN OLEIC ACID INDUCED ACUTE LUNG INJURY ANIMAL MODEL
Lara Brewer, M.S.1 Joseph Orr, Ph.D.1 and Dinesh
1.Anesthesiology, University of Utah, Salt Lake City, Utah, United States. 2.Respironics Inc, Wallingford, Connecticut, United States.
Background: One of the primary goals of ventilation in patients with acute lung injury (ALI) is to improve gas exchange by recruiting additional alveoli. If ventilation is not evenly distributed to the newly opened alveoli, the ventilation remains inefficient. One measure of the additional alveolar volume to ventilation balance is the Alveolar Lung Clearance Index (ALCI), which is a measurement of the alveolar volume turnovers required to reduce the concentration of the tracer gas to 1/40th the original concentration1. In this study, we measured how ALCI was affected by addition of positive end-expiratory pressure (PEEP) in both healthy and oleic acid induced ALI lung models. Materials and
Methods: Measurements of airway Deadspace (VDaw), alveolar tidal volume (VTalv), PEEP, and end-tidal CO2 (etCO2) were obtained from a NICO2 Respiratory Profile Monitor (Respironics, Inc.; Wallingford, CT) and end-tidal oxygen was measured using a paramagnetic oxygen analyzer (Capnomac, Datex, Helsinki, Finland) in six mechanically ventilated swine (38-49 kg). Functional Residual Capacity (FRC) measurements based on Nitrogen washout method were obtained by increasing FIO2 incrementally by 20%. The experiment was divided into two phases: 1) healthy lungs and 2) oleic acid-induced ALI which was created by intravenously infusing 0.09 mL/kg of oleic acid over a 15-minute period. PEEP was increased in steps of 5 cmH2O (range = 0 to 15 cmH2O) during each phase. ALCI was calculated by dividing the alveolar cumulative expired volume (ACEV) of nitrogen by the FRC at each PEEP level.
Results: In healthy lungs, ALCI was relatively stable at all levels of PEEP. In injured lungs, the ALCI was improved with 10 cm H2O of PEEP and returned to the healthy lungs level with a PEEP of 15 cm H2O.
Discussion: The ALCI can be an effective measure of the effect of recruitment on the distribution of alveolar ventilation relative to alveolar volume.
1) Pillow JJ, Frerichs I, Stocks J. Lung function tests in neonates and infants with chronic lung disease: global and regional ventilation inhomogeneity. Pediatr Pulmonol. 2006 Feb;41(2):105-21.