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
Haryadi, Ph.D.2
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.
Reference:
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.