The Science Journal of the American Association for Respiratory Care

2004 OPEN FORUM Abstracts

EXOGENOUS KL4 SURFACTANT REDUCES ALVEOLAR OPENING PRESSURE IN SALINE LAVAGE-INJURED LUNGS

Joseph D DiRocco MD, Lucio A Pavone MD, Charles J Lutz MD, Kathy P Snyder RN, Gary F Nieman BA. Department of Surgery – SUNY - Upstate Medical University

Introduction: Surfactant dysfunction in acute lung injury can cause heterogeneous patterns of microatelectasis and render alveoli unstable. High-pressure recruitment maneuvers have been advocated to open these collapsed alveoli. High peak pressures may also be injurious. We hypothesize that the administration of an exogenous, peptide-containing synthetic surfactant (KL4) will reduce the pressure required to recruit alveoli. We assessed the opening of alveoli by direct in vivo microscopic observation.

Methods: Sprague-Dawley rats were mechanically ventilated with 100% O2. Right thorectomy was performed in all animals for exposure of the right lung. All rats underwent staged recruitment maneuvers (RM) while subpleural alveoli were recorded with videomicroscopy (Table, Baseline). Each RM consisted of 10 cm H2O increments in airway pressure from 10 to 40 cm H2O. After baseline RM, all animals were subjected to repeated saline lavage injury until PaO2 < 150 mm Hg. RM with videomicroscopy were repeated after injury (Table, Injury). Animals then received either KL4 (100mg/kg of 30mg/cc, n=5) or buffered saline (3.3 cc/kg, n=3) followed by another RM under videomicroscopy (Table, Sham Group or KL4 Group). Computer image analysis of the recorded video at each pressure identified the number of alveoli per mm2 field and the percent of field with aerated alveoli. All values reported as mean ± SEM. * = p < 0.05 for ANOVA and Tukey HSD vs. Baseline, † = p < 0.05 vs. Sham.

Results:

  10 cm H2O 20 cm H2O 30 cm H2O 40 cm H2O
# Alveoli / mm2
Baseline 137 ± 6 137 ± 6 137 ± 6 137 ± 6
Injury 4 ± 1* 10 ± 1* 21 ± 2* 36 ± 3*
Sham Group 5 ± 2* 12 ± 3* 24 ± 5* 39 ± 7*
KL4 Group 25 ± 5* 36 ± 5*† 60 ± 5*† 84 ± 5*†
% Aerated
Baseline 44 ± 3 46 ± 3 43 ± 5 46 ± 4
Injury 4 ± 1* 10 ± 1* 17 ± 1* 21 ± 2*
Sham Group 5 ± 2* 12 ± 2* 16 ± 2* 21 ± 3*
KL4 Group 18 ± 3* 25 ± 3* 32 ± 3† 38 ± 3†

Conclusion: In the normal lung, increases in pressure above 10 cm H2O do not result in further alveolar recruitment. In the injured lung, the majority of subpleural alveoli were collapsed at 10 cm H2O and only partially recruited by 40 cm H2O. KL4 surfactant therapy significantly increased the degree of alveolar recruitment after injury at lower pressures. This reduction of necessary alveolar recruiting pressure will ameliorate the negative consequences of recruitment maneuvers.

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