ON-LINE LUNG VOLUME MEASUREMENT DURING HIGH FREQUENCY OSCILLATORY VENTILATION (HFOV)

Zhang C.Y¹, Chen X.N², Zeng J.S³, Cui Y.T⁴, Wang Y.⁵, Fan X.M⁶

Intensive Care Unit, Beijing Children’s Hospital,

Capital University of Medical Science, Beijing, China

Objective: To determine whether Bag-in-box system can be used to measure mean lung volume (MLV) during HFOV. Bag-in-box system used in this study is an apparatus using closed circuit helium dilution technique to determine the functional residual capacity (FRC) during conventional mechanical ventilation (CMV).

Methods: Six mechanical lung models and ten New Zealand adult rabbits were used. Rabbits were divided into ‘health’ and ‘Acute Lung Injury (ALI) group’. All of them induced by infusing oleic acid intravenously. For lung model, a serial re-breathing process was performed. Lengthen the re-breathing time in 10 seconds stepwise to determine the time needed for equilibration. Then measure different size of models to test the sensitivity. In animal study, the equilibration time was determined, then measured the MLV after mean airway pressure (MAP) was changed.

Results: It reviewed that 50 seconds of re-breathing is enough for equilibration both in lung model and rabbits. In lung models, the measured and the real volume differed by –0.5%～4.4%. The measured and the real volume correlated well (P<0.001) in models ranging from 10-60ml. The coefficient of variations across 45 MLV determinations in rabbits varied between 0.5～6.5%. When MAP changed, MLV changes can be detected.

Conclusion: Bag-in-box system allowed relatively unbiased, precise and safe on-line MLV measurement in lung models ranging from 10-60ml, and in rabbits during HFOV.

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