Author/Authors :
Yun, So Hui Department of Anesthesiology and Pain Medicine - Jeju National University School of Medicine, Jeju , Lee, Ho-Jin Department of Anesthesiology and Pain Medicine - Seoul National University Hospital, Seoul , Lee, Yong-Hun Department of Anesthesiology and Pain Medicine - Asan Medical Center - University of Ulsan College of Medicine - Seoul, Korea , Park, Jong Cook Department of Anesthesiology and Pain Medicine - Jeju National University School of Medicine, Jeju
Abstract :
Background: Unilateral lung hyperinflation develops in lungs with asymmetric compliance, which can lead to vital instability. The aim
of this study was to investigate the respiratory dynamics and the effect of airway diameter on the distribution of tidal volume during
mechanical ventilation in a lung model with asymmetric compliance.
Methods: Three groups of lung models were designed to simulate lungs with a symmetric and asymmetric compliance. The lung
model was composed of two test lungs, lung1 and lung2. The static compliance of lung1 in C15, C60, and C120 groups was manipulated to be 15, 60, and 120 ml/cmH2O, respectively. Meanwhile, the static compliance of lung2 was fixed at 60 ml/cmH2O. Respiratory
variables were measured above (proximal measurement) and below (distal measurement) the model trachea. The lung model was
mechanically ventilated, and the airway internal diameter (ID) was changed from 3 to 8 mm in 1-mm increments.
Results: The mean ± standard deviation ratio of volumes distributed to each lung (VL1/VL2) in airway ID 3, 4, 5, 6, 7, and 8 were in order,
0.10 ± 0.05, 0.11 ± 0.03, 0.12 ± 0.02, 0.12 ± 0.02, 0.12 ± 0.02, and 0.12 ± 0.02 in the C15 group; 1.05 ± 0.16, 1.01 ± 0.09, 1.00 ± 0.07, 0.97
± 0.09, 0.96 ± 0.06, and 0.97 ± 0.08 in the C60 group; and 1.46 ± 0.18, 3.06 ± 0.41, 3.72 ± 0.37, 3.78 ± 0.47, 3.77 ± 0.45, and 3.78 ± 0.60
in the C120 group. The positive end-expiratory pressure (PEEP) of lung1 was significantly increased at airway ID 3 mm (1.65 cmH2O) in
the C15 group; at ID 3, 4, and 5 mm (2.21, 1.06, and 0.95 cmH2O) in the C60 group; and ID 3, 4, and 5 mm (2.92, 1.84, and 1.41 cmH2O)
in the C120 group, compared to ID 8 mm (P < 0.05).
Conclusions: In the C15 and C120 groups, the tidal volume was unevenly distributed to both lungs in a positive relationship with
lung compliance. In the C120 group, the uneven distribution of tidal volume was improved when the airway ID was equal to or less
than 4 mm, but a significant increase of PEEP was observed.
Keywords :
airway obstruction , lung compliance , positive-pressure respiration , intrinsic , ventilation
