Acute and Critical Care

Original Articles

Pulmonary
Evaluation of Respiratory Dynamics in an Asymmetric Lung Compliance Model: So Hui Yun, Ho-Jin Lee, Yong-Hun Lee, Jong Cook Park; Korean J Crit Care Med. 2017;32(2):174-181. Published online April 14, 2017; DOI: https://doi.org/10.4266/kjccm.2016.00738

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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 (V_L1/V_L2) 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, 0.95 cmH₂O) in the C60 group; and ID 3, 4, and 5 mm (2.92, 1.84, 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.

Citations

Citations to this article as recorded by

Proof-of-concept study of compartmentalized lung ventilation using system for asymmetric flow regulation (SAFR)
Igor Barjaktarevic, Glen Meyerowitz, Onike Williams, I. Obi Emeruwa, Nir Hoftman
Frontiers in Medical Technology.2023;[Epub] CrossRef
Is It Essential to Consider Respiratory Dynamics?
Youngjoon Kang
The Korean Journal of Critical Care Medicine.2017; 32(2): 223. CrossRef

Collagen Synthesis in an in Vivo Rat Model of Ventilator-induced Lung Injury: Won Il Choi; Korean J Crit Care Med. 2006;21(2):109-115.

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Abstract PDF: BACKGROUND
Experimentally, maintaining high pressure or high volume ventilation in animal models produces an acute lung injury, however, there was little information on remodeling. We investigated the collagen synthesis in a rat model of ventilator-induced lung injury.
METHODS
Rats were ventilated with room air at 85 breaths/minute for 2 hours either tidal volume 7 ml/kg or 20 ml/kg (V(T)7 or V(T)20, respectively). After 2 hours of ventilation, rats were placed in the chamber for 24 hours. Lung collagen was evaluated by immunohistochemistry (n=5) and collagen was quantitated by collagen assay (n=5). Static compliance (Csta) of the whole lung as obtained from the pressure volume curves.
RESULTS
Type I collagen was an increase in expression in the interstitium with large V(T) (20 ml/ kg) ventilation after 2 hours of mechanical ventilation (MV), and further increased expression after 24 hours of recovery period. Static lung compliance was significantly (p<0.05) decreased in the V(T)20 compared with V(T)7 (0.221+/-0.05 vs 0.305+/-0.06 ml/cm H2O) after 2 hours of MV. There was a further decrease in lung compliance after 24 hours of recovery period (0.144+/-0.07 vs 0.221+/-0.05, p<0.05) in the V(T)20.
CONCLUSIONS
Large tidal volume ventilation causes an increase in type 1 collagen expression with reduction of lung compliance.

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