Early detection of deteriorating ventilation by monitoring bilateral chest wall dynamics in the rabbit.

Purpose: Mechanical complications during assisted ventilation can evolve due to worsening lung disease or problems in airway management. These complications affect lung compliance or airway resistance, which in turn affect the chest wall dynamics. The objective of this study was to explore the utility of continuous monitoring of the symmetry and dynamics of chest wall motion in the early detection of complications during mechanical ventilation.

Methods: The local tidal displacement (TDi) values of each side of the chest and epigastrium were measured by three miniature motion sensors in 18 rabbits. The TDi responses to changes in peak inspiratory pressure (n = 7), induction of one-lung intubation (n = 7), and slowly progressing pneumothorax (PTX) (n = 6) were monitored in parallel with conventional respiratory (SpO(2), EtCO(2), pressure and flow) and hemodynamic (HR and BP) indices. PTX was induced by injecting air into the pleural space at a rate of 1 mL/min.

Results: A strong correlation (R(2) = 0.99) with a slope close to unity (0.94) was observed between percent change in tidal volume and in TDi. One-lung ventilation was identified by conspicuous asymmetry development between left and right TDis. These indices provided significantly early detection of uneven ventilation during slowly developing PTX (within 12.9 ± 6.6 min of onset, p = 0.02) almost 1 h before the SpO(2) dropped (77.3 ± 27.4 min, p = 0.02). Decreases in TDi of the affected side paralleled the progression of PTX.

Conclusions: Monitoring the local TDi is a sensitive method for detecting changes in tidal volume and enables early detection of developing asymmetric ventilation.