Bronchial blockers under pressure: in vitro model and ex vivo model

Background

Pressures (P_e) exerted by bronchial blockers on the inner wall of the bronchi may cause mucosal ischaemia. Our aims were as follows: (i) to compare the intracuff pressure (P_i) and P_e exerted by commercially available bronchial blockers in an in vitro and an ex vivo model; (ii) to investigate the influence of both the inflated intracuff volume and cuff diameter on P_e; and (iii) to estimate the minimal sealing volume (V_Smin) and the corresponding P_e for each bronchial blocker studied.

Methods

The P_e exerted by seven commercial bronchial blockers was measured at different inflation volumes using a custom-designed system using in vitro and ex vivo animal models with two internal diameters (12 and 15 mm).

Results

In the same conditions, P_i was significantly lower than P_e (P<0.05), and P_e was higher in the in vitro model than in the ex vivo model. The P_e increased with the inflated volume, with use of the small-diameter model (P<0.05). Ex vivo models needed a higher minimal sealing volume than the in vitro models, and this volume increased with the diameter (e.g. the V_Smin at a positive pressure of 25 cm H₂O required a P_e ranging from 12 to 78 mm Hg on the 15 mm ex vivo model and from 66 to 110 mm Hg on the 12 mm ex vivo model).

Conclusions

The P_i cannot be used to approximate P_e. The diameter of the model, the inflated volume, and the bronchial blocker design all influence P_e. A pressure higher than the critical ischaemic threshold (i.e. 25 mm Hg) was needed to prevent air leak around the cuff in the in vitro and ex vivo models.

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