The effect of fibreoptic bronchoscopy in acute respiratory distress syndrome: experimental evidence from a lung model

Abstract

SummaryFlexible bronchoscopy is essential for appropriate care during mechanical ventilation, but can significantly affect mechanical ventilation of the lungs, particularly for patients with acute respiratory distress syndrome. We aimed to describe the consequences of bronchoscopy during lung‐protective ventilation in a bench study, and thereby to determine the optimal diameter of the bronchoscope for avoiding disruption of the protective‐ventilation strategy during the procedure. Immediately following the insertion of the bronchoscope into the tracheal tube, either minute ventilation decreased significantly, or positive end‐expiratory pressure increased substantially, according to the setting of the inspiratory pressure limit. The increase in end‐expiratory pressure led to an equivalent increase in the plateau pressure, and lung‐protective ventilation was significantly altered during the procedure. We showed that a bronchoscope with an external diameter of 4 mm (or less) would allow safer bronchoscopic interventions in patients with severe acute respiratory distress syndrome.

Evaluation of a flexible bronchoscope prototype designed for bronchoscopy during mechanical ventilation: a proof‐of‐concept study

“…For example, we observed an increase of 10 cmH 2 O in total-PEEP and Pplat directly after insertion of the adult bronchoscopes into the 7.0mm tracheal tube. The increase in Pplat was almost identical to that of the PEEP under these conditions, as previously demonstrated [10]. In contrast, the paediatric and prototype bronchoscopes did not disrupt lung-protective ventilation; there was no clinically significant modification of pulmonary pressures.…”

“…Thus, it was important to confirm our experimental results using an animal model. We obtained similar results regardless of the model used; a substantial rise in total-PEEP with an adult bronchoscope, and no effect of bronchoscopy on the ventilatory MV (l.min -1 ) 10 20 30 Pressure (cmH2O) 10 20 30…”

“…Next, we tested the effects of various bronchoscope/tracheal tube combinations on minute ventilation and PEEP. To do this, we used a controlled, high fidelity breathing simulator (Model 5600i, Dual Adult Pneuview System, Michigan Instruments, Grand Rapids, USA) to simulate the respiratory mechanics of adults with pathological lung function corresponding to severe ARDS [10,16]. Parameters for the ARDS lung were based on the PROSEVA study [17], and corresponded to severe ARDS according to the Berlin definition criteria [16].…”

“…Severe hypoxaemia (PaO 2 /F I O 2 < 100) is a contra-indication to bronchoalveolar lavage of the lungs in ARDS patients, due to the balance between risk and safety [9]. We have previously shown that a bronchoscope with an external diameter of 4 mm (or less) allowed safer bronchoscopic interventions in patients with ARDS [10]. Flexible bronchoscopes with a reduced diameter have been developed [11]; however, it has not previously been possible to reduce the external diameter of the bronchoscope without reducing the diameter of the suction channel, due to the optical fibres necessary for light transmission that fill the inner part of the bronchoscope.…”

Fibreoptic bronchoscopy in patients with acute respiratory distress syndrome

“…We would like to invite Nay et al. to explain in detail how they managed to simulate acute respiratory distress syndrome (ARDS) in the lung models used in their recent study of fibreoptic bronchoscopy , as to date, artificial models have been unable to replicate accurately the complex pathophysiology of the ARDS lung.…”