Efficacy of endotracheal tube clamping to prevent positive airways pressure loss and pressure behavior after reconnection: a bench study

BACKGROUND: Endotracheal tube (ETT) clamping before disconnecting the patient from the mechanical ventilator is routinely performed in patients with acute respiratory distress syndrome (ARDS) to minimize alveolar de-recruitment. Clinical data on the effects of ETT clamping are lacking, and bench data are sparse. We aimed to evaluate the effects of three different types of clamps applied to ETTs of different sizes at different clamping moments during the respiratory cycle and in addition to assess pressure behavior following reconnection to the ventilator after a clamping maneuver. METHODS: A mechanical ventilator was connected to an ASL 5000 lung simulator using an ARDS simulated condition. Airway pressures and lung volumes were measured at three time points (5 s, 15 s and 30 s) after disconnection from the ventilator with different clamps (Klemmer, Chest-Tube and ECMO) on different ETT sizes (internal diameter of 6, 7 and 8 mm) at different clamping moments (end-expiration, end-inspiration and end-inspiration with tidal volume halved). In addition, we recorded airway pressures after reconnection to the ventilator. Pressures and volumes were compared among different clamps, different ETT-sizes and the different moments of clamp during the respiratory cycle. RESULTS: The efficacy of clamping depended on the type of clamp, the duration of clamping, the size of the ETT and the clamping moment. With an ETT ID 6 mm all clamps showed similar pressure and volume results. With an ETT ID 7 and 8 mm only the ECMO clamp was effective in maintaining stable pressure and volume in the respiratory system during disconnection at all observation times. Clamping with Klemmer and Chest-Tube at end inspiration and at end inspiration with halved tidal volume was more efficient than clamping at end expiration (p < 0.03). After reconnection to the mechanical ventilator, end-inspiratory clamping generated higher alveolar pressures as compared with end-inspiratory clamping with halved tidal volume (p < 0.001). CONCLUSIONS: ECMO was the most effective in preventing significant airway pressure and volume loss independently from tube size and clamp duration. Our findings support the use of ECMO clamp and clamping at end-expiration. ETT clamping at end-inspiration with tidal volume halved could minimize the risk of generating high alveolar pressures following reconnection to the ventilator and loss of airway pressure under PEEP.