Clamp to prevent collapse

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.

Does endo-tracheal tube clamping prevent air leaks and maintain positive end-expiratory pressure during the switching of a ventilator in a patient in an intensive care unit? A bench study

Objectives

When patients with acute respiratory distress syndrome are moved out of an intensive care unit, the ventilator often requires changing. This procedure suppresses positive end expiratory pressure and promotes lung derecruitment. Clamping the endotracheal tube may prevent this from occurring. Whether or not such clamping maintains positive end-expiratory pressure has never been investigated. We designed a bench study to explore this further.

How the study was done

We used the Elysee 350 ventilator in ‘volume controlled’ mode with a positive end-expiratory pressure of 15 cmH2O, connected to an endotracheal tube with an 8 mm internal diameter inserted into a lung model with 40 ml/cmH2O compliance and 10 cmH2O/L/s resistance. We measured airway pressure and flow between the distal end of the endotracheal tube and the lung model. We tested a plastic, a metal, and an Extra Corporeal Membrane Oxygenation clamp, each with an oral/nasal, a nasal, and a reinforced endotracheal tube. We performed an end-expiratory hold then clamped the endotracheal tube and disconnected the ventilator. We measured the change in airway pressure and volume for 30 s following the disconnection of the ventilator.

Results

Airway pressure decreased thirty seconds after disconnection with all combinations of clamp and endotracheal tube. The largest fall in airway pressure (-17.486 cmH₂O/s at 5 s and -18.834 cmH₂O/s at 30 s) was observed with the plastic clamp combined with the reinforced endotracheal tube. The smallest decrease in airway pressure (0 cmH₂O/s at 5 s and -0.163 cmH₂O/s at 30 s) was observed using the Extra Corporeal Membrane Oxygenation clamp with the nasal endotracheal tube.

Conclusions

Only the Extra Corporeal Membrane Oxygenation clamp was efficient. Even with an Extra Corporeal Membrane Oxygenation clamp, it is important to limit the duration the ventilator is disconnected to a few seconds (ideally 5 s).