The Vitals: Barotrauma

Preventing Barotrauma

We can best protect our patients against this potentially devastating complication by ensuring the following:

• Application of Tidal Volume: Low tidal volume or Arbitrarily determined?
  The revolutionary ARDSnet study demonstrated a mortality benefit by targeting patients to receive a tidal volume of 6 rather than 12 ml/kg of predicted body weight. As mentioned earlier, alveolar pressures are adversely affected by larger tidal volumes and poor lung compliance. This causes the alveolar pressure to rise and, in turn, transpulmonary pressure along with it. Pressure controlled ventilation may be advantageous as it allows us to set the driving pressure to a safe value that minimizes the risk of causing lung injury. The caveat to this approach is that in conditions with poor lung compliance (ARDS), setting low driving pressures may lead to inadequate ventilation and life-threatening respiratory acidosis. Volume controlled ventilation may be advantageous as it allows us to set the ventilator to deliver a pre-determined, safe volume which would ideally minimize lung injury while adequately ventilating the patient. The caveat to this approach, however, is that regardless of lung compliance, the ventilator will attempt to deliver the programmed tidal volume even if it requires dangerously high driving pressures to accomplish this. ECMO then becomes a worthwhile consideration if the patient cannot be adequately ventilated without the application of exceedingly high driving pressures that only further lung injury and increase the risk of barotrauma.
• Application of PEEP: Strategic rather than aimlessly increasing? Intrinsic PEEP?
  PEEP must always be applied strategically to minimize harm. When we apply PEEP, the goal should be to titrate PEEP towards maximal lung recruitment. Further increments in PEEP cause overdistension of the alveoli increasing the susceptibility for alveolar rupture. In conditions associated with dynamic hyperinflation such as obstructive lung disease, large tidal volumes combined with low expiratory times creates air-trapping or “Intrinsic PEEP”. With the accumulation of Intrinsic PEEP, alveolar distension progressively worsens increasing the risk of rupture. Minimize this risk by delivering lower tidal volumes at faster inspiratory flow rates, which allows you the opportunity to provide maximal expiratory time for the patient’s lungs to fully deflate.
• Plateau Pressure: Maintain =< 30 cm H2O
  This can be achieved by maintaining a strategy of low tidal volume ventilation while minimizing excessive application of PEEP. It is also of importance to note that plateau pressure describes the total alveolar pressure rather than the alveolar pressure in separate regions of the lung that may be more diseased than in other regions. In those severely affected regions, the lung may be more susceptible to injury even despite maintaining plateau pressure <30. In that sense, the aim should really be to minimize plateau pressures as low as possible.
• Patient-Ventilator Synchrony: Optimal or Completely Dyssynchronous
  To maximize patient safety during invasive ventilation, it is imperative to ensure patient comfort and synchronize the ventilator in such a manner that matches the needs of the patient along with their underlying pathophysiology. Maladaptive interactions between the patient and ventilator can lead to dyssynchronies such as double triggering, which exposes the lungs to much higher tidal volumes with each breath and increases the risk of lung injury. Optimizing analgesia is of crucial importance; however, maximizing sedation and even brief periods of medical paralysis may, at times, be necessary to ensure patient safety.