Is smaller high enough? Another piece in the puzzle of stress, strain, size, and systems

Extracorporeal lung-supporting procedures open the possibility of staying within widely accepted margins of 'protective' mechanical ventilation (tidal volume of less than 6 mL per kg of predicted ideal body weight and plateau pressure of less than 30 cm H₂O) in most any case of respiratory failure or even of further reducing ventilator settings while still providing adequate gas exchange. There is evidence that, at least in some patients, a further reduction in tidal volumes might be beneficial. Extracorporeal procedures to support the lungs have undergone tremendous technical developments, thus reducing the procedure-related risks. However, what is true for ventilator settings should also be true for extracorporeal procedures: studies will have to demonstrate a convincing risk-benefit ratio. In addition, a simple reduction of the tidal volume will certainly not be the right answer. If extracorporeal support largely influences gas exchange, the 'optimal' tidal volume/positive end-expiratory pressure ratio keeping stress and strain low and avoiding alveolar derecruitment will still have to be individually defined.