Just by changing their lifestyle, humans are challenging the respiratory system to an extent never previously reached; by exposing it to extreme conditions. In an article in this issue of the European Respiratory Review, Adir and Bove [1] have deciphered the conditions that may promote lung injury when the respiratory system is exposed to low atmospheric pressure, high pressure surrounding the body and extreme exercise. The intensive care unit (ICU) can also be seen as an extreme environment for the respiratory system. This is because ICU management is required for the most severe forms of acute lung disease, in particular acute respiratory distress syndrome (ARDS), and the components of the management may be extreme, such as prone positioning [2] or extracorporeal lung oxygenation [3]. Therefore, I would like to discuss some aspects of hypoxaemia and mechanical ventilation that occur in the ICU, and which closely link to the cases described by Adir and Bove [1].
The main advance in ARDS management is the limitation of pressure and volume [4], which is delivered by the ventilator and applied to the respiratory system, with the primary goal of minimising ventilator-induced lung injury (VILI) [5]. Using a lower tidal volume (targeting 6 mL·kg−1 predicted body weight), set by the ventilator, has been shown to improve survival to a two-fold higher volume in higher compared to lower tidal volume [4]. Targeting modest oxygenation (arterial oxygen tension (PaO2) 55–80 mmHg) is also a component of lung-protective mechanical ventilation. The rationale for this is four-fold. First, targeting higher PaO2 (e.g. 100 mmHg) would commit the clinician to use potential harmful values of ventilator settings. For instance, higher positive end-expiratory pressure (PEEP) may …
