ARDS: refractory hypoxaemia and supportive care

Acute respiratory distress syndrome is not a disease the patient arrived with but an acute inflammatory injury to the alveolar-capillary membrane that follows some other insult -- sepsis above all, and also pneumonia, aspiration of gastric contents, major trauma, burns, pancreatitis, massive transfusion, near-drowning, inhalation injury and shock -- so it arises within days in a patient who was breathing adequately before it, floods the alveoli with protein-rich fluid, stiffens the lung and shunts blood past alveoli that are no longer being ventilated; what identifies it at the bedside is therefore not a new sign but a failure to respond -- breathlessness and a respiratory rate that climb, a patient who is restless, anxious and using the accessory muscles, fine crackles through both lungs, and a saturation and an arterial oxygen level that stay low or fall further while the oxygen is being turned up, which is the refractory hypoxaemia that defines the syndrome -- read together with bilateral opacities on chest imaging and the absence of a cardiac explanation, because a failing left ventricle and fluid overload flood the lungs in the same way and are what this syndrome is distinguished from rather than what it is; so the nurse who sees the oxygen requirement climbing without effect escalates rather than titrating, staying with the patient, sitting them upright, calling the team early and preparing for intubation and mechanical ventilation before exhaustion arrives, because these patients tire and arrest rather than settle onto a plateau; and once the patient is supported the care is supportive rather than curative -- nothing reverses the injury, so the lung is given time by ventilating it gently with a small tidal volume set on predicted body weight and a limited plateau pressure, accepting a carbon dioxide that rises and an oxygen target lower than the usual one rather than forcing either back to normal, keeping the positive end-expiratory pressure that holds the alveoli open unbroken so the circuit is not opened for suction or for turning, proning the patient for the greater part of the day in severe disease with the eyes, the face, the pressure areas, the lines and above all the airway protected through every turn, sedating and where it is ordered paralysing with the sedation always established first and a paralysed patient never left unsedated, keeping the fluid balance conservative once the circulation will allow it, treating the insult that caused the syndrome rather than the lung alone, and giving the corticosteroid, the neuromuscular blocker or the referral for extracorporeal support that the team decides on -- while what that support costs is watched for as closely as the syndrome itself: the barotrauma that declares itself as a sudden pneumothorax or as airway pressures that climb while the blood pressure falls, the ventilator-associated pneumonia the prevention bundle exists for, the delirium, the acquired weakness and the pressure injury of sedation and immobility, and the falling blood pressure that positive pressure and sedation produce in a patient who cannot simply be filled.