Perhaps a better definition of hypoxemia is a PaO2 that is associated with continued tissue hypoxia (rising lactate, low ScvO2), the need for vasopressor medications, or severe metabolic acidosis.
For ED patients that remain hypoxemic despite increased FiO2 and high levels of PEEP, consider the following rescue therapies:
Recruitment maneuvers - brief periods of high PEEP (35-50 cm H2O) or pressure-controlled breaths to reopen collapsed alveoli
High-frequency oscillatory ventilation - employs a high airway pressure to recruit closed alveolar segments
Prone positioning - believed to improve oxygenation through a redistribution of ventilation and perfusion
Extracorporeal membrane oxygenation
References
Patroniti N, Isgro S, Zanella A. Clinical management of severely hypoxemic patients. Curr Opin Crit Care 2011; 17:50-56.
