Hypoxia and Ventilator Asynchronies

Abstract

Acute hypoxia is commonly present in critically ill patients. There are five pathophysiological mechanisms of hypoxia. In critically ill patients, V/Q mismatch and shunt are the most common pathophysiological mechanisms of hypoxia distinguished from each other by their response to oxygen. In a mechanically ventilated patient, acute hypoxia may be attributed to equipment failure, endotracheal tube issues, or patient-related problems. The initial etiological approach is based on clinical examination and imaging tests—mainly lung ultrasound. In this chapter, we discuss the main causes, the diagnostic approach, and the management of acute hypoxia in critically ill mechanically ventilated patients. Patient-ventilator asynchronies, which may worsen patients’ outcomes, are common and may be present in all three phases of a mechanical breath: the triggering, the pressure delivery, and the cycling-off phase. Inspecting ventilator screen waveforms is a valuable tool for recognizing the different forms of patient-ventilator asynchronies. To master pattern recognition from ventilator screens takes time, but this chapter provides a sound theoretical ground for mastering this difficult and important part of intensive care.