Monitoring the respiratory system of the mechanically ventilated patient.

Bedside monitoring of respiratory status is designed to measure specific parameters and alert the clinician when these parameters exceed the limits of a desired range. Parameters should include measures of respiratory mechanics, oxygenation, and ventilation. Monitoring is the only form of communication between the physician and a patient receiving neuromuscular blocking agents. Airway pressure tracing alone, or in conjunction with concurrent flow, measures respiratory system mechanics, resistance, compliance, and the work of breathing. Pulse oximetry reflects oxygenation, while mixed venous oximetry indicates the balance between oxygen supply and demand. Capnography is a noninvasive way of assessing ventilation. Taken as a whole, noninvasive monitoring provides useful information, reflecting trends in oxygenation, ventilation, and mechanics. This article reviews the concepts of noninvasive monitoring of critically ill patients. Emphasis is given to the patient receiving neuromuscular blocking agents.