New studies of respiratory-function monitoring show a continuing need for on-line ventilation, lung mechanics, pulmonary gas exchange, and peripheral oxygen delivery monitors. However, problems with today's monitors remain. These include measurement errors using pulse oximetry and end-tidal CO2, false positive or false negative alarms, and information overload for the care provider. These problems are now being addressed in current publications and literature reviews. Meanwhile, computerized workstations, intelligent alarms, and increasingly sophisticated on-line computerized data analysis provide a miniature pulmonary-function testing laboratory in the operating room. This means that a care provider now has a monitor that not only functions as a discriminating lead monitor, such as end-tidal CO2, but also a lead implication monitor, such as the sidestream spirometer. Indeed, the sophistication of the respiratory monitors now available enables the care provider to fully assess the adequacy of oxygen delivery to the patient from its entry into the airway, to the peripheral body tissues.