41 - Respiratory Monitoring

Abstract

Intraoperative respiratory monitoring is a fundamental component of the standards for basic anesthetic monitoring. Monitoring of oxygenation and ventilation is essential for the safe conduct of an anesthetic. Current approaches to respiratory monitoring primarily assess pulmonary mechanical and global gas exchange processes. The majority of respiratory monitors in clinical use provide information at the systemic and whole-lung level, from which inferences are made regarding the regional lung and tissue-level conditions. Monitoring of gas exchange, and its response to various interventions, may differentiate etiologies for hypoxemia. Pulse oximetry is a simple and noninvasive method for continuous monitoring of arterial oxygen saturation. Systems utilizing near infrared spectroscopy are used clinically to monitor regional tissue oxygenation, particularly in the brain. Capnography is the primary quantitative method to assess ventilation during surgery and in the perioperative period. Besides providing physiologic information on ventilation, pulmonary blood flow, and aerobic metabolism, capnography is important for the verifying endotracheal tube placement, and determining the integrity of the breathing circuit. End-tidal carbon dioxide (CO2) is not always a reliable approximation of arterial CO2 tension, especially in the presence ofsignificant heterogeneity in the distribution of ventilation and perfusion. Measurement of the pressures, flows, and volumes associated with ventilation is necessary to optimize mechanical ventilation, as well as to detect mechanical derangements of the respiratory system. Imaging techniques, such as ultrasonography and electrical impedance tomography, have also emerged as important tools for respiratory monitoring. The monitoring of tissue and subcellular respiration remains a desirable goal for future innovation.