To Örebro University

Pulmonary aspiration is a feared complication in anesthesia practice. Even if it is a rare event it is the most common cause of anesthesia related death. There are two different types of pulmonary aspiration, macroaspirationwhere large amounts of gastric content are inhaled to the lungs, and the silent, often unnoticed, microaspiration, where small amounts of gastric or oropharyngeal contents are aspirated. Micro aspirations is much more common and can occur at any time during the perioperative period, presenting as postoperative pulmonary complications, often several days after the anesthesia procedure. 

Human physiology features multiple mechanisms of protection against pulmonary aspiration, including the esophageal sphincters that prevent gastric regurgitation and complex laryngeal reflex systems protecting the airway. An additional vital defense against pulmonary aspiration is an intact swallowing function, with dysphagia being the primary cause of aspiration pneumonia. Anesthetic agents affect these protective mechanisms to various extent.

The aim of this thesis was to study the effects of sedative agents on swallowing function, and different ventilatory techniques during anesthesia induction in healthy volunteers. In study I, the use of positive end expiratory pressure during mask ventilation after anesthesia induction was studied in regard of risk of gastric insufflation. In study II and IV the pharmacological effects of the opioid remifentanil on swallowing function were studied. Study III was the first study on effects of dexmedetomidine on human swallowing physiology. The experiments in this thesis has led to a deeper understanding in how different anesthetic agents affects the physiological protective mechanisms against pulmonary aspiration, both during anesthesia induction and sedation. The findings may facilitate clinical decisions, leading to better risk management in terms of macroaspiration during anesthesia and sedation, and postoperative pulmonary complications related to microaspirations.