1 – 4 This impairment may lead to adverse respiratory events like aspiration pneumonia or retained secretions. However, residual concentration of anaesthetics and residual sedation observed after general anaesthesia may depress this reflex. It protects the lungs from inhalation of foreign particles and clears the airways of retained secretions. This study indicates that residual sedation after propofol anaesthesia for colonoscopy does not adversely affect the cough reflex.Ĭough reflex is the main mechanism of airway defence. However, light sedation was observed with propofol concentrations of 1.2 and 0.9 µg ml −1.Ĭonclusion. Log C1 was measured before anaesthesia and during the recovery period with estimated decreasing propofol concentrations of 1.2, 0.9, 0.6, and 0.3 µg ml −1. C1 was log transformed for statistical analysis (Log C1). The citric acid concentration eliciting one cough (C1) was defined as the cough reflex threshold. Increasing concentrations of nebulized citric acid (2.5, 5, 10, 20, 40, 80, 160, 320, and 640 mg ml −1) were delivered during inspiration until a cough was evoked. Cough reflex threshold was measured with citric acid. Anaesthesia was induced and maintained with a blood target-controlled propofol infusion. Fifteen, ASA I–II, non-smoking patients undergoing elective colonoscopy were studied. The objective of this study was to investigate the effect of low concentrations of propofol on the cough reflex sensitivity as assessed by the cough reflex threshold to an inhaled irritant. It is unknown whether low concentrations of propofol alter the cough reflex in the early period after anaesthesia. Dysfunction of the cough reflex as a result of the lingering effects of anaesthetics may lead to aspiration pneumonia or retained secretions after general anaesthesia.