Effect of sniffing position on transesophageal echocardiography probe insertion: a randomized controlled trial

Transesophageal echocardiography (TEE) monitoring is essential in cardiac surgery, but it can cause several complications such as oropharyngeal injury. Although the sniffing position is a simple and widely used maneuver to facilitate tracheal intubation, its efficacy in TEE probe insertion remains unclear. In this study, we investigated the effect of the sniffing position on oropharyngeal injury and the ease of TEE probe insertion in patients undergoing cardiac surgery. In this prospective randomized controlled trial, 40 adult patients undergoing elective cardiac surgery were randomly assigned to either the conventional position group ( n = 20) or the sniffing position group ( n = 20). TEE probe insertion was performed by an experienced anesthesiologist using standard techniques. The primary outcome was the incidence of oropharyngeal injury, which was evaluated using a fiberoptic bronchoscope. Secondary outcomes included the first-attempt success rate, number of insertion attempts, resistance during advancement, and anatomical site of oropharyngeal injury. In this single-center trial of 40 patients, the incidence of fiberoptically detected oropharyngeal injury was significantly lower in the sniffing position group than in the conventional position group (5% vs. 45%; risk difference, -0.40; 95% CI, -0.61 to -0.13; p = 0.003). The first-attempt insertion success rate was significantly higher in the sniffing position group than in the conventional group (80% vs. 35%; risk difference, 0.45; 95% CI, 0.14 to 0.66; p = 0.004). The incidence of resistance during probe advancement was also significantly lower in the sniffing position group than in the conventional position group (20% vs. 60%; risk difference, -0.40; 95% CI, -0.62 to -0.10; p = 0.010). Posterior pharyngeal wall injury was the most common site of injury and occurred significantly less frequently in the sniffing position group (5% vs. 35%; risk difference, -0.30; 95% CI, -0.52 to -0.05; p = 0.044). In this single-center randomized trial of 40 patients, the sniffing position was associated with a lower incidence of fiberoptically detected oropharyngeal injury and a higher first-attempt TEE probe insertion success rate. The study was registered before patient enrollment at the Clinical Research Information Service of the Republic of Korea ( http://cris.nih.go.kr/ ) (registration date: July 2, 2020; reference no: KCT0005193).