To evaluate the role and effectiveness of hybrid contrast-enhanced ultrasound imaging technology in positioning indwelling nasointestinal tube in critically ill patients.

Thirty-two critically ill patients who had a nasointestinal tube indwelled were collected from May 1, 2018 to July 1, 2018 in the Intensive Care Unit of Zhejiang Provincial People's Hospital. In these patients, rough anatomical location of the esophagus, stomach, and duodenum was detected by conventional ultrasound and ultrasonic anatomy locating method to ensure that the nasointestinal tube was in the digestive tract. A microbubble ultrasound contrast agent and an oral ultrasound contrast agent were mixed and injected into the nasointestinal tube, and then the tube direction and end position were observed and recorded in real time. The optimal preparation of hybrid ultrasound contrast agent was determined by an in vitro experiment. Using the abdominal X-ray as the gold standard and the tube placed beyond the pylorus as a success marker, the successful positioning rate and the effectiveness of the hybrid contrast-enhanced ultrasound method for verifying the nasointestinal tube beyond the pylorus were assessed.

The results of the in vitro experiment showed that the hybrid ultrasound contrast agent containing the microbubble ultrasound contrast agent and oral ultrasound contrast agent mixed at a ratio of 1:1000 to 1:500 had optimal and stable ultrasound imaging effects. It was prepared at a ratio of 1:1000 and 1:500 for patients with body mass index (BMI)<28 and BMI≥28, respectively. Nasointestinal tubes were successfully positioned by the hybrid contrast-enhanced ultrasound imaging technology in 93.8% (30/32) of the patients, including success at one attempt in 24 cases [time required: (1.71±0.65) minutes] and success after multiple attempts in 6 [time required: (4.42±0.93) minutes], of whom 5 had the tube placed beyond the pylorus and 1 had the tube bent in the stomach. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the hybrid contrast-enhanced ultrasound imaging technology for nasointestinal tube positioning were 93.5%, 100.0%, 100.0%, 33.3%, and 93.8%, respectively. There were no obvious complications in all patients.

The hybrid contrast-enhanced ultrasound imaging technology has the advantages of both the microbubble ultrasound contrast agent and oral ultrasound contrast agent, and can position the direction and end of nasointestinal tube in critically ill patients quickly and accurately.