Prolonged imaging time in the salivagram appears unnecessary for detecting aspiration

The salivagram was first described to detect possible lung aspiration in infants or young children. Its original protocol required dynamic imaging for 60 minutes, which has high sensitivity. The purpose of this retrospective investigation was to determine whether a shortened period of image acquisition can be adopted without significantly reducing the sensitivity of the test in detecting aspiration.

The current salivagram protocol in our hospital requires 60 minutes of dynamic imaging. The images of a total of 398 patients (ages 1 month to 9 years old) with positive salivagrams were analyzed. The entire 60-minute dynamic images were divided into 6 periods, 10 minutes/period. The time of the onset of abnormal activity in the bronchi, which was evidence of aspiration in each patient, was recorded and assigned to the corresponding period.

Among all 398 patients with evidence of aspiration, tracheobronchial tree activity could be seen in the first 10 minutes of the dynamic imaging in 184 of them (46.2%, 184/398). The onset of the bronchial activity was seen between 10 and 20 minutes in 177 patients (44.5%, 177/398). A total of 35 patients (8.8%, 35/398) had the onset of abnormal tracheobronchial tree activity in the 3rd period between 20 and 30 minutes. During the 4^th period between 30 and 40 minutes, the onset of the aspiration occurred in only 2 patients (0.5%, 2/398). All patients had the onset of aspiration in the first 40 minutes of the dynamic imaging.

The originally described 60-minute dynamic imaging protocol of the salivagram can be safely shortened to 40 or even 30 minutes without a significantly decreased chance of detecting aspiration. Prolonged imaging is unnecessary.