Visual detection of pulselessness by carotid artery sonography - A prospective observational study among medical students.

Aim: This cross-sectional study aimed to determine whether medical students with little to no ultrasound experience could correctly distinguish between 'pulsation present' and 'no pulsation present' after a short introductory video on the subject using ultrasound videos of the common carotid artery (CCA).

Methods: Ultrasound videos (B-mode, M-mode, and Color Doppler) of pulsatile (systolic blood pressure 70-80 mmHg) and non-pulsatile (cardiopulmonary bypass surgery, clamped aorta) CCA were created. These were demonstrated to the medical students for a period of ten seconds - corresponding to the duration of the manual pulse palpation during cardiopulmonary resuscitation (CPR). All participants viewed twenty of these videos in random order on a tablet and were asked to decide whether or not a CCA pulse was present.

Results: 432 participants completed the study in full on 20 cases, enabling a total of 8640 decisions on CCA pulse 'present' or 'not present' to be evaluated. M-mode: in 96 % (1244/1296) of the cases, the participants correctly identified the presence of pulsatile CCA. In the videos without pulsatile CCA, the correct decision 'no pulsation present' was made in 95 % (1231/1296) of the cases. B-mode: the decision 'pulsation present' was made correctly in 69 % (889/1296) of the cases, and in the remaining 31 % (407/1296) the option 'no pulsation present' was incorrectly chosen, although a video with CCA pulsation was shown. In contrast, the correct decision 'no pulsation present' was selected in 99 % of the cases (2142/2160). Color Doppler: CCA pulsation was correctly detected in 99.5 % (1290/1296) of the cases. In the videos without CCA pulsation, 99 % (1281/1296) of the videos were correctly evaluated as 'no pulsation present'.

Conclusion: Medical students seem to be able to detect the absence of a pulse with a high degree of accuracy using 2D ultrasound of the CCA in a controlled study setting, using different ultrasound modes. The results of this study suggest that a combination of Color Doppler and B-mode may be useful when evaluating the CCA during CPR to answer the question 'pulsation present' or 'no pulsation present'.