The influence of respiration, neck flexion, and arterial segment on carotid artery longitudinal wall motion

Although carotid artery longitudinal wall motion (CALM) has been highly detailed in cross-sectional studies, there is little evi-dence to explain population interindividual variability. This study was conducted to investigate how common external factors impact CALM. Twenty-one young healthy adults (11 females, aged 22 +/- 2 yr) underwent three within-subject protocols. To evalu-ate probe positioning, vascular ultrasound was performed at a proximal and distal location along the common carotid artery. To evaluate neck angle, scans were acquired with the neck positioned at 70 degrees, 90 degrees, maximum extension (112 +/- 9 degrees), and maximum flex-ion (51 +/- 7 degrees). For the respiratory cycle condition, scans were taken during 7 s of inhalation, 7 s of exhalation, and 7 s of breath hold. CALM was evaluated for anterograde, retrograde, and maximum displacements, as well as radial-axial displacement. CALM was greater at proximal versus distal locations (retrograde = 1.14 +/- 0.62 vs. 0.63 +/- 0.24 mm, maximal = 1.32 +/- 0.59 vs. 0.73 +/- 0.24 mm; all P < 0.05). Minimum neck angles had greater motion than maximum angles (maximum displacement = 1.03 +/- 0.43 vs. 0.77 +/- 0.23 mm, P < 0.05). Without correcting breathing bias, retrograde displacement was greater during inspiration versus ex-piration (1.06 +/- 0.34 vs. 0.58 +/- 0.24 mm) and breath hold (1.06 +/- 0.34 vs. 0.58 +/- 0.24 mm), diastolic CALM was greater during expi-ration versus breath hold (1.10 +/- 0.44 vs. 0.76 +/- 0.33 mm), and maximum CALM was smaller during breath hold versus expiration (0.89 +/- 0.31 vs. 1.21 +/- 0.39 mm) and inspiration (0.89 +/- 0.31 vs. 1.41 +/- 0.70 mm). We recommend scanning 1-2 cm proximal to the carotid bifurcation, maintaining a neutral neck angle (70 degrees-90 degrees) for optimal CALM data collection in humans.NEW & NOTEWORTHY Carotid artery longitudinal wall motion (CALM) provides unique cardiovascular health information, yet a standardized approach to measurement is nonexistent. We tested CALM during manipulation of common external factors includ-ing probe position, neck angle, and breathing. All three conditions were found to alter CALM with drift in the breathing condition correctable by use of a linear bias correction. Consistent techniques should be used in CALM acquisition to reduce variability between individuals and population groups.

Automated summary

This study investigated the impact of external factors such as probe position, neck angle, and breathing on carotid artery longitudinal wall motion (CALM). The results showed that these factors do have an effect on CALM, and it is recommended to scan the carotid artery 1-2 cm proximal to the bifurcation and maintain a neck angle of 70°-90° for accurate data collection.