Where is the left ventricle during cardiopulmonary resuscitation based on chest computed tomography in the expiration with arms down position?

<div><p>Objective</p><p>Patients usually receive cardiopulmonary resuscitation during ventilatory expiration and with their arms down, which does not reflect the normal imaging position. This study used scout images from low-dose chest computed tomography to compare the locations of the left ventricle (LV) in the expiration with arms down position (EAD) and in the full inspirational with arms raised position (IAR).</p><p>Methods</p><p>This cross-sectional study used a convenience sample and evaluated scout images that were obtained during screening with the participants in the EAD and IAR positions. The effective compression point was defined as being on the sternum above the longest anteroposterior diameter (APD) of the LV (using axial computed tomography images). The sternum was divided into three parts and the heart’s position was evaluated on the EAD and the IAR images, and the distance from the xiphoid process to the LV’s sternum landmark (XLVD) was measured. We also examined the compressible organs during CPR based on the EAD and IAR images.</p><p>Results</p><p>We enrolled 127 participants. The LVs were located in the middle of the sternum at EAD for 117 participants (92%) and in the lower half of the sternum at IAR for 107 participants (84%). The mean XLVD was significantly different between the EAD and IAR positions (mean: 85 ± 21 mm vs. 33 ± 17 mm, respectively). The liver’s left lobe was located in the lower half of the sternum at EAD for 118 participants (93%).</p><p>Conclusions</p><p>These findings indicate that the location of the LV during cardiopulmonary resuscitation might be in the middle of the sternum if the patient is treated in the EAD position.</p></div

Comparing distances from the xiphoid process to the sternum landmark according to respiratory phase and arm position.

<p>Comparing distances from the xiphoid process to the sternum landmark according to respiratory phase and arm position.</p

Participant characteristics.

<p>Participant characteristics.</p

The distance from the xiphoid process to the point of the left ventricle’s maximal anteroposterior diameter of the left ventricle.

<p>The perpendicular line between the point for the left ventricle (LV)’s maximal anteroposterior diameter (APD) and the xiphoid process marker was measured in the expiration with the arms down position and the inspiration with the arms raised position (XLVD) (a,b). From the upper side of the sternum, the 1/4 and 2/4 sections were defined as the upper half of the sternum, the 2/4 and 3/4 sections were defined as the middle of the sternum, and the 3/4 and 4/4 sections were defined as the lower half of the sternum, relative to the positions of the heart and liver (c,d). In the expiration with the arms down position, the land marks of LV at sternum were located beneath the middle of the sternum, and the liver was located beneath the lower half of the sternum. In the inspiration with the arms raised position, the land marks of LV at sternum were located beneath the lower half of the sternum.</p

Determining maximal anteroposterior diameter (APD) of the left ventricle (LV) using axial and scout images.

<p>The skin above the maximal APD was searched to identify the sternum landmark representing the LV. </p><p></p><p></p><p>The maximal APD of the LV was measured and aligned in the axial images from the full inspiration with the arms raised position. The centre of the line was defined as the location of the LV (a).</p><p></p><p></p><p>The location of the LV was marked at the skin and a perpendicular line was drawn to the sternum for the sternum landmark of the LV.</p><p></p><p></p><p>A perpendicular line was drawn at the margin of the right atrial contour, and the intersection between the perpendicular line and the right atrial contour was marked.</p><p></p><p></p><p>A straight line was drawn from the heart’s apex to the intersection point at the right atrial contour.</p><p></p><p></p><p>Another perpendicular line was drawn from the radio-opaque marker at the lowest palpable xiphoid process to the line that connected the apex and intersection point. This intersection was defined as the LV sternum landmark for the expiration with the arms down position, and the distance from the sternum landmark to the xiphoid process marker was defined as the XLVD. This method was also applied to the expiration with the arms down position scout images.</p><p></p><p></p><p></p> <p>The maximal APD of the LV was measured and aligned in the axial images from the full inspiration with the arms raised position. The centre of the line was defined as the location of the LV (a).</p> <p>The location of the LV was marked at the skin and a perpendicular line was drawn to the sternum for the sternum landmark of the LV.</p> <p>A perpendicular line was drawn at the margin of the right atrial contour, and the intersection between the perpendicular line and the right atrial contour was marked.</p> <p>A straight line was drawn from the heart’s apex to the intersection point at the right atrial contour.</p> <p>Another perpendicular line was drawn from the radio-opaque marker at the lowest palpable xiphoid process to the line that connected the apex and intersection point. This intersection was defined as the LV sternum landmark for the expiration with the arms down position, and the distance from the sternum landmark to the xiphoid process marker was defined as the XLVD. This method was also applied to the expiration with the arms down position scout images.</p

Distances from the arbitrary sternum left ventricle (LV) landmark to the actual landmark using axial images from full inspiration.

<p>The measured LV landmark was approximately 1.23 mm lower on the sternum, compared to the actual landmark (median: –1.23 mm, interquartile range: –15.58 mm, 10.56 mm, range: –19.35 mm, 14.52 mm).</p

Univariable and multivariable analysis of factors associated with the location of the heart according to expiration and inspiration.

<p>Univariable and multivariable analysis of factors associated with the location of the heart according to expiration and inspiration.</p

Locations of the heart and liver according to the three sternum divisions.

<p>Locations of the heart and liver according to the three sternum divisions.</p

The incidence of VTE according to clinical parameters.

*<p>Fisher's exact test, ^†linear-by-linear association.</p>‡<p>Subtotal gastrectomy was conducted in 271 patients and proximal gastrectomy in 11 patients.</p><p>Abbreviations: VTE, venous thromboembolism; BMI, body mass index; WBC, white bleed cell.</p

Flow of patients in this study.

<p>Flow of patients in this study.</p