American journal of critical care : an official publication, American Association of Critical-Care Nurses
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Comparative Study
Echocardiographic determination of valid zero reference levels in supine and lateral positions.
The phlebostatic axis--the junction of the fourth intercostal space and the midpoint of the anterior-posterior diameter--has been accepted as a reliable external reference point for the mid-right and mid-left atrium. Acceptance of this reference point is based upon research conducted in 1945 that measured venous pressures in the hands of subjects positioned with the head of the bed raised to different levels. The validity of this reference point for intracardiac pressure measurements in supine or laterally positioned patients has not been established. ⋯ We analyzed the data of 25 normal, healthy subjects. The study findings show that the phlebostatic axis is a valid reference point for the right atrium, and the phlebostatic axis and midanterior-posterior diameter are valid reference points for the left atrium in the supine position. However, neither is a valid external reference point in the lateral positions. Pressure measurements obtained when patients are in the lateral positions are not accurate. There remains a need to develop valid methods of accurate pressure measurements in various body positions.
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To investigate the effects of four nonneutral neck positions on intracranial pressure. ⋯ These data support previous studies that indicated that a patient at risk for pathological increase in intracranial pressure should not be positioned with the neck in flexion or the head turned to either side.