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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Respiratory failure related to neuromuscular weakness has commonly been managed with long-term ventilation by tracheostomy. Currently, nasal positive pressure ventilation is being used with success in this patient population. It has been suggested that initiation of nasal positive pressure ventilation is best done in an intensive care setting. ⋯ Following the initiation of nasal positive pressure ventilation, this group of patients experienced near normalization of daytime measurements of partial pressure of arterial carbon dioxide, reported increases in daytime energy levels, and relief of nighttime signs and symptoms. These objectives were accomplished with no significant complications. Use of this protocol may also decrease length and cost of hospitalization and improve patient acceptance of noninvasive ventilatory assistance.
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To determine fluctuation in mixed venous oxygen saturation in critically ill medical patients during a period of rest. ⋯ Knowledge of normal fluctuation enables the care giver to evaluate changes in mixed venous oxygen saturation in response to activities and/or treatments. Additional study of fluctuation in homogenous groups of critically ill patients is warranted.