Page 330 - Clinical Application of Mechanical Ventilation

296 Chapter 10

Pulse contour analysis is not entirely noninvasive because an arterial catheter
Pulse contour is required, and some systems also require a central venous catheter. There are a
analysis uses the arterial
pressure waveform, arte- number of monitoring systems based on pulse contour analysis. Since the arterial
rial vascular resistance and pressure waveform varies with changes in arterial compliance, patient condition,
patient data to calculate the
stroke volume and cardiac and medications, the systems must be calibrated with another reference standard.
output. Two common reference standards are lithium dilution (Pittman et al., 2005) and
transpulmonary thermodilution (Della et al., 2002).
The Lithium Dilution Cardiac Output (LiDCO) system uses a peripheral venous
catheter into which lithium chloride is injected and then the lithium concentration
is measured at the arterial catheter. The Pulse Contour Cardiac Output (PiCCO)
system uses a combination of the transpulmonary thermodilution technique and ar-
terial pulse contour analysis. Transpulmonary thermodilution is done by injecting a
cold saline solution into a central venous line and then the temperature is measured
at the arterial side (typically via a femoral artery line).
In both LiDCO and PiCCO systems the cardiac output measurement needs to be
repeated on a regular basis and in the occurrence of any changes in patient condi-
tion or fluid and vasoactive drug administration.
The FLOTRAC system does not require calibration with some other method of
measuring cardiac output, but it uses a transducer attached to the patient’s periph-
eral arterial line and interfaced with a special monitor (Vigileo) to measure pulse
pressure. It also uses customized patient data and algorithms to account for changes
in arterial compliance and resistance. The data are updated every 20 seconds and
displayed as a continuous value. This system does not require a central venous line
but there is a specially adapted fiberoptic CVP (PreSep) line which can interface
with the same Vigileo monitor to provide central venous oxygen saturation data
#
(SvO ) to complement the continuous cardiac output data.
2

NONINVASIVE HEMODYNAMIC MONITORING

There are three major types of noninvasive hemodynamic monitoring methods:
#
transesophageal echocardiography, carbon dioxide elimination (VCO ), and im-
2
pedance cardiography (ICG). Following is a discussion of each technology.

Transesophageal Echocardiography

Transesophageal echocardiography provides diagnosis and monitoring of many
transesophageal echocardiog-
raphy: A method using a Doppler structural and functional abnormalities of the heart. It can also be used to calculate
transducer in the esophagus for an cardiac output from measurement of blood flow velocity by recording the Dop-
indirect measurement of the blood
flow velocity in the descending pler shift of ultrasound. The time velocity integral obtained for the blood flow in
aorta and the calculation of the the left ventricular outflow tract (e.g., descending aorta) is multiplied by the cross-
cardiac output and other hemody-
namic data. sectional area and the heart rate to yield the cardiac output. This Doppler technique
requires a highly skilled technician to obtain accurate readings (Mark et al., 1986).
The transesophageal echocardiography procedure may be done at the bedside, and
continuous readings are available with this procedure. A Doppler transducer probe

Copyright 2013 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.