The the level of the fourth intercostal space

The central
venous pressure (CVP) is the pressure measured in the central veins located
near the heart. It designates right mean atrial pressure and is recurrently
used as a guesstimate of right ventricular preload. “The central venous
pressure does not measure blood volume truthfully, although it is often used to
estimate it. The central venous pressure value is determined by the pressure of
venous blood in the vena cava and by the function of the right heart, and it is
not only affected by intravascular volume and venous return, but also by venous
tone and intrathoracic pressure, along with right heart function and myocardial
compliance” (Department of Anaesthesiology The
University of Hong Kong, n.d.).

and over-distention of the venous collecting system can be recognized by
central venous pressure measurements before clinical signs and symptoms become evident.
Under normal occurrences an increased venous return results in an augmented
cardiac output, without significant changes in central venous pressure.
However, with poor right ventricular function, or an obstructed pulmonary
circulation, the right atrial pressure rises, therefore causing a subsequent
rise in measures central venous pressure. Comparably, it is possible for a
patient with hypovolemia to exhibit a central venous pressure reading in the
normal range due to loss of blood volume or widespread vasodilation which will
result in reduced venous return and a fall in right atrial pressure and central
venous pressure” (Richard E. Klabunde, 2014).

“The central venous pressure can be
measured either manually using a manometer or electronically using a
transducer. In either case the central venous pressured must be zeroed at the
level of the right atrium. This is usually the level of the fourth intercostal
space in the mid-axillary line while the patient is lying in a supine position.
Each measurement of central venous pressure should be taken at this same zero
position. Trends in the sequential measurement of central venous pressure are
much more informative than single readings. However, if the central venous
pressure is measured at a different level each time then this renders the trend
in measurement inaccurate” (Department
of Anaesthesiology The University of Hong Kong, n.d.).

Pulmonary Artery Pressure.

Pulmonary artery pressure (PA pressure) is a measurement of blood pressure found in the pulmonary artery of the heart. “Pulmonary artery pressure is generated by
the right ventricle expelling blood into the pulmonary circulation, which acts
as an opposition to the production from the right ventricle. With each ejection
of blood during ventricular systole, the pulmonary arterial blood volume
increases, which stretches the wall of the artery. As the heart relaxes also
known as ventricular diastole, blood continues to flow from the pulmonary
artery into the pulmonary circulation. The smaller arteries and arterioles
serve as the chief resistance vessels, and through changes in their diameter,
regulate pulmonary vascular resistance” (Richard E. Klabunde, The
Pharmacologic Treatment of Pulmonary Hypertension, 2010).

Today, pulmonary
artery catheters are placed on a case by case basis taking into consideration
the patient’s condition and the staff qualification. Conditions for using a pulmonary
catheter include severe cardiogenic pulmonary edema, patients with acute
respiratory distress syndrome who are not hemodynamically stable, patients who
have had major thoracic surgery, and patients with septic or sever cardiogenic
shock.  “A pulmonary artery
pressure monitoring system uses a sensor to measure your pulmonary artery
pressure and heart rate. The sensor is small, comparable to the size of a penny
with two thin loops at each of the ends. The sensor is implanted in the
pulmonary artery of the heart. Normally you will not feel the sensor, and it
will not impede with your day to day activities or other devices that may be
implanted such as a pacemaker or defibrillator” (Abbott, n.d.).

Pulmonary Capillary Wedge Pressure.

Pulmonary capillary wedge pressure provides an estimation of left atrial
pressure. Left atrial pressure can be measured by insertion of a catheter into
the right atrium then piercing through the interatrial septum, however, for apparent
reasons, this is not usually accomplished because of the destruction to the
septum and potential detriment to the patient. “It is helpful to measure pulmonary capillary wedge pressure to
diagnose the severity of left ventricular
failure and to calculate the
degree of mitral valve stenosis. Both
conditions raise left atrial pressure and therefore raise pulmonary capillary
wedge pressure.
Aortic valve stenosis and regurgitation, and mitral
regurgitation also elevate left
atrial pressure. When these pressures are above twenty millimeters of mercury,
pulmonary edema is probable to transpire, which is life threatening to the