Page 496 - Cardiac Nursing

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472 P A R T III / Assessment of Heart Disease
available (Fig. 21-11). The thermodilution catheter is 7.5 Fr in di-
ameter and 110 cm long and is marked in 10-cm increments. The
balloon is inflated with a maximum of 1.5 mL of air.
Insertion of the PA Catheter
The catheter is inserted percutaneously. Once the RA is reached,
the balloon, located on the distal end of the catheter, is inflated
A
and the catheter is “floated” through the RA and RV and out into
the PA, where it occludes a branch of the PA. After the character-
istic PAOP tracing has been obtained, the balloon is deflated, al-
lowing the catheter to recoil slightly into the PA. The catheter is
left in the balloon-down position to prevent pulmonary infarc-
tion. The nursing responsibilities during insertion of the PA
catheter are summarized in Display 21-5.
PA Waveform Characteristics
30
20
As the catheter passes through the heart, three pressure waveforms
10 can be visualized using a PA catheter: RA, PA, and PAOP (Fig.
2
2
0 21-12A).
B
PA Pressure
PA pressures provide an index of the pressure within the pul-
monary vasculature and are affected by compliance of the LV, pul-
monary vascular pressure, CO, and the state of the lung tissue. In
individuals without preexisting cardiopulmonary disease, PA pres-
sure increases slightly with age (older than 60 years, PA mean
16 3 mm Hg; younger than 60 years, PA mean 12
2 mm Hg). 172 Similarly, in individuals with hypertension without
60 60 other cardiac disease there is also an age-related increase in PA
pressures (aged less than 45 years, PA mean 17 5 mm Hg;
40 40
aged 45 to 64 years, PA mean 18 6 mm Hg, and aged greater
20 20
than or equal to 65 years, PA mean 21 8 mm Hg). 173
0 0
C Three PA pressures are measured: systolic, diastolic, and mean.
The PA systolic (PAS) pressure reflects the flow of blood into the PA
■ Figure 21-10 Pericardial tamponade in a spontaneously breath-
ing patient. (A) Arterial waveform. Note the electrical alternans, al- from the RV. In the absence of elevated pulmonary vascular pressure
ternating height or duration of the QRS complex, and pulsus para- or RV outflow obstruction, PAS pressure is equal to RV systolic
doxus on the arterial waveform. (B) RAP 20 mm Hg. (C) PA to pressure. The PAS is affected by PA compliance and RV ejection.
PAOP. PAS pressure 26 mm Hg; PAEDP 17 mm Hg; PA mean During diastole, the mitral valve is open, and a continuous column
pressure 19 mm Hg; PAOP 20 mm Hg. Equalization of the di- of blood from the PA to the LA and LV exists; therefore, the pres-
astolic pressures is the result of circumferential compression of all car- sure just before contraction (end-diastole) is approximately equal in
diac chambers. the PA, LA, and LV. As a result of the diastolic equalization, the
PA end-diastolic pressure (PAEDP) is often used as an indirect in-
dicator of PAOP and LV end-diastolic pressure (LVEDP). The
difference between the RV end-diastolic pressure and PAEDP (an
who may benefit from the use of a PA catheter to guide and eval- increase in the diastolic pressure as the catheter passes across the
uate therapy (Display 21-4). pulmonic valve) is an important characteristic in determining
With the decreased use of PA catheters, one of the challenges for whether the catheter tip is correctly positioned in the PA or has
clinicians will be to maintain clinical proficiency in the use of PA flipped back into the right ventricle (Fig. 21-12A).
2
2
catheters and the hemodynamic data obtained (e.g., CO, ). The
Pulmonary Artery Catheter Education Program (www.PACEP.org) Pulmonary Artery Occlusion Pressure
and the American Thoracic Society Pulmonary Artery Catheter The PAOP is obtained by inflation of the balloon on the distal
Primer are excellent resources for standardized education. 170,171 end of the PA catheter, which allows the catheter to float forward
Consideration should also be given to the creation of a team of nurses to occlude a segment of the PA. The occluded catheter creates a
who provide care to patients requiring PA catheterization. static column of blood through the pulmonary vasculature (Fig.
21-12B). This static column acts as an extension of the fluid
Description of the PA Catheter within the catheter system and allows retrograde transmission of
left heart pressures to the distal port of the catheter.
The PA catheter is a multilumen, polyvinylchloride catheter with There is, in general, a good relationship between the mean
a variable external diameter. Many models of PA catheters are PAOP and mean LAP. At end-diastole, pressure equalizes between