During placement of a pulmonary artery catheter, what does a consistent fluctuation in pressure from 0 mmHg to 25 mmHg indicate?

When a pulmonary artery catheter is placed, a consistent fluctuation in pressure readings from 0 mmHg to 25 mmHg suggests that the catheter is positioned within the right ventricle. This fluctuation occurs because the right ventricle experiences changes in pressure with each heartbeat, reflecting the dynamics of ventricular filling and contraction.

The right ventricle's pressures are significantly lower than the pressures found in the pulmonary artery and the left atrium, creating a distinctive pattern when the catheter is in this location. This alternating pressure is due to the mechanical motion of the heart, which is not static and varies as the heart contracts and relaxes.

If the catheter were in the pulmonary artery, one would expect more stable pressures that align with the higher pressure typical of pulmonary circulation. A blocked catheter would demonstrate constant low pressure readings or difficulty in obtaining any pressure. Lastly, if the catheter were in the left atrium, the pressures would be low and stable, aligning more closely with left atrial pressures that do not fluctuate significantly like those in the right ventricle. Thus, the fluctuating pressures from 0 mmHg to 25 mmHg distinctly indicate that the catheter is in the right ventricle.