6 Hemodynamic Monitoring Techniques Free Online FlashCards

How is cardiac output calculated?

Cardiac output is the volume of blood pumped per minute: $CO = \text{heart rate} \times \text{stroke volume}$.

What does preload describe, and what is one key limitation of pressure estimates?

Preload is myocardial filling and stretch before contraction. CVP and PAWP provide context but are affected by other factors and are not stand-alone measures of blood volume or fluid responsiveness.

How is mean arterial pressure commonly approximated?

At a usual heart rate, a common approximation is $MAP \approx \frac{SBP + 2 \times DBP}{3}$.

How can an incorrectly sized blood-pressure cuff bias a reading?

A cuff that is too small can read falsely high; one that is too large can read falsely low.

What can ECG show, and what can it not confirm about circulation?

ECG displays electrical activity and heart rate, but it does not measure cardiac output or confirm that a pulse is producing adequate blood flow.

What can compromise pulse-oximeter accuracy?

Motion, poor peripheral perfusion, cold skin, nail products, and skin pigmentation can affect pulse-oximeter accuracy. Assess the signal and patient rather than relying on SpO₂ alone.

What can affect Doppler estimates of cardiac output?

Doppler measurements can estimate stroke volume and cardiac output, but image quality, operator technique, and calculation assumptions affect the results.

How does transducer height affect arterial pressure readings?

A transducer positioned too low reads falsely high; one positioned too high reads falsely low. Level it at the protocol-specified reference point and re-level after repositioning.

What does zeroing a pressure transducer establish?

Zeroing sets the transducer reference to atmospheric pressure as required by the system and local protocol.

How do overdamping and underdamping distort an arterial waveform?

An overdamped system may underestimate systolic and overestimate diastolic pressure. An underdamped system may exaggerate systolic pressure and produce ringing.

Why can’t a single CVP value establish fluid responsiveness?

CVP is influenced by right-heart function, venous return, intrathoracic and intra-abdominal pressure, and ventilator settings; one value does not reliably establish volume or fluid responsiveness.

What can a pulmonary artery catheter measure, and what does PAWP not directly measure?

A PAC can measure right-atrial and pulmonary artery pressures and mixed venous oxygen saturation, and can estimate cardiac output by thermodilution. PAWP helps assess left-sided filling pressure in context but is not a direct LV end-diastolic pressure measurement.