Understanding Arterial Pressure Tracing in ICU

Introduction

• Importance of arterial lines in ICU for guiding therapies.
• Arterial lines provide more than numerical values; they give pressure tracings.
• Eddie Watson provides lessons on critical care to make complex topics easy.

Basics of Arterial Pressure Tracing

• Systolic Upstroke: Large rapid upward tracing, marking the start of systole as the aortic valve opens.
• Peak Systolic Pressure: Highest point, corresponds to systolic BP (SBP).
• Systolic Decline: Downward movement with heart still in systole.
• Dichrotic Notch: Indicates aortic valve closure, end of systole.
• Diastolic Runoff: Pressure equalizing after systole, leads to diastolic BP (DBP).
• Pulse Pressure: Difference between peak systolic and minimum diastolic pressure.
• Mean Arterial Pressure (MAP): Average pressure, area under waveform.

Advanced Analysis

• Contractility: Slope of systolic upstroke.
• Stroke Volume: Area under systolic curve.
• Cardiac Output: Stroke volume multiplied by heart rate.
• Vascular Resistance: Slope of diastolic runoff.

ECG Alignment

• QRS complex occurs before systolic upstroke.
• ECG measures electrical impulse; contraction follows after 180ms delay from R wave.

Distal Pulse Amplification

• More distal readings show higher peak systolic pressure due to pressure wave reflection.
• Two pressure waves: forward flow and rebound pressure wave.
• Augmentation varies depending on arterial line location.

Abnormal Pressure Tracings

Damping

• Damping: Reduction of pressure tracing energy.
• Over-damped: Excessive damping, false low SBP, potentially high DBP, narrower pulse pressure.
• Under-damped: Less damping, false high SBP, low DBP, larger pulse pressure.

Square Wave Test

• Purpose: Check damping of arterial line.
• Procedure: Activate flush to test system response.
• Outcomes:
  • Optimally Damped: 1-2 oscillations.
  • Over-damped: Flatter wave, slow up/downstroke, no oscillation.
  • Under-damped: Exaggerated oscillations.

Conclusion

• Understanding pressure tracing is crucial for accurate readings in critical care.
• Damping concepts can be confusing; square wave test aids in ensuring accuracy.
• Encouragement to engage with ICU Advantage content for further learning.