Arterial lines are essential tools in managing critically ill patients, but it is frustrating when they are not working as expected. It can be hard to tell when an unexpected waveform or pressure reflects the patient's physiology versus a problem with the line. Recognizing common issues and systematic troubleshooting will optimize your hemodynamic monitoring.

Types of arterial line problems

• Overdamping (most common): Flattened waveform
  • Underestimates systolic | overestimates diastolic | typically does not affect MAP
  • Look for: air bubbles, clots, kinked tubing, malposition, or a low pressure bag (<300 mmHg)
• Underdamping: Peaky waveform with "ringing" oscillations and loss of dicrotic notch
  • Overestimates systolic | underestimates diastolic | typically does not affect MAP
  • Look for excessive tubing length
• System issues:
  • Zeroing errors
  • Transducer is not at the level of the right atrium > 4th intercostal space, mid-axillary line (phlebostatic axis)

Troubleshooting Steps

1. Correlate with Non-Invasive BP - MAPs should be within ~10 mmHg. Discrepancies suggest one of the numbers may be inaccurate. Make sure the cuff is the correct size!
2. Verify Transducer Position - Level transducer at the 4th intercostal space, mid-axillary line. For each 10 cm off there is about 8 mmHg of pressure inaccuracy.
3. Inspect Tubing and Pressure Bag
   • Ensure no kinks
   • Make sure the pressure bag is inflated to 300 mmHg
   • Flush vigorously to clear bubbles
4. Check for Clots (radial lines):  Use ultrasound with Doppler to visualize flow and detect perica­theter clots. Reduce insonation angle (<60°) for optimal signal. “Positional” lines may have a clot around it, and the line only works well when it’s “hubbed” or the wrist is flexed.
5. Consider exchanging the line over a micropuncture wire - it's more sterile and safest to place another line, but when access is tough/limited, it's not unreasonable to exchange a 4.45 cm 20g radial catheter for a 12 cm 20g catheter over a micropuncture wire with sterile technique.

By following these steps, you can systematically identify whether waveform or pressure abnormalities are due to technical issues or true patient physiology.

References

1. Weingart S. EMCrit 210.1 – Arterial Lines (Part 1). EMCrit Blog. Published on October 16, 2017. Available at: https://emcrit.org/emcrit/arterial-lines/. 
2. Rezaie S. Damping and Arterial Lines. REBEL EM. July 4, 2022. Available at: https://rebelem.com/damping-and-arterial-lines/.
3. Yartsev A. Arterial Line Dynamic Response Testing. Deranged Phsyiology.  Available at: https://derangedphysiology.com/main/cicm-primary-exam/required-reading/cardiovascular-system/Chapter%20759/arterial-line-dynamic-response-testing. 
4. Yartsev A. Normal Arterial Line Waveforms. Deranged Physiology. Available at: https://derangedphysiology.com/main/cicm-primary-exam/required-reading/cardiovascular-system/Chapter%20760/normal-arterial-line-waveforms.