What does this waveform represent? 

• The peak of the arterial waveform: Maximum systolic pressure
• The down-sloping: Decrease in arterial pressure throughout the systolic phase which is followed by the Dicrotic Notch
• Dicrotic notch: Closing of the aortic valve.
• Remainder of the down-sloping: Diastolic runoff while the aortic valve is closed

The farther away the arterial access point is from the heart the farther down the dicrotic notch will be on the waveform.  

Troubleshooting: It is important to recognize when the waveform is not reading appropriately. A couple solutions if your waveform is reading inappropriately is to flush the line and ensure the transducer is located at the level of the heart. 

Indications for arterial catheter placement:

• Frequent lab testing (i.e. blood gas monitoring in intubated patients)
• Persistent blood pressure monitoring 
• Hypotensive patients requiring vasopressors 
• Hypertensive patient with intracranial hemorrhages or aortic pathology 

Possible Sites:

• Radial artery
• Axillary artery
• Femoral artery
• Dorsalis Pedis 

It is important to avoid sites that do not have collateral flow such as the brachial artery due to the risk of thrombosis. 

References:

Nguyen, H.B, Huang, D.T. & Pinsky, M.R. (2016). Section 4: Resuscitative Procedures. In Tintinalli's Emergency Medicine: A Comprehensive Study Guide (8th ed., pp. 205-214). New York, NY: McGraw-Hill Education.