I
Introduction to ABG Sampling
- A.Definition - arterial puncture to measure oxygenation, ventilation, and acid-base balance.
- B.Higher-risk than venous access - arteries are deeper and demand firm post-puncture pressure.
Arterial puncture technique and the numbers that tell you how well someone is actually breathing - done safely, read correctly.
This page is educational, not clinical protocol. Arterial puncture is an invasive skill with real vascular risk and requires supervised, hands-on practice before it's performed on a real patient.
An arterial blood gas sample measures how well someone is oxygenating, ventilating, and maintaining acid-base balance, all from one arterial puncture. It's a higher-stakes skill than venous access - arteries are deeper, more painful to puncture, and demand firm post-puncture pressure to prevent a hematoma. CARDIG-Jerusalem's ABG Workshop builds the technique and the interpretation together, on realistic arm models.
Three sites in routine use, ranked by preference - accessibility and safety both favor the same first choice.
Hover or tap each point to see where it sits on the body.
Superficial, easy to compress, and backed up by the ulnar artery's collateral flow - the default first choice.
Try firstLarger and easier to feel, but deeper and closer to the median nerve - use when radial access fails.
Backup optionLarge and reliable in an emergency, but carries the highest complication risk and needs strict technique.
Emergency backupEight steps, starting with a safety check that has to pass before the puncture even happens.
01 Compress radial and ulnar arteries
02 Fist clenches, hand pales
03 Release the ulnar artery only
04 Color returns within 10 sec = normal
Compress both the radial and ulnar arteries, have the patient clench and release their fist until pale, then release only the ulnar artery and confirm color returns within 10 seconds.
Extend the wrist about 30 degrees over a rolled towel to bring the artery closer to the surface.
Locate the strongest pulse point with your non-dominant hand and keep a finger nearby to guide the needle.
Disinfect thoroughly and let it fully air-dry before puncture, same asepsis standard as any other invasive skin puncture.
Enter bevel-up at 30-45 degrees to the skin, steeper than venous access, aiming directly at the palpated pulse.
Arterial blood should fill the syringe on its own from pulse pressure - it shouldn't need to be actively drawn back.
Fill the syringe to the required volume, then withdraw the needle in one smooth motion.
Hold direct pressure for at least 5 minutes, expel any air bubbles from the sample, and transport on ice if analysis will be delayed.
An abnormal Allen test changes the plan. If color doesn't return within 10 seconds, ulnar collateral flow can't be confirmed - move to a different site rather than risk that hand's blood supply.
Four numbers, each telling a different part of the same story - oxygenation, ventilation, and acid-base balance.
Overall acid-base status - below is acidosis, above is alkalosis.
The respiratory component - reflects how well the lungs are ventilating.
How well oxygen is getting from the lungs into the blood.
The metabolic component - the kidneys' contribution to acid-base balance.
A summary number for the overall metabolic acid-base picture.
Once you know the pH is abnormal, the next question is which system caused it.
A PaCO₂ that moves in the opposite direction of the pH points to a respiratory problem - too much or too little ventilation.
High CO₂ with low pH suggests respiratory acidosis, often from hypoventilation.
An HCO₃ that moves in the same direction as the pH points to a metabolic problem, arising outside the lungs.
Low HCO₃ with low pH suggests metabolic acidosis, often from a build-up of acid elsewhere in the body.
Once you know which system caused the problem, check whether the other system has started correcting for it.
pH is abnormal, and only one of PaCO₂ or HCO₃ is abnormal. The compensating system hasn't responded yet.
pH is still abnormal, but both PaCO₂ and HCO₃ are abnormal and moving in the direction that corrects it.
pH has returned to the normal range, but PaCO₂ and HCO₃ are both still abnormal, revealing the underlying problem.
Arterial puncture carries more risk than venous access - these are the ones the workshop specifically drills.
Short teaching blocks feed directly into hands-on practice on realistic arm models, so every concept gets rehearsed within minutes of being taught.
Performing and correctly timing the modified Allen test until it's second nature.
Ranking radial, brachial, and femoral access by safety and accessibility.
Angle, pulse tracking, and pulsatile flash recognition, repeated on realistic arm models.
Air bubble removal, labeling, and transport timing before values start to drift.
Reading pH, PaCO₂, PaO₂, and HCO₃ together to identify the acid-base picture.
Full ABG panels paired with a clinical vignette, worked start to finish.
The questions we actually get about the workshop.
It helps but isn't required. Arterial puncture uses a steeper angle and different landmarks than venous access, so Station 3 starts from the fundamentals either way.
No. Every attempt happens on realistic arm models with simulated pulsatile flow - this workshop builds the technique before anyone touches a real patient under supervision.
Yes - CARDIG-Jerusalem issues a CARDIG Certification to everyone who completes the workshop and passes the skills check-off, verifiable through our Verify Certificate portal.
Station 1 covers exactly that scenario and what it means for site selection - recognizing an abnormal result is as important as performing the test correctly.
Station 5 and 6 cover the basics of reading the four key values and distinguishing respiratory from metabolic causes - full compensation analysis is a more advanced topic outside this workshop's scope.
On whether you correctly identify the acid-base picture from the four values, not on diagnosing the underlying clinical cause.
This page explains arterial blood gas sampling for learning purposes - it is not a substitute for supervised, hands-on clinical skills training. Arterial puncture is an invasive procedure with real vascular risk and requires direct instructor oversight before independent practice.
CARDIG-Jerusalem runs hands-on clinical skills training for Al-Quds medical students and members - this page is the starting point, not the endpoint.
Explore Membership →A condensed, section-by-section reference. For the full explanation of each point, see the Workshop overview above.
Want the full explanation behind each point? The Workshop overview above walks through every section here in detail, including the reasoning behind each guideline.