The safe way to obtain the ABG
This client with chronic obstructive pulmonary disease (COPD) is hypoxemic on a Venturi mask at 28%. When the mask was briefly lifted, his oxygen saturation fell from 90% to 83% within 2 minutes. Oxygen is never withheld from a hypoxemic client, including one who retains carbon dioxide. No room-air sample has been ordered. The nurse resumes the oxygen, draws the arterial blood gas on his prescribed oxygen, and records the delivery device and FiO2 of 28% on the request.
Why recording the oxygen setting is essential
The partial pressure of arterial oxygen (PaO2) depends directly on the oxygen the client is breathing. A PaO2 that is acceptable on 28% oxygen would mean something very different on room air. By writing the device and the fraction of inspired oxygen (FiO2) on the request, the nurse allows the result to be interpreted correctly and compared with future results. This is a standard part of ABG collection in any client receiving oxygen.
Why removing oxygen is dangerous
Taking him off oxygen for 20 minutes would expose him to prolonged hypoxemia; he has already shown how quickly his saturation falls. Hypoxemia can cause dysrhythmias, confusion, and tissue injury, especially during an acute exacerbation with purulent sputum and increased breathlessness. Watch out! A room-air sample is sometimes requested for specific purposes, but it must be ordered and done only when safe; a student's suggestion is not a reason to remove oxygen.
Why the other options are wrong
| Option | Problem |
|---|
| Keep him off oxygen for 20 minutes, then draw | Causes dangerous hypoxemia |
| Draw now, before saturation falls further | Sample reflects neither room air nor his treatment, and he stays hypoxemic |
| Resume oxygen and cancel the test | He needs the ABG now to guide treatment |
| Resume oxygen, draw, note 28% | Safe and interpretable |
Oxygen in carbon dioxide retainers
Clients with COPD who retain carbon dioxide are given controlled oxygen, such as a Venturi mask, to a target saturation that is often around 88 to 92%, because excessive oxygen can worsen carbon dioxide retention. But the answer to this risk is careful titration and monitoring, not withdrawal of oxygen. His 3-month-old stable ABG is useful for comparison, showing his usual baseline for carbon dioxide and bicarbonate.
Exam takeaway
Draw the ABG on the client's prescribed oxygen and record the device and FiO2; never remove oxygen from a hypoxemic client to obtain a room-air sample. Key point! In COPD, use controlled oxygen to a target range rather than stopping it.