ABG 🩸 Flashcards
(18 cards)
What does pO₂ measure?
The partial pressure of oxygen dissolved in the blood plasma.
What does SaO₂ measure?
The percentage of hemoglobin binding sites in the arteries occupied by oxygen.
What does SpO₂ stand for and what does it measure?
Peripheral oxygen saturation; it estimates arterial oxygen saturation (SaO₂) noninvasively using a pulse oximeter.
Which blood gas value is measured directly from arterial blood?
SaO₂.
Which blood gas value is estimated using light absorption?
SpO₂.
What is the normal range for pO₂ on room air?
80–100 mmHg.
What is the normal range for SaO₂ on room air?
95–100%.
What is the normal range for SpO₂ on room air?
95–100%.
What’s the difference between pO₂ and SaO₂?
pO₂ is the pressure of dissolved oxygen in plasma; SaO₂ is the percentage of hemoglobin molecules carrying oxygen.
What’s the difference between SaO₂ and SpO₂?
SaO₂ is measured directly from an ABG; SpO₂ is estimated by a pulse oximeter.
Can SpO₂ be trusted in carbon monoxide poisoning?
No, it can give falsely high readings.
Can SpO₂ detect low pO₂ in anemia?
No, SpO₂ can be normal even in severe anemia because it measures saturation, not content.
How can you tell if a blood gas sample is arterial?
High pO₂ (>70 mmHg), bright red color, and spontaneous flow due to high pressure.
What’s the typical pO₂ value in a venous blood gas (VBG)?
~40 mmHg.
Can VBG be used to assess oxygenation?
No, it cannot reliably assess oxygenation — only ABG can.
What factors can cause SpO₂ readings to be inaccurate?
Poor perfusion, cold extremities, nail polish, motion artifact, CO poisoning, or methemoglobinemia.
What happens to the oxyhemoglobin curve in acidosis, hypercapnia, or high 2,3-BPG?
It shifts to the right, promoting oxygen release to tissues.
What happens to the curve in alkalosis, hypothermia, or low 2,3-BPG?
It shifts to the left, increasing oxygen affinity.
