Overview and Key Difference 2. What is PAO 2 3. What is SAO 2 4. The partial pressures of dissolved gases in blood are measured by assuming that the blood was allowed to equilibrate with a volume of gas. It is important to note that O 2 in blood is dissolved in a mixture of other gases such as carbon dioxide and carbon monoxide , but O 2 is the only gas that exerts a pressure on the arterial wall.
When the concentration of O 2 in the blood is higher, the PAO 2 also rises, allowing the blood to carry higher amounts of O 2 in comparison with other fluids such as water.
Measuring and recording PAO 2 is important during disease states because there are certain physiological processes that depend on changes in O 2 in their microenvironments which are characterized by the changes in PAO 2.
Saturation of O 2 SAO 2 in blood defines the percentage of hemoglobin binding sites that are occupied by O 2. Each hemoglobin molecule can occupy four O 2 molecules as it can allosterically modify its conformation to facilitate binding of O 2 to its binding site. This is depicted by the plateau area of the oxygen-hemoglobin dissociation curve. This saturation pattern is the reason for the characteristic sigmoid shaped curve of the O 2 — Hemoglobin curve.
The patient with CO poisoning appears flushed and pink. Children should have sensors appropriate to their size. The monitor is small, portable for use in the field, operating rooms, and in patient hospital rooms to provide continuous, real time monitoring of the patient. Measurement of PaO2 requires drawing and testing an arterial blood sample —something that requires a trained provider, a lab, and time.
Waiting for an ABG can sometimes delay clinical decisions. I have been practicing anesthesia for 35 years and the use of pulse oximetry revolutionized patient safety when we started using it. Oxygen saturation is one of the most valuable tools I have. It can give you early warning about many things, including:. Our staff needs to know that numbers in the low 90s, while acceptable, indicate significant changes in oxygenation that need to be monitored and addressed.
Thank you for the detailed explanation- much more cohesive and detailed than my advanced pathophysiology text. Also, your website name is on point- I chuckled out loud when I stumbled on this page. May the force be with you, An RN-in-training. Thank you so much for the compliment. Let me k now if there are any topics that you would find helpful. Yes, a succinct summary, providing a clear explanation.
Thanks you for asking. Thanks for your suggestion. May the force be with you. My pao2 dropped to 27 dusting a right exersize heart cath dr sent mr back to pulmonologist and he said it was normal this is at Mayo Clinic rochester lol.
Marvelous article! A great teacher is someone who can explain complicated concepts so that anyone can understand them. You have succeeded! I am working on my doctorate in medical speech-language pathology and have spent all evening trying to understand ventilator modes, settings, and terminology.
Your blog was very helpful. Thank you! I try hard to make things clear. I am always open to suggestions about new topics. Thank you. I am a student in an NP program. It has been years since I worked in the ICU as a nurse. In a few months I hit the ICU for clinicals. Your articles and blog are helping get me up to speed again. Much appreciated! The A-a gradient has important clinical utility as it can help narrow the differential diagnosis for hypoxemia.
The A-a gradient calculation is as follows:. The alveolar oxygen pressure PAO2 is not easily measured directly; instead, it is estimated using the alveolar gas equation:.
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