Question

Jane Doe presents to the ER via the ambulance. She is using accessory muscle breathing while talking to the nurse. She states that she gets like this sometimes when she sleeps to long. Patient states she has a history of diabetes, sleep apnea and asthma. Jane is morbidly obese an maintaining an oxygen saturation of 90% on a non rebreather, HR 118, BP 141/76. When she speaks her oxygen goes down into the 80's. Jane can not complete a sentence without stopping to take a breath. The MD orders an ABG, what do you expect to find based on her current oxygen saturation?

Answer 1

ABG analysis

ABG (arterial blood gas) analysis is carried out in patients to determine the direct measurements in arterial blood they are (pH, Pao2, Paco2).

The relationship between Oxygen Saturation and pH, PaO2, PaCO2 are very much related to each other as one increases the other show significant changes and vice versa.

In the present scenario the patient is suffering with diabetes, sleep apnoea and asthma and the saturation has fallen down to 80.

	Oxygen saturation
Normal	95 - 100
Hypoxaemia	Less than 95
Mild Hypoxaemia	90-94
Moderate Hypoxaemia	75 - 89
Severe Hypoxaemia	Less than 75

According the above table the patient falls under moderate Hypoxemia

Now, with this the pH and PaCO2 alter accordingly. The approximate values that you will find if the Oxygen saturation is 80 are the following

Moderate Hypoxemia	Oxygen Saturation	pH	PaCO2
	75 - 89	7.8	28
Normal Range	95 – 100	7.35 – 7.4	35 - 45

These changes will further lead to increase acidosis and lead to metabolic acidosis. In which the HCO3 levels are decrease which has a normal range of 21-28. HCO3 levels become less than 21