Making ABG interpretation easy

1.9 Making ABG interpretation easy


The golden rule for making ABG interpretation easy is to assess pulmonary gas exchange and acid base status independently.



Assessing pulmonary gas exchange



• Using the algorithm opposite, classify gas exchange into one of the four possible categories.

• If there is type 1 respiratory impairment, assess severity of hypoxaemia (box 1)

• If there is type 2 respiratory impairment, establish whether it is chronic or acute, then assess severity of hypercapnia and hypoxaemia (boxes 1 & 2)

• If the category is hyperventilation, determine whether it is primary or secondary.


Box 1.9.1 Assessing hypercapnia severity


Severity is not related to absolute PaCO2 value but to the rate of PaCO2 rise and degree of blood pH derangement (pH < 7.25 = severe acidaemia). The presence of exhaustion is also an ominous sign.


Table 1.9.1 Assessing hypoxaemia severity































  PaO2 SaO2
Mild 8–10.6 kPa 90–94%
60–79 mmHg  
Moderate 5.3–7.9 kPa 75–89%
40–59 mmHg  
Severe < 5.3 kPa < 75%
< 40 mmHg  
or: High FiO2 requirements to maintain adequate Pao2  


image

Figure 21 Assessing pulmonary gas exchange.

Related posts:

  1. Common ABG values
  2. When and why is an ABG required?
  3. Pulmonary gas exchange: the basics
  4. Acid–base balance: the basics

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Dec 18, 2016 | Posted by in CARDIOLOGY | Comments Off on Making ABG interpretation easy

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