All of the following are true about capillary blood gas sampling ...

[LaDunn]

All of the following are true about capillary blood gas sampling except:
 
  a. capillary sampling can be used in lieu of direct arterial access in some infants and small children.
  b. a capillary sample PO2 provides a fairly close estimate of actual arterial oxygena-tion.
  c. clinicians should exercise caution when using capillary samples to guide decisions.
  d. properly obtained capillary blood can pro-vide estimates of arterial pH and PCO2 levels.

Question 2

A mixed venous blood sample obtained from a pulmonary artery catheter sample has a PO2 of 85 mm Hg and a hemoglobin saturation of 95. Which of the following is likely?
 
  1. The pulmonary artery catheter balloon was not deflated.
  2. The sample was drawn from the proximal, not distal port.
  3. The blood sample was withdrawn too quickly.
  a. 1 and 2 only
  b. 1 and 3 only
  c. 2 and 3 only
  d. 1, 2, and 3

[covalentbond]

Answer to Question 1

ANS: B
Sometimes capillary blood gas sampling is used as an alternative to direct arterial access in infants and small children. Properly obtained capillary blood from a well-perfused patient can provide rough estimates of arterial pH and PCO2 levels. However, the capillary PO2 is of no value in es-timating arterial oxygenation. For this reason, direct arterial access is still the preferred approach for assessing gas exchange in infants and small children. Respiratory therapists must exercise ex-treme caution when using capillary blood gases to guide clinical decisions.

Answer to Question 2

ANS: B
If one fails to deflate the balloon before sampling or withdraw the sample too quickly, the ve-nous blood may be contaminated with that from the pulmonary capillaries. The result is always a falsely high oxygen level.