Arterial Blood Gas

Question 1

how long does pulmonary transit take?

Answer 1

0.75 seconds
The time during which blood and blood cells are in direct contact with alveoli enabling gas exchange

Question 2

how long does gas exchange take?

Answer 2

0.25 seconds

Question 3

what is the difference in pO2 between arterial and venous blood?

Answer 3

goes from 10+ kPa to between 4 - 5.3 kPa

Question 4

what is the difference in pCO2 between arterial and venous blood?

Answer 4

goes from 4.7-6.0 in arterial to 5.3-6.7 in venous

Question 5

what is the difference in O2 saturation between arterial and venous blood?

Answer 5

goes from 96%+ to approx 75%

Question 6

what is the role of blood in pH balance?

Answer 6

good buffering capacity to quickly react to changes

Question 7

what are the body’s compensatory acid-base mechanisms?

Answer 7

ventilation and kidney secretion/retention

Question 8

how fast do each act?

Answer 8

respiratory compensation is fast, metabolic compensation is slow

Question 9

what is the format for reporting arterial blood gas results?

Answer 9

CADO → compensation? aetiology, disturbance, oxygenation

Question 10

what is the normal pH range?

Answer 10

7.35 to 7.45

Question 11

what is BE?

Answer 11

base excess → describes the concentration of bases compared with the expected concentration . An exact match is 0 and excess of base is positive and a base deficit is negative

Question 12

what is BE normal range?

Answer 12

-2 to 2

Question 13

what is the normal range for pCO2?

Answer 13

4.7 - 6.4 kPa

Question 14

what is the normal range of pO2?

Answer 14

10 - 13.5 kPa (rarely too high)

Question 15

what are the different aetiologies of acid/base imbalance?

Answer 15

respiratory/metabolic/mixed acidosis/alkalosis

Question 16

what is the CO2 flux rate out of tissues

Answer 16

4mL/dL/min

Question 17

How do you calculate PH from H+ and vice versa

Answer 17

pH=-log10[H+]
Or [H+]=10^-PH

Question 18

Resp and metabolic acidosis

Answer 18

Resp-carbonic acid
Metabolic-lactic acidosis,keto acidosis,Hcl

Question 19

Carbon dioxide loading

Answer 19

Carbon dioxide moved from cells into the blood down the conc gradient and combines with water forming carbonic acid catalyzed by carbonic anhydrase which dissociates into H+ and HCO3-
HCO3- moves into plasma and cl- enters rbc via AE1 transporter . H+ combines with Carbon dioxide and Hb forming Hbco2
Carbon dioxide also enters red blood cells to form carb amino haemoglobin

Question 20

What is the normal range for PO2

Answer 20

10-13.5 kPa

• 8-10- mild hypoxaemia
• 6-8- moderate hypoxaemia
• <6- severe hypoxaemia

Question 21

HCO3- normal range

Answer 21

22-26 meq/L