QuestionSBA
QuestionChoice
This is an example of respiratory compensation for metabolic alkalosis. The ABG shows respiratory acidosis, meaning a reduced respiratory rate would be an inappropriate response. Furthermore, this would be an example of respiratory compensation, rather than renal compensation.
10025769
e
Slowing the respiratory rate to retain CO2
QuestionChoice
In the type B intercalated cells of the distal convoluted tubule of the nephron, HCO3- can be secreted and hydrogen ions reabsorbed. This function is important in the response to **alkalosis**. By contrast, the ABG in this case shows a respiratory **acidosis**, making this option incorrect.
10025766
b
The elimination of bicarbonate (HCO3-) and reabsorption of hydrogen ions
QuestionChoice
The kidney plays a key role in acid-base balance. The intercalated cells of the distal convoluted tubule secrete hydrogen ions whilst reabsorbing HCO3- in an attempt to make blood pH more alkaline. As you can see in the ABG, HCO3- is raised, indicating the kidney has attempted to compensate for the chronic increase in CO2 secondary to COPD.
10025765
a
The elimination of hydrogen ions and reabsorption of bicarbonate (HCO3-)
QuestionChoice
An increase in respiratory rate acts to increase carbon dioxide, thus making the blood more alkalotic. This this a more acute mechanism of compensation for acidosis, whereas the vignette refers to chronic respiratory acidosis. Furthermore, an increase in respiratory rate is a respiratory method of compensation, whereas the question specifically asks for renal compensation. This is therefore not the single best answer to this question.
10025767
c
Increasing respiratory rate to exhale more carbon dioxide
QuestionChoice
This is incorrect. Increased reabsorption of hydrogen ions in the kidney occurs in response to blood alkalosis, while increased reabsorption of HCO3- occurs in response to blood acidosis. Reabsorption of both hydrogen ions and HCO3- does not typically occur together. Another important consideration is that many of the transporters responsible for acid-base balance in the kidney can either reabsorb HCO3- and secrete hydrogen ions or vice versa.
10025768
d
Reabsorption of both hydrogen ions and bicarbonate (HCO3-)
Concept
Chapter
2693
4015
Causes of respiratory acidosis
Topic
170
Clinical Chemistry
17551
A 70 year old man presents to A&E with a cough productive of green sputum and increased shortness of breath on exertion. He was diagnosed with chronic obstructive pulmonary disease (COPD) 3 years ago and has previously been noted to retain carbon dioxide. The following arterial blood gas (ABG) is obtained:


||||
|--------------|:-------:|------------------|
|pH|7.30|7.35 - 7.45|
|PaO₂|9.5 kPa|11 - 15|
|PaCO₂|7.2 kPa|4.6 - 6.4|
|Bicarbonate|34 mmol/L|22 - 30|


Which of the following compensatory mechanisms has been carried out by the kidney over the course of his **chronic** COPD.
a