3. (2 pts) A patient’s blood pH was measured upon arrival in the emergency room

Question

3. (2 pts) A patient’s blood pH was measured upon arrival in the emergency room to be 7.55 at which point they were treated for alkalosis.
a.Determine the [H+] in this solution.
                    answer 10^-7.55m/L
b. What is the ratio of HCO3-/H2CO3 in the blood at this pH value?
               answer 28HCO3-/H2CO3

c. Normal blood pH is 7.42. How does the ratio of HCO3-/H2CO3 at 7.42 compare to the same ratio at pH 7.55?
d. Calculate the concentration of H2CO3 when the pH is 7.55 and then 7.42. Comment on the measured concentration of HCO3- at normal pH (7.42) is near 23 mM and 21 mM at pH 7.55. Comment on the effectiveness of the blood buffering system at both pH values.

Explanation / Answer

c) At pH 7.42, [H+] = 10-7.42 moles/Liter       pk= 6.1

7.42-6.1=1.32= -log(x) so 10-1.45= x= .04786
take the inverse of this value:.04786-1 = 20.89
the patient's HCO3-/H2CO3 ratio is 21

note how the ratios compare. 28 during the alkalosis and 21 with the normal pH value.

d) so why are the measured values so different than our calculated answers?

[recall, alkalosis. 28 calculated 21 measured   and   normal. 21 calculated 23 measured]

your patient's buffering system is at work, he is in alkalosis but the HCO31- is normal. this tells you that the  HCO31- is already partially compensating for the alkalosis. most importantly, it tells you the  HCO31- is NOT causing the patient's problem. It's not metabolic. It's respiratory.

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