Transcript Respiratory regulation of Acid

Respiratory regulation of Acid-Base
Balance
DR. SUMREENA MANSOOR
ASSISTANT PROF OF BIOCHEMISTRY
DEPT OF BIOCHEMISTRY & MOLECULAR BIOLOGY
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Arterial Blood Gas (ABG)
pH, pCO2, pO2 – Measured directly
HCO3-, O2 saturation (usually) – Calculated from pH, pCO2, and
pO2
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Normal Arterial Blood Gas Values

pH
7.35 - 7.45

PaCO2
35-45 mmHg(4.7-6.0kpa)

PaO2
70-100mmHg(11.3-12.6kpa)

SaO2
93 - 98%

HCO3¯
22 - 26 mmol/L
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Arterial Blood Gases
Condition
State of
PaCO2
in blood
alveolar ventilation

> 45 mm Hg
Hypercapnia
Hypoventilation

35 - 45 mm Hg
Eucapnia
Normal ventilation

< 35 mm Hg
Hypocapnia
Hyperventilation

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Practical Approach
1. Check the pH

If the pH < 7.35 acidemia is present.

If the pH > 7.45 alkalemia is present.
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Practical Approach
2. Check the pCO2

pH < 7.35 and pCO2 > 40  respiratory acidosis

pH > 7.45 and pCO2 < 40  respiratory alkalosis
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17 year-old female patient while hyperventilating (frequent,
deep, sighing respiration to sustained, obvious, rapid, deep
breathing) fell unconscious to the floor. An attending
Physician diagnosed her condition as "hyperventilation
syndrome" caused by her anxiety and mental stress.
He
successfully treated her by rebreathing expired CO2 from a
paper
bag
and
she
completely
recovered.
What happened to the acid-base balance in her body?
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Respiratory alkalosis
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54 year-old man becomes critically unwell with confusion
and hypotension
Test
Results
Normal Range
PaO2
7.9 kPa
11.3-12.6
PaCO2
12.8 kPa
4.7-6.0
pH
7.16
7.36-7.44
HCO-3
42 mmol/l
20-28





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Respiratory acidosis with renal
compensation
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A 25 year-old patient has acute
exacerbation of bronchial asthma.
Which abnormality on the arterial
blood gas evaluation does this
patient most likely have?
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High pH suggesting low Hydrogen
*[H+] ions
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17 year old w/severe kyphoscoliosis, admitted for
pneumonia

pH:
7.47

pCO2:
25 mmHg

pO2:
60 mmHg

HCO3:
14 mmol/L
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Compensated respiratory alkalosis due
to chronic hyperventilation secondary to
hypoxia
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9 year old with H/O asthma, audibly wheezing x 1 week,
has not slept in 2 nights; presents sitting up and using
accessory
muscles
to
breath
with
audible
wheezes
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
pH:
7.51

pCO2:
25 mmHg

pO2
35 mmHg

HCO3:
22 mEq/L
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Uncompensated
respiratory
alkalosis
with severe hypoxia due to asthma
exacerbation
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57-year-old male with COPD, home oxygen dependence,
daily chronic sputum production, is treated with several
types of metered dose inhalers. No other medications. He is
in his usual state.
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Chronic respiratory acidosis
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The patient described in above problem develops increasing shortness of
breath, purulent sputum production, and increased weakness requiring
emergency room visit. He appears to be in moderate respiratory distress
peripheral cyanosis.
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Acute respiratory acidosis and
chronic respiratory acidosis
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MALE, AGED 70 YEARS, WITH RESPIRATORY
AND METABOLIC FAILURE DUE TO COPD. HE WAS
ADMITTED TO ICU AND MECHANICALLY VENTILATED
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
ON ADMISSION THIS PATIENT HAD A PARTIALLY
COMPENSATED RESPIRATORY ACIDOSIS, i. e  PCO2 AND
[HCO-3]. VENTILATION WAS OVER-ENTHUSIASTIC AND
PRODUCED A RESPIRATORY ALKALOSIS (P CO2 <35).
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THANKS