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As the pathogenic process of a respiratory disorder intensify,
The patients arterial blood gas (ABG) values are usually altered to some degree.
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pH (Arterial & Venous)
- Arterial 7.35 � 7.45
- Venous 7.30 � 7.40
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Pc02 (Arterial & Venous)
- Arterial 35 � 45 mmHg
- Venous 42 � 48 mmHg
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HC03 (Bicarb) (Arterial & Venous)
- Arterial 22 � 28 mEq/L
- Venous 24 � 30 mEq/L
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P02 (How much O2 is in arterial blood) Arterial & Venous
- Arterial 80 � 100 mmHg
- Venous 35 � 45 mmHg
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Oxygenated blood is
Arterial Blood
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CO2 is
An acid in the body
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HCO3 is
- Bicarb is a base and is not easily fixed. Usually means that there are other problems.
- A patient with a biocarb of 40 would be chronic because it takes time for it to drop
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ABG�s have
1st, middle and last names
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First name of an ABG is either
Uncompensated or Compensated which depends on the pH of the blood
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Compensated blood has a pH of
7.35 � 7.45 (7.40 is normal pH)
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The Middle name of an ABG is either
Respiratory or Metabolic
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PaCO2 problem is a
Respiratory Problem
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HCO3 Problem is a
Metabolic Problem
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Last name of an ABG is either
Acidosis or Alkalosis
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A PaCo2 between 35 � 45 is
Normal
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A PaCo2 of 34 and under is
Alkalosis
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A PaCo2 46 and above is
Acidosis
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A HCO3 between 22 � 28 is
Normal
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A HCO3 21 and under is
Acidosis
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A HCO3 29 and above is
Alkalosis
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PO2 of
- 80 � 100 (Normal)
- 60 � 80 (Mild)
- 40 � 60 (Moderate)
- Less than 40 aka <40 (Hypoxemia)
- Greater than 100 aka 100< Hyperoxia
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Example
- pH of 7.38 is Compensated
- PaCO2 of 60 is Acidosis
- PaOs of 61 is Mild
- HCO3 of 36 is Alkaline
- Compensated Respiratory Acidosis
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Acute Alveolar Hyperventilation aka Acute Respiratory Alkalosis
- Most common cause of hypoxemia
- As the PaO2 drops, the peripheral chemoreceptors are stimulated, which in turn cause the vent rate to increase
- This causes the PaO2 to decrease and the pH to increase
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Acute Alveolar Hyperventilation
Acute Respiratory Alkalosis
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Acute Ventilatory Failure aka Acute Respiratory Acidosis
- When a patient us unable to provide the work necessary to move gas into and out of the lungs to meet the normal CO2 production
- This leads to increased PaCO2 and decreased PaO2
- Acute vent failure can develop in response to any vent patern that does not provide adequate alveolar ventilation
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Acute Ventilatory Failure
Acute Respiratory Acidosis
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Chronic Ventilatory Failure aka Compensated Respiratory Acidosis
- Has a normal pH with a greater than normal PaCO2 level
- Most commonly seen in patients with COPD, also seen in several restrictive diseases
- When an individual hypoventilates for a long period of time, the kidneys work to correct the decreased pH by retaining HCO3
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Chronic Ventilatory Failure
Compensated Respiratory Acidosis
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The lungs maintain
PaCO2, HCO3 and pH levels on a moment to moment basis
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The Kidneys maintain
HCO3 and pH levels (ONLY) during periods of hyperventilation or hypoventilation
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Patients can have
- Chronic, Restrictive or Both
- Can also have Acute Episodes
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Acute Alveolar Hyperventilation Superimposed on Chronic Ventilatory Failure aka Acute Hyperbentilation on Compensates Respiratory Acidosis
- Like any person a pt with chronic vent failure can also acquire an acute disease (Pneumonia)
- Some pt�s have a mechanical reserve to increase alveolar ventilation to attempt to maintain their baseline Pa02
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Acute Alveolar Hyperventilation Superimposed on Chronic Ventilatory Failure
Acute Hyperventilation on Compensates Respiratory Acidosis
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CO2 retainers
Are hard to vent
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Acute Ventilatory Failure Superimposed on Chronic Ventilatory Failure aka Acute Hypoventilation on Compensated Respiratory Acidosis
- Some patients with chronic vent failure do not have the mechanical reserve to meet hypoxemic challenges of a respiratory disorder
- When a patient tries to maintain a baseline PaO2 by increasing alveolar ventilation, they consume more oxygen than is gained
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Acute Ventilatory Failure Superimposed on Chronic Ventilatory Failure
Acute Hypoventilation on Compensated Respiratory Acidosis
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Lactic Acidosis aka Metabolic Acidosis
- Oxygenation is inadequate to meet tissue metabolism so altered biochemical reactions that do not use oxygen are activated (Anaerobic Metabolisms)
- Lactic Acid is an end product of this
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Lactic Acidosis
Metabolic Acidosis
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When acute hypoxemia exists
Lactic acid is expected (Lactic/Metabolic Acidosis)
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Common Causes of Metabolic Acid-Base Abnormalities
- Metabilic Acidosis
- Lactic Acidosis (Most Common)
- Ketoacidosis
- Salicylate Intoxication (Aspirin O/D)
- Renal Failure
- Chronic Diarrhea
- Metabolic Alkalosis
- Hypokalemia
- Hypochloremia
- Gastric Suctioning
- Vomiting
- Excessive Corticosteroids
- Excessive Sodium Bicarb
- Diuretic Therapy
- Hypovolemia (Dehydration)
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