Respiratory Acid-Base Disorders in the Critical Care Unit

Kate Hopper1

  • 1Department of Veterinary Surgical and Radiological Sciences, University of California, Davis, Room 2112, Tupper Hall, Davis, CA 95616, USA.

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Disorders of Acid-Base Balance01:29

Disorders of Acid-Base Balance

The human body maintains a precise pH range of arterial blood between 7.35 and 7.45. Deviations result in either acidosis (pH < 7.35) or alkalosis (pH > 7.45). These conditions are further classified as respiratory or metabolic disorders based on their underlying cause.
Respiratory Acidosis and Alkalosis
Respiratory acidosis occurs due to an increase in the partial pressure of carbon dioxide PCO2 in the blood. It often arises from shallow breathing or impaired gas exchange caused by...
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Respiratory Regulation of Acid-Base Balance01:18

Respiratory Regulation of Acid-Base Balance

Respiratory compensation is a vital physiological process that stabilizes blood plasma pH by regulating the partial pressure of carbon dioxide (PCO2), a key determinant of pH levels. Most carbon dioxide in the blood dissolves and converts into carbonic acid (H2CO3). It dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3⁻). There is also an inverse relationship between PCO2​​ and pH.
When carbon dioxide levels increase in the blood, more H+ and HCO3⁻ are...
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Acute Respiratory Failure-III01:30

Acute Respiratory Failure-III

Hypercapnic respiratory failure, also known as Type 2 or ventilatory respiratory failure, is a severe condition characterized by the body's inability to effectively remove carbon dioxide (CO2) from the bloodstream. It leads to an arterial CO2 pressure (PaCO2) exceeding 45 mmHg and a blood pH above 7.35. This situation indicates that the body's ventilatory demand, or the ventilation needed to maintain normal PaCO2 levels, surpasses its supply or the maximum gas flow achievable without...
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Diagnosing Acidosis and Alkalosis01:24

Diagnosing Acidosis and Alkalosis

Diagnosing acid-base imbalances involves systematically analyzing arterial blood samples, focusing on three key measurements: pH, bicarbonate (HCO3−) concentration, and carbon dioxide partial pressure (PCO2). This analysis follows a four-step process that helps identify the imbalance's underlying cause and nature.
First, the pH level is assessed to determine whether the blood pH is normal (7.35–7.45), low (acidosis), or high (alkalosis).
Next, the PCO2  and...
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Acute Respiratory Failure-I01:21

Acute Respiratory Failure-I

Acute respiratory failure is a condition characterized by the inability of the lungs to perform their primary function: gas exchange. This failure leads to insufficient oxygen levels (hypoxemia) in the blood, elevated carbon dioxide levels (hypercapnia), or both, causing critical impairment in organ function.
Definition: It is defined by specific criteria based on blood gas measurements. Hypoxemia happens when the partial pressure of oxygen (PaO2) falls below 60 mmHg. At the same time,...
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Acute Respiratory Failure-V01:29

Acute Respiratory Failure-V

The treatment for acute respiratory failure varies based on factors like the underlying cause, overall health, and severity. A collaborative healthcare team is essential for early detection, often through arterial blood gas analysis. Identifying the cause is the primary goal, with treatment strategies adjusted for ventilation/perfusion (V/Q) mismatch, shunting, or diffusion impairment.
Ensure that patients are monitored continuously for their response to therapy, including changes in...
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