Respiratory acidosis - causes, symptoms, diagnosis, treatment, pathology

Summary

Respiratory acidosis occurs when the lungs fail to expel excess carbon dioxide, leading to a drop in blood pH below 7.35. This can result from respiratory system failure, brain stem issues, neuromuscular disorders, airway obstruction, or impaired gas exchange. The body compensates by increasing ventilation rate and depth, diffusing carbon dioxide into cells, and eventually, the kidneys step in to increase bicarbonate concentration in the blood, helping to restore pH balance.

Takeaways

• 🌬️ Respiratory acidosis occurs when the lungs fail to eliminate excess carbon dioxide, leading to a blood pH below 7.35.
• 🔄 The respiratory system normally balances pH by maintaining a steady rate of carbon dioxide exhalation.
• 🏗️ The diaphragm and chest wall muscles are crucial for the inhalation and exhalation process.
• 🔄 Carbon dioxide reacts with water in the blood to form carbonic acid, which dissociates into hydrogen ions and bicarbonate ions.
• 📈 The partial pressure of carbon dioxide (pCO2) must be kept within a narrow range to prevent pH fluctuations.
• 🚨 Chemoreceptors in the aortic and carotid bodies signal the brain to increase the respiratory rate if pCO2 rises.
• 🏥 Conditions like stroke, medication overdose, and neuromuscular disorders can disrupt the normal respiratory mechanism.
• 🚫 Airway obstruction and impaired gas exchange can prevent efficient elimination of carbon dioxide.
• 🔝 In respiratory acidosis, the body attempts to compensate by increasing ventilation rate and depth.
• 💧 Excess carbon dioxide can diffuse into red blood cells, forming carbonic acid and bicarbonate to counteract increased pCO2.
• 🔄 The kidneys play a role in long-term compensation by increasing bicarbonate reabsorption when pH is too low.

Q & A

What is respiratory acidosis?

Respiratory acidosis refers to a condition where the respiratory system fails to maintain normal pH balance, leading to a blood pH below 7.35 due to the accumulation of carbon dioxide.

How does the respiratory system normally regulate blood pH?

The respiratory system regulates blood pH by adjusting the ventilation rate, which controls the removal of carbon dioxide. Carbon dioxide forms carbonic acid in the blood, which dissociates into hydrogen and bicarbonate ions, affecting pH levels.

What role does carbon dioxide play in respiratory acidosis?

Carbon dioxide binds to water in the blood to form carbonic acid, which dissociates into hydrogen ions and bicarbonate. In respiratory acidosis, the buildup of carbon dioxide causes an increase in hydrogen ions, leading to a lower blood pH.

What happens when the partial pressure of carbon dioxide (pCO2) increases?

When pCO2 increases, chemoreceptors in the carotid arteries and aortic arch notify the brain to increase respiratory rate and depth to expel more carbon dioxide, helping to restore pH balance.

What causes minute ventilation to become inadequate in respiratory acidosis?

Minute ventilation becomes inadequate due to disturbances in the normal mechanism of ventilation. This can be caused by issues such as brainstem damage (e.g., stroke, overdose), neuromuscular disorders, airway obstruction, or impaired gas exchange in the lungs.

What are some common conditions that lead to respiratory acidosis?

Conditions that can lead to respiratory acidosis include opioid or barbiturate overdose, neuromuscular disorders like myasthenia gravis, severe trauma, obesity, airway obstruction (e.g., a lodged object), and diseases that impair gas exchange like COPD or pneumonia.

How does the body initially compensate for respiratory acidosis?

The body initially compensates by increasing the respiratory rate and depth of breathing to expel excess carbon dioxide. If this is insufficient, some carbon dioxide diffuses into red blood cells, where it is converted into bicarbonate to buffer pH changes.

Why is the intracellular pH affected during respiratory acidosis?

The intracellular pH can become acidic because hydrogen ions are generated when carbon dioxide is converted into bicarbonate. If there aren’t enough basic molecules, such as proteins, to neutralize the hydrogen ions, the pH inside cells drops.

How do the kidneys help compensate for chronic respiratory acidosis?

In chronic respiratory acidosis, the kidneys increase bicarbonate production and reabsorption in the proximal convoluted tubules. This helps neutralize excess hydrogen ions and stabilize blood pH over several days.

What is the difference between acute and chronic respiratory acidosis?

Acute respiratory acidosis occurs when there is a rapid increase in pCO2 without sufficient time for renal compensation, leading to a sharp drop in pH. Chronic respiratory acidosis involves renal compensation, where the kidneys increase bicarbonate production to restore pH.