Respiratory Acidosis and Alkalosis Quiz

Case Scenario

• A 19-year-old female medical student presented to the emergency room (ER) with shortness of breath, dizziness, lightheadedness, confusion, and heart palpitations.
• Her history revealed she had been enjoying herself prior to exams, and the prospect of studying the entire course caused severe anxiety and a panic attack.
• Examination revealed rapid, deep, uncontrolled breathing (hyperventilation) and a dry mouth.

ABG Results

• pH: 7.55 (Normal: 7.35 - 7.45)
• PaCO2: 30 mm Hg (Normal: 34 - 44 mm Hg)
• HCO3-: 18 mEq/liter (Normal: 22 - 26 mEq/liter)

Conclusion

• The results indicate respiratory alkalosis.

Learning Objectives

• Respiratory Acidosis:
  • Causes
  • Investigation (ABG)
  • Compensation (ABG)
• Respiratory Alkalosis:
  • Causes
  • Investigation (ABG)
  • Compensation (ABG)

Henderson-Hasselbalch Equation

• Describes pH derivation as a measure of acidity in biological and chemical systems.
• Useful for estimating the pH of a buffer solution.
• 7.4 = 6.1 + log₁₀(20)

Respiratory pH Disturbances

• Acid-base disorders are classified as:
  • Acidosis (low pH)
    • Metabolic
    • Respiratory
  • Alkalosis (high pH)
    • Metabolic
    • Respiratory

The Four Primary Acid-Base Disorders

• Conditions, Primary Disorder, and Compensation are details in the table from the slides
• The table shows the relationship between pH, and HCO3 and pCO2

Causes of Respiratory Acidosis

• Hypoventilation (e.g., asthma, COPD, narcotic poisoning)
• Airway obstruction
• Drug overdose
• Chest trauma
• Pulmonary edema
• Neuromuscular disease

Acute Respiratory Acidosis

• Elevated PaCO2 (greater than 6.3 kPa or 45 mm Hg) and accompanying acidemia (pH < 7.36).
• Causes include: central respiratory depression, neuromuscular disorders, and airway obstruction.

Symptoms of Respiratory Acidosis

• Initial signs include headache, anxiety, blurred vision, restlessness.
• Further symptoms can include sleepiness, tremors, delirium.
• Neurological manifestations depend on the degree of hypercapnia, rapidity of development, severity of acidemia, and hypoxemia.
• Central, muscular, intestinal signs, detailed in table from slides

Compensation Mechanisms

• Chemical buffers initially respond to small acid/base changes
• Respiratory systems respond within minutes to moderate shifts, through retention or elimination of CO2.
• Renal systems respond in hours to more severe shifts by regulating bicarbonate.

Compensation of Respiratory Acidosis

• Pulmonary and renal systems compensate for each other returning pH to normal levels.
• Lungs compensate for metabolic disturbances by altering PaCO2 levels through hyper/hypoventilation.
• Kidneys compensate by altering HCO3- levels by reabsorbing, retaining or excreting it.

Regulation of Respiration

• To maintain normal PO₂ and PCO₂ levels in arterial blood.
• Respiratory control involves three key elements: sensors, central controller, and effectors.

Respiratory Alkalosis

• Acid-base disturbance initiated by a reduction in PaCO2, caused by excessive loss of CO2 through hyperventilation.
• Hypocapnia occurs when the rate of CO2 output from the lungs exceeds CO2 production.

Causes of Respiratory Alkalosis

• Anxiety
• Hypoxia
• High altitude
• Pregnancy
• Fever
• Mechanical ventilation

Symptoms of Respiratory Alkalosis

• Seizures, deep rapid breathing, hyperventilation, tachycardia, low blood pressure, abnormal heart rhythm (hypokalemia), tingling and numbness
• Lethargy, confusion, lightheadedness, nausea and vomiting, further detailed in table from slides.

Hypokalemia

• Low potassium levels (less than 3.5 mEq/L) impact nerve and muscle cell function, especially those in the heart.
• Signs include tiredness, leg cramps, weakness, constipation, abnormal heart rhythms which may cause cardiac arrest.

ABG Interpretation (Table)

• Table showing relationships among ABG components (pH, PaCO2, HCO3)

Compensation of Respiratory Alkalosis

• Describes expected outcomes, including metabolic compensation, detailed in the table

Test your understanding of respiratory acidosis and alkalosis with this quiz. It covers the causes, investigations, and compensatory mechanisms, along with a case scenario involving a medical student. Dive into the biochemical principles with the Henderson-Hasselbalch equation.