How does the body compensate for respiratory acidosis?

Answer 1

Respiratory acidosis can occur during certain respiratory disorders, such as exacerbations of asthma or chronic obstructive pulmonary disease. These exacerbations lead to decreased air movement and increased carbon dioxide retention, decreasing the pH of the blood. Respiratory acidosis is an acute disorder, and metabolic compensation happens gradually over time.

The components of an arterial blood gas for respiratory acidosis without compensation will be as follows:

1. pH will be <7.35 (normal range 7.35-7.45)
2. Bicarbonate will be 22-28
3. Carbon dioxide will be >45 (normal range 35-45)

Therefore, acutely, pH will be low, carbon dioxide will be high, and bicarbonate will be normal. As pH is decreased chronically, the kidneys begin to compensate for the increased acid in the blood. It does so through several mechanisms.

1. Generate bicarbonate in the proximal tube to act as a buffer in the blood
2. Generation of ammonia which acts as a base to accept hydrogen in the urine and excrete acid in the form of ammonium
3. Excrete hydrogen through the urine via the hydrogen-potassium transporter

This compensation takes several days to begin, and you can tell when the kidneys begin to compensate through increase in bicarbonate on an arterial blood gas. A chronic respiratory acidosis with metabolic compensation will appear as follows on an arterial blood gas:

1. pH will be <7.35 (normal range 7.35-7.45)
2. Bicarbonate will be >28
3. Carbon dioxide will be >45 (normal range 35-45)

Metabolic compensation for respiratory acidosis on an arterial blood gas is as follows:

1. Acutely - HCO3 increases by 1mmol/L for every 10 mmHg increase in pCO2 above normal
2. Chronically - HCO3 increases by 4 mmol/L for every 10 mmHg increase in pCO2 above normal

Answer 2

Respiratory acidosis occurs when the lungs can't remove enough CO2, causing blood pH to drop. The body compensates through:

*Acute compensation (minutes to hours):*

1. Increased buffering: Blood proteins and phosphate buffers help neutralize excess hydrogen ions.

2. Renal compensation: Kidneys increase bicarbonate reabsorption and hydrogen ion excretion.

*Chronic compensation (hours to days):*

1. Renal adaptation: Kidneys increase ammonia production, which helps eliminate excess hydrogen ions.

2. Increased bicarbonate production: Liver and kidneys produce more bicarbonate to counterbalance acidosis.

*Respiratory compensation:*

1. Hyperventilation: Increased breathing rate and depth to expel excess CO2.

2. Increased respiratory drive: Stimulation of respiratory centers in the brain.

*Other mechanisms:*

1. Hormonal responses: Release of aldosterone, cortisol, and other hormones to regulate electrolyte balance.

2. Cellular adaptations: Changes in cellular metabolism to reduce acid production.

*Clinical interventions:*

1. Oxygen therapy

2. Ventilatory support (mechanical ventilation)

3. Medications to reduce CO2 production (e.g., sedatives)

4. Treatment of underlying causes (e.g., respiratory disorders, anesthesia)

*Importance of compensation:*

Effective compensation helps maintain blood pH within a narrow range (7.35-7.45), ensuring proper cellular function and preventing severe acidosis.