Understanding Respiratory Acidosis

Respiratory acidosis is a condition where the body has too much carbon dioxide ($\text{CO}_2$) in the lungs, leading to an increase in blood acidity. This typically happens when breathing is too slow or shallow (hypoventilation), preventing the effective removal of $\text{CO}_2$.

Analysis of Options

Let's examine each statement:

• Option 1: Increased rate of ventilation is a cause of respiratory acidosis. This is incorrect. An increased rate of ventilation (hyperventilation) removes excess $\text{CO}_2$ from the body, which can lead to respiratory alkalosis, not acidosis.
• Option 2: Blood pH more than 7. This is incorrect. Acidosis signifies a lower blood pH (below the normal range of 7.35-7.45). A pH greater than 7 indicates a neutral or alkaline state, not acidosis.
• Option 3: Increased levels of carbon dioxide in blood. This is correct. Respiratory acidosis is characterized by impaired $\text{CO}_2$ removal, leading to a buildup of $\text{CO}_2$ (hypercapnia) and consequently, a drop in blood pH. The partial pressure of arterial carbon dioxide ($\text{PaCO}_2$) is elevated.
• Option 4: Acidosis can be compensated through reduction of bicarbonate levels in plasma. This is incorrect. The kidneys try to compensate for respiratory acidosis by *increasing* bicarbonate ($\text{HCO}_3^-$) levels in the plasma to buffer the excess acid. Reducing bicarbonate would worsen the acidosis.

Therefore, the only true statement regarding respiratory acidosis is the increase in blood carbon dioxide levels.