**Question:** For the following medical conditions, select the associated acid base disturbances: Chronic pulmonary disease on steroids.

A. Metabolic acidosis
B. Respiratory alkalosis
C. Respiratory acidosis
D. Respiratory alkalosis

**Core Concept:**
Chronic pulmonary disease, particularly chronic obstructive pulmonary disease (COPD), can lead to respiratory acidosis due to decreased carbon dioxide (CO2) elimination from the blood. Steroids, when used in the treatment of chronic pulmonary diseases, can cause a shift in the respiratory compensation mechanism, leading to worsening of acidosis if they suppress the ventilatory response to hypercapnia.

**Why the Correct Answer is Right:**
Chronic pulmonary disease on steroids results in decreased ventilatory response to hypercapnia, which is the body's natural response to increased CO2 levels. This leads to decreased CO2 elimination, causing a shift in the respiratory compensation mechanism and ultimately results in respiratory acidosis.

**Why Each Wrong Option is Incorrect:**
A. Metabolic acidosis is typically associated with conditions like diabetes, renal failure, or starvation. Chronic pulmonary disease on steroids primarily affects the respiratory compensation mechanism, not the direct acid-base imbalance due to impaired kidney function or starvation.

B. Respiratory alkalosis is associated with conditions like alkalosis, vomiting, or excessive salivation. Chronic pulmonary disease on steroids results in impaired respiratory compensation, not increased CO2 elimination or alkalosis.

C. Respiratory acidosis is associated with conditions leading to decreased CO2 elimination like neuromuscular disorders or anesthesia. Chronic pulmonary disease on steroids results in impaired respiratory compensation, not decreased CO2 elimination.

D. Respiratory alkalosis is associated with conditions like vomiting, excessive salivation, or alkalosis. Chronic pulmonary disease on steroids results in impaired respiratory compensation, not alkalosis.

**Clinical Pearl:**
In clinical practice, understanding the effect of steroids on the respiratory compensation mechanism is essential when dealing with patients on steroids for chronic pulmonary diseases. Monitoring for signs of respiratory acidosis and adjusting treatment, including dosage and mode of administration, is crucial to avoid complications related to acid-base imbalances.

**Correct Answer:** Respiratory acidosis (C)

*Reasoning:*
Chronic pulmonary disease on steroids leads to impaired respiratory compensation, which results in decreased CO2 elimination and respiratory acidosis. Steroids can suppress the ventilatory response to hypercapnia, causing an imbalance in the respiratory compensation mechanism. This results in a shift from the normal respiratory alkalosis response to hypercapnia, leading to respiratory acidosis.