**Question:** Characteristic of type-II respiratory failure is: September 2010

**Core Concept:** Type-II respiratory failure, also known as acute respiratory acidosis, is a condition in which the lungs and respiratory muscles are functioning normally but the kidneys are unable to maintain the pH balance by excreting excess hydrogen ions (H+). In contrast, type-I respiratory failure (acute respiratory alkalosis) is caused by impaired lung function contributing to the imbalance in pH regulation.

**Why the Correct Answer is Right:** Type-II respiratory failure occurs when the kidneys fail to compensate for the increased acidity (decreased pH) in the blood due to excessive CO2 production or decreased CO2 elimination. In September 2010, the focus should be on the renal dysfunction as the primary cause of respiratory acidosis, not impaired lung function.

**Why Each Wrong Option is Incorrect:**

A. Type-I respiratory failure (acute respiratory alkalosis) is the correct answer for a question about impaired lung function causing respiratory alkalosis. It is not related to renal dysfunction.

B. Type-II respiratory failure (acute respiratory acidosis) is the correct answer when renal dysfunction is the primary cause, not increased CO2 production.

C. Acute respiratory acidosis with impaired lung function (type-I) is the correct answer when lung function is the primary issue, not renal dysfunction.

D. Chronic renal failure is unrelated to the question as it involves a long-term kidney condition rather than a sudden dysfunction like the question is asking for.

**Clinical Pearl:** Type-II respiratory failure emphasizes the importance of recognizing and distinguishing between different types of respiratory failure based on the primary cause (renal or pulmonary). Adequate assessment of the patient's clinical condition and history can guide the appropriate diagnosis and treatment.

**Correct Answer:** Type-II respiratory failure (acute respiratory acidosis) is the correct answer when renal dysfunction is the primary cause of respiratory acidosis, as seen in September 2010. This is typically due to acute kidney injury (AKI) or prerenal azotemia, both of which lead to reduced ability of the kidneys to excrete excess H+ ions, resulting in an imbalance between acidic and alkaline substances in the blood.