Hypoventilation from pulmonary, cardiac, musculoskeletal or neuromuscular diseases can cause?

UPUMS Nsg officer-2023

Applied Physiology

Hard

Appeared in: UPUMS Nsg officer-2023

Explanation

Hypoventilation is defined as inadequate ventilation, which prevents the lungs from effectively removing carbon dioxide (CO₂).
The retention of CO₂ in the blood is called hypercapnia. This leads to an increase in the partial pressure of CO₂ (PCO₂).
Elevated PCO₂ causes more CO₂ to combine with water, forming carbonic acid (H₂CO₃). This acid dissociates, releasing hydrogen ions (H⁺) and lowering the blood pH.
A primary respiratory problem (impaired ventilation) that leads to a drop in pH is defined as respiratory acidosis.
Conditions affecting the lungs, chest wall, or neural control of breathing, as mentioned in the question, are common causes of hypoventilation.

Option A: Metabolic alkalosis involves an excess of bicarbonate (HCO₃⁻) or loss of acid, leading to a high pH. Hypoventilation causes CO₂ retention (an acid), not a loss of acid or gain of base.
Option B: Metabolic acidosis is caused by a deficit of bicarbonate or an excess of non-respiratory acids (like ketones or lactic acid). The primary problem in the question is respiratory.
Option D: Respiratory alkalosis is the direct opposite of the condition described. It is caused by hyperventilation (breathing too fast or too deep), which leads to excessive elimination of CO₂ and a rise in blood pH.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pathophysiology of Acid-Base Imbalances as background academic context rather than a clinical decision trigger.
Nurses must be able to recognize signs of hypoventilation, such as shallow breathing, slow respiratory rate, confusion, and somnolence, as these indicate impending respiratory acidosis.
Monitoring arterial blood gases (ABGs) is crucial for diagnosing and managing respiratory acidosis. The key findings are a pH below 7.35 and a PaCO₂ above 45 mmHg.
The primary nursing intervention is to treat the underlying cause of hypoventilation to improve gas exchange. This may involve administering bronchodilators, providing respiratory support (like BiPAP or mechanical ventilation), or reversing sedative effects.

How to Approach the Question

First, identify the core concept in the question stem: 'Hypoventilation'.
Recall the physiological meaning of hypoventilation: breathing is too slow or shallow to eliminate sufficient carbon dioxide (CO₂).
Connect CO₂ to the body's acid-base balance. Remember that CO₂ acts as an acid in the blood (by forming carbonic acid).
Reason that if the body is retaining an acid (CO₂), the result will be 'acidosis'.
Determine the origin of the problem. Since it's caused by a breathing issue ('hypoventilation'), it is a 'respiratory' problem.
Combine the findings: The condition caused is 'Respiratory acidosis'.

Concept Tested & Keywords

Concept Tested: Pathophysiology of Acid-Base Imbalances
Stem keywords: Hypoventilation, pulmonary disease, cardiac disease, musculoskeletal disease, neuromuscular disease
Lead-in keywords: can cause

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