High flow oxygen therapy is contraindicated in COPD patients because they have?

KPSC Staff Nurse - 2015

Medical Surgical Nursing

Hard

Appeared in: KPSC Staff Nurse - 2015

Explanation

Patients with chronic COPD often retain carbon dioxide, leading to persistently high PaCO2 levels (chronic hypercapnia).
This chronic hypercapnia causes the central chemoreceptors in the brain to become less sensitive to CO2 as a stimulus for breathing.
The body then comes to rely on a 'hypoxic drive,' where peripheral chemoreceptors respond to low oxygen levels (hypoxemia) to stimulate respiration.
Administering high-flow oxygen corrects the hypoxemia, which can remove this backup drive to breathe, leading to hypoventilation, further CO2 retention (CO2 narcosis), and severe respiratory acidosis.

Option A: COPD patients typically suffer from chronic hypoxemia, which means they have low PaO2. High PaO2 is the result of excessive oxygen therapy, not the underlying condition that creates the contraindication.
Option C: COPD is an obstructive disease characterized by difficulty exhaling. This leads to the trapping of air and CO2, resulting in high PaCO2 (hypercapnia), not low PaCO2.
Option D: To compensate for chronic respiratory acidosis (caused by high PaCO2), the kidneys retain bicarbonate (HCO3) to buffer the acid and normalize the body's pH. Therefore, these patients typically have high HCO3 levels, not low.

Clinical Relevance

Nursing practice connection: Knowing Pathophysiology of oxygen administration in COPD helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses must administer oxygen to COPD patients with known or suspected CO2 retention cautiously, using controlled methods like a Venturi mask to deliver a precise, low concentration (e.g., 24-28%).
The target oxygen saturation (SpO2) for most COPD patients is lower than for healthy individuals, typically 88-92%. Aiming for 100% can be dangerous.
Continuous monitoring for signs of worsening hypercapnia (drowsiness, confusion, headache, asterixis or 'flapping tremor') is a critical nursing responsibility when a COPD patient is on oxygen therapy.

How to Approach the Question

First, identify the core concepts in the question: COPD and the contraindication of high-flow oxygen.
Recall the key pathophysiological feature of advanced COPD, which is the chronic retention of carbon dioxide (hypercapnia).
Understand the body's compensatory response to chronic hypercapnia: the respiratory drive shifts from being CO2-driven to being hypoxia-driven (the 'hypoxic drive').
Analyze the effect of the intervention: High-flow oxygen rapidly corrects hypoxia, thereby eliminating the primary stimulus for breathing in these patients.
Deduce the consequence: Removing the drive to breathe leads to hypoventilation and a dangerous increase in CO2 levels.
Evaluate the options based on this physiological chain of events. The underlying condition that establishes this risk is the chronic high PaCO2.

Concept Tested & Keywords

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E6 Nursing Brunner Adult Health 3SA Vol 1 Part 2 p. 38-40

E6 Medicine Davidson Principles Practice 24e p. 586-588