NORCET 7 Prelims -2024: A nurse caring for an adult on high-flow nasal cannula (HFNC) should understand which statement is correct?

NORCET 7 Prelims -2024

Medical & Surgical Nursing

Easy

Appeared in: NORCET 7 Prelims -2024

Explanation

The standard clinical guideline for High-Flow Nasal Cannula (HFNC) is to select prongs that occupy no more than 50% of the diameter of the patient's nares.
This sizing is crucial because HFNC works as an 'open system,' which requires space around the cannula for gas to leak out during exhalation.
This intentional leak is necessary to flush carbon dioxide (CO2) from the anatomical dead space of the upper airway, which is a primary mechanism of HFNC.
Proper sizing also prevents the dangerous buildup of unintended positive end-expiratory pressure (PEEP) and potential barotrauma to the airways.

Option A: HFNC therapy provides continuous, not intermittent, heated and humidified gas. This is essential to prevent drying and damage to the nasal and airway mucosa at high flow rates.
Option C: HFNC can deliver a fraction of inspired oxygen (FiO2) across the full range, from 21% (room air) up to 100%, via an integrated air-oxygen blender.
Option D: Choosing the largest cannula to block the nares is contraindicated. The therapy relies on a leak around the prongs to function correctly. Occluding the nares prevents CO2 washout and can cause dangerous pressure buildup (barotrauma).

Clinical Relevance

Nursing practice connection: Knowing Principles of High-Flow Nasal Cannula (HFNC) Therapy helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
A key nursing responsibility is selecting the appropriate size of the nasal interface and regularly assessing the patient's nares for any signs of pressure injury or skin breakdown.
Nurses must continuously monitor the patient's work of breathing, respiratory rate, and oxygen saturation (SpO2) to evaluate the effectiveness of the therapy and titrate flow and FiO2 settings as ordered.
What if? If the nares are fully occluded by the cannula, the nurse must immediately switch to a smaller size. Occlusion turns the open system into a closed one, risking barotrauma and causing the patient to rebreathe CO2, which negates the primary benefit of the therapy.

How to Approach the Question

First, identify the core concept of the question, which is the correct application and principles of High-Flow Nasal Cannula (HFNC) therapy.
This is a factual recall question. Your goal is to evaluate each statement based on your knowledge of how HFNC works.
Analyze Option A: Recall that high flows of dry gas are damaging to the mucosa. Therefore, humidification must be continuous and heated, not intermittent. This option is incorrect.
Analyze Option C: Recall that HFNC is a high-flow system used for respiratory support, capable of delivering a wide, precise range of oxygen concentrations. Limiting it to below 50% is incorrect.
Analyze Option D: Recall the mechanism of HFNC involves washing out CO2 from the upper airway. This requires an open system with a leak. Minimizing the leak by occluding the nares is counterproductive and dangerous. This option is incorrect.
Analyze Option B: This leaves the statement about prong size. The 50% rule is the standard safety and efficacy guideline for HFNC to ensure it functions as an open system. This statement is correct.

Concept Tested & Keywords

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E6 Nursing Fundamentals Potter Perry 12e Part 5 p. 7-9

E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 663-665