# A client with severe COPD and chronic hypercapnia is brought to the ED with worsening dyspnea, SpO2 86%. Which is the most appropriate initial oxygen prescription?

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> url: https://mymerci.kr/pages/nclex_q.php?qn_id=391785&lang=en  
> language: en  
> subject: Medical Emergencies  
> category: PA

## Question

A client with severe COPD and chronic hypercapnia is brought to the ED with worsening dyspnea, SpO2 86%. Which is the most appropriate initial oxygen prescription?

## Option

1. Place the client on a CPAP at 100% FiO2
2. No supplemental oxygen — the body will compensate
3. High-flow oxygen at 15 L/min via non-rebreather mask
4. Titrate oxygen to maintain SpO2 88-92% via nasal cannula 2 L/min, monitoring for changes in mental status and ventilation **✔ Correct answer**

**Correct answer: 4**

## Explanation

Correct (2): COPD clients with chronic CO2 retention rely partly on hypoxic respiratory drive; excessive O2 can blunt the drive and worsen CO2 retention, causing somnolence and respiratory acidosis. Target SpO2 88-92% with the lowest effective flow. Monitor neuro status and consider ABG. (1) High-flow can cause CO2 narcosis. (3) CPAP at 100% inappropriate as initial step in this scenario. (4) Hypoxia must be treated.

## In-depth explanation

Memory Tip COPD = "88-92" target. Cardiac/respiratory arrest, sepsis: target 94-98%. CPG If somnolence develops on O2, suspect CO2 narcosis — check ABG and consider NIV (BiPAP).

## Clinical scenario

Scenario 71-year-old male with severe COPD and chronic CO2 retention (baseline PaCO2 58). ED presentation: dyspnea, RR 28, SpO2 86% on room air, alert, mild lethargy.

## Key concepts

- **Hypoxic respiratory drive** — Backup ventilatory drive in chronic CO2 retainers; excessive O2 may suppress it.
- **COPD oxygen target** — SpO2 88-92% with titration; avoid hyperoxia.
- **CO2 narcosis** — CNS depression from rising PaCO2; presents as somnolence and confusion after high-flow O2.

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