# A nurse is caring for a critically ill client receiving 100% FiO2 via mechanical ventilation for 30 hours. Which assessment finding most warrants notifying the provider?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=391786&lang=en  
> language: en  
> subject: Medical Emergencies  
> category: PA

## Question

A nurse is caring for a critically ill client receiving 100% FiO2 via mechanical ventilation for 30 hours. Which assessment finding most warrants notifying the provider?

## Option

1. Oral temperature 37.4°C, mild sinus tachycardia, and unchanged lung sounds suggesting expected mild stress response
2. New retrosternal chest discomfort, dry cough, and decreasing pulmonary compliance suggesting oxygen toxicity **✔ Correct answer**
3. Serum glucose of 130 mg/dL, mild anxiety, and increased heart rate suggesting stress-induced hyperglycemia
4. Urine output of 60 mL/hr, slightly decreased skin turgor, and dry mucous membranes suggesting mild dehydration

**Correct answer: 2**

## Explanation

Correct (2): Prolonged exposure to high FiO2 (>50%) for >24-48 hours causes pulmonary oxygen toxicity — substernal pain, dry cough, dyspnea, decreasing compliance from atelectasis and alveolar damage; can progress to ARDS-like injury. Lower FiO2 to

## In-depth explanation

Memory Tip Oxygen toxicity = "Above 50, beyond 50" — FiO2 >50% for >50 hours. CPG Wean FiO2 using PEEP and prone positioning rather than relying on high FiO2.

## Clinical scenario

Scenario 48-year-old male, ARDS on mechanical ventilation with FiO2 100% for 30 hours. New retrosternal chest discomfort, non-productive cough, and decreasing lung compliance on ventilator settings.

## Key concepts

- **Pulmonary oxygen toxicity** — Free radical injury from prolonged high FiO2; chest pain, dry cough, decreasing compliance.
- **PEEP** — Positive end-expiratory pressure used to recruit alveoli and reduce FiO2 needs in ARDS.
- **FiO2 weaning** — Reduce inspired oxygen fraction to

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