Respiratory failure and Acute Respiratory Distress Syndrome (ARDS) are life-threatening conditions that require immediate recognition and intervention. They often develop as complications of infections, sepsis, trauma, or other critical illnesses. Both conditions disrupt the body’s ability to exchange gases, leading to dangerously low oxygen (O₂) or high carbon dioxide (CO₂) levels.
This article covers:
- Definition and types of respiratory failure
- Causes and pathophysiology of ARDS
- Signs and symptoms
- Diagnostic criteria including ABG values
- NCLEX exam tips and memory aids
- Priority nursing interventions
Understanding Respiratory Failure
Respiratory failure occurs when the capillaries in the alveoli cannot adequately exchange oxygen and carbon dioxide. This may happen due to blocked, inflamed, or fluid-filled alveoli, which prevent oxygen from entering the blood and CO₂ from being exhaled.
Causes
- Infections (e.g., pneumonia) causing alveolar swelling and mucus build-up
- Progression from a common respiratory infection (like flu) to pneumonia
- Acute Respiratory Distress Syndrome (ARDS) as a complication
Acute Respiratory Distress Syndrome (ARDS)
Definition
ARDS is a severe form of respiratory failure characterized by refractory hypoxemia — oxygen levels remain low despite high levels of supplemental oxygen.
Memory Trick:
REsistant to Oxygen = REfractory Hypoxemia.
Pathophysiology
- Initial trigger – infection, sepsis, aspiration, or trauma causes inflammation in the lungs.
- Alveolar damage – Capillaries around the alveoli become leaky, allowing fluid to enter alveolar spaces.
- Hard alveoli – Fluid and inflammation make alveoli stiff and unable to expand.
- Gas exchange failure – Oxygen cannot enter the blood effectively, and CO₂ clearance is impaired.
If untreated, patients can die from severe hypoxia.
Causes of ARDS
- Sepsis – systemic infection triggering widespread inflammation
- Respiratory inflammation – pneumonia, inhaled toxins, aspiration
- Acute pancreatitis – enzymes and cytokines from the pancreas cause lung inflammation
- Trauma or shock – systemic injury increasing inflammatory response
NCLEX Tip:
Acute pancreatitis significantly raises the risk of ARDS due to inflammatory mediators entering the lungs.
Types of Acute Respiratory Failure (ARF)
Hypoxemic Failure (Low O₂)
- PaO₂ ≤ 60 mmHg
- Caused by impaired oxygen exchange in the lungs
Hypercapnic Failure (High CO₂)
- PaCO₂ ≥ 50 mmHg
- Caused by impaired ventilation leading to CO₂ retention
Signs and Symptoms
Hypoxemia (Low O₂)
- Altered mental status (NCLEX tip: #1 early sign)
- Agitation
- Restlessness
- Confusion
ARDS Key Feature
- Refractory hypoxemia: Low PaO₂ despite oxygen therapy
Lab Values in ARDS:
- Low PaO₂
- High CO₂
- ABG shows impaired oxygenation and ventilation
ABG Interpretation – NCLEX Focus
Common Exam Question Example:
Which ABG values indicate acute respiratory failure?
Correct answer:
PaO₂ 47 mmHg, PaCO₂ 63 mmHg → Hypoxemia + Hypercapnia.
Priority Interventions for ARDS
Use the HOLY acronym:
- H – High Fowler’s position (HOB up) to improve lung expansion
- O – Oral suctioning & supplemental oxygen
- L – Listen to lung sounds regularly
- Y – Yell for help – notify healthcare provider immediately
Additional Management:
- Mechanical ventilation with PEEP (Positive End-Expiratory Pressure) to keep alveoli open
- Continuous monitoring of oxygenation, ventilation, and hemodynamics
Nursing Diagnosis Examples
- Impaired gas exchange related to alveolar-capillary membrane changes
- Ineffective breathing pattern related to decreased lung compliance
- Risk for decreased cardiac output related to hypoxemia
Prevention & Early Detection
- Monitor high-risk patients (sepsis, pancreatitis, pneumonia)
- Educate on early signs of hypoxemia (confusion, restlessness)
- Rapid response activation if SpO₂ drops despite oxygen therapy
Summary Table – ARDS & Respiratory Failure
| Feature | Respiratory Failure | ARDS |
|---|---|---|
| Cause | Any condition impairing gas exchange | Severe lung injury with refractory hypoxemia |
| PaO₂ | ≤ 60 mmHg | Low despite O₂ therapy |
| PaCO₂ | ≥ 50 mmHg (hypercapnic failure) | May be high or normal |
| Pathophysiology | Impaired ventilation or oxygenation | Leaky capillaries + stiff alveoli |
| Treatment | O₂ therapy, treat cause | Mechanical ventilation + PEEP |
Frequently Asked Questions (FAQs)
Q1. What is the hallmark of ARDS?
Refractory hypoxemia – low PaO₂ despite high oxygen delivery.
Q2. Can ARDS be reversed?
Yes, with early aggressive treatment and ventilatory support, but mortality rates remain high.
Q3. How is ARDS different from regular pneumonia?
ARDS involves diffuse alveolar damage and severe oxygenation failure, not just localized infection.
Q4. What is the most important early sign of hypoxemia?
Altered mental status – agitation, restlessness, confusion.
Q5. Why is PEEP important in ARDS?
It prevents alveolar collapse, improving oxygen exchange.
