10. Respiratory Failure (Type I & II)

📄Definition

Respiratory failure is defined as inadequate gas exchange by the respiratory system resulting in hypoxaemia ± hypercapnia.

  • Type I: Hypoxaemia (PaO₂ < 8 kPa), normal or low PaCO₂

  • Type II: Hypoxaemia with hypercapnia (PaCO₂ > 6.0 kPa)

🔬 Pathophysiology

🧠 Mnemonic: HARD GAS

  • Hypoventilation (esp. in Type II)

  • Alveolar-capillary membrane dysfunction

  • Right-to-left shunt

  • Diffusion impairment

  • Gas exchange failure

  • Air trapping or obstruction

  • Shunting of blood without oxygenation

🛡️ Causes

Type I (Hypoxaemic)

🧠 Mnemonic: PAPAS

  • Pneumonia

  • ARDS

  • Pulmonary oedema

  • Asthma (severe)

  • Shunting (e.g. congenital heart)

Type II (Hypercapnic)

🧠 Mnemonic: COPD CHAMP

  • COPD

  • Overdose (opiates/benzodiazepines)

  • Polio (neuromuscular)

  • Dead space ↑ (e.g. PE)

  • CNS depression

  • Head injury

  • Airway obstruction

  • Myasthenia gravis / Guillain-Barré

  • Pickwickian syndrome (Obesity Hypoventilation)

Risk Factors

  • Smoking (for COPD)

  • Neuromuscular disorders

  • Obesity

  • Sedative use

  • Existing lung disease

📋Clinical Features

🧠 Mnemonic: LATE FROG

  • Lethargy

  • Anxiety, agitation

  • Tachypnoea

  • Exertional dyspnoea

  • Flushed skin (esp. in Type II)

  • Reduced LOC

  • Oxygen desaturation

  • Gasping or accessory muscle use

🩺 Physical Examination Findings

  • Cyanosis

  • Tachycardia

  • Use of accessory muscles

  • Asterixis (flapping tremor in Type II)

  • Altered mental status

🔍 Investigations

🧠 Mnemonic: ABG + ROOT CAUSE

  • ABG – essential for diagnosis (Type I vs II)

  • Respiratory exam: auscultation, percussion

  • Oximetry – initial screen but unreliable in CO₂ retention

  • Overview CXR – exclude pneumonia, oedema, effusion

  • Toxicology if overdose suspected

  • CBC, CRP – infection screen

  • Anion gap if metabolic cause suspected

  • Urea, creatinine, LFTs – baseline

  • Spirometry – if stable

  • ECG – arrhythmias or RV strain (PE)

🧾 Management

🧠 Mnemonic: OXYGEN FIRST

  • O₂ therapy: start with controlled O₂ via Venturi mask

  • Xclude Type II before high-flow O₂ (risk of CO₂ retention)

  • Yield ABG results within 30 mins

  • Guided escalation: NIV or intubation if failing

  • Escalate early to ITU if unstable

  • NIV (BiPAP) for COPD with respiratory acidosis

  • Fluid management: avoid overload

  • Investigate & treat cause (antibiotics, bronchodilators)

  • Rehabilitate chronic causes (CPAP, lifestyle, smoking cessation)

  • Specialist referral for neuromuscular or recurrent cases

  • Target sats:

    • Type I: 94–98%

    • Type II: 88–92%

⚠️ Complications

  • Respiratory arrest

  • Cardiac arrhythmias

  • Cerebral oedema (CO₂ retention)

  • Multi-organ failure

  • Death if untreated

🧐 Differentials

🧠 Mnemonic: SHOCKED LUNG

  • Sepsis

  • Heart failure

  • Overdose

  • COPD exacerbation

  • Ketoacidosis

  • Embolism (PE)

  • Diffuse parenchymal disease

  • Lung collapse

  • Uraemia

  • Neuromuscular disease

  • Guillain-Barré syndrome

📌 PARA Revision Tips

  • ABG interpretation is a core skill – know normal values

  • Focus on causes and how Type I ≠ Type II

  • Know indications for NIV vs intubation

  • Red flags: lethargy + rising PaCO₂ = impending respiratory arrest

🔎 Last updated in line with NICE CG177 (2014)
Last reviewed: July 2025
🔒 PASSMAP ensures all content is NICE-aligned and reviewed for Physician Associate Registration Assessment (PARA) success.

Scroll to Top