Respiratory failure occurs when the respiratory system cannot maintain adequate gas exchange, leading to hypoxemia (low oxygen) and/or hypercapnia (high carbon dioxide).

The signs and symptoms can vary depending on whether it is acute or chronic, and whether it is hypoxemic (type I) or hypercapnic (type II).

Common Signs and Symptoms 

1. Early Symptoms 

Dyspnoea (shortness of breath) – often the first symptom 
Tachypnoea (rapid breathing) 
Fatigue or weakness 
Restlessness, anxiety, or confusion (especially if hypoxia is severe) 
Use of accessory muscles for breathing (neck and chest muscles) 
Nasal flaring (especially in children) 

2. Signs of Hypoxemia (low oxygen, Type I) 

Cyanosis (bluish lips, fingers, or skin) 
Tachycardia (rapid heart rate) 
Hypertension initially (can progress to hypotension in severe cases) 
Sweating (diaphoresis) 
Altered mental status (agitation, confusion, lethargy) 
Pallor or mottled skin 
In severe cases, coma may develop 

3. Signs of Hypercapnia (high carbon dioxide, Type II) 

Headache 
Flushed skin 
Drowsiness or somnolence 
Confusion or disorientation 
Tremors or asterixis (flapping tremor of the hands) 
Papilledema (in chronic cases) 
Bounding pulse and elevated blood pressure 
In severe cases: CO₂ narcosis, leading to stupor or coma 

4. Other Clinical Signs 

Changes in breathing pattern: if extreme, Cheyne-Stokes, Kussmaul respirations, or irregular breathing 
Inability to speak in full sentences 
Hypotension and shock in severe acute cases 
Wheezing, stridor, or crackles if underlying lung pathology is present 

Key Points 

Acute respiratory failure usually presents with rapid onset dyspnoea, cyanosis, and acute confusion. 

Chronic respiratory failure may present more subtly, with morning headaches, daytime sleepiness, and polycythemia. 

Early recognition is crucial; monitoring oxygen saturation (SpO₂), arterial blood gases (ABG), and vital signs is essential for diagnosis and management.