Respiratory Failure

Respiratory Failure - Defining Distress

• Respiratory Failure (RF): Inability of respiratory system to maintain adequate oxygenation ($PaO_2$) or ventilation ($PaCO_2$).
• Types:
  • Type I (Hypoxemic): $PaO_2$ < 60 mmHg (or $SpO_2$ < 90%) with normal/low $PaCO_2$.
    • Mechanisms: V/Q mismatch, shunt, diffusion impairment.
  • Type II (Hypercapnic): $PaCO_2$ > 50 mmHg (pH < 7.35 for acute).
    • Mechanism: Alveolar hypoventilation.
• Respiratory Distress: Increased work of breathing (WOB).
  • Signs: Tachypnea, retractions, nasal flaring, grunting.
  • Accessory muscle use, head bobbing, paradoxical breathing.
• Impending RF: Deterioration despite O2; fatigue, altered sensorium.

⭐ Grunting: expiratory sound (glottic closure) to maintain FRC & ↑ PEEP.

Respiratory Failure - Root Cause Roundup

• Upper Airway Obstruction:
  • Croup, Epiglottitis
  • Foreign body aspiration
  • Laryngomalacia, Tracheomalacia
• Lower Airway Disease:
  • Asthma (severe)
  • Bronchiolitis (RSV)
  • Pneumonia (viral/bacterial)
• Lung Parenchymal Disease:
  • Acute Respiratory Distress Syndrome (ARDS)
  • Pulmonary edema
  • Aspiration pneumonitis
• Neuromuscular Weakness:
  • Guillain-Barré syndrome
  • Spinal Muscular Atrophy (SMA)
  • Botulism
• Central Drive Depression:
  • CNS infection/trauma
  • Drug overdose (opioids)
• Chest Wall/Pleural:
  • Flail chest, Pneumothorax
  • Large pleural effusion
• Cardiac:
  • Congenital heart disease (CHD)
  • Myocarditis

⭐ Bronchiolitis, primarily due to Respiratory Syncytial Virus (RSV), is the most common cause of lower respiratory tract infection and subsequent respiratory failure in infants < 1 year old worldwide.

Respiratory Failure - Spotting the Signs

• Early Recognition is Key: Observe for:

  • Increased Work of Breathing (WOB):
    • Tachypnea: Infants >60/min, Children >40/min.
    • Retractions: Suprasternal, intercostal, subcostal.
    • Nasal flaring, grunting (expiratory sound).
    • Head bobbing, accessory muscle use.
  • Inefficient Breathing:
    • ↓ Air entry, ↓ chest expansion.
    • Wheezing, crackles, stridor.
  • Systemic Effects (Hypoxia/Hypercapnia):
    • CNS: Agitation → lethargy, confusion, coma.
    • CVS: Tachycardia → bradycardia (late), hypertension → hypotension.
    • Skin: Pallor, cyanosis (central: SpO₂ < 90%).

• Diagnostic Aids:

  • Pulse Oximetry: SpO₂ < 90% despite O₂ is alarming. Target >94%.
  • Arterial Blood Gas (ABG): Definitive.
    • Type I (Hypoxemic): PaO₂ < 60 mmHg (FiO₂ ≥ 0.6).
    • Type II (Hypercapnic): PaCO₂ > 50 mmHg & pH < 7.35.
  • Chest X-Ray: Identifies cause (pneumonia, ARDS).

⭐ Tripod position (child leans forward, supporting on arms) maximizes airway opening and indicates significant respiratory distress.

Respiratory Failure - Rescue & Relief

• Oxygen Therapy:
  • Goal: SpO₂ > 92%.
  • Devices: Nasal cannula, Face mask, NRBM, HFNC (provides PEEP).
• Non-Invasive Ventilation (NIV):
  • CPAP/BiPAP for ↑WOB. Contra: GCS < 10, facial trauma.
• Invasive Mechanical Ventilation (MV):
  • Indications: Apnea, failed NIV, $P_aO_2/F_iO_2$ < 200.
  • Lung Protective: Vt 4-6 ml/kg (IBW), Pplat < 30 $cmH_2O$.
• Adjuncts:
  • Bronchodilators, steroids, diuretics.
• ECMO: Refractory hypoxemia/hypercapnia.

⭐ In pediatric ARDS, a key goal of PEEP is to improve oxygenation by recruiting alveoli and preventing atelectrauma.

High‑Yield Points - ⚡ Biggest Takeaways

• Respiratory failure is the most common precursor to pediatric cardiac arrest.
• Early recognition of tachypnea, retractions, grunting, and nasal flaring is crucial.
• Impending failure signs include ↓ respiratory effort, cyanosis despite O2, and altered sensorium.
• Differentiate Type I (Hypoxemic) with low PaO2/FiO2 and Type II (Hypercapnic) with high PaCO2.
• Management priorities: ABC (Airway, Breathing, Circulation), oxygenation, and ventilatory support.
• Common causes include pneumonia, bronchiolitis, and asthma exacerbations.
• Consider PARDS in severe hypoxemia with bilateral infiltrates_._