Disorders of Ventilation


  • When there is alveolar hypoventilation, arterial PC02 increases above the range of 37 – 43 mmHg.
  • PaC02 may be 50 – 80 mmHg.
  • The respiratory system is dependent upon a complex system of ventilatory control to ensure appropriate and adequate ventilation in order to supply oxygen, remove carbon dioxide, and maintain acid-base homeostasis.
Disorders of Ventilation

Disorders of Ventilation Causes Clinical Features Treatment


  • · Obesity
  • · COPD
  • · Myasthenia gravis
  • · Motor neuron disease
  • · Poliomyelitis
  • · Brain stem infarction and haemorrhage
  • · Metabolic alkalosis
  • · High cervical hauma
  • · Obstructive sleep apnea
  • · Cystic fibrosis
  • · Kyphoscoliosis.

Clinical Features of Disorders of Ventilation :

  • · Cyanosis
  • · Secondary polycythemia
  • · Pulmonary hypertension
  • · RVH (Right Ventricular Hypertrophy)
  • · CHF (Congestive Heart Failure)
  • · Morning headache
  • · Fatigue
  • · Somnolence
  • · Mental confusion
  • ·Intellectual impairment.

Treatment of Disorders of Ventilation

  • Treat the cause
  • Correction of metabolic acidosis Supplemental oxygen Progesterone may be of benefit Mechanical ventilatory support Diaphragmatic pacing
  • Bipap ventilation – non-invasive positive pres­sure ventilation.

HYPOVENTILATION SYNDROMES Primary alveolar hypoventilation

  • · It is a disorder of unknown cause
  • · There is chronic hypercapnia and hypoxaemia
  • · There is no neuromuscular disease.

Respiratory neuromuscular disorders

  • · Disease of spinal cord, peripheral respiratory nerves and disease of respiratory muscles pro­duce a chronic hypoventilation syndrome over a • period of months to years e.g. MND (Motor Neu­ron Disease), myasthenia gravis, muscular dystrophy.

Obesity hypoventilation syndrome

  •  Massive obesity causes a load on the respiratory system due to weight on the rib cage and abdo­men reducing the compliance of the chest wall.
  • Treatment is reduction of weight, cessation of smoking in smokers, treatment of sleep apnea, enhancement of respiratory drive by progesterone.


  • Alveolar hyperventilation is PaC02 below range of 37­.- 43 mmHg.

Causes are Disorders of Ventilation :

  • High altitude
  • Pulmonary disease – Cardiac shunts
  • – Chest wall disorder
  • – CHF
  • Diabetic acidosis ./ Hepatic failure ../ Psychogenic
  • Salicylate induced ‘IT Fever
  • Sepsis
  • Pain
  • Pregnancy.
  • Treatment is removal of underlying cause. Usually alveolar hyperventilation has no clinical consequence and may not require treatment.


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