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.
CHRONIC HYPOVENTILATION Etiologic :
- · 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.
HYPERVENTILATION AND ITS SYNDROMES
- 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
- Treatment is removal of underlying cause. Usually alveolar hyperventilation has no clinical consequence and may not require treatment.