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Disoders of Ventilation. Sung Chul Hwang, M.D. Dept. of Pulmonary and Critical Care Medicine Ajou University School of Medicine. Central Medulla Oblongata pH, PaCO2, PaO2 fall in pH of ECF and Carotid body Fine regulation. Peripheral Aortic and Carotid body PaO2
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Disoders of Ventilation Sung Chul Hwang, M.D. Dept. of Pulmonary and Critical Care Medicine Ajou University School of Medicine
Central Medulla Oblongata pH, PaCO2, PaO2 fall in pH of ECF and Carotid body Fine regulation Peripheral Aortic and Carotid body PaO2 dominant during Chronic hypoxia Coarse regulation Chemoreceptor
Alveolar Hypoventilation • Increased PACO2 & PaCO2 above normal • Impaired respiratory drive: brain stem, carotid body trauma • Reduction in over all minute ventilation: resp. muscles, spinal cord, peripheral nerves • Impaired respiratory apparatus : chest wall, airways and lung
Neuromuscular Disorders • Spinal cord, peripheral nerves, respiratory muscle disease • orthopnea, paradocxical movement of abdomen and diaphragm • Dx : Rapid deterioration of MVV, reduced Pimax, Pemax, reduced transdisphragmatic pressures and response to phrenic nerve stimulations
Pathophysiology • Increased PACO2 & PaCO2 • Respiratpory Acidosis • Metabolic compensation -- increase in HCO3 -- • Decrease in Cl - • Decrease in PAO2 & PaO2 • Pulmonary vasoconstriction, Pulmonary hypertension, RV hypertrophy, CHF • (Cor pulmonale)
Mechanoreceptor • Stretch receptor : smooth muscle of trachea and main bronchus • Irritant receptor : beneath the epithelium of larynx, trachea, bronchi • J- receptor : periphery of lung • C- receptor : pulmonary interstitial space near pulmonary and bronchial circulation
Clinical features • Hypoxemia, cyanosis, polycythemia • chronic hypoxemia , hypercapnea, pulmonary HTN, CHF • ABG abnormality esp. in sleep and sleep disturbances • Sx : morning headache, fatigue, daytime somnolence, mental confusion, intellectual impairment • specific features of underlying diseases
Diagnosis • Defect in Control System : impaired response to chemical stimuli, able to hyperventilate voluntarily • Defects in N-M System : Unable to hyperventilate, abnormal static and dynamic lung measurements • Defects in Chest wall, Lungs, Airways : Abnormal airway resistance and compliance, widened (A-a) DO2
Treatment • Treat individual underlying disease • Correction of Metabolic Alkalosis • O2 supplements • Respiratory Stimulants (medroxyprogesterone) • Mechanical Ventilation : especially during sleep • Diaphragmatic pacing
Primary Alveolar Hypoventilation(Ondine’s Curse) • Chronic hypoxemia and hypercapnea without identifiable cause • defect in metabolic respiratory control • 20 - 50 yrs of age males • Sx and Signs of alveolar hypoventilation • treatment : general supportive care for hypoventilation
Obesity-Hypoventilation SD (Pickwickian SD) • Massive obesity • reduced FRC • Underventilation of Lung base and widening of (A-a)PO2 • Chronic hypercapnia, hypoxemia, polycythemia, pulmonary HTN, Right heart failure • Sx : OSA, sleep induced hypoventilation • Tx : stop smoking, weight reduction, correct OSA, medroxy progesterone