Respiratory Disease

Control of Ventilation Medulla –Inspiratory centre (Dorsal respiratory group) –Expiratory centre (Ventral respiratory group) fires during forced expiration Pons –Pneumotaxic centre –Apneustic centre

Control of Ventilation Neural –Stretch receptors in bronchial tree and visceral pleura - Hering-Breuer reflex –Limbic and hypothalamic inputs enable emotion to modify ventilation –Cortex can override –Pulmonary irritant reflexes - bronchioles constrict

Control of Ventilation Chemical Chemoreceptors in medulla respond to pCO 2 and H + in the CSF Chemoreceptors responding to CO 2, H + and O 2 in the walls of arteries: –Aortic body (X) –Carotid body (IX)

Gas transport Oxygen About 1.5% dissolved 4 molecules of O 2 bind to each molecule of Hb 100 mls blood contains about 20 ml O 2 Partial pressure is the most important determinant

Oxygen 75% saturated at pO 2 of 40 mm Hg Increasing acidity decreases binding (Bohr Effect) CO 2 also binds to Hb Temperature BPG BPG binds less strongly to foetal Hb Gas Transport

Carbon Dioxide About 55 ml per 100 ml deoxygenated blood at rest Dissolved: 7% Carbaminohaemoglobin: 23% Bicarbonate ions: 70% Chloride shift

Definitions Dyspnea: difficulty or shortness of breath Hypoxia: inadequate oxygen at cellular level Hypercapnia: elevated blood CO 2 levels Cyanosis: bluish colouration of skin or mucous membranes due to prescence of excess deoxygenated haemoglobin

COPD Emphysema Bronchitis Cystic fibrosis

Emphysema Loss of elasticity Enlargement of air spaces distal to terminal bronchioles Destruction of alveolar walls and capillaries Causes –SMOKING –  -antitrypsin deficiency –Genetic factors

Bronchitis Inflammation of major and small airways Edema and hyperplasia of submucosal glands Excess mucous secretion into bronchial tree Simple or chronic Causes: –SMOKING –Infections thought to be a result

Manifestations “pink puffer” or “blue bloater” Emphysema has proportionate loss of ventilation and perfusion Bronchitis mismatches ventilation and perfusion Emphysema and Bronchitis

Cystic Fibrosis Autosomal recessive disorder Alters fluid secretion in exocrine glands of epithelial lining of respiratory, gastrointestinal and reproductive tracts Chronic respiratory disease Pancreatic exocrine deficiency Elevation of NaCl in sweat

Cor Pulmonare Caused by pulmonary hypertension as a result of: –COPD –Cystic fibrosis –Sleep apnea –Scarring of pulmonary vasculature –Severe curving of upper spine

Cor Pulmonare Chronic requirement for output from right ventricle leads to right sided heart failure Blood accumulates in the periphery: –Fatigue –Dependent edema –Liver engorgement –Ascites –Anorexia and gastric distress –cyanosis