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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
pCO2 and H+ in the CSF
• Chemoreceptors responding to CO2, H+ and
O2 in the walls of arteries:
– Aortic body (X)
– Carotid body (IX)
Gas transport
• Oxygen
• About 1.5% dissolved
• 4 molecules of O2 bind to each molecule of
Hb
• 100 mls blood contains about 20 ml O2
• Partial pressure is the most important
determinant
Oxygen
• 75% saturated at pO2 of 40 mm Hg
• Increasing acidity decreases binding (Bohr
Effect)
• CO2 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 CO2 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