Physiology of the Respiratory System Obstructive and Restrictive Pulmonary Processes lecture from Physiology and Pathophysiology II 28. 2. 2023 M. Chalupová Respiratory System • O2 supply to the tissues via the blood • regulation of the acid-base balance via the CO2 concentration in the blood Changes in O2 Concentration HYPOXEMIA • decreased oxygen content of the blood • it leads to reduction of oxygen supply to tissue below physiological levels – HYPOXIA – due to insufficient delivery of oxygen (low PaO2) – or inability to utilise oxygen (normal PaO2) Changes in O2 Concentration HYPEROXEMIA • increased oxygen content of the blood • therapy of CO intoxication (hyperbaric oxygenotherapy) Cyanosis • refers to the bluish colour of skin, nails, lips and mucous membranes caused by a higher concentration of deoxygenated hemoglobin in the capillaries • the onset of cyanosis is 50 g/L of deoxygenated hemoglobin in the blood • CNS disorders • bronchial tree and lung disorders – hypoventilation – abnormal pulmonary diffusion • circulatory failure Changes in CO2 Concentration HYPERCAPNIA • increased concentration of carbon dioxide (CO2) in the blood • hypoventilation – brain strokes – overdose of drugs (opiates) HYPOCAPNIA • a state of reduced carbon dioxide in the blood • caused by hyperventilation Spirometry Pathophysiology of Respiration VENTILATION DIFFUSION PERFUSION DISTRIBUTION Diffusion Abnormalities • primarily affects O2 transport • hypoxemia stimulates respiratory centre • hyperventilation hypocapnia INCREASED DISTANCE • lung fibrosis • edema • inflammatory processes DECREASED DIFFUSION AREA • TBC • emphysema • lung resection Distribution Abnormalities • VENTILATION – air that reaches the lungs • PERFUSION – blood that reaches the lungs • V/Q ratio = VENTILATION/PERFUSION • normal V/Q ratio is 4/5 or 0.8 IMPAIRED PERFUSION • area with no perfusion = dead space • high V/Q ratio – pulmonary embolism IMPAIRED VENTILATION • low V/Q ratio – cause of low arterial partial pressure of oxygen (paO2) – chronic bronchitis, asthma and acute pulmonary edema Obstructive Lung Diseases • respiratory diseases characterized by airway obstruction • ASTHMA • CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD) – EMPHYSEMA – CHRONIC BRONCHITIS • CYSTIC FIBROSIS Bronchial Asthma • an acute airflow obstruction caused by bronchoconstriction, edema and mucous production resulting from an allergic or hypersensitive reaction • caused by a specific allergen – house-dust mites, pollen grains, moulds and domestic pets • eosinophils recognise the allergen and B-lymphocytes release allergenspecific IgE Ab • the allergen-IgE complex is bound to IgE-receptors on the surface of mast cells, eosinophils and basophils, hereby, mediators of anaphylactic reactions are released from the mast cell granules – leukotrienes: strong bronchoconstrictors, mucosal inflammation with edema – prostaglandin D2: bronchoconstriction and vasodilatation with increased capillary permeability Symptoms of Bronchial Asthma • wheezing (during exspiration) • cough • shortness of breath • chest tightness • symptoms often worsen at night or in the early morning, or in response to exercise or cold air Chronic Obstructive Pulmonary Disease (COPD) • refers to chronic bronchitis and emphysema • limitation of the airflow causing shortness of breath, chronic cough and frequent respiratory infections • noxious gases, tobacco smoking • CHRONIC BRONCHITIS – inflammation and swelling of the lining of the airways that leads to narrowing and obstruction of the airways – production of mucous (sputum) • EMPHYSEMA – in the alveoli, the inflammatory process causes destruction of alveolar walls and permanent enlargement of the alveoli – air becomes "trapped" in the alveoli and reduces the ability of the lung to shrink during exhalation – acute exacerbations Chronic Obstructive Pulmonary Disease Emphysema Cystic Fibrosis • genetically transmitted chronic obstructive disease characterized by exocrine secretion of thick, copious mucus in the respiratory, GIT and reproductive tracts • bronchial obstruction results in ineffective airway clearance, which causes mucus stasis • it leads to infection, commonly with Pseudomonas aeruginosa or Staphylococcus • permanent parenchymal damage results as bronchial walls are destroyed and the bronchioles become dilated Restrictive Lung Diseases • the distensibility of the lungs (compliance) is decreased • reduction of the diffusion area • gaseous exchange impairment • PNEUMOTHORAX • PNEUMOCONIOSES • ARDS • PULMONARY EDEMA • TBC • PNEUMONIAS Pneumoconiosis • ANTHRACOSIS (coal dust) • SILICOSIS (crystalline silica dust) • ASBESTOSIS (asbestos) • SIDEROSIS (iron oxides) • BYSSINOSIS (cotton) • particles from 1 to 5 μm reach the distal airways • the alveolar macrophages mediate an inflammatory response and initiate fibroblast proliferation and collagen deposition • reduction of the diffusion area Pulmonary Edema • left heart failure • inhalation of corrosive gases • hyperhydratation • shock • multiorgan failure Acute Respiratory Distress Syndrome (ARDS) • reaction to lung injury/inflammation leading to an impaired gas exchange with the systemic release of mediators causing inflammation, hypoxemia and frequently resulting in multiple organ failure • increased permeability of the alveolar-capillary membrane permits fluid and protein to move from the vessels into the interstitium and alveoli, causing pulmonary edema • inactivation of surfactant, alveolar surface tension increases • alveoli become lined with hyaline membranes, compromising the diffusion of respiratory gases • accumulation of fluid, impaired diffusion, which causes hypoxemia RESPIRATORY DISTRESS ARDS Pneumonia • inflammatory process in lung tissue • bacteria – Streptococcus pneumoniae – Staphylococcus aureus – Haemophilus influenzae • viruses – flu viruses – coronaviruses – adenoviruses • cough • chest pain • fever • dyspnoea