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Alternation of Respiratory function李雯婷 (Airway Resistance (pressure and…
Alternation of
Respiratory function李雯婷
Diffusion and Transport of Respiratory Gases
Oxygen diffuses into the blood from the alveoli, and CO2 diffuses out of the blood into the alveoli
passive movement of gas from a highconcentration area to a low-concentration area
random, kinetic motion of molecules through the respiratory membranes and fluids
Lung Compliance
Neurologic Control of Ventilation
neural control centers
chemoreceptors
lung receptors
proprioceptors
pressure receptors
other decreasing chest wall distensibility
abdominal distention
pregnancy
kyphoscoliosis
abdominal surgery
obesity
Disease
pneumonia
pulmonary edema
atelectasis
ARDS
pulmonary fibrosis
decrease in the elderly
increasing chest wall rigidity from calcification of costal cartilages
reduced mobility of ribs
partial contraction of inspiratory muscles
Changes in the thoracic vertebrae and intervertebral disks
decreased expansion of the chest wall in the elderly
Obstructive Pulmonary Disorders
Asthma
defined by paroxysms of diffuse wheezing, dyspnea, and cough
involve inflammation of the airways
lung disease characterized
(a)airway obstruction that is reversible
(b) airway inflammation
(c)increased airway reactivity to a variety of stimuli
triggered:allergens and stimuli, such as exercise and exposure to cold air
PEFR is measured to determine the index of airway function.
Airflow obstruction is indicated by a FEV1/FVC ratio of less than 75%.
COPD:emphysema and chronic bronchitis
airway obstruction is persistent and irreversible.
chronic bronchitis are cigarette smoking (90% of cases)(repeated airway infections)
chronic inflammation and swelling of the bronchial mucosa resulting in scarring
increased fibrosis of the mucous membrane
hyperplasia of bronchial mucous glands and goblet cells
neutrophil activity|,CD8 T lymphocyte elevated
bacterial:H. influenzae and S. pneumoniae.
Emphysema
destructive changes of the alveolar walls and abnormal enlargement of the distal air sacs
marked reduction in the pulmonary capillary bed,
smoking, air pollution, certain occupations ,Age>50years
Cigarette smoking in excess of 70 pack-years
alveolar destruction,release of proteolytic enzymes from inflammatory cells:marked reduction in the pulmonary capillary bed,
Smoking causes alveolar damage
parenchyma:release of proteolytic enzymes that directly damage alveolar tissue
inactivates α1-antitrypsin
loss of alveolar walls
Pulmonary Blood Flow
Hypoxic Vasoconstriction
diverting blood flow to areas of higher oxygen concentration
gas exchange are reduced
Low alveolar oxygen concentration
contraction of smooth muscle in the walls of the small pulmonary arterioles
Blood is diverted from areas of low alveolar oxygen concentration to areas of higher oxygen concentration
Distribution of blood flow
affected by body position and exercise
assumes the supine position, blood flow to the posterior dependent portion of the lung is higher than to the anterior lung
he effect of gravity on the lung has led to the concept of lung zones
Pulmonary Vasculature
Perfusion is the second process of respiration
low-pressure system
(25/8 mm Hg).
blood in the lungs 450 ml or 9%
Unoxygenated blood from the right ventricle is pumped into the main pulmonary artery and then into its branches, which divide into capillary beds throughout lung tissue
The capillary beds surround the alveoli and allow for diffusion of O2 and CO2
Airway Resistance
cartilage assists in maintaining airway passage stability, thus preventing airway collapse.
Stimulation of cholinergic fibers leads to bronchoconstriction.
stress, pulmonary conditioning, and age
Stimulation of the β2-adrenergic receptors leads to bronchodilation.
pressure and flow
Resistance increases as the radius of the airway tube decreases.
The bronchial muscles function to maintain an even distribution of ventilation.
Restrictive Pulmonary Disorders
Occupational Lung Diseases
inhalation of toxic gases or foreign particles
protected by mucociliary system and alveolar macrophages
Alveolar macrophages attempt to engulf and remove inorganic dust
(1) migrating to small airways to use the mucociliary escalator
(2) engulfing dust and exiting through the lymph and/or blood system
(3) passing through bronchial walls, depositing dust particles in extraalveolar tissue
4) destroying the particle (silica)
Atelectati Disorders
ARDS
(1) injury to the alveoli from a wide variety of disorders
(2) changes in alveolar diameter
(3) injury to the pulmonary
(4) disruptions in oxygen transport and utilization
injury include
(1) severe hypoxemia caused by intrapulmonary shunting of blood
(2) decrease in lung compliance
(3) decrease in FRC
(4) diffuse, fluffy alveolar infiltrates on the chest radiograph
(5) noncardiogenic pulmonary edema
Damage to the alveolar-capillary membrane,widespread protein-rich alveolar infiltrates and severe dyspnea
Pleural Space Disorders
Pleural Effusion
various types of effusions relate to changes in pleural capillary hydrostatic pressure, colloid oncotic pressure, or intrapleural pressure
(1) transudates
severe heart failure
edematous states.
(2)Exudates: increased production of fluid
inflammation or impaired lymphatic drainage.malignancies, infections (especially pneumonia), pulmonary embolism, sarcoidosis, post–myocardial infarction syndrome, and pancreatic disease.
(3) empyema attributable to infection in the pleural space
(4) hemothorax or hemorrhagic pleural effusions
(5) chylothorax or lymphatic pleural effusions
Pneumothorax
Spontaneous pneumothorax
accumulation of air in the pleural space
Fibrotic Interstitial Lung Diseases
Hypersensitivity Pneumonitis
antigen combines with the serum antibody in the alveolar walls, leading to a type III hypersensitivity reaction
Diffuse Interstitial Lung Disease
injury : alveolar epithelial or capillary endothelial cells
interstitial and alveolar wall thickening and increased collagen bundles in the interstitium
Lung tissue becomes infiltrated by lymphocytes, macrophages, and plasma cells
Lung Parenchyma Disorders ：marked reduction in the pulmonary capillary bed