Respiratory Physiology Flashcards
What does gas flow equal?
Pressure gradient divided by resistance
How thick is the respiratory membrane?
0.5- 1 micrometres thick- efficient gaseous exchange
What does pneumonia do to membrane?
Increases thickness
What does carbonic anhydrase catalyses?
The reaction between carbon dioxide and water to form carbonic acid
What does the chloride shift do?
HC03 moves out of the red blood cellars Cl- ions move in, to balance the ion exchange
What regions of the brain regulates breathing?
reticular formation: medulla and pons
What are the key physiological features of chronic obstructive pulmonary diseases?
Irreversible decrease in ability of lungs to force out air
80% sufferers have a history of smoking
Dispnea- difficult or laboured breathing (air hunger) that gets progressively worse
Coughing and frequent pulmonary infections
Development of respiratory failure manifesting as hypoventilation, respiratory acidosis and hypoxemia
What is COPD linked to?
Emphysema
Chronic bronchitis
Asthma
What does emphysema cause?
Permanent enlargement of the alveoli
Destruction of the alveolar walls
What must be enlisted to breathe due to emphysema?
Accessory muscles leading to fatigue
How much of total energy is required for breathing if a individual has emphysema as oppose to being healthy?
15-20% total energy as oppose to 5% in healthy individuals
What happens to the bronchioles during breathing with emphysema?
They open during inspiration but collapse during expiration, trapping air in the alveoli
What causes the left ventricle of the heart to enlarge in emphysema?
Damage to pulmonary capillaries as alveolar walls disintegrate
What causes chronic bronchitis?
Inhaled irritants lead to chronic production of excessive mucus.
Mucosae of the lower respiratory passageway becomes inflamed and fibrosed.
Obstructs airway
Increases pulmonary infections.
What are the two types oaf patients who have COPD?
- ‘Pink Puffer’- loose weight due to increased effort in maintaining adequate ventilation
- ‘Blue Boaters’- stocky build, becoming hypoxicconstriction of pulmonary blood vessels leading to pulmonary hypertension and right sided heart failure
What are treatments of COPD?
Bronchodilators
Corticosteroids
Surgery- removal of enlarged part of lung to allow greater expansion of remaining lung tissue
Oxygen- (use with caution) dilates pulmonary arteries and drives more CO2 form Hb into alveoli from where it cannot be removed
What is asthma characterised by?
Coughing, dyspnea, wheezing and chest tightness.
Sense of panic for acute attacks
What is the cause of asthma?
Immune response associated inflammation of the lungs
What is the treatments of asthma?
bronchodilators and inhaled corticosteroids
What is Tuberculosis caused by?
Infectious disease caused by the bacterium Mycobacterium tuberculosis
What is TB spread by?
Coughing and spread by inhaled air
When are symptoms of TB apparent?
When immunity is reduced
What are symptoms of TB?
Fever, night sweats, weight loss, racking cough, coughing up blood
What causes lung cancer?
90% cases from smoking
When do sufferers usually die from diagnosis?
Within one year of diagnosis
What are the three common types of lung cancer?
Adenocarcinoma
Squamous cell carcinoma
Small cell carcinoma
Where does Adenocarcinoma develop?
develops from bronchial glands and alveolar cells
Where does Squamous cell carcinoma develop?
develops from epithelium of the bronchi
Where does small cell carcinoma develop?
develop from the main bronchi and grow aggressively
What are the specific causes of asthma?
Immune dysfunction, allergen crosslinks with IgE bound mast cell membrane receptors and causes mast cell degranulation
What are advantages of drugs delivered to the lungs by inhalation?
Direct delivery to the lungs
Smaller doses- reduce side effects
Rapid onset of action
What is the optimum particle size for drug delivery to the lungs?
2-5 micrometers
What happens to particles smaller than 1 micrometer?
Will not reach lower respiratory tract
What happens to particles larger than 10 micrometers?
Will be swallowed
What are pressurised metered dose inhalers and what is used as the propellant?
Most common for delivery of bronchodilators and anti-inflammatory drugs
Uses hydrofluoroalkane as a propellant
What is the spacer on the pressurised metered dose inhaler for?
A plastic reservoir acts as a chamber
Removes need to co-ordinate inhalation
What are the features of breath actuated metered dose inhaler?
Activated by inspiration
Needs flow rate of 30L/min to discharge
Can deliver an aerosol or dry powder
How does dry powder inhalers work?
Inspiration generated turbulence resulting in dispersion of the drug
What does nebulisers do?
Delivers drug from a reservoir solution
10 times as much drug is required to produced the effect of a metered dose device
What are examples of short,long, and ultra long acting beta 2 adrenoceptor agonist?
Short acting: sabutamol, terbutaline
Long acting: formoterol, salmeterol
Ultra long acting: indacaterol
What is the mechanism of action of beta 2 adrenoceptor agonists?
Beta2 adrenoceptors are expressed highly in the bronchial smooth muscle
Stimulation stabilises receptor in its active form
Causes an increase in cAMP and thus PKA leading to regulation of muscle tone
Bronchodilation is due to reduced Ca2+ release from intracellular stores
What are examples of antimuscarinic agents?
Ipratropium, tiotropium
What is the mechanism of action of antimuscarinic agents?
Cells of respiratory system have nicotinic and muscarinic surface receptors.
M3 receptors mediate bronchoconstriction and enhance mucociliary clearance; via a PKC and IP3 pathway
M2 receptors inhibit ciliary activity as well as bronchodilation by inhibiting adenylyl cyclase
What are examples of methylxanthines?
aminophylline, theophylline
What is the mechanism of action of methylxanthines?
Found in coffee, tea, chocolate
Vasodilatory, anti-inflammatory, immunomodulatory actions
Inhibit enzyme phosphodiesterase (PDE).
What are examples of corticosteroids?
beclometasone dipropionate, budesonide, fluticasone
What is the mechanism of action of corticosteroids?
Supress inflammation and the immune response
What is a cough for?
Protective mechanism that removes excessive mucus
Triggered by receptors located in the epithelial surface of the airway mucosa
Where are receptors located in response to a cough reflex?
Pharynx, trachea, bronchi and bronchioles
What are the afferents nerves involved in a cough reflex?
Vague and glossopharyngeal nerves
What is the cough centre?
medulla
What are the efferents nerves in a cough reflex?
Vague, phoenix and spinal motor nerves
What are the effector muscles in a cough reflex?
Glottis, external intercostal, diaphragm
What are the treatments for a cough?
Antitussive: Centrally acting (opioid)
And
Peripherally acting
What do centrally acting opioid do?
Increase threshold for stimulation
What are peripherally acting antitussives and what do they do?
Local anaesthetics (lidocain) Antihistamines to reduce post-nasal drip from allergic rhinitis, which can stimulate cough
