Respiratory Flashcards
What is an average tidal volume?
500mL
What is a normal vital capacity?
4.8L
What is the residual volume of the lungs?
1.2L
What is vital capacity?
Total volume of air possible to expire?
Define residual volume.
Volume of the lungs with no air
How do you work out total lung volume?
Vital capacity + residual volume
How do you calculate minute ventilation?
Tidal volume x respiratory rate
How do you calculate alveolar ventilation?
(tidal volume - dead space) x respiratory rate
What is the normal volume of anatomic dead space in the lungs?
150mL
What is FVC?
Forced vital capacity, the maximum volume exhaled
What is FEV1?
Forced expiratory volume within 1 second, should be 80% of FVC
What findings in lung function tests are indicative of obstructive lung disease?
Reduced FEV1 due to increased resistance, less than 80% of FVC
What findings in lung function tests are indicative of restrictive lung disease?
FEV1 and FVC reduced but with FEV1 over 80% of FVC
Vital capacity reduced due to lack of elasticity
What is lung compliance?
The ease with which lungs and thorax expand
What results in high compliance?
Old age, emphysema
Small increase in TP, large increase in volume due to loss of elastic recoil
What results in low compliance?
Oedema, fibrosis, pneumonia
Large increase in TP, small increase in volume due to increased collagen expression and inflammation
What is newborn respiratory distress syndrome?
Occurs in premature babies, type II cuboid cells are underdeveloped reducing surfactant secretion, causing alveolar collapse on expiration
What conditions can cause alveolar collapse on expiration?
Arthritis
Ankylosing spondylitis
Due to reduced spinal cord/rib articulation
What is emphysema?
Degeneration of alveolar, bronchiole walls and capillaries due to proteolytic attack by leukocyte proteases, increasing alveolar dead space.
List the 4 main conducting airways.
Trachea
Bronchi
Bronchioles
Terminal bronchioles
List the 3 main respiratory airways.
Respiratory bronchioles
Alveolar ducts
Alveolar sacs
What is the opening of the larynx?
Glottis, covered by the epiglottis
What are the roles of the conducting airways?
Low resistance pathway for air flow
Warms and moistens air to increase efficiency
Defence against infection
What are the features of the respiratory tract that defend against infection?
Macrophages
Cilia
Mucus secretion and escalator
Movement of chloride ions out of cells
What is cystic fibrosis?
Defective gene leading to cystic fibrosis transmembrane regulator (apical chloride channel) mutations
Leading to mucus build up to to impact on fluid secretion
What features of the respiratory organs help to protect and prevent collapse?
Lungs surrounded by individual pleural sacs
Inner side attached to lungs via connective tissue
Outer side attached to diaphragm and thoracic wall
What is the thoracic wall made up of?
Spinal cord
Ribs
Intercostal muscles
What is pneumothorax?
Pleural sac broken due to puncture of chest wall allowing air to enter, lungs recoil and collapse
In which diseases can spontaneous pneumothorax occur?
Pneumonia
Emphysema
What is the treatment for minor pneumothorax?
X-ray monitoring
Absorption of air
Needle and chest tube insertion
What is the treatment for major pneumothorax?
Surgery to repair puncture
Removal of lung
Describe stage 1 of the asthma treatment pathway.
Occasional use of short acting beta agonist when required
Describe stage 2 of the asthma treatment pathway.
Use of SABA when required
Addition of low dose inhaled corticosteroid as preventer
Describe stage 3 of the asthma treatment pathway.
Use of SABA when required
Low dose inhaled corticosteroid as preventer
Addition of long acting beta agonist
Describe add ons at stage 4 of asthma treatment pathway.
Medium ICS dose Continuation of LABA if benefit seen Trial one of: - leukotriene antagonist - Theophylline - LAMA
What are the add ons at stage 5 of the asthma treatment pathway?
High dose ICS Addition of fourth drug: -leukotriene antagonist - theophylline - beta agonist tablet
What is added at stage 6 of the asthma treatment pathway?
Continued use of oral steroids at lowest effective dose alongside high dose ICS
What are the symptoms of an acute asthma exacerbation?
Cyanosis Drowsiness/unconsciousness Tachycardia Severe dyspnoea PEF <50% Respiratory rate >25 Oxygen sats <92%
What is the treatment for an acute asthma exacerbation in hospital?
Ipratropium nebulisers 500mcg every 4-6 hours
Single dose IV magnesium sulphate
IV aminophylline/salbuatmol
Oxygen 40-60%
What is the standard dose of oral steroids in acute asthma?
40-50mg daily for 5 days
What is the MOA of beta-2 adrenoceptor agonists?
Mimic adrenaline to increase cAMP levels causing relaxation of smooth muscle
Give examples of short acting beta agonists and their onset/duration of action.
Salbutamol, terbutaline
Onset of 1-5 minutes
Duration of 4-6 hours
Give examples of long acting beta agonists and their onset/duration of action.
Formeterol Onset 1-3 minutes Salmeterol Onset 10-20 minutes Duration of 12 hours
Give side effects of beta-agonists.
Fine tremor
Headache
Tachycardia
What is the MOA of corticosteroids?
Bind glucocorticoid receptors to dissociate heat shock proteins and allow receptors to travel to the nucleus where they bind to DNA blocking genes that code for cytokines for inflammation.
Give examples of inhaled corticosteroids.
Beclomethasone
Budesonide
Give examples of oral corticosteroids.
Prednisolone
Give examples of IV corticosteroids.
Hydrocortisone
What are the criteria for corticosteroid indication.
Exacerbation in the last 2 years
Using SABA at least twice weekly
Waking with symptoms once per week
What are the side effects of corticosteroids?
Oral candidiasis Hoarseness Adrenal suppression Skin thinning Cushing's
What is the MOA of leukotriene antagonists?
Antagonise broncho-constriction, reducing mucus secretion and airway oedema
Give examples of leukotriene antagonists.
Montelukast
Zafirlukast
What are the side effects of leukotriene antagonists?
Abdominal pain
Thirst
Headache
What are methylxanthines?
PDE inhibitors that prevent the breakdown of cAMP, preventing broncho-constriction
Give examples of methylxanthines.
Theophylline
Aminophylline
Why are leukotriene antagonists not 1st choice drugs in asthma? Give two reasons
Not as effective as beta-agonists
Side effect of thirst can increase risk of bedwetting in children
Why are methylxanthines not 1st choice drugs in asthma?
Narrow therapeutic window of 10-20mg/L
What are the side effects of methylxanthines with a dose over 20mg/L?
Insomnia
Arrhythmia
Hyperglycaemia
Convulsions
What are PDE4 inhibitors?
Reduce production of matrix metallaproteinase, enhancing effects of beta-2 agonists
Give an example of a PDE4 inhibitor.
Roflumilast
When are PDE4 inhibitors indicated?
Severe persistent COPD associated with chronic bronchitis
What are the side effects of PDE4 inhibitors?
Diarrhoea
Abdominal pain
Unexplained weight loss
What is the mechanism of action of monoclonal antibodies in asthma?
Inhibit IgE binding to mast cell receptors, thus reducing inflammation
Give an example of monoclonal antibodies used in asthma. What is the regimen?
Omalizumab SC every 2-4 weeks
Discontinued after 16 weeks if no adequate response is seen
Give examples of immunosuppressants that may be used by specialists in asthma.
Cyclosporin
Methotrexate
Gold
What are analeptics?
Stimulate chemoreceptors in carotid and aortic bodies to increase respiratory work rate
Give an example of an analeptic.
Doxapram
When are analeptics used?
Post-operative respiratory depression
Ventilatory failure in COPD
Apnoea in neonates
Why is caffeine useful in respiratory disease?
It is a phosphodiesterase inhibitor, increasing levels of cAMP and promoting effects of beta-adrenoceptors
What are cromones? Give an example.
Nedocromil
Mast cell stabilisers, work to reduce inflammation
What is the role of carotid and aortic chemoreceptors?
Activated by increased carbon dioxide levels in the blood increasing respiratory rate and workload
What is the normal level of carbon dioxide in ventilation?
40mmHg
What is the role of acetylcholine at M3 receptors in respiration?
Increases intracellular calcium ion levels
Interaction with calmodulin activates myosin light chain kinase
Kinase phosphorylates myosin leading to contraction
What occurs upon activation of beta-2 adrenoceptors?
Stimulates adenylyl cyclase, increasing production of cAMP
Protein kinase A activates to phosphorylate proteins acting to reduce intracellular calcium
Reduces activity of MLCK, causing relaxation of airway muscles
What is allergic asthma?
Hyper-responsiveness to stimulus causing broncho-constriction and mucus secretion that is reversible
Give examples of triggers of asthma.
Stress Cold Allergens Exercise Infection
How do dust mites cause allergic asthma?
Release of casts, secretions and enzymes
What occurs in the initial phase of asthma?
Occurs abruptly due to spasm
Allergen interacts with mast cell IgE releasing histamine, leukotriene B4 and prostaglandin D2
Interleukins, TNF and macrophage proteins also released into airway
Chemotaxins attract eosinophils to trigger late phase
What occurs in the late phase of asthma?
Allergens interact with dendritic and CD4 cells leading to ThO cell development, leading to Th2 clones
B cells produce IgE
IL-5 activates eosinophils
Cytokines induce IgE receptor expression
Eosinophils release cysteine leukotrienes, interleukins and toxic proteins which cause damage to epithelium
Inflammatory mediators include adenosine, NO and neuropeptides
What is intrinsic asthma?
Occurs later in life due to precipitating factors such as inhalation of irritants or pollutants
Chronic and persistent symptoms
What is the cause and action of COPD?
Exposure to irritants causing epithelial cells to release factors activating neutrophils
CD8, B cell and macrophage accumulation accumulation
Inflammatory cascade causes mediator release- TNF, interferon, MMP, interleukins
What causes damage in COPD?
Inflammation is sustained and causes tissue damage and systemic effects
MMPs destroy elastin fibres causing proteolytic degredation
What is COPD characterised by?
Airflow obstruction that is not fully reversible
Does not changed markedly over several months but progressive in the long term
FEV1/FVC ratio <70%
What are the risk factors of COPD?
Smoking
Age
Alpha-1 antitrypsin deficiency
Occupation
What does COPD present with?
Exertional breathlessness
Chronic cough
Regular sputum production
Wheeze
What is the BODE index?
Measure of COPD based on: BMI Obstruction Dyspnoea Exercise capacity
What are the side effects of anti-muscarinics?
Dry mouth
Urinary retention
Blurred vision
How can methylxanthines improve COPD symptoms?
Strengthen diaphragm
Increase mucociliary clearance
What are mucolytics used for?
Reduce mucus viscosity making it easier to clear and reducing obstruction
When is oxygen given in COPD?
Long term where FEV1 <35% and oxygen sats <92%
24-28% oxygen given >15 hours per day
What are the common causes of infective exacerbations of COPD?
Streptococcus pneumoniae
Haemophilus influenzae
What is the first line treatment of infective exacerbations of COPD?
Amoxicillin 500mg
OR tetracycline 100mg with 200mg doxycycline stat
Given alongside 30mg prednisone for 7-14 days
What is the second line treatment of infective exacerbations of COPD?
Broad spectrum cephalosporin or macrolide
What is hypercapnia?
Abnormally high carbon dioxide levels
What is cor pulmonale?
Right side heart failure due to pulmonary hypertension
What is polycythaemia?
Increase in RBCs due to chronic hypoxia, increasing blood viscosity
