Respiratory Flashcards
What centres and receptors are involved in respiration?
- Central regulatory centres
- Central and peripheral chemoreceptors
- Pulmonary receptors
where are three respiratory regulatory centres?
- Medullary respiratory centre
- Apneustic centre (lower pons)
- Pneumotaxic centre (upper pons)
Describe how central and peripheral chemoreceptors cause respiration?
- Central: raised [H+] in ECF stimulates respiration
* Peripheral: carotid + aortic bodies, respond to raised pCO2 & [H+], lesser extent low pO2
Describe the three types of pulmonary receptors and how these affect respiration?
- Stretch receptors, lung distension causes slowing of respiratory rate (Hering-Bruer reflex)
- Irritant receptor, leading to bronchoconstriction
- Juxtacapillary receptors, stimulated by stretching of the microvasculature
What is the ‘chloride shift’ in respiration?
- CO2 diffuses into RBCs
- CO2 + H2O —- carbonic anhydrase -→ HCO3- + H+
- H+ combines with Hb
- HCO3- diffuses out of cell,- Cl-replaces it
What is the bohr effect?
• Increasing acidity (or pCO2) means O2 binds less well to Hb
What is the haldane effect?
• ↑ pO2 means CO2 binds less well to Hb
what does tidal volume mean? how much is it males/female?
- Volume inspired or expired with each breath at rest
* 500ml in ♂s, 350ml in ♀s
What is the inspiratory reserve volume in L? what volume is this?
Inspiratory Reserve Volume (IRV) = 2-3 L
• Maximum volume of air that can be inspired after normal tidal inspiration
• Inspiratory capacity = TV + IRV
what is the Expiratory Reserve Volume (ERV) in L? what does this mean?
Expiratory Reserve Volume (ERV) = 750ml
• Maximum volume of air that can be expired after normal tidal expiration
what is the residual volume? how much is this in L?
Residual volume (RV) = 1.2L
• Volume of air remaining after maximal expiration
• ↑ with age
• RV = FRC – ERV (Functional Residual Capacity - Expiratory Reserve Volume)
what is the vital capacity? how much is this in L?
Vital Capacity (VC) = 5L • Maximum volume of air that can be expired after a maximal inspiration • 4,500ml in ♂s, 3,500 mls in ♀s • ↓ with age • VC = IC + ERV
What is FVC?
forced vital capacity
This is the volume of air that can forcibly be blown out after full inspiration, measured in liters.
What is FEV1?
Forced expiratory volume in 1 second
This is the maximum volume of air that can forcibly blow out in the first second during the FVC manoeuvre, measured in liters. Along with FVC it is considered one of the primary indicators of lung function.
What is the FEV1/FVC
This is the ratio of FEV1 to FVC. In healthy adults this should be approximately 75–80%.
What is the PEF?
Peak expiratory flow
This is the maximal flow (or speed) achieved during the
maximally forced expiration initiated at full inspiration,
measured in liters per second.
what is FEF 25–75% or 25–50%?
Forced expiratory flow 25-75% or 25-50%
This is the average flow (or speed) of air coming out of the lung during the middle portion of the expiration (also sometimes referred to as the MMEF, for maximal mid-expiratory flow).
What is FIF 25–75% or 25–50%?
This is similar to FEF 25–75% or 25–50% except the
measurement is taken during inspiration.
What is FET?
Forced Expiratory Time This measures the length of the expiration in seconds.
What is SVC?
Slow Vital capacity
Maximum volume of air that can be exhaled slowly after slow maximum inhalation.
What is MVV?
Maximum Voluntary Ventilation
A measure of the maximum amount of air that can be inhaled and exhaled in one minute, measured in liters/minute.
What is FRC?
functional residual capacity FRC The amount of air left in the lungs after a tidal breath out. The amount of air that stays in the lungs during normal breathing. ERV+RV = 2.4 / 1.9 L
What happens in PFTS in obstructive lung disease?
FEV1 - significantly ↓
FVC - ↓ or normal
(FEV1/FVC) - ↓
What happens in PFTs in restrictive lung disease?
FEV1 - ↓
FVC - significantly ↓
(FEV1/FVC) - normal or ↑
what is lung compliance?
is defined as change in lung volume per unit change in airway pressure
what are 2 causes of increased compliance?
Causes of ↑ compliance
• Age
• Emphysema
What are causes of decreased compliance in the lungs?
Causes of ↓ compliance • Pulmonary edema • Pulmonary fibrosis • Pneumonectomy • Kyphosis
Describe what happens to Hb saturations if the oxygen saturation curve shifts right?
Shifts to right = for given oxygen tension there is ↓ saturation of Hb with oxygen i.e. Enhanced
oxygen delivery to tissues
Left shift of the curve is a sign of hemoglobin’s ↑ affinity for oxygen (eg. at the lungs). Similarly, right
shift shows ↓ affinity,
Describe what happens to Hb saturations if the oxygen saturation curve shifts left?
Shifts to left = for given oxygen tension there is ↑ saturation of Hb with oxygen i.e. ↓ oxygen
delivery to tissues
Left shift of the curve is a sign of hemoglobin’s ↑ affinity for oxygen (eg. at the lungs). Similarly, right
shift shows ↓ affinity,
Describe 4 things that shift oxygen dissociation right?
Shifts to Right = Raised oxygen delivery • Raised [H+] (acidity) • Raised PCO2 • Raised 2,3-DPG • Raised temperature
Describe 5 things that shift oxygen dissocation left?
Shifts to Left = Lower oxygen delivery • HbF, methemoglobin, carboxyhemoglobin • Low [H+] (alkali) • Low PCO2 • Low 2,3-DPG • Low temperature
What is transfer factor?
The transfer factor describes the rate at which a gas will diffuse from alveoli into blood. Carbon
monoxide is used to test the rate of diffusion. Results may be given as the total gas transfer (TLCO) or
that corrected for lung volume (transfer coefficient, KCO)
what are 6 causes for a raised TLCO?
Causes of a raised TLCO • Asthma • Pulmonary hemorrhage (wegener's, goodpasture's) • Left-to-right cardiac shunts • Polycythemia • Hyperkinetic states • ♂ gender, exercise
what are 7 causes for a low TLCO?
Causes of a lower TLCO • Pulmonary fibrosis • Pneumonia • Pulmonary emboli • Pulmonary edema • Emphysema • Anemia • Low cardiac output
what conditions may cause ↑ KCO with a normal or ↓ TLCO?
KCO also tends to ↑ with age (used to diagnose or R/O interstitial lung disease). Some conditions may
cause ↑ KCO with a normal or ↓ TLCO
• Pneumonectomy/lobectomy
• Scoliosis/kyphosis
• Neuromuscular weakness
• Ankylosis of costovertebral joints e.g. Ankylosing spondylitis
what happens to pulmonary arteries in the presence of hypoxia?
A fall in the partial pressure of oxygen (pO2) in the blood leads to vasoconstriction of the pulmonary
arteries. This allows blood to be divered to better aerated areas of the lung and improves the efficiency
of gaseous exchange
describe some contraindications to thoracentesis?
An uncooperative patient or coagulation disorders that can not be corrected are absolute
contraindications.
Relative contraindications include cases in which the site of insertion has known bullous disease (e.g. emphysema), use of positive end-expiratory pressure (PEEP, in mechanical ventilation) and only one functioning lung (due to diminished reserve). The aspiration should not exceed 1L as there is a risk of development of pulmonary edema.
name some causes of asthma
The following can cause Asthma: • Isocyanates - the most common cause. Example occupations include spray painting and foam moulding using adhesives • Platinum salts • Soldering flux resin • Glutaraldehyde • Flour • Epoxy resins • Proteolytic enzymes
describe features that would increase the probability of asthma diagnosis
• Wheeze, breathlessness, chest tightness and
cough, worse at night/early morning
• History of atopic disorder
• Wheeze heard on auscultation
• Unexplained peripheral blood eosinophilia
describe some features that would reduce the probability of asthma
• Prominent dizziness, light-headedness, peripheral
tingling
• Chronic productive cough in the absence of
wheeze or breathlessness
• Repeatedly normal physical examination
• Significant smoking history (i.e. > 20 pack-years)
• Normal PEF or spirometry when symptomatic
What investigation would you do if a patient had an intermediate probability of asthma?
For patients with an intermediate probability of asthma further investigations are suggested. The
guidelines state that spirometry is the preferred initial test:
• FEV1/FVC < 0.7: trial of treatment
• FEV1/FVC > 0.7: further investigation/consider referral
When would a >400ml improvement in FEV1 be significant?
A > 400 ml improvement in FEV1 is considered significant
• Before and after 400 mcg inhaled salbutamol in patients with diagnostic uncertainty and airflow
obstruction present at the time of assessment
• If there is an incomplete response to inhaled salbutamol, after either inhaled corticosteroids
(200 mcg twice daily beclomethasone equivalent for 6-8 weeks) or oral prednisolone (30 mg
once daily for 14 days)
How is peak flow interpreted in Asthma?
It is now advised to interpret peak flow variability with caution due to the poor sensitivity of the test
• Diurnal variation % = [(Highest – Lowest PEFR) / Highest PEFR] x 100
• Assessment should be made over 2 weeks
• Greater than 20% diurnal variation is considered significant
How is complete control of asthma defined as?
The aim of asthma management is control of the disease. Complete control is defined as:
• no daytime symptoms
• no night-time awakening due to asthma
• no need for rescue medication
• no asthma attacks
• no limitations on activity including exercise
• normal lung function (in practical terms FEV1 and/or PEF >80% predicted or best)
• minimal side effects from medication.
Describe the inital therapy for asthma
Prescribe an inhaled short-acting β2 agonist as short-term reliever therapy for all patients with symptomatic asthma.
Inhaled corticosteroids are the recommended preventer drug for adults and children for achieving overall treatment goals.
Give inhaled corticosteroids initially twice daily (except ciclesonide which is given once daily).
Once-a-day inhaled corticosteroids at the same total daily dose can be considered if good control is established.
Clinicians should be aware that higher doses of inhaled corticosteroids may be needed in patients who are smokers or ex-smokers
Describe the initial add on therapy for asthma after initial therapy is established
SABA + low-dose ICS + leukotriene receptor antagonist (LTRA)
Describe the secondary add on therapy for asthma after initial therapy has started and initial add on therapy has been trialled
SABA + low-dose ICS + long-acting beta agonist (LABA)
Continue LTRA depending on patient’s response to LTRA
what should be considered in patients which excersize is a specific problem in asthma?
If exercise is a specific problem in patients taking inhaled corticosteroids who are otherwise well controlled, consider adding one of the following therapies:
• leukotriene receptor antagonists
• long-acting β2 agonists
• sodium cromoglicate or nedocromil sodium • theophyllines.
Immediately prior to exercise, inhaled short-acting β2 agonists are the drug of choice.
Describe the stages of COPD
1 - mild FEV1 >80% of predicted
2- moderate FEV1 50-80%
3- severe 30-49% FEV1
4- very severe <30% FEV1
What vaccinations are used in COPD?
- Annual influenza vaccination
* Pneumococcal vaccination
What is the initial COPD therapy
Bronchodilator therapy
• Short-acting β2-agoinst (SABA) or short-acting muscarinic antagonist (SAMA) is 1st line Rx.
Salbutamol/ipratropium
How is further management of COPD after inital therapy determined?
FEV1
If the FEV1 is more than 50% but patient is still need add on COPD therapy what can be used?
• Long-acting β2-agoinst (LABA), for
example salmeterol, or:
• Long-acting muscarinic antagonist
(LAMA), for example tiotropium
If the FEV1 is less than 50% in COPD what is the further treatment?
FEV1 < 50% (stage III and IV)
• LABA + inhaled corticosteroid (ICS) in a
combination inhaler, or:
• LAMA
when should oral theophylline be used in COPD?
• NICE only recommends theophylline after trials of short and long-acting bronchodilators or to
people who cannot use inhaled therapy
• The dose should be reduced if macrolide or fluroquinolone antibiotics are coprescribed
What are the features of cor pulmonale?
• Features include peripheral oedema, raised
JVP, systolic parasternal heave, loud P2
• Use a loop diuretic for oedema, consider
long-term oxygen therapy
• ACE-inhibitors, calcium channel blockers
and alpha blockers are NOT recommended
by NICE
When should COPD patients be assessed for LTOT?
The 2010 NICE guidelines on COPD clearly define which patients should be assessed for and offered long-term oxygen therapy (LTOT). Patients who receive LTOT should breathe supplementary oxygen for at least 15 hours a day. Assess patients if any of the following: • Very severe airflow obstruction (FEV1 < 30% predicted). Assessment should be 'considered' for patients with severe airflow obstruction (FEV1 30-49% predicted) • Cyanosis • Polycythaemia • Peripheral oedema • Raised jugular venous pressure • Oxygen saturations ≤ 92% on room air
What is included in the assessment of COPD patients for LTOT?
Assessment is done by measuring arterial blood
gases on 2 occasions at least 3 weeks apart in
patients with stable COPD on optimal
management.
Offer LTOT to patients with a pO2 of < 7.3 kPa or
to those with a pO2 of 7.3 - 8 kPa and one of the
following:
• Secondary polycythaemia
• Nocturnal hypoxaemia
• Peripheral oedema
• Pulmonary hypertension
What are the benefits of LTOT?
• ↓ secondary polycythemia
• ↓ sympathetic activity → ↓ cardiac
arrhythmia
• Improve sleep quality
what is emphysema? what is seen on PFTs?
Emphysema is an irreversible degenerative
condition; it is a known complication of COPD.
• ↑ Residual Volume (RV)
• ↑ Total Lung Capacity (TLC)
• Giving typical obstructive pathology
what is seen on CXR of patients with emphysema?
- Flattening of diaphragms: ↑ lung volumes
- Enlarged left pulmonary artery
- Attenuation of vessels
- Diffuse hyperlucency
what is panacinar emphysema?
Panacinar (panlobular): entire respiratory
acinus, from respiratory bronchiole to alveoli,
is expanded. > In the lower lobes.
what is centriacinar emphysema?
Centriacinar (centrilobular): respiratory
bronchiole (proximal and central part of the
acinus) is expanded. The distal acinus or
alveoli are unchanged. > In the upper lobes.
What is congenital lobar emphysema?
Congenital lobar emphysema (CLE): results in
overexpansion of a pulmonary lobe and
resultant compression of the remaining lobes of
the ipsilateral lung, and possibly contralateral
lung. There is bronchial narrowing because of
weakened or absent bronchial cartilage. There
may be congenital extrinsic compression,
commonly by an abnormally large pulmonary
artery. CLE is potentially reversible, yet
possibly life-threatening, causing respiratory
distress in the neonate.
what is paraseptal emphysema?
Paraseptal emphysema: involves the alveolar
ducts and sacs at the lung periphery. The
emphysematous areas are subpleural in
location and often surrounded by interlobular
septa (hence the name). It may be an incidental finding in young adults, and may be associated
with spontaneous pneumothorax. It may also
be seen in older patients with centrilobular
emphysema. Both centrilobular and paraseptal
emphysema may progress to bullous
emphysema.
What is emphysematous bulla?
Emphysematous Bulla is defined as being at least
1 cm in diameter, and with a wall less than 1mm
thick. Bullae are thought to arise by air trapping in
emphysematous spaces, causing local expansion
How do you manage COPD patients in the acute scenario with oxygen?
Prior to the availability of blood gases, use a 28% Venturi mask at 4 l/min and aim for an
oxygen saturation of 88-92% for patients with risk factors for hypercapnia but no prior history
of respiratory acidosis
• Adjust target range to 94-98% if the pCO2 is normal
what are the 4 indications for NIV AKA bipap
Non-invasive ventilation - key indications
• COPD with respiratory acidosis pH 7.25-7.35
• Type II respiratory failure secondary to chest wall deformity, neuromuscular disease or
obstructive sleep apnoea
• Cardiogenic pulmonary edema unresponsive to CPAP
• Weaning from tracheal intubation.
What are the Recommended initial settings for bi-level pressure support in COPD:
- EPAP
- IPAP
- Fi02
- back up rate
- back up inspiration:expiration ratio
- keep SP02 between?
• Expiratory Positive Airway Pressure (EPAP): 4-5 cm H2O
• Inspiratory Positive Airway Pressure (IPAP): RCP advocate 10 cm H20 whilst BTS suggest 12-
15 cm H2O
• FiO2: not > 40%
• Back up rate: 15 breaths/min
• Back up inspiration:expiration ratio: 1:3
• Keep SpO2: 88-92%
• ABG every 1-2 hours
Is V/Q scan for PE sensitive? specific?
what are other causes of V/Q mismatch?
• Sensitivity = 98%; specificity = 40% - high negative predictive value, i.e. If normal virtually
excludes PE
• Other causes of mismatch in V/Q include:
o Old pulmonary embolisms
o AV malformations
o Vasculitis
o Previous radiotherapy
• COPD gives matched defects
What is a limitation of CTPA?
Peripheral emboli affecting subsegmental arteries may be missed
What should all asthma patients be investigated with?
patients should be asked if their symptoms are better on days away from work/during holidays. If so, patients should be referred to a specialist as possible occupational asthma
all patients should have spirometry with a bronchodilator reversibility (BDR) test
all patients should have a FeNO test
What are the causes for upper zone fibrosis?
C - Coal worker's pneumoconiosis
H - Histiocytosis/ hypersensitivity pneumonitis
A - Ankylosing spondylitis
R - Radiation
T - Tuberculosis
S - Silicosis/sarcoidosisWhat are the causes of lower zone fibrosis?
idiopathic pulmonary fibrosis
most connective tissue disorders (except ankylosing spondylitis) e.g. SLE
drug-induced: amiodarone, bleomycin, methotrexate
asbestosis
What antibiotic is recommended for COPD patients?
azithromycin prophylaxis is recommended in select patients
other prerequisites include a CT thorax (to exclude bronchiectasis) and sputum culture (to exclude atypical infections and tuberculosis) LFTs and an ECG to exclude QT prolongation should also be done as azithromycin can prolong the QT interval
How long should anticoag be continued for in patients with transient risk factors?
3 months
How long should anticoag be continued for in patients with permanent risk factors or idiopathic?
6 months
what are 5 organisms which cause CAP
- Streptococcus pneumoniae (accounts for around 80% of cases)
- Hemophilus influenzae
- Staphylococcal aureus
- Atypical pneumonias (e.g. due to Mycoplasma pneumoniae)
- Viruses
what can strep. pneumoniae cause? what is it assoc. with?
Streptococcus pneumoniae commonly causes reactivation of the herpes simplex virus resulting in ‘cold sores and associated with foreign travel
Who does klebsiella pneumoniae affect classically? what cxr appearances may be seen? what is the mortality?
Klebsiella pneumoniae (Friedlander's pneumonia) is classically in alcoholics. CXR features may include abscess formation in the middle/upper lobes and empyema. The mortality approaches 30-50%
what are 4 characteristic features of pneumococcal pneumonia
Characteristic features of pneumococcal pneumonia • Rapid onset • High fever • Pleuritic chest pain • Herpes labialis
