Breathlessness Flashcards
What is hypoxaemia? also known as hypoxic hypoxia
abnormally low arterial partial pressure of oxygen
it is associated with clinical sign of central cyanosis
what is hypoxia
defined as low tissue partial pressure of oxygen either due to a reduction of the supply of oxygen or the inability to use it
results in organ/tissue dysfunction and even cell death
What is the difference between PAO2 and PaO2?
how do you measure them?
A: alveolar oxygen pressure
a: arterial oxygen pressure
A: calculated using alveolar gas equation
a: measured by performing an arterial blood gas analysis
PAO2 - PaO2 difference in normal individuals
healthy young adults about 2kPa
elderly about 5kPa
5 causes of hypoxaemia explained
mechanism, notes, PaO2, Aa difference, does O2 help?
1) Mechanism: high altitude (climbing Everest)
Notes: fall in barometric pressure leads to an increase inspired O2 tension (PIO2) and PAO2
PaO2: decreases
Aa difference: normal
does O2 help?:yes
2) mechanism : hypoventilation (e.g. opioid overdose)
notes: decreased alveolar ventilation “pump failure” leads to a decrease in PAO2 and an increase in PACO2
PaO2: decreased
Aa difference: normal
does O2 help? yes
3) mechanism: diffusion defect (e.g. fibrosis)
notes: leads to a decrease in PaO2
PaO2: decreases
Aa difference: increased
does O2 help: yes
4) mechanism: V/Q mismatch (e.g. PE)
notes: leads to a decrease in PaO2, PACO2 is low or normal
PaO2: decreases
Aa difference: increased
does O2 help: yes
5)mechanism: right to left cardiac shunt (e.g.congenital cyanotic heart disease
notes: hunted blood bypasses the alveoli and cannot be oxygenated resulting in a very low PaO2
PaO2: decreases
Aa difference: increased
Does O2 help? limited effect, only upon non-shunted blood
when should you suspect hypoxia
anxiety euphoria confusion/poor judgement/ irritability lack of coordination tachypnoea, use of accessory muscles tunnel-vision loss of consciousness, coma seizures
alveolar ventilation equation
VA= R(VT-VD) where R is respiratory rate, VT is tidal volume, and VD is dead space volume.
clinical features of type II respiratory failure
vary according to underlying cause
headache (cerebral vasodilation)
flapping tremor of the wrist
Bounding pulse
Describe a negative feedback loop for acidaemia, hypercapnia and hypoxia
those are the stimuli
the receptors are central and peripheral chemoreceptors
the control centre is located in the brainstem, medulla oblongata
the effectors are muscles of the respiratory system that pump to either increase or decrease alveolar ventilation
Describe the MRC Dyspnoea scale
grade 1 - not troubled by breathlessness except on strenuous exercise
grade 2 - short of breath on hurrying or walking up a slight hill
grade 3 - walks slower than others on level ground, or has to stop for breath when walking at own pace
grade 4 - stops for breath after 100m or after a few mins on level ground
grade 5 - too breathless to leave house, or breathless when dressing/undressing
what is stridor
high-pitched, wheezing sound caused by disrupted airflow. Stridor may also be called musical breathing or extrathoracic airway obstruction.
different types of stridor
inspiratory stridor: only hear it when breathing in - indicates an issue with the tissue above the vocal chords
expiratory stridor: only hear it when breathing out - indicates a blockage in the windpipe
biphasic stridor: causes abnormal sound when they breathe in and out - caused by narrowing of cartilage near the vocal chords
what causes stridor in adults
object blocking airway swelling in throat or upper airway bronchitis tonsilitis tracheal stenosis tumors etc.
what causes a wheeze
happens when the airways are tightened, blocked, or inflamed, making a person’s breathing sound like whistling or squeaking. Common causes include a cold, asthma, allergies, or more serious conditions, such as chronic obstructive pulmonary disease (COPD).
basic description of a pneumothorax
is a collapsed lung. A pneumothorax occurs when air leaks into the space between your lung and chest wall. This air pushes on the outside of your lung and makes it collapse. A pneumothorax can be a complete lung collapse or a collapse of only a portion of the lung.
causes of a pneumothorax
chest injury - blunt or penetrating trauma
lung disease - diseased lungs are more likely to collapse
ruptured air blisters (called blebs) when they burst they allow air to seep into space between lungs and lining causing a pneumothorax (associated with tall underweight people)
mechanical ventilation - when a ventilation device causes an imbalance of air pressure within the chest (very serious)
difference between pneumothorax and tension pneumothorax
both is air between the parietal and visceral pleura
difference is in a tension pneumo there is a mediastinal shift
briefly describe cardiac tamponade
happens when extra fluid builds up around the space of the heart - fluid puts pressure on the heart and prevents it from pumping properly
(A fibrous sac called the pericardium surrounds the heart. This sac is made up of 2 thin layers. Normally, a small amount of fluid if found between the 2 layers. The fluid prevents friction between the layers when they move as the heart beats. In some cases, extra fluid can build up abnormally between these 2 layers. If too much fluid builds up, the extra fluid can make it hard for the heart to expand normally. Because of the extra pressure, less blood enters the heart from the body. This can reduce the amount of oxygen-rich blood going out to the body.
If the fluid builds up around the heart too quickly, it can lead to short-term (acute) cardiac tamponade. It’s life-threatening if not treated right away. Another type of cardiac tamponade (subacute) can happen when the fluid builds up more slowly. This is also life-threatening.)
describe carbon monoxide poisoning
Carbon monoxide poisoning occurs when carbon monoxide builds up in your bloodstream. When too much carbon monoxide is in the air, your body replaces the oxygen in your red blood cells with carbon monoxide. This can lead to serious tissue damage, or even death.
deadly forms of cyanide
sodium cyanide
potassium cyanide
hydrogen cyanide
cyanogen chloride
different ways to classify HF
acute vs chronic left vs right systolic vs diastolic forward vs backward low output vs high output
HF definition
an inability of the heart to maintain an adequate perfusion of the tissues (cardiac output) at a normal filling pressure (CVP/JVP)
it is not a diagnosis
it is a syndrome of signs and symptoms that may be caused by a variety of pathological conditions
difference between chronic HF and hypovolaemic shock
blood volume, JVP, Pulse rate, BP, CO, TPR, timing, immediate danger to life?
Blood volume: HF ↑, hypo ↓ JVP: HF↑, Hypo↓ Pulse rate: HF⇔, hypo ↑ BP: HF↑or⇔, hypo↓ CO: HF↓, hypo↓ TPR: HF↑, hypo↑↑ timing: HF chronic, Hypo acute Immediate danger to life: HF no, hypo yes
pathophysiology of chronic left sided heart failure
systolic dysfunction: impaired emptying due to reduced contractility or/and increased after load
diastolic dysfunction: impaired ventricular relaxation or obstruction due to filling
describe systolic dysfunction in HF
diminished capacity of the ventricle to eject blood because of reduced contractility and/or excessive afterload
then end-systolic volume is increased due to the reduction in stroke volume and ejection fraction
what conditions lead to impaired contractility (HF)
MI or ischaemia
dilated cardiomyopathy
Chronic volume overload (e.g. mitral or aortic regurgitation)
Talk through aortic stenosis
narrowing of the aortic valve outlet
may result in slow rising pulse and ejection systolic murmur head on auscultation in the aortic area (second right intercostal space) and radiating to the carotids
what is meant by an ejection systolic murmur
Systolic means when the heart muscle contracts
ejection means because of blood flow through a narrowed or damaged valve
whereas a regurgitant murmur is because of back flow of blood into one of the chamber of the heart
Aortic stenosis on auscultation
type of murmur, where is it heard loudest, quality?, what can you make a patient do to hear it better?
ejection systolic murmur
heard loudest over aortic area (2nd right intercostal space)
has a crescendo-decrescendo quality
loudest on expirations and when a patient is leaning forward
mitral regurgitation on auscultation(type of murmur, loudest over?, radiation to?)
pan systolic murmur
loudest over mitral area (fifth left intercostal space mid-clavicular line)
radiation of murmur to axilla
pan systolic means: A murmur extending through the entire systolic interval, from the first to the second sound.
pulmonary stenosis on auscultation
ejection systolic murmur
heard loudest over pulmonary area
loudest during inspiration
radiates to left shoulder
describe diastolic dysfunction (filling) in HF
increased stiffness (reduced compliance) of the ventricle impairs filling during diastole (e.g. fibrosis or hypertrophy of ventricular wall or constriction by pericardium)
define cor pulmonale
right sided heart failure due to hypoxic lung disease (e.g. COPD)
Cor pulmonale is a condition that happens when a respiratory disorder results in high blood pressure in the pulmonary arteries (pulmonary hypertension). The name of the condition is in Latin and means “pulmonary heart.”
It’s also known as right-sided heart failure because it occurs within the right ventricle of your heart. Cor pulmonale causes the right ventricle to enlarge and pump blood less effectively than it should. The ventricle is then pushed to its limit and ultimately fails.
signs of Cor pulmonale
nicknamed blue bloater
central cyanosis raised JVP pitting oedema hepatomegaly parasternal heave (RVH) tricuspid regurgitation
compensatory mechanisms in chronic heart failure
- increased renal salt and water retention leading to increased filling pressure (↑JVP) and stroke volume by Frank-Starling mechanism
- baroreceptor reflex increases sympathetic tone increasing HR and contractility and producing increased peripheral vasoconstriction
- LVH and remodelling
_all this results in fatigue, and poor exercise tolerance
what is the release of renin stimulated by (think HF) in the renin-angiotensin-aldosterone system
1) reduced renal artery pressure secondary to the fall in CO
2) increased renal sympathetic tone (due to baroreceptor reflex)
detrimental effects of increased filling pressures in the heart (think HF)
- dilated heart is less efficient at contracting (law of Laplace)
- widening of AV valve orifices leads to regurgitation of blood through valves
- increased filling pressure of left ventricle leads to pulmonary oedema and breathlessness
- increased filling pressure of right ventricle leads to peripheral pitting oedema
increased sympathetic tone in HF friend or foe?
beneficial in mild HF but in more severe disturbances the effects may be detrimental:
- venoconstriction raises the filling pressure
- vasoconstriction leads to increase in afterload and hence myocardial oxygen consumption
- uncoupling
What are other signalling molecules increased in the plasma in heart failure
ADH - promotes water retention by the kidney
BNP (B type natriuretic peptide)- produced by failing myocardium, plasma level correlates with degree of severity, used as a biomarker
how does cardiac failure produce oedema? (starling forces)
increased venous filling pressure leads to an increase in capillary pressure
salt and water retention leads a reduction in the concentration of proteins in plasma and thus a decrease in the colloid osmotic pressure of plasma
these lead to an increase in the production of tissue (interstitial) fluid by capillaries by ultrafiltration
if you suspect heart failure what four things should you ask about
- dyspnoea -difficult or laboured breathing (due to pulmonary venous congestion)
- orthopnoea - SOB or difficulty breathing when lying flat
- PND - paroxysmal nocturnal dyspnoea -SOB that awakens the patient after 1-2 hours of sleep
- Fatigue
4 signs of acute left ventricular failure (LVF)
- tachypnoea - fast breathing - due to stimulation of J receptors
- cold hands - due to increased sympathetic tone
- tachycardia - due to increased sympathetic tone
- crackles or wheeze - due to pulmonary oedema
describe the abnormal heart sounds you would hear in patients in LVF (left ventricular failure)
combination of added heart sounds and tachycardia produces a “gallop rhythm”
S3 (early diastole) - abnormal filling of dilated ventricles
S4 (late diastole ) - atrial contraction against stiff ventricle
describe the therapeutic strategies in LVF (Left ventricular failure)
- Remove underlying cause if possible
- Give supplemental oxygen and consider CPAP or NIPPV
- Use loop diuretics to improve mechanical efficiency by reducing cardiac dilatation and filling pressures
- Reduce cardiac work by reducing after load (e.g. nitrate vasodilators)
- . LVAD only available in specialist cardiac units
5 causes of high output cardiac failure (what they are, describe them, how it produces high output cardiac failure)
1) Severe anaemia - blood contains too few oxygen carrying RBCs - requires heart to pump more blood each minute to deliver enough oxygen to the tissues
2) hyperthyroidism - thyroid gland produces too much thyroid hormone - increases body’s overall metabolism thus increasing demand for blood flow
3) arteriovenous fistula - abnormal connection between an artery and a vein - short circuits the circulation and forces the heart to pump more blood overall to deliver the usual amount of blood to the vital organs
4) Beriberi - deficiency of thiamine (vitamin B1) - leads to increased metabolic demand and increased need for blood flow
5) Paget’s disease - abnormal breakdown and regrowth of bones which develop an excessive amount of blood vessels - increased number of blood vessels require an increased cardiac output
which comes first right or left sided heart failure
left sided heart failure as right sided heart failure usually occurs as a result of LHF
(4) possible pathologies in the lungs (airways and parenchyma) that cause SOB
asthma
pneumonia / chest infection
pneumothorax
heart failure
6 investigations to do with SOB as presenting complaint (thinking lungs) (thinking bloods)
FBC - full blood count BNP - B natriuretic peptide U&E - urea and electrolytes D-dimer ABG - arterial blood gas CRP - C reactive protein
(BNP high in hypoxia because heart has to work hard to pump under oxygenated blood around)
why do a BNP test when someone is presenting with SOB
used in the diagnosis of heart failure
Why do U&Es when someone is presenting with SOB
acute kidney injury could cause raised urea and creatinine which could lead to pulmonary oedema
low potassium levels if on salbutamol inhaler (not for diagnosis but important to monitor)
why do a D-dimer when someone is presenting SOB
to diagnose PE/DVT
why do CRP when someone is presenting SOB
for respiratory acidosis/alkalosis
A moderately elevated CRP value (10-60 mg/l) is a common finding in viral upper respiratory tract infection, with a peak during days 2-4 of illness.
What is CRP raised in?
In inflammation
requirement levels of BNP for unlikely HF, referral needed and urgent referral needed
unlikely - <300pg/mL
referral - >400pg/mL
urgent - >2000pg/mL
how to test for CO poisoning
can do breath test but levels decline quickly after source is removed
has a half life of 300 mins so can be detected in the blood
investigations to do if you think circulation is the cause of a patients SOB
FBC Troponin Carboxyhaemoglobin methaemoglobin LFTs
what does it mean if a patient has raised carboxyhaemoglobin
CO poisoning
what does it mean if a patient has raised methaemoglobin
could be congenital or drugs (dapsone, local anaesthetics and antimalarial drugs)
what chest wall (or MSK) pathologies would cause SOB
osteoporosis - vertebral fractures
Do a bone profile (would show raised ALP if osteoporosis is present)
name some upper respiratory tract infections
sore throat pharyngitis cold tonsilitis epiglottitis laryngitis
what is the upper respiratory tract composed of
nasal cavity
pharynx
larynx
what is the lower respiratory tract composed of
trachea
primary bronchi
lungs
names some lower respiratory tract infections
bronchitis
bronchiolitis
exacerbations of pre-existing lung conditions (asthma/COPD)
Pnuemonia
symptoms of an upper respiratory tract infection
pain fever headache hoarse voice stridor
complications of an upper respiratory tract infection
Quinsy (peri-tonsillar abscess)
signs of an upper respiratory tract infection
raised temperature
erythema
exudate
(exudate - fluid that leaks out of blood vessels into nearby tissues)
symptoms of a lower respiratory tract infection
cough wheeze sputum production pleuritic chest pain
complications of a lower respiratory tract infection
empyema - a collection of pus in the cavity between the lung and the membrane that surrounds it (pleural space).
pulmonary cavity -an abnormal, thick-walled, air-filled space within the lung.
signs of a lower respiratory tract infection
raised RR intercostal muscle movement wheeze dull percussion bronchial breathing
3 important pathogens of an upper respiratory tract infection (URTI)
Group A streptococcus
Corynaebacterium diphtheriae
various viral infections
what can group A streptococcus cause? (URTI)
fever
pharyngitis
tonsillar enlargement
complications of group A streptococcus
Scarlett fever - need to notify WHO
abscess
rheumatic heart disease
what is rhinovirus
the most common culprit behind the common cold
difference between a lower respiratory tract infection and pneumonia
pneumonia shows consolidation on a CXR whereas LRTI doesn’t
any pathogen can cause both pneumonia and LRTI
(Consolidation indicates filling of the alveoli and bronchioles in the lung with pus (pneumonia), fluid (pulmonary oedema), blood or neoplastic cells.)
4 classifications of pneumonia
community acquired - no recent hospital contact
hospital acquired - after 48 hrs in hospital
ventilator associated - after 48 hrs on a ventilator
aspiration - not time related
hospital acquired pneumonia risk factors
post-surgical patients
chronic lung disease
immunocompromised
recent antibiotic exposure (increases infection with resistant organisms)
things to know about streptococcus pneumoniae (pnuemococcus)
- responsible for 50-66% community acquired pneumonia
- gram positive coccus, surrounded by polysaccharide capsule
- over 90 serotypes
- can cause multiple infections: LRTI/pnuemonia, empyema, meningitis, infective endocarditis, abscesses, otitis media and external