PBL 1 Flashcards
name 2 roles of the gas exchange system
- conducts oxygen into the body
2. removes co2 from the body
what is the purpose of the pleura and pleural fluid?
the 2 pleura allow optimal expansion and contraction of the lungs. the pleural fluid acts as a lubricant, allowing the layers to slide smoothly over each other friction free
what is the order of air passages from the trachea?
trachea —> primary bronchus —> secondary lobar bronchi —> tertiary segmental bronchi —> conducting bronchioles —> terminal bronchioles —> respiratory bronchioles
how many lobes do the lungs have and what are they divided by?
right has 3 — superior, middle, inferior
left has 2 — superior, inferior
separated by fissures — oblique and horizontal (only on right)
which lung is smaller and why?
left lung is smaller as it shares its side of the thorax with the heart
what borders do the lungs have?
anterior, inferior and posterior borders
what surfaces do the lungs have?
costal, mediastinal, diaphragmatic
what kind of epithelium is present in the trachea?
ciliated epithelium — protective barrier with cilia to waft things out of the respiratory tract
what are basal cells?
lung stem cells which replaced damaged cells
what are goblet cells?
secrete mucus
what are serous cells?
secretory cells
type 1 vs type 2 alveolar cells
type 1 — very thin simple squamous cells, non-ciliated, main site of gas exchange — covers 90% of alveolus
type 2 — produce surfactant to keep airways open (reduce surface tension), preventing airway collapse. also renew type 1 cells
what happens to the cells and cilia as you move down the airways?
cells start to become thinner and cilia start to disappear
name the lining cells
ciliated, intermediate, brush (stunted cilia — under research), basal epithelium
what makes up the contractile component in airways?
smooth muscle — controls calibre
what makes up the connective tissue in airways?
fibroblasts (produce matrix proteins that provide support/strucutre), intersitital cells (produce elastin), collagen, proteoglycans, cartilage
what immune cells are present in the airways?
mast, dendritic, lymphocytes, neutrophils, eosinophils, macrophage
what are submucosal glands?
sit under epithelial layer, surrounded by smooth muscle (causes mucus production when it contracts)
role of mucus
traps inhaled toxins, transports them out of the lungs by ciliary beating and cough reflex
role of smooth muscle in airways
- surrounds all airways
- responsible for calibre
- controls level of surfactant protein and mucus production if it contracts around the gland
- very thinly spread out in lower airways — blood vessels fused to the epithelial cells in alveoli (decreased diffusion distance)
describe the effects of disease on airways
- airway narrows
- mucus accumulation
- muscular layer thickening
- inflammatory cell infiltration
what is the forced vital capacity?
- exhale as forcefully as you can
- total volume of air exhaled
how does forced expiratory volume differ to forced vital capacity?
it is the same but in a specified amount of time
what is the effect of bronchodilators on airways and when are they used in asthma treatment?
- they are RELIEVERS = usually blue or green
- cause smooth muscle to relax
- short acting (1-2 hours) and long acting (up to 12 hours)
- usually used when asthma symptoms appear
what is the effect of corticosteroids on the airways and when are they taken in asthma treatment?
- they are PREVENTERS = usually brown, orange or red
- inhaled corticosteroids reduce inflammation in the airways
- used daily even when there are no symtoms
name 3 ways lung volume (+hence calibre) can be reduced
- physical impedance (obesity)
- cellular infiltration
- vascular leak
what is a pneumothorax?
= a collection of air between the visceral and parietal pleura causing a real (rather than potential) pleural space
= a collapsed lung
what causes the lung to collapse?
- gas flows into the pleural space, increasing the pressure to atmospheric pressure
- lung partially collapses due to the elastic recoil pressure
classification of a pneumothorax
1) primary = no underlying lung disease
2) secondary = no underlying lung disease
a. spontaneous = the majority of spontaneous pneumothorax are minor and self resolve
b. traumatic = in a small number of cases, a one way valve forms, causing more air to enter the pleural space
what is a haemothorax?
a collection of blood in the pleural cavity — often associated with a traumatic pneumothorax
what happens in a tension pneumothorax?
= medical emergency
- displaces mediastinal structures
- compromises cardiopulmonary function
- flow of air is one way (from lung into the pleural cavity) upon inspirtation — upon inspiration the air from the atm enters the pleural cavity (from stab wound) down the pressure gradient
- upon expiration, the air can’t escape from pleural cavity as the pleural pressure doesn’t increase above the atm pressure
- every inspiration results in a build up of air and pressure
what are the clinical features of a pneumothorax?
- spontaneous = chest pain and breathlessness
- pain = sudden onset, localised to the affected side and made worse on inspiration
- dyspnoea
- reduction in breath sounds on the affected side
- movement of chest wall may be reduced
- percussion note will be resonant
how do you diagnose a pneumothorax?
- decreased or absent breath sounds over affected lung
- confirmed by x-ray — will illustrate the collapse of the lung as extra black space, indicating the presence of air around the lung
- in tension pneumothorax, the lung shrivels up away from the affecte side and the mediastinum (inc. trachea) will shift towards the unaffected side = trachea displacement
= ABSENT BREATH SOUNDS AND RESONANT PERCUSSION
what are the 4 steps to examine the chest?
- inspection
- palpation
- percussion
- auscultation
what does a chest drain underwater seal create and why is this important?
- creates a one way valve
- stops more air entering
- usually in the form of an underwater seal
why are there sucking sounds at a wound?
noise of air entering and leaving the wound — not in a tension pneumothorax — here air enters the chest outside the lung but does not escape
why would engorged neck veins be visible?
there is an increase in intrathoracic pressure therefore it is harder for blood to return to the heart — therefore jugular vein distension
why would a patient have difficulty breathing with a pneumothorax?
build up of air puts pressure on the lung, so it cannot expand as much
why would you have a 3 sided dressing for a chest wound?
prevents additional air from entering the pleural cavity , whilst allowing trapped air to escape from the untaped edge during exhalation
why would there be a crackling swelling?
subcutaneous emphysema — air goes into fat
what is the principle of the ATLS protocol?
treat the greatest threat to life first
what is nociception?
the detection of painful stimuli
what do local anaesthetics inhibit?
inhibit action potential generation within cells
what is the mechanism of local anaethetics?
— bind reversibly to Na+ channels in the neuron cell membrane
- pass across lipid membrane in an non-ionised state and become ionised inside the axon (intracellular environment more acidic)
- ionised form is able to bind to the Na+ channel intracellular surface preventing Na+ ion entry and action potential generation
— nerve fibres are blocked in predictable sequence
- preferentially block small diameter, myelinated and high frequency nerve fibres
- sequence of fibres blocked
what is lidocaine?
an anaesthetic with minor analgesic properties
where is lidocaine injected?
into the 2nd intercostal space in mid-clavicular line
what is lidocaine used for?
- given by IV infusion to treat and prevent ventricular dysrhythmias in the immediate aftermath of a myocardial infarction
- also used as a local anaesthetic (analgesic) for minor surgery
- widely used for local anaesthesia (analgesic) for needle aspirations/chest drains
- has a 2 hour half-life — increased by reducing hepatic blood flow (97% clearance in 10 hours)
what is PTSD?
a condition where exposure to an intense and frightening emotional experience leads to lasting changes in behaviour, mood and cognition
what are the major symptoms of PTSD?
- feeling numb to the world with a lack of interest in former activities with a sense of estrangement from others
- reliving the trauma repeatedly
- sleep disturbances
- difficulty concentrating
- over alertness
what is CBT and what does it aim to do?
= cognitive behavioural therapy
- CBT for PTSD is a structured therapy that is designed to desensitise the person to the traumatic event
- reprocess the feared event and improve their strategies to decrease the sense of threat
what muscles work in inspiration (not forced)?
= diaphragm and external intercostals
what is the process of inspiration?
- diaphragm contracts and moves downwards
- external IC contract, elevate ribs outwards and upwards = enlarge thoracic cavity = increases lung volume = decreases pressure = pressure in lungs is lower than atm pressure so air rushes in
what innervates the diaphragm?
phrenic nerve
what innervates the external intercostal muscles?
intercostal nerves
what is the process of expiration?
- passive process
- elastic forces of lungs compress alveolar air volume = increased pressure in lungs = Palv > Patm
- diaphragm and external intercostal muscles relax = decreases thoracic cavity volume = increases pressure in lungs = air forced out
- elastic recoil of lungs is sufficient — all respiratory muscles are relaxed
what are the accessory muscles of respiration and what do they do?
- sternocleidomastoid = assists with the elevation of the sternum
- pectoralis major/minor = assist with the expansion of the ribs laterally
- serratus anterior = assist with the elevation of the rib cage
- latissimus dorsi = assists with the elevation of the lower rib cage
- scalenes = assist with the elevation of the upper rib cage
what happens in forced expiration?
- at the start, elastic recoil is the major force and external IC muscles breaking expiration
- towards the end abdominal muslces are used to push air out
if there is a lung puncture, what happens to the forces?
- puncture has connected pleural space to the atm
- Ppl = Palv = Patm
- collapsed lung
if you suck air out of pleural space to fix a collapsed lung, what are the pressure changes?
- Ppl < Palv —> Ppl «_space;Palv
- lung expands
what is responsible for elastic recoil of the lung?
- connective tissue fibres (collagen and most importantly elastin)
- surface tension forces at the air/liquid interface of the alveolus
what is the functional residual capacity?
the lung volume when the respiratory muscles are relaxed (after a normal passive exhalation)
how does elastic recoil cause air to be forced out (in terms of pressure)?
- elastic recoil begins to squeeze the alveolus space
- Palv is +ve with respect to Patm
- air is forced out
what happens to Ppl during inspiration and expiration?
- Ppl is decreasing as the pleural space is stretched during inspiration
- increases to normal volume during expiration
chest stab — why does lung collapse?
- stabbing punctured the chest wall and possibly lung
- now pleural pressure = atmospheric pressure
- no force to counter elastic recoil
- lung collapses
how can a collapsed lung result in a tension pneumothorax?
- lung collapses
- the puncture acts as a one-way valve
- air drawn into the pleural space with chest expansion
- Ppl increases above central venous pressure
- cardiac filling reduced
- cardiac output and BP fall
what is airflow = to?
airflow = driving pressure / airways resistance
driving pressure = Palv - Patm
what is airways resistance proportional to?
length / radius^4
why is there an increased work of breathing when there is an increased frequency of breathing?
- having to move air faster
- have to generate a greater pressure gradient to move air faster in the same amount of time
why is there an increased work of breathing for an increased tidal volume of breathing?
- lung stretched more
- more force required to stretch the lung
what parts of the respiratory tree are involved in gas exchange?
respiratory bronchioles and alveolar ducts and alveoli
how volume of air does a typical adult breathe in?
0.5L
what volume of air reaches the alveolar space and is involved in gas exchange in a typical adult?
350ml
equation for ‘fresh air’
fresh air = tidal volume - dead space
alveolar ventilation equation
alveolar ventilation = fresh air (= tidal volume - dead space) x breathing frequency
is alveolar ventilation higher for fast or slow breathing?
for the same amount of pulmonary ventilation, slow deep breathing gives more alveolar ventilation that fast rapid breathing
what is residual volume?
the amount of air that remains in the lungs after a forced exhalation (larger than dead space)
(many lung diseases increase ‘physiological’ dead space’)
what is the role of chemoreceptors?
detect changes in the levels of oxygen and carbon dioxide in the arterial aortic bodies and the carotid bodies
what are central chemoreceptors primarily sensitive to and where are they located?
primarily sensitive to the changes in CO2 and they are located in the medulla oblongata near to the medulla respiratory groups of the respiratory centre
what respiratory groups are there? what does each do?
there are 4 — 2 in the medulla and 2 in the pons (pontine respiratory group)
- dorsal respiratory group (in medulla) = controls mostly movements of inhalation and their timing
- ventral respiratory group (in medulla) = controls voluntary forced exhalation and acts to increase the force of inhalation
- pneumontaxic centre (various nuclei of the pons) = coordinates speed of inhalation and exhalation. sends inhibitory impulses to the inspiratory area. involved in fine tuning of respiration rate
- apneustic centre (nucleus of the pons) = coordinates speed of inhalation and exhalation. sends stimulatory impulses to the inspiratory area — activates and prolongs inhalations. overridden by pneumotaxic control from the apneustic area to end inhalation)
what respiratory groups control what (simplified)?
- ventral: expiration
- dorsal: inspiration
- pontine: rate and pattern of breathing
once the neurons stop firing, the inspiration muscles relax and expiration occurs
what are 5 causes of hypoxia?
- inadequate oxygenation of the blood in the lungs due to extrinsic reasons (eg. lack of O2 in the air)
- pulmonary disease
- venous-to-arterial shunts (‘right-to-left cardiac shunts’)
- inadequate oxygen transport to the tissues by the blood
- inadequate tissue capability of using oxygen
what are the physical responses of stress?
- increased SNS activity
- arousal
- CNS activation
- fight/flight respone
what is the fight or flight response (acute stress response)?
- refers to the physiological reaction when there is a perceived threat
- sympathetic nervous system is activated = increased HR/BP/breathing
- an adaptive response to enable management of stress
what are the 3 stages in the general adaptation syndrome response to stress?
- ALARM — recognising a stressor = body initiates fight or flight
- RESISTANCE — cope with or adapt to the stressor = maintain high metabolic rate, body cannot maintain this
- EXHAUSTION — depletion of resources if stressor cannot be overcome = symptoms reappear, can lead to a variety of health issues
what did Lazarus argue?
argued that stress involved a transaction between the individual and their external world, and that a stress response was elicited if the individual appraised a potentially stressful event as actually being stressful (Transactional Model)
according to Lazarus, what is primary appraisal?
the individual appraises the event itself via 4 possible ways:
1) irrelevant
2) benign (gentle) and positive
3) harmful and a threat
4) harmful and a challenge
according to Lazarus, what is secondary appraisal?
the individual evaluates the pros and cons of their different coping strategies
simplified primary vs secondary appraisal
primary = appraisal of the outside world secondary = appraisal of the individual themselves
what factors affect the stress-illness link?
- exercise (decreases stress)
- coping styles
- social support (high SS = decreased stress response = reduction in illness)
- personality
- arousal or perceived control
benefits of social support?
- improved adherance
- improved health outcomes
- effects are strongest in older patients
- better metabolic control — diabetes
- improved outcomes in kidney and heart patients
- triggers to consult
what is the autonomic nervous system divided into?
- sympathetic = fight or flight
- parasympathetic = rest and digest
efferent vs afferent fibres
- afferent (incoming nerves) : organs/tissues (info) —> CNS monitoring via sensort receptors/nerves
- efferent (outgoing nerves) : CNS (instructions) —> organs/tissues
what is a ganglion?
a conjunction of nerve cell junctions
what does the vagus nerve supply?
(cranial nerve 10)
supplies thoracic and abdominal organs
describe the PSNS
- most active under quiet conditions (rest and digest)
- 1st neurone usually in the brain (specifically brainstem = pons + medulla)
- limited anatomical distribution (eg. no supply to limbs, skin, blood vessles, muscles)
describe the SNS
- fight or flight
- 1st neurone (preganglionic) in particular spinal cord segment = T and upper 2-3 L segments
- 2nd neurone (postganglionic) usually in sympathetic ganglion = chain either side of the spinal column
- however some synapses in outlying ganglia ie. not in chain
what do sympathic pathways use?
acetylcholine then noradrenaline. nicotinic receptor then adrenergic receptor (several types!!)
what do parasympathic pathways use?
acetylcholine. nicotinic receptor then muscarinic receptor
how do you switch off signals in the nervous system?
inactivating/removing released transmitters
either/or:
- enzyme destorys transmitter
- transmitter ‘re-coupled’ by presynoptic nerve terminals for re-use or destruction
what enzyme breaks down Ach?
acetylcholinesterase
what is CBT?
= cognitive behavioural therapy
- uses techniques to challenge problem thinking
what is the primary goal of CBT for PTSD?
to undergo some sustained emotional processing of the traumatic memories
how must CBT for PTSD be carried out?
in a controlled way
ie. graded exposure, systematic desensitisation
what is self-efficacy?
a sense of power to affect one’s own behaviour
what are 4 problem-focused coping strategies (taking action)?
- gathering information about the illness
- consulting appropriately
- seeking support
- self-management/engagement
what are 6 emotion focused coping strategies (managing emotions)?
- attempting to control the response
- humour
- reappraisal - “worse things happen at sea”
- positive self talk - “it’s bad but i’ve coped before”
- resigned acceptance
- behavioural disengagement
describe this statement — ”I know you feel ok now, but this medication will stop it from getting worse”
a statement from a doctor designed to improve adherance to treatment that would address a patient’s illness beliefs
ABCDE mnemonic for the primary survey of the ATLS protocol
Airway Breathing Circulation Disability Exposure
what is a catamenial pneumothorax?
pneumothorax caused by endometriosis in a woman at the time of menstruation
what enzyme breaks down noradrenaline molecules after they have been released in a sympathetic synapse?
monoamine oxidase
what relationships are shown in Hebb’s inverted U?
arousal and performance
name 4 things you get as a result of PTSD
- feeling of detachment from the outside world
- re-experiencing of events
- cannot recall important parts of the trauma
- hyper vigilance = the elevated state of constantly assessing potential threats around you
during normal inspiration what alveolar pressure is required to draw in 0.5L of air?
-1mmHg
what is the anatomical dead space respiratory volume of a young male?
150ml
how many broncho pulmonary segments does the right superior lobe contain?
3
adrenaline lowers cAMP levels by acting on what adrenergic membrane receptors?
a2
a pulse rate over what suggests a tension pneumothorax?
135bpm
what are the borders of the safe triangle used when inserting a chest drain?
- apex below axilla
- horizontal level of nipple
- lat dorsi
- pec major
what is a suitable first-line treatment for PTSD?
eye movement desensitisation and reprocessing
activation of what class of neurotransmitter receptors could lead to peripheral vasoconstriction?
a receptor
chest drains are best placed in which region of the thorax?
between 5th and 6th ribs mid axillary line
