PBL Topic 2 Case 1 Flashcards
Identify two ways in which the lungs can be expanded and contracted
- Downward and upward movement of the diaphragm
- Elevation and depression of the ribs
Identify the muscles involved in inspiration
- Sternocleidomastoid
- Scalenes
- External Intercostals
- Pectoralis Minor
- Serratus Anterior
- Diaphragm
Identify the role of the sternocleidomastoid during inspiration
- Elevates sternum
Identify the role of the scalenes during inspiration
- Elevate rib 1 and 2
Identify the role of the pectoralis minor during inspiration
- Elevate ribs 3-5
Identify the role of the external intercostals during inspiration
- Elevate ribs 2-12
Identify the role of the diaphragm during inspiration
-Descends upon contraction and increases the volume of the thoracic cavity
Identify the muscles involved in quiet expiration
- None
Identify the muscles involved in forced expiration
- Internal Intercostals
- Diaphragm
- Rectus Abdominis
- Abdominal Obliques
Identify the role of the internal intercostals during forced expiration
- Depress ribs 1-11
Identify the role of the diaphragm during forced expiration
- Ascends upon relaxation and decreases volume of thoracic cavity
Identify the role of the rectus abdominis during forced expiratinon
- Depresses lower ribs
- Pushes diaphragm upwards
- Compressing the lungs
Identify the role of the abdominal obliques during forced expiration
- Depresses lower ribs
- Pushes diaphragm upwards
- Compressing the lungs
Where is the lung attached to the chest cage?
- At its hilum
What is pleural pressure and what are its typical values?
- Pressure of the fluid in the pleural space
- Negative 5 to negative 7.5 as inspiration progresses
What is alveolar pressure and what are its typical values?
- Pressure of the air in the alveoli
- Negative 1 during inspiration, allowing air to move into the lungs
- Positive 1 during expiration, allowing air to escape the lungs
What is transpulmonary pressure?
- Difference between alveolar and pleural pressure
- It is the pressure holding the lungs open
- Equal and opposite the elastic recoil
- Positive value
What is lung compliance?
- Extent to which lungs will expand
- Per unit increase in transpulmonary pressure
What is the total compliance of both lungs together?
- 200ml per cm H20 transpulmonary pressure
Identify two factors that affect lung compliance
- Elastic forces of lung tissue
- Elastic forces caused by surface tension
What is surfactant and which cells secrete it?
- Surface active agent that greatly reduces surface tension of water
- Type 2 alveolar epithelial cells
Identify LaPlace’s law in relation to the alveoli
- Pressure = 2 x Surface Tension / Radius of Alveolus
Identify the three fractions of work that takes place during inspiration
- Elastic work
- Tissue work
- Airway resistance work
What is anatomic dead space and what is its typical value?
- All spaces of the respiratory system other than the alveoli and related areas of gas exchange
- 150 ml
What is physiologic dead space and what is its typical value?
- Non functional alveoli
- 1500 ml
Which region of the respiratory centre causes inspiration?
- Dorsal respiratory group
- Via repetitive bursts of inspiratory action potentials to diaphragm
Which region of the respiratory centre causes expiration?
- Ventral respiratory group
- Via expiratory signals to the abdominal muscles
Which region of the respiratory centre controls the rate and depth of breathing?
- Pneumotaxic Centre
Where is the dorsal respiratory group located?
- Medulla
What is the role of the tractus solitarius?
- Sensory termination of vagus and glossopharyngeal nerves
- From peripheral chemoreceptors, baroreceptors and several lung receptors
Where is the apneustic centre located?
- Pons
Identify two roles of the apneustic centre
- Continuous stimulation to dorsal respiratory group
- Co-ordinates transition between inhalation and exhalation
Describe the inspiratory ramp signal
- Action potential begins weakly and increases in a ramp manner
- Resulting in contraction of the diaphragm
- Before ceasing abruptly, turning off excitation
- Resulting in relaxation of the diaphragm
Where is the Pneumotaxic centre located?
- Nucleus parabrachialis
- Upper pons
Identify the roles of the pneumotaxic centre?
- Inhibits apneustic centre
- Thus controls switch off point of inspiratory ramp signal
Where is the ventral respiratory group located?
- Medulla
- Nucleus ambiguus rostrally
- Nucleus retroambiguus cordally
Identify two roles of the ventral respiratory group
- Neurones spill over into DRG during inspiration
- Expiratory signals to the abdominal muscles
Outline the Hering Breuer Reflex
- Stretch receptors in bronchi and bronchioles
- Impulses through vagus nerve to DRG during overinflation
- Switch off inspiratory ramp signal
What substances act on the central chemoreceptors?
- Carbon Dioxide
- Hydrogen Ions
Outline how CO2 and H+ act on central chemoreceptors
- CO2 dissolves to form carbonic acid
- Crosses blood brain barrier
- Dissociates into H+ and HCO3- ions
- H+ have a potent stimulatory effect on chemosensitive area
What substances act on the peripheral chemoreceptors?
- Oxygen
Identify two peripheral chemoreceptors and their associated nerves
- Carotid bodies, located in carotid sinus, impulses through Hering’s nerves and glossopharyngeal nerves
- Aortic bodies, located in aortic arch, impulses through vagus nerve
Identify four causes of hypoxia
- Inadequate oxygenation (atmospheric)
- Pulmonary Disease
- Anaemia
- Poisoning of oxidation enzymes
Why is oxygen therapy inappropriate in cases of anaemia or poisoning of oxidation enzymes?
- Oxygen is readily available
- It is the mechanisms of oxygen transport that is deficient
Identify two ways that pulmonary disease may cause hypoxia
- Hypoventilation caused by increased airways resistance / decreased pulmonary compliance
- Abnormal Va/Q ratio (increased physiologic dead space/shunt)
What should the cardiothoracic ratio be?
- 50%
Identify two causes of a large CTR
- Cardiomegaly caused by left ventricular dilatation or pericardial effusion
How can you check for hyperinflation?
- Count ribs
- Hyperinflation if more than 10 posterior ribs are visible
What is meant by lung consolidation?
- Lung tissue that is filled with liquid rather than air
Identify three possible causes of lung consolidation?
- Infection
- Infarction
- Inflammation
What are lung shadows suggestive of?
- Bronchiectasis
What is meant by the term pneumothorax?
- Air in the pleural space
Identify the risk factors of primary pneumothorax
- Smoking
- Tall Stature
- Apical pleural blebs
- Being male
What is the difference between primary and secondary pneumothorax?
- Primary = No lung disease
- Secondary = Lung Disease
- Secondary lung disease has higher mortality rates
Outline the pathophysiology of a spontaneous pneumothorax?
- Rupture of pleural bleb
- Pressure in pleural space becomes positive
- Transpulmonary pressure reaches 0
- Lung collapse due to elastic recoil
Outline the pathophysiology of a tension pneumothorax
- Valvular mechanism occurs in which air enters but cannot escape pleural space
- Pleural pressure becomes increasingly positive
- Mediastinal shift
- Reduces venous return
Outline the signs and symptoms of a pneumothorax
Spontaneous:
- Tachypnoea
- Dyspnoea
- Reduce lung sounds in affected lung
Tension:
- Tachycardia
- Cyanosis
- Hypotension
- Mediastinal Shift
- Tracheal Displacement
- No lungs markings (complete translucency)
- Sharply defined edge of deflated lung
Identify the findings of a pneumothorax on chest x-ray
- No lung markings (complete translucency)
- Sharply defined edge of deflated lung
How can you differentiate between a pre-existing emphysematous bullae and a pneumothorax?
- CT scan
When is simple aspiration carried out?
- Young patients
- Presenting with a medium or large primary pneumothorax
Outline the procedure of a simple aspiration
- Infiltrate lidocaine
- Second intercostal space, mid-clavicular line
- Cannula through pleura, attached to three way tap
When is intercostal tube drainage carried out?
- Older patients
- Presenting with secondary pneumothorax
Outline the procedure of an intercostal tube drainage
- Infiltrate lidocaine
- Fifth-intercostal space, mid-axillary line
- Cannula through pleura, attached to three way tap
-
Why is an underwater seal used in a chest drain?
- Air can pass from tube into atmosphere by forming bubbles
- Air cannot pass back into tube
When is emergency surgery for a pneumothorax required?
- Continued bubbling after 5-7 days
- Recurrence of primary spontaneous pneumothorax in first year (1 in 5 cases)
Identify three ways in which pleurodesis can be achieved?
- Pleural abrasion
- Partial pleurectomy
- Chemical pleurodesis with talc (contra-indication for surgery)
What is pleurodesis?
- Surgery in which lung is adhered to chest wall
- Seals pleural cavity
- Prevents build-up of air
Outline ATLS Protocol: Airways and Breathing
Assess volume, rhythm character and symmetry of breathing
- Determine accessory muscle use e.g. abdominal movement
- Supplemental oxygen (60% and adjusted in light of ABGs) to patients with dyspnoea, tachypnea or chest pain
Outline ATLS Protocol: Circulation
- Palpate carotid pulse in unconscious patient
- Palpate peripheral pulses (e..g radial and brachial) in conscious patient
- Venous access for administration of drugs / fluids
Outline ATLS Protocol: Airways: Disability
- Conscious level assessed using Glasgow Coma Scale
- Score of 8 or less denotes coma associated with airway compromise
Outline ATLS Protocol: Airways: Exposure, Evidence Examination
- Clinical examination
- Patient undressed with privacy maintained
- Warm blankets/ environment/ fluid to prevent hypothermia
What does the autonomic nervous system control?
- Visceral functions of the body
Identify the two subdivisions of the autonomic nervous system
- Sympathetic
- Parasympathetic
How does the position of the ganglia differ in the sympathetic and parasympathetic subdivisions?
- Sympathetic: Located immediately after leaving the spinal canal
- Parasympathetic: Located much closer to effector
What is a cholinergic neurotransmitter substance?
- One that secretes acetylcholine
What is an adrenergic neurotransmitter substance?
- One that secretes noradrenaline
What type of nerve fibres do preganglionic neurones possess?
- Cholinergic
What type of nerve fibres do postganglionic parasympathetic neurones possess?
- Cholinergic
What type of nerve fibres do postganglionic sympathetic neurones possess?
- Adrenergic
Identify the two types of cholinergic receptors and their location
- Muscarinic: Effector Cell
- Nicotinic: Ganglia
What type of receptors are adrenergic receptors?
- G-protein coupled receptors
Identify the two major types of adrenergic receptors
- Alpha (1 and 2) and Beta (1 and 2)
Which second messenger system is used by alpha receptors?
- Phospholipase C
Which second messenger system is used by beta receptors?
- Adenylyl Cyclase cAMP
How do alpha and beta receptors differ in their response to adrenaline and noradrenaline
- Adrenaline excited both receptors equally
- Noradrenaline mainly excites alpha receptors
Identify examples of B1, B2 and B3 receptors
- B1: Heart rate and force of contraction
- B2: Vasodilation and bronchodilation
- B3: Lipolysis
What is Mass Discharge
- When all portions of sympathetic nervous system discharge simultaneously
- Due to hypothalamic activation
- In response to fright / fear pain
Outline the Alarm Phase
- Fight or Flight Response
- Increased blood flow to active muscles and away from organs
- Increased glycolysis by liver and muscles
- Increased strength and mental alertness
- Mainly adrenaline / noradrenaline
Outline the Resistance Phase
- Mobilisation of energy reserves, mainly lipids and amino acids
- Conservation of glucose
- Mainly glucocorticoids
Outline the Exhaustion Phase
- Lipid reserves deplete
- Structural or functional damage to vital organs
- Inability to produce glucocorticoids
- Failure of electrolyte balance
Outline how local anaesthetics work
- Block the initiation and propagation of action potentials
- By blocking sodium channels
- Through interaction with interaction with amino acid residues of s6 transmembrane helical domain of channel protein
Outline two uses of lidocaine
- Local anaesthetic
- Treatment and prevention of ventricular dysrhythmias
What is the half life of lidocaine?
Identify two ways in which hepatic blood flow can be reduced
- 2 hours
- Reduced cardiac output after MI
- Drugs that reduce contractibility (B1 adrenoreceptor antagonists)
Identify three adverse effects of lidocaine
- Drowsiness
- Disorientation
- Convulsions
Lidocaine is considered a Class 1B drug, what does this mean?
- Binds to alpha subunit on sodium channel
- Inhibits action potential
- During phase 0
What is meant by the term use-dependence?
- The more frequently the channels are activated, the greater the degree of block produced
Identify two causes of post traumatic stress disorder?
- Witnessing violent death of others
- Victim of sexual abuse, rape, torture, terrorism or hostage taking
Outline 3 pre-disposing factors to PTSD
- Personality
- Previously unresolved traumas
- History of psychiatric illness
Identify six clinical features of PTSD
- Flashbacks
- Insomnia
- Emotional blunting
- Emotional detachment
- Avoidance
- Hyper-vigilance
Identify three complications of PTSD
- Depressive illness
- Alcohol misuse
- Chronic course (most cases recover at the end of the first year)
Identify 4 methods of treatment / management of PTSD
- Cognitive Behavioural Therapy
- Social support by those involved
- Eye movement desensitisation and reprocessing
- SSRIs and venlafaxine
What is CBT?
- Structured therapy involving..
- Removing maladaptive behavioural responses
- Replacing them with new responses
What is the bystander effect?
- Phenomenon in which someone is less likely to intervene in an emergency situation when other people are present.
What is pluralistic ignorance?
- A state in which everybody in the group misleads everyone else by defining the situation as non-emergency.
What is diffusion of responsibility?
- People are less likely to offer help to someone if there are others present
- They perceive responsibility as being shared between all present
- Therefore see themselves as being less personally responsible.
Identify four factors that affect the likelihood of a person receiving help.
- Ambiguity of situation
- Cost-benefit analysis of helping
- Gender, women more likely to receive help than men
- Competence
If a person wishes to receive help in an emergency situation, either as a victim or active helper, what should they do?
- Choose a specific person in the crowd to help them
- Provide the person with a specific instruction
- Rather than appealing to the larger group.
What does Lazarus mean by primary appraisal?
Individual appraises event as either irrelevant, positive, threatening or challenging
What does Lazarus mean by secondary appraisal
Individual appraises coping strategies, which include direct action, seeking information, doing nothing or defence mechanisms
Identify four types of stressful events
- Salient events
- Overload, multitasking
- Ambiguous events
- Uncontrollable events
What is the interaction between psychology and physiology in stress?
- Appraisal causes a change in physiology
- Which is detected and then appraised causing a further response
Identify psychological factors that affect the ongoing process of appraisal
- Control
- Personality
- Coping
- Social support
What is the Cochrane Collaboration?
- International Organisation
- Prepare, maintain and promote accessibility to systematic reviews
- Stresses the importance of RCTs as the gold standard study type
- High degree of methodological rigour and are updated frequently
What is meant by the term stress reactivity?
- Physiological changes in response to stress
- Sweating, increased blood pressure
- Varies between people
What is meant by allostatic load?
- Fluctuation in physiological changes as the individual recovers from stress
- Recovery is less compete and increasingly depleted
