Download Respiratory Physiology Exam Q&A: Lung Function and Mechanics and more Exams Advanced Education in PDF only on Docsity!
BSMS103 Theme 4 Exam With
Complete Solution
What is pressure measured in? - Answer Cm of water
What are the two elastic components of the lung? - Answer Elastin fibres in the alveolar walls, bronchioles and capillaries, and alveolar surface tension
What is compliance? - Answer Measure of the elasticity/stretchiness of the lungs. Volume change per unit pressure change
What does normal lung compliance look like on a graph? - Answer Hysteresis loop. Difference in compliance is due to the increased level of energy required for inspiration. More volume in deflation than inflation, as some of the pressure in inflation is being used to recruit and inflate the alveoli
What is surface tension? - Answer Cohesive force between molecules, strong attractive forces between neighbours on the surface. Tends to collapse the alveolus, increases with emphysema and age
What is surfactant and how does it reduce surface tension? - Answer Surfactant is produced by type II alveolar cells from fatty acids. Surfactant has hydrophobic and hydrophilic ends which repel each other, reducing the attraction between cells.
Why is surfactant important? - Answer Increases lung compliance, promotes alveolar stability, prevents alveolar collapse, sucks fluid from capillaries
What is the functional residual capacity? - Answer Balance point where lungs and chest are in equilibrium (after exhaling); lungs sit at this position naturally
What is the transpulmonary pressure? - Answer Difference between alveolar pressure and intrapleural pressure
What are the accessory muscles of inspiration? - Answer Scalene and sternomastoids
In normal breathing, what is the intrapleural pressure? - Answer Negative
What do inspiration and expiration do to the intrapleural pressure? - Answer Makes it more negative, and expiration makes it more positive so air is forced out of the lungs as chest wall and diaphragm relax
How does pressure change during the quiet breathing cycle in inspiration? - Answer 1. Flow line before breathing = 0, increases inwards and RR slows and stops
- to generate flow, create pressure gradient through a change in alveolar pressure; this drives flow and changes lung volume
- reflects static compliance of lungs + generation of driving force of negative alveolar pressure
How does pressure change during expiration in the quiet breathing cycle? - Answer 1. Flow increases, going outwards, rate slows + stops - back to zero
- At end of breath, alveolar pressure back to 0. Changing pressure down drives flow out
- Intrapleural pressure again reflects the compliance and pressure creating this alveolar pressure. Faster lung contraction creates an increase in alveolar pressure
What is airway resistance? - Answer Pressure difference between alveoli and mouth
What is pulmonary resistance? - Answer The tissue and airways
What is laminar flow? - Answer When the air flow is all in one direction
What is the Poiseuille equation and what does it represent? - Answer Resistance is inversely proportional to 4th power of radius; flow is inversely proportional to the viscosity of a fluid. I.e more flow for less viscous liquid
What are the factors in airway resistance? - Answer Inflammation, mucus, bronchodilators, steroids, gas density
What increases the likelihood of turbulent flow? - Answer High velocity, large tube diameter
Where does turbulent flow occur? - Answer Trachea
What is the tidal volume? - Answer The total amount of air taken in in a breath
What is the vital capacity? - Answer Maximum amount of air a person can expel from the lungs after taking a maximum inhalation in. Equivalent to sum of IRV, TV, ERV.
What is the approx amount of dead space in the lungs? - Answer 150ml
What is the forced vital capacity? - Answer When all excess air is forced out
What is the residual volume? - Answer Air left in lungs after normal exhalation
What is total lung capacity? - Answer The max amount of air in lungs after forced inhalation
What is FEV1? - Answer Forced expiratory volume in 1 second; how much air is expelled in 1 second, then work it out as percentage of total
What does the spirometry pattern look like for someone with a mild obstruction e.g asthma? - Answer FVC is unchanged; same amount of air is moved but it takes longer, and there is a lower FEV1.
What is gas exchange influenced by? - Answer Alveolar surface area and thickness of alveolar membrane
How do you measure abnormal gas exchange? - Answer Use small concentrations of CO as a tracer gas; acts in a similar way to O2 in the lungs. Hold breath for known time; measure CO in expired air - dilution gives alveolar volume
What does perfusion look like in an imperfect lung? - Answer Not all alveoli are equally perfused/ventilated so different alveoli have different gas exchange rates
How do you calculate the SaO2 of mixed blood? - Answer Either use a weighted average or a ratio
Does increasing FiO2 help raise SaO2? - Answer This increases the fraction of inspired oxygen. Still cannot get SaO2 above 100%, and won't help if there is a chunk of lung not being oxygenated
Can aid shunting but this is not always fixed (VQ mismatch)
How can one raise SaO2? - Answer Close down veins/arteries where it is occurring to improve oxygen saturation, so the rest of the lungs get the rest of the O2. Divert blood to ventilated areas.
How does the body respond to pneumonia? - Answer By shutting down the lobe where the shunting occurs, allows blood to only go to ventilated areas
Why is hypoxic PA constriction bad in COPD? - Answer All the lung segments are working individually, so all increase their resistance to flow so that the perfusion goes elsewhere. So, heart must pump harder and faster to pump blood into stiff vascular bed; many COPD patients have RH failure due to this
Where within the lung is the intrapleural pressure less negative? - Answer Less negative at the base than at the apex because alveoli at base are compressed, so lower one expands more upon standing
Why and what are the regional differences in intrapleural pressure? - Answer More negative in apex; less ventilation. Also no lung weight on apex so less heavy.
Most ventilation in the base of the lung.
On different parts of the compliance curve; base on steeper part so a change in pressure causes more expansion
What is the perfusion inequality within the lung? - Answer Greater blood flow at base of lung largely due to gravity. Additional capillaries opened up ; aids flow
At RV, flow is greater at apex
Less uneven during exercise as PA pressure rises
What does blood flow per alveolus depend on? - Answer Location of the alveolus, and volume of the lung. Typically working between FRC and TLC, so blood flow sits in middle of curve; less at apex, more at base
What happens in VQ mismatch? - Answer Q gradient is steeper than V gradient - at apex relatively under perfused, where as at base relatively under ventilated
What is the diffusion gradient like between capillaries and alveoli? - Answer Small; drives gas exchange. Depends on adequate ventilation of the alveoli
What has a greater effect on efficiency; low PaO2 or high PaO2 - Answer Low has a greater effect on efficiency
What happens in pulmonary shunting? - Answer Some bronchial venous blood drains into pulmonary veins and enters left atrium; mixes with oxygenated blood. In normal lungs, 1-2% of output; not that significant
When does pulmonary shunting become a problem? - Answer When there is a VQ mismatch so theres a lower PO2 in blood from lung base, so lowers mixed capillary PO2, so lowers mixed blood PO2.
What is VQ mismatch commonly a cause of? - Answer Hypoxia in pneumonia, COPD, asthma
Which part of the brainstem is the rhythm generator? - Answer Medulla - has inspiratory and expiratory groups of neurones
Which part is responsible for rate modification? - Answer Pneumotaxic centre, in pons
When does the respiratory centre begin to respond to hypoxia? - Answer Drive does not kick in until SaO2 falls below 88%
What is the problem with those who are CO2 insensitive? - Answer Cannot detect increasing levels of CO2, so respiratory drive does not increase sufficiently. Therefore prone to type II respiratory failure
What do you measure in arterial blood gases? - Answer Acid-base status, gas tensions, O2 and CO2.
Why do you assess ABGs? - Answer To assess ventilatory status, oxygenation, acid-base status, and response to an intervention
Why is a base excess equivalent to a metabolic shift in HCO3- - Answer If Co2 increases, the other side of the equilibrium does too, so more H+ and HCO3-. But kidneys excrete H+, so just leads to build up in HCO3-
What does it indicate when the CO2 levels fit the change in pH? - Answer It shows that the problem is primary respiratory. If CO2 levels do not fit the change in pH, then it is metabolic
If the problem is primary respiratory, how do you identify whether there is metabolic contribution? - Answer If the base excess is out of -2 - 2, there is a metabolic contribution. Then identify whether it is compensating or combined. If the base excess is within this range, indicates a simple respiratory problem
How do you identify whether there is compensation occurring? - Answer If base excess is out of the normal range (-2 to 2), then it is compensated - chronic. Normal base excess indicates that it is acute
What is the term for low pH? And for high pH? - Answer Acidosis and alkalosis
What is more important at a tissue level; paO2 or saO2? - Answer SaO2 - if above 90%
then it is fine
What are the trends regarding atmospheric pressure and height? - Answer Greater height = lower pressure
At high altitude, what is the response to lower PaO2? - Answer Hypoxic hyperventilation: increases alveolar ventilation. Decrease in PaCo2 - respiratory alkalosis. This reduction in PACO2 leaves more space for O2 in alveoli
What effect does respiratory alkalosis have on the ventilatory response to hypoxia? - Answer It decreases ventilatory response, so hyperventilation decreases and the PaO falls
How does the renal system compensate for an alkaline blood pH? - Answer by excreting extra HCO3-
What are the symptoms of acute mountain sickness and why? - Answer Headache due to increased cerebral blood flow - compressed brain
Malaise - due to hypoxaemia
Loss of appetite, N&V - reduced GI perfusion
Peripheral oedema - hypoxaemia leads to fluid retention
Disturbed sleep - periodic breathing, insomnia
Cyanosis
How can you prevent/treat acute mountain sickness? - Answer Prevent it by acclimatisation
Treatment: resent or descend
What is HAPE? - Answer High altitude pulmonary oedema. Abnormal fluid accumulation in lungs. Symptoms: SOB, cough, tachypnoea, tachycardia, clinical signs of PE. Impaired ability to exchange gas at alveoli, altered pulmonary compliance:
What are the types of patient interfaces? - Answer Nasal cannulae, controlled masks and uncontrolled masks. Oxygen reaches the patient as either litres per min or percentage inspired.
What are the clinical indications where oxygen therapy can be given? - Answer Acute hypoxaemia, chronically hypoxaemic COPD patients w/ acute exacerbation, chronically hypoxaemic stable COPD patients, palliative use in advanced malignancy.
What pathologies can cause acute breathlessness with hyperaemia in patients that do not have significant background lung problems? - Answer Acute pulmonary oedema, acute pneumonia, acute pneumothorax, acute asthma
What its the risk of untreated acute breathlessness with hypoxaemia? How do you treat this? - Answer Risk of acute cardiac dysrhythmia and organ failure. Use a high flow uncontrolled mask with maximal oxygen treatment.
What are the issues surrounding oxygen treatment of chronically hypoxaemic patients with COPD who have an acute exacerbation? - Answer Often acclimatised to a lower pO2, so depend on their hypoxaemic drive. If you over-correct their pO2, can switch off their respiratory drive leading to CO2 retention, acidosis, narcosis and death.
How do you instead treat chronically hypoxaemic COPD patients w acute exacerbation?
- Answer Controlled oxygen mask, pO2 of 24%. then titrate oxygen dosage against response (look at ABG for this)
What must be stated on the drug chart in hospital when prescribing oxygen? - Answer Type of source, dosage, target oxygen saturation range
What occurs in untreated chronically hypoxaemic patients? - Answer Develop worsening pulmonary arterial hypertension and right ventricular hypertrophy
What can LTOT be used for? Which indications show it should be used? - Answer Some patients w COPD. Either below 7.3kPa or 7.3-8kPa with secondary polycythaemia, nocturnal hypoxaemia, peripheral oedema or evidence of pulmonary hypertension.
Provided from oxygen concentrator, treatment for min 15 hours per day
What are the benefits of LTOT? - Answer Improved long term survival, prevention of deterioration in pulmonary hypertension, reduction of polycythaemia, improved sleep quality and renal blood flow, reduction in cardiac arrhythmias
What is obstructive sleep apnoea? - Answer Cessation of airflow for 10s or more. Obstructive indications collapse of pharyngeal airway during sleep. 5 or more obstructive apnoeas per hour.
What is the incidence of OSA in men and women? What are the risk factors attached? - Answer 4% men 2% women. Increased with age, obesity, neck circumference, alcohol/sedatives, craniofacial/pharyngeal abnormalities, disease associations (e.g hypothyroidism)
What happens in sleep apnoea? - Answer Sleep - pharyngeal muscle relaxation - airway collapse - apnoea - arousal - tone returns - resumption of breathing - sleep
What are the clinical features of OSA? - Answer Daytime sleepiness, irritability/mood swings, morning headaches/dry mouth, snoring, unrefreshing sleep, nocturnal choking/waking with a start, nocturnal cardiac arrhythmias, cor pulmonale, polycythaemia,
What are the consequences of OSA? - Answer Increased risk of accidents. Associated w/ hypertension, type II diabetes, IHD, CVD. Also associated with CAD, heart failure can make it worse
How is OSA managed? - Answer Treat any associated problems, weight loss, avoid hypnotics/alcohol, surgery, CPAP
What are the positives and negatives of CPAP? - Answer Symptoms eradicated completely, mask problems, airway drying, lifelong treatment
What are the symptoms of asthma? - Answer Cough, wheeze, breathlessness, tight chest. Episodic, may be worse at night or after exposure to triggers.
What are the triggering factors of asthma? - Answer Three main sections;
Inflammation - respiratory infection, allergens, work place
Constriction - change in temperature, exercise, cold air, emotion
Other - medications, food additives, tolerance, reflux, air pollution
What is crucial in making a diagnosis of asthma? - Answer History - past medical, social and family history all provide clues. Physical exam likely to be normal unless during an attack
How do you investigate asthma? Anything expected? - Answer CXR normal, may have hyperinflation
High eosinophil count
Skin prick test shows allergies
Lung function tests e.g peak flow may show airway obstruction
How do you manage asthma long term? - Answer Options - pharmacological or non
Non - lose weight/quit smoking
Pharmacological: relievers - B2 agonists such as salbutamol
Controllers/preventers - inhaled corticosteroids, long acting inhaled beta agonists
What are the 3 key questions required to ask asthma sufferers? - Answer Have you had difficulty sleeping during the night due to symptoms?
Have you had the usual symptoms during the day?
Has your asthma interfered with your usual activities?
What are methods of specialised treatments for those with difficult asthma? - Answer Desensitisation to proven allergens
Monoclonal anti IgE injections
Immunosuppressant therapy
Bronchial thermoplasty
How can treatment compliance be unintentional and intentional? - Answer Unintentional
- misunderstanding, poor inhaler technique, language, forgetfulness
Intentional - denial, side effect concern
What should be included in a personalised asthma action plan? - Answer Daily medication, triggers to avoid, indicators of asthma, medication for worsening asthma
What are the features of severe asthma, and when it becomes life threatening? - Answer Medical emergency
PEF = 33-50% of best. BPM over 110. RR above 25 breaths per min
Life threatening: hypoxia, silent chest, bradycardia, hypotension, exhaustion, confusion, coma
How do you treat acute severe asthma? - Answer Oxygen, corticosteroids, nebulised bronchodilators (salbutamol). Exceptional circumstances require IPPV
According to WHO, how many people have latent infection TB? - Answer 2 billion
How many deaths globally from TB? - Answer 3 million
What is the epidemiology of TB in london? - Answer 40/100 000
What increases risk of TB more - being UK born or being born abroad - Answer being born abroad
What are the ways in which the likelihood of TB transmission increases? - Answer Close contact with smear +ve, contact with high risk groups (travel/living in high risk country), immunodeficiency (HIV, steroids, chemo, vit D deficiency, diabetes, end stage renal failure), lifestyle factors (drug/alcohol misuse, homelessness, overcrowding, prison inmates), genetic susceptibility
What % of TB cases are primary? What occurs? - Answer 1-5% cases; bacilli overcome immune system soon after the initial infection
What occurs in a latent infection with TB? - Answer 2-23% cases - reactivation disease. The risk of reactivation increases with immunosuppression
What principles are used to diagnose active TB? - Answer Identify the infected area
Isolate the organism
Obtain information regarding susceptibility to antibacterials
What principles are used in the diagnosis of latent TB? - Answer Identify the immune response to TB proteins
What occurs in the Mantoux test? - Answer Needs circulating memory T-lymphocytes, these mount a delayed hypersensitivty reaction. It is cross reactive with other mycobacterial antigens, so non-specific. May be falsely negative in severely ill/immunosuppressed individuals
What is ELISA? Why is it used? - Answer Enzyme-linked immunological assay of release of interferon-gamma in whole blood, following stimulation by specific tuberculosis antigen. More specific than Mantoux, and correlates better with the degree of exposure than Mantoux. But does not differentiate between latent infection and disease. Recommended for those who are TST positive
Discuss pulmonary TB - Answer Is the majority of cases - 55%, so infection risk. Cavitary disease. Symptoms: haemoptysis, cough, chest pain, night sweats, weight loss, fever,
pallor, fatigue.
What investigations are used in PTb? - Answer Sputum, bronchoalveolar lavage fluid, CXR. May see hilar lymphadenopathy, tuberculous pleural effusion
What are the key features of extra pulmonary disease? - Answer More common in non-UK born asian origin. Sites; lymph nodes, CNS< bone, genitourinary, GI tract, disseminated/miliary
What is the common presentation of TB lymphadenitis? - Answer Non tender cervical LN, no systemic symptoms. Occasional draining sinus/fluctuant node. Firm discrete mass. Usually unilateral. HIV co infection affects presentation. Often gets worse on treatment, can form tracts with chronic discharge, cold abscess formation
What is the common presentation of disseminated/miliary TB? - Answer Fevers, sweats, weight loss and malaise v common. Majority have respiratory symptoms. 20% have GI/CNS symptoms; abdo pain, diarrhoea, hepatomegaly (50%), headache or confusion, altered mental state (20%)
What are the other forms of TB? - Answer Skeletal, CNS, pericardial, genitourinary, TB enteritis, eye TB
What were the old surgical therapies for TB? - Answer Thoracoplasty, rib resection, plombage
What is the modern control of TB? - Answer Early diagnosis and treatment, combination of minimum 3 drugs
Optimal adherence, contact tracing
How is TB prevented? - Answer BCG, chemoprophylaxis
What are the first line drugs used in TB treatment? - Answer Isoniazis, Rifampicin,
seen in alcoholics, respiratory disease, smokers, hyposplenism. HIV causes 50-100x increase in invasive pneumococcal disease. Acquired in nasopharynx; asymptomatic in 40-50% cases. Causes either lobar or bronchopneumonia
How does one diagnose pneumococcal disease in CAP? - Answer Look at blood cultures and urinary pneumococcal antigen
When is haemophilia influenzae an important cause of CAP? - Answer Important in patients with pre-existing lung disease such as COPD/CF. Clinical features are indistinguishable from other bacterial causes. Treatment: amoxicillin/co-amoxiclav
What does mycoplasma pneumoniae most commonly cause? - Answer Atypical pneumonia, often in a young patient. Occurs in cycles, usually only in one lobe. Diagnosed by rising titres of complement fixing antibodies. Treatment: macrolides/tetracyclines
What are the extra-pulmonary symptoms of mycoplasma pneumonia? - Answer Malaise, headache, arthralgia, erythema multiforme, erythema nodosum, transverse myelitis, aseptic meningitis, cerebellar ataxia, cold aggluitins, pericarditis, myocarditis
What symptoms are prominent in CAP caused by Chlamydophila pneumoniae? - Answer Prominent headache, gradual onset mild symptoms. Often occurs in older patients, causes about 5-10% CAP cases. Can be asymptomatic. Treatment: macrolide or tetracyclines
What is caused by Chlamydophila psittaci? - Answer Zoonosis - infected bird exposure. Causes extra pulmonary symptoms; rose spots on abdomen, segmental or bronchopneumonia. Treatment: macrolide or tetracyclines
What is Legionella pneumophila? What does it cause? - Answer Water contaminant, aerosolised inhalation. Sporadic infections - must notify Public health of outbreak
What occurs in Legionnaire's disease? - Answer Responsible for 2-9% of CAP. Most severe of atypical pathogens. Initial mild headache, then fevers, myalgia, dyspnoea, GI
upset. Can cause lobar or multi lobar pneumonia. Diagnose through direct immunofluorescence/urinary legionella antigen. Treatment with macrolides or quinolones
What types of pneumonia is Staph aureus associated with? - Answer Young and elderly
Community associated MRSA
Severe necrotising pneumonia, PVL, lung abscesses
What are the clinical features of pneumonia? - Answer fever, malaise, pleuritic chest pain, breathlessness, cough, sputum, haemoptysis. Elderly patients more likely to be atypical - confused, arthralgia, GI upset, jaundice, lethargy, flu-like
What do you look for in CXR for pneumonia? - Answer Consolidation - lobar, air-bronchogram
Infiltrates
Cavitation
What are some differential diagnoses associated with pneumonia? - Answer Heart failure, malignancy, inhaled foreign body/obstructing tumour, PE, poss eosinophilic pneumonia/vasculitis
How is the severity and prognosis of pneumonia assessed? - Answer CURB-65 score: confusion, urea, respiratory rate, systolic bp, above the age of 65
What is the trend between pneumonia mortality and CURB-65? - Answer Higher CURB-65 score = larger mortality %
What does a failure to respond in pneumonia patients indicate? - Answer Mortality is higher in non-responders
Could be due to wrong/incomplete diagnosis, antibiotic problem, complication developing, underlying bronchial obstruction
