Respiratory Flashcards
What is Boyel’s Law?
pressure of a gas is inversely proportional to volume: p∝1/V
What is Charles’ Law
Increase in temperature results in an increase in pressure due to the increased kinetic energy of molecules
What is the ideal gas law?
pressurevolume= amount in molesideal gas constant* temperature
What is partial pressure?
the pressure that would be exerted by one of the gases in a mixture if it occupied the same volume on its own.
What is vapour pressure?
pressure exerted by gaseous water in a mixture
What is the saturated vapour pressure at 37 degrees C?
6.28kPa
What is gas tension?
the partial pressure of a gas dissolved in a liquid
What is gas content?
total amount of gas in a liquid - reacted+dissolved gas
Which cells secrete surfactant?
Clara cells in the bronchioles and type 2 alveolar cells
Which intercostal muscles allow for exhalation and what is their orientation?
innermost and internal intercostal muscles, posterior/inferior
Which intercostal muscles allow for inhalation and what is their orientation?
external intercostal muscle anterior/inferior
At what level does the oesphagus pass through the diaphragm?
T10
At what level does the Aorta pass through the diaphragm?
T12
which nerve and roots innervate the diaphragm?
The phrenic nerve, C3,4,5
What is the difference between the right and left bronchi?
The Left bronchi is longer and more horizontal than the right
Describe the lobes and the fissures of each lung
The right lung has 3 lobes - the upper, middle and lower. These are separated by the horizontal and oblique fissure respectively. The Left lung is smaller due to the heart sitting on the left side of the chest, and has just an upper and lower lobe separated by an oblique fissure
Which muscles are involved in inspiration?
Diaphragm and external intercostal muscles
Which muscles are involved in forced expiration?
Abdominal muscles and innermost and internal intercostal muscles
What are the accessory inspiratory muscles?
sternocleidomastoid, scalenes and pec. minor
How does surfactant work?
Surfactant reduced the interaction between molecules, reducing surface tension. This reduced surface tension prevents alveoli from collapsing, and increases lung compliance.
What is frick’s first law of diffusion?
diffusion rate = (pressure difference x area of fluid x gas solubility)/(distance x √molecular weight)
What are the partial pressures of CO2 and O2 in alveolar air?
O2 - 13%
CO2 - 5.3
What are the partial pressures of CO2 and O2 in arterial blood?
O2 - 13.2%
CO - 5%
What are the partial pressures of CO2 and O2 in venous blood?
O2 - 5.2%
CO2 - 6%
What is serial, alveolar and physiological dead space?
serial - volume of the airways
alveolar - volume of lung that is not airway and does not support gas exchange
physiological dead space is the sum of serial and alveolar dead space
What is the pulmonary ventilation rate?
tidal volume x resp rate
What is the dead space ventilation rate?
dead space volume x resp rate
What is the alveolar ventilation rate?
pulmonary ventilation rate - dead space ventilation rate
what is the inspiratory capacity?
the biggest breath that can be taken in from resting expiratory volume
what is the functional residual capacity?
volume of air which remains in the lungs at the resting expiratory volume
what is the vital capacity?
largest possible volume of air inhaled from forced expiratory volume
what is total lung capacity?
the volume of air in the lungs at the end of maximal inspiration
What is Graham’s Law?
smaller molecules tend to diffuse faster than larger ones
What factors affect the diffusion rate of gases across the air-blood inter-phase (5)
- pressure differences
- solubility of the gas
- surface area of the of fluid
- diffusion distance (0.6 nano metres)
- molecular weight of the gas
What is tidal volume?
volume of air breathed in and out at rest
what is the inspiratory reserve volume?
the extra volume which can be inhaled above that at rest
what is the expiratory reserve volume
the extra volume which can be exhaled above that at rest
what is the residual volume
the volume remaining in the lung following maximal expiration
How would a restrictive pattern differ from a normal on on spirometry?
decreased compliance would allow for normal rate of flow initially, however the overall lung volume is reduced. therefore fev1 may be normal but FVC will be lower
How would a obstructive pattern differ from a normal on on spirometry?
there is increased compliance, so although they may be able to expire the same volume the rate will be lower. therefore FEV1 is reduced but FVC may be normal
What is measured with helium dilution and how?
residual volume. mixture of gases with known helium concentration is given. level of dilution of helium in expired gases allows residual volume to be calculated
what is measured with a nitrogen wash out and how?
serial dead space.
patient is given 1 breath of pure O2,patient expires into a metre which detects nitrogen. volume expired before nitrogen is detected is the serial dead space.
How are acute changes in PO2 detected?
By peripheral chemoreceptors in the carotid and aortic bodies. This is a crude measure which only responds to large drops in PO2. If there is a decrease it causes increase in RR and HR and sends more blood to vital organs.
How are changes in PCO2 detected?
Indirectly by central chemoreceptors which detect changes in pH of the CSF. This is the main mechanism by which ventilation is controlled, as it is fast and sensitive.
How are chronic decreases in respiration detected and monitored?
In patients who chronically hypoventilate, the kidney increases HCO3- levels to compensate for the respiratory acidosis. Choroid plexus cells in the CNS can respond to this persistent increase in HCO3, by allowing an increase in the CSF concentration of HCO3. This decreases the CSF acidity despite persistent high CO2 levels allowing a chronic compensated respiratory alkalosis not to increase resp rate. These patients tend to run on a lower PO2 because of this, so controlled oxygen targets should be lower for them (88-92%).
What is type 1 respiratory failure? What can cause it?
Adequate CO2 exchange but inadequate O2 exchange
type 1 -VQ mismatch e.g. PE, Impaired diffusion e.g. ILD
What is type 2 respiratory failure?
Inadequate O2 and CO2 exchange
respiratory pump failure e.g. head injury, neurological muscle weakness, chest wall problems like trauma
What three things characterise asthma?
1- reversible airway obstruction due to smooth muscle contraction
2- airway wall inflammation and remodelling
3- increase in airway responsiveness to some stimuli e.g. temperature, smoke, pollen
What can precipitate an asthma exacerbation? (4 things)
lack of treatment adherence
exposure to allergen or triggering drug
respiratory virus
cold air
What sort of wheeze is typically present in asthma
a high pitched, polyphonic, expiratory wheeze
What test is diagnostic of asthma?
low peak expiratory flow rate
low FEV1/FEV
a 12% increase in FEV1 following salbutamol
What is the MRC Dyspnoea scale?
1- not troubled by breathlessness except on strenuous exercise
2- short of breath when hurrying or walking uphill
3- walks slower than contemporaries on flat ground, or has to stop to catch breath when walking at own pace
4- stops for breath after walking about 100m or after a few minutes on level ground
5a- too breathless to leave the house but independent of ADLs
5b - housebound and dependent on others for ADLs
What is lobar pneumonia?
Pneumonia with consolidation confined to one or more lung lobes
What is broncho pneumonia?
Diffuse and patchy pneumonia which originates from the airways and spreads into lung tissue. On CXR there tend to be multiple small nodular or reticulonodular opacities which tend to be patchy and/or confluent
What is aspiration pneumonia?
pneumonia secondary to aspiration of food, drink, saliva or vomit. On CXR there may be airspace opacification in a lobar or segmental distribution
What is the CURB-65 score?
scoring system for hospital acquired pneumonias
C- new mental confusion
U- Urea >7mmol/L
R- Resp rate over 30/min
B - blood pressure <90/60
65 - age over 65yrs
a score of 2 or more is an indication to be admitted to hospital
What is a transudate? What causes transudative effusions in the pleura?
Serous fluid with a low protein content - <30g/L
Causes include cardiac failure, hypoalbuminaemia, nephrotic syndrome, sepsis
What is exudate? What causes exudative accumulations in the pleura?
Serous fluid with a high protein content, >30g/L
Neoplasm, TB or Pneumonia, connective tissue disease, rheumatoid athritis,
4 causes of low PaO2
Hypoventilation
Diffusion Impairment
Shunt
V/Q Mismatch
What is massive haemoptysis?
> 240mls in 24 hours
>100mls over consecutive days
What is a mild asthma attack?
PEFR > 75%
No features of severe asthma
What is a moderate asthma attack?
PEFR 50-75% predicted
No features of severe asthma
What is a severe asthma attack?
PERF 33 -50% Or any of the following: Cannot complete sentences in one breath Resp rate over 25/min Heart rate over 110/min
What is a life threatening asthma exacerbation?
10 thing
PEFR < 33% Or any of the following: Sats < 92% or ABG pO2 < 8kPa Cyanosis Poor respiratory effort Near or fully silent chest Exhaustion Confusion Hypotension Arrhythmia Normal PCO2
What is a near fatal asthma attack?
Raised PCO2
WHO performance scale
0- normal, fully active
1- restricted in physically strenuous activity
2- ambulatory and capable of all self care but not able to work up and about more than 50% of waking hours
3 - capable only of limited self care, confined to bed or chair more that 50% of waking hours
4- completely disabled, no self care, confined to bed or chair
5- dead
What are the absolute contraindications for thrombolysis? (6)
Haemorrhaging or ischaemic stroke in last 6 months CNS neoplasm Recent trauma or surgery GI bleed in last month Bleeding disorder Aortic dissection
What are the relative contraindications to thrombolysis?
Warfarin
Pregnancy
Advanced liver disease
Infective endocarditis
What are the criteria for discharge following an asthma exacerbation? (8)
- PEFR >75%
• Stop regular nebulisers for 24 hours prior to discharge
• Inpatient asthma nurse review to reassess inhaler technique and adherence
• Provide PEFR meter and written asthma action plan
• At least 5 days oral prednisolone
• GP follow up within 2 working days
• Respiratory Clinic follow up within 4 weeks
• For severe or worse, consider psychosocial factors
Causes of eosinophilia (7)
Asthma COPD Hay fever Allergic bronchopulmonary aspergillosis Drugs e.g. recurrent antibiotics Vasculitis Eosinophillic pneumonia
What is the aim of long term oxygen therapy?
Prevent renal and cardiac damage due to hypoxia
What are the requirements for long term oxygen therapy?
pO2 consistently below 7.3 kPa
pO2 consistently below 8kPa with cor pulmonale
Must be a non-smoker who doesn’t retain high levels of CO2
What is Kartagener syndrome?
Triad of bronchiectasis, sinusitis and situs inversus
What are the causes of bronchiectasis?
Post infective - whooping cough, TB
Immune deficiency - hypogammaglobulinaemia
Genetic - CF, kartagener
