Resp Misc. Flashcards
How is ventilation in the lungs achieved?
By the expansion of the thoracic cavity and lungs during inspiration. This reduces the intra alveolar pressure and transmural pressures, which encourages gas to travel down the pressure gradient from the atmosphere into the lungs.
How is expiration achieved?
By the recoil of the lungs following active expansion
Is expiration an active or passive process?
Largely passive
In expiration, how is recoil achieved?
Due to elastic connective tissue and alveolar surface tension
How is alveolar surface tension created?
By the attraction between the water molecules at the liquid – air surface, which creates a natural tendency for the alveoli to collapse
What reduces alveolar surface tension?
The presence of a pulmonary surfactant, which acts to intersperse the water molecules on the surface of the lungs
What is meant by the term ‘tidal volume’?
The volume of air entering and leaving per breath
What is meant by the term ‘inspiratory reserve volume’?
The extra volume which the lungs can inspire above tidal volume
What is meant by the term ‘inspiratory capacity’?
The maximal volume of air that can be inspired: TV + IRV
What is meant by the term ‘expiratory reserve volume’?
Extra volume of air that can be expired above tidal volume
What is meant by the term ‘residual volume’?
Minimum volume of air remaining in the lungs after expiration
What is meant by the term ‘functional residual volume’?
Volume of air in lungs at the end of normal, passive respiration (RV+ ERV)
What is meant by the term ‘vital capacity’?
Maximal volume of air that can be moved out of the lungs following a maximal respiration
What is meant by the term ‘total lung capacity’?
Maximum volume of air that the lungs can hold
For a healthy young male, what is the average tidal volume?
500mls
For a healthy young male, what is the average inspiratory reserve volume?
3000mls
For a healthy young male, what is the average inspiratory capacity?
3500mls
For a healthy young male, what is the average expiratory reserve volume?
1000mls
For a healthy young male, what is the average reserve volume?
1200mls
For a healthy young male, what is the average functional reserve capacity?
2200mls
For a healthy young male, what is the average vital capacity?
4500mls
For a healthy young male, what is the average total lung capacity?
5700mls
How do you calculate pulmonary ventilation?
Tidal volume * Respiratory rate
What is meant by the term ‘anatomical dead space’?
The volume of air that remains in the airways and doesn’t pass into the alveoli
What is meant by the term ‘alveolar dead space’?
The alveoli which are ventilated but not perfused and therefore cannot take part in respiration
What are the four main factors affecting ventilation?
Partial pressure of O2 / C02
Diffusion coefficient
Surface area
Membrane thickness
What is the majority of oxygen bound to?
Haemoglobin
What is the Bohr effect?
It describes a rightward shift in 02 dissociation, which means more oxygen is unloaded at the same PC02
What mediates the Bohr effect?
Increased P02, temperature, 2,3-Bisphosphoglyceric acid and acidosis
What are the three way carbon dioxide can be transported?
Free C02
Carb-amino compounds
Bicarbonate
What is the primary driver of respiration?
The pre-botzinger complex in the medulla
What is the principle chemical controller of respiration?
Central chemoreceptors
What is the role of chemoreceptors?
They act to increase respiration in response to increase PC02 and H
Where are peripheral chemoreceptors found?
In aortic and carotid bodies
What is a peak flow test?
A pulmonary function test that measures an individuals maximum speed of expiration, with variation occurring with age, height and sex
What is the average peak flow for an adult male?
550 - 600 L/min
What is the average peak flow for an adult female?
450 - 500 L/min
What is the effect on peak flow in obstructive lung disease?
Reduced
What is the effect on peak flow in restrictive lung disease?
None
What is a spirometry?
Effort dependent tests of dynamic lung volumes
What volumes are measured in a spirometry?
Forced vital capacity (FVC)
Forced expiratory volume in 1 second (FEV1)
Forced expiratory ratio (FER) – FEV1/FVC ratio
What is the effect on FVC in restrictive lung disease?
Decreased
What is the effect on FEV1 in restrictive lung disease?
Decreased
What is the FER in restrictive lung disease?
> 75% (normal)
What is the effect on FVC in COPD?
Decreased
What is the effect on FEV1 in COPD?
Decreased
What is the FER in COPD?
<75% (decreased)
What is the effect on FVC in Asthma?
None
What is the effect on FEV1 in Asthma?
Decreased
What is the FER in COPD?
<75% (decreased)
Why does FER not fall in restrictive lung disease?
Because the decrease in both FVC and FEV1 is proportional
Why does FER fall in obstructive lung disease?
Because the decrease in FEV1 is more than in FVC, with this disproportionate fall resulting in a decrease in FER
What does the ‘bronchial challenge’ look at?
The body’s response of FEV1 to B2 agonists
What do the results of the ‘bronchial challenge’ allow?
Asthma to be distinguished from COPD
What fall in FEV1 during the bronchial challenge is indicative of asthma?
> 15% increase
What fall in FEV1 during the bronchial challenge is indicative of COPD?
<15% increase
What does the transfer factor test do?
It measures the diffusion capacity of the lungs by measuring the amount of carbon monoxide diffusion that occurs in a single breath
In a patient with asthma, what results would be expected from the transfer factor test?
Normal
In a patient with restrictive lung disease, what results would be expected from the transfer factor test?
Reduced
In a patient with emphysema, what results would be expected from the transfer factor test?
Reduced
What % of oxygen does a nasal cannula give?
24-40%
What % of oxygen does a simple face mask give?
40-60%
What % of oxygen does a blue venturi mask give?
24%
What % of oxygen does a white venturi mask give?
28%
What % of oxygen does a yellow venturi mask give?
35%
What % of oxygen does a red venturi mask give?
40%
What % of oxygen does a green venturi mask give?
60%
What % of oxygen does a non rebreather give?
up to 85%
What flow rate is used for nasal cannulas?
Up to 6 litres
What flow rate is used for simple face masks?
5 -15 litres
What flow rate is used for non rebreather masks?
15 litres
What is the benefit of using venturi masks?
It is the most precise form of oxygen delivery
What oxygen mask should be used in an emergency situation?
Non rebreather
What oxygen mask should be used in type 1 respiratory failure?
Standard mask, yellow, red or green venturi (35-60% oxygen)
What oxygen mask should be used in type 2 respiratory failure?
Titrate oxygen starting with the blue venturi (24%), increase to white (28%) if no response is seen
What is the oxygen level aim in type 1 respiratory failure?
94 – 98%
What is the oxygen level aim in type 2 respiratory failure?
88 – 92%
In type 2 respiratory failure what should be checked prior to starting oxygen?
ABGs
