Transition Week Flashcards
Functional Residual Capacity?
Volume of air left in lungs after normal, passive expiration.
FRC = Residual Volume + Expiratory Reserve Volume.
How does obesity affect FRC:
Decreases due to pressure on diaphragm etc.
How does COPD affect FRC:
Increase, emphysema causes more air-trapping. Elastic recoil of lung is lost.
What % of total lung capacity is FRC:
40%
Forced Vital Capacity?
Maximum volume of air that can be moved out during a single breath following a maximal inspiration.
FVC = IRV+TV+ERV
Total Lung Capacity?
Maximum volume of air that the lungs can hold at the end of maximum inspiration.
TLC = Vital Capacity + Residual Volumd
Can you measure residual capacity on spirometry?
NO
Therefore you also cannot measure total lung capacity this way
Where is respiratory rhythm generated?
in the medulla
Role of peripheral chemoreceptors in respiration?
Sense tension of oxygen and carbon dioxide and H+in th el
Role of peripheral chemoreceptors in respiration?
Sense tension of oxygen and carbon dioxide and H+in the blood
Role of central chemoreceptors in respiration?
Situated near surface of medulla on brainstem. Respond to H+ conc in CSF.
Hypoxic drive of respiration?
Effect via peripheral chemoreceptors. Stimulated when PO2 falls to low. Important in high altitudes.
Process of inspiration?
Active process.
Volume of thorax increases due to contraction of diaphragm. External intercostal muscle contraction lifts the rives and moves out the sternum.
Process of inspiration?
Active process.
Volume of thorax increases due to contraction of diaphragm. External intercostal muscle contraction lifts the rises and moves out the sternum.
Intrapleural pressure falls so air rushes in.
Forces promoting alveolar collapse?
Elasticity of stretched pulmonary connective tissue fibres.
Alveolar surface tension
Dynamic airway compression?
Pressure surrounding airway exceeds pressure within airway. Occurs during inhalation to increase airway pressure upstream and increase driving pressure between alveolus and alveoli.
Makes expiration more difficult in patients struggling with airway obstruction but no problems in normal people.
Compliance
Measure of effort that has to go into stretching the lungs in inspiration.
How do emphysema and lung collapse affect gas exchange?
Decrease surface area = SOB
How do pulmonary fibrosis, pulmonary oedema (HF) and pneumonia affect gas exchange?
Increase thickness of gas exchange membranes= SOB
Cardiac Output:
Volume of blood pumped by each ventricle per minute.
CO = SV x HR
Stroke volume:
Volume of blood ejected by each ventricle per heart beat.
SV = EDV-ESV.
Changes are due to changes in diastolic length of myocardial fibres, which are due to volume of blood at the end of diastole.
Frank-Starling Mechanism?
the more the ventricle is filled with blood during diastole, the greater the volume of ejected blood will be during the resulting systolic contraction
Frank-Starling Mechanism?
the more the ventricle is filled with blood during diastole, the greater the volume of ejected blood will be during the resulting systolic contraction
How does heart failure affect Frank-Starling Curve?
Shifts curve to right. Larger end-diastolic pressure but lower stroke volume
What should FEV/FVC ratio be in COPD post bronchodilator?
<70%
Granuloma:
Organised collection of activated macrophages and lymphocytes.
Differentials of lung granuloma:
Sarcoidosis
Mycobacterial disease (TB, leprosy)
Silicosis
Foreign bodies
