Respiratory physiology 3 Flashcards
What is ventilation?
Movement of air in and out of the lungs
What is perfusion?
Blood flow reaching alveoli
What is alveolar ventilation?
Volume of fresh air that reaches the alveoli
How is total pulmonary ventilation calculated?
Tidal volume x respiratory rate
Why is the partial pressure of O2 higher in the air than in the alveoli?
Because the fresh air is partially diluted in dead space.
What is the normal alveolar partial pressure of O2 and CO2?
PAO2 = 100mmHg
PACO2 = 40mmHg
What is the comparison of ventilation at the base and apex of the lungs?
Ventilation is greater at the vase than the apex, this is because at the base the alveoli are ‘squashed’ allowing them to have greater capacity to expand.
What is bronchial circulation?
Bronchial arteries provide oxygenated blood to lung tissue
What is the comparison of blood pressure in systemic circulation and pulmonary circulation?
Systemic circulation has much higher pressure (120/80 mm Hg) than pulmonary circulation (25/10mmHg)
Ideally, what is partial pressure in the alveoli equal to?
Partial pressure in arterial circulation
What is the comparison of the partial pressure gradient of O2 and the partial pressure gradient of CO2?
PO2 gradient is 10x greater than PCO2 gradient.
(PO2 - 100 to 40mmHg, PCO2 -46 to 40mmHg)
What is more water soluble, CO2 or O2?
CO2
Elastic fibres are never located between type 1 alveolar cells and capillary cell, why is this important?
To allow for a short gas diffusion distance
What is emphysema?
Destruction of alveoli, reduces surface area for gas diffusion.
Also causes loss of elasticity
What is fibrotic lung disease?
Thickened alveolar membrane slows gas exchange
What is pulmonary oedema?
Increase in interstitial fluid causes increased diffusion distance
What is asthma?
Increased airway resistance caused by constriction of bronchioles, causes decreased ventilation
What is the main cause of emphysema?
Smoking
What is an obstructive lung disease?
Disease which causes obstruction to air flow (effect expiration)
What is restrictive lung disease?
Restriction to lung expansion, caused by loss of compliance (effects inspiration)
Give 2 examples of obstructive lung disorders
Asthma
COPD (chronic bronchitis and emphysema)
Give 4 example of restrictive lung disorders
IPD
Infant respiratory distress syndrome
Pulmonary oedema
Pneumothorax
What piece of equipment can be used to measure lung function?
Spirometer
In a healthy young male what is the normal value for FEV1/FVC?
FEV1 - Forced expiratory volume in 1 second, 4l
FVC - forced vital capacity, 5L - FEV1/FVC = 80%
What effect does obstructive disorders have on the FEV1/FVC ratio?
Decrease
What effect does restrictive disorders have on the FEV1/FVC ratio?
Constant or sometimes increased.
