Respiratory Physiology 3 Flashcards
Define ANATOMICAL DEAD SPACE
The volume of gas occupied by the conducting airways and this gas is not available for exchange.
What are the 2 ways to describe VENTILATION?
Pulmonary (Minute) ventilation
Alveolar ventilation
Define PULMONARY (minute) VENTILATION
total air movement into/out of lungs (relatively insignificant in functional terms)
Define ALVEOLAR VENTILATION
fresh air getting to alveoli and therefore available for gas exchange (functionally much more significant!) (Value of 4200)
Under normal conditions what is the relationship between RESTING P02 and PCO2?
remain fairly constant
What happens during HYPER-VENTILATION (increased alveolar ventilation) ?
PO2 rises to about 120 mm Hg and PCO2 falls to about 20 mmHg.
What happens during HYPO-VENTILATION (decreased alveolar ventilation)
PO2 falls to 30 mmHg and PCO2 rises to 100 mmHg.
What is the normal alveolar partial pressure of O2?
100mmHg (13.3kPa)
What is the normal alveolar partial pressure of CO2?
40mmHg (5.3kPa)
What is the blood supply to the lungs?
Pulmonary artery carries deoxygenated blood AWAY from the heart to the lungs.
Pulmonary vein carries oxygenated blood TOWARDS the heart from the lungs.
What is pulmonary circulation opposite in function to?
Systemic circulation
It delivers CO2 to the lungs and picks up O2.
How is BRONCHIAL CIRCULATION (nutritive) supplied?
via the bronchial arteries arising from systemic circulation to supply oxygenated blood to lung tissues
What does the PULMONARY CIRCULATION (gas exchange) consist of?
L&R pulmonary arteries originating from the right ventricle.
Entire cardiac output from RV
What does the PULMONARY CIRCULATION supply?
The dense capillary network surrounding the alveoli and returns oxygenated blood to the left atrium via the pulmonary vein.
What is PaO2
partial pressure of oxygen in arterial blood
What is PACO2
Partial pressure of carbon dioxide in alveolar air
What is the rate of diffusion across the membrane directly proportional to?
- the partial pressure gradient
- gas solubility
- the available surface area
What is the rate of diffusion across the membrane inversely proportional to?
the thickness of the membrane
What is EMPHYSEMA?
Destruction of alveoli reduces surface area for gas exchange and loss of elasticity
What is Fibrotic lung disease?
Thickened alveolar membrane slows gas exchange.
Loss of lung compliance may decrease alveolar ventilation
What is PULMONARY OEDEMA?
Why may Arterial PCO2 be normal?
Fluid in interstitial space increases diffusion distance.
due to higher CO2 solubility in water
What is ASTHMA?
Over reactive constriction of bronchial smooth muscle
Increased airway resistance decreases airway ventilation
What is an obstructive lung disorder?
Obstruction of air flow, especially on expiration
Increases the work of expiration
What is a RESTRICTIVE lung disorder?
Restriction of lung expansion
Increases the work of inspiration
— Loss of lung compliance
Give examples of RESTRICTIVE lung disorders
- Fibrosis: formation of excess fibrous connective tissue creates a “stiff” lung.
~ Idiopathic (cause unknown)
~ Asbestosis (and other occupational origins e.g. coal dust) - Infant Respiratory Distress Syndrome: (insufficient surfactant production)
- Oedema
- Pneumothorax
What is SPIROMETRY?
Technique commonly used to measure lung function
Measurements can be classed as static (where the only consideration made is the volume exhaled) or dynamic (where the time taken to exhale a certain volume is what is being measured)
