Lung Function Flashcards
Why is it important to know about the respiratory system ?
- integral to safe dental treatment of patients with respiratory problems
- general anaesthetic can lead to hypoxia
- analgesics and narcotics are respiratory depressants
- drilling of the teeth can cause asthma attacks
What is the function of the respiratory system ?
• gas exchange - intake of oxygen and removal of carbon dioxide
• contributes to regulation of blood pH
• filters and heats inspired air
• metabolises inhaled chemicals
• receptors for sense of smell
What are the functions of the elastic fibres on the alveoli ?
They give the lungs elastic recoil
Describe the structure of the respiratory system
- trachea > bronchi > bronchioles > terminal bronchioles > respiratory bronchioles > alveolar ducts > alveolar sacs
- 2 zones : conducting zone and respiratory zone
Summarise the function of the conducting zone
- no gas exchange taking place
- transfers air to and from the alveoli
- warms and humidifies inspired air
- filters and removes foreign material
Summarise the function of the respiratory zone
- gas exchange
- oxygen delivery to the blood
- carbon dioxide removal from the blood
Which structures of the respiratory system are part of the conducting zone ?
- trachea
- bronchi
- bronchioles
- terminal bronchioles
Which types of cells are found in the bronchial epithelium ?
- ciliated cells
- goblet cells (more)
- basal cells
- clara cells (less)
Which types of cells are found in the bronchiolar epithelium ?
- ciliated cells
- very very few goblet cells
- lots of clara cells
Which types of cells are found in the alveolar epithelium ?
- type 1 alveolar cells
- type 2 alveolar cells
- alveolar macrophage
Why is the conducting zone known as dead space ?
Because it is not involved in gas exchange
What are the 2 types of dead space ?
- anatomical dead space
- physiological dead space
Describe the function of the anatomical dead space
- the conducting airways that deliver air to the alveoli
- the volume is determined by the geometry of the airway network
Describe the function of the physiological dead space
- volume of the lung that does not participate in gas exchange
- measured by the functional assessment of the lung
What is the estimate for the volume of the anatomical and physiological dead space in healthy subjects ?
150 - 180 ml
How are lung volumes measured ?
A spirometer can be used to measure changes in the volume of air in the lungs
What is the tidal volume ?
It is the normal air moving in and out of the lungs (normal breathing at rest)
- 0.5 litres
What is the inspiratory reserve volume ?
The amount of air that can be breathed in (maximal inhalation)
- 3.1 litres
What is the expiratory reserve volume ?
- amount of air that can be breathed out (maximal exhalation)
- 1.2 litres
What is the difference between capacity and volume ?
capacity is the sum of volumes that can be divided into different volumes whereas volume is a set value which cannot be subdivided
Which values can’t be measured using spirometery ?
- functional residual capacity (2.4 litres)
- residual volume (1.2 litres)
- total lung capacity (6 litres)
They can’t be measured using spirometery because the air can’t be expelled
What are the values of inspiratory capacity and vital capacity ?
• inspiratory capacity - 3.6 litres
• vital capacity - 4.8 litres
What is functional residual capacity ?
- air remaining at the end of normal exhalation
- provides a buffer and prevents breath to breath fluctuations in alveolar gas composition
- air entering the lungs mixes with air remaining in the lungs
- 2.4 litres
What is residual volume ?
- air remaining in the lungs at the end of maximal exhalation
- 1.2 litres
What is tidal volume ?
Tidal volume = air in the dead space + air in the alveoli
(air entering the lungs ventilates both the dead space and the alveoli)
What is alveolar ventilation ?
- It is the volume of gas entering the alveoli every minute
- alveolar ventilation = (tidal volume - dead space) x respiratory rate
- typical value at rest =4200 ml/min
How can alveolar ventilation be increased ?
- increasing tidal volume
- increasing respiratory frequency
What is the typical value of expired ventilation/minute ventilation ?
6000 ml/min
What is hypoventilation ?
- breathing in and out too slowly compared to what the body needs
- decrease in ventilation without similar decrease in oxygen consumption or carbon dioxide production
How can hypoventilation occur ?
(Hypercapnia)
- in disease states which physiological dead space
- when respiratory muscles are paralysed or the chest wall is damaged
- when tidal volume is reduced by CNS depression
What is hyperventilation ?
- breathing in and out too quickly for the bodies needs
- ventilation in excess metabolic needs or carbon dioxide exhaled at a greater rate than production
How can hyperventilation occur ?
(Hypocapnia)
- during acute asthma attacks
- under conditions of stress
- at altitude
