Respiratory Physiology 1 Flashcards
Describe the respiratory cycle
The oxygen saturated blood moves from lungs to heart to capillary beds to muscles. While Carbon goes the reverse.
Explain how the pressure in the pleural space of the lungs is negative
It is a sealed sac, with the potential space between visceral and parietal pleura is touching, with a little serous fluid within.
As thoracic cavity is larger than lungs, the lungs are semi-expanded at rest, which means that there is recoil from the lungs which want to collapse and this generates the negative pressure in the pleural space.
Describe how inspiration and expiration affects pressures in the lungs and pleural space
Inspiration = a further decrease of intrapleural pressure, from the diaphragm and other inspiratory muscles contracting.
The alveolar which is pulled by the pleural space also becomes more negative than the atmosphere
Expiration = relaxing of the diaphragm, contraction of intercostal muscles
Describe how alveolar pressure changes through a respiratory cycle
Define lung volumes and capacities.
4 different volumes?
4 capacities (two or more volume combined)
4 different volumes Inspiratory reserve volume Tidal volume Expiratory reserve volume Residual volume
4 capacities (two more more volumes combined) Inspiratory capacity ( IRV + TV/Vt) Functional residual capacity (FRC) Vital capacity (IRV + TV/Vt +ERV) Total lung capacity (TLC)
Identify the most important factor contributing to resistance
Radius of the airways is the most important factor
Describe how obstructive lung disease affect airways with an example
Eg asthma of horse or cat
decrease radius of airways and increased mucous production
Which increases resistance
Early dynamic small airway closure
Ultimately leads to reduced expiration capacity and increased residual volume
Describe minute and alveolar ventilation
which is more important?
Minute ventilation
volume of air reaching the alveoli per minute
VE- BF x VT
Alveolar ventilation
taking into account dead space (in trachea)
Va = Bf x (VT - VD)
Alveolar ventilation is more important as dead space is not functional alveolar, but minute ventilation is easier to measure. Changes in minute ratio still has functional use
Being mindful of the ratio of dead space and anaesthesia tubing is also dead space
Define compliance and elastance
Compliance = ability of lungs to stretch and expand
volume/pressure = compliance
Due to elastic fibres + surface tension
C facilitates “appropriate functional residual capacity”
Elastane = the reciprocal of compliance
pressure change required to elicit a volume change
Therefore increased elastane = increased work of breathing
Describe the principle of surface tension
Water is drawn to other water molecules more than air, thus water clumps together
Explain how surface tension is generated in the alveoli
Alveoli fluid/water covers the alveolar surface, because of the air-water interface
Describe the role of type II pneumocystis and surfactant
Type II pneumocystis produces surfactant
Surfactant lines the alveoli to reduces the surface tension by reducing air-water interface in the alveoli
Explain the effect of surfactant on surface tension in the lung
As due to the law of Laplace, the larger the alveoli the easier it is to inflate as there is less surface tension.
IMPORTANT = Surfactant makes it easy to inflate the lungs regardless of size of the alveoli
Define work of breathing
Energy required to perform tidal ventilation over a set period of time
Describe how lung disorders affect the work of breathing
