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48 Cards in this Set
- Front
- Back
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define pulmonary ventilation |
the movement of air into and out of the lungs |
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What is intrapulmonary pressure? |
pressure within alveoli |
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what is intrapleural pressure? |
always more negative that alveolar the pressure between the lungs and pleura the elastic nature of the lung tissue versus the ribcage and thorax trying to pull apart visceral from parietal pleura |
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what is the value of intrapleural pressure? |
756mmHg |
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What is the value for intrapulmonary pressure? |
760mmHg |
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What is the collapsing pressure of the lungs? |
4mmHg the pressure difference between intrapulmonary and intrapleural pressure |
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What is the role of the external intercostal muscles? |
with the first rib fixed there are two movements forward movement of the lower end of the sternum upwards and outwards movement of the ribs |
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How much does the volume of the thorax normally increase? |
500ml (normal tidal volume) |
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How much does intrapleural pressure drop by on inspiration? |
6mmHg |
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How much does intrapulmonary pressure decrease by on inspiration |
1mmHg |
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Which muscles are involved in forced expiration? |
the abdominal wall contracts the internal intercostals pull the ribs downwards |
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What is energy used for in breathing? |
contract muscles of inspiration stretch elastic elements overcome airway resistance overcome frictional forces arising from viscosity of the lung and chest wall overcome inertia of air and tissues |
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What is most significant form of non elastic resistance? |
airway |
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What determines air flow? |
pressure divided by resistance |
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What increases the likelihood of turbulent flow? |
increased velocity large diameter |
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Which part of the airway is more likely to be turbulent? |
the upper airway |
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Where is the greatest resistance to flow? |
the segmental bronchi because cross sectional area is low and airflow is turbulent |
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What is the flow like at the smallest airways? |
laminar and resistance is lown |
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What happens to airway resistance on inspiration? |
it decreases |
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Which condition is an over inflated chest characteristic of? |
COPD |
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What is compliance? |
the distensibility or ease of stretch of lung tissue when external forces are applied of the ease with which the lungs expand under pressure |
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What does high compliance mean? |
Large change in volume for given change in pressure |
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what are the major determinant of compliance? |
alveolar surface tension elastic components |
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In a healthy individual, what is compliance? |
1L/kPa |
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What will reduce compliance? |
replacing elastic tissue with non elastic tissue blocking smaller respiratory passages increasing alveolar surface tension decreasing the flexibility of the thoracic cage or its ability to expand |
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What will increase compliance?
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pulmonary emphysema due to alveolar rupture creating larger air spaces impaired elastic recoil leads to poor deflation |
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At what volume is lung compliance greatest? |
lower volumes |
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How does lung volumes at the base compare to the apex? |
at the base lung volume is less because it is compressed |
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For the same intrapleural pressure, which area of the lung expands most? |
base |
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What causes alveolar surface tension? |
The polar nature of water causes surface tension but lungs lined with pure water would collapse. Alveoli have surfactant to prevent this |
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Where is surfactant produced? |
in type 2 alveolar cells |
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What makes up surfactant and what is its purpose? |
A mixture of phospholipids that prevent alveolar collapse reduces surface tension to increase lung compliance |
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What is the effect of increase lung compliance? |
allows a greater expansion for a given pressure change |
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What are the 4 volumes to consider in respiration? |
1. tidal volume 2. inspiratory reserve volume 3. expiratory reserve volume 4. residual volume |
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what is tidal volume? |
the volume of air breathed in and out in a single breath |
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What is inspiratory reserve volume? |
the volume breathing in by max inspiration at the end of normal inspiration |
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What is expiratory reserve volume? |
the volume breathed out at the end of normal expiration |
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What is residual volume? |
the volume of air in lungs at the end of max expiration |
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What are the 4 pulmonary capacities? |
1. inspiratory capacity 2. functional residual capacity 3. vital capacity 4. total lung capacity |
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What is inspiratory capacity? |
tidal volume plus inspiratory reserve volume thee air breathed in by max inspiration at the end of normal expiration |
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What is functional residual capacity? |
The expiratory reserve volume plus the residual volume the air left in the lungs after normal expiration |
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What is the purpose of functional residual capacity?
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acts as a buffer against extreme changes in alveolar gas levels |
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What is vital capacity? |
the air that can be breathed by max inspiration following max expiration |
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What is total lung capacity? |
vital capacity plus residual volume only a fraction of TLC is used in normal breathing |
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What is dead space? |
anatomical areas of airway that are not involved in gas exchange |
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how much of the lung on average is dead space? |
150ml |
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when might physiological dead space increase?
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in disease when ventilation:perfusion ratios alter |
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How does physiological dead space compare to anatomical dead space in a normal person? |
they are about the same because alveolar dead space is low physiological dead space is areas of the lung that could be involved in gas exchange but aren't anatomical dead space is areas where gas exchange will not occur |
