Lung Physiology Flashcards
How is the minute volume of lungs calculated?
VM = Tidal Volume X Respiratory Rate
VM = Alveolar ventilation + Dead space ventilation
What is alveolar ventilation?
The protiono of the minute volume that contributes to gas exchange
Note: Some air is wasted in large airways/ dead space
What is ventilation / perfusion mismatch?
Normally ventilation to perfusion ratio is equal (ratio of 1)
Diseased lung may have a mismatch of ventilation to perfusion.
Healthy Lung: V/Q = 1
Shunt: Q>V (perfusion greater than ventilation)
Dead space: V>Q (Ventilation greater than perfusion)
What proportion of tidal volume does not contribute to alveolar ventiltion?
30%
This is termed “anatomical dead space”
What is anatomical dead space?
Areas of lung that do not contribute to alveolar ventilation
What is physiological dead space?
Areas of lung that ventilate but do not have blood supply
Redcued area of lung to eliminate CO2
E.g. Ephysema
V > Q
What is CO2 shunting and how does it occur?
Areas of lung that are adequately perfused but not ventilated. Sets up concentration gradient that increases CO2
Blood leaving lungs have higher levels of CO2 and lower levels of O2
e.g. Pneumonia - consolidation of lung
Q>V
What does CO2 retention commonly suggest?
Reduced alveolar ventilation
What is a sensitive test for pulmonary shunting and why?
Oxygen saturation
Blood/circulation is unable to compensate for reduced alveolar ventilation, as O2 binds complete to haemoglobin
Patient’s become hypoxic
Why do patients with increased dead space become hypoxic?
Increased dead space may result in hypoperfusion and ineffective elimination of CO2
Patient’s become hypoxic
What may cause compensating patients with tachypnoea to become hypercapnic?
Exhaustion
How does vessels enter the lungs?
Viathe lung hillums
What effect does the autonomic nervous system have on airways?
Sympathetic: Bronchodilation
Parasympathetic: Vasoconstriction
Describe the layers covering the lungs?
Thoracic cage
Parietal pleura
(Pleural fluid)
Visceral pleura
Lung
What are the bronchioles/ trachea’s epithelium?
Cilliated columnar epithelial cells
Goblet cells + Submucosal glands
Goblet cells + gland secrete gel phase (layer)
Gel phase sits on sol phase (pericellular fluid)
What is the tidal volume?
Volume of air drawn into and out of lungs during normal breathing
What is the vital capacity?
Maximum tidal volumes
(individual breathes in and out as much as possible)
What is the inspiratory reserve volume?
Tidal volume (inspired) + whatever an individual can maximally inspire
What is the expiratory reserve volume?
Tidal volume (expiratory) + whatever an individual can maximially expire
