Ventilation Mechanics and Lung Volumes - Anatomy and Physiology
- Which two volumes make up the functional residual capacity?
- Expiratory reserve volume plus residual volume.
- Why is intrapleural pressure normally negative?
- The lungs tend to recoil inward while the chest wall tends to spring outward, pulling the pleural layers apart.
- What is lung compliance, and how does pulmonary fibrosis change it?
- Compliance is the change in lung volume per change in pressure. Fibrosis decreases it, making the lungs stiffer.
- Why is quiet expiration a passive process?
- Inspiratory muscles relax, and the elastic recoil of the lungs and chest wall reduces lung volume.
- Tidal volume is 500 mL and respiratory rate is 12 breaths per minute. What is minute ventilation?
- 6,000 mL/min (6 L/min), because .
- Which lung volume cannot be measured with simple spirometry?
- Residual volume, so capacities that include it, such as FRC and TLC, also cannot be measured that way.
- Which lung capacity is the sum of tidal volume, inspiratory reserve volume and expiratory reserve volume?
- Vital capacity.
- Which muscle is the main muscle of quiet inspiration, and which nerve supplies it?
- The diaphragm, supplied by the phrenic nerve (C3 to C5).
- Air enters the pleural space through a chest wound. What happens to the lung on that side, and why?
- It collapses. Intrapleural pressure rises to atmospheric, so nothing opposes the lung's elastic recoil.
- How does the FEV1/FVC ratio typically differ between obstructive and restrictive lung disease?
- It is reduced in obstructive disease and normal or increased in restrictive disease.
- Tidal volume is 500 mL, dead space is 150 mL and rate is 12 breaths per minute. What is alveolar ventilation?
- 4,200 mL/min, because .
- How does Boyle's law explain airflow into the lungs during inspiration?
- As the thoracic cavity expands, lung volume rises and alveolar pressure falls below atmospheric pressure, so air flows in.