13 terms

# 4 Lung volumes and capacities

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Name some of the lung volumes and their abbreviations
1. Tidal volume (TV)
2. Inspiratory volume (IRV)
3. Expiratory volume (ERV)
4. Residual volume (RV)
Lung volumes
1. Tidal volume
2. Inspiratory volume (IRV)
3. Expiratory volume (ERV)
4. Residual volume
1. Volume air inspired and expired with each normal breath
Lung volumes
1. Tidal volume
2. Inspiratory volume (IRV)
3. Expiratory volume (ERV)
4. Residual volume
1. Volume that can be inspired over and above the tidal volume. Used during exercise
Lung volumes
1. Tidal volume
2. Inspiratory volume (IRV)
3. Expiratory volume (ERV)
4. Residual volume
1. Volume that can be expired after the expiration of a tidal volume
Lung volumes
1. Tidal volume
2. Inspiratory volume (IRV)
3. Expiratory volume (ERV)
4. Residual volume
1. Volume that remains in the lungs after maximal expiration
2. Cannot be measured directly by spirometry
Lung volumes
1. Tidal volume
2. Inspiratory volume (IRV)
3. Expiratory volume (ERV)
4. Residual volume
1. Anatomic dead space: Volume in the conducting airways; approx. 150ml
2. Physiologic dead space: Volume that does not participate in gas exchange; approx equal to anatomic dead space, but is rather greater in lung diseases. It is calculated using the following equation:
a. Vd = TV × (pCO₂a - pCO₂e) / pCO₂a
TV-Tidal volume
a-Alvolar
e-expired air
Ventilation rate
1. Minute ventilation is expressed as:
Minute ventilation = TV × Breaths/min
2. Alveolar ventilation is expressed as:
Alveolar ventilation = (TV-Dead space) × Breaths/min
Name some of the lung capacities
1. Inspiratory capacity
2. Functional residual capacity (FRC)
3. Vital capacity (VC) or forced vital capacity (FVC)
4. Total lung capacity (TLC)
Lung capacities
1. Inspiratory capacity
2. Functional residual capacity (FRC)
3. Vital capacity (VC) or forced vital capacity (FVC)
4. Total lung capacity (TLC)
1. Is the sum of tidal volume and inspiratory volume
2. Expressed as: TV + IRV
3. Approx. 3500 ml
Lung capacities
1. Inspiratory capacity
2. Functional residual capacity (FRC)
3. Vital capacity (VC) or forced vital capacity (FVC)
4. Total lung capacity (TLC)
1. Is the sum of expiratory volume and residual volume
2. Expressed as: ERV + RV
3. Is the volume remaining in the lung after a tidal volume is expired (includes the RV so cannot be measured by spirometry directly)
4. Approx. 2300 ml
Lung capacities
1. Inspiratory capacity
2. Functional residual capacity (FRC)
3. Vital capacity (VC) or forced vital capacity (FVC)
4. Total lung capacity (TLC)
1. Sum of tidal volume, inspiratory volume and expiratory volume
2. Expressed as: TV + IRV + ERV
3. Is the volume air that can be forcibly expired after a maximal inspiration
4. Approx. 4600 ml
Lung capacities
1. Inspiratory capacity
2. Functional residual capacity (FRC)
3. Vital capacity (VC) or forced vital capacity (FVC)
4. Total lung capacity (TLC)
1. Is the sum of all four lung volumes
2. Expressed as: TV + IRV + ERV + RV or VC + RV
3. Is the volume in the lungs after a maximal inspiration
4. Includes RV, so it cannot be measured directly with spirometry
5. Approx. 5800 ml
What is forced expiratory volume in one second? (FEV₁) Its clinical role
1. The volume of air that can be expired the first second of a forced maximal expiration
2. FEV₁ is normally 80% of FVC (or VC). It can be expressed as: FEV₁ / FVC = 0.8
3. In obstructive (e.g. asthma/COPD) lung diseases, it is reduced more than FVC so that the ratio decreases
4. In restrictive (e.g. fibrosis) lung diseases, both of them are reduced and the ratio is either normal or increased