LUNG VOLUMES & CAPACITY
| A | Inspiratory capacity minus the inspiratory reserve volume | |
| B |
Total lung capacity minus the reserve volume |
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| C |
Functional residual capacity minus residualvolume |
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| D |
Vital capacity minus expiratory reserve volumes |
Tidal volume is calculated using which of the following equation?
| A |
Inspiratory capacity minus the inspiratory reserve volume |
|
| B |
Total lung capacity minus the reserve volume |
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| C |
Functional residual capacity minus residualvolume |
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| D |
Vital capacity minus expiratory reserve volumes |
The inspiratory capacity equals the tidal volume plus the inspiratory reserve volume.
IC=TV+IRV
Therefore Tidal Volume = Inspiratory Capacity – Inspiratory Reserve Volume
Tidal volume refers to the amount of air that moves into the lungs with each inspiration. Inspiratory reserve volume refers to the amount of air inspired with a maximal inspiratory effort in excess of tidal volume.
Ref: Review of Medical Physiology, 22nd Edition By Wiiliam F Ganong, Page 651; Guyton and Hall Medical Physiology, 10th Edition, Page 437.
| A |
Inspiratory capacity minus the inspiratory reserve volume |
|
| B |
Total lung capacity minus the reserve volume |
|
| C |
Functional residual capacity minus residual volume |
|
| D |
Vital capacity minus expiratory reserve volumes |
A i.e. Inspiratory Capacity minus Inspiratory Reserve volume
Total lung capacity depends upon :
| A |
Size of airway |
|
| B |
Closing volume |
|
| C |
Lung compliance |
|
| D |
Residual volume |
C i.e. Compliance of lung
Functional residual capacity is:
| A |
Volume remaining after forced expiration |
|
| B |
Tidal volume + volume inspired forcefully |
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| C |
Volume remaining after normal expiration |
|
| D |
Tidal volume + volume expired by forced expiration |
C i.e. Volume remaining after normal expiration
Functional residual capacity of lung is defined as:
| A |
Volume expired after normal expiration |
|
| B |
Volume remaining after forced expiration |
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| C |
ERV + RV |
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| D |
Tidal volume + volume inspired forcefully |
C i.e. ERV + RV
|
VOLUME |
||
|
Tidal volume |
500 m1Q |
Is the air that moves into the lung |
|
(T.V) |
|
n,ith each normal inspiration or the volume of air that moves out of lung with each expiration |
|
Inspiratory |
3300 m1Q |
The air inspired with a maximal |
|
reserve |
|
inspiratory effort in excess of tidal |
|
volume (IRV) |
|
volume |
|
Expiratory |
1000 inlQ |
The air expelled with a maximal |
|
reserve |
|
expiratory effort in excess of tidal |
|
volume (ERV) |
|
volume |
|
Residual |
1200 m1Q |
The amount of air remaining in the |
|
Volume (RV) |
|
lungs even after forced expiration |
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CAPACITIES |
||
|
Inspiratory capacity I |
3800 ml. |
Total amount of air that can be |
|
C=TV+ IRV |
|
breathed in. |
|
Vital capacity(VC) |
4800 ml. |
Maximal amount of air that can |
|
=TV+ IRV+ERV |
|
be expelled out force fully after a |
|
=IC + ERV |
|
maximal (deep) inspiration |
|
Functional residual |
2200 ml. |
It is the volume of air remaining |
|
capacity |
|
in the lung after normal |
|
FRC=ERV+RV |
|
expiration (after normal tidal expiration) |
|
Total lung capacity |
6000 ml. |
The amount of air present in the |
|
(TLC) |
(4.2-6 |
lung after a maximal inspiration. |
|
=TV+IRV+ERV+RV |
UN) |
This is the maximum volume to |
|
=VC + RV |
|
which the lungs can be expandedQ |
|
=IC + FRC |
|
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March 2013
| A | Additional volume of air that can be inspired forcefully after the end of normal inspiration | |
| B |
Volume of air breathed out of lungs in a single normal quiet respiration |
|
| C |
Additional volume of air that can be expired forcefully after normal expiration |
|
| D |
Volume of air remaining in lungs even after forced expiration |
Ans. D i.e. Volume of air remaining in lungs even after forced expiration
Regarding lung volumes, which of the following is true:
| A |
Functional residual capacity accounts for 75% of total lung capacity |
|
| B |
Residual volume keeps alveoli inflated between breaths |
|
| C |
Vital capacity increases in elderly |
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| D |
Residual volume is about 500 ml |
Ans. B: Residual volume keeps alveoli inflated between breaths
- The amount of air that moves into the lungs with each inspiration (or the amount that moves out with each expiration) is called the tidal volume (500 ml). The air inspired with a maximal inspiratory effort in excess of the tidal volume is the inspiratory reserve volume. (3000 ml)
- The volume expelled by an active expiratory effort after passive expiration is the expiratory reserve volume (1200 ml), and the air left in the lungs after a maximal expiratory effort is a residual volume (1200 ml).
- The space in the conducting zone of the airways occupied by gas that does not exchange with blood in the pulmonary vessels is the respiratory dead space. The vital capacity (4700 ml), the largest amount of air that can be expired after a maximal inspiratory effort, is frequently measured clinically as an index of pulmonary function. It gives useful information about the strength of the respiratory muscles and other aspects of pulmonary function (ERV+TV+IRV).
- The fraction of the vital capacity expired during the first second of forced expiration (FEV1, timed vital capacity) gives additional information; the vital capacity may be normal but the FEV1 reduced in diseases such as asthma, in which airway resistance is increased because of bronchial constriction.
- The amount of air inspired per minute (pulmonary ventilation, respiratory minute volume) is normally about 6 L (500 mL/ breath x 12 breaths/ min).
- The maximal voluntary ventilation (MVV), or, as it was formerly called, the maximal breathing capacity, is the largest volume of gas that can be moved into and out of the lungs in 1 minute by voluntary effort. The normal MVV is 125-170 L/ min.
- Inspiratory Capacity (TV + IRV) = 3500 ml
- Functional Residual Capacity (RV + ERV) = 2400 ml
- Total Lung capacity (RV + VC) = 5900 ml
| A |
Tidal volume |
|
| B |
Residual volume |
|
| C |
Inspiratory reserve volume |
|
| D |
Expiratory reserve volume |
Ans. is ‘b’ i.e., Residual volume.
- Residual air (residual volume) can not be expired (residual volume is the amount of air remaining in the lung after maximum possible expiration), the residual volume cannot be measured by spirometry.
Relaxation volume of lung is documented as ‑
| A |
Functional residual capacity |
|
| B |
Residual volume |
|
| C |
Vital capacity |
|
| D |
Closing volume |
Ans. is ‘a’ i.e., Functional residual capacity
Relaxation volume
- The relaxation volume is the volume of the relaxed respiratory system, i.e., the volume at which the net elastic recoil of the total respiratory system is zero (the elastic recoil of the chest wall is equal and opposite to that of lungs).
- In healthy subjects, this occurs at the end of quiet expiration, i.e., at functional residual capacity.
- Therefore, in healthy adults at rest FRC is essentially equal to the relaxation volume of the respiratory system and FRC is usually treated as synonymous with relaxation volume.
- However, in real sense FRC and relaxation volume are not synonymous terms and, while the two volumes are some times equal, more often they are not, i.e., active or passive mechanisms often operate to make FRC different from relaxation volume.
- For example, neonates have a more compliant (less stiff) chest wall.
- The chest wall thus has less elastic recoil to balance that of the lung, thus decreasing the relaxation volume of the lung.
- FRC then is often maintained above relaxation volume by active mechanisms like inspiratory muscle activity and slowing of expiration.
- Another example where FRC and relaxation volume may differ is in obstructive lung disease where FRC is dynamically determined and may be considerably above relaxation volume.
| A |
2.4 L |
|
| B |
3.6 L |
|
| C |
6 L |
|
| D |
10 L |
Ans. is ‘c’ i.e., 6 L
