Lung volumes are divided into two categories (Figure 135-1). Static lung volumes are measured with slow breathing, whereas dynamic lung volumes are measured with fast or forced breaths. The lung volumes and capacities measured during spirometry are compared with theoretical values that reference values relative to the height, age, and sex of the subject in whom lung volumes are measured.
Spirogram showing static lung volumes.
(Reproduced from Morgan & Mikhail’s Clinical Anesthesiology, 5th ed. McGraw-Hill. Figure 23-5.)
STATIC LUNG VOLUMES AND CAPACITIES
The “static lung volumes” are individual volumes that cannot be further divided (Table 135-1):
Lung Volumes and Capacities
| Favorite Table
| Download (.pdf)
TABLE 135-1 Lung Volumes and Capacities
|Measurement ||Definition ||Average Adult Values (mL) |
|Tidal volume (Vt) ||Each normal breath ||500 |
|Inspiratory reserve volume (IRV) ||Maximal additional volume that can be inspired above Vt ||3000 |
|Expiratory reserve volume (ERV) ||Maximal volume that can be expired below Vt ||1100 |
|Residual volume (RV) ||Volume remaining after maximal exhalation ||1200 |
|Total lung capacity (TLC) ||RV + ERV + Vt + IRV ||5800 |
|Functional residual capacity (FRC) ||RV + ERV ||2300 |
Tidal volume—The amount of air that is mobilized with each unforced breath (300-500 mL). To find out how much air arrives to the alveoli (and therefore participates in the gas exchange), one must calculate the alveolar volume, subtracting the anatomical dead space from the tidal volume. The anatomical dead space is given by the initial portion of the airways (from the mouth to the terminal bronchioles). Anatomical dead space does not participate in the exchange of O2 and CO2 between air and blood, but has only one function to bring the air to the alveoli. The dead space volume is on average 150 cc, and it can be calculated approximately by multiplying the weight in kilograms by 2.
Inspiratory reserve volume—The maximum amount of air that, after normal inspiration, may still be forcibly introduced in the lungs.
Expiratory reserve volume—The maximum amount of air that, after a normal expiration, can still be expelled with a forced exhalation.
Residual volume—The air that remains in the lungs after a forced exhalation. This volume cannot be measured directly and is calculated using various methods: plethysmography, helium mixing, nitrogen washout. Increased residual volume is a sign of lung hyperinflation due to bronchoconstriction or pulmonary emphysema. It is also very important in forensic medicine, because the absence of this residual air is an indication of death by suffocation.
The lung capacities are sums of volumes:
Log In to View More
If you don't have a subscription, please view our individual subscription options below to find out how you can gain access to this content.
Want remote access to your institution's subscription?
Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.
If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.
AccessAnesthesiology Full Site: One-Year Subscription
Connect to the full suite of AccessAnesthesiology content and resources including procedural videos, interactive self-assessment, real-life cases, 20+ textbooks, and more
Pay Per View: Timed Access to all of AccessAnesthesiology
24 Hour Subscription $34.95
48 Hour Subscription $54.95
Pop-up div Successfully Displayed
This div only appears when the trigger link is hovered over.
Otherwise it is hidden from view.