Give me a little TLC [Total Lung Capacity] ~ I’ll take the other kind too

Take a deep breath.

Let it out.

Feel your chest rise and fall, your ribs expand as you let all that oxygen fill your lungs, and slowly squeeze the toxins out of your body as you exhale. (fun fact, the man who discovered Oxygen in 1774: Joseph Priestly was born today…man what were we breathing before he discover sweet O2?)

Ahhh, there may not be anything more centering than taking a moment to focus on your breathing. Really lets you take some time and give yourself a little TLC –> in the common parlance (tender love and care) and in the physiological way TOTAL LUNG CAPACITY. When considering lung function and health, physical therapists look at several volumes and capacities.

Alright, lets break them down:


Your total lung capacity is just what it sounds like, it is the volume of air in the lungs after a MAXIMAL inhalation:
TLC (total lung capacity) = RV (residual volume) + VC (vital capacity)

Ready for more? Ok, read on…don’t get overwhelmed, remember this all happens without you even thinking about it (and you don’t even have to memorize it, unless you are a DPT student of course)….just take a deep breath:

VD (anatomic dead space)

The volume of air that occupies the non-respiratory conducting airways

ERV (expiratory reserve volume)

Max volume of air that can be exhaled after a normal tidal exhalation.

~ 15% of total lung volume

FEV (Forced expiratory volume)

Max volume of air exhaled in a pecific period of time,

FVC (forced vital capacity)

Volume of air expired during  a forced maximal expiration after forced maximal inspiration.

FRC (functional residual capacity)

VOl of air in lungs after normal exhalation

FRC = ERV + RV → ~ 40%

IC (inspiratory capacity)

The max volume of air inspired after a normal tidal exhalation

IC = TV + IRV → 60%

IRV (inspiratory reserve volume)

Max volume that can be inspired after normal tidal volume inspiration

IRV ~ 50% total lung volume

VE (Minute volume ventilation)

Volume of air expired in one minute

VE = TV x respiratory rate

PEF Peak expiratory flow)

The max flow of air during the begining of a forced expiratory maneuver

RV (residual volume)

Gas remaining in lungs at end of max expiration

RV = ~ 25% total lung volume

TV (Tidal volume)

Total volume inspired and expired with each breath during quiet breathing. TV is approximately 10% of total lung volume

TLC (Total lung capacity)

The volume of air in the lungs after a maximal inspiration; the sum of all lung volumes:

TLC = RV + VC  or TLC = FRC + IC

VC (Vital Capacity)

The volume chage that occurs between maximal inspiration and maximal expiration

VC = TV + IRV + ERV → ~ 75% of total lung volume



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