Respiration During Exercise (1)

Respiration During Respiration During Exercise (1) Exercise (1)

Pulmonary Ventilation (V)

The amount of air moved in or out of the lungs per minute

It is the product of tidal volume (VT) and breathing frequency

V= VT x f


1. Dead-space ventilation (VD)

• Unused ventilation (like the trachea & bronchi)

• Does not participate in gas exchange


• Anatomical dead space conducting zone

BUT

• Physiological dead space caused by disease


2. Alveolar ventilation (VA)

• Volume of inspired gas that reaches the respiratory zone

V = VA + VD

Total minute ventilation can be subdivided into dead space

ventilation & alveolar ventilation

V +

Pulmonary Volumes & Capacities

•They are measured by spirometry

• Vital Capacity (VC):

– Maximum amount of air that can be expired following a maximum inspiration

InspiratorInspiratory Reserve y Reserve Volume Volume (IRV)(IRV)

Tidal Volume Tidal Volume (TV)(TV)

Residual Residual Volume (RV)Volume (RV)

Expiratory Expiratory Reserve Reserve

Volume (ERV)Volume (ERV)



• Residual Volume (RV):

– Air remaining in the lungs after a maximum expiration






• Total Lung Capacity (TLC):

– The sum of VC and RV







Partial Pressure of Gases (Dalton’s Law)

The total pressure of a gas mixture is equal to the sum of the

pressure that each gas would exert independently

Partial Pressure of Gases (Dalton’s Law)

• The partial pressure of oxygen (PO2)– Air is 20.93% oxygen– This is expressed as a fraction

20.93/100 = 0.2093– The total pressure of air = 760 mmHg– So PO2 = 0.2093 x 760 = 159 mmHg

Diffusion of GasesDiffusion of GasesFick's Law of Diffusion Fick's Law of Diffusion

The rate of gas transfer (V The rate of gas transfer (V gas) is proportional to gas) is proportional to the tissue area (A), the tissue area (A),

the diffusion coefficient of the diffusion coefficient of the gas (D), the gas (D),

and the difference in the and the difference in the partial pressure of the partial pressure of the gas on the two sides of gas on the two sides of the tissue (P1-P2), the tissue (P1-P2),

And inversely proportional And inversely proportional to the thickness (T)to the thickness (T)

P1P1 P2P2

Diffusion of GasesDiffusion of GasesFick's Law of Diffusion Fick's Law of Diffusion

V gas = A/T x D x (PV gas = A/T x D x (P11 – – PP22))

Respiration During Exercise (1)

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