Ventilation – Comprehensive Study Notes

25 vocabulary flashcards covering key terms and concepts from the lecture notes on ventilation mechanics, pressures, lung compliance, and gas exchange.

Ventilation

The mechanical process of moving gas (usually air) into and out of the lungs.

Respiration (cellular)

Physiological processes in which cells use oxygen and produce carbon dioxide; distinct from ventilation.

Tidal Volume (VT)

The volume of gas moved into or out of the lungs during a single breath, measured during either inspiration or expiration.

Pulmonary Ventilation

Mass movement of air in and out of the lungs produced by pressure changes generated primarily by diaphragm contraction and relaxation.

Barometric Pressure (PB)

Force exerted by the atmospheric air surrounding the Earth; at sea level ≈ 760 mm Hg.

Pressure Gradient

Difference in pressure between two points that drives gas or liquid to flow from high to low pressure.

Intra-alveolar Pressure (Palv)

Pressure inside the alveoli; becomes lower than PB during inspiration and higher during expiration to create airflow.

Transairway / Transrespiratory Pressure (Prs)

Difference between barometric pressure at the mouth (PB) and alveolar pressure (Palv); Prs = PB – Palv; the driving pressure expanding lungs and chest wall together.

Pleural Pressure (Ppl)

Pressure in the pleural space, normally subatmospheric (negative) and always less than Palv in healthy lungs.

Compliance (CL)

Measure of lung distensibility; change in volume (ΔV) per change in pressure (ΔP), expressed in L/cm H₂O.

Elastance

Tendency of matter to return to its original shape once deforming force is removed; the inverse of compliance (Elastance = ΔP / ΔV).

Driving Pressure

Pressure difference between two points in a tube; determines flow magnitude (e.g., 20 mm Hg − 5 mm Hg = 15 mm Hg).

Poiseuille’s Law (radius effect)

Principle stating that if airway radius is halved, the driving pressure needed for the same flow increases sixteen-fold.

Partial Pressure

Pressure exerted by an individual gas within a mixture; the sum of all partial pressures equals total atmospheric pressure.

Room Air Composition

Approximate constituents of atmospheric air: N₂ 78.6 %, O₂ 20.9 %, H₂O vapor 0.5 %, CO₂ 0.03 %.

Gas Exchange (A-C membrane)

Transfer of O₂ and CO₂ between alveolar air and pulmonary capillary blood across the alveolar-capillary membrane.

Laminar Flow

Smooth, orderly gas movement found mainly in small bronchioles and distal airways.

Turbulent Flow

Chaotic, rapid gas movement predominantly present in the upper airways, trachea, and major bronchi.

High Compliance Region

Area of the lung that fills easily during inspiration because of low elastic resistance.

Low Compliance Region

Area of the lung that requires more pressure to fill and empties slowly due to higher elastic resistance.

Work of Breathing

Energy expended by respiratory muscles to overcome lung/thorax compliance and airway resistance during ventilation.

Transpulmonary / Transairway Pressure Change

Pressure difference generated to initiate inspiration (Palv < PB) or expiration (Palv > PB).

Negative Pleural Pressure

Subatmospheric pressure created by opposing forces of lung recoil inward and chest wall expansion outward.

Diffusion (gas-liquid)

Movement of gas molecules between alveolar air and capillary blood driven by partial-pressure differences.

Ventilation Cycle

Regular sequence of inspiration followed by expiration constituting one complete breath.