Chapter 11 – Ventilation Vocabulary

Ventilation

The cyclic process of moving gas (usually air) in and out of the lungs to remove CO₂ and replenish O₂.

Respiration

Physiologic process of oxygen utilization and carbon-dioxide production at the cellular level; distinct from ventilation.

Tidal Volume (VT)

The volume of gas moved into or out of the lungs during a single, normal breath.

Transrespiratory Pressure (PTR)

The pressure gradient between the airway opening (PAO) and body surface (PBS); drives overall gas flow through the respiratory system.

Transairway Pressure (PTAW)

The pressure difference between the airway opening (PAO) and the alveoli (PA); represents the driving force for intrapulmonary airflow.

Transalveolar Pressure (PTA)

The pressure gradient between alveolar pressure (PA) and pleural pressure (Ppl); reflects the distending pressure across alveolar walls.

Transchestwall Pressure (PTCW)

The pressure difference between pleural pressure (Ppl) and body-surface pressure (PBS); represents chest-wall distending pressure.

Transpulmonary Pressure (PTP)

The pressure difference between the airway opening (PAO) and pleural space (Ppl); keeps alveoli open and determines lung inflation.

Transthoracic Pressure (PTT)

The pressure gradient between alveolar pressure (PA) and body-surface pressure (PBS); causes gas to flow into and out of the alveoli during breathing.

Pleural Pressure (Ppl)

The sub-atmospheric pressure within the pleural space; typically about –5 cm H₂O at end-expiration in resting, healthy lungs.

Functional Residual Capacity (FRC)

The resting lung volume at the end of quiet exhalation; maintained by a positive end-expiratory transpulmonary pressure.

Hysteresis

The difference between inflation and deflation pressure-volume curves of the lung, partly due to surface-tension changes and recruitment of collapsed alveoli.

Surface Tension

Cohesive force at the air-liquid interface in alveoli that opposes lung inflation and contributes to elastic recoil.

Pulmonary Surfact