Lung Mechanics and Ventilation - Vocabulary Flashcards

Vocabulary flashcards covering key terms from the lecture notes on lung mechanics and ventilation.

Atmospheric pressure

Pressure exerted by surrounding air; standard sea-level value is 760 mm Hg.

Intrapleural pressure (Ppl)

Subatmospheric pressure in the pleural space that keeps the lungs expanded; normally negative.

Esophageal balloon-tipped catheter

Device used to estimate pleural pressure by measuring pressure in the esophagus.

Alveolar pressure (PA)

Pressure inside the alveoli; negative during inspiration, zero when flow is absent, positive during expiration.

Transpulmonary pressure (PL)

Distending pressure across the lung; PA − Ppl; determines alveolar volume.

Transrespiratory pressure (Prs)

Pressure difference driving gas flow; PA − Pbs (also called transairway pressure).

Transmural chest-wall pressure (Pw)

Pressure across the chest wall; Ppl − Pbs; reflects chest wall recoil.

Pao

Pressure at the airway opening (mouth); equals atmospheric pressure during normal spontaneous breathing.

Pbs

Pressure at body surface; reference pressure (usually 0 cm H2O or 0 mm Hg).

Pleural pressure measurement

Pressure measured in the pleural space, often inferred from esophageal pressure.

Surface tension

Force to overcome cohesive forces at the air–liquid interface in alveoli; tends to collapse alveoli.

Pulmonary surfactant

Substance that reduces alveolar surface tension; mainly phospholipids and proteins; produced by Type II cells.

DPPC (dipalmitoyl phosphatidylcholine)

Major surface-tension–lowering phospholipid in surfactant.

Lecithin–Sphingomyelin (L/S) ratio

Amniotic-fluid marker of fetal lung maturity; >2:1 suggests maturity; used clinically to assess risk of RDS.

Type II alveolar cells

Cells that synthesize and secrete surfactant and participate in alveolar repair.

Functional residual capacity (FRC)

Lung volume at end of a normal expiration; balance point between lung and chest-wall recoil.

Residual volume (RV)

Volume of air remaining in the lungs after maximal expiration.

Total lung capacity (TLC)

Maximum amount of air the lungs can contain after a maximal inspiration.

Vital capacity (VC)

Maximum amount of air exhaled after a maximal inhalation.

Inspiratory capacity (IC)

Maximum amount of air that can be inspired from the end of a normal expiration.

Tidal volume (VT)

Volume of air moved in and out of the lungs during a normal breath.

Inspiratory Reserve Volume (IRV)

Additional air that can be inspired after a normal inspiration.

Expiratory Reserve Volume (ERV)

Additional air that can be exhaled after a normal expiration.

Compliance

Ease of lung and chest-wall distension; change in volume per unit change in pressure.

Elastance

Inverse of compliance; pressure change required per unit volume change.

Elastic recoil

Tendency of the lungs to return to their original size after stretch.

Laplace’s law

P = 2T/r; pressure required to keep an alveolus open given surface tension (T) and radius (r).

Surfactant function

Reduces surface tension, stabilizes alveoli; DPPC is a key component.

MIP / MEP

Maximum inspiratory pressure (PImax) and maximum expiratory pressure (PEmax); index of ventilatory muscle strength.

PEEP

Positive end-expiratory pressure; maintains alveolar recruitment at end of expiration.

Peak airway pressure (Ppeak)

Maximum pressure during inspiration; reflects both elastic and resistive loads.

Plateau pressure (Pplat)

Alveolar pressure during no-flow part of inspiration; reflects elastic recoil.

Airway resistance (Raw)

Resistance to gas flow in the airways; computed as (Ppeak − Pplat)/flow.

Time constant (TC)

Product of compliance and resistance (CLT × Raw); governs filling/emptying rate.

Equal pressure point (EPP)

Location where intraluminal pressure equals pleural pressure; relevant to expiratory flow limitation.

Mucociliary clearance

Mucus transport by cilia; aided by expiratory flow patterns.

Hysteresis

Difference between inflation and deflation pressure–volume curves due to recruitment/derecruitment.

Static vs dynamic PV curves

Static PV: no flow; Dynamic PV: with flow; used to assess compliance and elastance under breathing.

DLCO

Diffusing capacity of the lung for carbon monoxide; measures gas diffusion across the alveolar–capillary membrane.