# Breathing Mechanics Notes

### Osmosis High-Yield Notes

This Osmosis High-Yield Note provides an overview of Breathing Mechanics essentials. All Osmosis Notes are clearly laid-out and contain striking images, tables, and diagrams to help visual learners understand complex topics quickly and efficiently. Find more information about Breathing Mechanics:

Lung volumes and capacities

Anatomic and physiologic dead space

Ventilation

Alveolar gas equation

Compliance of lungs and chest wall

Combined pressure-volume curves for the lung and chest wall

Alveolar surface tension and surfactant

Airflow, pressure, and resistance

Breathing cycle

NOTES NOTES BREATHING MECHANICS LUNG VOLUMES & CAPACITIES osms.it/lung-volumes-capacities ▪ Spirometry: spirometer used to measure air volume moving in, out of lungs ▪ Static lung volumes: volumes not involved in airﬂow rate ▪ Capacities: combination of > one lung volume Volume variations ▪ Related to age, sex, body size, posture ▪ Tidal volume (VT) ▫ 500mL ▫ Air volume inspired, expired during quiet breathing ▪ Inspiratory reserve volume ▫ Maximum volume inhaled air above VT = 3L ▪ Expiratory reserve volume ▫ Maximum expired air volume below VT = 1.2L ▪ Residual volume (RV) ▫ Air remaining in lungs after forced expiration = 1.2L (not measured by spirometry) ▪ Functional residual capacity (FRC) ▫ Expiratory reserve volume (ERV) + RV = 2.4L 594 OSMOSIS.ORG ▪ VT + inspiratory reserve volume = 3.5L ▪ Vital capacity (VC) ▫ VT + inspiratory reserve volume (IRV) + ERV = 4.7L ▪ Total lung capacity (TLC) ▫ Combination of all lung capacities = 5.9L MEASURING FRC Helium dilution method ▪ Helium placed in spirometer → inhaled ▪ Helium concentration in lungs equalizes with amount of helium placed in spirometer (helium insoluble in blood) after few breaths ▪ Total helium mass measured in spirometer = FRC Body plethysmograph method ▪ Application of Boyle’s law (P X V = k) ▪ Person sits inside plethysmograph (airtight box) → breathes in/out through mouthpiece → measures air pressure in mouth ▪ Mouthpiece closed after expiring VT; as person attempts to breathe FRC calculated using measurements of alveolar pressure, lung volume, pressure changes within plethysmograph