mechanics of normal restful breathing

Flashcards covering the fundamental mechanics and vocabulary of respiratory physiology, including pressure gradients, volumes, and clinical maneuvers.

Boyle’s Law

A principle stating that the pressure of a gas is inversely proportional to the volume of its container ($P \times V = \text{constant}$).

Boyle's Law - inspiration

Boyle's Law - expiration

atmospheric pressure (Patm)

Also called barometric pressure; the pressure exerted by the air surrounding the body, which by convention is considered 0 cm H2O

intra-alveolar pressure (Palv)

Also called Intrapulmonary pressure; the pressure within the alveoli of the lungs which falls and rises during breathing but always equalizes with Patm It is the sum of PIP and Pel

intrapleural pressure (PIP)

The pressure within the pleural cavity, which is negative (approximatel -5 cm H2O) at FRC due to opposing lung and chest wall recoil.

lung elastic recoil

The inward collapsing force created by the elastic properties of the lung connective tissue and alveoli.

chest wall elastic recoil

The outward springing force of the rib-cage and muscles of respiration.

transmural pressure

transpulmonary pressure (PTP)

The transmural pressure across the lung, calculated as alveolar pressure minus intrapleural pressure ($P_{TP} = P_{alv} - P_{IP}$).

chest wall pressure (PCW)

The transmural pressure across the chest wall, calculated as intrapleural pressure minus atmospheric pressure ($P_{CW} = P_{IP} - P_{atm}$).

positive transmural pressure

distending pressures associated with forces that tend to expand or increase the volume of a structure.

negative transmural pressure

collapsing pressures associated with forces that tend to decrease the size or volume of a structure.

transmural pressures - pneumothorax

A condition where air enters the thorax from the atmosphere, causing PIP to become equal to Patm, resulting in lung collapse (atelectasis) and chest wall expansion

breathing cycle

breathing cycle - rest

breathing cycle - during inspiration

breathing cycle - end of inspiration

breathing cycle - during expiration

breathing cycle - end of expiration

Valsalva Maneuver

A forced expiratory effort with the glottis closed, resulting in increased positive compressive pressure in the thoracic cavity and highly positive alveolar (airway) pressure.

esophageal pressure

A measure used as an index of intrapleural pressure, typically obtained via a balloon catheter placed in the lower esophagus.