Lung Mechanics and Respiratory Physiology

What physiological actions happen in inhalation

Diaphragm moves down, ribs elevate, lung volume increases

What physiological actions happen in exhalation

Diaphragm moves up, ribs depress, lung volume decreases

What is pleural pressure

Pressure in the pleura → About -5 to -7.5 cm H2O

What is transpulmonary pressure

Difference between alveolar and pleural pressure

What is the mechanism of inhalation

Intrathoracic volume increase → Pleural pressure is more negative → Transpulmonary pressure increase → Alveolar volume increase, alveolar pressure decrease → Pressure difference increase → Air flow IN 

What is the mechanism of exhalation

Intrathoracic volume decrease → Pleural pressure is less negative → Transpulmonary pressure decrease → Alveolar volume decrease, alveolar pressure decrease → Pressure difference increase → Air flow OUT 

What is mechanical ventilation

Applying positive pressure to cause gas to flow into alveoli until pressure is equal

How does mechanical ventilation cause expiration

Upper airway pressure is decreased → Pressure gradient between airway and alveoli is reversed → Gas flows OUT

What increases the chances of occlusion in alveoli

High surface tension (lack of surfactant) and small alveolar radius; found in children

What is compliance

The ability for the lung to stretch during breathing (change in volume per change in pressure)

What is non elastic resistance

Airway resistance to gas flow

What is tidal volume

Quiet breathing; the amount of air that comes in and out of lung normally

What is inspiratory reserve volume

Deep inhalation; the amount of air that can be forcefully inhaled

What is expiratory reserve volume

Deep exhalation; the amount of air that can be forcefully exhaled

What is functional residual capacity

The remaining amount of air after inhalation/expiration used when there is no regular airflow

Sympathetic control of bronchial diameter

Beta2 receptors DILATE → Increase airflow

Parasympathetic control of bronchial diameter

ACh CONSTRICT → Decrease airflow

What medication can constrict bronchus diameter

Histamine, ACh

What medication can dilate bronchus diameter

Adrenergic beta agonist

What is minute ventilation

The total amount of air moved in and out of the system per minute

What is alveolar ventilation

The amount of air per minute that enters the areas where gas exchange occurs

What is Dalton’s law

The total pressure of gas is equal to the summation of pressure for all gases

What is Fick’s law

Diffusion of gas → (PA - Pa)AD/Thickness of wall

What is Px

Partial pressure

What is Fx

Fractional volume/pressure

What is Sx

Saturation

What is Cx

Concentration

What is a

Arterial blood

What is v

Venous blood

What is c

Capillary blood

What is A

Alveolar gas

What is I

Inspired gas

What is E

Expired gas

What would PECO2 refer to

Partial pressure of CO2 in EXPIRED air

What does SaO2 mean

Saturation of O2 in arterial blood