Lung mechanics Flashcards
What is internal respiration?
The exchange of gases (oxygen and carbon dioxide) between blood, interstitial fluid, and cells.
What is external respiration?
The exchange of gases (oxygen and carbon dioxide) between blood and the external environment.
What 3 processes are involved in external respiration?
Pulmonary ventilation
Gaseous diffusion.
Transport of oxygen and carbon dioxide.
what is pulmonary ventilation
The physical movement of air into and out of the lungs
What drives the movement of air through the airways?
Airflow is driven by the pressure gradient between the mouth and alveoli, expressed as:
Flow = ΔP / R, where ΔP = pressure difference and R = resistance.
What are the two main pressure gradients in breathing?
Pressure gradient driving air: From the mouth to alveoli (mouth - alveolar).
Pressure gradient distending the lung: Transmural pressure (alveolar - intrapleural).
What is transmural pressure?
The pressure difference between the alveolar pressure and the intrapleural pressure that distends the lung.
transmural = alveolar - intrapleural
What is required for the bulk flow of air along the airways?
A pressure gradient must be generated between atmospheric pressure (PB) and airway pressure (Paw).
when does air flow into the lungs?
What happens to airway pressure during inspiration?
During inspiration, Paw decreases, creating a pressure gradient that allows air to flow into the lungs.
What is the equation for airflow through the airways?
Flow (Q) = ΔPressure (P1 - P2) / Resistance (R),
where P1 is atmospheric pressure and P2 is airway pressure.
What creates the flow of air during expiration?
Air flows out when Paw (airway pressure) > PB (atmospheric pressure), generating a pressure gradient.
What is the equation for airflow during expiration?
Flow (Q) = ΔPressure (P1 - P2) / Resistance (R),
where P1 is airway pressure and P2 is atmospheric pressure.
What does Boyle’s Law state?
The pressure of a fixed number of gas molecules at constant temperature is inversely related to the volume of the container. (PV = constant)
What happens to pressure when the volume of a gas is decreased?
When volume decreases, pressure increases due to the gas molecules being compressed into a smaller space.
What happens to pressure when the volume of a gas is increased?
When volume increases, pressure decreases as gas molecules are distributed over a larger space.
What is the mathematical representation of Boyle’s Law?
P1 × V1 = P2 × V2
where P and V are initial and final pressure and volume, respectively.
How is Boyle’s Law applied in respiration?
During inhalation, lung volume increases, leading to a decrease in pressure and air inflow. During exhalation, lung volume decreases, increasing pressure and pushing air out.
How are the lungs mechanically coupled to the chest wall?
by the pleural fluid, which prevents lung collapse by balancing the inward recoil of the lungs with the outward recoil of the chest wall.
What is the value of intrapleural pressure at resting end-expiration?
Intrapleural pressure is negative, approximately -5 cm H₂O at resting end-expiration.
What happens to intrapleural pressure during inspiration?
The expansion of the thoracic cage during inspiration further reduces intrapleural pressure, which allows the lungs to expand.
How does increased lung volume affect airway pressure?
Increased lung volume leads to a decrease in airway pressure, which drives air into the lungs.
What is the relationship between alveolar pressure (Pₐ) and atmospheric pressure (Pᵦ) during inspiration?
During inspiration, alveolar pressure (Pₐ) becomes less than atmospheric pressure (Pᵦ), allowing air to flow into the lungs.
How are respiratory pressures generally expressed?
Respiratory pressures are expressed relative to atmospheric pressure (Pᵦ).
unless stated otherwise