Module 1 Lecture 6

The atmospheric pressure at sea level is 760 mmHg

Equilibrated - no net movement of air, the preinspiratory size of lungs (760)

Size of the thorax on the contraction of inspiratory muscles (expands), the size of the lungs as they are stretched to fill the expanded thorax

Size of thorax - smaller, relaxation of the inspiratory muscle, size of the lungs as they recoil? bigger?

airflow is the volume of air flowing through the lungs at a given point

Airflow is directionally proportional to the pressure gradient between external atmospheric and alveoli and inversely proportional to resistance airway passages

F ∝ pressure gradient/resistance

During normal quiet breathing, pressure gradient has the biggest influence on air flow

Liquid molecules are strongly attached to each other, it creates tension called surface tension

It is a detergent-like mixture of lipids and proteins decreases in water cohesiveness

surfactant reduces attraction between water molecules, it reduces surface tension of alveolar fluid and reduces tendency to recoli/alveolar collapse

Premature babies are at risk because they lack sufficient surfactant and alvoli which may collapse between breathes

Change in lung volume occurs with a change in transpulmonary pressure, the greater the lung compliance, the greater the expansion at any given transpulmonary pressure.

Lung compliance is determined largely by two factors. Distensibility of lung tissue ( increase in lung compliance) alveolar surface tension (decrease in lung compliance)

Lung distensibility is generally high and surfactant keeps alveolar surface tension low, healthy lungs have a high compliance for efficient ventilation - thoracic respiratory compliance is also affected by thoracic wall compliance

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It is the amount of air that moves in and out during normal quiet breathing

it is the amount of air that can be breathed in forcibly beyond TV

is the amount of air that can be breathed out forcibly beyond TV

Amount of air remaining after forced expiration helps to keep alveoli open

Inspiratory capacity is the total amount of air that can be inspired after normal tidal volume expiration -> TV and IRV

The functional residual capacity is the amount of air remaining in lungs after a normal tidal volume expiration –> RV and ERV

It is the amount of exchangeable air –> TV, IRV and ERV

Total lung capacity is the sum of all lung volumes