Rhythmic expansion and contraction of the thorax caused by contraction and relaxation of respiratory muscles

inspiratory muscles

expiratory muscles

accessory inspiratory muscles

calm breathing

Breathe hard

abdominal breathing

chest breathing

Thoracic and abdominal mixed breathing

Refers to the pressure of gas in the alveoli, which changes periodically during breathing

Early inhalation

End of inspiration

Early exhalation

End of expiration

Variety

During calm breathing, the pressure is always lower than atmospheric pressure (negative pressure)

When breathing hard, the pressure will increase significantly. When exhaling hard with the glottis closed, the pressure can be higher than the atmospheric pressure.

Prerequisites

main reason

Expand the lungs so that they can expand and contract with the expansion and contraction of the thorax

Acts on the vena cava and thoracic duct in the chest to expand them, which is beneficial to the return of venous blood and lymph fluid

Metrics

source

There is always resistance to inhalation

source

When the thorax is in its natural position (quiet end of inspiration), the lung capacity is approximately 67% of the total lung capacity.

When the thorax is smaller than its natural position (at the end of calm expiration and deep exhalation), the elastic resistance is outward, which is the driving force for inhalation and the resistance for exhalation.

When the chest is larger than the natural one (deep inhalation), the elastic resistance is inward, which is the resistance of inhalation and the power of exhalation.

The elastic resistance of the thorax can be either the resistance of inhalation or exhalation or the power, which is determined by the position of the thorax.

Influencing factors

deep inspiratory volume

functional residual capacity

vital capacity

total lung capacity

The maximum amount of air that can be inhaled or exhaled per minute while trying to breathe deeply and quickly

It reflects the ventilation volume that can be achieved by fully exerting all ventilation capabilities per unit time. It is one of the physiological indicators that estimates the maximum amount of exercise the body can perform.

Factors such as reduced lung or thoracic compliance, weakened respiratory muscle contraction, or increased airway resistance can reduce maximum voluntary ventilation.