Biomechanics of breathing. Lungs ventilation

Respiration External respiration (Ventilation

and the exchange of gases (oxygen and carbon dioxide) between the air and blood )

Internal respiration (oxygen utilization by the tissues)

Airway zones Conductive (Leading ) zone Transient (transit ) zone Respiratory zone

Of the total volume of the lungs conductive zone is about 150 ml,

transient - about 1500 ml.

Functions of the respiratory pathways

1. Warming.2. Moisturizing.3. Clearing the air

Inhaled air: t 18-22 C, 45-55% BBIn the bronchi: t 37 ° C, 100% BB

Respiratory muscles

Main muscles for inspiration: diaphragm and external intercostal, intercartilaginous muscles

Muscles for expiration: internal intercostal, pectoral, abdominal muscles

Calm inspiration is an active process. The contraction of the inspiratory muscles and diaphragm increases intrathoracic volume. It stretches the thorax and lungs.

Calm expiration is a passive process. The thorax and lungs recoil when the respiratory muscles relax.

Inspiration

the dome of the diaphragm flattens, ribs elevate

In the rest, 4/5 of inhalational work is done by diaphragm.

Pressure in the alveoli reduces below atmospheric, the air moves under pressure gradient into the lungs

Exhalation

Normally is a passiveprocess. After relaxation of muscles, due to the elastic tension of thorasic tissues air is removed

(Becoming active during bronchial obstruction)

Inspiration Exspiration

Effect of Rib and Sternum Movement on Thoracic Volume

Pressure in the lungs and intrapleural pressure

Intrapleural pressure is always lower than the alveolar one:First: chest is a sealed container.Second, the lungs are characterized by elastic tension, which is due to these factors:

1. presence of ellastic fibers, which make 1 / 3 of elastic tention;2. surface tension of the liquid layer on the inner surface of alveoli, which makes 2 / 3 of the elastic tension of the lungs.

Thirdly, “negative” pressure in the pleural cavity is maintained by the large absorbtion capacity of pleural leaves.

Physiological dead space

Breathing act (respiratory movements):

inspiration expiration, their value on average equals to 1:1,2

in adults.  The frequency of respiratory movements in an adult - 16-20 respiratory movements for 1 minute.

Evaluation of functional state of the respiratory system

1. Tidal volume (breathing air) - a volume of air that is inhaled or exhaled at rest. Normally it is - 0,3-0,8 l (mean 0.5 ml).

2. Inspiratory reserve volume (additional air) - is the maximum volume of air you can inhale above after the calm inspiration. Normally it is 1.5-2.0 l.

3. Expiratory reserve volume (air backing) - is the maximum volume of air you can exhale above after the calm expiration. Normally it is 1,0-1,5 liters.

4. Residual volume (residual air) - the amount of air that remains in the lungs after maximum exhalation. Normally it is 1,0-1,5 liters.

Spirometer, Lung Volumes, and Lung Capacities

Lung capacity 1. The total maximum lung capacity - the maximum volume of

air that fits in the lungs or the sum of all lung volumes. Normally is 4,5-6,5 liters.

2.Vital lung capacity - the largest amount of air you can exhale after maximum inhalation or the amount of the first three volumes. Normally it is: women - 3,0-3,5 l; in men - 3,5-5,0 liters.

3. Inspiratory capacity - the maximum amount of air you can breathe after calm exhalation, or the amount of the first two volumes. Normally it - 1,8-2,8 liters.

4. Functional residual capacity - the amount of air contained in the lungs after calm exhalation or the amount of the last two volumes. Normally - 2.5-3.5 liters.

Appropriate Vital Capacity value

Men [27.63 - (0.112 x · age in years)] · height in cmfor women [21.78 - (0.101 · age in years)] · height in cmNormally the actual VC can deviate up to 15%

Alveolar ventilation

Alveolar ventilation is a volume of air that enters the alveoli of the lungs per unit of time.

Alveolar ventilation =(TV - Dead Space) · BR

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