Investigating Ventilation

Understanding Ventilation

The process of moving air into and out of the lungs is known as ventilation. It allows gas exchange to occur, providing oxygen to tissues and removing waste carbon dioxide.
Inspiration (inhalation) and expiration (exhalation) are the two phases of ventilation. The former is an active process, whilst the latter can be passive or active, depending on the circumstances.
Proper ventilation requires functioning lungs, airways, respiratory muscles, and a connected nervous system.

During inspiration, the diaphragm contracts and flattens, increasing the space in the thoracic cavity, hence allowing air to flow into the lungs.
Meanwhile, the external intercostal muscles contract, pulling the ribcage upwards and outwards, further expanding the chest cavity.
Expiration is mostly a passive process under normal conditions and involves the relaxation of the diaphragm and the external intercostal muscles. This results in decrease in volume and increase in pressure in the chest cavity, hence expelling air out of the lungs.
During strenuous activities like vigorous exercise, expiration becomes an active process where internal intercostal muscles contract, pulling the rib cage downwards and further decreasing thoracic volume.

Demand for oxygen: During exercise, cells need more oxygen to produce ATP, hence increasing the rate and depth of ventilation.
Levels of carbon dioxide: High levels of CO2 in the blood trigger an increase in ventilation to expel the excess gas.
pH in the blood: If CO2 levels rise, the blood becomes more acidic (lower pH), which also signals the need for increased ventilation.
The nervous system plays a significant role in controlling ventilation, particularly the medulla oblongata.

Measurement of ventilation can be conducted using a spirometer, which measures the volume of air inspired and expired.
Tidal volume is the volume of air moved into or out of the lungs during a normal breath.
Inspiratory and expiratory reserve volumes represent the additional volume of air that can be inspired or expired from the lungs above the normal tidal volume.
Vital capacity is the total amount of air that can be voluntarily moved out of the lungs after a maximal inspiration.
Respiratory rate (breaths per minute) and minute ventilation (volume of air breathed in one minute) also provide useful information about the efficiency of ventilation.
Comparing these values before, during, and after exercise can provide insights into how the body adjusts ventilation in response to metabolic needs.