Depth- amplitude of each respiratory movement
The depth of ventilation refers to the amount of air that is inhaled and exhaled. The amount of air inhaled and exhaled in one cycle is called the tidal volume. The more the chest cavity expands, the greater the depth of the ventilation. Full expansion of the chest wall with full relaxation on exhalation is a good indicator of adequate depth of breathing and adequate tidal volume. Many books will try and apply numbers in milliliters per breath to calculate tidal volume. This is not possible to measure in the field, so it is important to assess the expansion of the chest to help determine tidal volume.
Respiratory depth is assessed by observing the degree of movement in the chest wall.
Depth is generally described as normal, deep, or shallow.
(1) Normal. Normal depth of breathing is hard to determine. The chest will not expand to its full capacity with each breath. If a patient is not showing signs of distress, is alert, and has a normal skin color, then you can gauge that the breathing depth is normal and adequate for his condition. Airflow of about 500 ml each breath is normal in an adult.
(2) Shallow. If a patient's chest and abdomen rise and fall only slightly, the patient's breathing is shallow. A patient with shallow breathing will probably breathe at a rapid rate. If a patient has a pattern of rapid, shallow breathing, he is said to be "short of breath." Rapid and shallow breathing will not get a high enough tidal volume to allow the air to reach the lungs for good oxygenation. A pattern of slow, shallow breathing is called "hypoventilation."
(3) Deep. A patient's breathing is deep when the chest cavity expands to almost its full capacity. A person who is gasping for air expands his chest to its full capacity. A breathing pattern of rapid, deep breathing is called "hyperventilation."