An adult takes fourteen to twenty breaths every minute, and children, depending on age, are able to make up to sixty respiratory movements in the same period of time. This is an unconditioned reflex that helps the body survive. Its implementation goes beyond our control and understanding. External and internal breathing among themselves have a so-called message. It works on the principle of feedback. If the cells lack oxygen, then the body speeds up respiration, and vice versa.
Definition
Breathing is a continuous reflex act. It ensures the constancy of the gas composition of the blood. It consists of three stages or links: external respiration, gas transport and tissue saturation. Failure can occur at any stage. It can lead to hypoxia and even death. External respiration is the first stage in which gas exchange occurs between a person and the environment. First, atmospheric air enters the alveoli. And in the next step, it diffuses into the blood for transportation to the tissues.
The mechanism by which oxygen enters the blood is based on the difference in the partial pressure of the gases. Exchange occurs according to the concentration gradient. That is, blood with a high carbon dioxide content easily accepts enough oxygen, and vice versa. At the same time, the essence of tissue respiration is as follows: oxygen from the blood enters the cytoplasm of the cell, and then passes through a chain of chemical reactions called the respiratory chain. Ultimately, carbon dioxide and other metabolic products enter the peripheral bed.
Air composition
External respiration is highly dependent on the composition of atmospheric air. The less oxygen it contains, the less often breaths become. Normally, the composition of the air is approximately the following:
- nitrogen - 79.03%;
- oxygen - 20%;
- carbon dioxide - 0.03%;
- all other gases - 0.04%.
As you exhale, the ratio of the parts changes somewhat. Carbon dioxide rises to 4%, and oxygen decreases just as much.
The structure of the respiratory apparatus
The external respiration system is a series of tubes interconnected. Before getting into the alveoli, the air goes a long way to keep warm and clean. It all starts with the nasal passages. They are the first barrier to dust and dirt. The hairs located on the nasal mucosa hold large particles, and closely located vessels warm the air.
Then comes the nasopharynx and oropharynx, followed by the larynx, trachea, and main bronchi. The latter are divided into right and left lobes. They branch, forming a bronchial tree. The smallest bronchioles at the end have an elastic sac - the alveolus. Despite the fact that the mucous membrane lines all the airways, gas exchange occurs only at the very end. Unused space is called dead. Normally, its size reaches up to one hundred and fifty milliliters.
Breathing cycle
In a healthy person, breathing takes place in three stages: inhalation, exhalation and pause. In time, the whole process takes from two and a half to ten seconds or more. These are very individual parameters. External respiration largely depends on the conditions in which the body is and on its state of health. So, there are concepts such as rhythm and respiratory rate. They are determined by the number of movements of the chest per minute, their dimensionality. The depth of breathing can be determined by measuring the volume of exhaled air or the girth of the chest during inhalation and exhalation. The process is quite simple.
Inhalation is performed during contraction of the diaphragm and intercostal muscles. The negative pressure that is created at this moment, as if “sucks” atmospheric air into the lungs. In this case, the chest expands. Exhalation is the opposite effect: the muscles relax, the walls of the alveoli tend to get rid of overstretching and return to their original state.
Pulmonary ventilation
The study of the function of external respiration has helped scientists better understand the mechanism of development of a significant number of diseases. They even identified a separate branch of medicine - pulmonology. There are several criteria by which the work of the respiratory system is analyzed. Indicators of external respiration are not a hard value. They may vary depending on the constitution of the person, age and state of health:
- Tidal volume (TO). This is the amount of air that a person inhales and exhales at rest. The norm is from three hundred to seven hundred milliliters.
- Reserve inspiratory volume (DOM). This is air that can still be added to the lungs. For example, if after a calm breath, ask a person to take a deep breath.
- Reserve volume of expiration (ROVD). This is the volume of air that will leave the lungs if, after a regular exhalation, it is deep. Both indicators are about one and a half liters.
- Residual volume. This is the amount of air that remains in the lungs after a deep exhalation. Its value is from a thousand to one and a half thousand milliliters.
- The four previous indicators together make up the vital capacity of the lungs. In men it is equal to five liters, in women - three and a half.
Pulmonary ventilation is the entire volume of air that passes through the lungs in one minute. In an adult healthy person at rest, this figure fluctuates around six to eight liters. The study of the function of external respiration is necessary not only for people with pathologies, but also for athletes, as well as children (especially premature newborns). Often such knowledge is needed in intensive care, when the patient is transferred to mechanical ventilation (mechanical ventilation) or removed from it.
Types of Normal Breathing
The function of external respiration largely depends on the type of process. And also from the constitution and gender of a person. By the method of expansion of the chest, two types of breathing can be distinguished:
- Chest, during which ribs rise. It predominates in women.
- Abdominal when the diaphragm is flattened. This type of breathing is more common in men.
There is also a mixed type when all muscle groups are involved. This indicator is individual. It depends not only on gender, but also on the person’s age, since chest mobility decreases over the years. The profession also influences him: the harder the work, the more the abdominal type prevails.
Pathological types of breathing
External respiration changes dramatically in the presence of respiratory failure syndrome. This is not a separate disease, but only a consequence of the pathology of other organs: heart, lungs, adrenal glands, liver or kidneys. Cider passes in both acute and chronic form. In addition, it is divided into types:
- Obstructive. Dyspnea appears on inspiration.
- Restrictive type. Shortness of breath appears on exhalation.
- Mixed type. Usually it is a terminal stage and includes the first two options.
In addition, there are several types of pathological breathing that are not associated with a specific disease:
- Cheyne - Stokes breath. Starting with the superficial, breathing gradually deepens and on the fifth-seventh breath reaches normal values. Then it becomes rare and shallow again. There is always a pause at the end - a few seconds without a breath. It occurs in newborns, with head injury, intoxication, hydrocephalus.
- Kussmaul's breath. This is a deep, noisy and rare breath. It occurs with hyperventilation, acidosis, diabetic coma.
Pathology of external respiration
Violation of external respiration occurs both during normal functioning of the body, and in critical situations:
- Tachypnea is a condition where the respiratory rate exceeds twenty times per minute. It happens both physiological (after exercise, in a stuffy room), and pathological (with blood diseases, fever, hysteria).
- Bradypnoe - a rare breath. It is usually combined with neurological diseases, increased intracranial pressure, cerebral edema, coma, intoxication.
- Apnea - absence or respiratory arrest. May be associated with respiratory muscle paralysis, poisoning, traumatic brain injury, or cerebral edema. Also, a symptom of respiratory arrest in a dream is isolated.
- Dyspnea - shortness of breath (rhythm, frequency and depth of breath). It occurs with excessive physical exertion, bronchial asthma, chronic obstructive bronchitis, hypertension.
Where is knowledge of the characteristics of external respiration needed?
The study of external respiration must be carried out for diagnostic purposes to assess the functional state of the entire system. In patients at risk, for example, smokers or workers in an unhealthy industry, a tendency towards occupational diseases is thus detected. For surgeons and anesthetists, the state of this function is important in preparing the patient for surgery. A dynamic study of external respiration is carried out to confirm the disability group and assess disability in general. As well as during the follow-up of patients with cardiac or pulmonary chronic diseases.
Types of Research
Spirometry is a way to assess the state of the respiratory system by the volume of normal and forced expiration, as well as expiration in 1 second. Sometimes, for diagnostic purposes, they carry out a test with a bronchodilator. Its essence is that the patient first goes through the study. Then he receives inhalation of a medication that expands the bronchi. And after 15 minutes, the study passes again. The results are compared. It is concluded that the pathology of the respiratory tract is reversible or irreversible.
Bodyplethysmography - is performed to assess the total lung capacity and aerodynamic resistance of the airways. For this, the patient must inhale air. It is in a sealed chamber. In this case, not only the amount of gas is recorded, but also the force with which it is inhaled, as well as the air flow rate.