MEDICAL BIOLOGY, ANATOMY, HUMAN PHYSIOLOGY AND PATHOLOGY - Y.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

CHAPTER 6. RESPIRATORY PROCESS AND ITS PATHOLOGY

RESPIRATORY SYSTEM DISEASES

DISORDERS OF EXTERNAL RESPIRATION

Under normal conditions, The activity of the respiratory center ensures a specific rate, depth, and rhythm of breathing. At rest, a person breathes without any visible effort, largely without noticing the process. This state is called respiratory comfort, and breathing itself is referred to as eupnea.

Under METABOLISM/18.html">The Influence of certain factors, the rhythm, depth, and rate of breathing may change, resulting in dyspnea. These changes can be manifestations of compensatory reactions aimed at maintaining the constancy of the Blood gas composition, or they may arise as a consequence of impaired respiratory regulation, leading to alveolar ventilation disorders and respiratory failure.

Bradypnea is an abnormally slow respiratory rate. A reflex decrease in breathing rate is observed during increases in blood pressure and in hyperoxia. Causes of bradypnea may include increased resistance to airflow in the Upper Respiratory Tract—known as stenotic breathing—or the direct action of pathogenic factors that depress the excitability of the respiratory center, such as narcotics and barbiturates.

Tachypnea is rapid, shallow breathing. Tachypnea may occur in fever, functional Changes in the Central Nervous system (hysteria), or pulmonary lesions (Atelectasis, Pneumonia, congestion). In addition, localized pain (in the chest wall, abdominal wall, or Pleura) can lead to tachypnea. Pain limits the depth of breathing and increases its frequency (protective breathing).

Hyperpnea is deep and rapid breathing. Under physiological conditions, hyperpnea occurs as a respiratory response aimed at improving blood oxygenation and eliminating excess carbon dioxide, for example, during muscular exertion.

The highest degree of excitation of the respiratory center manifests as Kussmaul breathing, which is most commonly observed in patients in a state of diabetic coma. It is characterized by noisy, accelerated breathing in which a deep inspiration is followed by a forced expiration involving the active participation of expiratory Muscles.

Apnea literally translates as the absence of breathing, but the term is commonly used to denote a temporary cessation of Respiration. Apnea can be caused by alterations in the body's gas exchange, the severity of which depends on the frequency of occurrence and duration of the breathing pause. Apnea may appear during anesthesia as a consequence of a reduced partial pressure of $CO_2$ in arterial blood and ceases immediately upon the normalization of $CO_2$ content.

Periodic breathing refers to a disorder of respiratory rhythm characterized by the alternation of breathing periods with periods of apnea. There are two types of periodic breathing: Cheyne-Stokes respiration and Biot's respiration.

Cheyne-Stokes respiration is characterized by a gradual increase in respiratory amplitude leading to marked hyperpnea, followed by a decrease down to apnea, after which a new cycle of respiratory movements begins, ending in apnea once again.

Biot's respiration differs from Cheyne-Stokes respiration in that respiratory movements of constant amplitude cease just as abruptly as they begin.

Apneustic breathing is characterized by a prolonged, spasmodic inspiratory effort that is only occasionally interrupted by expiration.

Gasping respiration (from the English "gasp") consists of isolated "sighs" that decrease in frequency and strength, observed during agony. Such breathing is also referred to as terminal or agonal breathing. Typically, these "sighs" occur after a temporary cessation of respiration (the pre-terminal pause).

Dyspnea, or shortness of breath. In respiratory failure and certain other pathological processes, a person may experience a sensation of air hunger and a consequent urge to increase ventilation. This phenomenon is called dyspnea. Experiencing a lack of air, a person not only involuntarily but also consciously increases the activity of respiratory movements in an attempt to alleviate this sensation. The presence of this subjective feeling is the most essential feature distinguishing dyspnea from Other types of respiratory disorders; therefore, unconscious individuals do not experience dyspnea.

In a healthy person, dyspnea may occur during heavy muscular work if it demands extreme effort at the limit of physical capacity.

Under pathological conditions, dyspnea can be caused by:

1. Inadequate oxygenation of blood in the Lungs (decreased partial pressure of oxygen in the air, impaired pulmonary ventilation, and Pulmonary Circulation disorders).

2. Impaired gas transport by the blood (anemia, circulatory failure).

3. Obstruction of chest and diaphragmatic movements.

4. Functional and organic lesions of the central nervous system (strong emotional influences, hysteria, encephalitis, cerebrovascular disorders, etc.).

Breathing during dyspnea is typically rapid and deep. Both inspiration and expiration are intensified, with expiration acquiring an active character carried out with the participation of expiratory muscles. However, in some cases, either inspiration or expiration may predominate, leading to inspiratory (accentuated inspiration) or expiratory (accentuated expiration) dyspnea. Inspiratory dyspnea is observed, for example, in The First stage of asphyxia, during general excitation of the central nervous system, during physical exertion in patients with circulatory failure, and in pneumothorax. Expiratory dyspnea is less common, occurring mainly in patients with Bronchial Asthma or emphysema, when resistance to airflow in the Lower Respiratory Tract increases during expiration.

Obstruction of airflow through the upper respiratory tract results in stenotic breathing.