Respiratory motion is regulated by the respiratory center and cerebral cortex, influenced by afferent impulses from thoracic and pulmonary expansion, as well as stimulation of pulmonary stretch receptors. It is further modulated by chemoreceptors located in the carotid body, aortic body, and central nervous system. The maintenance of normal respiratory function depends on coordinated rhythmic respiratory movements, unobstructed airways, proper cardiopulmonary circulation, and intact alveolar gas exchange. Impairment in any of these components can lead to dysfunctional respiratory function. In a healthy adult, the respiratory rate is typically 16–20 breaths per minute, with a ratio of 1:4 to the heart rate.
Etiology
Respiratory System Diseases
Respiratory tract inflammatory diseases or trauma, such as chronic bronchitis in the elderly, severe lung infections, burns, or extensive chest injuries, can cause swelling of the tracheal and bronchial mucosa and increased secretion production. These factors disrupt alveolar gas exchange. In some cases, weakened coughing function results in retention of lower airway secretions, leading to respiratory distress, hypoxia, and carbon dioxide retention.
Circulatory System Diseases
Disorders such as rheumatic heart disease, cor pulmonale, or acute left heart failure can impair pulmonary microcirculation, leading to pulmonary edema, increased airway secretions, and disruption of gas exchange.
Neurological System Diseases
Conditions such as encephalitis, cerebral edema, cerebrovascular accidents, severe brain trauma, poliomyelitis, Guillain-Barré syndrome, poisoning, and coma can affect the respiratory center, resulting in dysfunctional respiratory function, weakened swallowing, and diminished or absent cough reflexes. Tetanus can cause respiratory muscle spasms, leading to the retention of lower airway secretions or aspiration, ultimately contributing to impaired respiratory function.
Clinical Manifestations
The primary symptom of dysfunctional respiratory function is respiratory distress. Unlike laryngeal respiratory distress, it typically presents without stridor or the "three-retraction" sign. The main manifestations include changes in respiratory rate and depth.
Disorders caused by respiratory or circulatory system conditions usually result in an increased respiratory rate.
Neurological diseases, such as those that elevate intracranial pressure, often slow respiratory rate.
Dysfunction of respiratory muscles, such as in polyneuropathy, leads to shallow breathing.
Gas exchange impairment causes hypoxia and carbon dioxide retention, leading to tachycardia, increased cardiac output, contraction of pulmonary microvasculature, and elevated pulmonary circulation resistance. Chronic conditions may ultimately result in right heart failure. Severe carbon dioxide retention can exacerbate into pulmonary encephalopathy, characterized by diminished consciousness, drowsiness, or coma.
Arterial blood gas analysis in cases of lower airway secretion retention and respiratory failure typically shows decreased partial pressure of oxygen, elevated partial pressure of carbon dioxide, and may also include reduced blood pH.
Treatment
General Treatment
General treatment includes:
- Supplemental oxygen therapy.
- Administration of effective antibiotics to control infections.
- Timely correction of acid-base imbalances and electrolyte disturbances.
- Identification and management of the underlying cause or primary disease.
Management of Different Types of Respiratory Dysfunction
In critical situations, ensuring airway patency is a priority. Various approaches may be undertaken:
Medications delivered via nebulization are used to alleviate bronchospasm, reduce phlegm, and enhance the function of the mucociliary clearance system in the airway, thereby promoting the expulsion of lower airway secretions.
Fiberoptic (or electronic) bronchoscopy can be employed to remove retained secretions from the lower airways, thereby maintaining airway patency. In cases with severe or prolonged disease and large amounts of secretions, tracheostomy is preferred to reduce physiologically ineffective airway dead space and facilitate timely secretion removal.
The main purposes of tracheostomy include:
- Facilitating the immediate removal of lower airway secretions, which improves gas exchange.
- Reducing respiratory dead space, thereby increasing the volume of effective gas exchange.
- Providing access for mechanical ventilation and oxygen therapy.
- Lowering airway resistance to reduce the physical effort and oxygen consumption associated with breathing.