From the Guidelines
Breathing is a complex process controlled by the respiratory control system, which consists of sensory receptors, central integrating circuits, and motor output to the respiratory muscles, as described in the American Journal of Respiratory and Critical Care Medicine 1. The mechanism of breathing involves the coordination of various components, including the respiratory muscles, lungs, and nervous system.
- The respiratory muscles, such as the diaphragm and external intercostal muscles, contract and relax to expand and deflate the chest cavity, creating negative pressure inside the lungs to draw in air.
- The lungs, specifically the alveoli, are responsible for exchanging oxygen and carbon dioxide between the air and bloodstream.
- The nervous system, particularly the respiratory center in the brainstem, monitors carbon dioxide levels in the blood and adjusts breathing rate and depth accordingly, as noted in the ats/ers statement on respiratory muscle testing 1. This process is essential for maintaining normal levels of minute ventilation and arterial PCO2, even in cases of marked weakness of the respiratory muscles, where the control system compensates by driving the respiratory muscles harder than normal, as discussed in the study 1. Key aspects of the breathing mechanism include:
- The role of chemoreceptors in measuring arterial P CO, P O2, and pH2 to provide information about the status of the respiratory system 1.
- The importance of the central integrating circuits in processing this information and adjusting motor output to the respiratory muscles 1.
- The use of laboratory tests, such as inhalation of hypercapnic or hypoxic gas mixtures, to assess the control system and diagnose abnormalities in respiratory function, as described in the study 1.
From the FDA Drug Label
CLINICAL PHARMACOLOGY 12. 1 Mechanism of Action Albuterol sulfate is a beta2-adrenergic agonist. The pharmacologic effects of albuterol sulfate are attributable to activation of beta2-adrenergic receptors on airway smooth muscle. The FDA drug label does not answer the question.
From the Research
Mechanism of Breathing
The mechanism of breathing involves the contraction and relaxation of various muscles, including the diaphragm and intercostal muscles, to expand and contract the chest wall and lungs.
- The diaphragm is the main inspiratory muscle, and when its muscle fibers are activated, they shorten, causing the dome of the diaphragm to descend and pleural pressure to fall 2.
- The external intercostals, parasternal intercostals, and scalenes help to expand the rib cage during inspiration, increasing the volume of the thoracic cavity and allowing air to flow into the lungs 2.
- During expiration, the abdominal muscles contract, producing a rise in abdominal pressure that leads to a cranial displacement of the diaphragm and a rise in pleural pressure, helping to deflate the lungs 2.
Respiratory Failure
Respiratory failure can occur when the respiratory system is unable to oxygenate the blood and/or remove carbon dioxide from the blood.
- Acute hypercapnic respiratory failure frequently occurs in patients with chronic obstructive pulmonary disease (COPD) experiencing acute exacerbations, and can be treated with noninvasive positive pressure ventilation (NPPV) 3.
- NPPV can help to reduce the need for endotracheal intubation, inhospital mortality, and the mean length of hospital stay in patients with acute respiratory failure due to COPD 3.
Treatment of Acute Respiratory Failure
The treatment of acute respiratory failure depends on the underlying cause and severity of the condition.
- High-flow nasal cannula oxygen therapy, continuous positive airway pressure (CPAP), and bilevel positive airway pressure (BiPAP) may be beneficial alternatives to invasive mechanical ventilation (IMV) for COVID-19-associated acute respiratory failure 4.
- NPPV can be used to wean patients from IMV, and has been shown to reduce mortality, nosocomial pneumonia, and weaning failure in patients with COPD 3.