- Dyspnea is the medical term used to denote breathing discomfort.
- Stimulation of the ventilatory controller leads to a sensation of air hunger, the urge to breathe, or the need to breathe.
- Acute hypoxemia and hypercapnia can cause air hunger, even in the absence of activity of the ventilatory muscles; thus, these sensations do not arise from the muscles or act of breathing. Constraining ventilation can worsen air hunger for a given level of hypoxemia or hypercapnia.
- The dyspnea associated with exercise is commonly described as heavy breathing or breathing more. The receptors responsible for this sensation have not been clearly defined and may reside within the skeletal muscles.
- The sensation of increased work or effort of breathing is probably a reflection of a neural discharge from the motor cortex to the sensory cortex. This corollary discharge provides a “copy” to the sensory cortex of the motor output going to the ventilatory muscles.
- The sense of increased work or effort of breathing is most commonly seen when there is a disorder of the ventilatory pump.
- Stimulation of the pulmonary stretch receptors (PSRs) may alleviate the sensation of air hunger.
- The sensation of chest tightness, commonly seen in patients with asthma, probably arises from stimulation of pulmonary receptors as a consequence of bronchospasm.
- The sensation of chest burning associated with acute bronchitis is likely caused by the stimulation of RARs and C fibers in the lungs.
- Dissociation of efferent neural impulses arising within the controller and reafferent neural messages from receptors throughout the respiratory system increases the intensity of dyspnea.
- A patient with a single cardiopulmonary disorder may have multiple physiological abnormalities, each of which may give rise to a qualitatively distinct respiratory sensation.