Cough pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2], M.Umer Tariq [3] Abiodun Akanmode,M.D.[4]
Pathophysiology
The act of coughing is a vital one that leads to the mucociliary clearance of excess secretions from the airway and other parts of the respiratory tree.Cough occurs via a complex neurophysiologic cough reflex arc.
Cough Reflex
The cough reflex is constituted by 3 main components ie
- The Afferent pathway: This made up of sensory nerve fibers in the ciliated epithelium found in the upper airways. The afferent impulses are transmitted into the medulla.
- Central pathway: This is a central area located within the pons and brainstem. It coordinates the cough reflex arc.[1]
- The efferent pathway: cough impulses that are originated from the cough central travels via the vagus nerve,phrenic nerve, and spinal motor nerves to the diaphragm and abdominal wall muscles.
The Afferent sensory nerves:There are 3 major classes of afferent sensory nerves,this classification is based on there conduction velocity(A-fiber, > 3 m/s; C-fiber, < 2 m/s),origin ,myelination,neurochemistry etc.
- Rapidly adapting receptors (RARs)
- Slowly adapting stretch receptors (SARs)
- C-fibres.
Cough Mechanics
For an effective cough to be produced, a sequence of timed mechanical events divided into 3 phases has to take place.[2]
- The inspiratory phase: Here there in inhalation of an appropriate amount of gas, the amount of gas inhaled tends to vary little as 50% of the tidal volume to about 50% of the vital capacity.[3] [4]The inspiratory phase also bring about a structural change in the architecture of the expiratory muscles ie lenghtning and strentning of the expiratory muscles thus leading to the a generation of the required amount of intrathoracic pressure.
- The Compression Phase: The contraction of the muscles of the chest wall, abdominal wall, and the diaphragm against a closed glottis brings about a rapid increase in intrathoracic pressure.The pressure developed in the glotts during this compression phase could be as high as 300mmhg.[5]
- The Expiratory Phase: At this last phase the glottis is open and the large intrathoracic pressure that was developed in the compressive phase bringing about a large expiratory airflow and the unique sound associated with coughing.[5]
Dysfunction
The ability to cough efficiently and effectively is cough cannot be over
During Injections
Coughing during an injection can lessen the pain of the needle stick caused by a sudden, temporary rise in pressure in the chest and spinal canal, inhibiting the pain-conducting structures of the spinal cord.[6]
References
- ↑ Polverino M, Polverino F, Fasolino M, Andò F, Alfieri A, De Blasio F (2012). "Anatomy and neuro-pathophysiology of the cough reflex arc". Multidiscip Respir Med. 7 (1): 5. doi:10.1186/2049-6958-7-5. PMC 3415124. PMID 22958367.
- ↑ BUCHER K (1958). "Pathophysiology and pharmacology of cough". Pharmacol Rev. 10 (1): 43–58. PMID 13542168 PMID: 13542168 Check
|pmid=value (help). - ↑ Harris RS, Lawson TV (1968). "The relative mechanical effectiveness and efficiency of successive voluntary coughs in healthy young adults". Clin Sci. 34 (3): 569–77. PMID 5666883 PMID: 5666883 Check
|pmid=value (help). - ↑ Yanagihara N, Von Leden H, Werner-Kukuk E (1966). "The physical parameters of cough: the larynx in a normal single cough". Acta Otolaryngol. 61 (6): 495–510. doi:10.3109/00016486609127088. PMID 5963004.
- ↑ 5.0 5.1 McCool FD (2006). "Global physiology and pathophysiology of cough: ACCP evidence-based clinical practice guidelines". Chest. 129 (1 Suppl): 48S–53S. doi:10.1378/chest.129.1_suppl.48S. PMID 16428691 PMID: 16428691 Check
|pmid=value (help). - ↑ Usichenko, TI (2004). "Reducing venipuncture pain by a cough trick: a randomized crossover volunteer study". Anesthesia and Analgesia. 99 (3): 952–3. PMID 14742367. Unknown parameter
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