Whale in Medicine

SPUTUM

• Because sputum consists mainly of secretions from the tracheobronchial tree rather than the upper airway, the finding of alveolar macrophages and other inflammatory cells is consistent with a lower respiratory tract origin of the sample, whereas the presence of squamous epithelial cells in a "sputum" sample indicates contamination by secretions from the upper airways.

CLASSIFICATION of cough

• Cough can be classified based upon the duration of the cough；Acute cough exists for less than three weeks and is most commonly due to an acute respiratory tract infection；Cough that present three to eight weeks is subacute；more than eight weeks is chronic cough.

   

• Cough reflex arc: each cough occurs through the stimulation of a complex reflex arc. This is initiated by the irritation of cough receptors that exist not only in the epithelium of the upper and lower respiratory tracts, but also in the pericardium, esophagus, diaphragm, and stomach. Chemical receptors sensitive to acid, cold, heat, capsaicin-like compounds, and other chemical irritants.

   

• Mechanical cough receptors can be stimulated by triggers such as touch or displacement. Laryngeal and tracheobronchial receptors respond to both mechanical and chemical stimuli.

   

CAUSES of cough

• It is commonly held that use of an angiotensin-converting enzyme inhibitor; post-nasal drainage; gastroesophageal reflux; and asthma, alone or in combination, account for more than 90% of patients who have chronic cough and a normal or noncontributory chest radiograph.

   

• Post-nasal drainage of any etiology can cause cough as a response to stimulation of sensory receptors of the cough-reflex pathway in the hypopharynx or aspiration of draining secretions into the trachea. Clues to this etiology include symptoms of post-nasal drip, frequent throat clearing, and sneezing and rhinorrhea.

   

• The most common etiologies of chronic cough are upper airway cough syndrome (due to postnasal drip), asthma, and gastroesophageal reflux. On the other hand, a post-infectious etiology is a particularly common cause of subacute cough. One study showed that in nearly half of patients, subacute cough was post infectious and resolved without specific therapy.

   

• Upper airway cough syndrome: several studies suggest that upper airway cough syndrome related to postnasal drip is a common cause of subacute and chronic cough. Underlying reasons for postnasal drip include allergic, perennial nonallergic, and vasomotor rhinitis；acute nasopharyngitis；and sinusitis. Once secretions are present in the upper airway, cough is probably induced by stimulation of cough receptors within the laryngeal mucosa.

   

  QUALITY and QUANTITY of postnasal drainage and its therapy

• On speculum examination of the nose, one may see excess mucoid or purulent secretions, inflamed and edematous nasal mucosa, and/or nasal polyps; in addition, one might visualize secretions or a cobblestoned appearance of the mucosa along the posterior pharyngeal wall. Unfortunately, there is no means by which to quantitate post-nasal drainage.

   

• In many instances, one is left to rely on a qualitative judgment based on subjective information provided by the patient. This assessment must also be counterbalanced by the fact that many people who have chronic post-nasal drainage do not experience cough.

   

• Therapy for post-nasal drainage depends on the presumed etiology (infection, allergy, or vasomotor rhinitis) and may include systemic antihistamines; antibiotics; nasal saline irrigation; and nasal pump sprays with corticosteroids, antihistamines, or anticholinergics.

   

  POST-NASAL DRIP

• Symptoms of postnasal drip include frequent nasal discharge, a sensation of liquid dripping into the back of the throat, and frequent throat clearing. However, postnasal drip may also be “silent”, so that the absence of these symptoms does not necessarily exclude the diagnosis. Clues on physical examination are a cobblestone appearance to the nasopharyngeal mucosa and the presence of secretions in the nasopharynx.

   

• References:

  Harrison s Principles of Internal Medicine 18 Ed

  UpToDate _ Evaluation of subacute and chronic cough in adults

• Comments:
1. postnasal drip 的症狀常見於chronic cough、subchronic cough、asthma；但是postnasal drip並不是就一定會造成dyspnea，儘管dyspnea常見於asthma的病人。
2. Dyspnea, wheezing, and airways obstruction: is it asthma?
• Tracheobronchial adenoid cystic carcinoma(ACC) typically presents with symptoms of cough, dyspnea, and hoarseness. [Standard therapy is surgical resection often followed by radiotherapy].
3. Pseudo-asthma: when cough, wheezing, and dyspnea are not asthma. Cough that is misdiagnosed as asthma can occur with pertussis, cystic fibrosis, primary ciliary dyskinesia, airway abnormalities such as tracheomalacia and bronchomalacia, chronic purulent or suppurative bronchitis in young children, and habit-cough syndrome. On the other hand, the respiratory sounds and dyspnea(on exertion) may be happened due to other causes.
4. Postnasal drip: www.entnet.org/content/post-nasal-drip