Chapter 73 - Cough Flashcards
brain nucleus key for modifying cough
nucleus tractus solitarius
Acute vs chronic cough
Acute: <3 wk
Chronic: >8 wk
Unexplained cough vs cough hypersensitivity syndrome
Unexplained: thorough eval, still cannot identify cause of cough
Cough Hyper/Neurogenic cough: pt appears to have common etiology for cough, but tx is not eliminating the cough…similar mechanism as chronic pain (lower threshold)
Different classes of cough receptors
chemoreceptors (water, ammonia, CO2, smoke, milk, gastric)
Mechanoreceptors (touch, flow, proprioception, laryngeal muscle contraction)
Irritant receptors: nociceptive C fibers, GPCR, transient receptor potential (ion channels)
pulmonary stretch receptors
C fiber activation may –> mast cell degran –> histamine, bradykinin, edeme
Location of cough receptors
subepithelial layer of respiratory tract, GI tract, CV system
Cough reflex neural components
Receptors –> SLN (internal) –> cortex –> nucleus ambiguus (medulla) –> RLN
can reflux remaining in the esophagus cause cough?
yes, even the distal esophagus, can also lead to bronchoconstriction
Most common causes of chronic cough
Upper airway cough syndrome (PND) asthma eosinophilic bronchitis GERD The above are responsible for 80% of chronic cough
What is atopic cough?
Cough in pt that are atopic without bronchial hyperresponsiveness, cough responds to antihistamines without inhaled steroids
Other causes of chronic cough
chronic bronchitis/infection ILD ACEi CHF Stimulation of hairs in EAC (Arnold's nerve)
Causes of upper airway cough syndrome
Rhinitis (allergic, vasomotor, postinfectious, anatomical abnl, irritant, medicamentosa, of pregnancy, occupational)
Bacterial sinusitis/AFS
Occupational/Environmental exposures causing chronic cough
Coal/hard rock mining, tunnel workers, concrete manufacturing
Secondhand smoke, particulate matter, irritant gas/fume, mold, perfumes, pollutants
Pathophysiology of UACS
initial stimulation of cough receptors by nasal drainage
may induce inflammation in the lower airways –> increase sensitivity to cough
irritant exposures release cytokines –> lower respiratory tract changes –> increased sensitivity to cough
So the condition is not just due to mechanical receptor stimulation, but also cough may be triggered by inflammatory signaling/neuroplastic changes that increase cough receptor sensitivity
Cough variant asthma
cough due to strong odor, exercise, other triggers
positive methacholine challenge
Nonasthmatic eosinophilic bronchitis
sx similar to asthma, neg methacholine test
eosinophils in sputum
Tx inhaled steroid
How often does cough occur with ACEi usage? Who gets is more commonly
5-35%
Women, nonsmokers, on it for HF rather than HTN
Tx UACS
First gen antihistamine (central cough suppression not seen in second gen)..chlorpheniramine, promethazine (phenergan), brompheniramine (Dimetan), benadryl
Decongestants
Nasal rinses if significant nasal sx
How to treat chronic cough if a cause is not obvious
Treat for the 4 most common causes empirically (UACS, asthma, non-asthmatic eosinophilic bronchitis, GERD)
UACS- Antihist/Decong
Asthma- ICS, bronchodil, leukotriene antag
NAEB- ICS
GERD- PPI, lifestyle/diet
Try this for 4 wk. If no resolution, investigate further
How long does it take for cough to subside after d/c ACEi? Can you try an ACEi again later?
2-4 wk
May try again in 2-3 mo but if cough returns do not try again
How to treat ACEi cough if you cannot d/c the ACEi
sodium cromoglycate theophylline sulindac indomethacin amlodipine ferrous sulfate picotamide
These can all suppress the cough
Treatments for unexplained cough
dextromethorphan benzonatate (DEC stretch receptor sensitivity in lungs) baclofen transdermal lidocaine patch nebulized lidocaine TCA gabapentin speech therapy
