Introduction

Defense Mechanism

• Protects airways from adverse effects of inhaled noxious substances
• Clears excessive bronchial secretions

Scope of Problem

• 13 million patients in 1979 with complaint of cough
• Second most common complaint
• May accompany upper or lower respiratory tract infection for several weeks
• Considered "normal" up to 2 months after illness
• Occurs in up to 75% of smokers

Necessity to Cough

Cough is an important normal protective reflex activity which can become a major sign and symptom of lung disease and a significant clinical problem for a large number of patients.

The normal mechanism occurs with an inhalation of gas above FRC followed by closure of the glottis and an increase in intrapleural pressure to 100 cm H2O. About 0.2 seconds after glottis closure, it reflexively opens with resulting turbulent expiratory flow.

Cough Reflex

The cough reflex has 5 components: 1) cough receptors, 2) afferent nerves, 3) a poorly defined cough center, 4) efferent nerves, 5) effector muscles. Key to cough particularly in pathology is the cough receptors. In summary, cough receptors are throughout all the airways and upper G.I. tract. as well as the pericardium and diaphragm.

Causes of Cough

Acute Cough

• Two of these causes include bronchopulmonary infection ( ex. bronchitis or pneumonia) and environmental causes such as cigarette smoke or other air pollutants such as ozone.

Chronic Cough

• Persistent cough for greater than 2 weeks without a recognized etiology presents an important clinical problem. The persistence of cough can be do to stimulation of any of the numerous cough receptors by a wide variety of causes.
• The approach to a chronic cough requires consideration of the anatomical distribution of the cough receptors and the knowledge of the likely of the various etiologies of chronic cough.
• Common causes of chronic cough
  • airways hyperactivity
  • post nasal drip
  • gastro-esophageal reflux
• Less common but important causes of chronic cough
  • lung cancer
  • laryngeal disease
  • drug induced (ACE inhibitors)
  • ear disease
  • psychogenic

Mechanism - Voluntary or Psychogenic

Reflex Stimulation

• Cough receptors:
  • extrathoracic: nose, oropharynx, larynx, upper trachea
  • intrathoracic: rapidly adapting irritant receptors in epithelium of lower trachea and large central bronchi
  • other locations: tympanic membrane, diaphragm, stomach
• Afferent nerves: trigeminal, glossopharyngeal, superior laryngeal, vagus
• Efferent nerves: recurrent laryngeal nerves, vagus, corticospinal tract and peripheral nerves
• Reflex begins with deep inspiration, followed by glottic closure, diaphragmatic relaxation, and thoracic and abdominal expiratory muscle contraction. Posterior wall of airway invaginates and causes shearing of mucus.
• Positive pleural pressure generated up to 100-300 mm Hg; peak flows of 12 L/sec

Productive Cough

• "Normal" quantity unknown; usually cleared by mucociliary action alone
• Accumulate secretions because of:
  • excessive production
  • altered physical properties
  • deficient clearance

Nonproductive Cough: Irritative Phenomenon

• May be mechanical, chemical, thermal, or inflammatory
• Alteration of surface epithelium of major airways exposes irritant receptors which become sensitized and cause cough

Complications

• Provokes more coughing
• Paroxysms may stimulate vomiting
• Syncope/dizziness
• Utter exhaustion
• Rib fractures
• Muscle tears
• Vertebral compression fractures
• Pneumoperivarices
• Headache
• Rupture spleen
• Esophageal variceal bleeding
• Stress incontinence

Evaluation

Diagnostic Features

• Acute or chronic
  • acute:
    viral nasopharyngitis or laryngotracheobronchitis inhalation allergenic or irritative substance
  • chronic:
    chronic bronchitis (cough with sputum for 3 months in 2 consecutive years), bronchiectasis, tuberculosis, carcinoma, asthma
• Productive or nonproductive
  • productive with underlying inflammatory process
  • nonproductive: mechanical or irritative stimulus
• Type and quantity of sputum
  • foul smelling: anaerobic infection abscess/necrotizing pneumonia
  • abundant frothy/salivalike sputum: bronchoalveolar carcinoma
  • pink-tinged, foamy sputum: pulmonary edema
  • rust-colored: pneumococcal pneumonia
  • chronic copious purulent sputum ñ blood streaking: bronchiectasis
• Character
  • brassy: from major airways involvement/tracheal disease
  • barking or croupy: laryngeal disease
  • paroxysmal whoops: pertussis
  • nocturnal: congestive cardiac failure or asthma; gastroesophageal reflux
  • meals: hiatal hernia or gastroesophageal reflux
  • ams: severe bronchitis or bronchiectasis
• Time relationships
• Associated features
  • wheezing
  • stridor
  • fevers and chills
  • weakness and weight loss
  • recurrent pneumonias
  • smoking history
  • repeated throat clearing/sensation of phlegm in throat
  • occupational history

Physical Examination

• Breathing pattern and rate
• Accessory muscle use
• Lungs: wheezes and rhonchi, crackles, dullness to percussion
• HEENT: hairs on tympanic membranes, nasal mucosal edema/polyps, oropharyngeal secretions, sinus tenderness
• Neck: mass or enlarged thyroid

Roentgenographic Examination

• PA and lateral chest
• Paranasal sinuses
• CT thorax

Laboratory Examination

• Eosinophils
• IgE
• ESR or specific testing for collagen vascular disease, sarcoidosis, infection

Pulmonary Function Testing

• Spirometry
• Volumes
• Bronchoprovocation testing

Fiberoptic Bronchoscopy

Treatment

• Aimed at specific diagnosis
• Empiric therapeutic trial of bronchodilators, antacids
• Topical nasal steroids
• Systemic steroids
• Antihistamines and decongestants
• Antibiotics
• Consider hydration, expectorants, mucolytics
• Dextromethorphan or codeine for post viral cough
• Intractable cough due to irreversible disorder: narcotics, nebulized lidocaine
• Biofeedback