Chronic inflammatory airway disease with progressive airflow limitation resulting in:


  • Based on a patient’s
    – Medical history
    – Physical exam
    – Pulmonary function tests (PFTs)
    – Laboratory tests
  • Spirometry (PFTs) is recommended in order to make the Dx
    • FEV1 is decreased to < 80% predicted
    • TLC is normal to elevated
    • FRC is usually elevated
    • Significant reversibility after inhaling a SABA
      • Increase by ≥ 12%
      • 200 mL in FEV1
  • Level of severity based on
    – Impairment, severity of symptoms
    – Risk, exacerbations
Diagnosis Summary
Condition Diagnostic
Asthma 20% FEV1 or PEF
12% FEV1 or PEF w/ Bronchodilator
Exercise-induced Asthma 15 % FEV1 or PEF w/ Exercise


What percentage of airway reversibility and change in FEV1 do you need in order to confirm the diagnosis of asthma?
A. 12% and 500 mL
B. 25% and 200 mL
C. 12% and 200 mL
D. 18% and 100 mL

Clinical Testing

  • Spirometry
    – Recommended for every pt ≥ 5 yrs of age***
  • If pt < 5 yrs of age, a therapeutic trial of medication is recommended
  • Studies specific to individual patients
    – Allergy testing
    – CXR
    – Bronchial provocation testing
    – Sinus x-rays or CT scan
    – GERD evaluation
    – CBC with eosinophils, total IgE, sputum exam

Asthma Triggers

URI Environmental Occupational or
Viral Allergens Allergens ASA Cardiac
Trigger for
-Tobacco smoke
-Wood burning stoves
Irritants NSAIDs   Consider in both
pediatric and adult
  Temperature   Beta
  Humidity   Sulfites

Management of Stable Asthma

Allergy Treatment

  • Key to control
    • Avoidance of allergens or environmental control.
    • For asthma patients found to be sensitive to house dust mite allergen: (Q)
      • Mattresses and pillows be encased in allergen-impermeable covers, and sheets
      • Blankets be washed weekly in hot water. A minimum water temperature of 54°C (130°F) is needed to kill house dust mites.
      • Although inefficient for removing live mites, vacuuming with a vacuum cleaner fitted with a HEPA filter removes mite allergen from carpets and may also be helpful.
      • Reducing indoor humidity to 60% or less (ideally 30%–50%), removing carpets from the bedroom, removing carpets that are laid on concrete elsewhere in the home
      • Minimizing the number of stuffed toys in children’s beds.
      • Avoiding sleeping or lying on upholstered furniture may also be effective.
      • Indoor air-filtering devices are not recommended because house dust mite allergens are relatively heavy and do not remain airborne.

        It should be noted that the efficacy of the interventions recommended by the NAEPP has not been clearly demonstrated.
  • Intranasal corticosteroids (Flonase)
    • Most effective controller therapy, should be 1st-line in persistant asthma
    • Reduce both allergic rhinitis and asthma sxs in pts with mild asthma.
    • Benefits: (Q)
      • Some benefits seen within weeks, but FULL-BENEFIT occurs in 1-2 Mo.
      • Decrease severity of Sx
      • Improve Peak Expiratory Flow & Spirometry
      • Diminished airway hyperresponsiveness
      • Prevent exacerbations
    • CAUTION:
      • Inhaled corticosteroids should be used with caution, if at all, in patients with:
        • Active or quiescent tuberculosis infection of the respiratory tract
        • Untreated systemic fungal, bacterial, parasitic, or viral infections; or
        • Ocular herpes simplex.
      • Alternative agents:
        • Cromolyn, leukotriene modifiers, and theophyllines
  • LABA:
    • Helpful for
      • Nocturnal Asthma
      • Exercise-induced Asthma
    • May worsen asthma in African Americans
  • Antihistamines alone or combined with a decongestant (Zyrtec-D)
    • May reduce asthma and rhinitis sxs
  • Leukotriene modulators (singulair)
    • Treat sxs of asthma and allergic rhinitis at the same time
    • No intrinsic smooth-muscle–relaxing ability, and therefore should not be used as quick-relief medications.
    • They are less potent than inhaled corticosteroids, but they can be used as alternative long-term controller agents in patients with mild persistent asthma, and as an adjunct to low- to medium-dose inhaled corticosteroids in patients with moderate persistent asthma.
    • The 2007 National Asthma Education and Prevention Program specifically recommends against using a leukotriene modifier as a substitute for an inhaled corticosteroid in patients taking long-acting β-agonists.
    • Although monitoring of liver enzymes is required in patients treated with zileuton, a 5-lipoxygenase inhibitor, it is not required in patients treated with leukotriene receptor antagonists such as montelukast or zafirlukast.
    • Leukotriene modifiers may be particularly effective in patients with exercise-induced asthma and aspirin-sensitive asthma.
  • Immunotherapy (Omalizumab)
    • May reduce development of asthma in pts with seasonal rhino-conjunctivitis
    • Only adjunctive therapy shown to add to the efficacy of high-dose inhaled corticosteroids plus LABA in pts who have persistent allergic asthma.

ED Management of Acute Exacerbation

Initial Assessment

Asthma Exacerbation: Adults

  • Acute Asthma Exacerbation =  Decreased PEF (< 50% predicted normal)
  1. Supplemental Oxygen to maintain O2 Sat > 90%
  2. Albuterol inhaled :
    • (90 micrograms/dose metered-dose inhaler)  4-8 puffs  q 20 minutes for up to 4 hrs, then q 1-4 hrs when required; OR
    • 2.5 to 5 mg nebulized q 20 minutes x 3 doses, followed by 2.5 to 10 mg q 1-4 hrs when required; or 10-15 mg/hour nebulized continuously
  3. Prednisone : 40-80 mg/day orally given in 1-2 divided doses
    Methylprednisolone : 60-80 mg orally once daily
    Dexamethasone : 16 mg orally once daily
Features of a moderate exacerbation include:
  • breathlessness at rest
  • loud expiratory wheezes on examination
  • agitation
  • use of accessory muscles of respiration with suprasternal retractions
  • a pulse rate of 100–120 beats/min
  • pulsus paradoxus of 10–25 mm Hg
  • a PEF or FEV1 of 40%–69% of predicted
  • a PaO2 ≥60 mm Hg
  • a pCO2 <42 mm Hg
  • an oxygen saturation of 90%–95%
  1. Supplemental Oxygen to maintain O2 Sat > 90%
  2. Albuterol inhaled :
    • (90 micrograms/dose metered-dose inhaler)  4-8 puffs  q 20 minutes for up to 4 hrs, then q 1-4 hrs when required; OR
    • 2.5 to 5 mg nebulized q 20 minutes x 3 doses, followed by 2.5 to 10 mg q 1-4 hrs when required; or 10-15 mg/hour nebulized continuously
  3. Ipratropium bromide inhaled : 500 micrograms nebulized given in combination and dosed with each administration of short-acting beta-2 agonist (usually every 20 minutes for 3 doses and then when required)
  4. Prednisone : 40-80 mg/day orally given in 1-2 divided doses
    Methylprednisolone : 60-80 mg orally once daily
    Dexamethasone : 16 mg orally once daily OR  4-8mg IV x1
  5. Magnesium sulfate : 2 g intravenously as a single dose given over 20 minutes

With impending respiratory failure:

  1. ICU
  2. +/- Mechanical Ventilation
    • For patients who are refractory to therapy and remain in severe respiratory distress.
    • Ventilatory management strategies often include:
      • LOW RR,
      • LOW tidal volumes,
      • High Inspiratory flow rates,
      • Avoidance of ventilator-applied positive end-expiratory pressure (PEEP).
  3. +/- IV ABx


  1. ICU admission plus oxygen plus consider assisted ventilation:
    Supplemental oxygen should be given by nasal cannulae or nonrebreather mask to achieve arterial oxygen saturation of >90%.
  2. Albuterol inhaled : 2.5 to 5 mg nebulized q 20 minutes x 3 doses, followed by 2.5 to 10 mg q 1-4 hrs when required; or 10-15 mg/hour nebulized continuously
    -- AND --
    Ipratropium bromide inhaled : 500 micrograms nebulized given in combination and dosed with each administration of short-acting beta-2 agonist (usually every 20 minutes for 3 doses and then when required)
  3. Hydrocortisone sodium succinate : 100 mg intravenously every 8 hours -OR-
    Prednisone : 40-80 mg/day orally given in 1-2 divided doses -OR-
    Methylprednisolone : 60-80 mg orally once daily
  4. Magnesium sulfate : 2 g intravenously as a single dose given over 20 minutes
  5. Heliox: 80:20 or 70:30 helium to oxygen ratios have been used.
    Coadministration of a helium-oxygen gas mixture (heliox) and bronchodilators may be helpful in selected patients with respiratory failure but is controversial.
  6. Mechanical Ventilation
    • For patients who are refractory to therapy and remain in severe respiratory distress.
    • Ventilatory management strategies often include:
      • LOW RR,
      • LOW tidal volumes,
      • High Inspiratory flow rates,
      • Avoidance of ventilator-applied positive end-expiratory pressure (PEEP).
  7. IV ABx

Asthma Exacerbation: Child

  • Acute Asthma Exacerbation =  Decreased PEF (< 50% predicted normal)
  1. Supplemental Oxygen to maintain O2 Sat > 92%
  2. Albuterol SVN
    Small Volume Neb., 0.15 mg/kg/dose, Can repeat q20min x 3 doses, then q1-4h PRN,
    Max dose: 5mg
  3. Albuterol MDI
    Metered dose inh., 0.25 puffs/kg
    Max: 10 puffs
  4. Ipratropium Bromide
    < 20 kg: 250 μg/dose
    > 20 kg: 500 μg/dose
    Combine with first dose albuterol Tx
    -AVOID- MDI w/ Hx of nut allergy

  5. Continous Albuterol Neb
    5-10 kg: dose 10 mg/hr
    10-20 kg: dose 15 mg/hr
    > 20 kg: dose 20 mg/hr
  6. Steroids:
    • Prednisone/Prednisolone PO
      2 mg/kg, Administer to those who fail initial inhalation therapy
      Max dose: 60 mg
    • Dexamethasone
      0.6 mg/kg
      Max: 16 mg
    • Methylprednisolone
      2 mg/kg IV
  7. NEB Steroid (budesonide 0.5mg)
    Racemic Epi 11.25mg NEB   or   NEB Terbutiline
    Benadryl 1.25mg/kg
    Ibuprofen 10mg/kg
    (Arachidonic acid blocker - Block inflammatory pathway)
  8. Epinephrine 1:1000 IM/SC
    0.01 mL/kg
    Max: 0.4mg

No response to initial Tx of Impending Resp. Failure:

  1. Terbutaline SC
    0.01 mg/kg
    Max: 0.4 mg (0.4 ml of 1 mg/ml sol)
  2. Terbutaline IV
    10 μg/kg bolus over 10 min, then 0.3 - 0.5 μg/kg/min
  3. Theophylline
    5 mg/kg IV loading dose, followed by 1 mg/kg/hr continuous infusion
  4. Magnesium Sulfate IV/IM
    50 mg/kg/dose over 20 min q4-6h
    Give NS Bolus first to avoid hypotension
    Max: 2 g
  5. Ventilation plus transfer to ICU
    Indications for intubation and mechanical ventilation:
     Clinical symptoms of exhaustion, cyanosis, or drowsiness with hypoxemia and hypercapnia.
     Intubation is preferred before the onset of respiratory arrest.
     Fluid replacement will be required in these patients, as they are frequently fluid depleted, and initiation of positive pressure ventilation may be accompanied by hypotension.
     Noninvasive ventilation may be used as a rescue therapy to avoid intubation. Continuous positive airways pressure, CPAP, or bi-level non-invasive ventilation can be applied using either a nasal or full-face mask interface.
     Sedation is occasionally necessary for patient tolerance, but should be used with caution


  • Azithromycin: 10 mg/kg orally once daily on the first day, followed by 5 mg/kg once daily for 4 days
  • Clarithromycin: 15 mg/kg/day orally given in divided doses every 12 hours, maximum 1000 mg/day
  • Erythromycin base: 30-50 mg/kg/day orally given in divided doses every 6 hours


Asthma Exacerbation: Pregnancy

  • The principles of managing acute asthma in pregnancy are similar to those for the nonpregnant state.
  • They consist of
    • Repetitive lung function measurements
    • Maintenance of oxygen saturation at >95%
    • Administration of repetitive inhaled β2 agonists, and
    • Early administration of systemic corticosteroids, in addition to fetal monitoring.
  • Early intervention during acute exacerbation is key to the prevention of impaired maternal and fetal oxygenation.
  • Uncontrolled asthma:
    • Associated with a variety of maternal and fetal complications, including
      • Hyperemesis
      • Hypertension
      • Toxemia
      • Vaginal hemorrhage
      • Complicated labor
      • Intrauterine growth restriction
      • Preterm birth
      • Increased perinatal mortality, and
      • Neonatal hypoxemia.
  • *** To date, no asthma medication qualifies for the U.S. Food and Drug Administration use-in-pregnancy category A rating (for which adequate well-controlled studies in pregnant women have failed to demonstrate risk to the fetus). However, problems as a result of routine treatment of asthma in the ED have not been reported.
  • Hyperventilation of pregnancy leads to a higher PaO2 and a diminished PaCO2. Thus, a PaO2 of <70 mm Hg in pregnant women with acute asthma represents fairly severe hypoxemia, and a PaCO2 of >35 mm Hg represents respiratory failure.
  • During asthma exacerbation, the normal alkalosis of pregnancy is aggravated, leading to a decrease in placental blood flow.
  • Hypoxemia is usually more severe in the fetus than in the mother.


  • β-2 Agonists and inhaled corticosteroids are considered safe during pregnancy and are recommended as a routine part of asthma management.
  • As in non-pregnant patients, a short burst of PO steroid (prednisone, 40 to 60 milligrams per day) or its equivalent, and inhaled corticosteroids in patients with mild persistent or more severe asthma should be considered for pregnant asthmatics discharged from the ED after treatment for an exacerbation.

Aspirin-induced asthma

  • A syndrome of rhinorrhea, nasal polyps, sinusitis, conjunctival edema, and asthma following aspirin ingestion.
  • Aspirin-induced asthma usually begins with perennial vasomotor rhinitis, followed by hyperplastic rhinosinusitis with nasal polyps.
  • Cross-reactivity may be seen with
    • NSAIDs, including indomethacin, naproxen, ibuprofen, fenoprofen, mefenamic acid, and phenylbutazone.
  • Safe alternatives to aspirin include:
    • Salsalate
    • Acetaminophen.


  • Leukotriene modifiers are regarded as the treatment of choice for patients with aspirin-induced asthma.
    • Singulair

Exercise-induced asthma

  • Exercise-induced bronchospasm should be anticipated in all asthma patients.
  • Exercise as a stimulus differs from other asthma provocations (e.g., allergens, viral infections, air pollutants) in that it does not evoke any long-term sequelae, nor does it increase airway reactivity.


  • 15 % FEV1 or PEF w/ Exercise.
  • It usually occurs during or after exercise, reaches its peak 5–10 minutes after stopping the activity,
  • Remits spontaneously within the next 20–30 minutes.

Differential Dx

  • Other conditions associated with breathing difficulties during exercise, particularly vocal cord dysfunction, can be confused with exercise-induced asthma.


  • Like usual Asthma (albuterol, Ipratropium)
  • LABA to prevent EIA

Checklist for ED Discharge

Intervention Dose/Timing Education/Advice M.D./R.N. Initials
Inhaled medications (e.g., MDI with valved holding chamber; nebulizer) Select agent, dose, and frequency (e.g., albuterol). Teach purpose.  
  Short-acting β2 agonist
2–6 puffs every 4 h for __ days. Teach and check technique.  
  Corticosteroids Low to medium dose for patients with chronic persistent asthma. For MDIs, emphasize the importance of using a spacing device or holding chamber.  
Oral medications Select agent, dose, and frequency (e.g., prednisone 40 milligrams once a day for 10 d). Teach purpose.  
Teach side effects.
Peak flow meter For selected patients: measure a.m. and p.m. peak expiratory flow, and record best of three tries each time. Teach purpose.  
Teach technique.
Distribute peak flow diary.
Follow-up visit If possible, make appointment for follow-up care with primary clinician or asthma specialist or advise patient to make appointment. Advise patient (or caregiver) of date, time, and location of appointment, ideally within 7 d of hospital discharge.  
Action plan Before or at discharge. Instruct patient (or caregiver) on simple plan for actions to be taken when symptoms, signs, and peak expiratory flow values suggest recurrent airflow obstruction.  


  • Follow-up:
    – Every 2-6 wk intervals
    – Once controlled, reassess at least every 1-6 Mo
  • Measures of control are the same as those to assess severity plus use of,
  • Validated multidimensional questionnaires like the asthma control test (ACT)
  • Step down can be considered if asthma is well controlled for 3 months or more, but do not stop ICS completely
  • Decrease dose of ICS gradually
    – 25% to 50% q 3 mo
    – Deterioration in asthma control is highly variable

Asthma Action Plans

  • Reduce hospitalizations, ED visits, symptoms, night waking, time off work, and quality of life
  • Especially for patients with moderate or severe persistent asthma
  • Patients with a history of severe exacerbations.
  • Pts with poorly controlled Asthma.
  • Action plans should:
    • Describe how to recognize and respond to worsening asthma
    Individualize the plan
    • Provide advice about a change in ICS
    • Base action plan on personal best PEF rather than predicted
  • Green Zone:
    • Usual activity
    • PEF 80% or more of personal best
  • Yellow Zone:
    • Some of usual activity
    • PEF 50%-80% of personal best
  • Red Zone:
    • Cannot do usual activities
    • PEF less than 50% of personal best
GREEN 80 - 100 % of the usual or normal peak flow readings are clear A peak flow reading in the green zone indicates that the asthma is under good control.
YELLOW 50 - 79 % of the usual or normal peak flow readings Indicates caution. It may mean respiratory airways are narrowing and additional medication may be required.
RED < 50 % of the usual or normal peak flow readings Indicates a MEDICAL EMERGENCY. Severe airway narrowing may be occurring and immediate action needs to be taken. This would usually involve contacting a doctor or hospital.

Risk factors for death from asthma include the following:

  • Past history of sudden severe asthma exacerbation
  • Prior intubation for asthma
  • Prior admission to an ICU for an exacerbation
  • 2 hospitalizations for asthma during the past year
  • 3 ER visits for asthma during the past year
  • Hospitalization or an ER visit for asthma during the past month
  • Use of > 2 canisters per month of an inhaled short-acting β2-agonist
  • Difficulty perceiving airflow obstruction or severity of exacerbations
  • Lack of a written asthma action plan
  • Comorbidity (as from cardiovascular disease or COPD)
  • Serious psychiatric disease or psychosocial problems
  • Low socioeconomic status and inner-city residence
  • Illicit drug use
  • Sensitivity to Alternaria

ADMISSION ORDERS: Asthma Exacerbation

1. Admit to:

2. Diagnosis: Exacerbation of asthma

3. Condition:

4. Vital Signs: q6h. Call physician if P >140; R >30, <10; T >38.5°C; pulse oximeter <90%

5. Activity: Up as tolerated.

6. Nursing: Pulse oximeter, bedside peak flow rate before and after bronchodilator treatments.

7. Diet: Regular.

8. IV Fluids: D5 ½ NS at 125 cc/h. [aggressive hydration NOT recommended]

9. Special Medications:

-Oxygen 2 L/min by NC. Keep O2 sat >90%.

Beta-Agonists and Ipratropium - Acute Treatment:

-Albuterol (Ventolin) 2.5-5 mg in 2.5 mL NS q20min for 3 doses, then 2.5 to 10 mg every one to four hours as needed until peak flow meter ≥200-250 L/min and sat ≥90%, then q4h OR

-Levalbuterol (Xopenex) 0.63-1.25 mg by nebulization q6-8h prn.

-Albuterol (Ventolin) MDI 3-8 puffs, then 2 puffs q3-6h prn, or powder 200 mcg/capsule inhaled qid.

-Albuterol/Ipratropium (Combivent) 2-4 puffs qid.

Ipratropium (Atrovent) 500 mcg nebulized every 20 minutes for three doses, then as needed.

Magnesium sulfate, 2 grams infused intravenously over 20 minutes.

Systemic Corticosteroids:

-Methylprednisolone (Solu-Medrol) 60-125 mg IV q6h; then 30-60 mg PO qd.OR

-Prednisone 20-60 mg PO qAM.

Maintenance Inhaled Corticosteroids (adjunct therapy):

-Advair Diskus (fluticasone/salmeterol) one puff bid [doses of 100/50 mcg, 250/50 mcg, and 500/50 mcg]. Not for acute attacks.

-Beclomethasone (Beclovent) MDI 4-8 puffs bid, with spacer 5 min after bronchodilator, followed by gargling with water.

-Triamcinolone (Azmacort) MDI 2 puffs tid-qid or 4 puffs bid.

-Flunisolide (AeroBid) MDI 2-4 puffs bid.

-Fluticasone (Flovent) 2-4 puffs bid (44 or 110 mcg/puff).

Maintenance Treatment:

-Salmeterol (Serevent) 2 puffs bid; not effective for acute asthma because of delayed onset of action.

-Ipratropium (Atrovent) MDI 2-3 puffs tid-qid.

Acute Bronchitis

-Ceftriaxone (Rocephin) 2 gm IV q12h OR

-Cefotaxime (Claforan) 2 gm IV q6h OR

-Levofloxacin (Levaquin) 750 mg PO/IV PO qd OR

-Moxifloxacin (Avelox) 400 mg every 24 hours.

Prevention and Prophylaxis:

-Cromolyn (Intal) 2-4 puffs tid-qid.

-Nedocromil (Tilade) 2-4 puffs bid-qid.

-Montelukast (Singulair) 10 mg PO qd.

-Zafirlukast (Accolate) 20 mg PO bid.

-Zileuton (Zyflo) 600 mg PO qid.

10. Symptomatic Medications:

-Docusate (Colace) 100 mg PO qhs.

-Famotidine (Pepcid) 20 mg IV/PO q12h OR

-Lansoprazole (Prevacid) 30 mg qd.

11. Extras: Portable CXR, ECG, pulmonary function tests before and after bronchodilators.

12. Labs: ABG, CBC, CMP. Theophylline level. Sputum Gram stain, C&S.


ITE 2013, Q#105.
A 12-year-old female with asthma sees you for a follow-up visit. The girl’s mother states that she is currently coughing several days per week and uses her albuterol (Proventil, Ventolin) inhaler 3–4 times weekly. She has awakened with a cough during the night 3 times in the last month. The patient thinks her asthma only mildly affects her day-to-day activity. In-office spirometry reveals that her FEV1 is 83% of predicted, with a normal FEV1/FVC ratio.

Which one of the following asthma classifications best fits this patient’s presentation?

A) Intermittent
B) Mild persistent
C) Moderate persistent
D) Severe persistent
E) Status asthmaticus


ITE 2013, Q#232.
A 12-year-old female is brought to the emergency department with an asthma exacerbation. Which one of the following indicates that her exacerbation may be life threatening?

A) A past need for systemic corticosteroids
B) Inspiratory and expiratory wheezing in both lung fields
C) Paradoxical chest movement
D) A PaCO2 <35 mm Hg
E) An FEV1 that is 60% of expected after initial treatment in the emergency department


  • Signs that an asthma exacerbation may be life threatening include
    • altered mental status,
    • absence of wheezing, and
    • paradoxical chest or abdominal movement.
  • A PaCO2 >42 mm Hg may indicate impending respiratory failure; levels <40 mm Hg would be expected with hyperventilation of any cause.
  • An FEV1 <40% of expected, especially after initial treatment in the emergency department, is an indication for admission.
  • Systemic corticosteroids are frequently used for even moderate asthma exacerbations.


68. A previously healthy 26-year-old white male carpenter reports episodes of chest tightness and dyspnea. He states that he feels better on weekends.
He most likely has

A) hypersensitivity pneumonitis
B) toxic pneumonitis
C) byssinosis
D) benign pleural effusion
E) occupational asthma


  • The diagnosis of occupational asthma can be made when both bronchospasm and its relationship to the work environment can be demonstrated. A history of cough, wheezing, chest tightness, or episodic dyspnea in varying combinations or singly should lead one to suspect bronchospasm. Relating bronchospasm to the work environment can be done in several ways. A history of exposure to a known sensitizer is helpful, as is a pattern of symptoms occurring after exposure. With many agents the onset of symptoms may be delayed up to several hours. A 10% decrease in FEV1 measured before and after a work
    shift supports the diagnosis. Improvement of bronchospasm with removal from exposure also suggests the diagnosis. Treatment includes both standard pharmacologic therapy and removal from exposure as soon as possible.
  • Hypersensitivity pneumonitis is an immune-mediated syndrome that is not as common as occupational asthma. It begins with malaise, fever, and myalgias 4–6 hours after exposure to an antigen to which the person has become sensitized.
  • Byssinosis is due to exposure to the dust of hemp, flax, or cotton. Symptoms vary from reversible chest tightness on one or more days early in the work week to chronic bronchitis and permanent obstructive lung disease.
  • Toxic pneumonitis or pulmonary edema is the result of very high exposure to irritant gases, metal dust, or metal fumes, usually associated with unusual
    circumstances such as a fire, explosion, or spill.
  • Benign pleural effusions are the most common sequela during the first 20 years after asbestos exposure. The diagnosis is one of exclusion, made by ruling out other causes of exudative effusions in workers with known asbestos exposure.

    Ref: Goldman L, Schafer AI (eds): Goldman’s Cecil Medicine, ed 24. Elsevier Saunders, 2011, pp 567-569.