Respiratory

Asthma: occupational asthma evaluation and management

Clinical Overview and When to Suspect Occupational Asthma

— Sensitizer-induced (allergic) OA: latency period (weeks to years), IgE-mediated (HMW antigens) or non-IgE (LMW chemicals like isocyanates).

— Irritant-induced OA / RADS (Reactive Airways Dysfunction Syndrome): no latency, follows a single high-level irritant exposure (chlorine spill, ammonia leak), symptoms <24 hours after exposure, persisting ≥3 months.

— Work-exacerbated asthma (WEA): pre-existing asthma worsened by workplace triggers — managed differently from true OA.

— New-onset wheeze, cough, chest tightness, or dyspnea in an adult worker.

— Symptoms improve on weekends, vacations, or days off, worsen on return to work.

— Rhinoconjunctivitis preceding lower-airway symptoms (classic with HMW allergens like flour, animal dander, latex).

— Index occupations: bakers (flour), healthcare workers (latex, glutaraldehyde), spray painters (isocyanates), farmers (grain dust), hairdressers (persulfates), welders, woodworkers (western red cedar/plicatic acid), laboratory animal workers.

— OA is potentially curable if diagnosed early and exposure ceases — delay leads to persistent airway remodeling.

— Has workers' compensation, disability, and OSHA reporting implications that the generalist must initiate.

Definition: Asthma caused or worsened by exposures in the workplace; accounts for ~15% of adult-onset asthma in the US.

When to suspect on Step 3:

Why it matters for the family/preventive medicine boards:

Board pearl: Any adult with new-onset asthma after age 18 should be screened with an occupational history — ask "What do you do for work, and do your symptoms change on days off?" This single question is the most cost-effective screening tool.

Step 3 management: Document a detailed occupational/exposure timeline at the first visit; do not defer to pulmonology — initial workup (PEF diary, spirometry, occupational history) is the PCP's job before referral.

Presentation Patterns and Key History

— Job title AND specific tasks/materials (not just "factory worker" — ask about chemicals, dusts, animal proteins, cleaning agents).

— Temporal pattern: symptoms during shift, end of shift, 4–12 hours later (late asthmatic response — classic for LMW agents like isocyanates), or overnight.

— Improvement off work: weekends, vacations ≥1–2 weeks; sensitizer OA may take days–weeks to clear.

— Latency: months to years of asymptomatic exposure before sensitization (HMW/LMW agents) vs. no latency in RADS.

— Co-workers affected? Suggests a high-exposure environment.

— Personal atopy, smoking, prior asthma (distinguishes WEA from new OA).

— Safety Data Sheets (SDS) — request from employer; lists sensitizers and irritants.

— Baker's asthma: wheat flour, alpha-amylase enzymes; rhinitis precedes asthma.

— Isocyanate asthma: auto body shops, polyurethane foam — late-phase reactions, frequently negative skin tests.

— Western red cedar asthma: plicatic acid; symptoms may persist years after cessation.

— Cleaning workers: quaternary ammonium compounds, bleach mixing → RADS.

Symptom cluster: episodic wheeze, cough (often nocturnal after workdays), chest tightness, dyspnea — indistinguishable from non-occupational asthma except for the temporal-work relationship.

Key historical elements (must elicit all):

Pattern recognition:

Key distinction: OA = caused by work exposure (new sensitization or irritant injury). Work-exacerbated asthma = pre-existing asthma triggered by nonspecific workplace factors (cold air, exertion, dust). The distinction drives compensation eligibility and management — OA usually requires complete removal, WEA may tolerate exposure reduction.

Board pearl: A weekend-improvement pattern has high sensitivity but low specificity (50% of asthmatics report it). Objective testing is required — never diagnose OA on history alone.

Step 3 management: Obtain SDS sheets and a 2–4 week serial peak flow diary (4×/day, work and off-work periods) before the next visit.

Physical Exam Findings and Functional Assessment

— Often normal between episodes — a normal exam does not exclude OA.

— During exacerbation: tachypnea, accessory muscle use, prolonged expiratory phase, audible wheeze, inability to speak full sentences.

— Diffuse, polyphonic expiratory wheeze; may be biphasic in severe obstruction.

— Silent chest = ominous, indicates severe airflow limitation — escalate immediately.

— Look for absence of focal findings (would suggest pneumonia, foreign body, or mass).

— Boggy, pale nasal turbinates and clear rhinorrhea — suggests allergic rhinitis often co-existing with HMW-sensitizer OA.

— Conjunctival injection — workplace irritant exposure.

— Eczema, urticaria, or contact dermatitis on hands/forearms — supports atopic phenotype and chemical exposure (latex, epoxy resins).

— Pulsus paradoxus >12 mmHg = severe attack.

— HR >120, RR >30, SpO₂ <92% on room air, PEF <50% predicted → severe.

— Rising PaCO₂ on ABG in a tachypneic asthmatic = impending respiratory failure (normally should be low due to hyperventilation).

— Office spirometry pre- and post-bronchodilator.

— Inspect hands for chemical staining, dermatitis.

— Document baseline weight, vitals, SpO₂ for longitudinal comparison.

General appearance:

Pulmonary exam:

Upper airway / ENT:

Skin:

Hemodynamic and severity assessment during acute presentation:

Functional/occupational assessment to perform in clinic:

Board pearl: A patient with new-onset wheeze who is afebrile, has clear lungs at the office visit, and normal CXR but whose PEF drops 20% during work shifts has OA until proven otherwise.

CCS pearl: In the acute severe attack, order continuous pulse oximetry, cardiac monitoring, PEF, and ABG; reassess every 15–30 minutes after bronchodilator therapy. Do not order CXR routinely unless fever, focal findings, or failure to improve.

Diagnostic Workup — Initial Labs, Imaging, and Spirometry

— Spirometry pre- and post-bronchodilator: obstruction (FEV1/FVC <0.70 or <LLN) with ≥12% AND ≥200 mL FEV1 improvement after albuterol = reversibility.

— If spirometry normal and suspicion high: methacholine challenge (PC20 <8 mg/mL = airway hyperresponsiveness). Negative methacholine has high NPV — essentially rules out current asthma.

— Serial peak expiratory flow (PEF) monitoring: 4 readings/day × ≥2 weeks at work and ≥2 weeks off work. ≥20% diurnal variability or work-related deterioration supports OA. Most practical first-line tool in primary care.

— Compare best, mean, and lowest PEF on work vs. off-work days.

— CBC: eosinophilia (>300/µL) supports atopic phenotype.

— Total IgE and specific IgE to suspected workplace antigens (flour, latex, animal dander) — useful for HMW agents; usually negative for LMW chemicals.

— Skin prick testing to occupational allergens if available.

— CXR: typically normal in OA; obtain to exclude alternatives (hypersensitivity pneumonitis, pneumonia, mass, COPD) — especially with crackles, fever, or weight loss.

— High-resolution CT only if HP or interstitial disease suspected.

Step 1 — Confirm asthma physiologically:

Step 2 — Establish work-relatedness (the OA-specific step):

Step 3 — Adjunctive labs:

Imaging:

ECG: not routinely required; consider if cardiac wheeze ("cardiac asthma") suspected in older patients.

Key distinction: Spirometry confirms asthma; PEF monitoring confirms work-relatedness. You need both for an OA diagnosis. A positive methacholine alone does not localize the cause to the workplace.

Step 3 management: Provide the patient a handheld PEF meter, diary card, and written instructions at the index visit; review at 4–6 weeks. Do not refer to pulmonology before serial PEF is in hand — it accelerates definitive workup.

Diagnostic Workup — Advanced and Confirmatory Studies

— Gold standard for OA diagnosis — controlled exposure to the suspected agent in a specialized lab with serial FEV1 measurements over 24 hours.

— Detects immediate (within minutes) and late (4–12 hour) bronchoconstriction.

— Indicated when diagnosis remains uncertain after PEF + immunologic testing, or when medicolegal stakes are high (disability, workers' comp dispute).

— Risks: severe bronchospasm — only at experienced centers.

— Serial FEV1 measured before, during, and after a work shift.

— Alternative when SIC unavailable; less standardized but practical.

— Methacholine challenge done at work and again after ≥2 weeks away.

— Improvement in PC20 off-work strongly supports sensitizer-induced OA.

— Sputum eosinophils (>1–2%) increase during work exposure in sensitizer OA — useful supportive evidence.

— Fractional exhaled nitric oxide (FeNO): rises with work exposure in Th2-driven OA; lower utility for LMW agents.

— Skin prick testing or specific IgE for HMW agents (latex, flour, animal proteins, enzymes) — strong PPV.

— LMW agents (isocyanates, anhydrides, persulfates) — IgE testing has poor sensitivity; SIC often required.

— Single high-level irritant exposure, symptoms <24 h, persistent hyperresponsiveness ≥3 months. No SIC needed — diagnosis is clinical.

Specific inhalation challenge (SIC):

Workplace challenge / supervised return-to-work testing:

Non-specific bronchial hyperresponsiveness:

Airway inflammation biomarkers:

Immunologic testing:

When to suspect RADS instead of sensitizer OA:

Board pearl: The combination of methacholine PC20, serial PEF, and specific IgE correctly classifies most OA cases without ever needing SIC.

Step 3 management: Refer to occupational medicine or pulmonology for SIC or workplace challenge when PEF + spirometry + immunology are inconclusive but suspicion remains high — and before the patient permanently leaves the job (post-removal SIC is less interpretable).

Risk Stratification and First-Line Management Logic

— 1. Complete cessation of exposure — best outcomes, especially if implemented within 6–12 months of symptom onset.

— 2. Substantial exposure reduction (engineering controls: ventilation, enclosure, substitution of agent; PPE — respirators) — second-best; persistent symptoms in ~50%.

— 3. Personal respiratory protection alone — least effective for sensitizer OA; may be acceptable for irritant-induced WEA.

— Intermittent, mild persistent, moderate persistent, severe persistent — based on daytime symptoms, nighttime awakenings, SABA use, FEV1, and exacerbations.

— Short symptom duration before removal (<1 year).

— Normal or near-normal FEV1 at diagnosis.

— Low degree of bronchial hyperresponsiveness.

— HMW-allergen sensitization (vs. LMW chemicals, which often cause persistent disease).

— Non-smoker.

— OA is a compensable occupational disease in all US states.

— PCP must provide written documentation linking diagnosis to workplace exposure.

— Patient retains right to job, retraining, and wage replacement during evaluation.

Core principle: Removal from exposure is the definitive treatment. Pharmacotherapy controls symptoms but does not reverse ongoing sensitization injury.

Management hierarchy (in order of preference):

Severity stratification (same as non-occupational asthma — GINA/NAEPP):

Prognostic factors favoring recovery after removal:

Key distinction: A patient with isocyanate-induced OA removed after 3 years of symptoms often has persistent asthma for life — counsel accordingly. A baker removed within 6 months of rhinitis/asthma onset may achieve complete remission.

Workers' compensation interaction:

Step 3 management: Once OA is confirmed, the definitive intervention is reassignment away from the agent, not escalating ICS dose. Initiate the workers' comp claim, notify employer (with consent), and engage occupational medicine for return-to-work planning.

Pharmacotherapy — First-Line Drug Regimen

— Step 1–2: As-needed low-dose budesonide-formoterol (or beclomethasone-formoterol).

— Step 3: Low-dose ICS-formoterol maintenance + as-needed ICS-formoterol.

— Step 4: Medium-dose ICS-formoterol maintenance + as-needed ICS-formoterol.

— Step 5: High-dose ICS-LABA + add-on (LAMA, biologic) + specialist referral.

— LAMA (tiotropium): step 4–5; reduces exacerbations.

— Leukotriene receptor antagonists (montelukast): modest benefit; FDA black-box warning for neuropsychiatric effects — counsel and document.

— Biologics (step 5): omalizumab (anti-IgE, allergic phenotype), mepolizumab/benralizumab/reslizumab (anti–IL-5, eosinophilic), dupilumab (anti–IL-4Rα), tezepelumab (anti-TSLP — broadest indication, including low-eosinophil disease).

— Albuterol nebulized or MDI with spacer, ipratropium for moderate-severe attacks.

— Systemic corticosteroids: prednisone 40–50 mg PO × 5–7 days; no taper needed for short courses.

— Magnesium sulfate IV for severe attacks not responding to standard therapy.

Same stepwise framework as general asthma (GINA 2024 / NAEPP 2020): controller + reliever therapy, escalated by control.

Preferred Track 1 (GINA): ICS-formoterol as both controller and reliever (MART/AIR):

NAEPP 2020 alternative: SMART (single maintenance and reliever therapy) with ICS-formoterol from step 3 upward.

Reliever-only SABA monotherapy is no longer recommended even for intermittent disease (GINA).

Add-on agents:

Acute exacerbation:

Board pearl: Pharmacotherapy in OA is identical to general asthma — the unique intervention is exposure cessation. Step 3 distractors will offer "escalate ICS dose" when the correct answer is "remove from workplace exposure."

Step 3 management: When initiating ICS-formoterol, demonstrate inhaler technique in clinic, prescribe a spacer, provide a written asthma action plan, and document teach-back.

Workplace Intervention and Expanded Non-Pharmacologic Management

— 1. Elimination/substitution — replace the sensitizer with a safer agent (e.g., powder-free, low-protein latex gloves; water-based for solvent paints). Most effective.

— 2. Engineering controls — local exhaust ventilation, enclosed processes, automated handling. Reduces ambient exposure for all workers.

— 3. Administrative controls — job rotation, scheduling, training.

— 4. PPE (respirators, gloves) — last resort; fit-testing required for tight-fit respirators (annual under OSHA).

— Limited role; some evidence for latex and animal-handler OA. Not first-line — exposure reduction primary.

— Smokers have worse OA outcomes and greater sensitization risk (especially with anhydrides, platinum salts).

— Offer varenicline, bupropion, or NRT + behavioral counseling at every visit.

— Annual influenza, pneumococcal (PCV20 or PCV15+PPSV23), COVID-19, RSV (age ≥60 with risk factors), Tdap per schedule.

— Treat allergic rhinitis (intranasal steroids), GERD, OSA, obesity — all worsen asthma control.

— Screen for vocal cord dysfunction, a common asthma mimic in workers.

— Written asthma action plan with green/yellow/red zones based on PEF % personal best.

— Inhaler technique re-demonstration at every visit (>70% of patients use inhalers incorrectly).

Exposure control hierarchy (OSHA-aligned):

Allergen immunotherapy:

Smoking cessation:

Vaccinations (preventive, board-favorite):

Comorbidity optimization:

Patient education:

Key distinction: Engineering controls protect the workforce; PPE protects the individual. OSHA mandates engineering controls be implemented before relying on PPE — a frequent board distractor.

Step 3 management: When a worker is diagnosed with OA, notify the employer's occupational health program (with patient consent), request industrial hygiene assessment, and document the OSHA 300 log entry — the employer's responsibility, but PCP triggers the cascade.

Special Populations — Elderly and Renal/Hepatic Impairment

— Coexisting COPD is common; OA and COPD frequently overlap (ACO — asthma-COPD overlap).

— Reduced perception of dyspnea — symptoms underreported; reliance on objective PEF/spirometry more important.

— Comorbid heart failure can produce wheeze ("cardiac asthma") — obtain BNP, echo if uncertain.

— ICS: safe; monitor for oral candidiasis (rinse mouth after use), skin thinning, cataracts/glaucoma with high doses, osteoporosis (DEXA if cumulative high-dose therapy).

— LABA/formoterol: generally safe; caution with tachyarrhythmias.

— LAMA (tiotropium): caution in narrow-angle glaucoma, urinary retention from BPH.

— Systemic corticosteroids: worsen hyperglycemia, hypertension, osteoporosis, cataracts — minimize courses.

— Theophylline: narrow therapeutic window, multiple drug interactions — generally avoided; if used, target level 5–15 mcg/mL.

— ICS, LABA, LAMA, leukotriene modifiers — no dose adjustment.

— Biologics (omalizumab, mepolizumab, etc.) — no renal adjustment needed.

— Avoid NSAIDs in those with AERD (aspirin-exacerbated respiratory disease) — relevant overlap with OA.

— Montelukast, zileuton — caution; zileuton requires LFT monitoring (hepatotoxicity).

— Theophylline metabolism reduced — dose-adjust and monitor levels.

— Prednisone clearance reduced in cirrhosis — use lowest effective dose.

— Beta-blockers (even cardioselective at high dose) can worsen asthma — review medication list.

— ACE inhibitors → cough, may confound asthma symptom assessment.

Older workers (≥65) — diagnostic challenges:

Pharmacologic considerations in the elderly:

Renal impairment:

Hepatic impairment:

Polypharmacy alert:

Board pearl: A 68-year-old former smoker with new wheeze and a workplace dust exposure may have OA, COPD, or both — distinguish with post-bronchodilator FEV1/FVC and serial PEF.

Step 3 management: In older workers with OA, balance fall risk, osteoporosis screening (DEXA), and cataract surveillance against ICS benefit; use lowest effective ICS dose and consider biologics earlier to spare steroids.

Special Populations — Pregnancy, Pediatrics, and Adolescents

— Asthma affects ~8% of pregnancies; uncontrolled asthma is more dangerous than medications.

— One-third worsen, one-third improve, one-third unchanged during pregnancy.

— Risks of uncontrolled asthma: preeclampsia, preterm birth, low birth weight, perinatal mortality.

— Safe in pregnancy: budesonide (preferred ICS — most data), albuterol, formoterol/salmeterol, montelukast, prednisone (use lowest dose; weigh cleft palate signal in first trimester vs. exacerbation risk).

— Avoid: live vaccines; zileuton (limited data).

— Continue controllers — do not stop ICS at pregnancy diagnosis.

— Strong indication to reassign away from sensitizer — fetal as well as maternal benefit.

— Document medical accommodation request; Pregnancy Discrimination Act and PWFA (Pregnant Workers Fairness Act, 2023) require reasonable accommodation.

— All standard asthma medications (ICS, LABA, LAMA, SABA, montelukast, prednisone) — compatible with breastfeeding.

— Apprentices in bakeries, hair salons, auto body shops, healthcare — high-risk first jobs.

— Screen at well visits: "What kind of work or training are you doing?"

— Pre-employment asthma history; pre-existing asthma is a risk factor for sensitization.

— True OA rare in children but parental occupation can bring agents home ("para-occupational" exposure — e.g., asbestos historically, beryllium, isocyanate dust on clothing).

— Counsel parents to change clothes/shower before contact with children.

Pregnancy:

Occupational exposure during pregnancy:

Lactation:

Adolescents entering workforce (16–18):

Pediatrics (general):

Key distinction: In pregnancy, uncontrolled asthma harms the fetus more than asthma medications do — a frequent board stem will offer "discontinue ICS due to pregnancy" as a wrong answer.

Step 3 management: For a pregnant worker with OA, coordinate with OB, occupational medicine, and HR for immediate reassignment; document the PWFA accommodation request in writing within the prenatal record.

Complications and Adverse Outcomes

— Status asthmaticus — refractory bronchospasm requiring ICU admission, possibly intubation.

— Pneumothorax, pneumomediastinum from high airway pressures.

— Hypoxic respiratory failure, hypercapnic respiratory failure (late, ominous).

— Cardiac arrest from severe hypoxia or acidosis.

— Airway remodeling — subepithelial fibrosis, smooth muscle hypertrophy, persistent obstruction even after removal from exposure.

— Fixed airflow obstruction — non-reversible FEV1 decline mimicking COPD.

— Persistent bronchial hyperresponsiveness — particularly with LMW agents (isocyanates).

— Anxiety, depression, PTSD — work-related illness has high psychiatric comorbidity.

— Loss of employment — up to 30% of OA patients are unemployed within 5 years of diagnosis.

— Income loss — even with workers' comp, replacement wages typically 60–67% of prior earnings.

— Job retraining barriers — older workers, those with limited education face the worst outcomes.

— Health insurance disruption — particularly when job-linked.

— High-dose ICS: adrenal suppression, osteoporosis, growth velocity reduction (pediatric).

— Frequent oral steroid courses (≥2/year): diabetes, hypertension, weight gain, cataracts, osteonecrosis.

— LABA monotherapy without ICS — black-box warning, increased asthma death.

— Asthma deaths in the US ~3,500/year; OA contributes disproportionately due to delayed diagnosis.

Acute complications:

Chronic complications of untreated OA:

Socioeconomic complications (Step 3 emphasis):

Medication-related complications:

Mortality:

Board pearl: Persistent bronchial hyperresponsiveness after removal from exposure is the single strongest predictor of long-term disability in OA — measured by methacholine PC20.

Step 3 management: At every OA visit, screen for depression (PHQ-9), financial strain, and oral steroid burden (≥2 courses/year = trigger biologic referral). Document exacerbation frequency, ED visits, and missed workdays in the longitudinal record.

When to Escalate Care — ICU, Consult, and Inpatient Triage

— PEF <50% predicted/personal best after initial SABA.

— SpO₂ <92% on room air.

— Inability to speak full sentences, RR >30, HR >120.

— Failure to respond to SABA within 60 minutes.

— Persistent PEF <70% after ED treatment.

— Ongoing requirement for nebulized SABA more frequent than q4h.

— History of near-fatal asthma, prior intubation, ICU admission.

— Poor home support, inability to monitor, recent oral steroid course.

— Altered mental status, exhaustion, silent chest.

— Rising or normal-trending PaCO₂ in tachypneic patient.

— Need for noninvasive or invasive mechanical ventilation.

— Hemodynamic instability or arrhythmia.

— Severe acidosis (pH <7.30) refractory to therapy.

— Use ketamine (bronchodilator properties) for induction.

— Avoid high tidal volumes; permit permissive hypercapnia (target plateau pressure <30 cm H₂O).

— Low respiratory rate, long expiratory time, monitor for auto-PEEP.

— Pulmonology / allergy-immunology: uncontrolled despite step 4 therapy; diagnostic uncertainty; biologic candidate; consideration of SIC.

— Occupational medicine: confirmed or suspected OA, workers' comp navigation, return-to-work planning.

— Industrial hygiene (via employer or state OSHA): workplace assessment.

Indications for ED referral from clinic:

Indications for hospital admission:

ICU admission criteria:

Intubation considerations:

Specialty consultation triggers:

CCS pearl: In a CCS asthma exacerbation case, order continuous SpO₂, cardiac monitoring, IV access, nebulized albuterol + ipratropium, IV/PO methylprednisolone, and ABG. Reassess PEF every 30–60 minutes; if no improvement after 1 hour or worsening, add IV magnesium sulfate 2 g and prepare for ICU transfer. Do not order chest CT or routine ABG repeatedly — wastes simulated time.

Step 3 management: Before any discharge from ED/inpatient, ensure oral steroid burst, ICS-formoterol prescription, action plan, PCP follow-up within 1–2 weeks, and trigger-avoidance counseling are all documented.

Key Differentials — Same-Category (Airway/Asthma-Spectrum) Causes

— Pre-existing asthma worsened by nonspecific workplace triggers (cold air, dust, exertion).

— Distinguish: asthma diagnosis predates the job; PEF improves off work but no new sensitization.

— Management: exposure reduction, optimize controller — complete removal usually not required.

— Single high-level irritant exposure → persistent asthma symptoms ≥3 months.

— No latency period, no immunologic sensitization.

— Diagnosis is clinical; no SIC needed.

— Inhaled organic antigens (moldy hay → farmer's lung; bird antigens → bird fancier's lung; metalworking fluids).

— Restrictive pattern on PFTs (not obstructive), reduced DLCO, ground-glass / centrilobular nodules on HRCT, lymphocytic BAL.

— Systemic symptoms (fever, weight loss) — distinguishes from OA.

— Cough without wheeze or airflow obstruction; sputum eosinophils elevated; normal spirometry, negative methacholine.

— Responds to ICS; can be occupational (latex, welding fumes).

— Asthma + nasal polyps + NSAID sensitivity.

— Distinct from OA but may coexist; ask about NSAID-induced wheeze.

— Difficult-to-control asthma + elevated IgE (>1000) + Aspergillus sensitization + central bronchiectasis.

— Symptoms 5–10 min after exertion; relevant in physically demanding occupations.

Work-exacerbated asthma (WEA):

Reactive Airways Dysfunction Syndrome (RADS):

Hypersensitivity pneumonitis (HP):

Eosinophilic bronchitis:

Aspirin-exacerbated respiratory disease (AERD / Samter's triad):

Allergic bronchopulmonary aspergillosis (ABPA):

Exercise-induced bronchoconstriction:

Key distinction: OA causes new sensitization; WEA worsens existing disease; RADS follows a single toxic exposure; HP causes restrictive lung disease. All four can present with work-related dyspnea — the PFT pattern + temporal exposure history distinguishes them.

Board pearl: A worker with fever, fatigue, weight loss, and crackles (not wheeze) after agricultural exposure does not have OA — think hypersensitivity pneumonitis and order HRCT + serum precipitins.

Key Differentials — Other-Category Causes

— Inspiratory stridor (not expiratory wheeze), throat tightness, sudden onset/offset.

— Often misdiagnosed as refractory asthma.

— Diagnosis: laryngoscopy during symptoms shows paradoxical adduction.

— Management: speech therapy, address triggers (anxiety, GERD, irritants).

— Older smokers; persistent obstruction, less reversibility, low DLCO.

— May coexist with OA (especially welders, miners).

— Chronic productive cough, recurrent infections, HRCT shows dilated airways.

— Wheeze from interstitial edema; orthopnea, PND, elevated JVP, BNP elevated.

— Common in older workers presenting with new dyspnea.

— Sudden dyspnea, pleuritic chest pain, hypoxia; consider in any new dyspnea — D-dimer, CTPA.

— Chronic cough, sour taste, worse supine; empiric PPI trial.

— Tracheal stenosis, mass, foreign body — fixed flow-volume loop pattern.

— Normal SpO₂, paresthesias, perioral numbness, no wheeze; tetany possible.

— Hilar adenopathy, restrictive PFTs, occasional endobronchial involvement causing wheeze.

— Asthma + peripheral eosinophilia + multisystem (skin, neuropathy, sinus disease) → consider EGPA, especially in patients on leukotriene modifiers with new vasculitic features.

Vocal cord dysfunction (VCD) / Inducible laryngeal obstruction:

COPD:

Bronchiectasis:

Heart failure ("cardiac asthma"):

Pulmonary embolism:

GERD-related cough/wheeze:

Upper airway obstruction:

Anxiety/hyperventilation syndrome:

Sarcoidosis:

Chronic eosinophilic pneumonia / EGPA (Churg-Strauss):

Key distinction: Inspiratory stridor or sudden-onset throat-tightness in a worker = VCD until proven otherwise; do not escalate ICS-LABA — escalate to laryngoscopy and speech therapy.

Board pearl: Refractory "asthma" with peripheral eosinophilia >10%, mononeuritis multiplex, and sinusitis = EGPA — order ANCA (MPO), eosinophil count, and biopsy; treat with high-dose steroids and consider mepolizumab.

Secondary Prevention, Discharge Medications, and Long-Term Plan

— Permanent removal from the causative agent for sensitizer OA.

— For RADS, avoid further high-level irritant exposures.

— For WEA, reduce exposure + optimize controller therapy.

— Controller: ICS-formoterol (budesonide-formoterol or beclomethasone-formoterol) — preferred per GINA.

— Reliever: as-needed ICS-formoterol (same inhaler in MART) or albuterol if on non-formoterol regimen.

— Oral corticosteroid burst: prednisone 40–50 mg × 5–7 days if recent exacerbation.

— Spacer device for MDIs.

— Written asthma action plan with green/yellow/red PEF zones.

— Annual influenza, COVID-19 boosters, pneumococcal series, Tdap, RSV (age ≥60 with risk).

— Allergic rhinitis (intranasal steroids, antihistamines).

— GERD (PPI trial, weight loss).

— OSA screening (STOP-BANG) — treat with CPAP.

— Obesity (counseling, GLP-1 agents if indicated).

— Tobacco cessation at every visit.

— Submit physician statement linking diagnosis to exposure.

— Coordinate with state workers' comp board.

— Vocational rehabilitation referral for retraining if reassignment impossible.

— Co-workers should be evaluated if a workplace OA cluster suspected — initiate via occupational medicine or OSHA referral.

— OA-related hospitalizations and ED visits are quality measures (HEDIS asthma medication ratio).

— Document controller-to-reliever ratio >0.5 — performance metric.

Definitive secondary prevention — exposure cessation:

Discharge medication bundle (after exacerbation or new diagnosis):

Vaccination updates at every visit:

Comorbidity management:

Workers' compensation and disability:

Family screening:

Health systems / value-based care:

Step 3 management: At the post-diagnosis visit, prescribe controller, action plan, spacer, vaccinations, and schedule occupational medicine consultation within 4 weeks for workplace exposure assessment and return-to-work planning.

Board pearl: Patients removed from exposure within 6–12 months of symptom onset have the best chance of complete remission — early diagnosis is the highest-yield preventive intervention.

Follow-Up, Monitoring Parameters, and Rehab/Counseling

— 2–6 weeks after diagnosis or medication change — assess symptoms, technique, adherence.

— Every 3 months once controlled — assess control (ACT score, exacerbations, SABA use).

— Annually at minimum — spirometry, vaccinations, comorbidities, medication review.

— After any exacerbation: 1–2 weeks post-ED/discharge.

— Asthma Control Test (ACT): ≥20 = well-controlled; <20 = poorly controlled — step up therapy.

— Spirometry annually (more often if uncontrolled); track FEV1 decline.

— PEF diary during workplace re-evaluation or return-to-work trials.

— Exacerbation log: OCS courses, ED visits, hospitalizations.

— Inhaler technique — re-demonstrate at every visit; >70% use inhalers wrong.

— Adherence — controller fill rates, medication possession ratio.

— Eosinophilic phenotype, high IgE, frequent OCS bursts → refer for biologic.

— Consider for patients with fixed obstruction, deconditioning, persistent dyspnea despite optimized medical therapy.

— Includes exercise training, education, breathing techniques.

— Avoidance of the causative agent — even brief re-exposure can trigger severe attacks in sensitized workers.

— Cross-reactivity awareness (e.g., latex sensitization → avoid certain foods: banana, kiwi, avocado).

— Tobacco cessation, weight management, exercise.

— Mental health screening (PHQ-9, GAD-7) — high comorbidity.

— Only after documented absence of exposure, objective improvement in PEF/methacholine, and occupational medicine clearance.

Follow-up cadence:

Monitoring parameters:

Biologic candidacy review (annually):

Pulmonary rehabilitation:

Counseling priorities:

Return-to-work evaluation:

CCS pearl: Sequence at the follow-up visit: (1) ACT score, (2) inhaler technique check, (3) adherence review, (4) spirometry if uncontrolled, (5) step adjustment, (6) update action plan, (7) vaccinations, (8) schedule next visit.

Board pearl: A patient using SABA >2 days/week (excluding pre-exercise prophylaxis) is not well-controlled — step up therapy regardless of PEF.

Ethical, Legal, and Patient Safety Considerations

— Most US states have occupational disease reporting laws — OA is reportable in many states (CA, NJ, MI, MA via SENSOR-Pesticides/OA programs).

— Reporting triggers public health investigation of the workplace; may identify co-workers at risk.

— OA is compensable; physician must document work-relatedness with reasonable medical certainty.

— Patient may face employer retaliation — illegal under OSHA Section 11(c) anti-retaliation provisions.

— Document objectively; avoid speculation in records.

— Workplace surveillance testing (spirometry, methacholine) — workers must consent; results should be discussed with worker before employer.

— Genetic testing for atopic predisposition — GINA (Genetic Information Nondiscrimination Act, 2008) prohibits employer use; counsel before testing.

— Diagnosis is protected health information — disclose to employer only with patient consent.

— Exception: imminent danger to others (e.g., a worker whose impairment endangers public safety — pilot, commercial driver) — may trigger reporting per state law and FMCSA/FAA rules.

— At hospital discharge after asthma exacerbation, omission of controller therapy is a leading cause of 30-day readmission. Verify ICS-formoterol is on the discharge med list, action plan provided, PCP follow-up scheduled within 1–2 weeks.

— Medication reconciliation at every transition — ED, hospital, PCP, occupational medicine.

— ADA (Americans with Disabilities Act) — asthma is a covered disability; employer must provide reasonable accommodation (reassignment, respirator, schedule modification).

— PWFA (2023) — pregnant workers with asthma entitled to accommodation.

— Company-employed occupational physicians have dual loyalty; the PCP serves as the patient's advocate in disputes.

Mandatory reporting and surveillance:

Workers' compensation:

Informed consent edge cases:

Confidentiality vs. disclosure:

Transition-of-care risk (Step 3 favorite):

Disability accommodation:

Conflict of interest:

Board pearl: A worker with confirmed OA who is fired after filing a workers' comp claim is a victim of illegal retaliation — direct to OSHA whistleblower complaint within 30 days.

Step 3 management: Always document work-relatedness, exposure agent, objective testing, and counseling on workers' comp rights in the chart — chart language is medicolegally protective for both patient and physician.

High-Yield Associations and Rapid-Fire Clinical Facts

— Bakers — wheat flour, alpha-amylase (HMW).

— Healthcare workers — latex (HMW), glutaraldehyde, methacrylates.

— Spray painters / auto body — isocyanates (TDI, MDI, HDI) — most common LMW cause.

— Hairdressers — persulfates (bleaching agents), henna.

— Farmers — grain dust, animal dander, mold.

— Woodworkers — western red cedar (plicatic acid), oak.

— Cleaners — quaternary ammonium, chloramines (bleach + ammonia mixing).

— Laboratory workers — animal proteins (rat urine).

— Electronics / soldering — colophony (pine resin flux).

— Pharmaceutical workers — psyllium, antibiotics (penicillins).

— HMW agents (>10 kDa proteins) → IgE-mediated, immediate response, positive skin prick.

— LMW agents (<5 kDa chemicals) → mixed/non-IgE, late response, often negative skin test.

— Isocyanates → conjugate with airway proteins (haptens) → T-cell-mediated.

— PC20 <8 mg/mL on methacholine = airway hyperresponsiveness.

— ≥20% diurnal PEF variation = supportive of asthma.

— FEV1 ≥12% AND 200 mL post-bronchodilator = reversibility.

— FeNO >50 ppb = eosinophilic inflammation, predicts ICS response.

— Up to 70% of OA patients have persistent symptoms despite removal.

— Best predictor of recovery: early diagnosis + complete removal.

— LMW agents (isocyanates) → worst prognosis.

— Black-box warning for LABA monotherapy (asthma deaths) and montelukast (neuropsychiatric).

— Tezepelumab — only biologic effective across all asthma phenotypes (low eos too).

Top sensitizers by occupation:

Pathophysiology pearls:

Test associations:

Prognostic facts:

Pharmacology rapid-fire:

Board pearl: "Late asthmatic response 4–12 hours after work shift" + "auto body shop" = isocyanate-induced OA — gold-standard diagnostic stem.

Board Question Stem Patterns

— A 34-year-old baker presents with cough, wheeze, and rhinitis for 8 months. Symptoms improve on vacation. Spirometry shows reversible obstruction. Next step? → Serial peak flow monitoring at work and off work (not "start ICS-LABA" or "refer for SIC immediately").

— Auto body worker develops cough and dyspnea 6 hours after end of shift; symptoms worsened over 2 years. Methacholine PC20 = 2 mg/mL. Best management? → Permanent removal from isocyanate exposure (not "respirator and continue work").

— Janitor mixed bleach and ammonia 4 months ago; persistent cough and wheeze ever since. Spirometry shows reversible obstruction. Diagnosis? → Reactive Airways Dysfunction Syndrome (no latency, single high-level irritant).

— A 28-year-old with childhood asthma starts a new job in a warehouse with cold air; symptoms increase. Diagnosis? → Work-exacerbated asthma, not OA — manage with exposure reduction + step-up therapy.

— 26-week-pregnant flour mill worker with worsening asthma. Best ICS? → Budesonide (most data in pregnancy); also reassign away from flour exposure.

— Farmer with fever, weight loss, crackles, restrictive PFTs, ground-glass on HRCT. → Not OA — this is HP (farmer's lung).

— Worker with inspiratory stridor, throat tightness, normal spirometry between attacks. → VCD; refer for laryngoscopy and speech therapy.

— Patient asks if employer must be notified. → Disclose only with patient consent; file workers' comp claim with patient's authorization; counsel on OSHA anti-retaliation protections.

Stem 1 — The classic temporal pattern:

Stem 2 — Isocyanate exposure with late response:

Stem 3 — RADS:

Stem 4 — Work-exacerbated vs. occupational asthma:

Stem 5 — Pregnancy:

Stem 6 — Hypersensitivity pneumonitis mimic:

Stem 7 — Vocal cord dysfunction:

Stem 8 — Workers' comp and ethics:

Step 3 management: The most common wrong answer across OA stems is "escalate inhaled corticosteroid dose." The correct answer for sensitizer OA is almost always "remove from exposure + maintain controller therapy."

Board pearl: When the stem mentions "symptoms improve on weekends/vacations" + adult-onset asthma + a specific occupation, the diagnosis is OA — the question is testing the next diagnostic step, usually serial PEF.

One-Line Recap

Occupational asthma is adult-onset asthma caused by workplace exposures, diagnosed by combining objective evidence of asthma (spirometry/methacholine) with documented work-relatedness (serial PEF, specific IgE, or specific inhalation challenge), and treated definitively by complete removal from the causative agent — pharmacotherapy alone is inadequate.

— Adult-onset asthma + work-related symptom pattern → spirometry + methacholine + serial PEF (2 weeks on, 2 weeks off work) + specific IgE; SIC if needed.

— Sensitizer-induced OA (latency, immunologic, requires complete removal).

— Irritant-induced OA / RADS (no latency, single high-level exposure, ≥3 months persistence).

— Work-exacerbated asthma (pre-existing asthma, nonspecific triggers, often manageable with exposure reduction).

— Complete cessation of exposure for sensitizer OA — earlier removal = better recovery.

— GINA-aligned ICS-formoterol (MART/AIR) as controller-reliever; oral steroid burst for exacerbations; biologics for severe phenotypes.

— Workers' compensation claim, OSHA notification, ADA/PWFA accommodation, occupational medicine referral.

— Annual spirometry, ACT score, inhaler technique, action plan updates, vaccinations.

— Screen for VCD, GERD, OSA, depression — common comorbidities.

— Counsel that LMW agents (isocyanates) often cause persistent disease even after removal; HMW agents diagnosed early have the best chance of full recovery.

Diagnosis algorithm:

Three categories to distinguish:

Definitive management:

Follow-up and prevention:

Board pearl: When a Step 3 stem describes new-onset adult asthma in a baker, painter, healthcare worker, or hairdresser with weekend improvement — serial peak flow is the next step, and removal from exposure is the definitive treatment. Always document work-relatedness and counsel on workers' compensation rights.