shared:general:asthma
Table of Contents
Asthma
Background
- Definition: Chronic inflammatory disease of airways → episodes of airflow limitation → classic triad of sx (wheezing, cough, & dyspnea); over time can → airway remodeling (fibrosis, smooth muscle hypertrophy) → fixed obstructive component
- “Asthma-plus” syndromes: Atopy (asthma + allergic rhinitis + atopic dermatitis), Samter’s triad (asthma + ASA sensitivity + nasal polyps), Allergic Bronchopulmonary Aspergillosis (ABPA) (asthma + bronchiectasis+ allergic reaction to aspergillus), Churg–Strauss (asthma + eosinophilia + granulomatous vasculitis) (Lancet 2002;360:1313)
- Pathophysiology: Genetic (predisposition for IgE-mediated/Th2 response) & environmental factors (pollution, tobacco, allergens) → altered immune response → airway hyperresponsiveness, bronchoconstriction, ↑ edema/mucus → airflow obstruction
- Epidemiology: Affects ~8% of US adults, ♀ > ♂; African-American > Caucasian > Hispanic; onset in majority of pts occurs by age 40 y
- Risk factors: Atopy, smoking, obesity, occupational exposure (adult onset), dust mite exposure (childhood onset); rural upbringing protective (thought to be 2/2 ↑ diversity of microbial exposure) (NEJM 2013;369:549)
Diagnosis
- Hx/PE and spirometry used to diagnose and assess comorbidities, triggers and severity
- History: Classic sx: Intermittent episodes of dyspnea, chest tightness, wheezing, cough, frequently w/ identifiable triggers (below), often early-AM or nighttime coughing
- PMHx: Atopy (atopic dermatitis, allergic rhinitis), seasonal allergies, rhinitis/sinusitis, GERD, CHF, OSA, obesity, depression/anxiety, vocal cord dysfunction
- Meds: ASA/NSAIDs (use or hx sensitivity), βB, ACEI
- FHx: Asthma, atopy, other pulm diseases
- Social hx: Tobacco exposure, occupational & home exposures, incl pets
- Exam: Often unremarkable exam if not in acute exacerbation; HEENT (nasal polyps, allergic “shiners” or rhinitis), skin (atopic dermatitis), full chest & pulm exam
- Spirometry: Recommended in all pts in whom asthma is considered; documents obstruction (FEV1/FVC <70%) & its potential reversibility (FEV1 ↑ by 200 mL & 12% w/ bronchodilator); however, spirometry can be nl in mild disease btw episodes; pts may fail to show reversibility if asthma very poorly controlled; see “Pulmonary Function Tests”
- Labs: Not routinely indicated; if severe asthma, consider serum IgE, CBC w/ diff (↑eos), skin testing/RAST (typically by allergy/immunology specialist)
- Other: Methacholine challenge: Induced bronchospasm demonstrates airway hyperresponsiveness; occasionally used if PFTs nl and/or cough-variant asthma suspected; Se >90% (ARJCCM 2000;161:309), trial of empiric tx typically preferred; Sputum: >3% eosinophils has Se 86%, Curschmann spirals (mucous casts), Charcot–Leyden crystals (eosinophil lysophospholipase); CXR/advanced imaging if indicated by Ddx
- Differential diagnosis: COPD, PE, CHF, bronchiectasis, hypersensitivity pneumonitis, eosinophilic lung disease, tracheobronchomalacia, mechanical airway obstruction, (tumor), ABPA, med-induced cough (ACEI), vocal cord dysfunction (see “Hoarseness”)
Evaluation
- General approach: Patients w/ asthma should be assessed for symptom control, medication/tx adherence, and trigger exposure to determine management plan
- Asthma history: age of onset, exacerbations (PO steroids, ED, inpatient, intubation); recent poor control/hx intubation assoc w/ ↑ asthma mortality (Chest 2003;124:1880), peak flow
| Potential Asthma Triggers (cdc.gov/asthma/healthcare) | |
|---|---|
| Allergens | Persistent: Dust mites, cockroaches, pets, Seasonal (some regional variability): trees (spring), grass (summer), weed pollen (fall) |
| Occupational | Smoke, irritants, mold |
| Meds/toxins | Tobacco smoke exposure, outdoor air pollution, perfumes, ASA, NSAIDs, nonselective βB (though some controversy) |
| Infections | Viral upper respiratory infections |
| Other | Stress, cold air, strenuous physical activity, food additives (sulfites), hard laughing/crying |
Treatment
- Nonpharmacologic treatment: Indicated for all pts, multifaceted approach beneficial
- Allergen avoidance: Dust mites: Use bedding encasements, wash sheets weekly in hot water, avoid down, HEPA vacuum or air filter, no carpet in bedroom; pets: ↓ pet exposure (pet-free home or at least keep out of bedroom); eliminate mold/moist conditions when possible (↓ indoor humidity); Cockroach: Extermination, no exposed food or garbage; Pollens (indoors w/ windows closed during peak season); consultation with allergy specialist may be helpful
- Irritant avoidance: Avoid outdoor exercise during periods of ↓ air quality (airnow.gov/ offers US air quality forecasts), avoid exposure to wood stoves, tobacco smoke
- Smoking: Smoking & 2nd-hand smoke may ↓ response to asthma medication, ↓ lung function, & trigger exacerbations; counsel all pts & family members to quit (see “Tobacco Use”) & ask housemates to smoke outside (AJRCCM 2007;175:783)
- Immunizations: Influenza & pneumococcal vaccines recommended; see “Immunizations”
- Patient education: Key to trigger avoidance, effective inhaler use; see “Tip Sheets” at www.nhlbi.nih.gov/health/public/lung/asthma/asthma_tipsheets.pdf
- Asthma action plan: Pts & providers should establish an asthma action plan, using sx or peak flow: sample at www.nhlbi.nih.gov/health/public/lung/asthma/asthma_actplan.pdf
- Pharmacologic Treatment
- General Approach: Initial tx dictated by severity; subsequent tx dictated by degree of control; all pts should have “rescue” inhaler Rx; All other Rx’s are “controller”: effective in preventing/reducing sx over long-term, not useful in acute management of sx
- Initiating treatment: For pts not currently treated, determining which “step” to start on determined by severity assessment (below); pt category determined by most severe sx
- Continuing treatment: For pts currently treated, assess control (see above) and then step up, down, or maintain as indicated; pt & provider judgment of tx efficacy should be guide; if asthma not well controlled, assess inhaler adherence & technique before modifying tx
| Classification of Asthma Severity | ||||
|---|---|---|---|---|
| Persistent | ||||
| Intermittent | Mild | Mod | Severe | |
| Sx frequency | ≤2 d/wk | >2 d/wk | Daily | Daily |
| Nighttime awakenings | ≤2×/mo | 3–4×/mo | >1/wk | Nightly |
| SABA use for sx control | ≤2 d/wk | >2 d/wk | Daily | Several times/d |
| Interference w/ nl activity | None | Minor | Some | Extreme |
| Spirometry (% predicted) | Nl btw exacerbations | Nl btw exacerbations | FEV1: 60–80% pred; FEV1/FVC: ↓ | FEV1: <60% pred; FEV1/FVC: ↓ |
| Exacerbations | <1/y | ≥2/y | ≥2/y | ≥2/y |
| Initial Tx | Step 1 | Step 2 | Step 3 | Step 4 or 5 |
| Asthma Treatment Steps | |
|---|---|
| Step | Controller Medication |
| Step 1 | None indicated (should receive SABA PRN) |
| Step 2 | Low-dose ICS, consider allergen immunotherapy Alt: Antileukotriene, theophylline, cromolyn |
| Step 3 | Low-dose ICS & LABA Alt: Medium-dose ICS, low-dose ICS + (LTRA, theophylline, or zileuton); consider adjunct tiotropium, allergen immunotherapy |
| Step 4 | Med-dose ICS & LABA, specialist referral Alt: Med-dose ICS & (LTRA, theophylline, or zileuton); consider adjunct tiotropium, allergen immunotherapy |
| Steps 5, 6 | High-dose ICS + LABA ± oral corticosteroids, specialist referral, consider anti-IgE therapy or anti-IL5 therapy if appropriate phenotype |
| Features of Well-Controlled Asthma | |
|---|---|
| No limitation of activities No nocturnal sx/awakenings Validated survey indicating control (see above) | PEF or FEV1 nl Reliever/rescue tx ≤2 d/wk Daytime sx ≤2 d/wk |
| Treatment Plan by Level of Control | |
|---|---|
| Well-controlled: All control criteria met or n/a | <3 mo: maintain regimen; ≥3 mo: consider step-down reassess in 1-6 mo |
| Partially controlled: 1–2 of the listed criteria not met | Step-up 1 step Reassess in 2–6 wk |
| Poorly controlled: ≥3 of the listed criteria not met | Step-up 1–2 steps: Consider short course PO corticosteroids (40–60 mg QD × 3–10 d) Reassess in 2 wk |
- When to Refer
- Patients with “asthma-plus” syndromes; pts w/ mod–severe asthma or poorly controlled/frequent exacerbations despite escalation of Rx; dx uncertain, prior hospitalization for asthma → specialist (pulm or allergy/immunology)
- Patients with /prominent allergic component → allergy/immunology for allergy testing, consideration of allergen immunotherapy
ASTHMA MEDICATIONS
- Inhalers: Multiple devices (below); pt education key, as many use inhalers incorrectly (AJRCCM 1994;150:1256); inhaler how-to videos at cdc.gov/asthma/inhaler_video/default.htm
| Inhaled Medication Delivery Systems (nhlbi.nih.gov) | |
|---|---|
| Metered-dose inhaler (MDI) | Aerosolized Rx; must be “primed” (discarded sprays) before 1st use; requires coordination of actuation & breath Deep slow breath × 3–5 s, then hold × 10 s; repeat after 1 min if dose is “2 puffs” |
| Spacer | Used w/ MDI; turns aerosol into finer droplets for ↑ delivery to lungs; ineffective if pt exhales into spacer; requires separate Rx |
| Valved holding chamber (VHC) | Similar to spacer but prevents pt exhaling into device, may be more expensive; requires Rx |
| Dry powder inhaler (DPI) | Powdered Rx drawn into lungs w/ inhalation; can clump w/ ↑ humidity; use fast, deep breath & hold for 10 s |
| Nebulizer | Requires nebulizer machine to deliver Rx; no more effective at Rx delivery, but does not require pt effort/coordination |
EXACERBATIONS
- Definition: Acute onset/worsening of asthma symptoms (AFP 2011;84:40)
- Presentation: hx: Cough, wheeze, chest tightness, some limitation of activity; Exam: ↑ work of breathing on exam, wheezing, tachypnea; Peak flow: <80% (<40% consistent w/ severe exacerbation)
- Red flags: Severe SOB, failure for peak flow to improve after quick-acting rx used, sx not improving 24 h after step-up → severe exacerbation → ED
- Management of mild–mod exacerbation: (Some limitation of activity, peak flow 50–80% personal best): SABA 2–6 puff (or neb) now then Q2–4h PRN; step-up to next level of care; low threshold for short-course oral corticosteroids (40–60 mg prednisone QD × 3–10 d), esp if sx fail to improve w/ initial rescue Rx
shared/general/asthma.txt · Last modified: 2019/12/05 04:08 by 127.0.0.1