Asthma

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

Table of Contents

Asthma

Background

Diagnosis

Evaluation

Treatment

ASTHMA MEDICATIONS

EXACERBATIONS