Asthma Clinical Practice Guideline Review Division of Population Health Revised June 2010.
Asthma 2010
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Transcript of Asthma 2010
Asthma DefinitionReactive airway diseaseChronic inflammatory lung disease
Inflammation causes varying degrees of obstruction in the airways
Asthma is reversible in early stages
Asthma
Affects approx 15% of New Zealanders which equates to 1 in 6 of the population
Incidence in New Zealand is increasingAsthma hospitalization rates have
markedly increasedPrevalence is higher in Maori & Pacific
Island adults with hospital admissions twice as likely for Maori than non-Maori adults
Asthma
High morbidity due to:1. Underdiagnosis and inappropriate therapy2. Limited access to healthcare3. Inaccurate assessment of severity4. Delay in seeking help5. Inadequate medical treatment6. Nonadherence to prescribed therapy7. Increase in allergens in the environment
TriggersPollensDustDust mitesFood colouringMoulds/fungiAnimalsFeathersJob-related factorsCold/flu viruses
Stress, emotionsChange of weatherChange of seasonSmokeCold airMedicinesFumesExercise
AsthmaPathophysiologyEarly-Phase ResponseEarly-Phase Response
Triggered when IgE receptors on mast cells beneath the bronchial wall are activated
Release inflammatory mediators (histamine, bradykinin, leukotriene, prostaglandins, chemotactic factors, and cytokines)
Mediators cause• bronchial smooth muscle constriction• increased vasodilation and permeability• epithelial damage
AsthmaPathophysiology
Early-Phase ResponseEarly-Phase Response Bronchospasm,increased mucous secretion, oedema formation, and increased amounts of tenacious sputum
Patient experiences wheezing, cough, chest tightness, and dyspnoea
Peaks within 30-60mins of exposure to trigger & subsides in another 30-90mins
Factors Causing Expiratory Obstruction in Asthma
1. Reduction in airway diameter
2. ↑ in airway resistance related to mucosal inflammation
3. Constriction of bronchial smooth muscle
4. Excess production of mucous
Fig. 28--3
Late-Phase ResponsePeaks in 5 – 6 hrsInfiltration with eosinophils & neutrophilsInflammation as more inflammatory
mediators producedBronchial reactivityMore severe than early-phase response & can
last 24 hrs or more
Early and Late Phases of Responses of Asthma
Fig. 28--1
AsthmaClinical ManifestationsUnpredictable and variableRecurrent episodes of:wheezing breathlessness coughtight chestExpiration may be prolonged from an
inspiration-expiration ratio of 1:2 to 1:3 or 1:4Between attacks may be asymptomatic with
normal or near-normal lung function
AsthmaClinical ManifestationsWheezing is an unreliable sign to gauge
severity of attackSevere attacks can have no audible wheezing
due to reduction in airflow“Silent chest” is ominous sign of impending
respiratory failure
AsthmaClinical Manifestations
Difficulty with air movement can create a feeling of suffocationPatient may feel increasingly anxiousMobilizing secretions may become difficult
AsthmaClinical Manifestations Examination of the patient during an acute Examination of the patient during an acute
attack usually reveals signs of hypoxaemiaattack usually reveals signs of hypoxaemiaRestlessnessIncreased anxietyInappropriate behaviorIncreased pulse and blood pressure
Features of Acute Severe AsthmaUnable to complete a sentence in 1 breathRR > 25 breaths per minPulse rate > 110 beats per minPERF (peak expiratory flow rate) <50%
predicted normal value or pt’s best-known value
Life Threatening FeaturesPERF <33% of predicted normal value or pt’s
best known valueSilent chest – absence of wheezeDiminished respiratory effortBradycardiaHypotensionExhaustionConfusion & agitation due to hypoxiaSigns of hypercarbia (sweating, red florid
complexion, bounding pulse, peripheral tremorsComa