PathophysiologyBronchial Asthma

& COPD

RVS Chaitanya Koppala

Asthma Common and chronic inflammatory condition of the airways, whose

cause is not completely understood

Common symptoms are

Hyper-responsive airways (coughing, wheezing, chest tightness and shortness of breath)

Broncho contriction

Asthma means laboured breathing refer to a disorder of the respiratory system that leads to episodic difficulty in breathing

Chronic disorder of the airways associated with variable airflow obstruction and an increase in the airway response to a variety of stimuli

Epidemiology

Exact prevalence of asthma remains uncertain because of differing ways in which airway restriction is reported

Diagnostic uncertainty (children under 2 yrs.) overlaps with chronic obstructive pulmonary disease (COPD)

Over 5 million people in UK , around 300 million worldwide

Mortality is estimated around 1400 deaths/yr

5-12% in children with a higher occurrence in boys than girls or parents have a allergic disorder

30-70% of children become symptom free by adulthood

COPD vs Asthma

In COPD, both the airways and lung parenchyma are affected by the disease and airflow limitation is progressive. COPD is predominantly diagnosed in patients >40 years old

&

In Asthma only the airways are affected. Asthma is usually present from childhood

Aetiology• Two main causes of symptoms are

Airway hyperresponsiveness (?)

Bronchoconstriction(?).

• Trigger factors is the allergen in faeces of the house dust mite (bedding carpets and soft furnishing.)

• Pollen from grass (seasonal asthma)

• Increased industrialization (occupational asthma)

• Drug induced asthma (Beta blocker drugs and prostaglandin synthetase inhibitors) ex: Aspirin and other NSAIDS (?)

Pathophysiology

Eosinophilic Non Eosinophilic

Extrinsic Asthma Intrinsic Asthma

Causative factor is allergen Causative factor is Virus

More common in children More common in Adults

Dust mite, IgE antibodies,

Rhinovirus (during first 3 yrs of life)

Non allergic factors, viral infection , irritants like

epithelial damage , mucosal inflammation,

emotional upset, parasympathetic input

Triggers activated Th2 lymphocytes and mast cells Triggers epithelial cell damage and Macrophages

Effected cells are eosinophil Effected cells are neutrophils

Causes airway inflammation Causes airway inflammation

Airway hyperesponsiveness, irritation, Oedema,

mucous plugging, remodeling

Airway hyperesponsiveness, irritation, Oedema,

mucous plugging, remodeling

Cellular mechanism involved in airways

Clinical manifestation

Persistant cough

Dyspnoea

Wheezing (a high pitched noise due to turbulent airflow/ narrowed airway)

Reversible airflow obstruction

Atopy

Allergic rhinitis

Acute severe asthma

Requires Hopitalization

Immediate emergency treatment

Bronchospasm (breathless at rest, cardiac stress)

Breathlessness Cannot talk or cannot lie down

Air trapped

Peak flow rate >100L/min

Air beneath mucosal inflammation

Pulse rate >110beats/min

Hyperexpansion of thoracic cavity

Lowering of diaphragm

Rapid breathing (>30 breath/min)

Lower oxygen saturation (SpO2 <92%)

Fatigued, cyanosed, confused, lethargic

Hypercapnia (High PaCO2 level)

Investigations

• Function of the lung can be measured to help diagnose and monitor various respiratory diseases

FEV (Forced Expiratory Volume)– spirometer (inhales deeply and exhales forcibly)

FVC (Forced Vital Capacity)– max volume of air exhaled with maximum capacity)

PEF (Peak Expiratory Flow)—the maximum flow rate that can be forced during expiration assess the improvement of deterioration and effectiveness of treatment.