Asthma
Definition – a syndrome of intermittent reversible airway obstruction.
Pathophysiology – A medium airway disease with 3 major contributors: 1) mucosal inflammation with increased TH2 lymphocytes, eosinophils, mast cells and mucus production, 2) bronchial hyper-reactivity to allergens/irritants, and 3) smooth muscle contraction. Chronic, poorly controlled asthma leads to airway remodeling with hyperplasia of smooth muscle and mucosal glands as well as submucosal fibrosis and eventually produces irreversible obstruction.
Epidemiology – Prevalence in US and Europe: 5-10%. Prevalence in SSA: 3-5%. Prevalence in SSA is increasing, especially in higher socio-economic classes and cities. Prevalence is higher in pre-pubertal children (especially boys). Over 40yo, prevalence is higher in females. Family history is present in 30% of cases.
Subtypes –
- Childhood Asthma – most cases present between 1-10 years of age and 50% resolve by the end of puberty.
- Atopic Asthma – a genetic predisposition associated with eczema or seasonal allergic rhinitis.
- Adult Onset Asthma – starts after puberty. Likely to persist for life.
- Occupational Asthma – associated with occupational exposure. Common exposures include flour dust, animal allergens, platinum salts, kerosene, and ammonia. Often symptoms only improve during long vacations (> 2 weeks). Avoidance is essential but symptoms may not resolve for 2-3 years.
- Exercise-induced Asthma – symptoms only present with exercise. Pretreatment with beta-agonist is recommended. Dx: PFR drops by 20% with exercise.
- Cough Predominant Asthma – cough is predominant or only symptom.
- Aspirin-sensitive Asthma – Asthma symptoms and nasal congestion worsen one hour after aspirin ingestion. Often associated with nasal polyps. Treatment is avoidance of all NSAIDs
Symptoms – Asthma should be considered in any patient with chronic, intermittent cough, dyspnea, chest tighness or wheeze. The cough is typically paroxysmal, productive of scan sputum and worse at night. The dyspnea is often described as chest or throat tightness with air hunger. All symptoms of asthma are generally worse at night because of the diurnal variation of smooth airway contraction in the airways.
Signs –During acute asthma exacerbations, observation often reveals tachypnea with increased work of breathing (grunting, nasal flaring, and/or subcostal/supraclavicular retractions). Patients often appear anxious. Palpation and percussion are usually normal although the chest can be hyperresonant. On ascultation, diffuse expiratory wheezes with an increased expiratory time are often heard. In very severe asthma, there may be poor air movement and no detectable wheeze. Atelectasis often causes decreased breath sounds in the bases. Barrel chest may be present in chronic asthma. Physical examination often normal between episodes.
Differential Diagnosis (for wheezing) – asthma, atypical pneumonia (if fever), PCP (if HIV positive), pulmonary edema (if history/exam consistent with CCF), COPD (if smoker, obstruction not reversible), PE (if risk factors for DVT), tuberculosis (if symptoms are chronic and fever, night sweats or wt loss), or helminth infection with migration of larvae through the lungs (like strongyloidiasis).
Investigations –
- Oxygen saturation – <93% indicates hypoxia.
- Peak flow rate (PFR) – ideally should be compared to patient’s personal best measured at time when patient is asymptomatic. If personal best is not known PFR should be compared to predicted PFR by age and weight. If > 80% obstruction is minimal, if 50-80% obstruction is moderate, if < 50% obstruction is severe. In asthma, PFR should improve by 15% after dose of beta agonist.
- CXR – typically will show hyperexpansion with flattening of the diaphragms and clear lungs. Streaky atelectasis often also present.
- CBC
- HIV test
- Sputum for culture and sensitivity – if fever and sputum.
- Sputum for AFB x 3 – if productive cough > 2wk with fever, night sweats or wt loss.
Treatment –
- Inpatient - All patients with severe or life-threatening asthma should be admitted to the hospital. In severe asthma patients will be unable to speak in full sentences, RR>25, HR>105, PFR<50% predicted. In life-threatening asthma patients will have silent chest, cyanosis, bradycardia, hypotension, feeble respiratory effort or confusions and these patients should be admitted to the ICU.
The following should be given immediately:
- Oxygen (4-10L/min)
- Salbutamol 2 puffs every hour (or 5mg via nebulizer or spacer, if available)
- Prednisolone 60mg PO OD x 5/7 or
- If unable to take PO, hydrocortisone 200mg IV Q6H
- No sedatives!
If pt still has symptoms of severe asthma:
- Amophylline 250mg IV over 20 minutes then 1g over 24 hours.
- Consider Magnesium 2gm IV stat.
- Consider intubation but only if all other treatment has failed.
Outpatient – The goal of outpatient management is to prevent exacerbations and airway remodeling. In all patients with asthma. In all patients, identify trigger(s) and teach patient to avoid the trigger! Common triggers include allergens, viral infections, exercise, cold, emotion, smoke. Encourage smoking cessation or abstinence as smoking worsens all forms of asthma. Encourage exercise.
The following medications should be used:
- Salbutamol 2 puffs (100ug each) as needed for symptoms
- Pt must be educated on how to correctly use inhaler!
- Inhaled corticosteroid, increase dose until patient has symptoms < 2x/wk (“step up”). Start at 200mcg/day for children and 400mcg/day for adults and increase to maximum of 800mcg/day. Most asthma can be controlled with inhaled corticosteroids alone if used correctly.
- If still having symptoms >2x/wk at maximum dose of inhaled corticosteroid, add salmeterol or theophylline BD
- If still having symptoms > 2x/wk, add low dose oral steroids
- Once patient’s symptoms have been well controlled for 6 months, reduce medications to minimum necessary for symptoms < 2x/wk (“step down”)
Asthma Clinical Cases
Case 1
You are called to H2 to review a 35yo female with known asthma who presents with 2 days of cough, progressively worsening dyspnea and low-grade fevers. She was in her usual state of health until 2 days ago when she developed a nonproductive cough and low-grade fever. The symptoms worsened overnight and yesterday she became increasingly dyspneic with chest tightness. This morning the dyspnea was even worse and she came BMC.
ROS: No night sweats, weight loss. There is no blood in the sputum. No abdominal pain, vomiting or diarrhea. No swelling of the legs.
Past Medical History: She was diagnosed with asthma 10 years ago and has had 3 prior admissions to BMC for this condition including one admission to the ICU when she required intubation.
What is the definition of asthma? As above.
What is the pathophysiology of asthma? As above.
What do you think about when this patient developed asthma? Does this change her prognosis? Pt has adult onset asthma. Likelihood of spontaneous remission is very low. Discuss differences between childhood and adult onset asthma.
Medications: None
What will you ask about on family history? Ask for family history of asthma, eczema and allergies. These are “atopic” conditions and often inherited together. Discuss atopic asthma.
Family History: There is no family history of asthma, eczema or allergies.
What do you want to ask about on social history? Smoking. Smoking cessation is very important for asthmatics. Also occupational history to rule out possibility of occupational asthma. Occupational asthma usually associated with working in mines, working closely with animals, cotton or working with chemicals. Discuss other types of asthma.
Social History: The patient denies any smoking or drinking alcohol. She is a peasant and lives with her husband and 3 children who are all well. She does not work outside of the home. No known TB contacts.
What do you expect to find on examination in this patient with asthma? As above.
Exam: T 38.6C, BP 110/65, HR 120, RR 42, Oxygen Saturation 89%
The patient is alert but dyspneic and is unable to complete a full sentence.
There is no thrush, pallor or lower extremity edema.
CV: Tachycardic but regular with no murmur. No JVD.
Pulm: By inspection, severely tachypneic with subcostal/supraclavicular retractions and nasal flaring. Percussion note is resonant bilaterally. By auscultation there are expiratory wheezes throughout the lung with poor air movement and an increased expiratory time.
Abd: Nontender and nondistended with no hepatosplenomegaly.
The rest of the examination is unremarkable.
How would you grade this patient’s asthma? What is the appropriate disposition of the patient? Severe asthma as severely tachypneic and cannot complete full sentences. Admit to ward. Review grades of asthma.
What other simple test could you perform to confirm the diagnosis of asthma and determine the severity? Discuss spirometry, PEFR and show peak flow meter.
The patient’s Peak Expiratory Flow Rate (PEFR or PFR) is 40% of predicted.
What is your impression? Be specific and describe severity. Adult onset asthma, severe.
Name 3 differentials that you would consider in this case. Not all that wheezes is asthma.” Pulmonary edema (cardiac asthma), obstruction (foreign body, mass), disseminated strongyloidiasis, PCP (HIV), PE
Name 3 investigations that you would order urgently. O2 saturation, PFR, CXR, Rapid Test, FBP
What would you expect to see on CXR in this patient? Hyperexpanded lungs, flattened diaphragms.
CXR reveals hyperexpanded lungs (8 anterior ribs visible), flattened diaphragms and an infiltrate in the left lower lobe.
What is the most likely trigger of this patient’s asthma attack? Pneumonia. Review common triggers and importance of identifying and avoiding them.
How are you going to treat this patient? Antibiotics (Ceftriaxone 1gm OD) + treatments as listed above for acute asthma.
The patient improves. What medications will you discharge this patient home on? See above. Introduce concept of controller meds and how/why we use them.
What counseling will you give before discharge? Avoid triggers, don’t smoke, you need to take medications every day no matter how you feel.
You see the patient back in clinic 2 weeks later. How do you know if your controller meds are working? If symptoms (and using inhaler) < 2/wk then asthma is well controlled. If not, need to titrate up controller meds.
