Asthma and COPD Flashcards by Charles Pryce

Summarize the pathophysiological mechanisms in asthma

Reversible airflow obstruction due to constriction of smooth muscle in the airways
Bronchial wall inflammation leading to mucus hypersecretion and plugging

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List common acute asthma precipitants

Viral infection
Allergen (dust/pets/pollution/cigarette smoke)
Exercise
Emotional stress
Cold temperature
Night time

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Define airflow obstruction in the small airways

Airflow obstruction is defined as a FEV1/FVC (measured with spirometry) of <70 %.

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What constitutes ‘reversibility’ in bronchodilator response tests for asthma

Post-bronchodilator (10 mins) FEV1 increases more than 200 mL and the increase is greater than 12%.

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Classify asthma severity based on % predicted PEFR

Life threatening asthma <33 %
Acute severe asthma 33-50 %
Moderate asthma >50-75 %
Mild asthma >75 %

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Define ‘control’ of asthma

No day time symptoms
No night time awakening due to asthma
No exacerbations
No need for rescue treatment
No limitations to activity

There may have to be compromise between side effects of treatment and control of symptoms

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Describe the step-wise approach to asthma management

Step 1: Salbutamol

Step 2: Salbutamol + Budesonide

Step 3: Salbutamol + Budesonide + Salmeterol (or increased dose of steroid inhaler)

Step 4: As step 3 but trial of high dose inhaled steroid. Consider 4th drug e.g. leukotriene receptor antagonist

Step 5: As step 4 but regular oral steroids at lowest possible dose. Specialist care required

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List three different types of inhalers

pressurized meter dose inhaler (pmdi),
breath activated inhalers
dry powder inhalers

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How do spacers improve drug delivery

Remove the need for coordination between activation and inhalation

Reduce the velocity of aerosol and subsequent impaction on oropharynx.

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What particle size of nebulized solution is appropriate for the treatment of asthma

A drug particle size of 1-5 microns

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Should NSAIDS be excluded in all asthmatics

Only 10 % of asthmatics get bronchoconstriction secondary to NSAIDs, therefore it is unnecessary to exclude this useful group of analgesics in all asthmatics.

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What are the criteria that define severe asthma

Severe asthma consists of one or more of the following:

Previous near fatal asthma e.g. requiring ventilation
Previous admission for asthma within the previous year
Requires >3 classes of asthma medication
Heavy use of beta-2 agonist
Repeated attendances at A&E

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Which commonly used anaesthetic drugs cause histamine release

Morphine (give it slowly
SUX
Thiopental
Mivacurium

Avoid in brittle asthmatics

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What is the appearance of the capnograph tracing in asthmatics and why

Up-sloping of the plateau (shark fin like) –> indicates alveoli emptying at different rates.

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The expiratory time might need to be prolonged in asthmatics –> what impact does this have on other ventilatory parameters

Decreased inspiratory time –> increased inspiratory pressures

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Summarize an approach to laryngospasm, bronchospasm, poor ventilatory effort and pneumothorax

LARYNGOSPASM

Dx - RDS/Stridor/tug/accessory muscles/paradoxical breathing
Rx - Jaw thrust 100% O2 –> CPAP –> Re-intubation

BRONCHOSPASM
Dx - Expiratory wheeze and prolonged expiration
Rx - FiO2 1.0 and BDs

POOR VENTILATORY EFFORT
Dx - Residual sedation/opioids/incomplete recovery from NMB
Rx - BVM with FiO2 1.0 may need re-intubation
(re-sedate in the instance of residual NMB)

PNEUMOTHORAX
Rx - ICD

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How is intra-operative bronchospasm diagnosed

Increased airway pressures with difficulty ventilating and upsloping of the capnograph trace ± desaturation

Expiratory wheeze on auscultation

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How is intraoperative bronschospasm managed

IMMEDIATE
FiO2 1.0 and call for help
Exclude circuit malfunction/obstruction
Increase [volatile]
High Paw may be needed with I:E 1:4
Consider disconnection to relieve accumulation of autoPEEP
Change LMA to ETT if high pressures required (Aintree fibre-optic).
Drugs:
- B2 agonist puffed into circuit via adaptor or 2.5 - 5 mg salbutamol nebulized into circuit
- If equipment not available: Salbutamol 0.25 mg IV slow IV bolus

SHORT TERM
Aminophylline: 5mg/kg IV over 20 mins
(If on regular aminophylline: 0.5mg/kg/hr)
Hydrocortisone: 100mg IV
Magnesium Sulfate: 2 g in 200 ml over 20 mins
Adrenalin 10ug boluses IV
Ketamine 2mg/kg IV
ABG/CXR

DEFINITIVE
If refractory use IV infusion –> ICU

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Define COPD

Chronic obstructive pulmonary disease is characterized by a progressive development of airflow limitation that is not fully reversible. Clinically, it encompasses:

Chronic bronchitis ‏
Emphysema
Mucous plugging

What is chronic bronchitis

Presence of productive cough for >3 months for >2 consecutive years.

What is chronic bronchitis

Enlargement of air spaces, destruction of lung parenchyma, loss of lung elasticity and closure of small airways.

What is mucous plugging

Due to bronchial hypersecretion, tenacious secretions and ciliary dysfunction.

List the risk factors for the development of COPD

Cigarette smoking
Climate and air pollution
Occupational exposure: Grain/coal/mineral dust/welding fumes
Alpha 1 - antitrypsin deficiency

What differences are there between asthma and COPD?

Entity - COPD - Asthma
Age - > 35 - Any age
Cough - Persistent + Productive - Intermittent and dry
Smoking - Almost invariable - Possible
Breathlessness - Progressive and persistent - Intermittent and variable
Nocturnal Sx - Uncommon - Common
Family Hx - Uncommon - common
Atopy - Possible - common

What is the purpose of prn reliever inhalers in COPD

Improve exercise tolerance and relieve dyspnoea

When are long acting beta agonists indicated in COPD

If patients remain symptomatic despite prn reliever inhalers a long acting inhaled beta agonist or anticholinergic is added

Describe two different methods of inhaler delivery

Metered-dose inhaler (usually with spacer) | Breath-activated inhaler

What and when are oral medications prescribed

Oral steroids used for acute exacerbations Severe uncontrolled COPD might warrant maintenance steroids Oral theophylline is used for more severe COPD Mucolytics in chronic bronchitis

When are home nebulizers prescribed

For patients with disabling breathlessness and whose disease is uncontrolled on inhalers

What are the benefits of home oxygen

1. Improve survival 2. Reduce incidence of polycythaemia 3. Reduce progression of pulmonary hypertension 4. Improve neuropsychological health

How is home oxygen prescribed

Continuous therapy with O2 concentrator > 15 hours/day Intermittent therapy for short bursts using O2 cylinders

Who is prescribed home O2 therapy

Marked breathlessness at rest with PaO2 < 7.3 kPa

List the non-pharmacological management of patient's with COPD

1. Smoking cessation 2. Pulmonary rehabilitation - exercise - nutritional 3. Immunization - Pneumococcus and influenza 4. Surgery - bullectomy and lung volume reduction surgery in patients with emphysema

List the benefits of smoking cessation

1. Improvement of oxygen carrying capacity due to decrease in COHb (12 - 18 hours) 2. Return to normal hepatic enzyme function (6 - 8 weeks) 3. Return to normal immune function (6 - 8 weeks) 4. Improvement of ciliary and airway function and decreased sputum production

What should be considered in the perioperative period if the patient is on maintenance steroid therapy (>10mg daily)

Perioperative steroid replacement - IV hydrocortisone Ensure usual prednisone is taken and that regular dosing in the postoperative period

What surgical factors might increase the risk of pulmonary complications

1. The closer the incision is to the diaphragm --> hypoventilation and pulmonary complications (greatest risk for thoracic and upper abdominal surgery) 2. Postoperative pulmonary complications are lower for laparoscopic versus open surgery 3. Increased risk with increased surgical durations

What are the advantages of regional anaesthesia in COPD

Allows maintenance of spontaneous ventilation without irritation of airway Opioid sparing effect May facilitate early mobilization

What are the disadvantages of regional anaesthesia in COPD

Patient preference: - Can patient lie flat and still for duration of surgery Is sedation required to facilitate regional technique --> respiratory depression Neuraxial blocks - Sensory level of T6 may compromise intercostal muscle function: reduce coughing efficacy Pneumothorax risk with supraclavicular approaches to the brachial plexus and interscalene approach to the phrenic nerve

What are the advantages of GA in COPD

1. Control of ventilation and ETCO2 2. May be necessary for certain types of surgery 3. ETT - definitive airway and allows for suction of secretions 4. May be required to maintain oxygenation in the face of respiratory depression

What are the disadvantages of GA in COPD

Changes in functional lung volumes --> compromise postoperative resp function in patients with reduced respiratory reserve Bronchospasm risk from airway instrumentation and histamine releasing drugs Risk of barotrauma and pneumothorax from IPPV/PEEP/Air trapping Need to avoid N2O in bullous emphysema due to the risk of rupturing a bullae

Why is vascular access a challenge in patients on long term steroids

Fragile skin and vessel walls

How should drug choices be guided in COPD

``` Avoid drugs that cause histamine release Morphine Mivacurium SUX Thiopental ```

How are important lung capacities affected by anaesthesia and surgery

Vital capacity and functional residual capacity are reduced subsequent to the effects of anaesthetic drugs, neuromuscular blocking agents and surgical trauma

What measures are available to help preserve respiratory function and oxygentation

Lung expansion manoeuvres (teach prior to surgery) - sitting - deep breathing - Incentive spirometry (inhalation) - positive pressure breathing techniques (exhalation) Chest physiotherapy‏ Humidified Oxygen therapy, CPAP, nebs, analgesia/RA, (coughing and deep breathing)

How is the need for perioperative steroid replacement assessed

Depends on the dose of long term steroids (>10 mg prednisolone) Depends on whether surgery is minor, intermediate or major

Can histamine antagonists reduce the effects of histamine releasing drugs in patients with COPD