14. Respiratory Disease

Question 1

FEV1/FVC

Answer 1

Represents the proportion of vital capacity that is expired in the first second of forced expiration (normal value 80%)

Question 2

Define Asthma

Answer 2

Asthma is a chronic obstructive disease with bronchiolar inflammation and hyperresponsiveness that displays reversible, variable, and recurrent airway obstruction

Question 3

Obstructive lung diseases

Answer 3

Asthma, COPD, cystic fibrosis

Question 4

Restrictive parenchymal lung diseases

Answer 4

Pulmonary fibrosis, sarcoidosis, radiation-induced interstitial lung disease

Question 5

Restrictive extraparenchymal lung diseases

Answer 5

Myasthenia gravis, diaphragm paralysis, muscular dystrophy, obesity, kyphoscoliosis

Question 6

What is status asthmaticus

Answer 6

Bronchospasmic episode that does not respond to treatment and is considered life threatening

Question 7

Treatment of status asthmaticus

Answer 7

• Supplemental O2 to maintain SaO2 of >90%
• B2-agonists by metered dose inhaler every 15-20 mins
• IV corticosteroids
• IV magnesium sulfate
• Epinephrine 0.3mg 1:1000 administered subcutaneously
• Tracheal intubation for PaCO2 >50 mm Hg

Question 8

Classification of asthma

Answer 8

Mild intermittent (<2 symptoms per week, FEV >80%)
Mild persistent (>2 symptoms per week, FEV >80%)
Moderate persistent (Daily symptoms, FEV 60-80%)
Severe persistent (Continuous symptoms, FEV <60%)

Question 9

What is cystic fibrosis?

Answer 9

Cystic fibrosis is an autosomal recessive disease resulting in altered chloride and water transport (CFTR gene) across epithelial cells; this prevents sodium reabsorption by epithelial sodium channels. Can impact respiratory, gastrointestinal, and reproductive systems.

Question 10

How is cystic fibrosis diagnosed?

Answer 10

Sweat chloride concentration exceeding 60 mEq/L in addition to one or more of the following:
- Chronic airway disease
- Exocrine pancreatic insufficiency
- Cystic fibrosis in first-degree relative
- Failure to pass meconium at birth is highly suggestive

Question 11

Treatment of cystic fibrosis

Answer 11

No cure
Proactive treatment of airway infection (prophylactic antibiotics, often azithromycin)
Chest therapy
Involvement of pancreas leading to diabetes is common
Lack of digestive enzymes may lead to malabsorption and difficulty absorbing Vit A, D, E, K. Treated with pancreatic enzyme replacement.

Question 12

Anesthetic considerations for cystic fibrosis

Answer 12

Optimize pulmonary status, r/o active infection
Chest physiotherapy prior to surgery
Electrolytes, LFTs, chest XR
Risk of pneumothorax is high (avoid nitrous oxide)
Procedure later in the day (allow clearance of night-time secretions)
Ketamine relatively contraindicated (secretions)
Prophylactic beta agonist

Question 13

What is COPD?

Answer 13

COPD is an irreversible disease that causes airway obstruction by either chronic bronchitis and/or emphysema

Question 14

How is COPD classified?

Answer 14

I (mild), II (moderate), III (severe), IV (very severe)
Based on FEV1/FVC

Treatment starts with short acting bronchodilator (albuterol) and transitions to long acting bronchodilator (salmeterol, formoterol, bambuterol), anticholinergics (atrovent, spiriva, combivent), then to inhaled steroid and oxygen/pulmonary rehabilitation

Question 15

Chronic bronchitis

Answer 15

“Blue bloaters” - results in chronic hypersecretion of mucus in the bronchi resulting in increased resistance to airflow and irreversible airway obstruction

Question 16

Emphysema

Answer 16

“Pink puffers” is enlargement of the airway due to destruction of the airway walls distal to bronchioles. This leads to loss of elasticity/recoil. Symptoms include dyspnea, cough, sputum production, and decreased exercise tolerance. “Barrel Chest” due to hypertrophy of the accessory muscles used during respiration.

Question 17

Diagnosis of COPD (tests, labs, imaging, etc)

Answer 17

PFTs including spirometry

Bronchitis = productive cough at least 2 consecutive years

Blood labs = hypercarbia, polycythemia, decreased serum alpha 1 antitrypsin levels, and leukopenia.

Chest radiographs may demonstrate lung nodules, bullae, hyperinflated lungs, masses, or fibrotic changes.

Pulse oximetry at rest, during exertion, and during sleep is useful to examine for hypoxemia and need for supplemental oxygen

Question 18

Anesthesia considerations for COPD patients

Answer 18

Smoking cessation for 6 weeks
EKG to r/o right-sided heart disease and ischemic heart disease
CXR (extensive bullae = higher risk of pneumothorax)
Chest physiotherapy to loosen secretions and dislodge mucus plugs.
Avoid nitrous oxide
Consider B2 agonist and antimuscarinic (robinul) to increase airway patency
Avoid over oxygenation (ventilation-perfusion mismatch) Maintain O2 sats 88-92%
Watch out for breath-trapping (intrinsic positive PEEP) if intubated
Diminished response to hypercarbia
Local anesthesia preferred.

Question 19

Sources of pulmonary emboli

Answer 19

Thrombus from vein in lower extremity
Mural thrombus from atrial fibrillation
Fat embolism from long bones

Question 20

Virchow’s Triad

Answer 20

Stasis, damage to endothelium, and hypercoagulable state

These are risk factors for pulmonary embolus
- Immobility, malignancy, disability, obesity, oral contraceptives, pregnancy, factor V leiden, antiphospholipid syndrome, and protein C and S deficiency, DVT, recent long bone fracture, hormone replacement therapy)

Question 21

Diagnosis of PE

Answer 21

Signs/symptoms: pleuritic chest pain, dyspnea, tachypnea, hemoptysis, coughing, JVD, cyanosis, rales and rhonchi, diminished breath sounds.

D-dimer assay: highly sensitive, if negative PE unlikely

CXR may show cardiomegaly, atelectasis, pulmonary effusions, raised diaphragm

CT angiography

Venous ultrasonography to rule out DVT

Arterial blood gas: hypoxemia, respiratory alkalosis, and hypocapnia

Wells criteria >4 = probable PE (clinical signs/symptoms, high suspicion of PE as diagnosis, HR >100, surgery within 1 month or immobility >3 days, history of PE or DVT, malignancy, hemoptysis)

Question 22

Treatment for PE

Answer 22

Anticoagulation to prevent progression of thrombus and decrease additional thrombotic episodes. Consideration given for fibrinolytics and embolectomy for massive PE.

• Initial treatment with unfractionated heparin (goal PTT 60-85), low molecular weight heparin with bridging to warfarin for goal INR 2-3.
• If anticoagulation is contraindicated, inferior vena cava filter is indicated
• 3 months anticoagulation is recommended for most patients.
• Lifelong anticoagulation for patients with unprovoked PE, recurrent DVTs, massive PEs, and malignancies associated with thrombosis.

Question 23

What is montelukast?

Answer 23

leukotriene receptor antagonist

Question 24

What is ipratropium?

Answer 24

anticholinergic bronchodilator

Question 25

What is albuterol?

Answer 25

B2 agonist

Question 26

The most objective and relevant tests for measuring the degree of airway obstruction in asthmatic patients

Answer 26

FEV1
Peak expiratory flow (PEF)

Well controlled asthma: FEV1 should be 80% of FVC

Question 27

Preferred general anesthetic for asthmatic patient

Answer 27

Propofol