Respirology

Question 1

List 6 hemodynamic changes with the application of positive pulmonary end expiratory pressure.

Answer 1

1) Decreased venous return to the right heart.
2) Increased right ventricular afterload.
3) Decreased ventricular compliance.
4) Decreased ventricular contractility.
5) Decreased cardiac output.
6) Decreased left ventricular afterload.

Question 2

List 4 respiratory changes with the application of positive pulmonary end expiratory pressure.

Answer 2

1) Re-expands collapsed alveoli.
2) Redistributes lung water from alveoli to interstitium, and improves V Q mismatch.
3) Increased functional residual capacity.
4) If hyperinflation and lung overdistention occurs, there will be a rise in partial pressure of arterial carbon dioxide.

Question 3

Anesthetic considerations for different types of lung tumors. Name 5 features and considerations of squamous cell carcinoma.

Answer 3

1) Often due to smoking.
2) Predominantly central lesions.
3) Often with endobronchial tumor.
4) Mass effects cause obstruction, cavitation, hemoptysis and pneumonia.
5) Hypercalcemia occurs from PTH related peptide.

Question 4

Name 6 features and considerations of adenocarcinoma.

Answer 4

1) Most common non small cell lung cancer.
2) Peripheral lesions.
3) Extrapulmonary invasion is common.
4) It has the most Pancoast tumors.
5) It promotes growth hormone and corticotropin AKA ACTH.
6) Hypertrophic osteoarthropathy.

Question 5

Name 2 features of large cell lung cancer.

Answer 5

1) Large, cavitating peripheral tumors.

2) Similar to adenocarcinoma.

Question 6

Name 6 features of small cell carcinoma.

Answer 6

1) Fast growth rate.
2) Early metastases.
3) Large, cavitating peripheral tumors.
4) Surgery usually not indicated.
5) Lambert Eaton syndrome
6) Paraneoplastic syndromes such as SIADH, and ectopic ACTH.

Question 7

Name 7 features of carcinoid tumors.

Answer 7

1) Proximal in location, endobronchial.
2) Bronchial obstruction with distal pneumonia.
3) Highly vascular.
4) Predominantly benign.
5) No association with smoking.
6) 5 year survival is more than ninety percent.
7) Carcinoid syndrome is rare.

Question 8

Name 6 non surgical maneuvers for cardiac herniation after thoracic surgery.

Answer 8

1. Supportive care such as A B Cs, fluids, vasopressors, inotropes.
2. Ensure there is no suction on chest tube to surgical side.
3. Discontinue peep.
4. Maintain spontaneous ventilation, or lower tidal volumes. Increase respiratory rate.
5. Position patient lateral, with surgical side up.
6. Inject 1 to 2 liters of air into surgical side of lung.

Question 9

Name 3 concerns regarding a bronchopleural fistula.

Answer 9

1) Need to isolate the healthy lung from infection.
2) Risk of tension pneumothorax with positive pressure ventilation.
3) Inadequate ventilation secondary to an air leak from the fistula.

Question 10

Name 3 different ways to manage a bronchopleural fistula.

Answer 10

1) Awake intubation with double lumen tube, (or single lumen tube is it is a small fistula).
2) Induction and intubation with a double lumen tube while patient is kept spontaneously ventilating. Use fiber optic bronchoscopy if the patient is post pneumonectomy.
3) Minimally invasive surgery, with use of an in situ thoracic epidural and sedation.

Question 11

What are 6 indications to insert a right sided double lumen tube?

Answer 11

Distorted anatomy of the entrance to the left mainstem, which includes:

1) External or intraluminal tumor compression.
2) Descending thoracic aortic aneurysm.

Site of surgery involving the left mainstem:

3) Left lung transplant.
4) Left tracheobronchial disruption.
5) Left sided sleeve resection.
6) Left pneumonectomy (this is a mild indication, it can be done with a left sided double lumen tube)

Question 12

What are 8 complications of mediastinoscopy?

Answer 12

1) Occlusive cerebrovascular accident due to innominate artery compression.
2) Pneumothorax.
3) (Left?) Recurrent laryngeal nerve damage.
4) Phrenic nerve injury.
5) Esophageal injury.
6) Mediastinitis
7) Venous Air embolism.
8) Chylothorax.

Question 13

List 5 structures that may be compressed during mediastinoscopy.

Answer 13

1) Innominate artery.
2) Trachea.
3) Esophagus.
4) Recurrent laryngeal nerve.
5) Phrenic nerve.

Question 14

What are 7 contraindications to mediastinoscopy?

Answer 14

1) Previous mediastinoscopy is a relatively strong contraindication to a repeat procedure because scar tissue eliminates the plane of dissection.
2) Superior vena cava (SVC) syndrome increases the risk of bleeding from distended veins and is a relative contraindication.
3) Severe tracheal deviation.
4) Thoracic aortic aneurysm.
5) Cerebrovascular disease.
6) Severe cervical spine disease with limited neck extension.
7) Previous chest radiotherapy.

Question 15

What is the three legged stool of pre thoracotomy respiratory assessment?

Answer 15

1) Respiratory mechanics which has 4 parameters:
a) Predicted post operative FEV 1 value of more than forty percent.
b) Other parameters include maximum voluntary ventilation, reserve volume over total lung capacity, and forced vital capacity.
2) Cardio pulmonary reserve which has 4 parameters:
a) VO 2 max of more than 15 milliliters per kilogram per min. Note: An estimated predicted post operative V O 2 max of less than 10 milliliters per kilogram per minute may be an absolute contraindication to pulmonary resection.
b) Stair climb of more than 2 flights of stairs.
c) 6 minute walk test with a distance of more than two thousand feet.
d) Exercise oximetry with a decrease of less than 4 percent with two flights of stairs.
3) Lung parenchymal function:
a) Predicted post operative diffusing lung capacity for carbon monoxide value of over forty percent.
b) Partial pressure of oxygen in arterial blood is more than sixty percent.
c) Partial pressure of carbon dioxide is less than forty five percent.

Question 16

How do you classify post thoracotomy anesthetic management based on predicted post operative FEV 1 percentage?

Answer 16

1) Predicted post operative FEV 1 of more than forty percent: extubate in operating room if patient is alert, warm and comfortable.
2) Predicted post operative FEV 1 between thirty to forty percent: Consider extubation based on exercise tolerance, DLCO, V/Q scan and associated diseases.
3) Predicted post operative FEV 1 of less than thirty percent: staged weaning from mechanical ventilation. Consider extubation if more than twenty percent, plus thoracic epidural analgesia.

Question 17

According to Barash, what are 8 whole lung function screening tests that are used to predict if the patient has an elevated risk of post operative thoracic surgery complications?

Answer 17

1) Partial pressure of carbon dioxide in arterial blood of more than forty six millimeters mercury.
2) Partial pressure of oxygen in arterial blood of less than sixty millimeters mercury.
3) Forced vital capacity of less than fifty percent, or 1.5 milliliters per kilogram.
4) FEV 1 of less than fifty percent.
5) Vital capacity of less than two liters.
6) Minute ventilation volume of less than fifty percent, or less than fifty liters per minute.
7) Reserve volume over total lung capacity of more than fifty percent.
8) Diffusing lung capacity for carbon monoxide of less than fifty percent.

Note: Of these the most valid single test for post-thoracotomy respiratory complications is the predicted postoperative FEV1.

Question 18

What are 4 absolute indications for one lung ventilation?

Answer 18

1) Isolation of lung to prevent contamination of a healthy lung for two reasons:
a. Infection
b. Hemorrhage
2) Control of distribution of ventilation to only one lung for 4 reasons:
a. BP fistula
b. BP cutaneous fistula
c. Unilateral cyst or bullae
d. Major bronchial disruption or trauma
3) Unilateral lung lavage (for Sanitation)
4) Vats (for Visualization)

Question 19

What are 5 high priority relative indications to lung isolation?

Answer 19

1) Thoracic aortic aneurysm
2) Pneumonectomy
3) Lung volume reduction
4) Minimally invasive cardiac surgery
5) Upper lobectomy

Question 20

What are 4 low priority relative indications to lung isolation?

Answer 20

1) Esophageal surgery
2) Middle and lower lobectomy
3) Mediastinal mass resection, thymectomy
4) Bilateral sympathectomies

Question 21

Name 11 reasons for postoperative arterial hypoxemia.

Answer 21

1) Atelectasis.
2) Alveolar hypoventilation from residual opioids, neuromuscular blockade, and inhalational agents.
3) V/Q mismatch, or shunt, from CHF, pulmonary edema, pneumothorax, or aspiration.
4) Dead space from pulmonary embolism,
5) Decreased DLCO from emphysema, interstitial lung disease, pulmonary fibrosis, or pulmonary hypertension.
6) Decreased FRC from advanced age or obesity.
7) Airway obstruction – tongue displacement, soft tissue collapse, edema, foreign body object, hematoma, or tracheal stenosis.
8) Diffusion hypoxia, which is unlikely if the patient is on supplemental oxygen.
9) Increased oxygen consumption from shivering or sepsis.
10) Transfusion related lung injury.
11) ARDS.

Question 22

Describe the anesthetic management of a mediastinoscopy induced hemorrhage.

Answer 22

1) Stop surgery and pack the wound. There is a serious risk that the patient will get too close to the point of hemodynamic collapse if the surgery-anesthesia team does not admit soon enough that there is a problem.
2) Begin the resuscitation and call for help, both anesthetic and surgical.
3) Obtain cross-matched blood in the operating room.
4) Obtain large-bore vascular access in the lower limbs.
5) Place an arterial line (if not placed at induction).
6) Prepare for massive hemorrhage with blood warmers and rapid infusers.
7) Place a double-lumen tube or bronchial blocker if the surgeon believes thoracotomy is a possibility
8) Convert to sternotomy or thoracotomy if indicated.

Question 23

List 5 factors that correlate with increased risk of desaturations during one lung ventilation.

Answer 23

1) Normal pre operative spirometry or restrictive lung disease
2) High percentage of ventilation or perfusion to the operative lung on preoperative V Q scan.
3) Right sided thoracotomy
4) Poor P A O 2 during two lung ventilation, particularly in the lateral position intraoperatively.
5) Supine position during one lung ventilation

Question 24

Describe your work up and management for desaturation during one lung ventilation.

Answer 24

1) For severe or precipitous desaturation, I would inform the OR team I am resuming two-lung ventilation, if possible.
2) Otherwise, ensure that delivered FIO 2 is at 1.
3) Verify adequacy of tidal volume.
4) Ensure that cardiac output is optimal from blood pressure and heart rate.
5) Decrease volatile anesthetics to less than 1 mac to minimize inhibition of hypoxic pulmonary vasoconstriction, and supply intravenous anesthetic infusion.
6) Check position of double-lumen tube or blocker with fiberoptic bronchoscopy.
7) Apply a recruitment maneuver to the ventilated lung (this will transiently make the hypoxemia worse).
8) Apply peep of 5centimeters water to the ventilated lung, except in patients with emphysema).
9) Apply a recruitment maneuver to the non ventilated lung, then immediately apply c pap of 1 to 2centimeters water to this lung.
10) Coordinate Intermittent reinflation of the nonventilated lung with the surgeon.
11) Other partial ventilation techniques of the nonventilated lung, including oxygen insufflation, high frequency ventilation, or lobar collapse using a bronchial blocker.
12) Mechanical restriction of the blood flow to the nonventilated lung such as clamping of the pulmonary artery.

Question 25

Name 5 benign tumors of the anterior mediastinum.

Answer 25

1) Thymoma
2) Thymic cyst
3) Thymolipoma
4) Retrosternal goiter
5) Cystic hygroma
6) Teratoma
7) Parathyroid adenoma

Question 26

Name 6 malignant anterior mediastinum tumors.

Answer 26

1) Thymic carcinoma
2) Thymic carcinoid
3) Thyroid carcinoma
4) Seminoma
5) Mixed germ cell
6) Lymphoma

Question 27

Name 5 middle mediastinum structures.

Answer 27

1) Benign adenopathy.
2) Bronchogenic cysts.
3) Esophageal masses.
4) Hiatal hernia.
5) Cardiovascular structures

Question 28

Name 6 patient related major risk factors associated with postoperative pulmonary complications.

Answer 28

1) Age over 60 years.
2) ASA class of higher than 2.
3) Congestive heart failure.
4) Pre existing pulmonary disease such as COPD.
5) Cigarette smoking.
6) Serum albumin of less than 35.

Question 29

Name 8 procedure related major risk factors associated with postoperative pulmonary complications.

Answer 29

1) Emergency surgery.
2) Abdominal surgery.
3) Thoracic surgery.
4) Head and neck surgery.
5) Neurosurgery.
6) Vascular surgery.
7) Prolonged duration of anesthesia such as more than 2.5 hours.
8) General anesthesia.

The history and physical examination findings of patients with COPD provide a more accurate assessment of the likelihood of postoperative pulmonary complications than pulmonary function test results or measurement of arterial blood gases. A history of poor exercise tolerance, chronic cough, or unexplained dyspnea combined with diminished breath sounds, wheezing, and a prolonged expiratory phase predicts an increased risk of postoperative pulmonary complications. Preoperative preparation of patients with COPD includes smoking cessation, treatment of bronchospasm, and eradication of bacterial infection.

The value of routine preoperative pulmonary function testing remains controversial. The results of pulmonary function tests and arterial blood gas analysis can be useful for predicting pulmonary function following lung resection, but they do not reliably predict the likelihood of postoperative pulmonary complications after nonthoracic surgery.

Question 30

What volumes in the lung are affected postoperatively, and which lung volume is the most important for gauging severity of the defect?

Answer 30

The changes in pulmonary function that occur postoperatively are primarily restrictive, with proportional decreases in all lung volumes and no change in airway resistance. The decrease in FRC, however, is the yardstick by which the severity of the restrictive defect is gauged.

Question 31

What is the most important determinant of postoperative pulmonary restriction and the risk of post operative pulmonary complication?

Answer 31

The operative site is one of the single most important determinants. The following three categories are in order of most to least severe effect on FRC decrease.

1) Nonlaparoscopic upper abdominal operations cause the most profound restrictive defect, precipitating a 40% to 50% decrease in FRC compared with preoperative levels, when conventional postoperative analgesia is employed.
2) Lower abdominal and thoracic operations cause the next most severe change in pulmonary function, with decreases in FRC to 30% of preoperative levels.
3) Most other operative sites—intracranial, peripheral vascular, otolaryngologic—have approximately the same effect on FRC, with reductions to 15% to 20% of preoperative levels.

Question 32

How long does it take for FRC to recover after upper abdominal operations?

Answer 32

3 to 7 days. With intermittent C papp by mask, FRC wil recover within 72 hours. After median sternotomy for cardiac operations, FRC does not return to normal for several weeks, regardless of postoperative pulmonary therapy. The single most important aspect of postoperative pulmonary care is getting the patient out of bed, preferably walking.

Question 33

Describe the management of controlled ventilation in the COPD patient during general anesthesia.

Answer 33

Controlled mechanical ventilation is useful for optimizing oxygenation in patients with COPD who are undergoing operations requiring general anesthesia. Tidal volumes of 6 to 8 mL/kg combined with slow inspiratory flow rates minimize the likelihood of turbulent airflow and help maintain optimal ventilation/perfusion matching. Slow respiratory rates (6 to 10 breaths per minute) provide sufficient time for complete exhalation to occur, which is particularly important if air trapping is to be minimized. Slow rates also allow sufficient time for venous return and are less likely to be associated with undesirable degrees of hyperventilation. The phenomenon of air trapping or dynamic hyperinflation is enhanced when positive pressure ventilation is applied and insufficient expiratory time is allowed. This contributes to increased intrathoracic pressure, impedes venous return, and transmits the elevated intrathoracic pressure to the pulmonary artery. An increase in pulmonary vascular resistance can lead to right ventricular strain. Hyperinflated lungs may exert direct pressure on the heart, limiting its ability to expand fully during diastole even with adequate preload. Shift of the ventricular septum and ventricular interdependence due to the shared pericardium may cause a distended right ventricle to impinge on the filling of the left ventricle.
Air trapping can be detected during mechanical ventilation intraoperatively by the following methods:
1. Capnography shows that the carbon dioxide concentration does not plateau but is still upsloping at the time of the next breath. This indicates that there is still admixture of air from dead space reducing the carbon dioxide concentration.
2. Direct measurement of flow may be displayed graphically by the ventilator, showing that the expiratory flow has not reached baseline (zero) before initiation of the next breath.
3. Direct measurement of the resulting PEEP can be performed using more advanced ventilators that are capable of an expiratory hold.
4. The patient can simply be disconnected from the ventilator briefly and observed to see whether the blood pressure increases significantly as PEEP is eliminated.

Question 34

What is the increase in partial pressure of carbon dioxide in the event of apneic oxygenation?

Answer 34

In the presence of apnea but provision of oxygen, the arterial partial pressure of carbon dioxide increases 5-10 millimeters mercury during the first minute. This initial rapid increase in arterial partial pressure of carbon dioxide represents equilibration of the alveolar gas with the venous partial pressure of carbon dioxide. After the first minute of apnea, the arterial partial pressure of carbon dioxide increases approximately 3 millimeters mercury per minute, reflecting metabolic production of CO2.

Question 35

Describe 3 physiological changes that occur when a patient is in lateral position, awake, breathing spontaneously and the chest is closed.

Answer 35

1) West zones are turned by 90 degrees.
2) Both blood flow and ventilation to the dependent lung are significantly greater than that to the non dependent lung.
3) The dependent hemi diaphragm is pushed higher into the chest by the abdominal contents compared with the nondependent lung hemi diaphragm.

Question 36

Describe 2 physiological changes that occur when a patient is in lateral position, awake, breathing spontaneously and the chest is open.

Answer 36

Controlled positive-pressure ventilation is the most common way to provide adequate ventilation and ensure gas exchange in an open-chest situation. Two complications can arise from the patient breathing spontaneously with an open chest.

1) Mediastinal shift, usually occurring during inspiration.
2) Paradoxical breathing. During inspiration, atmospheric pressure in the open hemithorax can cause movement of air from the non dependent lung into the dependent lung. During expiration, air moves from the dependent lung into the non dependent lung.

Question 37

Describe 2 physiological changes that occur when a patient is in lateral position, anesthetized, breathing spontaneously and the chest is closed.

Answer 37

1) Induction of general anesthesia causes a reduction in the volumes of both lungs secondary to a reduction in FRC.
2) The nondependent lung moves to a steeper position on the compliance curve and receives most of the tidal volume, whereas the dependent lung is on the flat (noncompliant) part of the curve. This results in a significant V Q mismatch.

Question 38

Describe a physiological change that occurs when a patient is in lateral position, anesthetized, breathing spontaneously and the chest is open.

Answer 38

Opening the chest has little impact on the distribution of perfusion.
The upper lung is now no longer restricted by the chest wall and is free to expand, resulting in a further increase in V Q mismatch as the nondependent lung is preferentially ventilated, owing to a now increased compliance.

Question 39

Describe a physiological change that occurs when a patient is in lateral position, anesthetized, paralyzed and the chest is open.

Answer 39

During paralysis and positive-pressure ventilation, diaphragmatic displacement is maximal over the nondependent lung, where there is the least amount of resistance to diaphragmatic movement caused by the abdominal contents. This further compromises the ventilation to the dependent lung and increases the V Q mismatch.

Question 40

List three types of airway categories based on functional lung anatomy.

Answer 40

1) Conductive airways allow or conduct basic gas transport without gas exchange. This ranges from trachea to terminal bronchioles.
2) Transitional airways have smaller diameters. Respiratory bronchioles are conduits for gas movement, while alveolar ducts allow limited gas diffusion and exchange.
3) Respiratory airways’ primary function is gas exchange. These include alveoli and alveolar sacs.

Question 41

Describe 2 types of toxic alterations in hemoglobin which affect pulse oximetry readings.

Answer 41

1) Carboxyhemoglobin causes a slight reduction of the assessment of oxygen saturation by pulse oximetry, by overestimating the fraction of hemoglobin available for oxygen transport.
2) Methemoglobin levels cause pulse oximetry readings to approach 85%, independent of actual oxygen saturations.

Question 42

Describe 3 types of dyes which affect pulse oximetry readings.

Answer 42

1) Indigo carmine causes a transient decrease.
2) Indocyanine green causes a transient decrease.
3) Methylene blue causes transient marked decrease for several minutes.

Question 43

Describe 5 other factors which can affect pulse oximetry readings.

Answer 43

1) Reduced blood flow
2) Jaundice may cause falsely high carboxyhemoglobin and methemoglobin readings, and low oximetry readings.
3) Blue nail polish.
4) Vasodilatation causes a slight decrease.
5) Venous pulsation such as tricuspid insufficiency can cause an artifactual decrease.

Question 44

List 3 sources of physiologic shunt.

Answer 44

1) Thebesian veins, which empty into all four chambers of the heart.
2) Bronchial veins, which drain directly into pulmonary veins.
3) Visceral pleural veins, which drain into the bronchial veins.

Question 45

What is the consensus on nitric oxide for ARDS?

Answer 45

According to an article titled “Effect of nitric oxide on oxygenation and mortality in acute lung injury: systematic review and meta-analysis” in 2007 in the british journal of medicine, nitric oxide is associated with limited improvement in oxygenation until day 4 in patient with ARDS. There was no difference in hospital mortality, ventilator free days, or duration of ventilation. Patients receiving nitric oxide had an increased risk of developing renal dysfunction.

Question 46

Hypoxic pulmonary vasoconstriction is directly inhibited by which 13 factors?

Answer 46

1) Mediators such as substance P, calcitonin, and atrial natriuretic peptide.
2) Endothelium derived vasodilators such as prostacyclin, and nitric oxide.
3) Nitroglycerin and nitroprusside.
4) Halogenated anesthetics. Halothane inhibits HPV the most, followed by enflurane and isoflurane.
5) Alpha adrenergic blockade.
6) Beta adrenergic stimulation.
7) Calcium channel blockers.
8) Increased left atrial pressure.
9) Increased alveolar pressure
10) Infection
11) Hypocarbia
12) Alkalosis.
13) Peripheral chemoreceptor stimulation.

Question 47

Hypoxic pulmonary vasoconstriction is indirectly inhibited by which 6 factors?

Answer 47

Factors associated with an increase in pulmonary artery pressure antagonize the effect of increased resistance caused by HPV and result in increased flow to the hypoxic region.

1) Mitral stenosis
2) Volume overload
3) Thromboembolism
4) Hypothermia
5) Vasoconstrictor drugs
6) Large hypoxic lung segment

Question 48

Hypoxic pulmonary vasoconstriction is enhanced by which 6 factors?

Answer 48

1) Acidosis
2) Beta adrenergic blockade
3) Epidural blockade
4) Low dose serotonin
5) Cyclo oxygenase inhibitors such as aspirin or NSAIDs
6) Inhibition of nitric oxide synthase such as L arginine analogs.

Question 49

List 6 subjective clinical criteria for a routine awake extubation.

Answer 49

1) Follows commands
2) Clear oropharynx or hypopharynx, no blood or secretions.
3) Intact gag reflex
4) Sustained head lift for 5 seconds, sustained hand grasp.
5) Adequate pain control.
6) Minimal end expiratory concentration of inhaled anesthetics.

Question 50

List 5 objective clinical criteria for a routine awake extubation.

Answer 50

1) Vital capacity of more than 10 milliliters per kilogram.
2) Tidal volume of more than 6 milliliters per kilogram.
3) Peak voluntary negative inspiratory pressure of more than negative 20 centimeters water.
4) Sustained tetanic contraction of more than 5 seconds.
5) T1 over T4 ratio of more than 0.7 for train of four.
6) Alveolar arterial partial pressure of oxygen gradient of less than 350 millimeters mercury on an FIO2 of 1.
7) Dead space to tidal volume ratio of less than 0.6.

Question 51

List 7 factors that increase end tidal CO2 during anesthesia.

Answer 51

Increases in end tidal CO2 are due to elements that either increase metabolic rate to increase production, or increase CO2 elimination.

1) Hyperthermia
2) Sepsis
3) Malignant hyperthermia
4) Shivering
5) Hyperthyroidism
6) Hypoventilation
7) Rebreathing

Question 52

List 5 factors that decrease end tidal CO2 during anesthesia.

Answer 52

Decreases in end tidal CO2 are due to elements that either
decrease metabolic rate to decrease production, or decrease CO2 elimination.
1) Hypothermia
2) Hypothyroidism
3) Hyperventilation
4) Hypoperfusion
5) Pulmonary embolism

Question 53

List 2 causes for fixed obstruction of the upper airway.

Answer 53

Fixed obstruction limits flow equally during inspiration and expiration.

1) Tracheal stenosis
2) Goiter

Question 54

List 2 causes for variable extrathoracic obstruction of the airway.

Answer 54

1) unilateral vocal cord paralysis

2) vocal cord dysfunction

Question 55

List 2 causes for variable intrathoracic obstruction of the airway.

Answer 55

1) Tracheomalacia. During a forced inspiration, negative pleural pressure holds the floppy trachea open. With forced expiration, loss of structural support results in tracheal narrowing and a plateau of diminished flow. Airflow is maintained briefly before airway compression occurs.

Question 56

List 6 factors that can increase closing capacity.

Answer 56

1) Age
2) Smoking
3) Obesity
4) Supine position more than upright.
5) Anesthetized patients
6) Pregnancy
7) Lung disease such as COPD

Note: Some references state pregnancy, obesity and supine position has no change in closing capacity. They will have higher airway closure in terms of decreased FRC and where the closing capacity sits relative to FRC.

Question 57

List 9 factors that decrease functional residual capacity.

Answer 57

4 disease factors that reduced FRC include:

1) Acute lung injury
2) Pulmonary edema
3) Pulmonary fibrotic processes
4) Atelectasis

5 Mechanical factors include:

5) Pregnancy
6) Obesity
7) Pleural effusion
8) Posture, Supine more so than lateral.
9) Ventilatory weakness or paralysis

Question 58

List 3 physiological changes, and their respective timelines, after smoking cessation.

Answer 58

1) Normal carboxyhemoglobin concentration in nonsmokers is approximately 1%; in smokers, however, it can be as high as 8% to 10%. Cessation of smoking, even for 12 to 24 hours preoperatively, can decrease CO concentration to near normal.
2) Normalization of mucociliary function requires 2 to 3 weeks of abstinence from smoking, during which time sputum increases.
3) Several months of smoking abstinence is required to return sputum clearance to normal.

Note: Smoking patients should be advised to stop smoking 2 months prior to elective operations to maximize the effect of smoking cessation, or for at least 4 weeks to benefit from improved mucociliary function and some reduction in PPC rate. If patients cannot stop smoking for 4 to 8 weeks preoperatively, it is controversial whether they should be advised to stop smoking 24 hours preoperatively. A 24-hour smoking abstinence would allow carboxyhemoglobin levels to fall to normal but may increase the risk of PPC.

Question 59

List 11 symptoms of oxygen toxicity during hyperbaric oxygen therapy.

Answer 59

Toxicity during therapy affects mainly the lung, CNS and the eye.  Pulmonary toxicity in the conscious patient include:
1)	Tracheobronchial irritation with cough and burning chest pain.
2)	Decreased vital capacity
3)	ARDS with prolonged exposure
CNS toxicity presents as:
4)	Nausea and vomiting
5)	Numbness
6)	Twitching
7)	Dizziness
8)	Olfactory, acoustic or taste sensations
9)	Nonfocal tonic clonic seizures
Eye toxicity includes:
10)	Myopia
11)	Retinopathy of prematurity

Question 60

Describe Reynold’s number.

Answer 60

For a given flow geometry (e.g., flow through a tube of circular cross-section), transition from laminar to turbulent flow occurs at a critical value. In straight, smooth, circular tubes, transition from laminar to turbulent flow occurs at a Reynold’s number of approximately 2100, which is a dimensionless ratio. Resistance depends on gas viscosity during laminar flow, while resistance depends on gas density during turbulent flow.

Question 61

What is the change in FRC with regards to position and induction of general anesthesia?

Answer 61

FRC is reduced by almost 1 liter, or 10 to 15%, by moving from upright to supine position. Induction of anesthesia further decreases the FRC by 0.5 liters or 10%. Muscle paralysis does not cause additional reduction in FRC.

Question 62

How much does vital capacity decrease within 1 to 2 days after surgery and when does it return to normal?

Answer 62

Vital capacity is decreased by 25 to 50 percent within 1 to 2 days after surgery and generally returns to normal after 1 to 2 weeks.

Question 63

How much do the following lung parameters change by after surgery?

Answer 63

1) Residual volume
Answer: Increases by 13%.

2) Expiratory reserve volume
Answer: Decreases 25% after lower abdominal surgery and 60% after upper abdominal and thoracic surgery.

3) Tidal volume
Answer: Decreases 20 % within 24 hours. Recover in 2 weeks.

Question 64

List 6 advantages to using LMAs in supraglottic surgery.

Answer 64

1) Protection of the airway from blood and surgical debris
2) Reduced cardiovascular responses
3) Reduced coughing on emergence
4) Reduced laryngospasm after airway device removal
5) Improved oxygen saturation after airway device removal
6) Ability to administer oxygen until complete restoration of airway reflexes

Question 65

What is the volume of total lung capacity?

Answer 65

6 to 8 liters

Question 66

What is the volume per kilogram for vital capacity?

Answer 66

Vital capacity is usually 60 milliliters per kilogram, or 4 to 6 liters in an adult.

Question 67

What is the volume per kilogram for tidal volume?

Answer 67

Tidal volume is 6 to 8 milliliters per kilogram.

Question 68

What is the volume of residual volume?

Answer 68

2 to 2.5 liters.

Question 69

What is the volume per kilogram for functional residual capacity?

Answer 69

Functional residual capacity is usually 30 milliliters per kilogram, or 3 to 4 liters in an adult.

Question 70

What is volume of anatomic dead space per kilogram in an adult?

Answer 70

2 milliliters per kilogram. It is also 30% of tidal volume in a healthy adult.

Question 71

What is the minute volume ventilation of a healthy young adult?

Answer 71

170 L per minute

Question 72

What is the oxygen consumption for an adult?

Answer 72

Oxygen consumption is usually 3 milliliters per kilogram per minute in an adult. For an infant, it is 8 milliliters per kilogram per minute.

Question 73

List 4 central etiologies that cause hyperventilation.

Answer 73

1) Drug administration such as aminophylline, salicylates and norepinephrine.
2) Intracranial hypertension
3) Hepatic cirrhosis
4) Nonspecific arousal states such as anxiety and fear

Question 74

What are 3 anatomic landmarks for placement of a chest tube?

Answer 74

1) Lateral border of the pectoralis major
2) Anterior axillary line
3) 4th or 5th intercostal space, above the rib.

Question 75

List 5 factors that can influence diffusing capacity of the lung.

Answer 75

1) Decreased hemoglobin concentration decreases it
2) Increased PACO2 increases it
3) Exercise increases it
4) Supine position increases it
5) Pulmonary capillary blood volume

Note: Normal value of DLCO is 17-25 milliliters per minute per millimeters mercury.

Question 76

During two lung ventilation in the lateral position, what is the distribution of cardiac outflow between nondependent and dependent lung?

Answer 76

The nondependent lung receives 40% of cardiac output, while the dependent lung receives 60%.

Question 77

During two lung ventilation in the lateral position, what percentage of cardiac output is participating in gas exchange in the lungs?

Answer 77

Normally, venous admixture in the lateral position is 10% of cardiac output and is equally divided as 5% in each lung. Therefore, the average percentage of cardiac output participating in gas exchange is 35% in the nondependent lung and 55% in the dependent lung.

Question 78

During one lung ventilation in the lateral position, what is the fractional blood flow in the non dependent lung? What percentage of this participates in gas exchange?

Answer 78

During two lung ventilation, 35% of cardiac output participates in gas exchange in the non dependent lung. With active hypoxic pulmonary vasoconstriction, blood flow to the nondependent hypoxic lung will be decreased by 50% and therefore is 17.5%. To this, the original 5% venous admixture must be added, for a total of 22.5% fractional flow in the non dependent lung during one lung ventilation. None of this participates in gas exchange, it is all shunt.

Question 79

During one lung ventilation in the lateral position, what is the fractional blood flow in the dependent lung? What percentage of this participates in gas exchange?

Answer 79

During two lung ventilation, 55% of cardiac output participates in gas exchange in the dependent lung. With hypoxic pulmonary vasoconstriction redistributing 17.5% to dependent lung, plus the original 5% venous admisture, the total fractional blood flow is 77.5%. 72.5% participates in gas exchange.

Question 80

List 4 mechanisms of increased arterial to end tidal CO2 gradient.

Answer 80

1) Increased dead space such as emphysema, smoking, advanced age or pulmonary embolism
2) Iatrogenic single lung ventilation
3) Decreased minute ventilation such as shallow breaths or hypoventilation
4) Anesthesia

Question 81

For the following oxygen saturations, list the corresponding partial pressures of oxygen.

Answer 81

1) 10%

Answer: PAO2 is 10 millimeters mercury

2) P 50

Answer: 27 millimeters mercury

3) 75% O2 saturations

Answer: 40 millimeters mercury

4) P 90

Answer: 60 millimeters mercury

5) 98% O2 saturations

Answer: 100 millimeters mercury

Question 82

List the four most common indications for lung transplantation:

Answer 82

1) COPD
2) Cystic fibrosis and other congenital forms of bronchiectasis
3) Pulmonary fibrosis: idiopathic, associated with connective tissues disorders, etc
4) Primary pulmonary hypertension