Apex Unit 1 Respiratory Flashcards

Question

Select the statements that BEST describe the carotid chemoreceptors. (Select 2.) They are more sensitive after carotid endarterectomy. Type I Glomus cells mediate hypoxic ventilatory drive. Hering's nerve is part of the afferent limb. They are more sensitive to SaO2 than PaO2.

Answer 1

Hering's nerve is part of the afferent limb. Type I Glomus cells mediate hypoxic ventilatory drive. While the central chemoreceptor in the medulla primarily responds to PaCO2, the peripheral chemoreceptors in the carotid bodies primarily respond to PaO2 (not SaO2). Type I Glomus cells are the sensors that transduce PaO2 into an action potential. They mediate the hypoxic ventilatory drive. This action potential is propagated along the afferent limb, which consists of Hering's nerve and the glossopharyngeal nerve (CN IX). Carotid endarterectomy impairs the function of the peripheral chemoreceptors on the same side.

Answer 2

Hering-Breuer inflation reflex The Hering-Breuer inflation reflex prevents alveolar overdistension by stopping inhalation when lung volume is too large.

Answer 3

Desflurane Hypoxic pulmonary vasoconstriction minimizes shunt by diverting pulmonary blood flow away from unventilated alveoli. Agents that impair HPV increase the shunt fraction and reduce PaO2. Examples: Halogenated anesthetics (> 1 – 1.5 MAC) IV anesthetic agents preserve HPV.

Answer 4

injected just below the border of the greater cornu of the hyoid bone. There are 3 key airway blocks: 1. Glossopharyngeal 2. Superior laryngeal 3. Transtracheal To block the superior laryngeal nerve, local anesthetic is injected just below the border of the greater cornu of the hyoid bone. 1 mL of local anesthetic is injected outside of the thyrohyoid membrane. 2 mL are injected just beneath the thyrohyoid membrane.

Answer 5

NOT the arytenoids but same spot!! You guys have seen this view hundreds of times. Even so, you've likely succumbed to one of the most common misteachings in anesthesia. You CANNOT see the arytenoids during laryngoscopy! What you are actually seeing are the corniculate and cuneiform cartilages. The cuneiforms are lateral to the corniculates.

Answer 6

You may know this concept as the laryngospasm notch. Like it or not, the NCE likes to test your vocabulary. There are times where you'll have to know two or more words for the same thing. Believe it or not, we have 5 synonyms for pseudocholinesterase! Don't worry, we'll cover that in the neuromuscular blockers tutorial. For now, let's get back to laryngospasm and Larson's maneuver.

Answer 7

Inositol triphosphate Phospholipase C Leukotrienes While second messenger systems are covered in the autonomic nervous system tutorial, it's important to discuss them as they relate to control of airway caliber. Bronchoconstriction is mediated by the PNS (muscarinic-3 receptor) and the immune response. Bronchodilation is mediated by circulating catecholamines and the VIP receptor (nitric oxide pathway).

Answer 8

Theophylline + Methylxanthine Zafirlukast + Leukotriene modifier Cromolyn + Mast cell stabilizer Triamcinolone + Corticosteroid Many of you will see questions very similar to this on the NCE. While it's nearly impossible to learn all of the drugs in all of the classes, we recommend that you memorize at least the most common examples.

Answer 9

Forced expiratory flow at 25-75% vital capacity Airway resistance can be measured with dynamic pulmonary function testing. These tests include: FEV1 FVC FEV1/FVC ratio Forced expiratory flow at 25-75% vital capacity Forced expiratory flow is the average forced expiratory flow during the middle half of the FEV measurement. This test is the most sensitive indicator of small airway disease (obstruction). Diffusion capacity of CO is a measure of gas transfer and not airway resistance.

Answer 10

Asthma Positive predictors of postoperative pulmonary complications can be divided into patient, procedure, and diagnostic tests. Patient examples: age > 60, CHF, COPD, and cigarette smoking Procedure examples: surgical site, procedure lasting > 2.5 hours, and GA Diagnostic test examples: serum albumin < 3.5 g/dL Mild/moderate asthma, ABGs, and PFTs have not been shown to be independent predictors of postoperative pulmonary complications.

Answer 11

FEV1 FRC Restrictive disease reduces all of the lung volumes. FRC is decreased, although it may remain unchanged relative to the other volume and capacities. Since TLC is smaller and there is less volume to exhale, the amount of air exhaled in 1 second (FEV1) will be reduced. The FEV1/FVC ratio is usually unchanged. The FEF 25-75% is sensitive to increase air flow resistance in the medium sized airways. This isn't a problem for patients with a restrictive lung disease.

Answer 12

Vagal stimulation In the textbooks, you’ll usually find that asthma is classified by etiology or severity, but are these systems helpful in the differential diagnosis of asthmatic bronchospasm in the operating room? A more useful framework is to consider the source of bronchospasm as the result of direct PNS stimulation or as a consequence of an immune response (mast cell degranulation). Although intubation does not cause an immune response, it can activate vagal afferents leading to bronchospasm. This is most likely to occur during a lighter plane of anesthesia. Airway smooth muscle is not innervated by the SNS, so a reduction in SNS tone can't precipitate bronchospasm. Instead, airway smooth muscle is rich in beta-2 receptors, which explains how beta-2 agonists (epi, albuterol) cause bronchodilation. Although some of our induction agents cause histamine release, there are others that don't. Since the question didn't specifically state which drugs were administered, you shouldn't make any assumptions. The stem gives you exactly what you need to answer the question.

Answer 13

Hydrocortisone 2 mg/kg IV The key here is "acute" bronchospasm. Hydrocortisone may be given to prevent the requirement for longer term therapy, however it does nothing to reverse the acute phase. Indeed, corticosteroids require several hours to take effect. Epinephrine, ketamine, and lidocaine are useful in the treatment of acute bronchospasm.

Answer 14

Is the most common metabolic disease affecting the liver Causes panlobular emphysema Alpha-1 antitrypsin deficiency causes a relative increase in alveolar protease activity. This enzyme degrades pulmonary connective tissue and leads to the development of panlobular emphysema. Cigarette smoking doubles the rate of alveolar destruction. A deficiency in this enzyme does not increase the risk of bronchospasm. The only treatment for this condition is liver transplantation.

Answer 15

Respiratory rate 7 breaths per minute COPD is an issue of getting the air out of the lung. Any intervention that increases expiratory time will be useful. A slower respiratory rate accomplishes this goal. An I:E ratio of 1:1 increases I time at the expense of E time. This increases the risk of dynamic hyperinflation. FiO2 should be adjusted to prevent hypoxemia. Smaller tidal volumes (6-8 mL/kg) are preferred, again to minimize the risk of dynamic hyperinflation.

Answer 16

Decrease respiratory rate Disconnect the circuit The airway pressure in this waveform clearly depicts dynamic hyperinflation, otherwise known as breath stacking. Patients with COPD have a longer expiratory time constant, and this means they require a longer period of time to exhale fully. Of the answer choices provided, there are two options that reverse dynamic hyperinflation. By reducing the respiratory rate, the patient will spend more time over the course of a minute in E time. If PEEP becomes dangerously elevated, the definitive treatment for dynamic hyperinflation is to remove the patient from the ventilator. Increasing inspiratory time is another way of saying reducing expiratory time, so this choice will actually make the patient's condition worse. The inspiratory flow determines how fast the tidal volume is delivered to the patient. Increasing the inspiratory flow will deliver the preset tidal volume faster, and this does nothing to facilitate expiration.

Answer 17

Cystic fibrosis CF is an autosomal recessive genetic disorder that affects chloride channels. Excessive pulmonary secretions plug the airways and create an obstructive ventilatory defect. Management is similar to COPD and be sure to humidify the airway to minimize the tenacity of secretions. Avoid anticholinergics for the same reason. Sarcoidosis is a chronic granulomatous disorder that results in the development of granulomas that may progress to fibrosis. Nearly all patients with sarcoidosis have pulmonary involvement, and the disease can also affect the heart, CNS, skin, and eyes. They are often on steroids, so be sure to continue this therapy throughout the perioperative period. Flail chest results when cracked ribs move inward during inspiration, while the rest of the rib cage moves outward. The flail region then moves outward during expiration. Tidal volumes are reduced during spontaneous ventilation and increases the risk of hypoxemia. Positive pressure ventilation is the best treatment until the ribs can be stabilized. Negative pressure pulmonary edema increases interstitial lung water. This creates a restrictive defect.

Answer 18

Proton pump inhibitors Methods to reduce the incidence of ventilator associated pneumonia include: Minimizing the duration of mechanical ventilation Limiting sedation Oropharyngeal decontamination Proton pump inhibitors increase gastric pH, which provides an environment where bacterial pathogens can flourish. Microaspiration introduces these pathogens into the lungs.

Answer 19

14g angiocath insertion at the 2nd intercostal space midclavicular line Emergency treatment of a tension pneumothorax includes insertion of a 14g angiocath into the 2nd intercostal space at the mid-clavicular line or the 4th or 5th intercostal space at the anterior axillary line. This will release the tension and relieve hemodynamic instability, but not the underlying pneumothorax. Chest tube insertion is the definitive treatment. Pericardiocentesis is a treatment for pericardial tamponade. CPR should not be started based on a CXR alone.

Answer 20

TEE + 1 Precordial Doppler + 2 EtCO2 + 3 CVP + 4

Answer 21

Hyperventilation Nitric oxide Nitroglycerine When managing the adult with right heart failure or the infant with bronchopulmonary dysplasia or a right-to-left shunt, you must understand how to manipulate pulmonary vascular resistance. PVR is reduced by: hyperventilation, nitric oxide, and nitroglycerine. PVR is increased by: hypoxia, hypercarbia, nitrous oxide, hypothermia, and PEEP.

Answer 22

Binds to the oxygen binding site on hemoglobin with an affinity 200 times that of oxygen Carbon monoxide: Shifts the oxyhemoglobin dissociation curve to the left (not right). Is produced in soda lime, particularly after desiccation. Production is highest with desflurane (des > iso >>>sevo). Poisoning (increased carboxyhemoglobin) is treated with oxygen therapy. Methemoglobinemia is treated with methylene blue.

Answer 23

PaCO2 > 60 mmHg Inspiratory force < 25 cm H2O Other indications for tracheal intubation include: Vital capacity < 15 mL/kg (not < 25) Respiratory rate > 40 breaths per minute (not > 35) Keep in mind that no single variable indicates the need for intubation and mechanical ventilation.

Answer 24

Pulmonary infection Bronchopleural fistula Indications for one lung ventilation are divided into absolute and relative. Absolute indications are further broken down into 3 areas: ``` Isolation to avoid contamination Control of distribution of ventilation Unilateral bronchopulmonary lavage Most indications that improve surgical exposure are relative indications. Examples include esophageal resection and thoracic aortic aneurysm repair. ```

Answer 25

DLT is in too far on left side + Right breath sounds absent DLT is too far on right side + Left breath sounds absent DLT tip is in the trachea + Left and right breath sounds heard

Answer 26

Hemorrhage Pneumothorax The thorax contains some high value real estate, which explains why there are many complications associated with mediastinoscopy. ``` The most common serious complications are: #1 Hemorrhage #2 Pneumothorax (usually right side) ``` The thoracic ducts drain lymph into the subclavian veins. The left duct is much larger than the right duct, which explains why a left-sided injury is more common than a right-sided injury. Chylothorax (chyle or lymphatic fluid in the pleural space) is the result of thoracic duct injury. The left recurrent laryngeal nerve loops under the aortic arch before ascending the trachea. This explains why the left RLN is more susceptible to injury.

Answer 27

Class 3 The mandibular protrusion test assesses the function of the temporomandibular joint. The patient is asked to sublux the jaw, and the position of the lower incisors is compared to the position of the upper incisors. A class III assessment (like the patient in this question) suggests a more difficult laryngoscopy.

Answer 28

Posterior cricoarytenoid The posterior cricoarytenoid is the only muscle that ABducts the vocal cords. You may question the clinical relevance of knowing these sorts of details, however the NBCRNA website has a practice question about the intrinsic laryngeal muscles. That's a pretty good reason to learn it. The cricothyroid is the only muscle that tenses (elongates) the vocal cords. The aryepiglottic closes the laryngeal vestibule, and the lateral cricoarytenoid ADDucts the vocal cords.

Answer 29

External branch of the superior laryngeal nerve. Two branches of the vagus nerve provide innervation to the larynx: the superior laryngeal n. and the recurrent laryngeal n. The external branch of the SLN innervates the cricothyroid muscle. Remember that this is the only muscle that tenses (elongates) the vocal cords. The internal branch of the superior laryngeal n. is purely sensory. The recurrent laryngeal nerve innervates all of the other intrinsic laryngeal muscles. The glossopharyngeal n. does not innervate the larynx.

Answer 30

Trigeminal - Anterior tongue Glossopharyngeal - Vallecula Recurrent laryngeal - Trachea Superior laryngeal - Posterior epiglottis Knowing the sensory innervation of the airway is the foundation of understanding regional anesthesia for fiberoptic intubation. It will also help identify areas of failed topicalization. From proximal to distal: Anterior tongue: Trigeminal (V) V3 - mandibular branch Posterior tongue: Glossopharyngeal (IX) Soft palate: Glossopharyngeal (IX) Oropharynx: Glossopharyngeal (IX) Vallecula: Glossopharyngeal (IX) Anterior epiglottis: Glossopharyngeal (IX) Posterior epiglottis: Superior laryngeal internal branch (X) Laryngeal mucosa to level of vocal cords: Superior laryngeal internal branch (X) Laryngeal mucosa below level of vocal cords: Recurrent laryngeal (X) Trachea: Recurrent laryngeal (X)

Answer 31

3 mL at the inferior aspect of the greater cornu of the hyoid bone bilaterally There are three nerve blocks that will provide anesthesia for oral fiberoptic intubation: glossopharyngeal, superior laryngeal, and recurrent laryngeal. Once you learn the innervation of the airway, this question becomes much easier. This patient tolerated the scope in the oropharynx, which is innervated by the glossopharyngeal nerve. Once the scope entered the territory covered by the superior laryngeal internal branch, the patient became uncomfortable. To increase his tolerance for the rest of the procedure, you'll need to know which block to perform (superior laryngeal n. block) and know how to do it (inject 3 mL at the inferior aspect of the greater cornu of the hyoid bone bilaterally). This also could've been a hotspot question. As you study each question, ask yourself other ways that the question writer might cover the same material. The glossopharyngeal n. block is performed by injecting 1 - 2 mL at the tonsillar pillars bilaterally. The transtracheal block is performed by injecting 3 - 5 mL through the cricothyroid membrane.

Answer 32

Mitral stenosis The right RLN loops under the right subclavian artery, while the left RLN loops under the aorta. This makes the left RLN more susceptible to injury. Causes of left RLN (only) injury include: Mitral stenosis (left atrial enlargement compresses the nerve and may present as hoarseness). PDA ligation Aortic arch aneurysm Thoracic tumor Causes of left or right RLN injury include: parathyroid or thyroid surgery, external pressure from an LMA or ETT, neck tumor, and neck extension.

Answer 33

Epiglottis - 1 Corniculate - 2 Arytenoid - 3 Cricoid - 4 This question forces you to see the anatomy with your mind's eye. Whenever you answer any question, try to visualize what is going on. Maybe an image from this website, a textbook, or something of your own creation. Additionally, you should be able to label these if you are presented with the posterior or sagittal cut of the larynx. ``` Order from most superior to most inferior in the sitting position: Epiglottis Corniculate Arytenoid Cricoid ```

Answer 34

Three The larynx consists of 9 cartilages (3 paired and 3 unpaired): Paired cartilages = corniculate, arytenoid, and cuneiform Unpaired cartilages = epiglottis, thyroid, and cricoid

Answer 35

C3-C6 The adult larynx is located at the C3-C6 vertebrae. By comparison, the infant larynx is located at C2-C4.

Answer 36

Gastroesophageal reflux disease Exposure to second hand smoke Recent upper respiratory tract infection Laryngospasm is the sustained and involuntary contraction of the vocal cord adductors that results in the inability to ventilate. This response often outlasts the stimulus, and may result in complete airway obstruction, negative pressure pulmonary edema, gastric aspiration, cardiac arrest, and death. Risk factors include: ``` Age < 1 year (not old age) Hypocapnia (not hypercapnia) Light anesthesia (not deep anesthesia) Saliva or blood in the upper airway Gastroesophageal reflux disease Exposure to second hand smoke Recent upper respiratory tract infection ```

Answer 37

Tensor palatine - Opens the nasopharynx Genioglossus - Opens the oropharynx Hyoid muscles - Open the hypopharynx The upper airway dilator muscles maintain airway patency. Impairment of these muscles (anesthesia, sedation or OSA) can contribute to airway obstruction.

Answer 38

Mandibular body Larson's maneuver is another name for stimulating the laryngospasm notch. Application of postcondylar pressure stimulates a sigh and effectively breaks laryngospasm. Landmarks for Larson's maneuver include: Posterior: Mastoid process Superior: Skull base Anterior: Ramus of mandible Also, don't confuse Larson's maneuver with Muller's maneuver. Muller's maneuver is inhaling against a closed glottis. It's the opposite of the Valsalva maneuver - exhaling against a closed glottis.

Answer 39

Two There are three types of pneumocytes (alveolar cells): Type 1: Cells where gas exchange occurs ~80 percent of the alveolar surface Type 2: Produce surfactant and can divide to produce type 1 cells Type 3: Macrophages that fight lung infection

Answer 40

Ventilation/perfusion mismatch A ventilation/perfusion mismatch (specifically atelectasis) is the most common cause of postoperative hypoxemia. As FRC becomes smaller (the result of anesthesia and surgery), there is less radial traction to hold the airways open. The ultimate result is atelectasis, right-to-left shunt, V/Q mismatch, and hypoxemia. Treatment includes humidified oxygen, mobility, and pulmonary toilet (coughing, deep breathing, incentive spirometry).

Answer 41

Forced exhalation Breathing is a process that creates cyclic pressure changes inside the thorax. This mechanism exchanges fresh gas in the upper airway with alveolar gas in the distal airway, saturating hemoglobin with oxygen and eliminating carbon dioxide from the blood. For air movement to occur, the airways must remain patent. Transpulmonary pressure is the pressure inside the airway (it keeps the airway open). Transpulmonary pressure = alveolar pressure - intrapleural pressure Intrathoracic pressure and intrapulmonary pressure are other names for transpulmonary pressure. During tidal breathing: Transpulmonary pressure is always positive (keeps airway open). Intrapleural pressure is always negative (keeps lungs inflated). Alveolar pressure becomes slightly negative during inspiration and slightly positive during expiration. Aside from pathologic states, such as pneumothorax, the only time that intrapleural becomes positive is during a forced expiration.

Answer 42

Rectus abdominis Contraction of the inspiratory muscles reduces thoracic pressure and increases thoracic volume. This is an example of Boyle's law. Inspiration: The diaphragm and external intercostals contract during inspiration (tidal breathing). The diaphragm increases the superior-inferior dimension of the chest. The external intercostals increase the anterior-posterior diameter. Accessory muscles include the sternocleidomastoid and scalene muscles. Exhalation: Exhalation is usually passive; this process is driven by the recoil of the chest wall. Exhalation becomes an active process when minute ventilation increases or in patients with lung disease, such as COPD. A forced exhalation is required to cough and clear the airway of secretions. Active exhalation is carried out by the abdominal musculature (rectus abdominis, transverse abdominis, internal obliques, and external obliques). The internal intercostals serve a secondary role in active exhalation. Knowing this should help you better understand why upper abdominal surgery increases the risk of post-operative pulmonary complications.

Answer 43

Alveolar ventilation is a function of alveolar size and its position on its compliance curve (Alveolar compliance = Alveolar volume / Alveolar Pressure). The best ventilated alveoli are the most compliant. They exchange more gas, because their volumes change more throughout the respiratory cycle. These alveoli reside at the steep slope of the curve. The least ventilated alveoli are the least compliant. They exchange less gas, because their volumes change very little throughout the respiratory cycle. These alveoli reside near the top of the curve.

Answer 44

Dead space is ventilation without perfusion and shunt is perfusion without ventilation. The graph examines the V/Q relationship in the entire lung. Point C marks where ventilation and perfusion are equally matched. Point D marks the region where ventilation is greater than perfusion; dead space is increased here. Points A and B mark where perfusion exceeds ventilation; shunt is increased here.

Answer 45

It increases Vd/Vt describes the fraction of the tidal volume that is lost to dead space. Said another way, this gas is not involved in alveolar gas exchange. In the spontaneous ventilating patient, we can assume that the Vd = 2 mL/kg and Vt = 6 mL/kg. For easy math, we'll call Vd 150 mL and Vt 450 mL. Vd/Vt = 150 mL / 450 mL = 0.33 = 33% Mechanical ventilation increases alveolar pressure, and this increases ventilation relative to perfusion. This explains why Vd/Vt increases to 0.5 or 50 percent. Said another way, mechanical ventilation increases West zone one.

Answer 46

Increasing the tubing length of the circle system This question asked about an increased PaCO2-EtCO2 gradient. This is another way of asking what increases dead space ventilation or West zone one. The most common cause of increased dead space under general anesthesia is a reduction in cardiac output. COPD and pulmonary embolism increase dead space. Other causes include anticholinergics, mechanical ventilation, neck extension, adding a heat and moisture exchanger between the y-piece and the endotracheal tube, and an incompetent unidirectional valve. Remember that dead space begins at the y-piece. Increasing the length of the inspiratory or expiratory limb of the anesthesia circuit does NOT affect dead space. The only time that the limbs contribute to increased Vd is when one (or both) of the unidirectional valves is incompetent.

Answer 47

PaCO2 increases PaO2 decreases Adding an HME in-between the endotracheal tube and the y-piece increases apparatus dead space. If ventilation is held constant, the PaCO2 rises. An increased PaCO2 increases the alveolar concentration of CO2. Remember the alveolar gas equation? One of the many teaching points from this equation is that an increased PaCO2 causes the alveolar partial pressure of O2 to decrease. If this doesn't ring a bell, be sure to go back and read this in the Respiratory II: Physiology Tutorial.

Answer 48

PaO2 The alveolar gas equation is among the most important calculations in anesthesia. Chances are you'll see this concept tested in some way on the NCE. Here's the equation. PAO2 = FiO2 x (Pb - PH2O) - (PaCO2 / RQ) ``` PAO2 = partial pressure of O2 inside the alveolus FiO2 = fraction of inspired oxygen Pb = barometric pressure PH2O = humidity of inspired gas (assume this is 47 mmHg) PaCO2 = partial pressure of CO2 in the blood RQ = respiratory quotient (CO2 production / O2 consumption = 0.8) ```

Answer 49

Internal thoracic veins (internal mammary veins) Anatomic shunt (venous admixture) describes any venous blood that empties directly into the left side of the heart. Since this blood bypasses the lungs, it never has the opportunity to saturate with oxygen. Indeed, anatomic shunt explains why there is always an A-a gradient. ``` There are three causes of anatomic shunt: 1. Venous blood that empties into the left atrium: Thebesian veins (drains left heart) Bronchiolar veins (drains bronchial circulation) Pleural veins (drains bronchial circulation) ``` 2. Right-to-left shunt due to an intracardiac lesion. 3. AV malformations that develop as a consequence of liver disease.

Answer 50

Expiratory reserve volume decreases Don't you just love it when a question ties a bunch of concepts together? Whenever you see shunt or venous admixture, you should think about FRC. Since FRC is the sum of residual volume and expiratory reserve volume, a reduction in ERV leads to a reduction in FRC. A smaller FRC decreases the amount of pulmonary blood that comes into contact with oxygenated alveoli per unit time. This increases the venous admixture (shunt). In the clinical environment, a smaller FRC explains the faster rate of arterial desaturation during apnea as well as an increased A-a gradient.

Answer 51

20 percent The residual volume is the volume of gas that remains in the lungs after a full exhalation. In the healthy 70 kg adult, the residual volume = 1200 mL and the total lung capacity = 5800 mL. You were asked how RV contributes to the overall percentage of the TLC (1200 mL / 5800 mL = 20%). You must be able to calculate each of the four lung volumes and four lung capacities, and this requires knowing the normal value for each one.

Answer 52

Total Lung volume = IRV + TV + ERV + RV Vital capacity = IRV + TV + ERV Inspiratory capacity = IRV + TV Functional residual capacity = ERV + RV

Answer 53

38 mmHg Don't be intimidated by calculation questions! This one is easy once you understand the concept. Dalton's law of partial pressures says that the sum of the partial pressures of each gas in a mixture equals the total partial pressure of the mixture. P total = P1 + P2 + P3... The atmospheric pressure at sea level is 760 mmHg, so this is the total partial pressure. All you have to do is calculate 5 percent of this number. Atmospheric pressure = 760 mmHg End-tidal CO2 = 5 percent So, what is five percent of 760 mmHg? The correct answer is 38 mmHg. You could also use this same calculation (or use algebraic substitution depending on the variables provided in the stem) if you were asked to calculate the partial pressure or vol% of an anesthetic gas in a container.

Answer 54

0.357 mL/100g/min (we also accepted 0.350) The NCE might ask about normal oxygen consumption as mL/min, mL/kg/min, or mL/100g/min. 1. VO2 as mL/min: The classic answer for a 70 kg adult is 250 mL/min. The classic answer on a per weight basis is 3.5 mL/kg/min. Commit both of these to memory. 2. VO2 as mL/kg/min: If you chose to use 250 mL/min, then simply divide 250 mL/min by the patient's weight (250 mL/min divided 70 kg = 3.57 mL/kg/min). Alternatively, you could've used 3.5 mL/kg/min, since this is the number we told you to memorize. 3. VO2 as mL/100g/min: You'll need to change kg to 100g. 3.57 mL/kg/min = 0.357 mL/100g/min Or ... 3.5 mL/kg/min = 0.350 mL/100g/min

Answer 55

Decreases P50 Shifts the oxyhemoglobin dissociation curve to the left You'll see plenty of questions that require you to apply knowledge from several different subject areas. This is a perfect example. EMLA cream contains prilocaine. Prilocaine is metabolized to o-toluidine. O-toluidine causes methemoglobinemia. Methemoglobin decreases P50 (shifts the oxyhemoglobin dissociation curve to the left). As an aside, methemoglobinemia is treated with IV methylene blue 1-2 mg/kg. By the time you've completed APEX, this type of thinking will become second nature for you.

Answer 56

The Bohr effect describes how changes in acid (PCO2 or H+) alter the carrying capacity of O2 in the blood. It explains why hemoglobin releases O2 at the tissue level and binds O2 in the lungs. Remember bOHr = Oxygen + Hgb. The Haldane effect describes how changes in PO2 in the blood alter the carrying capacity of CO2 in the blood. It explains why venous blood can carry more CO2 than arterial blood. The Hamburger phenomenon describes how Cl- is exchanged for HCO3- to maintain electroneutrality when the erythrocyte acts as a buffer.

Answer 57

J receptor stimulation J receptor stimulation causes tachypnea. These receptors are activated by pulmonary embolism or during pulmonary vascular congestion, such as CHF. The Hering-Breuer inflation reflex stops inspiration when the lungs become hyperinflated. The paradoxical reflex of head causes a newborn baby to take her first breath. The dive reflex causes apnea, bradycardia, and vasoconstriction when the face is submerged in cold water.

Answer 58

Nitroprusside increases venous admixture Hypoxic pulmonary vasoconstriction minimizes shunt by reducing blood flow through poorly ventilated alveoli. A low alveolar PO2 (not arterial PO2) is the trigger that activates HPV. The effect begins almost immediately and reaches its full effect after 15 minutes. ``` Anything that inhibits HPV increases shunt. Examples include: Halogenated anesthetics > 1-1.5 MAC Phosphodiesterase inhibitors Dobutamine Vasodilators IV anesthetics do not inhibit HPV. ```

Answer 59

Increasing peak airway pressure to 40 cm H2O for eight seconds Alveolar recruitment maneuvers (ARMs) are the best way to reverse anesthesia-induced atelectasis. Indeed, increasing peak airway pressure to 30 cm H2O is required for initial reopening, and increasing the PIP to 40 cm H2O for eight seconds appears to reverse anesthesia-induced atelectasis almost completely The application of PEEP reverses atelectasis, but only partially. PEEP should be applied after an ARM in an effort to prevent open airways from collapsing again. Mixing air with oxygen also helps to prevent atelectasis.

Answer 60

FEV1 = 30% Spirometry: There are two key measures that quantify the severity of expiratory airflow obstruction: 1. FEV1 = The volume of air that can be expired in 1 second. Normal = > 80% Severe = < 35% 2. MMEF = Best test of airflow in the medium size airways. Normal = > 75% Severe = < 30% Blood Gases: The PaO2 and PaCO2 change in predictable ways during a severe asthmatic attack. The most common ABG findings during an asthmatic attack are hypocarbia and respiratory alkalosis. CO2 retention usually begins when FEV1 < 25%; this is a sign of impending respiratory failure! Bronchospasm can cause hypoxemia due to V/Q mismatch, but this typically doesn't occur until the FEV1 < 50%.

Answer 61

Montelukast Albuterol is a beta-2 agonist with bronchodilator properties. It is a first-line agent in the setting of acute bronchospasm. Sevoflurane improves bronchospasm in two ways: 1) It has a direct bronchodilator effect, and 2) It deepens the level of anesthesia. If the patient's bronchospasm is so severe that you are absolutely unable to ventilate, you'll need to use an IV agent. Here's where it gets tricky ... There are two key points to understand: Montelukast is NOT used in the treatment for acute bronchospasm. Hydrocortisone IS administered during acute bronchospasm, however it does NOT treat acute symptoms - instead it's given to prevent symptoms down the road. Although there are some investigations examining the use of montelukast for acute bronchospasm, you will not find this agent in the protocols available in the textbooks.

Answer 62

Asthma You do NOT have to memorize every test for every disease process. Instead, just understand the test and understand the disease, and you'll be able to reason your way through the question. The diffusing capacity for carbon monoxide (DLCO) is used to assess how well the lung can exchange gas. This test measures the partial pressure difference between the inspired and expired CO after a known quantity of CO has been inhaled (CO inspired - CO expired = amount of CO that entered the blood). The normal value for DLCO is 17-25 mL/CO/min/mmHg. Lower values correlate with a significant reduction in diffusing capacity. Using Fick's law of diffusion, the DLCO tells us two key characteristics about the alveolocapillary interface: Surface area (decreased by emphysema) Thickness (increased by fibrosis and pulmonary edema) Asthma affects airway diameter, but not the alveolocapillary interface itself. This would affect tests of pulmonary mechanics (FEV1, MMF, etc), but not tests of gas exchange (DLCO).

Answer 63

Decreased airway diameter Polycythemia Higher risk of cor pulmonale You must be able to compare chronic bronchitis with emphysema. Pathophysiology: Chronic bronchitis is caused by inflammation and mucus production that reduce airway diameter. Emphysema is caused by a reduction in the surface area of the alveolocapillary interface and loss of elastic recoil. Blood Gases: The patient with chronic bronchitis is polycythemic; an increased RBC mass compensates for a chronically low PaO2. They tend to retain CO2. We call them "blue bloaters.” The patient with emphysema generally has a normal (or slightly reduced) PaO2. The PaCO2 is usually normal or decreased (as a result of hyperventilation). We call them "pink puffers." Cor Pulmonale: This complication is more common with chronic bronchitis, generally as a result of pulmonary hypertension. Chronic alveolar hypoxia causes pulmonary vasoconstriction, and this increases pulmonary vascular resistance. In consequence, the workload of the right ventricle increases, leading to RV hypertrophy (right axis deviation) and ultimately RV failure.

Answer 64

Dexmedetomidine Cor pulmonale is always the result of pulmonary hypertension. An increased PVR increases the workload of the right heart, and this leads to RV hypertrophy and ultimately RV failure. Therefore, anesthetic management specifically avoids anything that increases PVR. Anesthetic goals for the patient with pulmonary hypertension includes the avoidance of: ``` Hypoxia Acidosis Hypercarbia Hypothermia Nitrous oxide Vasoconstrictors Conditions that increase SNS tone Ketamine (maybe) Other IV anesthetic agents are safe to use. Because dexmedetomidine doesn't cause respiratory depression, it won't cause hypercarbia. This makes it an attractive drug in this patient population. ``` Regional anesthesia is safe, unless a high sensory level is required during neuraxial blockade. A decreased SVR in the setting of a fixed PVR can lead to profound hypotension.

Answer 65

Increased pulmonary artery occlusion pressure Cor pulmonale is right-sided heart failure that results from pulmonary hypertension (increased PAP and normal PAOP). This creates a back pressure on the venous circulation that leads to: ``` Jugular venous distension Hepatomegaly Lower extremity edema An increased PAOP is consistent with LV (not RV) failure. ```

Answer 66

End-tidal carbon dioxide Pulmonary embolism prevents blood in the affected vessels from reaching the alveoli. Said another way, these alveoli are ventilated and not perfused, so they become dead space. Because end-tidal gas is a mixture of gas from perfused alveoli and alveoli lacking perfusion, it is diluted and the EtCO2 decreases. By extension, the PaCO2 to EtCO2 gradient increases. Large emboli can plug the main pulmonary arterial vessels, and this can increase PVR and right ventricular work. In extreme cases, this can progress to RV failure and tricuspid regurgitation. Tachycardia and tachypnea are common findings in the patient with PE.

Answer 67

Positive end-expiratory pressure This risk of aspiration pneumonitis is increased in patients with Mendelson syndrome. This is characterized by a gastric volume > 25 mL and gastric pH < 2.5. Here is the pathophysiology and treatment for the patient who has aspirated gastric contents. Immediately After Aspiration: Because chemical injury to the lung tissue occurs immediately after the insult, there is no need for deep tracheal suctioning or bronchoscopy. Suctioning the mouth and pharynx for particulate matter is useful. Minutes After Aspiration: Atelectasis increases pulmonary shunt. Indeed, hypoxemia is the hallmark sign of aspiration pneumonitis. In fact, it is often the first sign. PEEP is indicated to reduce shunt. Hours After Aspiration The inflammatory response takes hold within hours. Macrophages release cytokines and tumor necrosis factor-alpha. Neutrophils release proteases and oxygen free radicals. Collectively these chemicals lead to non-cardiogenic pulmonary edema. Lidocaine reduces free radical production, inhibits neutrophil chemotaxis, minimizes reperfusion injury, and improves outcomes in patients with aspiration pneumonitis. Steroids are of questionable benefit. A Day After Aspiration: Necrosis of alveolar cells occurs within 24 hours. Two Days After Aspiration: Antibiotics are only indicated if fever or an increased WBC count persist for more than 48 hours.

Answer 68

Tidal volume 6 mL/kg and respiratory rate = 16 breaths/min As a general rule, restrictive lung disease is associated with a reduction in all lung volumes and decreased lung compliance. Expiratory flow rates remain normal. The best ventilatory strategy for restrictive lung disease aims to minimize the risk of barotrauma. This is best accomplished with a smaller tidal volume (6 mL/kg IBW) and faster respiratory rate (14-18 breaths/min). Maintaining peak inspiratory pressure < 30 cm H2O also minimizes the risk of barotrauma.

Answer 69

Pulmonary edema Pneumonia ``` There are five causes of hypoxemia. For each of these, you must know how the A-a gradient is affected, if the condition responds to supplemental oxygen, and be able to identify examples. 1. High altitude A-a gradiant = normal O2 helpful = yes Example = low barometric pressure 2. Hypoventilation A-a gradient = normal O2 helpful = yes Example = low PAO2, opioid overdose 3. Diffusion defect A-a gradient = increased O2 helpful = yes Example = pulmonary fibrosis 4. V/Q mismatch A-a gradient = increased O2 helpful = yes Example = dead space, shunt ``` 5. Right to left shunt A-a gradient = increased O2 helpful = no (if shunt > ~ 30%) Example = VSD, Tetralogy of Fallot, VSD, Eisenmenger syndrome

Answer 70

Negative pressure pulmonary edema Restrictive lung diseases can be divided into categories: Acute intrinsic: negative pressure pulmonary edema Chronic intrinsic: Amiodarone induced pulmonary fibrosis Disease of chest wall/mediastinum: Ankylosing spondylitis Other/increased intraabdominal pressure: Pregnancy

Answer 71

Esophageal resection Isolation of one lung to prevent infection: Massive pulmonary hemorrhage Infection Control of distribution of ventilation: Bronchopleural fistula Surgical opening of a major airway Large unilateral lung cyst or fistula Unilateral bronchopulmonary lavage: Pulmonary alveolar proteinosis Surgical exposure can be of high or low priority, but it is always a relative indication for one lung ventilation. Esophageal resection is a low priority procedure.

Answer 72

Inward during inspiration Outward during expiration Flail chest is a consequence of chest trauma with multiple rib fractures. The key characteristic is paradoxical movement of the chest wall at the site of the fractures. Inspiration (Negative Intrathoracic Pressure) Normal: The chest wall moves outward and lungs expand. Flail chest: The injured ribs move inward and collapses affected region. Expiration (Positive Intrathoracic Pressure) Normal: The chest wall moves inward and lungs empty. Flail chest: The injured ribs move outward and affected region doesn't empty.Since part of the lung isn’t moving normally, it doesn’t participate in gas exchange. Consequences include alveolar collapse, hypoxemia, hypoventilation, and hypercarbia. Treatment includes reducing pain with an epidural catheter or intercostal nerve blocks. Remember, this area is highly vascular and that the rate of local anesthetic uptake into the systemic circulation is high.

Answer 73

1:3 The patient with severe COPD experiences gas trapping (increased alveolar time constant). Therefore, your ventilatory strategy must allow ample time for exhalation to occur. Increasing the expiratory time minimizes air trapping and dynamic hyperinflation. If you are using volume cycled ventilation, know that this comes at the cost of a higher peak inspiratory pressure (you have less time to get the same volume of gas into the patient).

Answer 74

Montelukast + Leukotriene antagonist Theophylline + Phosphodiesterase inhibitor Cromolyn + Mast cell stabilizer Ipratropium + Anticholinergic

Answer 75

Hypoventilation Acidosis impairs the ability of the body's enzymatic systems to function properly. This is exemplified by the presence of respiratory acidosis and reversal of neuromuscular blockers. Anticholinesterases inhibit acetylcholinesterase, which increases the concentration of Ach in the synaptic cleft at the neuromuscular junction. It is the ratio of Ach and NMB at the neuromuscular junction that determines the quality of the reversal. An inadequate reversal leads to respiratory muscle weakness, hypoventilation, and respiratory acidosis. This potentiates the NMB and reduces the efficacy of the anticholinesterase, creating a self-perpetuating cycle of increasing respiratory muscle weakness. Don’t forget that the benzylisoquinolines are metabolized by Hofmann elimination (cisatracurium 100% and atracurium 33%). This reaction is slowed in the patient with respiratory acidosis, thereby prolonging the duration of action for these drugs. Respiratory acidosis can also cause myocardial depression. As an aside, you'll find a question very similar to this on the 2015 version of the National Certification Examination Handbook. You would be wise to analyze the questions in that document.

Answer 76

VO2 max = 8 mL O2/kg/min Assessment of respiratory reserve can be divided into 3 key areas: respiratory mechanics, gas exchange, and cardiopulmonary reserve. ``` 1. Respiratory Mechanics: The ability to move gas in and out of the lungs FEV1 < 40% (best measurement) 2. Gas Exchange: The ability to transfer O2 and CO2 across the alveolocapillary interface DLCO < 40% predicted (best measurement) PaO2 < 60 mmHg PaCO2 > 45 mmHg 3. Cardiorespiratory Interaction: ``` The ability of the lungs and heart to work together to maintain PaO2 and PaCO2 VO2 max < 15 mL O2/kg/min (best measurement) Unable to climb 1 flight of stairs SpO2 decreases > 4% during exercise Of all of the tests mentioned above, the single best predictor of postoperative pulmonary complications is VO2 max. In addition to lung function, hypoalbuminemia (<3.6 g/dL) is also a predictor of PPC. You may think that this list is too specific to memorize, but trust us when we say that it’s not!

Answer 77

When the anesthetized patient is placed in the lateral decubitus position: The nondependent lung moves from the flat (noncompliant) region of the curve to an area of better compliance. Ventilation is best here, because the lung is on a favorable position of the curve.

Answer 78

Apply positive end-expiratory pressure to the dependent lung Hypoxemia during OLV is the result of intrapulmonary shunt. The most important predictor of PaO2 during OLV is the PaO2 during two-lung ventilation. Strategies for reversing hypoxemia during OLV: Increase FiO2 to 100% Check the DLT position with a fiberoptic bronchoscope. Apply CPAP 10 cm H2O to the non-dependent lung (this can impede visualization during VATS). Apply PEEP 5-10 cm H2O to the dependent lung. Ligate or clamp the pulmonary artery of the non-dependent lung (not always possible). Resume two-lung ventilation. As an aside, insufflating oxygen at 5 L/min into the non-dependent lung can be a very effective method to increase PaO2 without obscuring surgical visualization.

Answer 79

Three liters in 24 hours During OLV, the dependent lung must perform all of the gas exchange functions. Excessive crystalloid administration increases hydrostatic pressure, which increases interstitial lung water and impairs gas exchange. In the patient scheduled for pneumonectomy, the dependence on a single lung continues into the postoperative period as well. For this reason, it’s best to limit crystalloid to replacement of volume deficits and maintenance requirements (no third space). It’s recommended to limit crystalloids to < 3L in the first 24 hours.

Answer 80

Right arm Mediastinoscopy is performed to diagnose and stage lung cancer. The most common approach involves a small incision made at the midline of the lower neck at the suprasternal notch. The scope is placed anterior to the trachea and posterior to the innominate artery artery and thoracic aorta. Because this region is rich in high value real estate, there are a number of serious complications that can result: Thoracic aorta (hemorrhage and reflex bradycardia) Innominate artery (decreased carotid blood flow and cerebral blood flow) Tracheal (airway obstruction) Vena cava (hemorrhage) Lung (tension pneumothorax) Thoracic duct (chylothorax) Phrenic and recurrent laryngeal nerve (paresis) The right common carotid and right subclavian arteries branch off the innominate artery. Compression of the innominate artery impairs perfusion of the brain as well as the right upper extremity. For this reason, you must continuously monitor the pulse in the right upper extremity while the mediastinoscope is inside the patient. This can be accomplished with an arterial line, SpO2 probe, or even your finger. A blood pressure cuff is placed on the left arm to monitor systemic blood pressure in the event of innominate compression. Another name for the innominate artery is the brachiocephalic artery.

Answer 81

Apple juice = 2 hours Breast milk = 4 hours Cow's milk = 6 hours The Practice Guidelines for Preoperative Fasting and Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration have been updated since their original publication in 1999. Here are the most current recommendations: 2 hours = Clear liquids 4 hours = Breast milk 6 hours = Nonhuman milk, infant formula, solid food Miller states that ingestion of fried and fatty foods "may" require eight hours or more. Ingestion of clear liquids two hours before surgery reduces gastric volume and increases gastric pH. Both of these reduce the risk of Mendelson syndrome.

Answer 82

Three The Mallampati score is used to assess the size of the tongue relative to the volume of the mouth. The more space the tongue occupies, the less space there is to work To perform the exam, the patient should sit upright, extend the neck, open the mouth as wide as possible, and stick out the tongue. The patient should not phonate. Remember the mnemonic: PUSH Class I: Pillars, Uvula, Soft palate, Hard palate Class II: __ Uvula, Soft palate, Hard palate Class III: __ __ Soft palate, Hard palate Class IV: __ __ __ Hard palate By itself, the MMT is a poor predictor of difficult airway, however its predictive power increases substantially as it is combined with additional airway tests.

Answer 83

Edentulousness History of snoring Presence of a beard You must know the independent risk factors that predict difficult mask ventilation. The mnemonic "BONES" should help: ``` Beard (odds ratio = 3.18) Obese (odds ratio = 2.75) No teeth (odds ratio = 2.28) Elderly (odds ratio = 2.26) Snoring (odds ratio = 1.84) ```

Answer 84

Arched palate Long upper incisors Mandibular protrusion test class three Predictors of difficult laryngoscopy include: Small mouth opening Prominent overbite / retrognathic jaw (short jaw) Inability to bite upper lip with lower teeth (mandibular protrusion test class three) Long incisors Mallampati class three or four High, arched palate Short, thick neck Short thyromental distance Reduced cervical mobility The Cormack-Lehane grading system is used to measure the view you obtain during laryngoscopy. A class four means that you cannot see the epiglottis or any of the glottic structures. This IS a difficult airway and NOT a predictor of a difficult airway!

Answer 85

Tip of the nose How to size an oropharyngeal airway: Measure the distance between the corner of the patient's mouth and the earlobe or the angle of the mandible. An incorrectly sized OPA can worsen airway obstruction.

Answer 86

Light anesthesia The lightly anesthetized patient is more tolerant of a nasopharyngeal airway than he is of an oropharyngeal airway. In fact, an oropharyngeal airway in a lightly anesthetized patient can precipitate laryngospasm. Contraindications to an NPA include: ``` Coagulopathy (risk of epistaxis) Basilar skull fracture LeFort II or III fracture Nasal fracture CSF rhinorrhea Previous transsphenoidal hypophysectomy Previous Caldwell-Luc procedure ```

Answer 87

Oral Pharyngeal Laryngeal Head elevation and head extension aim to align the oral, pharyngeal, and laryngeal axes. This offers the greatest chance for successful laryngoscopy and intubation. Problems with other positions: Head in the neutral position does not align any of these axis. Head elevated on a pad with head in the neutral position only aligns the PA and LA. Head on the bed with head extension only aligns the PA and LA.

Answer 88

Endotracheal tube visualized between the vocal cords You were probably hoping to see (+) EtCO2 for three consecutive breaths, huh? Remember, your job is the identify the best answer choice of those provided in the question - these may not always align with your expectations. According to Hagberg, the two most reliable signs of endotracheal intubation are: Visualizing the ETT between the vocal cords. Fiberoptic visualization of the tracheal rings with a fiberoptic bronchoscope. Notice that both of these provide direct, visual proof of successful intubation. We know what you're thinking - what about the presence of carbon dioxide on the capnograph? While (+) EtCO2 for three breaths is reliable most of the time, there a few circumstances that will yield a false-negative result. These situations include cardiac arrest, severe bronchospasm, complete ETT obstruction (kinking or plugging), and equipment malfunction. Bilateral breath sounds, chest rise and fall, and mist in the endotracheal tube are less reliable than the presence of CO2 on the capnograph or the methods of direct visualization described above.

Answer 89

Oral ETT in women = 21 cm Oral ETT in men = 23 cm Nasal ETT in women = 25 cm Nasal ETT in men = 27 cm

Answer 90

Flexion We're going to make this really easy to remember; the tube goes where the nose goes. Flexion moves the tip towards the carina (~ 2 cm). Extension moves the tip away from the carina (~ 2 cm). Lateral rotation of the head moves the tip away the carina (~ 0.7 cm). Another thing to keep in mind is the position of the bed. The steep Trendelenburg position causes the abdominal contents to shift towards the chest, reduce thoracic volume, and cause endobronchial intubation.

Answer 91

Glossopharyngeal During laryngoscopy with the Macintosh blade, the tip of the blade is placed in the vallecula. You should be able to identify this on a hotspot-type question as well. Airway innervation from proximal to distal: Anterior tongue: Trigeminal (V) V3 - mandibular branch Posterior tongue: Glossopharyngeal (IX) Soft palate: Glossopharyngeal (IX) Oropharynx: Glossopharyngeal (IX) Vallecula: Glossopharyngeal (IX) Anterior epiglottis: Glossopharyngeal (IX) Posterior epiglottis: Superior laryngeal internal branch (X) Vocal cords: Superior laryngeal internal branch (X) and recurrent laryngeal (X) Trachea: Recurrent laryngeal (X)

Answer 92

60 cm H2O While the maximum cuff pressure for an endotracheal tube is 25 cm H2O, the maximum cuff pressure for an LMA is 60 cm H2O (target pressure 40 - 60 cm H2O). Excessive cuff pressure (LMA or ETT) can cause nerve injury and is associated with a higher incidence of sore throat Cuff pressures should be measured periodically throughout the anesthetic, particularly if nitrous oxide is used.

Answer 93

Correct placement and appropriate sizing The LMA Classic is a small mask that covers the laryngeal inlet. It is inflated to permit positive pressure ventilation up to 20 cm H2O. The integrity of the seal is more dependent on correct placement and appropriate sizing and less dependent on cuff volume or pressure. The LMA cuff pressure should never exceed 60 cm H2O. If the pressure is this high and you are unable to generate an adequate seal, then the LMA may be improperly positioned, the patient is inadequately anesthetized, and/or there is a partial or complete laryngospasm. Remember that nitrous oxide diffuses into the cuff, and this will increase cuff pressure (Boyle's law). You must periodically measure cuff pressure with a monometer when N2O is used.

Answer 94

2.5 This is a two part question; convert the weight to kg then answer the question 1. 54 / 2.2 = 24.5 kg 2. LMA-Classic size = 2.5 ``` Patient Size = LMA-Classic Size < 5 kg = 1 5 - 10 kg = 1.5 10 - 20 kg = 2 20 - 30 kg = 2.5 30 - 50 kg = 3 50 - 70 kg = 4 70 - 100 kg = 5 > 100 kg = 6 ```

Answer 95

4.5 While some may say that the largest size endotracheal tube that passes through an LMA is the "one that fits," we argue that knowing this information helps you get it right the first time and it may even get you points on boards. ``` LMA-Class Size / Largest ETT that fits: 1 = 3.5 1.5 = 4.0 2 = 4.5 2.5 = 5.0 3 = 6.0 cuffed 4 = 6.0 cuffed 5 = 7.0 cuffed 6 = 7.0 cuffed ```

Answer 96

Cuff pressure = 50 cm H2O Complications of LMA use include: Nerve injury: recurrent laryngeal, hypoglossal, lingual Pharyngeal necrosis Trauma to the uvula Sore throat Conditions that can increase the risk of complications include: LMA is too small Nitrous oxide (if cuff pressure isn't monitored throughout the procedure) Non-supine positions

Answer 97

Laryngeal mask airway We all know that direct vision laryngoscopy is an intensely stimulating procedure that can lead to increased catecholamines, tachycardia, hypertension, dysrhythmias, bronchorrhea and bronchospasm. Interestingly, combitube placement may be even more stimulating. The tendency of airway device placement to activate the SNS (from most activation to least activation): Combitube DVL Fiberoptic intubation LMA

Answer 98

Esophagus The Combitube is a supraglottic, double lumen device that is blindly placed in the hypopharynx. The proximal balloon occludes the hypopharynx, while the distal balloon occludes the esophagus. If the tip is placed in the esophagus (this is common), the lungs can be ventilated through the lumen between the distal and proximal balloons. It is uncommon that the tip is positioned in the trachea, but if you get lucky, the distal lumen can be used for ventilation. Pathology at or below the larynx may render this device useless. Esophageal rupture has been reported. Cricoid pressure should be released (not maintained) when placing the Combitube.

Answer 99

Pass the endotracheal tube off of the lighted stylet The trachea is anterior to the esophagus. Placement of the lighted stylet into the trachea results in a "well-defined circumscribed glow" below the thyroid prominence. This is what you saw in the image. If the lighted stylet was in the esophagus, you would observe a "more diffuse transillumination of the neck without the circumscribed glow." Benefits of the lighted stylet: Useful for the anterior airway. Useful with small mouth opening. Requires very little manipulation of the neck. Less stimulating than direct vision laryngoscopy. Less sore throat than direct vision laryngoscopy. We want you to notice the difference between: Esophageal placement = diffuse transillumination of the neck without the circumscribed glow Tracheal placement = well defined circumscribed glow just below the thyroid prominence

Answer 100

It should be bent at a less acute angle This question requires you to draw on your knowledge of the pediatric airway to answer it correctly. When using the Trachlight in the adult, it should be bent to a 90 degree angle. When using this device in children, the angle should be 60-80 degrees (more acute angle) to better accommodate a more cephalad glottic opening. Since the pediatric airway is smaller, the Trachlight should be bent closer to the tip. For the same reason, you should expect that transillumination will occur sooner. Because of the thinner neck in the child, the circumferential glow will be more prominent. It's possible that there are more false positive results (you think the tip is in the tracheal when it is really in the esophagus).

Answer 101

Age less than six years old The only absolute contraindication to cricothyroidotomy is young age (Hagberg says age < 10 years). Children have pliable and mobile laryngeal and cricoid cartilages, and this can make cricothyroidotomy incredibly challenging. In this age group, percutaneous transtracheal ventilation is the surgical airway technique of choice. Cricothyroidotomy is useful when facial trauma impairs conventional airway management methods. An unstable c-spine is ok, so long as cervical spine immobilization is employed. A neck burn injury can make landmark identification more difficult, however it is not a contraindication. Hagberg notes that some people argue that laryngeal fracture and transection should be considered absolute contraindications, but there is some disagreement on this.

Answer 102

Fiberoptic bronchoscopy and blind nasal intubation Based on cineradiography data, fiberoptic bronchoscopy and blind nasal intubation are associated with less cervical motion than other intubation techniques. Of the two, FOB is favored with c-spine injury due to a lower risk of trauma and a higher success rate. It should be noted that these techniques are not necessarily associated with a lower incidence of neurologic deficits.

Answer 103

Cervical spine injury Retrograde intubation involves puncturing the cricothyroid membrane and passing a wire between the vocal cords and out of the mouth. Next, an endotracheal tube is loaded over the wire and advanced into the trachea. Most of the reported cases of retrograde intubation described its use in patients with cervical spine injuries. Contraindications to retrograde intubation: A neck flexion deformity can make this procedure challenging if not impossible. Obesity or the presence of a goiter may prevent you from accurately identifying the cricothyroid membrane. Coagulopathy increases the risk of bleeding into the airway following needle puncture. Placing a needle through a pretracheal abscess can cause a respiratory infection.

Answer 104

``` 1 = Remove the stylet 2 = Rotate the DLT 90 degrees 3 = Advance the DLT into the bronchus 4 = Confirm placement with fiberoptic bronchoscope ``` After the tip is placed between the vocal cords, you should: Remove the stylet to avoid mucosal damage. Rotate the DLT 90 degrees in the direction of the bronchus to be intubated. Advance the tube to 29 cm in males and 27 cm in females at the teeth. Stop if you encounter resistance. Fill the tracheal cuff with 5-10 mL of air and the bronchial cuff with 1-2 mL of air. Be aware that the bronchial balloon is a low volume and high pressure cuff - keep it deflated when you don't need lung separation. Auscultation is not the most reliable method of determining correct placement. Confirm placement with a fiberoptic bronchoscope.

Answer 105

Flexible fiberoptic bronchoscope with patient awake and spontaneous ventilation Flexible fiberoptic bronchoscopy in the awake, spontaneously ventilating patient is the gold standard for managing the difficult airway. There is nothing else to say about this.

Answer 106

Step 1 = Remove the endotracheal tube Step 2 = Stop flow of all airway gases Step 3 = Pour saline into the airway Step 4 = Re-establish ventilation You will find debate as to whether you should remove the endotracheal tube or turn off the oxygen as the first step. In reality, you're doing many steps simultaneously, however on the NCE there is a specific order of steps. Miller cites the ASA Operating Room Fire Guidelines. We made sure to reconcile this text with the guidelines. ``` Fire is present: 1. Remove the endotracheal tube. 2. Stop flow of all airway gases. 3. Remove other flammable material from the airway. 4. Pour saline into the airway. 5. If fire not extinguished on first attempt, use a CO2 fire extinguisher. Fire is controlled: ``` 1. Re-establish ventilation by mask. Avoid supplemental O2 or N2O. 2. Check ETT for damage - fragments may remain in the airway. 3. Bronchoscopy to assess the injury and retained ETT fragments.

Answer 107

By measuring the size of the tongue relative to the volume of the mouth, the Mallampati exam helps us predict the difficulty of endotracheal intubation. ``` To perform the exam, the patient should: Sit upright Extend the neck Open the mouth as wide as possible Stick out the tongue NOT phonate ``` This patient has a class I airway, because you can visualize the tonsillar pillars.

Answer 108

3 The Cormack and Lehane grading system helps us measure the view we obtain during direct vision laryngoscopy. Be sure to understand what you can and cannot see with each score.

Answer 109

Old age Edentulousness Presence of a beard You must know the independent risk factors for difficult mask ventilation. The mnemonic "BONES" should help: ``` Beard Obese (most books say BMI > 26 kg/m2) No teeth Elderly (age > 55 years) Snoring ``` The distractors are predictors of difficult endotracheal intubation - not mask ventilation.

Answer 110

Goldenhar Klippel-Feil You must know the congenital conditions that are associated with cervical spine anomalies. Examples include: Goldenhar Klippel-Feil Trisomy 21

Answer 111

Cervical flexion and atlanto-occipital joint extension The sniffing position maximizes the probability of successful tracheal intubation by aligning the oral, pharyngeal, and laryngeal axes. It consists of 2 key elements: Cervical flexion: Moves the chin to the chest Atlanto-occipital joint extension: Extends the head on the neck

Answer 112

Coagulopathy Le Fort II fracture The turbinates are highly vascular structures. Instrumenting the nose places the patient at risk for epistaxis, which can complicate airway management. Coagulopathy makes this more likely. Le Fort II and III fractures can disrupt the cribriform plate, creating a direct line of communication between the nasal and cranial cavities. Placing a nasal airway, nasal ETT, or NGT could be catastrophic. Signs of cribriform plate injury include “raccoon eyes,” periorbital edema, and/or CSF leak in the nose or ears.

Answer 113

Attach a monometer to the pilot balloon Inflating the ETT cuff creates a seal that permits positive pressure ventilation and protects the lungs from aspiration of gastric contents. Tracheal ischemia can occur if the cuff pressure exceeds tracheal mucosal perfusion pressure. For this reason, the cuff pressure should be less than 25 cm H2O. Attaching a manometer to the pilot balloon is the best way to determine the pressure inside the cuff.

Answer 114

Distal end → Upper esophageal sphincter (cricopharyngeus muscle) Sides → Pyriform sinuses Proximal end → Base of the tongue

Answer 115

LMA ProSeal + Gastric drain LMA Fastrach + Designed for tracheal intubation LMA Flexible + Wire-reinforced airway tube

Answer 116

Asthma You need to know when you can use a particular device and when you can't (or shouldn't). Compared to an endotracheal tube, an LMA produces considerably less airway irritation making it a suitable choice in the asthmatic patient. Although the LMA shields the larynx from oropharyngeal secretions, it does NOT provide a secure airway. Therefore, it is contraindicated in any patient with a full stomach (gastroparesis or hiatal hernia). An LMA is also contraindicated if there is an airway obstruction at or below the level of the glottis (tracheal tumor).

Answer 117

Intact gag reflex Prolonged use Zenker’s diverticulum The Combitube is a supraglottic, double lumen device that is blindly placed in the hypopharynx. Contraindications to its use include: Intact gag reflex Prolonged use (> 2 - 3 hours) due to risk or ischemia from oropharyngeal balloon Esophageal disease (Zenker’s diverticulum) Ingestion of caustic substances Do not use a size 37-F in someone < 4 ft Do not use a size 41-F in someone < 6 ft It provides a secure airway, so it is a useful alternative in the patient with a full stomach. Additionally, placement does not require neck extension, so it’s useful in the patient with Klippel-Feil syndrome.

Answer 118

Pushing the lever down, points the tip up The non-dominant hand controls the lever Flexible fiberoptic bronchoscopy in the awake, spontaneously ventilating patient is the gold standard for managing the difficult airway. One of the downsides of FOB under general anesthesia is loss of pharyngeal tone and upper airway obstruction. If the patient requires PPV, then a special adapter can be placed between the mask and the y-piece. This will allow you to provide positive pressure ventilation while the FOB is in the patient’s airway. The dominant hand holds the cord. The non-dominant hand holds the scope near the proximal end, where the thumb controls the lever. Pushing the lever down, points the tip up. Pushing the lever up, points the tip down. Rotating the scope left or right allows you to control the scope in the horizontal plane.

Answer 119

It requires a minimum mouth opening 7 millimeters It is useful in the patient with Pierre Robin syndrome The Bullard laryngoscope is a rigid, fiberoptic device used for indirect laryngoscopy. For this reason, the oral, pharyngeal, and laryngeal axes do not have to align. It is useful in the patient with: Small mandible (Pierre-Robin syndrome) Limited mouth opening (requires at least 7 mm) Limited cervical mobility There is a disposable tip extender that is useful for tall patients. It snaps in place before laryngoscopy and it must be removed and discarded after laryngoscopy.

Answer 120

Remember the Cormack and Lehane grading system? The Eschmann introducer provides the most significant benefit when you obtain a grade III view during laryngoscopy. Before moving on, what are some other names for the Eschmann introducer?

Answer 121

Microstomia Mandibular hypoplasia Severe oropharyngeal bleeding The lighted stylet is a blind technique that transilluminates the anterior neck to facilitate endotracheal intubation. Like other indirect intubation methods (FOB and Bullard), the lighted stylet is useful in the patient with microstomia (small mouth) and/or mandibular hypoplasia. Unlike the FOB and Bullard that use a camera to visualize the larynx, the lighted stylet is a blind technique. Therefore, it is also useful in the patient with severe oropharyngeal bleeding that would otherwise obscure a camera. The lighted stylet is not useful in the following situations: Super morbid obesity (excess neck tissue impairs transillumination) Epiglottitis (the lighted stylet can injure the epiglottis and worsen airwayobstruction) A can’t ventilate and can’t intubate scenario (and LMA or invasive airway is a better choice)

Answer 122

Prevent contamination from contralateral lung infection Provide ventilation of the isolated lung Be used to suction secretions from the isolated lung The bronchial blocker is an alternative to the double lumen endotracheal tube. You must understand the similarities and differences between both. Unlike the DLT, the bronchial blocker cannot: Prevent contamination from contralateral lung infection. Provide ventilation to the isolated lung. Be used to suction secretions from the isolated lung. Unlike the bronchial blocker, the DLT cannot: Provide lung separation in children < 8 - 10 years old. Provide lung separation for the patient requiring nasotracheal intubation. Both the DLT and bronchial blocker allow you to insufflate oxygen into the isolated lung.

Answer 123

Just like cricothyroidotomy, retrograde intubation requires you to penetrate the cricothyroid membrane.

Answer 124

Transtracheal jet ventilation + Upper airway obstruction Cricothyroidotomy + Patient age less than 6 years Tracheostomy + No absolute contraindication

Answer 125

Asthma Coronary artery disease Pros of deep extubation include: Decreased CV and SNS stimulation (desirable with CAD) Decreased coughing and airway irritation (desirable with asthma) Cons of deep extubation include: Ineffective airway reflexes Increased risk of airway obstruction (caution with obstructive sleep apnea) Increased risk of aspiration (caution with Parkinson’s disease)

Answer 126

Airway exchange catheter The airway exchange catheter is a long, thin, flexible, hollow tube that maintains direct access to the airway following tracheal extubation. It is the most common device used to manage extubation of the difficult airway. A nasal airway may be helpful in the patient at risk for failed extubation, but it is not the best choice presented in the question. The Shikani stylet is a cross between a lighted stylet and a FOB. It is used for intubation. The Eschmann introducer is also used during intubation.