APEX Anesthesia: Unit 1 Respiratory

Risk factors for difficult intubation 1. Small mouth opening 2. Narrow palate w/ high arch 3. Long upper incisors 4. Interincisor distance <3cm 5. Mallampati class 3 or 4 6. Mandibular protrusion test class 3 7. Poor compliance of submandibular space 8. Thyromental distance (<6cm or 9 cm) 9. Short and thick neck 10. Poor AOJ mobility (cannot extend neck or touch chin to chest)

10 risk factors for difficult intubation

Aspiration pneumonitis risk factors: 1. Trauma 2. Emergency surgery 3. Pregnancy 4. GI Obstruction 5. GERD 6. Peptic ulcer dz 7. Hiatal hernia 8. Ascites 9. Difficult airway mngmt 10. Cricoid pressure 11. Impaired airway reflexes 12. Head injury 13. Sz 14. Residual NMB

14 Risk factors for aspiration pneumonitis.

Risk factors for difficult LMA 1. Limited mouth opening 2. Upper airway obstruction (prevents passage of device into pharynx) 3. Altered pharyngeal anatomy (prevents seal) 4. Poor airway compliance (requires excessive PIP) 5. Increased airway resistance (requires excessive PIP) 6. Lower airway obstruction

6 risk factors for difficult supraglottic device placement.

Laryngospasm tx - 100% FiO2 - Remove noxious stimuli - Deepen anesthesia - CPAP 15-20cmH2O - Open airway (head extension, chin lift) - Larson's maneuver - Sux** **Infants/small kids should also get 0.02 mg/kg atropine with sux! If Sux is not possible, roc is the only other NMBD that can be given IM. **If no IV, submental sux will produce fastest onset!

7 Laryngospasm treatments

Impaired AOJ mobility d/t 1. Degenerative joint dz 2. Rheumatic arthritis 3. Ankylosing spondylitis 4. Trauma 5. Surgical fixation 6. Klippel-Feil 7. Down syndrome

7 conditions that impair atlanto-occipital joint mobility.

Aspiration Tx 1. Tilt head down or to the side (1st action!) 2. Upper airway suction to remove particulates 3. Lower airway suction to remove particulates; does NOT help chemical burn from gastric acid 4. Secure airway to support oxygenation 5. PEEP to reduce shunting 6. Bronchodilators to reduce wheezing 7. Lidocaine to reduce neutrophil response 8. Antibiotics (only if pt develops a fever or ↑WBC count >48 hours) *Steroid probably do NOT help.

8 Treatments of aspiration.

Acute bronchospasm tx 1. 100% FiO2 2. Deepen anesthetic (gas, propofol, ketamine, lido) 3. Albuterol (β2 agonist) 4. Ipratropium (anticholinergic) 5. Epi 1 mcg/kg IV 6. Aminophylline 7. Helium-O2 (Heliox): ↓ airway resistance (↓Reynold's #) 8. Hydrocortisone 2-4 mg/kg IV: onset is several hours! *Montelukast is NOT a treatment.

8 Tx for acute bronchospasm

Alveolar gas equation tells us that hypoventilation can cause hypercarbia and hypoxemia. It explains how supplemental O2 reverses hypoxemia but NOT hypercarbia. PAO2 = FiO2 x (Pb-PH2O) - (PaCO2/RQ) Pb: Atm pressure PH2O: 47 mmHg RQ (Respiratory quotient) = (CO2 elimination/O2 consumption) = 200mL/250mL = 0.8 *Alveolar oxygen in the healthy adult breathing RA at sea level is 105.98mmHg.

Alveolar gas equation.

An 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. You are able to: - ETCO2 measurement - Jet ventilation (via Luer-lock adapter) - O2 insufflation (via 15mm adapter)

Best time to use an airway exchange catheter? What can you do with it? (3)

PulmHTN is mean PAP > 25mmHg. Causes: COPD, left-sided ❤︎ dz, connective tissue disorders Goals: Optimize Pulm Vascular Resistance ▪︎↑PVR - Hypoxemia - Hypercarbia - Acidosis - SNS stimulation - Pain - Hypothermia - ↑intrathoracic pressure: PEEP, atelectasis, mechanical ventilation - Drugs: Nitrous oxide, Ketamine, Desflurane ▪︎↓PVR - ↑PaO2 - Hypocarbia - Alkalosis - ↓intrathoracic pressure: prevent cough/strain, normal lung volumes, spontaneous ventilation, high frequency jet ventilation - Drugs: Inhaled nitric oxide, nitroglycerin, PDEi's (Sildenafil), PGE1 and PGE2, CCBs, ACEi's *The pt w/ cor pulmonale (R❤︎ failure) is also sensitive to ↑PVR, so keep these same principles in mind.

Define pulmonary HTN. - 3 Causes? - Goals of anesthetic mngmt?

TLC = TV + IRV + ERV + RV = 5800mL VC = IRV + TV + ERV = 4500mL IC = IRV + TV = 3500mL FRC = ERV + RV = 2300mL CC = RV + CV = Variable *Closing Capacity

Define the 5 lung capacities. How much volume is in each?

IRV = 3000mL (amount that can be forcibly inhaled after tidal inhalation) TV = 500mL (amount during normal breath) ERV = 1100mL (amount that can be forcibly exhaled after tidal exhalation) RV = 1200mL (volume remaining in lungs after complete exhalation; cannot be exhaled from the lungs. serves as O2 reservoir during apnea) CV = variable (volume above RV where the small airways begin to close) *Closing volume

Define the 5 lung volumes. How much volume is in each?

Mallampati exam assess the oropharyngeal space (size of tongue relative to volume in mouth). 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

Describe Mallampati scoring system.

Zone 1 - PA > Pa > Pv - Dead space - Ventilation w/o perfusion Zone 2 - Pa > PA > Pv - Waterfall - Normal physiology Zone 3 - Pa > Pv > PA - Shunting - Perfusion w/o ventilation Zone 4 - Pa > Pist > Pv > PA - Pressure in the interstitial space impairs ventilation and perfusion

Describe West zones of lung.

Inspiration - diaphragm and external intercostals contract (tidal breathing) - diaphragm increases the superior-inferior dimension of the chest - external intercostals increase the anterior-posterior diameter - accessory muscles include the sternocleidomastoid and scalene muscles Expiration - exhalation usually is passive; driven by recoil of the chest wall - active exhalation is carried out by the abdominal musculature (rectus abdominis, transverse abdominis, internal obliques, external obliques) - internal intercostals serve a secondary role in active exhalation - exhalation becomes an active process when Vm increases or in patients w/ lung dz (ex. COPD) - forced exhalation is required to cough and clear airway of secretions

Describe how the respiratory muscles function during breathing cycle.

Inter-incisor gap looks at the pt's ability to open their mouth. This directly affects the ability to align the oral, pharyngeal, and laryngeal axes. A small inter-incisor gap creates a more acute angle b/t the oral and glottic openings → difficult intubation. Normal = 2-3 fingerbreadths or 4 cm

Describe inter-incisor gap assessment. What is normal?

Restrictive lung dz is characterized by: - impaired lung expansion - ↓ lung volumes - normal pulmonary flow rates

Describe restrictive lung dz.(3)

The Cormack & Lehane scoring system helps measure the view we obtain during direct vision laryngoscopy.

Describe the Cormack & Lehane scoring system.

1. Normal: Upside-down ice cream cone 2. Obstructive: Normal inspiration w/ expiratory obstruction (baby stroller) - ex. COPD 3. Restrictive: shape similar to normal loop but smaller and shifted to right - ex. pulmonary fibrosis 4. Fixed obstruction: inspiration and expiration both affected. - ex. tracheal stenosis - extrathoracic obstruction is abnormal during inspiration and normal during expiration - intrathoracic obstruction is abnormal during expiration and normal during inspiration *inspiration is on the bottom half.

Describe the pulmonary flow-volume loops. 1. Normal 2. Obstructive 3. Restrictive 4. Fixed obstruction Give example of each abnormal pulmonary flow-volume loops.

Trigeminal n. - V1 (ophthalmic): Nares and anterior 1/3 septum - V2 (maxillary): Turbinates and septum - V3 (mandibular): Anterior 2/3 tongue Glossopharyngeal n. - Posterior 1/3 tongue - Soft palate - Oropharynx - Vallecula - Anterior epiglottis SLN - Internal branch: posterior epiglottis → vocal cords - External branch: Ø sensory fx! (only motor innervation to cricothyroid muscle) RLN - below vocal cords → trachea

Describe the sensory innervation of the upper airway. *4 nerves

Vm: amount of air in a single breath x #breaths per minute ⇨ Vm = Vt x RR VA: only measures the fraction of Vm that is available for gas exchange. It removes the anatomic dead space gas from Vm formula. ⇨ VA = (Vt - Anatomic dead space) x RR *VA is directly proportional to CO2 production; indirectly proportional to PaCO2.

Difference b/t minute ventilation (Vm) and alveolar ventilation (VA).

Non-dependent lung - Moves from flatter region (less compliant) to an area of better compliance (slope) - Ventilation is optimal in this lung Dependent lung - Moves from the slope to the lower, flatter area of the curve (less compliant) - Perfusion is best in this lung (d/t gravity) - Reduction of alveolar volume contributes to atelectasis The net effect is that ventilation is better in the nondependent lung and perfusion is better in the dependent lung. This creates VQ mismatch and increases the risk of hypoxemia during OLV.

Discuss how anesthesia in the lateral decubitus position affects the VQ relationship in non-dependent and dependent lungs.

Hering-Breuer reflex prevents over-inflation of the lungs. • Once lungs become overstretched (Vt ~1.5L), stretch receptors in the wall of bronchi and bronchioles transmit signals thru CNX to DRG producing effect similar to pneumotaxic center stimulation. • Switches off inspiratory signals → stops inspiration.

What is the Hering-Breuer inflation reflex?

LMA can fit... ⇨ ETT Size 1 ⇨ 3.5 1.5 ⇨ 4.0 2 ⇨ 4.5 2.5 ⇨ 5.0 3 ⇨ 6.0 4 ⇨ 6.0 5 ⇨ 7.0

What is the largest size ETT that can be pass thru each LMA size? LMA Size: 1 1.5 2 2.5 3 4 5

The mandibular protrusion test assesses the function of the TMJ. Patient subluxes the jaw and the position of the lower incisors is compared to the position of the upper incisors. Class I: Pt can move LI past the UI and bit the vermillion of the lip. Class II: Pt can move the LI in line with the UI. Class III: Pt cannot move LI past the UI → difficult intubation.

What is the mandibular protrusion test? What value indicates difficult intubation risk?

Thyromental distance helps estimate size of the submandibular space. With the neck extended and mouth closed, measure distance from tip of the thyroid cartilage to tip of mentum. Difficult intubation risk if the TMD is >9 cm OR <6 cm (3 fingerbreadths)

What is the thyromental distance? What value indicates difficult intubation risk?

⍺1-antitrypsin deficiency causes alveolar elastase to be free to wreak havoc on pulmonary connective tissue, which leads to panlobar emphysema. Alveolar elastase is an enzyme that breaks down pulmonary connective tissue. This enzyme is kept in check by ⍺1-antitrypsin (produced in the liver). The only definitive tx is liver transplant.

What is ⍺1-antitrypsin deficiency? Treatment?

An Eschmann introducer (bougie) is best used when a grade 3 view is obtained during laryngoscopy (Grade 2 view is the next best time). The likelihood of successful intubation is unacceptably low when a grade 4 view is obtained.

When do we use an Eschmann introducer?

Nasopharyngeal airway C/I: 1. Cribiform plate injury (risk of brain injury): - LeFort II or III fracture - Basilar skull fracture - CSF rhinorrhea - Raccoon eyes - Periorbital edema 2. Coagulopathy (risk of epistaxis) 3. Previous transsphenoidal hypophysectomy 4. Previous Caldwell-Luc procedure 5. Nasal fracture *Caution during pregnancy (epistaxis risk)

When is nasopharyngeal airway contraindicated?

▪︎ Left shift = ↑affinity "Lock" ; occurs in lungs - ↓Temp - ↓2,3DPG - ↓CO2 - ↓H+/↑pH (alkalosis) - HgbMet - HgbCO - HgbF ▪︎ Right shift = ↓affinity "Release" ; occurs near metabolically active tissue - ↑Temp - ↑2,3DPG - ↑CO2 - ↑H+/↓pH (acidosis) Normal P50 is 26.5 partial pressure O2 (mmHg).

Factors that alter the OxyHgb dissociation curve. - 8 Left shift - 5 Right shift What is normal P50?

FRC = ERV + RV = (35 mL/kg) ▪︎ ↓FRC is d/t ↓ outward lung expansion and/or ↓ lung compliance. Ex: - obesity/pregnancy (↑abd pressure) - upright and supine position - anesthetic induction and NMBD - surgical displacement *When FRC is ↓, intrapulmonary shunt (Zone 3) will ↑. PEEP acts to restore FRC by ↓Zone 3. ▪︎ ↑FRC is d/t COPD or any condition that causes air trapping. Since FRC contains RV, it cannot be measured by conventional spirometry. Therefore, we measure it indirectly by nitrogen washout, helium wash-in, or body plethysmography.

Factors that influence FRC? How is FRC measured?

Intrinsic lung dz (affects lung parenchyma) - Acute: aspiration, negative pressure pulmonary edema - Chronic: pulmonary fibrosis, sarcoidosis Extrinsic lung dz (affects areas around lungs) - Chest wall/mediastinum: kyphoscoliosis, flail chest, neuromuscular disorders, mediastinal mass - ↑ intraabd pressure: pregnancy, obesity, ascites

Give examples of intrinsic lung dz (acute and chronic). Give examples of extrinsic lung dz.

V/Q ratio is the ratio of ventilation (Vm = 4L/min) to perfusion (CO = 5L/min) Normal V/Q ratio = 4/5 = 0.8 Dead space: 10/0 = infinity Shunting: 0/10 = 0 *VQ mismatch occurs when ratio is disturbed. If it is >0.8, this moves toward dead space. If <0.8, this moves toward shunting.

- Normal V/Q ratio? - Dead space V/Q ratio? - Shunting V/Q ratio?

Obstructive lung dz 1. FVC: Normal/↓ if gas trapping 2. FEV1: Normal/↓ if gas trapping 3. FEV1/FVC Ratio: ↓ 4. FEF25-75%: ↓ 5. RV: Normal/↑ if gas trapping 6. FRC: Normal/↑ if gas trapping 7. TLC: Normal/↑ if gas trapping Restrictive lung dz 1. FVC: ↓ 2. FEV1: ↓ 3. FEV1/FVC Ratio: Normal 4. FEF25-75%: Normal 5. RV: ↓ 6. FRC: ↓ 7. TLC: ↓

How are the following affected in obstructive vs. restrictive lung dz 1. FVC 2. FEV1 3. FEV1/FVC Ratio 4. FEF25-75% 5. RV 6. FRC 7. TLC

Bronchial blocker can be used to: - insufflate O2 into the non-ventilated lung - suction air from the non-ventilated lung (improves surgical exposure) Bronchial blocker cannot be used to: - ventilate - suction blood, pus, or secretions from the non-ventilated lung

How can the lumen of the bronchial blocker be used during OLV?

Bilateral RLN injury - Acute: respiratory distress (unopposed action of cricothyroid m.) - Chronic: no respiratory distress Unilateral RLN injury - No respiratory distress

How does bilateral and unilateral RLN injury affect airway integrity?

Bilateral SLN injury - hoarseness - no respiratory distress Unilateral SLN injury - No respiratory distress

How does bilateral and unilateral SLN injury affect airway integrity?

CO2 is the primary byproduct of aerobic metabolism. Venous blood transports it to the lungs, where it exits to the atmosphere. Mechanisms of CO2 transport: - Bicarb (70%) - Hgb bound (23%) - Dissolved in plasma (7%) The rxn that converts CO2 to HCO3 requires carbonic anhydrase (H2CO3). H2O + CO2 ↔︎ H2CO3 ↔︎ H+ + HCO3- When the RBC releases CA into plasma, Cl- is transported into the RBC to maintain electroneutrality ⇨ Hamburger shift.

How is CO2 transported in blood?

Smoking will ↑: - SNS tone - sputum production - HgbCO concentration - risk of infection Short-term benefits: - SNS-stimulation effects of nicotine dissipate after 20-30 min - P50 returns to near normal in 12 hours (CaO2 improves) *short-term cessation does NOT ↓ risk of postop pulm complications. Intermediate-term benefits (cessation ≥6 weeks) include return of normal pulm function including: - airway fx - mucociliary clearance - sputum production - pulmonary immune fx - hepatic enzyme induction subsides

How is tobacco smoke harmful? (4) Short- and intermediate-term benefits of smoking cessation?

Trachea is anterior to esophagus. Therefore, we can confirm placement via quality of light shining thru the neck. •If it is in the trachea, the light has to travel thru less tissue. There will be a well-defined circumscribed glow below the thyroid prominence. •If it is in the esophagus, the light has to travel thru more tissue. So, there will be a more diffuse transillumination of the neck w/o the circumscribed glow.

How to confirm proper placement of lighted stylet (light wand)?

OLV Mngmt 1. 100% FiO2 2. Confirm DLT position w/ bronchoscope (poor position is #1 common complication) 3. CPAP 10 cmH2O to dependent lung 4. PEEP 5-10 cmH2O to dependent lung 5. Alveolar recruitment maneuvers 6. Clamp pulm artery to nondependent lung 7. Resume 2-lung ventilation *If hypoxemia still severe, it is prudent to resume 2LV promptly!

Management of hypoxemia during one-lung ventilation.

Max cuff pressures: - ETT: <25 cmH2O - LMA: <60 cmH2O Max peak inspiratory pressures: - LMA Unique: <20 cmH2O - LMA Proseal: <30 cmH2O - LMA Supreme: <30 cmH2O

Max recommended cuff pressures for an ETT vs LMA. What is the max recommended peak inspiratory pressures for: - LMA Unique - LMA Proseal - LMA Supreme

2 hours: clear liquids 4 hours: breast milk 6 hours: non-human milk, infant formula, solid food 8 hours: fried or fatty foods

NPO Guidelines to reduce risk of pulmonary aspiration.

Flail chest is a result of blunt chest trauma with multiple rib fractures. The key xtic is a paradoxical movement of the chest wall at the site of the fractures. Inspiration (Negative intrathoracic pressure) - Normal: chest wall moves outward, lungs expand - Flail chest: injured ribs move inward and collapses affected region Expiration (Positive intrathoracic pressure) - Normal: chest wall moves inward, lungs empty - Flail chest: injured ribs move outward and affected region does not empty Treatment: epidural catheter or intercostal n. blocks (↑risk of LA toxicity)

Pathophysiology and tx of flail chest.

CO reduces the O2 carrying capacity of blood (left shift). It binds to the O2 binding site on Hgb with an affinity 200x that of O2. Oxidative phosphorylation is impaired and metabolic acidosis results. - CO is measured with a co-oximeter (not pulse ox!) - Pts take on a cherry red appearance (not cyanosis) - SNS stimulation may be confused with light anesthesia or pain - If soda lime is dessicated, then volatile gasses can produce CO (Des > Iso >>> Sevo) Treatment: - 100% FiO2 until CoHgb is <5% for 6 hours - Hyperbaric O2 if CoHgb >25% or the patient is symptomatic

Pathophysiology of carbon monoxide poisoning. Treatment?

Awake extubation ▪︎Pros: - airway reflexes intact - ability to maintain airway patency - ↓risk of aspiration ▪︎Cons: - ↑CV and SNS stimulation - ↑cough - ↑ICP - ↑IOP - ↑intraabd pressure Deep extubation ▪︎Pros: - ↓CV and SNS stimulation - ↓cough ▪︎Cons: - airway reflexes ineffective - ↑risk of airway obstruction - ↑risk of aspiration

Pros and Cons of awake vs deep extubation

Indications for retrograde intubation: 1. Unstable c-spine (most common use of RI) 2. Upper airway bleeding (cannot visualize glottis) *Since RI requires time (~5-7min for experienced CRNAs), it is best used when intubation has failed but still able to ventilate.

2 indications for retrograde intubation

Paired cartilages of larynx - Corniculate - Arytenoid - Cuneiform Unpaired cartilages of larynx - Epiglottis - Thyroid - Cricoid *Adult larynx extends from C3-C6 consisting of bone, ligaments, and 9 cartilages.

3 paired cartilages of larynx 3 unpaired cartilages of larynx

Causes of hypercapnia... ▪︎ ↑CO2 Production - Ex. Sepsis, overfeeding, MH, intense shivering, prolonged sz activity, thyroid storm, burns ▪︎ ↓CO2 Elimination - Ex. airway obstruction, ↑dead space, ↑Vd/Vt, ARDS, COPD, respiratory center depression, drug overdose, inadequate NMBD reversal ▪︎ Rebreathing - Ex. incompetent 1-way valve, exhausted soda lime

3 primary causes of hypercapnia. Give examples.

Mechanical ventilation in COPD 1. Low tidal volumes (6-8 mL/kg IBW) 2. ↑ Expiratory time to ↓ air trapping 3. Slow inspiratory flow rate to optimize VQ matching 4. Low PEEP ok as long as air trapping doesn't occur

4 goals/strategies for mechanical ventilation in COPDers.

Indications for Bullard laryngoscope 1. Small mouth opening (min = 7mm) 2. Impaired c-spine mobility 3. Short, thick neck 4. Treacher Collins syndrome 5. Pierre-Robin syndrome

5 Indications for Bullard laryngoscope.

Normal A-a gradient - ↓FiO2 (not enough O2 inspired) - Hypoventilation (inadequate air transfer) Increased A-a gradient - Diffusion limitation (capillary thickening hinders O2 diffusion) - V/Q mismatch - Shunting (pulm blood bypasses alveoli) Shunting is NOT fixed with supplemental oxygen! There is no way for O2 to access the pulmonary capillary. *All the other causes allow O2 to transfer b/t the alveolus and pulm capillary and are reversable.

5 causes of hypoxemia. Which ones are reversed with supplemental oxygen?

1. Antacids: sodium citrate, sodium bicarb, mag trisilicate 2. H2 antagonists: ranitidine, cimetidine, famotidine 3. GI stimulants: metoclopramide 4. PPIs: omeprazole, lansoprazole, pantoprazole 5. Antiemetics: droperidol, ondansetron *Routine use of any of these as prophylaxis for patients not at risk for aspiration is NOT recommended. **Anticholinergics to reduce risk of aspiration is NOT recommended.

5 drug classes used as prophylaxis of aspiration pneumonitis. Give examples of each class.

Indications for bronchial blocker 1. children <8yo (smallest DLT is 26F for 8-10yo) 2. requires nasotracheal intubation 3. tracheostomy 4. preexisting single lumen ETT 5. requires intubation after surgery and want to avoid changing DLT to single lumen ETT

5 indications for a bronchial blocker.

Risk factors for difficult invasive airway 1. Abnormal neck anatomy (tumor, hematoma, abscess, hx of radiation) 2. Obesity (unable to ID cricothyroid membrane) 3. Short neck (unable to ID cricothyroid membrane) 4. Limited access to cricothyroid membrane (halo, neck flexion deformity) 5. Laryngeal trauma

5 risk factors for difficult invasive airway placement.

Risk factors for difficult mask ventilation 1. Beard 2. Obese (BMI >26 kg/m2) 3. No teeth 4. Elderly (>55yo) 5. Snoring "BONES"

5 risk factors for difficult mask ventilation.

Airway block landmarks - Glossopharyngeal n. block: palatoglossal arch at anterior tonsillar pillars - SLN block: greater cornu of hyoid - Transtracheal n. block: cricothyroid membrane

Airway block landmarks - Glossopharyngeal n. block - SLN block - Transtracheal n. block

▪︎Absolute Indication for OLV - Isolation of one lung to avoid contamination (infection, massive hemorrhage) - Control of distribution of ventilation (bronchopleural fistula, surgical opening of major airway, large unilateral lung cyst or bulla, life-threatening hypoxemia r/t lung dz) - Unilateral bronchopulmonary lavage (pulmonary alveolar proteinosis) ▪︎Relative Indication for OLV - Surgical exposure: High priority (thoracic aortic aneurysm, pneumonectomy, thoracoscopy, upper lobectomy, mediastinal exposure) - Surgical exposure: Low priority (middle and lower lobectomy, esophageal resection, thoracic spinal sx) - Pulmonary edema s/p CABG - Severe hypoxemia r/t lung dz

Absolute and Relative Indications for one-lung ventilation.

Contraction of the inspiratory muscles reduces thoracic pressure and increases thoracic volume. This is an example of Boyle's Law.

Contraction of the inspiratory muscles reduces thoracic pressure and increases thoracic volume. What law is this?

Central chemoreceptor - located in medulla - responds to the H+ concentration in CSF (which is a function of the PaCO2 of the blood) *remember PaCO2 is primary stimulus to breathe Peripheral chemoreceptor - located in carotid bodies: Nerves of Hering → CN IX (glossopharyngeal n.) - located in aortic arch: CN X (Vagus) - responds to ↓O2, ↑CO2, and ↑H+

Contrast the location and function (what do they respond to) of the central and peripheral chemoreceptors.

O2 carrying capacity (CaO2) is how much O2 is carried in the blood. CaO2 = (1.34 x Hgb x SaO2) + (PaO2 x 0.003) Normal = 20 mL O2/dL

Equation and normal value for O2 carrying capacity.

Oxygen delivery (DO2) is how much O2 is delivered to the tissues. DO2 = CaO2 x Cardiac Output x 10 Normal = 1000 mL O2/min

Equation and normal value for O2 delivery.

Medullary respiratory centers 1. dorsal respiratory center: active during inspiration (respiratory pacemaker) 2. ventral respiratory center: active during expiration Pontine respiratory centers 3. pneumotaxic center (upper pons): inhibits DRC 4. apneustic center (lower pons): stimulates DRC

What are the 4 areas of the respiratory center?

Anatomic Vd: air confined to the conducting airways - Nose/Mouth → Terminal bronchioles Alveolar Vd: alveoli ventilated but not perfused - reduced pulmonary blood flow (↓CO) Physiologic Vd: Anatomic Vd + Alveolar Vd - anything that ↑ anatomic or alveolar Vd Apparatus Vd: the Vd added by equipment - facemask, HME

What are the 4 types of dead space? Give an example of each.

1. Guedel 2. Berman 3. Williams - used for blind orotracheal intubation and fiberoptic intubation 4. Ovassapian - used for fiberoptic intubation

What are the 4 types or oral airways? Which (2) are best for fiberoptic intubation?

Alveolar ventilation is a function of alveolar size and its position on the alveolar compliance curve. ▪︎The best ventilated alveoli are the most compliant (steep slope of curve). ▪︎The poorest ventilated alveoli are the least compliant (flat portion of curve). **Compliance = ∆Volume/∆Pressure **Perfusion greatest at lung base d/t gravity. **Ventilation greatest at lung base d/t higher alveolar compliance.

What does the alveolar compliance curve tell you?

The diffusing capacity for carbon monoxide (DLCO) assesses how well the lungs can exchange gas. Normal = 17-25 mL/CO/min/mmHg Using Fick's law of diffusion, the DLCO tells us about the alveolar-capillary interface: - surface area (↓ by emphysema) - thickness (↑ by pulmonary fibrosis and pulmonary edema) Therefore, DLCO is ↓ by anything that ↓ alveolar surface area and/or ↑ thickness of the alveolar-capillary interface.

What does the diffusing capacity for carbon monoxide tell us? What law uses equation?

Ludwig's angina is a bacterial infection characterized by a rapidly progressing cellulitis in the mouth floor. Inflammation and edema compress the submandibular, subaxillary, and sublingual spaces. The most significant concern is posterior displacement of the tongue ⇨ complete, supraglottic airway obstruction. Best way to secure airway is an AWAKE nasal intubation or AWAKE tracheostomy.

What is Ludwig's angina? Best way to secure airway in this patient?

Mendelson's syndrome is a chemical aspiration pneumonitis with the following xtics: - Gastric pH <2.5 - Gastric volume >25 mL (0.4 mL/kg) It was first described in OB pts receiving inhalation anesthesia.

What is Mendelson's syndrome?

Angioedema is d/t ↑ vascular permeability that can lead to swelling of the face, tongue, and airway. Airway obstruction is an extreme concern. 2 common causes: ▪︎ Angiotensin converting inhibitors Treatment: epi, antihistamines, and steroids (just like anaphylaxis) ▪︎Hereditary angioedema (C1-esterase deficiency) Treatment: C1-esterase concentrate or FFP *epi, antihistamines, and steroids are not effective

What is angioedema? - 2 common causes and their respective treatment

Closing volume is the point at which dynamic compression of the airways begins. This is the volume above residual volume where the small airways begin to close during expiration. ↑ CV is d/t: "CLOSE-P" - COPD - LV failure - Obesity - Surgry - Extreme age - Pregnancy

What is closing volume (CV)? What increases it?

HPV minimizes shunting by ↓blood flow thru poorly ventilated alveoli. A low PAO2 (alveolar) is the trigger that activates HPV. The effect begins almost immediately and reaches its full effect after 15 min. Anything that inhibits HPV will ↑ shunting (perfusion w/o ventilation). This includes: - halogenated gases >1-1.5 MAC - PDE inhibitors - dobutamine - vasodilators **IV anesthetics do NOT inhibit HPV.

What is hypoxic pulmonary vasoconstriction (HPV)? What impairs it? (4)

Mediastinoscopy: performed to obtain biopsy of the paratracheal lymph nodes at the level of the carina. This helps the surgeon stage the tumor prior to lung resection. ▪︎Potential complications: 1. Hemorrhage (most common) d/t vascular injury 2. Pneumothorax (2nd most common) d/t pleural injury 3. Impaired cerebral perfusion d/t innominate compression 4. Dysrhythmias d/t stimulation of carotid, aorta, or trachea 5. Air embolism d/t venous injury and air entrapment 6. Chylothorax d/t thoracic duct injury (left chest only) 7. Hoarseness and/or vocal cord paralysis d/t RLN or Vagus injury *Innominate a. compression compromises the circulation to the RUE and Right side of Circle of Willis. Place an a-line or pulse ox on the RUE to monitor for innominate a. compression.

What is mediastinoscopy? 7 Potential complications?

A-a gradient is the diff b/t alveolar oxygen (PAO2) and arterial oxygen (PaO2). - helps diagnose cause of hypoxemia by quantifying amount of venous admixture *Normal = 5-15 mmHg A-a gradient increased by: - high FiO2 - aging - vasodilators - right to left shunting - diffusion limitation

What is the A-a gradient? 5 factors affect it?

Bohr effect describes O2 carriage. ↑CO2 and ↓pH causes erythrocytes to release O2. It is the cell's way of asking hgb to release O2 to support aerobic metabolism.

What is the Bohr effect?

The Haldane effect describes O2 carriage. ↑O2 causes erythrocytes to release CO2 (in the lungs). It states that deoxygenated Hgb is able to carry more CO2 (venous blood).

What is the Haldane effect?

Which muscles abduct and adduct the vocal cords? - Posterior CricoArytenoid "Please Come Apart" - Lateral CricoArytenoid "Let's Close Airway"

Which muscles abduct and adduct the vocal cords?

Which muscles tense and relax the vocal cords? - CricoThyroid "Cords Tense" - ThyroaRytenoid "They Relax"

Which muscles tense and relax the vocal cords?