Obstructive Sleep Apnea Overview
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Questions and Answers

What is the primary risk factor for Obstructive Sleep Apnea (OSA)?

  • Age over 50 years
  • High blood pressure
  • Gender, male
  • Obesity (correct)

    • Which index is used for diagnosing the severity of sleep apnea?

  • Chronic Hypoxemia Index
  • STOP-Bang Score
  • Body Mass Index (BMI)
  • Apnea Plus Hypopnea (AHI) Index (correct)

    • What is a hallmark symptom of Obstructive Sleep Apnea?

  • Daytime somnolence (correct)
  • Persistent fatigue
  • Frequent headaches
  • Chronic cough

    • What type of medications are commonly used for treating OSA?

    <p>Antidepressants</p> Signup and view all the answers

    What preoperative consideration is essential for a patient with OSA?

    <p>Bring CPAP</p> Signup and view all the answers

    What is the expected sensitivity of the STOP-Bang questionnaire?

    <p>100%</p> Signup and view all the answers

    Which of the following treatments is considered surgical for OSA?

    <p>Uvulopalatopharyngoplasty</p> Signup and view all the answers

    Which physiological change is associated with OSA?

    <p>Decreased apneic oxygen reserve</p> Signup and view all the answers

    What is the hallmark feature of Chronic Obstructive Pulmonary Disease (COPD)?

    <p>Chronic productive cough</p> Signup and view all the answers

    Which type of emphysema predominantly affects the respiratory bronchioles in the upper lung lobes?

    <p>Centrilobular emphysema</p> Signup and view all the answers

    What is the most significant risk factor for developing COPD?

    <p>Cigarette smoking</p> Signup and view all the answers

    What is the classification for a patient with FEV₁ between 50% to 79%?

    <p>Moderate</p> Signup and view all the answers

    What physiological change occurs due to the inflammatory reaction in COPD?

    <p>Increased airway resistance</p> Signup and view all the answers

    Which of the following is NOT a common clinical manifestation of COPD?

    <p>Persistent fever</p> Signup and view all the answers

    What is a potential secondary cause of death in COPD patients?

    <p>Heart disease</p> Signup and view all the answers

    What is the primary method for managing intraoperative bronchospasm?

    <p>Increasing FiO₂ to 1.0</p> Signup and view all the answers

    What is the hallmark clinical feature of pulmonary edema?

    <p>Pink, frothy sputum</p> Signup and view all the answers

    Which of the following conditions could lead to non-cardiogenic pulmonary edema?

    <p>Acute respiratory distress syndrome (ARDS)</p> Signup and view all the answers

    Which treatment is commonly avoided when managing aspiration pneumonitis?

    <p>Antibiotics</p> Signup and view all the answers

    Which of the following is NOT a risk factor for developing ARDS?

    <p>Pulmonary fibrosis</p> Signup and view all the answers

    In which type of pneumothorax does air progressively accumulate to cause a mediastinal shift?

    <p>Tension pneumothorax</p> Signup and view all the answers

    What is the mechanism by which aspiration pneumonitis causes lung injury?

    <p>Caustic injury from gastric contents</p> Signup and view all the answers

    Which treatment modality is suggested for managing non-cardiogenic pulmonary edema?

    <p>Lung protective ventilation</p> Signup and view all the answers

    During the emergence phase of anesthesia, what measure is critical to verify?

    <p>Adequate reversal of neuromuscular blockade</p> Signup and view all the answers

    Which condition is primarily characterized by airway closure leading to atelectasis?

    <p>Aspiration pneumonitis</p> Signup and view all the answers

    What is the hallmark clinical feature of pulmonary hypertension?

    <p>Dyspnea/exercise intolerance</p> Signup and view all the answers

    What should be done for a patient presenting with sudden hypoxemia postoperatively?

    <p>Consider high-flow oxygen therapy</p> Signup and view all the answers

    What is a primary cause for the development of tension pneumothorax?

    <p>Chest trauma resulting in rib fractures</p> Signup and view all the answers

    What poor outcome is associated with a 5-year mortality rate in patients with pulmonary hypertension?

    <p>79%</p> Signup and view all the answers

    Which condition is a common cause of chronic cor pulmonale?

    <p>Chronic obstructive pulmonary disease (COPD)</p> Signup and view all the answers

    What is the typical pulmonary function change seen with atelectasis?

    <p>Decreased lung volumes</p> Signup and view all the answers

    Which intervention is NOT recommended in the management of aspiration pneumonitis?

    <p>Antibiotic therapy as routine</p> Signup and view all the answers

    Which of the following is a primary pathway leading to pulmonary embolism?

    <p>Deep vein thrombosis (DVT)</p> Signup and view all the answers

    What should be avoided during maintenance anesthesia in patients with pulmonary conditions to prevent hemodynamic instability?

    <p>Hypothermia</p> Signup and view all the answers

    Which medication is advised to minimize cardiac depression during anesthesia in pulmonary hypertension?

    <p>Etomidate</p> Signup and view all the answers

    What is a significant clinical manifestation of cor pulmonale?

    <p>Jugular venous distension</p> Signup and view all the answers

    Which non-invasive assessment tool is crucial for diagnosing pulmonary hypertension?

    <p>Doppler echocardiography</p> Signup and view all the answers

    What is a potential surgical option for treating severe cases of pulmonary hypertension?

    <p>Heart/lung transplant</p> Signup and view all the answers

    What is a characteristic pathophysiological feature of pulmonary embolism?

    <p>Occlusion of pulmonary blood flow</p> Signup and view all the answers

    Which condition is characterized by obesity coupled with daytime hypoventilation?

    <p>Obesity Hypoventilation Syndrome (OHS)</p> Signup and view all the answers

    Chronic hypoxemia and hypercarbia due to OSA can lead to an inflammatory state.

    <p>True</p> Signup and view all the answers

    What is the primary treatment for Obstructive Sleep Apnea (OSA)?

    <p>CPAP</p> Signup and view all the answers

    The _____ index quantifies the number of abnormal respiratory events per hour of sleep.

    <p>Apnea Plus Hypopnea (AHI)</p> Signup and view all the answers

    Which of the following is NOT a component of the STOP-Bang questionnaire?

    <p>Gender, female</p> Signup and view all the answers

    Match the treatment options with their types for Obstructive Sleep Apnea (OSA):

    <p>Lifestyle = Weight loss Medical = CPAP Surgical = Adenotonsillectomy Medications = Modafinil</p> Signup and view all the answers

    Patients with OSA are generally not sensitive to sedative effects.

    <p>False</p> Signup and view all the answers

    Describe a preoperative consideration for a patient with OSA.

    <p>Bring CPAP on the day of surgery.</p> Signup and view all the answers

    A crucial step during induction for a patient with OSA is to elevate the head and shoulders for _____ during ventilation.

    <p>ramping</p> Signup and view all the answers

    What percentage of obese patients are affected by OSA?

    <p>40%</p> Signup and view all the answers

    What is the hallmark clinical feature of pulmonary hypertension?

    <p>Dyspnea/exercise intolerance</p> Signup and view all the answers

    Cor pulmonale can only develop as a chronic condition.

    <p>False</p> Signup and view all the answers

    What is the incidence of pulmonary embolism in surgical patients?

    <p>Approximately 1%</p> Signup and view all the answers

    The primary cause of pulmonary embolism typically results from a __________.

    <p>deep vein thrombosis (DVT)</p> Signup and view all the answers

    Match the following conditions with their causes:

    <p>Pulmonary Hypertension = COPD Cor Pulmonale = Chronic left heart failure Pulmonary Embolism = DVT Acute Cor Pulmonale = Pulmonary Embolism</p> Signup and view all the answers

    What procedure can be performed to provide a definitive diagnosis for pulmonary embolism?

    <p>Cardiac catheterization</p> Signup and view all the answers

    Neuraxial anesthesia may cause significant hemodynamic alterations during anesthesia maintenance for patients with pulmonary conditions.

    <p>True</p> Signup and view all the answers

    Which medical treatments are commonly used for managing Pulmonary Arterial Hypertension (PAH)?

    <p>Prostanoids, endothelin receptor antagonists, phosphodiesterase inhibitors, diuretics</p> Signup and view all the answers

    The release of a __________ into circulation leads to occlusion of pulmonary circulation.

    <p>thrombus</p> Signup and view all the answers

    Which of the following statements about the prognosis of pulmonary hypertension is true?

    <p>The disease progresses rapidly.</p> Signup and view all the answers

    What is the hallmark clinical feature of pulmonary edema?

    <p>Pink, frothy sputum</p> Signup and view all the answers

    Hypoxemia is an expected feature of aspiration pneumonitis.

    <p>True</p> Signup and view all the answers

    In which condition do the alveoli collapse due to obstruction, leading to impaired gas exchange?

    <p>Atelectasis</p> Signup and view all the answers

    Increased pulmonary capillary pressure is a characteristic of __________ pulmonary edema.

    <p>cardiogenic</p> Signup and view all the answers

    Match the following conditions with their descriptions:

    <p>Pulmonary Edema = Accumulation of fluid in interstitium and alveoli Atelectasis = Airway collapse leading to impaired gas exchange Tension Pneumothorax = Progressive accumulation of air in pleural space causing mediastinal shift Aspiration Pneumonitis = Chemical injury to lung due to gastric contents</p> Signup and view all the answers

    What treatment should be considered for patients with acute respiratory distress syndrome (ARDS)?

    <p>Lung protective ventilation</p> Signup and view all the answers

    Hypotension is not a common sign of pneumothorax.

    <p>False</p> Signup and view all the answers

    What is the primary medical treatment for managing lidocaine-induced ventricular dysrhythmias?

    <p>Amiodarone</p> Signup and view all the answers

    The development of __________ is characterized by the rapid accumulation of fluid in the alveoli.

    <p>Acute Respiratory Distress Syndrome (ARDS)</p> Signup and view all the answers

    Which risk factor is majorly associated with the development of ARDS?

    <p>Sepsis</p> Signup and view all the answers

    What is the primary characteristic of emphysema?

    <p>Permanent enlargement of air spaces and destruction of alveolar walls</p> Signup and view all the answers

    Cigarette smoking is the most significant risk factor for Chronic Obstructive Pulmonary Disease (COPD).

    <p>True</p> Signup and view all the answers

    What is the hallmark clinical feature of chronic bronchitis?

    <p>chronic productive cough</p> Signup and view all the answers

    The decrease in elastic recoil of the lungs leads to _____ in patients with COPD.

    <p>airflow obstruction</p> Signup and view all the answers

    Match the following terms related to COPD with their definitions:

    <p>Chronic Bronchitis = Excess mucous secretion causing airflow obstruction Centrilobular Emphysema = Affects respiratory bronchioles in upper lung lobes Panlobular Emphysema = Widespread destruction of acini FEV₁ = Measurement used for classifying severity of lung obstruction</p> Signup and view all the answers

    Which of the following is NOT a common symptom associated with COPD?

    <p>Chest pain</p> Signup and view all the answers

    The progression of airflow limitation in COPD is generally reversible.

    <p>False</p> Signup and view all the answers

    What are two types of emphysema mentioned in the content?

    <p>centrilobular and panlobular</p> Signup and view all the answers

    COPD is a combination of both _____ and chronic bronchitis.

    <p>emphysema</p> Signup and view all the answers

    What is a likely secondary cause of death in individuals with COPD?

    <p>Heart disease</p> Signup and view all the answers

    What structure prevents aspiration during swallowing?

    <p>Larynx</p> Signup and view all the answers

    The nasal septum is formed entirely by cartilage.

    <p>False</p> Signup and view all the answers

    What are the three functions of the nose?

    <p>Heating, humidification, filtration</p> Signup and view all the answers

    The area of the respiratory zone which primarily functions in gas exchange is called the _____

    <p>alveoli</p> Signup and view all the answers

    Match the following components of the respiratory system with their descriptions:

    <p>Trachea = Structure preventing airway collapse Bronchi = Conduct air to each lung Larynx = Protective structure during swallowing Pharynx = Muscular tube extending to the esophagus</p> Signup and view all the answers

    Which of the following structures contains the true vocal cords?

    <p>Larynx</p> Signup and view all the answers

    The trachea is composed of complete rings of cartilage.

    <p>False</p> Signup and view all the answers

    What are the names of the four paranasal air sinuses?

    <p>Frontal, ethmoid, maxillary, sphenoid</p> Signup and view all the answers

    What does a V/Q ratio of 0 indicate?

    <p>Perfusion without ventilation</p> Signup and view all the answers

    A rightward shift in the oxyhemoglobin dissociation curve reduces the release of oxygen from hemoglobin.

    <p>False</p> Signup and view all the answers

    What is the primary factor that Dalton's Law of Partial Pressures emphasizes?

    <p>Total pressure equals the sum of partial pressures.</p> Signup and view all the answers

    The equation for the diffusion of gases across the alveolocapillary membrane is described by ______'s Law.

    <p>Fick</p> Signup and view all the answers

    Match the gas-related terms to their definitions:

    <p>Dead Space = Ventilation without perfusion Shunt = Perfusion without ventilation Alveolar Gas Equation = Calculation of PA<del>O2</del> Oxyhemoglobin Dissociation Curve = Relationship between pH and oxygen release</p> Signup and view all the answers

    What is the primary muscle of inspiration in the mechanics of breathing?

    <p>Diaphragm</p> Signup and view all the answers

    The pleura is the serous membrane that separates the lungs from the diaphragm.

    <p>False</p> Signup and view all the answers

    What is the relationship expressed by Boyle's Law?

    <p>Pressure and volume are inversely related.</p> Signup and view all the answers

    The __________ pressure is calculated as the difference between alveolar pressure and pleural pressure.

    <p>transpulmonary</p> Signup and view all the answers

    Match the following terms related to lung compliance:

    <p>Compliance = Measure of lung stiffness Elastic forces = Collagen and elastin in lung tissue Alveolar surface tension = Inhibits lung expansion High compliance = Easier expansion of the lung</p> Signup and view all the answers

    Which component of the thoracic cavity specifically surrounds the lungs?

    <p>Visceral pleura</p> Signup and view all the answers

    Bronchial circulation is responsible for the blood supply to the lungs and bronchi.

    <p>True</p> Signup and view all the answers

    What is the significance of the diaphragm in respiration?

    <p>It is the primary muscle that enables inhalation by expanding the thoracic cavity.</p> Signup and view all the answers

    The thoracic cavity consists of the left pleural cavity, right pleural cavity, and __________.

    <p>mediastinum</p> Signup and view all the answers

    Which of the following pressures refers specifically to the pressure within the alveoli?

    <p>Alveolar pressure</p> Signup and view all the answers

    Which system supplies deoxygenated blood for gas exchange in the lungs?

    <p>Pulmonary circulation</p> Signup and view all the answers

    The pulmonary circulation has a high-pressure system when compared to systemic circulation.

    <p>False</p> Signup and view all the answers

    What is the normal ventilation-perfusion ratio in the lungs?

    <p>0.8</p> Signup and view all the answers

    The ____ aorta supplies oxygenated blood to the conducting zone of the respiratory system.

    <p>thoracic</p> Signup and view all the answers

    Match the pulmonary pressures with their approximate values:

    <p>Right Ventricular Pressure = 15 mm Hg Pulmonary Artery Pressure = 20 mm Hg Pulmonary Capillary Pressure = 5 mm Hg Left Atrial Pressure = 7 mm Hg</p> Signup and view all the answers

    What effect does hypoxic pulmonary vasoconstriction have?

    <p>Shunts blood away from poorly ventilated regions</p> Signup and view all the answers

    Pulmonary vessels are narrower and less compliant than systemic arteries.

    <p>False</p> Signup and view all the answers

    What is the primary characteristic of the vessels in the pulmonary arterial system?

    <p>They are shorter, wider, and more distensible than systemic arteries.</p> Signup and view all the answers

    The left atrium receives oxygenated blood from the __________.

    <p>pulmonary veins</p> Signup and view all the answers

    Match the following pressures to their appropriate values:

    <p>Pulmonary wedge pressure = 5 mm Hg Pc = 7 mm Hg Pif = 8 mm Hg Πp = 28 mm Hg</p> Signup and view all the answers

    Which lung volume represents the amount of air inspired or expired with each normal breath?

    <p>Tidal Volume</p> Signup and view all the answers

    The vital capacity is the maximum amount of air that remains in the lungs after the most forceful expiration.

    <p>False</p> Signup and view all the answers

    What is the method used to indirectly measure certain lung volumes like Functional Residual Capacity?

    <p>Helium Dilution Method</p> Signup and view all the answers

    The maximum amount of air that the lungs can contain is known as _____ Lung Capacity.

    <p>Total</p> Signup and view all the answers

    Match the following lung volumes/capacities with their descriptions:

    <p>Tidal Volume = Amount of air for each normal breath Inspiratory Reserve Volume = Extra air that can be inspired with full force Residual Volume = Air remaining after forceful expiration Vital Capacity = Maximum air expelled after maximum inhalation</p> Signup and view all the answers

    What does the equation Minute Ventilation = Tidal Volume × Respiratory Rate calculate?

    <p>Volume of air moved in one minute</p> Signup and view all the answers

    Dead space refers to ventilated areas that receive adequate perfusion for gas exchange.

    <p>False</p> Signup and view all the answers

    What is the primary purpose of measuring Functional Residual Capacity?

    <p>To assess lung health and capacity for gas exchange</p> Signup and view all the answers

    The volume of air that remains in the lungs at the end of normal expiration is called _____ Capacity.

    <p>Functional Residual</p> Signup and view all the answers

    Which of the following can be an indirect measurement to determine lung volumes?

    <p>Helium Dilution Method</p> Signup and view all the answers

    Study Notes

    Obstructive Sleep Apnea (OSA)

    • A mechanical obstruction of the pharynx due to reduced muscle tone during sleep
    • Obesity is the biggest risk factor
    • 40% of obese patients have OSA
    • 80% of patients seeking bariatric surgery have OSA
    • The prevalence is increasing in children
    • OSA is linked to higher morbidity and mortality in hospitalized patients
    • OSA causes chronic hypoxemia and hypercarbia
    • Chronic hypoxemia and hypercarbia lead to an inflammatory response
    • OSA reduces functional residual capacity (FRC)
    • Decreased apneic oxygen reserve contributes to hypoxemia and hypercarbia

    Clinical Features and Diagnosis of OSA

    • Daytime sleepiness is a hallmark symptom
    • Habitual snoring and fragmented sleep are typical
    • Polysomnography is needed for a definitive diagnosis, and to establish severity
    • The Apnea-Hypopnea Index (AHI) quantifies the number of abnormal respiratory events per hour of sleep
    • STOP-Bang is a simple screening tool used preoperatively
    • STOP-Bang has a sensitivity of ~100% and a specificity of ~40%

    Treatment for OSA

    • Lifestyle modifications: weight loss
    • Medical treatment: CPAP, airway devices, medications (modafinil, methylxanthines, tricyclic antidepressants)
    • Surgical treatment: adenotonsillectomy, uvulopalatopharyngoplasty, hypoglossal nerve stimulator

    Anesthetic Management for OSA

    • Preoperative:
      • Bring CPAP to the hospital on the day of surgery
      • Conduct a thorough airway exam to anticipate difficulty with mask ventilation or laryngoscopy
      • Assess Mallampati score and neck circumference
      • Consider regional anesthesia or multimodal analgesia to minimize the need for sedatives
      • Minimize sedatives, as OSA patients are sensitive to their effects
    • Induction:
      • Anticipate difficult mask ventilation and laryngoscopy
      • Reduced FRC shortens apneic oxygen time
      • Elevate the head and shoulders (ramping)
      • Keep airway adjuncts (LMA/videolaryngoscope) available

    Chronic Obstructive Pulmonary Disease (COPD)

    • A preventable and treatable condition characterized by airflow obstruction that is not fully reversible
    • The airflow limitation usually progresses and is linked to an inflammatory response in the lungs caused by noxious particles or gases.

    Chronic Bronchitis

    • Obstructed expiratory airflow due to excessive mucous secretion
    • Occurs most days for at least three months per year for at least two consecutive years

    Emphysema

    • Permanent enlargement of air spaces distal to the terminal bronchioles, with destruction of alveolar walls
    • Centrilobular: impacts mainly the respiratory bronchioles in the upper lung lobes
    • Panlobular: widespread destruction of the air sacs

    Incidence, Outcomes, and Etiology of COPD

    • Cigarette smoking is the primary risk factor
    • Environmental pollutants and genetics also play a role
    • COPD is the third-leading cause of death, affecting approximately 5% of American adults
    • Death can result from respiratory failure or related comorbidities (e.g., heart disease, lung cancer)

    Pathophysiology of COPD

    • An inflammatory reaction in the lungs leads to progressive airflow obstruction (decreased FEV1)
    • Bronchial lumen size is reduced
    • Increased collapsibility of bronchial walls
    • Decreased elastic recoil of the lungs
    • A combination of emphysema and chronic bronchitis characterizes COPD

    Clinical Features and Diagnosis of COPD

    • A chronic productive cough and progressive exercise limitations are hallmarks
    • Clinical manifestations include dyspnea and wheezing
    • Pulmonary function testing (GOLD classification) establishes diagnosis and severity:
      • FEV1 ≥80% = mild
      • FEV1 50%-79% = moderate
      • FEV1 30%-49% = severe
      • FEV1 <30% = very severe

    Anesthetic Management for COPD

    • Preoperative:
      • Thorough history and physical exam to assess severity
      • Consider spirometry and arterial blood gas (ABG) analysis
      • Optimize medical management before surgery
    • Induction:
      • Consider rapid sequence induction (RSI)
      • Use propofol rather than etomidate or barbiturates
    • Maintenance:
      • Use sevoflurane as the least irritating volatile anesthetic
      • Avoid atracurium, mivacurium, morphine, B-antagonists, Hemabate, and NSAIDs
    • Emergence:
      • Consider deep extubation
      • Favour Sugammadex over anticholinesterase reversal agents to avoid bronchospasm
      • Confirm adequate reversal of neuromuscular blockade

    Intraoperative Bronchospasm

    • Administer additional anesthetic agents
    • Increase FiO2 to 100%
    • Administer a short-acting B2-agonist (albuterol)
    • Consider administering epinephrine 10 mcg/kg
    • Administer a corticosteroid (hydrocortisone 2-4 mg/kg)
    • Consider administering aminophylline

    Pulmonary Hypertension (PH)

    • Mean pulmonary artery pressure >25 mm Hg

    Incidence, Outcomes, and Etiology of PH

    • Rapid disease progression; 5-year mortality rate is 79%
    • Causes include COPD, connective tissue disorders, sarcoidosis, drug effects, and genetics/idiopathic

    Pathophysiology of PH

    • Increased vascular tone
    • Growth and proliferation of pulmonary vascular smooth muscle
    • Right ventricular overload that may lead to cor pulmonale

    Clinical Features and Diagnosis of PH

    • Dyspnea and exercise intolerance are hallmarks
    • Diagnosis is established through clinical evaluation and diagnostic tests

    Anesthetic Management for PH

    • Preoperative Considerations:
      • Consider ECG, echocardiogram, chest x-ray, and ABG
      • Continue medications for pulmonary hypertension
      • Consider regional anesthesia
    • Maintenance:
      • Neuraxial anesthesia may cause significant hemodynamic changes
      • Etomidate or high-dose opioids may be preferred to minimize cardiac depression
      • Consider arterial blood pressure monitoring
      • Consider a central venous catheter for major procedures

    Cor Pulmonale

    • Right heart failure secondary to pulmonary pathology

    Incidence, Outcomes, and Etiology of Cor Pulmonale

    • Cor pulmonale is the third most common cardiac disorder in individuals over 50 years old
    • Five times more prevalent in males
    • Cor pulmonale can be acute (e.g., pulmonary embolism) or chronic (e.g., COPD)

    Pathophysiology of Cor Pulmonale

    • Right ventricular dysfunction develops in response to pulmonary hypertension
    • The rate of right ventricular dysfunction progression depends on the severity and progression of pulmonary hypertension

    Clinical Features and Diagnosis of Cor Pulmonale

    • Cough, dyspnea, weakness, fatigue, hemoptysis, jugular venous distention, S3 gallop, S4 heart sound, murmurs, hepatomegaly, ascites, and dependent edema are common manifestations.
    • Doppler echocardiography: the velocity of tricuspid regurgitation correlates with invasive pulmonary artery pressure measurements
    • Cardiac catheterization: provides information about pressures in the pulmonary system and heart

    ###Treatment for Cor Pulmonale

    • Medical: Oxygen therapy, medications (prostanoids, endothelin receptor antagonists, phosphodiesterase inhibitors, diuretics)
    • Surgical: Heart/lung transplant

    Anesthetic Management for Cor Pulmonale

    • Preoperative:
      • Consider regional anesthesia
    • Maintenance:
      • Maintain adequate oxygenation
      • Avoid acidosis
      • Minimize stimuli that increase sympathetic tone
      • Avoid hypothermia

    Pulmonary Embolism (PE)

    • Occlusion of pulmonary blood flow by embolic material, causing obstruction and ventilation/perfusion mismatch

    Incidence, Outcomes, and Etiology of PE

    • Occurs in approximately 1% of surgical patients
    • Occurs in up to 30% of orthopedic surgical patients
    • Usually caused by a deep vein thrombosis (DVT) originating from the iliofemoral vessels
    • Other causes include DVT, air, CO2, tumor, bone, fat, and catheter fragments
    • Virchow's Triad: venous stasis, venous injury, and hypercoagulable state

    Pathophysiology of PE

    • Thrombus formation
    • Release of thrombus into the circulation
    • Pulmonary circulation occlusion
    • Increased pulmonary vascular resistance proximal to the occlusion, decreased perfusion distal to the occlusion
    • Ventilation/perfusion mismatch
    • Alveolar damage

    Clinical Features and Diagnosis of PE

    • Hallmark: Sudden-onset dyspnea, a sudden decrease in EtCO2
    • Clinical manifestations: Hypotension, tachycardia, hypoxemia, wheezing, and tachypnea

    Treatment for PE

    • Medical: Thrombolytic agents, anticoagulation
    • Surgical: Embolectomy (thromboendartectomy, rheolytic embolectomy, rotational embolectomy, suction embolectomy); inferior vena cava (IVC) filter insertion

    Anesthetic Management for PE

    • Induction:
      • Use etomidate
      • Avoid ketamine and nitrous oxide (N2:O)
    • Maintenance:
      • Consider high FiO2
      • Consider monitoring central venous pressure (CVP) and pulmonary artery pressure (PAP)

    Intraoperative Pulmonary Embolism

    • Increase FiO2 to 100%
    • Discontinue anesthetic agents
    • Administer sympathomimetics and fluids/blood as needed
    • Administer lidocaine or amiodarone for ventricular dysrhythmias
    • Prepare for thrombolysis or pulmonary embolectomy
    • Consider cardiopulmonary bypass as a temporizing measure

    Restrictive Pulmonary Disease (Pulmonary Edema)

    • Conditions that interfere with normal lung expansion during inspiration

    Incidence, Outcomes, and Etiology of Restrictive Pulmonary Disease

    • Pulmonary edema refers to an accumulation of excess fluid in the interstitium and alveoli
    • Negative-pressure pulmonary edema may result from acute airway obstruction

    Pathophysiology of Restrictive Pulmonary Disease

    • Imbalance of Starling's forces leading to pulmonary edema
    • Cardiogenic: high pulmonary capillary pressure
    • Non-cardiogenic: Increased permeability of the alveolar-capillary membrane (e.g., sepsis, ARDS)

    Clinical Features and Diagnosis of Restrictive Pulmonary Disease

    • Hallmark: pink, frothy sputum
    • Clinical manifestations: Tachypnea, accessory muscle use, tachycardia, hypertension, diaphoresis, and basilar crackles on auscultation
    • Chest X-ray findings:
      • Enlarged cardiac silhouette
      • 'White-out' appearance

    Treatment Restrictive Pulmonary Disease

    • Medical: Oxygen therapy, CPAP or mechanical ventilation, fluid restriction, medications (morphine, nitroprusside, inotropes)

    Aspiration Pneumonitis

    • Movement of gastric contents into the lungs, causing chemical injury to lung tissue.

    Incidence, Outcomes, and Etiology of Aspiration Pneumonitis

    • Overall incidence ~1/3000 anesthetics
    • ~1/1500 emergency anesthetics or Cesarean deliveries
    • Occurs when protective airway reflexes are inhibited, usually after vomiting or gastroesophageal reflux
    • Risk factors: Emergency surgery with a full stomach, bowel obstruction, pregnancy, and acute trauma
    • Often resolves without treatment

    ###Pathophysiology of Aspiration Pneumonitis

    • Immediate damage to lung parenchyma by caustic aspirate
    • Atelectasis develops within minutes, leading to airway closure and decreased compliance
    • Alveolar macrophages release inflammatory cytokines (IL-8, TNF-alpha), attracting neutrophils that release oxygen radicals and proteases
    • Secondary injury results from fibrin deposition and alveolar necrosis
    • Damage to the alveolar-capillary membrane
    • Impaired gas exchange
    • Capillary leak
    • Hemodynamic changes
    • Myocardial ischemia and acidosis due to hypoxemia

    ###Clinical Features and Diagnosis of Aspiration Pneumonitis

    • Hallmark: Arterial hypoxemia
    • Clinical manifestations: Tachypnea, dyspnea, cyanosis, tachycardia, and hypertension
    • Diagnosis: ABG and chest radiography
    • Chest radiography: Demonstrates aspirate in the perihilar and dependent lung regions
    • Differential diagnosis: High concern in an otherwise healthy patient who develops unexplained/sudden hypoxemia intra- or postoperatively

    Treatment for Aspiration Pneumonitis

    • Medical: Ventilation (consider low FiO2, PEEP), consider steroids, consider lidocaine 1.5 mg/kg, avoid routine administration of antibiotics, avoid routine use of deep tracheal suctioning/bronchoscopy

    Anesthetic Management for Aspiration Pneumonitis

    • Preoperative Considerations:
      • NPO
      • Identify risk factors
      • Pharmacologic prophylaxis
        • Nonparticulate antacids (sodium citrate with citric acid)
        • H2 receptor antagonists (famotidine)
        • PPIs (pantoprazole)
        • Antiemetics (ondansetron)
    • Induction:
      • Consider RSI with cricoid pressure
      • Consider videolaryngoscopy
      • If vomiting, reflux, or aspiration occur during induction:
        • Tilt the patient's head downwards or turn them to the left side
        • Suction the oropharynx/ET tube
        • Consider applying PEEP
        • Consider postponing surgery
    • Maintenance:
      • Avoid excessive administration of sedating medication
      • Evacuate the stomach
    • Emergence:
      • Awake extubation
      • Confirm adequate reversal of neuromuscular blockade

    Acute Respiratory Distress Syndrome (ARDS)

    • A condition occurring in critically ill patients where fluid accumulates in the alveoli, causing ventilation/perfusion mismatch

    Incidence, Outcomes, and Etiology of ARDS

    • Risk of developing ARDS is additive:
      • 1 risk factor - 25%
      • 2 risk factors - 42%
      • 3 risk factors - 85%
    • Major risk factors: Sepsis, bacterial pneumonia, trauma, aspiration pneumonitis
    • ARDS has a mortality rate of ~50%

    Pathophysiology of ARDS

    • Damage to the alveolar-capillary membrane triggers a diffuse inflammatory response
    • Capillary endothelium: Releases cytokines and membrane-bound phospholipids, activates leukocytes and macrophages, produces microemboli
    • Pulmonary vasoconstriction, bronchoconstriction, altered vascular reactivity/permeability
    • Increased pulmonary vascular resistance with the potential development of cor pulmonale

    Clinical Features and Diagnosis of ARDS

    • Hallmark: Non-cardiogenic pulmonary edema
    • Clinical manifestations: Dyspnea, hypoxemia, diffuse bilateral pulmonary infiltrates, decreased pulmonary compliance
    • ARDS is precipitated by a noxious event (e.g., trauma, bacterial pneumonia)

    Treatment for ARDS

    • Medical: Lung-protective ventilation (supplemental O2), afterload reduction/inotropic support, prone positioning, inhaled nitric oxide (iNO)

    Anesthetic Management for ARDS

    • Maintenance:
      • Ventilation:
        • Consider tidal volume (Vt) 6-8 mL/kg ideal body weight (IBW)
        • Consider PEEP
        • Avoid peak inspiratory pressures (PIPs) >30 cm H20
      • Avoid excessive administration of IV fluids
      • Consider monitoring arterial blood pressure, central venous pressure, cardiac output, and urinary output

    Pneumothorax

    • Simple Pneumothorax: Air accumulation in the pleural space; no communication between the pleural space and the atmosphere
    • Communicating Pneumothorax: Air accumulation in the pleural space due to communication between the pleural space and the atmosphere
    • Tension Pneumothorax: Progressive air accumulation in the pleural space that results in mediastinal shift
    • Hemothorax: Blood accumulation in the pleural space

    Incidence, Outcomes, and Etiology of Pneumothorax

    • Spontaneous (sneezing, coughing)
    • Chest trauma (rib fracture)
    • Barotrauma
    • Subclavian central line insertion
    • Supraclavicular/infraclavicular brachial plexus block
    • Surgical procedures (mediastinoscopy, radical neck dissection, mastectomy, axillary lymph node dissection, nephrectomy)

    ###Clinical Features and Diagnosis of Pneumothorax

    • Hallmark: Decreased SpO2, increased peak inspiratory pressures, tachypnea, hypotension, tachycardia
    • Clinical manifestations: Asymmetric chest wall movement, tracheal shift, hyperresonance
    • Differential diagnosis: High concern in a patient with a history of chest trauma who develops an acute decrease in pulmonary compliance

    Treatment for Pneumothorax

    • Simple Pneumothorax:
      • Catheter aspiration
      • Tube thoracostomy
    • Communicating Pneumothorax:
      • Semi-occlusive dressing
      • Supplemental O2
      • Tube thoracostomy
    • Tension Pneumothorax:
      • Needle thoracostomy
      • Tube thoracostomy
    • Hemothorax:
      • Tube thoracostomy
      • Consider blood transfusion

    Atelectasis

    • A pathological condition characterized by abnormal alveolar gas exchange due to airway collapse.

    Incidence, Outcomes, and Etiology of Atelectasis

    • Occurs in ~90% of patients who receive general anesthesia
    • Develops within minutes and may persist for hours or days
    • Most common after thoracic/upper abdominal surgery
    • The most common cause of postoperative respiratory dysfunction

    Pathophysiology of Atelectasis

    • Blockage or obstruction of airways can result from:
      • Compression of lung tissue
      • Impaired surfactant
      • Absorption of oxygen from nitrogen-free alveoli

    Obstructive Sleep Apnea

    • Mechanical obstruction of the pharynx during sleep due to decreased muscle tone.
    • Obesity is the most significant risk factor, affecting 40% of obese patients and 80% of patients undergoing bariatric surgery.
    • Increasing prevalence in children.
    • Associated with increased morbidity and mortality in hospitalized patients.
    • Results in chronic hypoxemia and hypercarbia, leading to an inflammatory state.
    • Decreases functional residual capacity (FRC) and apneic oxygen reserve.
    • Clinical Features: Daytime somnolence, habitual snoring, and fragmented sleep.
    • Diagnosis: Polysomnography provides objective diagnosis and severity gradation.
    • STOP-Bang Score: Used for preoperative evaluation, requires at least three of the following:
      • Snoring
      • BMI > 35 kg/m²
      • Tiredness
      • Age > 50 years
      • Observed apnea
      • Neck circumference > 40 cm
      • High blood pressure
      • Gender (male)
    • Treatment:
      • Lifestyle: Weight loss.
      • Medical: CPAP, airway devices, medications (modafinil, methylxanthines, tricyclic antidepressants).
      • Surgical: Adenotonsillectomy, uvulopalatopharyngoplasty, hypoglossal nerve stimulator.

    Anesthetic Management of Obstructive Sleep Apnea

    • Preoperative Considerations:
      • Ensure CPAP is available on the day of surgery.
      • Perform thorough airway examination to anticipate difficult mask ventilation and laryngoscopy.
      • Assess Mallampati score and neck circumference.
      • Consider regional anesthesia or multimodal analgesia to minimize sedation.
      • Minimize or avoid sedatives due to increased sensitivity in patients with OSA.
    • Induction:
      • Anticipate difficult mask ventilation and laryngoscopy.
      • Decreased FRC leads to decreased apneic oxygen time.
      • Elevate head and shoulders (ramping).
      • Have airway adjuncts (LMA/videolaryngoscope) readily available.
    • Postoperative Considerations:
      • Monitor ventilation and oxygenation.
      • Consider CPAP in the PACU.
      • Prolonged monitoring (6-24 hours) may be necessary.

    Chronic Obstructive Pulmonary Disease (COPD)

    • Preventable and treatable disease characterized by airflow limitation that is not fully reversible.
    • Airflow limitation progresses and is associated with an inflammatory response in the lungs.
    • Etiology: Cigarette smoking is the most significant risk factor. Other risk factors include environmental pollutants and genetics.
    • Pathophysiology: Inflammatory reaction in the lungs leading to progressive airflow obstruction, decreased FEV1, decreased bronchial lumen size, increased bronchial wall collapsibility, and decreased lung elastic recoil.
    • Clinical Features: Chronic productive cough, progressive exercise limitations, dyspnea, wheezing.
    • Diagnosis: Pulmonary function testing (GOLD Classification):
      • Mild: FEV1 ≥ 80%
      • Moderate: FEV1 50%-79%
      • Severe: FEV1 30%-49%
      • Very Severe: FEV1 < 30%
    • Treatment: Bronchodilators, inhaled corticosteroids, pulmonary rehabilitation, oxygen therapy, smoking cessation.

    Anesthetic Management of COPD

    • Preoperative Considerations:
      • Optimize pulmonary function before surgery.
      • Cessation of smoking.
    • Induction:
      • Rapid sequence induction may be required for difficult airways.
      • Consider using etomidate or propofol for induction, as they are less likely to cause bronchospasm.
      • Avoid succinylcholine due to the risk of hyperkalemia.
    • Maintenance:
      • Consider using sevoflurane, the least irritating volatile anesthetic.
      • Avoid atracurium, mivacurium, morphine, beta-blockers, Hemabate, and NSAIDs due to their potential to induce bronchospasm.
    • Emergence:
      • Deep extubation may be necessary.
      • Consider using sugammadex for neuromuscular blockade reversal to minimize the risk of bronchospasm.
      • Verify adequate reversal of neuromuscular blockade.

    Intraoperative Bronchospasm Management

    • Treatment:
      • Administer additional anesthetic agents.
      • Increase FiO2 to 1.0 (100%).
      • Administer short-acting beta-2 agonist (albuterol).
      • Consider administering epinephrine 10 mcg/kg.
      • Administer a corticosteroid (hydrocortisone 2-4 mg/kg).
      • Consider administering aminophylline.

    Pulmonary Hypertension

    • Defined as a mean pulmonary artery pressure (PAP) greater than 25 mmHg.
    • Etiology: COPD, connective tissue disorders, sarcoidosis, drug effects, genetics, idiopathic.
    • Pathophysiology: Increased vascular tone, pulmonary vascular smooth muscle growth and proliferation, right ventricular overload leading to cor pulmonale.
    • Clinical Features: Dyspnea, exercise intolerance.
    • Treatment: Oxygen therapy, medications (prostanoids, endothelin receptor antagonists, phosphodiesterase inhibitors), heart/lung transplantation.

    Anesthetic Management of Pulmonary Hypertension

    • Preoperative Considerations:
      • Consider ECG, echocardiogram, chest x-ray, and ABG.
      • Continue medications for pulmonary hypertension.
      • Consider regional anesthesia.
    • Maintenance:
      • Neuraxial anesthesia may cause significant hemodynamic alterations.
      • Etomidate or high-dose opioids may be preferable to minimize cardiac depression.
      • Consider arterial blood pressure monitoring.
      • Consider a central venous catheter for major procedures.

    Cor Pulmonale

    • Right heart failure secondary to pulmonary pathology.
    • Etiology: Acute (e.g., PE) or chronic (e.g., COPD).
    • Pathophysiology: Right ventricular dysfunction develops in response to pulmonary hypertension.
    • Clinical Features: Cough, dyspnea, weakness, fatigue, hemoptysis, jugular venous distension, S3 gallop, S4 heart sound, murmur, hepatomegaly, ascites, dependent edema.
    • Diagnosis: Doppler echocardiography (tricuspid regurgitation velocity), cardiac catheterization.
    • Treatment: Oxygen therapy, medications (prostanoids, endothelin receptor antagonists, phosphodiesterase inhibitors, diuretics), heart/lung transplantation.

    Anesthetic Management of Cor Pulmonale

    • Preoperative Considerations:
      • Consider regional anesthesia.
    • Maintenance:
      • Maintain adequate oxygenation.
      • Avoid acidosis.
      • Avoid stimuli that increase sympathetic tone.
      • Avoid hypothermia

    Pulmonary Embolism (PE)

    • Occlusion of pulmonary blood flow by embolic material, resulting in obstruction of pulmonary blood flow.
    • Etiology: Usually caused by deep vein thrombosis (DVT) from the iliofemoral vessels. Other emboli include air, CO2, tumor, bone, fat, and catheter fragments.
    • Virchow's Triad:
      • Venous stasis.
      • Venous injury.
      • Hypercoagulable state
    • Pathophysiology: Thrombus formation, release of thrombus into circulation, occlusion of pulmonary circulation, increased pulmonary vascular resistance (PVR) proximal to occlusion, decreased perfusion distal to occlusion, V/Q mismatch, alveolar damage.
    • Clinical Features: Sudden-onset dyspnea, sudden decrease in EtCO2, hypotension, tachycardia, hypoxemia, wheezing, tachypnea.
    • Treatment: Thrombolytic agents, anticoagulation, embolectomy, IVC filter insertion.

    Anesthetic Management of Pulmonary Embolism

    • Induction:
      • Etomidate is preferred for induction.
      • Avoid ketamine and N2O.
    • Maintenance:
      • Consider high FiO2.
      • Consider monitoring central venous pressure (CVP) and PAP.

    Intraoperative Pulmonary Embolism Management

    • Treatment:
      • Increase FiO2 to 1.0 (100%).
      • Discontinue administration of anesthetic agents.
      • Administer sympathomimetics and fluid/blood as needed.
      • Administer lidocaine or amiodarone in the presence of ventricular dysrhythmias.
      • Prepare for thrombolysis or pulmonary embolectomy.
      • Consider cardiopulmonary bypass as a temporizing measure.

    Restrictive Pulmonary Disease (Pulmonary Edema)

    • Conditions that interfere with normal lung expansion during inspiration.
    • Etiology:
      • Acute intrinsic (e.g., pulmonary edema, aspiration pneumonitis, ARDS)
      • Chronic intrinsic (e.g., idiopathic pulmonary fibrosis, sarcoidosis, radiation injury)
      • Chronic extrinsic (e.g., flail chest, pneumothorax, pleural effusion)
    • Pathophysiology: Imbalance of Starling's forces leading to pulmonary edema:
      • Cardiogenic: High pulmonary capillary pressure.
      • Non-cardiogenic: Increased permeability of the alveolar-capillary membrane.
    • Clinical Features:
      • Hallmark: Pink, frothy sputum.
      • Tachypnea, accessory muscle use, tachycardia, hypertension, diaphoresis, basilar crackles on auscultation.
    • Diagnosis: Chest x-ray (enlarged cardiac silhouette, "white-out" appearance).
    • Treatment: Oxygen therapy, CPAP or mechanical ventilation, fluid restriction, medications (morphine, nitroprusside, inotropes).

    Aspiration Pneumonitis

    • Movement of gastric contents from the stomach to the lungs, resulting in chemical injury to the lung tissue.
    • Incidence: Approximately 1/3000 anesthetics, 1/1500 emergency anesthetics or cesarean deliveries.
    • Etiology: Occurs when protective airway reflexes are inhibited, usually after vomiting or gastroesophageal reflux.
    • Risk Factors: Emergency surgery with a full stomach, bowel obstruction, pregnancy, acute trauma.
    • Pathophysiology: Immediate damage to lung parenchyma by the caustic aspirate, atelectasis, release of inflammatory cytokines by alveolar macrophages, secondary injury, impaired gas exchange, capillary leak, hemodynamic changes, myocardial ischemia, and acidosis.
    • Clinical Features:
      • Hallmark: Arterial hypoxemia.
      • Tachypnea, dyspnea, cyanosis, tachycardia, hypertension.
    • Diagnosis: ABG and chest radiography (demonstrates aspirate in the perihilar and dependent lung regions).

    Aspiration Pneumonitis Treatment

    • Ventilation (low FiO2, PEEP), steroids, lidocaine 1.5 mg/kg, avoid routine administration of antibiotics, avoid routine deep tracheal suctioning/bronchoscopy.

    Anesthetic Management of Aspiration Pneumonitis

    • Preoperative Considerations:
      • NPO status.
      • Recognize risk factors.
      • Pharmacologic prophylaxis:
        • Nonparticulate antacid (sodium citrate with citric acid).
        • H2 receptor antagonist (famotidine).
        • PPI (pantoprazole).
        • Antiemetics (ondansetron).
    • Induction:
      • Consider Rapid Sequence Induction with cricoid pressure.
      • Consider videolaryngoscopy.
      • If vomiting, reflux, or aspiration occur:
        • Tilt the patient's head downward or turn the patient to the left side.
        • Suction the oropharynx/ETT.
        • Consider applying PEEP.
        • Consider postponing surgery.
    • Maintenance: Avoid excessive administration of sedating medication.
      • Evacuate the stomach.
    • Emergence:
      • Awake extubation.
      • Verify adequate reversal of neuromuscular blockade.

    Acute Respiratory Distress Syndrome (ARDS)

    • Condition occurring in critically ill patients in which fluid accumulates in the alveoli, resulting in a mismatch of ventilation and perfusion.
    • Incidence: Risk is additive with multiple risk factors:
      • 1 risk factor: 25% risk.
      • 2 risk factors: 42% risk.
      • 3 risk factors: 85% risk.
    • Risk Factors:
      • Major: Sepsis, bacterial pneumonia, trauma, aspiration pneumonitis.
    • Mortality Rate: Approximately 50%.
    • Pathophysiology: Damage to the alveolar-capillary membrane leading to a diffuse inflammatory response:
      • Capillary endothelium releases cytokines and membrane-bound phospholipids.
      • Complement system activates leukocytes and macrophages, producing microemboli.
    • Clinical Features:
      • Hallmark: Noncardiogenic pulmonary edema.
      • Dyspnea, hypoxemia, diffuse bilateral pulmonary infiltrates, decreased pulmonary compliance.

    Treatment of ARDS

    • Lung protective ventilation (supplemental O2), afterload reduction/inotropic support, prone positioning, inhaled nitric oxide (iNO).

    Anesthetic Management of ARDS

    • Maintenance:
      • Ventilation:
        • Consider VT 6-8 mL/kg IBW.
        • Consider PEEP.
        • Avoid PIPs > 30 cm H2O.
      • Avoid excessive administration of IV fluids.
      • Consider monitoring arterial blood pressure, central venous pressure, cardiac output, urinary output.

    Pneumothorax

    • Simple pneumothorax: Accumulation of air in the pleural space with no communication between the space and the atmosphere.
    • Communicating pneumothorax: Accumulation of air in the pleural space due to communication between space and the atmosphere.
    • Tension pneumothorax: Progressive accumulation of air in the pleural space, resulting in mediastinal shift.
    • Hemothorax: Accumulation of blood in the pleural space.
    • Etiology: Spontaneous (sneezing, coughing), chest trauma (rib fracture), barotrauma, subclavian central line insertion, supraclavicular/infraclavicular brachial plexus block, surgical procedures.

    Clinical Features of Pneumothorax

    • Hallmark: Decreased SpO2, increased peak inspiratory pressures, tachypnea, hypotension, tachycardia.
    • Clinical Manifestations: Asymmetric chest wall movement, tracheal shift, hyperresonance.
    • Treatment:
      • Simple pneumothorax: Catheter aspiration, tube thoracostomy.
      • Communicating pneumothorax: Semi-occlusive dressing, supplemental O2, tube thoracostomy.
      • Tension pneumothorax: Needle thoracostomy, tube thoracostomy.
      • Hemothorax: Tube thoracostomy, consider blood transfusion.

    Atelectasis

    • Pathologic condition characterized by abnormal alveolar gas exchange due to airway collapse.
    • Incidence: Occurs in approximately 90% of patients who receive general anesthesia.
    • Etiology: Compression of lung tissue, impaired surfactant, absorption of oxygen from nitrogen-free alveoli.
    • Pathophysiology: Blockage or obstruction of the airways, decreased compliance.
    • Treatment: Deep breathing exercises, incentive spirometry, early mobilization, supplemental oxygen.

    Respiratory System Anatomy

    • Upper Airway: Includes the nose, mouth, pharynx, and larynx.
    • Nose:
      • Structures: Ala nasi (alar cartilage), anterior nares, nasal vestibules, nasal fossae, nasal septum (vomer bones and cartilages), nasal conchae, nasopharynx, nasal choanae, paranasal sinuses (frontal, ethmoid, maxillary, sphenoid).
      • Functions: Heating, humidification, filtration, olfaction.
    • Pharynx: Muscular tube extending from the skull base to the esophagus at vertebral level C6. Contains tonsils, aggregations of lymphoid tissue.
    • Larynx:
      • Protective structure that prevents aspiration during swallowing, extending from vertebral level C3 to C6. Composed of one bone and nine cartilages, ligaments, muscles, and membranes.
      • Structures: Vestibular folds (fibrous tissue covered by mucous membranes), true vocal cords (fibromembranous folds),
      • Musculature: Various muscles control vocal cord movement and airway protection.
      • Cormack-Lehane Classification: Describes the visibility of the laryngeal structures during laryngoscopy.
    • Trachea: Protective structure that prevents airway collapse, extending from the inferior larynx to the carina. Composed of incomplete rings of cartilage.
    • Bronchi:
      • Neurovascular Structures: Supplied by arteries (bronchial), drained by veins (bronchial), and innervated by both sympathetic and parasympathetic nerves.
      • Bronchodilation: Sympathetic stimulation.
      • Bronchoconstriction: Parasympathetic stimulation, histamine, and slow reactive substance of anaphylaxis.
    • Respiratory Zone: Includes respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.
    • Alveoli: Area of respiratory zone primarily responsible for gas exchange.
    • Pulmonary Hilum: Conduit to the lung, containing the mainstem bronchus, pulmonary circulation, bronchial circulation, lymphatics/lymph nodes, and pulmonary innervation.
    • Thoracic Cavity: Contains the left pleural cavity, mediastinum, and right pleural cavity.
      • Pleura: Serous membrane separating the lungs from the mediastinum and thoracic cage (parietal: lines the chest wall, mediastinum, diaphragm; visceral: lines the lungs).

    Mechanics of Breathing

    • Diaphragm: Primary muscle of inspiration, a bilateral dome that functions independently. Separates the thoracic and abdominal cavities.
    • Boyle's Law: Relates pressure and volume of a gas (P1V1 = P2V2).
      • Inspiration: Increased lung volume, decreased lung pressure.
      • Expiration: Decreased lung volume, increased lung pressure.
    • Pleural, Alveolar, and Transpulmonary Pressures:
      • Pleural Pressure (Ppl): Pressure within the pleural space.
      • Alveolar Pressure (Palv): Pressure within the alveoli.
      • Transpulmonary Pressure: Difference between alveolar and pleural pressure (Palv - Ppl).
    • Lung Compliance: Measure of lung stiffness, indicating the amount of force required to expand the lung. Influenced by elastic forces of lung tissue and surface tension.
    • Lung Volumes:
      • Tidal Volume: Amount of air inspired or expired with each normal breath.
      • Inspiratory Reserve Volume: Extra air inspired with forceful inspiration.
      • Expiratory Reserve Volume: Extra air expired with forceful expiration.
      • Residual Volume: Air remaining in lungs after forced expiration.
    • Lung Capacities:
      • Inspiratory Capacity: Maximum air inspired from normal expiratory level.
      • Functional Residual Capacity: Air remaining in lungs at the end of normal expiration.
      • Vital Capacity: Maximum air expelled after maximal inspiration and expiration.
      • Total Lung Capacity: Maximum air the lungs can hold.
    • Helium Dilution Method: Indirect measurement used to determine lung volumes/capacities that cannot be measured directly (FRC, RV, TLC).

    Ventilation & Gas Exchange

    • Minute Ventilation: Volume of air moved per minute (Tidal Volume x Respiratory Rate).
    • Dead Space: Ventilated areas that do not participate in gas exchange.
    • Alveolar Ventilation: Volume of air available for gas exchange per minute (Respiratory Rate x (Tidal Volume - Dead Space)).
    • Dalton's Law of Partial Pressures: The total pressure of a gas mixture is the sum of the partial pressures of its components.
    • Alveolar Gas Equation: Calculates the partial pressure of oxygen in the alveoli (PAO2).
    • Fick's Law: Describes the diffusion of gases across the alveolocapillary membrane; rate of diffusion is directly proportional to surface area, diffusion coefficient, and pressure difference, and inversely proportional to membrane thickness.

    Oxygen Transport in the Blood

    • Oxygen Transport
      • Physical Dissolution in Plasma: Minimal amount.
      • Bound to Hemoglobin: Majority of oxygen transport.
    • Oxyhemoglobin Dissociation Curve:
      • Rightward Shift: Enhances oxygen release from hemoglobin (increased H+, CO2, temperature, 2,3-BPG).
      • Leftward Shift: Reduces oxygen release from hemoglobin (decreased H+, CO2, temperature, 2,3-BPG).

    Pulmonary Circulation

    • Bronchial Circulation: High pressure, low flow circulation. Supplies oxygenated blood to the conducting zone of the respiratory system.
    • Pulmonary Circulation: Low pressure, high flow circulation. Supplies deoxygenated blood to the respiratory zone for gas exchange.

    Pulmonary System Pressures

    • Right Ventricular Pressure: Pressure in the right ventricle.
    • Pulmonary Artery Pressure (PAP): Pressure within the pulmonary arteries.
    • Pulmonary Capillary Pressure: Pressure within the pulmonary capillaries.
    • Pulmonary Wedge Pressure: Estimate of left atrial pressure.
    • Left Atrial/Pulmonary Venous Pressures: Pressure in the left atrium and pulmonary veins.

    Ventilation-Perfusion Matching

    • Ventilation-Perfusion Ratio (V/Q): Ratio of ventilation to perfusion, normally 0.8. Varies in different lung regions.
      • V/Q = ∞: Dead space (ventilated but not perfused).
      • V/Q = 0: Shunt (perfused but not ventilated).

    Hypoxic Pulmonary Vasoconstriction

    • Systemic Circulation: Vessels constrict in response to decreased oxygen.
    • Pulmonary Circulation: Unique adaptation to shunt blood away from poorly ventilated areas, redirecting it to better ventilated areas.

    Other Important Concepts

    • Surface Tension: Causes collapse of small airways (laplace's law). Surfactant reduces surface tension, preventing alveolar collapse.
    • Starling Forces: Govern fluid movement across the capillary membrane. (Pc, Πif, Pif, Πp)

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