McCall 2021 EMS Exam 2 Review

Airway Management, Ventilation, and Capnography

• Definition and Function of Capnography: Capnography is the noninvasive measurement of the partial pressure of carbon dioxide ($CO_2$) in exhaled breath over time. It provides a real-time graphic representation (a waveform) and a numeric value known as the End-Tidal $CO_2$ ($EtCO_2$). It measures the adequacy of ventilation, perfusion (the delivery of blood to the lungs), and cellular metabolism.

• Emergency Airway Clearing: If an unconscious patient presents with shallow or ineffective breathing and fluid or blood is visible in the mouth, the first action must be to suction the airway.

  • Reasoning: This is prioritized because fluid in the airway presents an immediate risk of aspiration (fluid entering the lungs), which can cause pneumonia or mechanical obstruction. Furthermore, you cannot effectively ventilate a patient if the airway is blocked by liquid or debris.

• Manual Airway Techniques: There are two primary manual methods to open an airway:

  1. Head-Tilt, Chin-Lift Maneuver: This is the standard method used for patients without suspected spinal trauma.

  2. Jaw-Thrust Maneuver: This technique is used specifically when there is a suspicion of spinal or cervical injury. It involves displacing the mandible forward without tilting the head back to maintain spinal alignment.

• Assessment of Inadequate Breathing: Breathing is assessed by observing rate, rhythm, quality, and depth (tidal volume). Signs of inadequacy include:

  • Abnormal rates (too fast or too slow).

  • Shallow chest rise (reduced tidal volume).

  • Use of accessory muscles.

  • Cyanosis (blue skin tint) or altered mental status.

  • Intervention: If breathing is inadequate (specifically if rate or depth is insufficient to sustain life), the provider must provide Positive Pressure Ventilation (PPV), typically via a Bag-Valve Mask ($BVM$).

Cardiovascular Physiology and Pathophysiology

• Path of Blood Flow:

  1. Deoxygenated blood enters the Right Atrium via the Superior and Inferior Vena Cava.

  2. It passes through the tricuspid valve into the Right Ventricle.

  3. It is pumped through the pulmonary valve into the Pulmonary Artery (the only artery carrying deoxygenated blood) to the lungs.

  4. Oxygenated blood returns via the Pulmonary Veins to the Left Atrium.

  5. It passes through the mitral (bicuspid) valve into the Left Ventricle.

  6. It is pumped through the aortic valve into the Aorta for systemic distribution.

• Blood Pressure Dynamics:

  • Systolic Pressure: The pressure exerted against the arterial walls while the Left Ventricle is contracting (ventricular systole).

  • Diastolic Pressure: The pressure exerted against the arterial walls while the Left Ventricle is at rest/refilling (ventricular diastole).

• Myocardial Infarction ($MI$): The formal medical term for a "heart attack." It occurs when a coronary artery is obstructed (usually by a clot or plaque), resulting in the death of myocardial (heart muscle) tissue due to lack of oxygen (ischemia).

• Blood Components and Functions:

  • Red Blood Cells (Erythrocytes): Responsible for carrying oxygen to tissues and removing carbon dioxide via hemoglobin.

  • White Blood Cells (Leukocytes): The primary cells of the immune system, responsible for fighting infection.

  • Platelets (Thrombocytes): Essential for the clotting process (hemostasis).

  • Plasma: The liquid component of blood that transports nutrients, hormones, and waste products.

Shock and Perfusion

• Core Physiology Definitions:

  • Perfusion: The circulation of blood within an organ or tissue in adequate amounts to meet the cells' current needs for oxygen, nutrients, and waste removal.

  • Respiration: The actual exchange of gases ($O_2$ and $CO_2$) at the alveolar level or cellular level.

  • Ventilation: The physical act of moving air into and out of the lungs.

  • Circulation: The movement of blood through the heart and blood vessels.

• The V/Q Ratio: This represents the ratio of Ventilation (V) (air reaching the alveoli) to Perfusion (Q) (blood reaching the alveoli).

  • Application: This is most critically applied in cases of Pulmonary Embolism ($PE$), where ventilation is occurring, but a clot prevents perfusion to that section of the lung, creating a "V/Q mismatch."

• Pharmacology and Shock: Medications such as Atenolol, Metoprolol, and Propranolol are Beta-Blockers.

  • Effect on Shock: These drugs block the effects of epinephrine/norepinephrine on the heart. The first sign of shock is typically tachycardia (increased heart rate) as the body attempts to compensate. Because Beta-Blockers keep the heart rate low, they conceal this first sign, making it harder to detect early compensated shock.

• Types of Shock and Indicators:

  • Hypovolemic Shock: Caused by low fluid volume (bleeding or dehydration). Patients often have a history of trauma, vomiting, or diarrhea.

  • Distributive Shock: Caused by widespread vasodilation (e.g., Septic, Anaphylactic, or Neurogenic shock).

  • Cardiogenic Shock: Caused by the heart failing as a pump (e.g., following an $MI$).

  • Obstructive Shock: Caused by a physical block to blood flow (e.g., Tension Pneumothorax or Cardiac Tamponade).

• Comparison of Hypotension Mechanisms:

  • Hypovolemic Shock causes hypotension through a lack of volume within the vessels.

  • Distributive Shock causes hypotension through a lack of pressure because the "container" (the blood vessels) has suddenly enlarged due to vasodilation, even if the fluid volume remains the same.

• Compensated vs. Decompensated Shock:

  • Compensated: The body is still maintaining a near-normal blood pressure through increased heart rate and peripheral vasoconstriction.

  • Decompensated: The body can no longer maintain blood pressure. A drop in systolic blood pressure (typically below $90\,mmHg$) is the primary indicator that the patient has moved into decompensated shock.

Medical Terminology and Anatomy

• Anatomic Locations:

  • Superior/Inferior: Above/Below.

  • Medial/Lateral: Toward the midline/Away from the midline.

  • Proximal/Distal: Nearer to the trunk/Farther from the trunk (used for extremities).

  • Unilateral/Bilateral: On one side of the body/On both sides of the body.

  • Dorsal/Ventral: Toward the back (posterior)/Toward the belly (anterior).

  • Anterior/Posterior: Front/Back.

• Body Positions:

  • Supine: Lying flat on the back.

  • Prone: Lying face down.

  • Recovery (Lateral Recumbent): Lying on the side.

• Kidney Function: The kidneys serve the critical life function of filtering waste from the blood, maintaining fluid and electrolyte balance, and regulating blood pressure through the renin-angiotensin system.

Assessment Principles

• Triage and Prioritization: We prioritize or triage complaints because immediate life-threats (Airway, Breathing, and Circulation issues) must be managed before secondary or minor injuries to ensure patient survival.

• AVPU Scale: Used to assess a patient's Level of Consciousness ($LOC$):

  • A: Alert (The patient is awake).

  • V: Responsive to Voice.

  • P: Responsive to Pain.

  • U: Unresponsive.

• Pertinent Negatives: These are specific signs or symptoms that are absent, but their absence is significant to the clinical picture.

  • Example: A patient complaining of chest pain who denies having any shortness of breath. The "negative" shortness of breath is "pertinent" to ruling in/out various cardiac or respiratory conditions.

• The Primary Assessment:

  • Purpose: To identify and manage immediate life-threats.

  • Duration: A primary assessment may take longer if life-threats (like a blocked airway or massive hemorrhage) are found, as these must be treated immediately before moving on.

  • Components:

    1. General Impression: Age, sex, level of distress.

    2. Level of Consciousness: AVPU.

    3. Airway: Ensure patency.

    4. Breathing: Assess rate and quality; provide oxygen or ventilation if needed.

    5. Circulation: Check pulse (rate, rhythm, quality), skin (color, temperature, condition), and identify major bleeding.

    6. Transport Decision: Determine if the patient is a "Load and Go" or "Stay and Play."

Life Stages and Specialized Populations

• Infants and Children:

  • Anatomic Differences: They have larger tongues relative to their mouths and narrower airways. Their trachea is more flexible and prone to collapse if the neck is over-extended.

  • Upper Airway Sensitivity: Infants are "obligate nose breathers." Because their airways are so narrow, simple congestion or cold-like illnesses can cause significant respiratory distress as the small amount of swelling significantly increases airway resistance.

• Geriatric Populations:

  • Chronic Disease Susceptibility: Aging leads to decreased immune function, reduced elasticity in the lungs (increased residual volume), and decreased cardiac output, making them more susceptible to disease.

  • Shock in the Elderly: Geriatric patients may not show the classic signs of shock (like tachycardia) because of medications (e.g., Beta-blockers) or an aging heart that cannot increase its rate effectively. Their skin may not show typical changes due to poor peripheral circulation.

Operations and Communication

• Transport and Abandonment: Before leaving a patient at a hospital, you must provide a formal "hand-off" report to a healthcare provider with an equal or higher level of certification. Leaving a patient without this proper transfer of care is legally considered abandonment.

• Refusal of Care: To obtain a legal refusal, the patient must be competent and oriented. The process includes:

  1. Explaining the risks of refusing treatment (up to and including death).

  2. Ensuring the patient understands these risks.

  3. Attempting to persuade the patient.

  4. Obtaining the patient's signature on a refusal form.

  5. Obtaining a witness signature (e.g., a family member or police officer).

• Radio Communications Best Practices:

  • Do: Use plain English, be brief and concise, and wait for a clear frequency before speaking.

  • Avoid: Use of codes (like "10-codes"), slang, or using the patient's name (to maintain privacy/HIPAA).

• Closed-Loop Communication: This theory involves the receiver repeating an order or information back to the sender to confirm it was heard and understood correctly.

  • Example: Leader: "Administer 0.3 mg of Epinephrine." Provider: "Understood, administering 0.3 mg of Epinephrine."

• Subjective vs. Objective Documentation:

  • Subjective: Perceptions or what the patient tells you (e.g., "The patient states he feels dizzy"). Use these for the patient's chief complaint and symptoms.

  • Objective: Measurable facts and observations (e.g., "Patient's pulse is $110\,bpm$" or "Cyanosis noted around the lips"). The majority of the Patient Care Report ($PCR$) should be objective record-keeping.