JB Learning Chapter 6

Ventilation vs respiration: what's the difference?

Ventilation is air movement in/out of lungs; respiration is gas exchange at alveoli/tissues

What is oxygenation?

The loading of O₂ onto hemoglobin in pulmonary capillaries

What does "V/Q mismatch" mean?

Ventilation and perfusion don't match at the alveoli, leading to hypoxia

Give two causes of high V/low Q (ventilation good, perfusion poor).

Pulmonary embolism; severe blood loss/shock

Give two causes of low V/high Q (ventilation poor, perfusion intact).

Pneumonia; pulmonary edema/asthma/bronchospasm

List the four types of hypoxia.

Hypoxic, anemic, stagnant, histotoxic

Early vs late hypoxia signs?

Early: anxiety, tachycardia, pale/clammy; Late: cyanosis, bradypnea, AMS, low SpO₂

Which drive normally controls breathing?

Hypercapnic drive (CO₂ levels)

What is "hypoxic drive" and who has it?

Breathing driven by low O₂; some COPD patients with chronic CO₂ retention

Should you ever withhold oxygen from COPD patients?

No—give O₂ when indicated and monitor ventilation closely

Define tidal volume in adults (approximate).

~500 mL per normal breath

How do you calculate minute volume?

Tidal volume × respiratory rate

Scenario: RR 10/min, shallow breaths ~200 mL—minute volume?

2,000 mL/min (hypoventilation)

Why do shallow breaths cause hypoxia even with normal RR?

Most air stays in anatomic dead space (~150 mL), so little reaches alveoli

What is anatomic dead space volume in adults?

~150 mL

Name three common pulse sites and when to use them.

Carotid (unresponsive adult), radial (responsive adult), brachial (infant)

What skin signs suggest early shock?

Pale, cool, clammy skin with delayed capillary refill

Capillary refill (CRT): when is it most useful?

In children; CRT >2 seconds can indicate poor perfusion

Define the "perfusion triangle."

Pump (heart), pipes (vessels), fluid (blood)

Match triangle failures to shock types.

Pump→cardiogenic; Pipes→distributive; Fluid→hypovolemic

Stages of shock and key differences?

Compensated (normal BP), decompensated (falling BP), irreversible (organ failure)

Narrow pulse pressure suggests what?

Early shock/poor stroke volume

What MAP is generally needed to perfuse vital organs?

~≥60 mmHg

Define preload and afterload.

Preload: ventricular filling; Afterload: resistance the ventricle pumps against

How does high afterload affect the heart?

Increases workload and may reduce stroke volume/cardiac output

Electrical conduction pathway of the heart.

SA node → AV node → Bundle of His → Purkinje fibers

Three major components of blood and their roles.

Plasma (fluid), RBCs (O₂ carriage), platelets/WBCs (clotting/immunity)

Approximate blood composition by volume.

~55% plasma, ~45% RBCs (hematocrit varies), <1% WBCs/platelets

Main form of CO₂ transport in blood?

As bicarbonate (HCO₃⁻), ~70%

Two other forms CO₂ is carried in.

Dissolved in plasma; bound to hemoglobin (carbaminohemoglobin)

Why can pulse oximetry be misleading in CO poisoning?

CO binds hemoglobin and can show normal SpO₂ despite tissue hypoxia

Normal pulse oximetry range and intervention threshold.

95-100% normal; <90% needs prompt intervention

Arterial vs venous vs capillary bleeding appearance.

Arterial spurts/bright red; venous steady/dark; capillary oozes

What does JVD indicate in shock states?

Impaired right heart filling/obstructive causes (tension pneumothorax, tamponade)

Classic obstructive shock causes.

Tension pneumothorax, cardiac tamponade, massive pulmonary embolism

Tension pneumothorax hallmarks.

Severe dyspnea, unilateral absent breath sounds, hypotension, JVD (late: tracheal deviation)

Cardiac tamponade classic triad (Beck's triad).

Hypotension, JVD, muffled heart sounds

Anaphylactic shock key features.

Vasodilation, capillary leak, bronchoconstriction; hives, wheeze, hypotension

First-line field treatment for anaphylaxis.

Epinephrine IM, airway/oxygen, rapid transport

Neurogenic shock key features.

Warm, dry skin below injury, hypotension with bradycardia

Septic shock pathophysiology (simple).

Infection → vasodilation and leaky capillaries → relative hypovolemia

Burn shock mechanism.

Plasma leakage from capillary damage → hypovolemia

Fluid compartments and approximate distribution.

Intracellular ~70%, interstitial ~25%, intravascular ~5% of body fluid

Hydrostatic vs oncotic pressure roles.

Hydrostatic pushes fluid out; oncotic (albumin) pulls fluid in

What hormones conserve water and sodium in shock?

ADH (water reabsorption) and aldosterone (Na⁺/water retention)

Adrenal medulla hormones and their effects.

Epinephrine/norepinephrine ↑HR, ↑contractility, vasoconstriction, bronchodilation

Kidney hormones important to perfusion.

Renin (BP control), erythropoietin (RBC production)

Signs of respiratory distress vs failure.

Distress: increased effort but adequate gas exchange; Failure: inadequate rate/depth—needs ventilation

Mechanism of inhalation vs exhalation.

Inhale: diaphragm contracts, negative pressure draws air in; Exhale: passive recoil pushes air out

How can an open chest wound impair ventilation?

Breaks negative-pressure seal, preventing effective lung expansion

Define "oxygen delivery" (DO₂) conceptually.

Ventilation + oxygenation + circulation working together to supply tissues with O₂

Internal vs external respiration.

External: alveoli↔blood gas exchange; Internal: blood↔tissue gas exchange

Why does anaerobic metabolism cause acidosis?

Produces lactic acid when O₂ is insufficient

Which organ is most sensitive to hypoxia and how fast?

Brain; irreversible injury can begin in 4-6 minutes

Which spinal cord levels are critical for diaphragmatic breathing?

C3-C5 (phrenic nerve)

Why does sepsis cause warm skin early?

Peripheral vasodilation increases skin blood flow before decompensation

Two reasons pulse ox may read falsely low or high.

Low: poor perfusion/cold extremities; High: CO poisoning/methemoglobinemia

When to use carotid vs radial pulse checks.

Carotid for unresponsive adults; radial for responsive adults with adequate perfusion

Which pulse is best for infants?

Brachial pulse

Primary assessment priority sequence (ABCs).

Airway → Breathing → Circulation

Chain of Survival key first steps for cardiac arrest.

Early recognition, immediate high-quality CPR, rapid defibrillation (AED)

Why does narrow pulse pressure suggest poor stroke volume?

Lower systolic relative to diastolic indicates weak ventricular output

What causes crackles in cardiogenic shock?

Pulmonary edema from fluid backing up into alveoli

Why keep shock patients warm?

Hypothermia worsens coagulopathy and impairs perfusion

What does "mission-critical" respiratory rate mean clinically?

Extremely fast or slow rates can fail to maintain ventilation, requiring assisted breaths

Which quadrant pain suggests gallbladder disease?

Right upper quadrant

Which quadrant pain suggests appendicitis?

Right lower quadrant

Where does most nutrient absorption occur?

Small intestine

A common sign of internal bleeding into the abdomen.

Abdominal distention with tenderness and signs of shock

What does the spleen do and why is it EMS-relevant?

Filters blood/immune role; splenic injury can cause life-threatening internal bleeding

Main difference between arteries and veins functionally.

Arteries carry blood away under high pressure; veins return blood with valves to prevent backflow

Why does vasodilation drop blood pressure?

Larger vessel diameter reduces systemic vascular resistance

What does a bounding pulse suggest?

Possible hypertension or hyperdynamic state (early sepsis)

What does a weak, thready pulse suggest?

Low stroke volume/poor perfusion (shock)

Key difference: respiratory arrest vs cardiac arrest.

Respiratory arrest: no breathing but pulse present; Cardiac arrest: no pulse

Why does hyperventilation lower CO₂ (and pH rises)?

Excessive exhalation of CO₂ causes respiratory alkalosis

Two field interventions that directly improve V/Q matching.

Open/maintain airway with oxygen; position/ventilate to improve alveolar ventilation

How does severe anemia cause hypoxia with normal lungs?

Too little hemoglobin to carry oxygen

Why does massive PE cause sudden hypoxia?

Blocks pulmonary blood flow → ventilation without perfusion (V/Q mismatch)

What is the clinical meaning of "reticular activating system"?

Brainstem network that maintains arousal; hypoxia or perfusion failure → AMS

What endocrine response helps maintain BP early in shock?

Catecholamine release (epi/norepi) causing vasoconstriction and tachycardia

What physical exam finding can hint at neurogenic shock vs other types?

Warm, dry skin with bradycardia rather than cool, clammy tachycardia

Why lay most shock patients supine?

Maximizes venous return/preload to support cardiac output

Why are infants/children prone to faster fluid loss?

Thinner skin, higher surface area, and higher metabolic rate

What is the main danger of full-thickness burns beyond local tissue damage?

Massive fluid shifts → hypovolemia and shock

How does aldosterone affect serum sodium and water?

Increases renal sodium reabsorption and water follows, expanding intravascular volume

Two best immediate actions for life-threatening external hemorrhage.

Direct pressure/tourniquet and rapid transport

Why can severe chest trauma cause obstructive shock?

Tension pneumothorax or tamponade impedes cardiac filling/output

How do baroreceptors respond to falling BP?

Increase sympathetic tone → tachycardia and vasoconstriction

Key difference between anxiety (early hypoxia) and confusion (late hypoxia).

Anxiety = compensated; confusion/AMS = decompensated hypoxia

Ventilation vs respiration: what's the difference?

Ventilation is air movement in/out of lungs; respiration is gas exchange at alveoli/tissues

What is oxygenation?

The loading of O₂ onto hemoglobin in pulmonary capillaries

What does "V/Q mismatch" mean?

Ventilation and perfusion don't match at the alveoli, leading to hypoxia

Give two causes of high V/low Q (ventilation good, perfusion poor).

Pulmonary embolism; severe blood loss/shock

Give two causes of low V/high Q (ventilation poor, perfusion intact).

Pneumonia; pulmonary edema/asthma/bronchospasm

List the four types of hypoxia.

Hypoxic, anemic, stagnant, histotoxic

Early vs late hypoxia signs?

Early: anxiety, tachycardia, pale/clammy; Late: cyanosis, bradypnea, AMS, low SpO₂

Which drive normally controls breathing?

Hypercapnic drive (CO₂ levels)

What is "hypoxic drive" and who has it?

Breathing driven by low O₂; some COPD patients with chronic CO₂ retention

Should you ever withhold oxygen from COPD patients?

No—give O₂ when indicated and monitor ventilation closely