Oxygen Therapy and Hypoxia - Vocabulary Flashcards

Vocabulary-style flashcards covering key terms and concepts related to hypoxemia, hypoxia, oxygen therapy, and related physiology and clinical considerations.

Hypoxemia

Decreased oxygen levels in the blood.

Hypoxia

Decreased oxygen delivery to tissues.

FiO2 (Fraction of Inspired Oxygen)

Fraction of inspired oxygen concentration (0.21–1.0).

Goals of Oxygen Therapy

1) Correct hypoxemia/hypoxia (PaO2 <60 mmHg or SpO2 <90%),

2) Decrease symptoms (dyspnea, pulmonary hypertension, cor pulmonale, tachycardia, confusion)

, 3) Decrease cardiopulmonary workload.

Indications for Oxygen (Decision Criteria)

Lab values (PaO2, SaO2),

specific conditions (CO/ cyanide poisoning, trauma, MI, PE, CPR),

bedside signs (tachypnea, tachycardia, cyanosis, confusion).

Hypoxemic Hypoxia

A type of hypoxia due to low arterial oxygen (low PaO2) leading to reduced O2 delivery to tissues.

Circulatory (Stagnant) Hypoxia

Hypoxia from failure of the heart to pump adequate blood; treat by increasing cardiac output.

Anemic Hypoxia

Hypoxia from reduced oxygen carrying capacity due to low Hb < ~10 g/dL, or CO poisoning; treat with oxygen and transfusions.

Histotoxic Hypoxia

Tissues cannot use oxygen (e.g., sepsis, cyanide); treat underlying cause.

Normal/Mild/Moderate/Severe Hypoxemia PaO2 Levels

Normal 80–100 mmHg; Mild 60–79; Moderate 40–59; Severe <40.

Age-Related PaO2 Change

After age 60, the lowest acceptable PaO2 tends to decrease ~1 mmHg per year.

Critical Minimum PaO2

PaO2 should be ≥ 55–60 mmHg.

Refractory Hypoxemia

• Hypoxemia that does not significantly improve with supplemental oxygen.

• Criteria from your slides:

  • PaO₂ < 60 mmHg despite FiO₂ > 0.50 (50%).

  • If FiO₂ is increased by 20%, PaO₂ increases by <10 mmHg.

• Cause: True shunting (blood bypassing ventilated alveoli).

• Treatment: Usually requires hyperinflation therapy like PEEP (Positive End-Expiratory Pressure) or CPAP — not just more O₂

Occult Hypoxemia

SpO2 92–96% but SaO2 <88% on ABG; more common in point-of-care settings.

Early Signs of Hypoxemia

Tachycardia, hypertension, tachypnea, dyspnea, pallor, restlessness, headache.

Late Signs of Hypoxemia

Bradycardia, hypotension, arrhythmias, coma, confusion, cyanosis, impaired judgment.

ABG Normal Values

pH 7.35–7.45; PaCO2 35–45 mmHg; PaO2 80–100 mmHg; HCO3- 22–28 mEq/L.

SpO2 Normal vs Critical Values

Normal 95–97%; Critical 87–90%.

Pulse Oximetry Errors

Common sources: poor perfusion, CO poisoning, nail polish, motion, hypothermia, abnormal Hb, light, dyes.

Hazards of Oxygen Therapy

Oxygen-induced hypoventilation,

oxygen toxicity,

retinopathy of prematurity

absorption atelectasis,

fire risk.

Oxygen-Induced Hypoventilation

Chronic CO₂ retainers (ex: severe COPD patients) often have persistently high PaCO₂.

• Titrate O₂ carefully → Use the lowest FiO₂ needed to keep PaO₂ ~50–60 mmHg or SpO₂ ~88–92%.(normal 80-100mmHG, 95%-97%

• But NEVER withhold O₂ → Hypoxemia is more dangerous and life-threatening than the risk of raising CO₂.

• Monitor closely with pulse oximetry or ABGs.

Oxygen Toxicity

PaO2 >150–300 mmHg

Too much O₂ for too long → free radical damage → Acute lung injury (ALI) and fibrosis (scaring).

with free radical injury leading to acute lung injury (ALI)/fibrosis (scaring); limit 100% O2 for <24 hours.

Retinopathy of Prematurity

Neonates exposed to PaO2 >80 torr risk retinopathy.

High PaO₂ (>80) in neonates = risk of permanent blindness (ROP)

Absorption Atelectasis

Nitrogen washout with high FiO2 causing alveolar collapse.

CHAH Mnemonic

Types of hypoxia: Circulatory, Hypoxemic, Anemic, Histotoxic.