Chapter 42 – Medical Gas Therapy: Key Vocabulary

A comprehensive set of vocabulary flashcards covering key terms, devices, hazards, and therapies discussed in Chapter 42 – Medical Gas Therapy.

Oxygen (O2) Therapy

Use of supplemental oxygen to maintain adequate tissue oxygenation and reduce cardiopulmonary workload.

Hypoxemia

Below-normal arterial oxygen tension (PaO2 < 60 mm Hg) or saturation (SaO2 < 90 %).

FiO2

Fraction of inspired oxygen; the percentage or concentration of oxygen in the gas mixture a patient breathes.

PaO2

Partial pressure of oxygen dissolved in arterial blood, normally 80–100 mm Hg at sea level.

SaO2

Percentage of hemoglobin saturated with oxygen in arterial blood; normal is 95–100 %.

PaCO2

Partial pressure of carbon dioxide in arterial blood; elevated levels may depress ventilation in some patients on oxygen.

Ventilatory Depression

Reduction of spontaneous breathing drive, which can occur at PaO2 ≥ 60 mm Hg in some chronic hypercapnic patients.

Oxygen Toxicity

Cellular damage to lung or CNS caused by prolonged exposure to high FiO2 (> 0.50).

Absorption Atelectasis

Collapse of alveoli when high FiO2 replaces nitrogen, allowing oxygen to be absorbed into blood and reducing alveolar volume.

Retinopathy of Prematurity

Retinal vessel damage in premature infants exposed to PaO2 > 80 mm Hg.

Low-Flow System

Oxygen delivery device that provides supplemental O2 at flows below the patient’s inspiratory demand, resulting in variable FiO2.

Reservoir System

Delivery device that stores oxygen between breaths to conserve gas and deliver higher FiO2 (e.g., masks, reservoir cannulas).

High-Flow System

Device supplying a fixed FiO2 at flows meeting or exceeding patient’s peak inspiratory flow (≈ ≥ 60 L min⁻¹).

Nasal Cannula

Most common low-flow device; delivers FiO2 0.24–0.40 at ¼–8 L min⁻¹ (humidify ≥ 4 L min⁻¹).

Nasal Catheter

Thin catheter placed through nostril behind uvula; delivers FiO2 0.22–0.45 at ¼–8 L min⁻¹; rarely used today.

Simple Mask

Reservoir mask requiring 5–10 L min⁻¹ input; provides FiO2 0.35–0.50; < 5 L min⁻¹ risks CO2 rebreathing.

Partial Rebreathing Mask

Mask with reservoir bag (no valves); ≥ 10 L min⁻¹ flow; delivers FiO2 0.40–0.70.

Nonrebreathing Mask

Mask with one-way valves preventing room-air dilution and rebreathing; ≥ 10 L min⁻¹; delivers FiO2 0.60–0.80.

Air-Entrainment Device

High-flow system using a jet and ports to mix air and O2; FiO2 depends on air-to-O2 ratio and downstream resistance.

Back Pressure

Resistance distal to entrainment ports that decreases entrained air, raising delivered FiO2 and reducing total flow.

High-Flow Nasal Cannula (HFNC)

Heated, humidified system that delivers high FiO2 at flows meeting minute ventilation, creating positive airway pressure.

Oxygen Blender

Precision device that mixes pressurized air and O2 through matched regulators and proportioning valve to set exact FiO2.

Oxyhood

Clear plastic enclosure around an infant’s head providing controlled FiO2 with humidified gas.

Incubator (Isolette)

Infant enclosure providing thermal regulation; may be combined with oxyhood for oxygen delivery.

Oxygen Tent

Loose-fitting pediatric enclosure; FiO2 control and temperature regulation are difficult.

Three Ps (Device Selection)

Purpose, Patient, Performance—criteria for choosing an oxygen delivery system.

Hyperbaric Oxygen (HBO) Therapy

Breathing 100 % O2 at pressures > 1 atm to achieve hyperoxygenation and other physiologic effects.

Multiplace Chamber

Large HBO chamber holding several people with air locks; patient breathes O2 via mask or hood.

Monoplace Chamber

Single-patient HBO chamber pressurized entirely with oxygen.

Boyle’s Law (Bubble Reduction)

Gas pressure inversely relates to volume; used in HBO to shrink gas emboli or decompression bubbles.

Neovascularization

Growth of new blood vessels stimulated by HBO to aid chronic wound healing.

Decompression Sickness

Condition of inert gas bubble formation treated with HBO (also called “the bends”).

Nitric Oxide (NO) Therapy

Inhaled gas that selectively dilates pulmonary vessels, improving oxygenation and reducing pulmonary hypertension.

Methemoglobinemia

Oxidized hemoglobin (Fe³⁺) incapable of carrying O2; potential adverse effect of NO therapy.

Heliox

Mixture of helium and oxygen (e.g., 80 : 20 or 70 : 30) used to decrease airway resistance and work of breathing.

Heliox Correction Factor

Multiplier applied to O2 flowmeter reading because helium’s low density alters indicated flow (1.8 for 80 : 20, 1.6 for 70 : 30).

Carbogen

Gas mixture of CO2 and O2 (5 % or 7 % CO2) used for hiccoughs, CO poisoning, or during cardiopulmonary bypass.

Absorption Atelectasis Risk Factors

High FiO2, low tidal volume, or obstructed airways leading to alveolar collapse as O2 is absorbed.

Reservoir Cannula

Nasal device with small chamber (or pendant) that stores O2 during exhalation, conserving 50–75 % of oxygen use.

Minute Ventilation

Volume of gas inhaled or exhaled per minute (tidal volume × respiratory rate).

I:E Ratio

Inspiratory-to-expiratory time ratio; longer inspiratory times increase FiO2 with low-flow devices.

Back-up Valve (Nonrebreather)

One-way valve atop reservoir bag allowing O2 inflow during inspiration and preventing exhaled gas entry.

Downstream Flow Resistance

Obstruction after air-entrainment site that changes FiO2 and total flow output.

Bleomycin / Paraquat Caution

Patients receiving these drugs can develop worsened lung injury with high FiO2.

Fire Hazard

Increased risk of ignition during procedures (e.g., laser bronchoscopy) and in environments with elevated FiO2.