MedGas Administration: High Flow Devices, Enclosure Systems, and Titration

Vocabulary practice flashcards covering high flow nasal cannulas, gas blending systems, oxygen enclosures, device selection, and oxygen titration principles.

High Flow Nasal Cannula (HFNC)

An oxygen delivery system delivering flows typically from $30\,\text{L/min}$ to $60\,\text{L/min}$ with an $\text{FiO}_2$ range from room air ($21\%$) to $100\%$, incorporating active or cartridge-based warming and humidification.

Three Required Components of an HFNC System

The essential structural parts of any high flow nasal cannula setup: a patient interface (e.g., cannula or prongs), a gas delivery device that regulates $\text{FiO}_2$ (e.g., a blender or two flow meters), and a humidification system.

PEEP Generation in HFNC

The generation of positive end-expiratory pressure at a rate of approximately $1\,\text{cmH}_2\text{O}$ of pressure for every $10\,\text{L/min}$ of gas delivered, which stents small airways open during inspiration and expiration.

Carbon Dioxide Washout

The flushing of carbon dioxide from the anatomical dead space by high gas flows, which helps lower $\text{PaCO}_2$ in patients with hypercapnic respiratory failure.

Vapotherm

A brand of high flow nasal cannula device that utilizes a paper transfer cartridge to provide warmth and humidification to the delivered breathing gas.

Indications for High Flow Nasal Cannula

Clinical situations appropriate for HFNC, including hypoxemic respiratory failure (e.g., pneumonia), hypercapnic respiratory failure (e.g., COPD exacerbation), reducing the risk of intubation, palliative comfort for DNI or hospice patients, and device intolerance (such as inability to wear a CPAP mask).

Manual Gas Blending Formula

The mathematical method used to mix compressed air and oxygen manually: $\text{O}_2\text{ Flow} = \frac{\text{Total Flow} \times (\%\text{O}_2 - 21)}{79}$ and $\text{Air Flow} = \text{Total Flow} - \text{O}_2\text{ Flow}$.

Oxygen Blender

A precision device connected to $50\,\text{psi}$ compressed air and oxygen high-pressure wall sources (yellow and green hoses) that combines the two gases to allow direct dialing of a specific $\text{FiO}_2$.

Oxygen Blender Quality Control

The safety check required when a blender is first placed on a patient and at least once per shift, performed using a calibrated oxygen analyzer placed at the patient outlet to confirm $\text{FiO}_2$ accuracy.

Oxygen Hood (Oxy Hood)

An infant oxygen enclosure covering only the head that requires flow rates greater than $7\,\text{L/min}$ to flush out carbon dioxide, capable of delivering heated, humidified gas at an $\text{FiO}_2$ from room air to $100\%$.

Noise Amplification in Oxygen Hoods

A known clinical side effect occurring because the high flow from the nebulizer or humidification system generates noise that is amplified inside the enclosed head chamber.

Isolette

A temperature-controlled infant enclosure designed for stable newborns to maintain a neutral thermal environment, capable of administering heated, humidified oxygen via an internal $50\,\text{psi}$ gas source, an oxygen bleed line, or free-flowing gas from an anesthesia bag.

Oxygen Tent

A pediatric enclosure system requiring gas flows of $12\,\text{L/min}$ to $15\,\text{L/min}$ to flush carbon dioxide, delivering a variable $\text{FiO}_2$ of $40\%$ to $50\%$ that fluctuates significantly due to frequent opening and closing.

The Three P's of Device Selection

The clinical decision-making framework for selecting oxygen equipment: Purpose (correct hypoxemia, reduce work of breathing), Patient (age, condition, airway, minute volume), and Performance (device precision and $\text{FiO}_2$ stability).

Emergent Oxygen Therapy

The clinical approach for trauma, cardiac/respiratory emergencies, or suspected tissue hypoxia, calling for the highest possible $\text{FiO}_2$ ($100\%$ if available), typically initiated using a non-rebreather mask.

Critically Ill Adult Oxygen Therapy

The oxygen strategy for patients presenting with moderate to severe hypoxemia, requiring a reservoir or high flow system providing an $\text{FiO}_2$ of at least $60\%$.

Acute-on-Chronic Hypoxemia Management

Oxygen therapy tailored for chronic lung disease patients to prevent suppressing their hypoxic drive, targeting a $\text{PaO}_2$ between $50\,\text{mmHg}$ and $70\,\text{mmHg}$ (saturation between $85\%$ and $92\%$) using low flows of $1\,\text{L/min}$ to $2\,\text{L/min}$ or an air-entrainment mask at $24\%$ to $28\%$.

Desired FiO2 Formula

The mathematical formula used to calculate a target oxygen fraction: $\frac{\text{Known PaO}_2}{\text{Known FiO}_2} = \frac{\text{Desired PaO}_2}{\text{Desired FiO}_2}$.

Protocol-Based Oxygen Therapy

A clinical framework that authorizes respiratory therapists to initiate, modify, and discontinue oxygen therapy within their scope of practice based on systematic patient evaluations rather than requiring a physician order for each change.

Oxygen Titration

The process of adjusting oxygen delivery upward or downward in increments of $1\,\text{L/min}$ to $2\,\text{L/min}$ or small percentage increments to maintain target arterial oxygen saturation ($\text{SpO}_2 \ge 92\%$).

Post-Titration Recheck Times

The time required to reassess a patient following an oxygen adjustment: $10\,\text{minutes}$ for patients with no pulmonary history, and $20\,\text{minutes}$ for patients with a pulmonary history.

Oxygen Discontinuation Criterion

The guideline indicating oxygen therapy should be discontinued when the measured $\text{PaO}_2$ on supplemental oxygen is greater than $5$ times the set $\text{FiO}_2$.

Textbook Weaning Frequency Recommendation

The textbook rule suggesting that a patient's oxygen concentration should be decreased no more frequently than once per shift.