Specialty Gases and Air-Oxygen Ratios Study Guide

Vocabulary flashcards covering specialty gases (Heliox, Nitric Oxide), Air-Oxygen ratio calculations, and clinical respiratory therapy fundamentals.

Heliox

A mixture of helium and oxygen that is less dense than oxygen, allowing it to pass through upper airway obstructions more easily.

Helium

The second lightest gas; it does not support combustion and is a key component in heliox mixtures.

80/20 Heliox

A mixture of $80\%$ helium and $20\%$ oxygen used for severe obstructions, requiring a conversion factor of $1.8$ when using an oxygen flow meter.

70/30 Heliox

A mixture of $70\%$ helium and $30\%$ oxygen used for mild obstructions, requiring a conversion factor of $1.6$ when using an oxygen flow meter.

Non-rebreather mask

The preferred delivery device for heliox because it offers a tightly closed system with close to $100\%$ delivery efficiency.

Heliox Conversion Factor

A multiplier applied to the oxygen flow meter setting to determine the actual flow rate, because heliox is less dense than pure oxygen.

Nitric Oxide ($NO$)

A specialty gas used as a selective pulmonary vasodilator to improve blood flow to ventilated alveoli and reduce intrapulmonary shunting.

Persistent Pulmonary Hypertension of the Neonate ($PPHN$)

The primary indication for Nitric Oxide therapy in term or near-term neonates ($>34$ weeks gestation).

Nitric Oxide Starting Dose

$20\,\text{parts per million (ppm)}$.

Rebound pulmonary hypertension

A severe clinical condition and hypoxemia that can occur due to the abrupt discontinuation of Nitric Oxide therapy.

Air:Oxygen Ratio Formula

$\frac{100 - X}{X - 20\text{ or }21}$, where $X$ is the desired $FiO_2$ as a whole number.

$40\%$ FiO2 Ratio

An air-to-oxygen ratio of $3:1$.

$60\%$ FiO2 Ratio

An air-to-oxygen ratio of $1:1$.

Total Flow Calculation

The sum of the air-to-oxygen ratio parts multiplied by the oxygen liter flow from the flow meter.

Inspiratory Flow Demand

The flow required by a patient, typically minimum $2\text{-}3$ times minute ventilation (usually $>40\,L/min$ for adults).

Hypoxic Drive

The physiological drive to breathe that can be suppressed in COPD patients if their $PaO_2$ is not maintained between $55\text{-}65\,mmHg$.

Respiratory Flow (L/sec)

Calculated as $\frac{\text{Tidal Volume (L)}}{\text{Inspiratory Time (sec)}}$.

Ventilator Flow Goal

Typically $45\text{-}60\,L/min$, with $60\,L/min$ often considered optimal to meet peak inspiratory demands.