Medical Gas Systems, Cylinder Safety, and Humidity Therapy

What is the fire-risk classification of N and CO2?

nonflammable

T/F, O2 is flammable

False

By what means is oxygen for medical use in a hospital most commonly produced?

Fractional distalation

What is the U.S. Food and Drug Administration (FDA) purity standard for O2?

99%

Which of the following methods of producing O2 is commonly used in the home care setting?

physical separation (sieve)

Large hospital air compressor systems must be capable of maintaining 50 pounds per square inch gauge (psig) at what flows?

100L/min

T/F, helium is heavier than air

False

What key property of He makes it useful as a therapeutic gas?

Low density

Which of the following gases is used to treat conditions causing hypoxic respiratory failure?

NO

Compressed gas cylinders are manufactured from which of the following?

Seamless steel

Department of Transportation (DOT) regulations require compressed gas cylinders to be hydrostatically tested for leaks and expansion every how often?

5-10 years

During inspection of the shoulder of a compressed gas cylinder, you note a plus sign (+) next to the test date. This indicates what about the cylinder?

It can be filled to 10% above its service pressure.

According to the U.S. Department of Commerce, a gas cylinder that is color coded blue should contain what gas

N2O

According to the National Institute of Standards and Technology of the U.S. Department of Commerce, a gas cylinder that is color-coded brown and green should contain what gas

O2-He mixture

In clinical practice, how is a positive identification made of the contents of a medical gas cylinder?

Reading the cylinder label

Which of the following mechanisms do all compressed gas cylinders use to avoid excessively high buildup of cylinder pressure?

pressure-relief mechanism on the valve stem

Cylinders of liquid gases are filled according to what specification?

filling density

The measured pressure in a liquid-filled cylinder is equivalent to what

the pressure of the surface vapor at any given temperature

When full, a gas cylinder registers a pressure of 2200 psig. After a few hours of use, the pressure gauge reads 550 psig. The cylinder is now how full?

One fourth

What is the usual method of monitoring the remaining contents in a gas-filled cylinder?

read the pressure gauge

To accurately determine the remaining contents of a liquid-filled CO2 cylinder, what would you do?

weigh the contents of the cylinder

One cubic foot of any gas is equivalent to how many liters of gas?

28.30

What cylinder factor is used to compute the duration of flow for a 244 cu/ft (H/K) O2 or air cylinder?

3.14

What cylinder factor is used to compute the duration of flow for a 22 cu/ft O2 or air E cylinder?

0.28

The gauge on an H cylinder of O2 reads 2000 psig. About how long would the contents of this cylinder last, until completely empty, at a flow of 6 L/min?

17 hours 30 minutes

The gauge on an E cylinder of O2 reads 800 psig. About how long would the contents of this cylinder last, until completely empty, at a flow of 3 L/min?

1 hour 15 minutes

ou are planning a patient transport that will take about 1 hours. The patient requires manual ventilation with 10 L/min of O2. What is the minimum number of full E cylinders you would take with you?

2

Structural requirements for the central piping systems that are used in hospitals to distribute gases are established by whom?

National Fire Protection Association (NFPA)

The pressure of O2 or air in a bulk supply system is reduced to what standard working pressure?

50 psig

What is the primary purpose of indexed connector systems?

to prevent inadvertent misconnections between equipment

What is the indexed safety system for threaded high-pressure connections between large compressed gas cylinders and their attachments?

American Standard Safety System (ASSS)

Which of the following is false about ASSS standards?

They provide a separate connector for all gases.

Which of the following statements is FALSE about PISS standards?

The exact positions of pins and pinholes do not vary for each gas.

What is the PISS index hole position for O2?

2 and 5

What safety system is designed to prevent accidental interchanging among low-pressure (less than 200 psig) connectors such as those found on flowmeters and ventilators?

DISS

What device is used to reduce the pressure and control the flow of a compressed medical gas?

regulator

if you had to power a ventilator from a large cylinder of compressed gas, which of the following devices would be required?

reducing valve

If you have to deliver medical gas to a patient from a compressed gas cylinder, which of the following devices would you select to control gas flow?

flowmeter

To clean a cylinder valve outlet of foreign material, what should you do?

Quickly open, then close, the valve.

What is the point in the respiratory track where inspired gas reaches body temperature, ambient pressure, saturated (BTPS) conditions?

isothermic saturation boundary

Which of the following is FALSE about the isothermic saturation boundary (ISB)?

Above the ISB, temperature and humidity increase during exhalation.

What is the primary goal of humidity therapy?

maintain normal physiologic conditions

Indications for warming inspired gases include all of the following except:

reducing upper airway inflammation or swelling

Which of the following inspired conditions should be maintained when delivering medical gases directly into the trachea through an endotracheal tube or a tracheotomy tube?

100% RH at 32° to 35° C

What device adds molecular water to gas?

humidifier

Factors affecting a humidifier's performance include all of the following except:

outlet size

What is the most important factor determining a humidifier's performance?

temperature

The greater the temperature of the gas, the:

more water vapor it can hold

All of the following are true about humidification and contact time except:

Low flows decrease and high flows increase relative humidity output.

Simple unheated bubble humidifiers are commonly used to humidify gases with what type of systems?

oronasal oxygen delivery

What is the goal of using an unheated bubble humidifier with oronasal oxygen delivery systems?

Raise the humidity of the gas to ambient levels.

What is the typical water vapor output of an unheated bubble humidifier?

15 to 20 mg/L

Increasing the flow through an unheated bubble humidifier has which of the following effects?

decreasing the water vapor content

To protect against obstructed or kinked tubing, simple bubble humidifiers incorporate which of the following?

pressure relief valve

A design that increases surface area and enhances evaporation by incorporating an absorbent material partially submerged in a water reservoir that is surrounded by a heating element best describes what type of humidifier?

wick

Advantages of passover humidifiers include all of the following except:

They do not require heating to maintain body temperature, ambient pressure, saturated (BTPS) conditions.

Which type of humidifier "traps" the patient's body heat and expired water vapor to raise the humidity of inspired gas?

heat-moisture exchanger

heat-moisture exchangers (HMEs) are mainly used to do what?

warm and humidify gases delivered to the trachea via ventilator circuits

An ideal heat-moisture exchanger (HME) should have an efficiency rating of at least which of the following?

70%

Which of the following best defines an aerosol?

suspension of liquid or solid particles in a gas

The mass of aerosol particles produced by a nebulizer in a given unit time best describes which quality of the aerosol?

output

Which of the following describes the mass of drug leaving the mouthpiece of a nebulizer as aerosol?

emitted dose

Which of the following is a common method to measure aerosol particle size?

cascade impaction

What measure is used to identify the particle diameter, which corresponds to the most typical settling behavior of an aerosol?

mean mass aerodynamic diameter (MMAD)

What measure is used to describe the variability of particle diameters in an aerosol?

GSD

Most nebulizers used in respiratory care produce which type of aerosol suspension?

heterodisperse

What is the retention of aerosol particles resulting from contact with the respiratory tract mucosa called?

deposition

What is the primary mechanism for deposition of large, high-mass particles (greater than 5 μm) in the respiratory tract?

inertial impaction

Where do most aerosol particles in the 5- to 10-μm range deposit?

upper airways

What is the primary mechanism for central airway deposition of particles in the 1- to 5-μm range?

sedimentation

Where do most aerosol particles in the 1- to 5-μm range deposit?

central airways

Which of the following techniques will increase aerosol deposition by sedimentation in the lungs?

10-second breath-hold

What term describes the primary mechanism for deposition of small particles?

Brownian diffusion

What is the primary fate of inhaled aerosol particles that are between 1 and 0.5 μm?

Most are cleared during exhalation.

All of the following drugs or drug categories have been associated with increased airway resistance and bronchospasm during aerosol administration except:

albuterol

Immediately after firing, the aerosol particles produced by most metered-dose inhalers are about how large?

35 μm

Most of the spray generated by the majority of metered-dose inhalers consists of which of the following?

propellant

When fired inside the mouth, what percentage of the drug dose delivered by a simple metered-dose inhaler (MDI) deposits in the oropharynx?

about 80%

A patient with an acute exacerbation of asthma is not responding to the standard dose and frequency of an aerosolized bronchodilator and is now receiving small-volume jet nebulizer (SVN) therapy every 30 minutes. Which of the following would you recommend to the patient's physician at this time?

Consider continuous nebulization of the drug.