Chapter 35 Stem Flashcards
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)?
The ISB is normally located just below the larynx (vocal cords).
Which of the following factors cause the isothermic saturation boundary (ISB) to shift farther down into the airways?
Decreased ambient temperature
Increased tidal volume (VT)
Endotracheal intubation
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
Administration of dry gases at flows exceeding 4 L/min can cause which of the following?
Structural damage
Heat loss
Water loss
Inhalation of dry gases can do which of the following?
Increase viscosity of secretions
Impair mucociliary motility
Increase airway irritability
Which of the following inspired conditions should be maintained when delivering medical gases to the nose or mouth?
50% relative humidity (RH) at 20° to 22° C
Which of the following inspired conditions should be maintained when delivering medical gases to the hypopharynx, as when administering oxygen by nasal catheter?
95% RH at 29° to 32° C
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
Clinical indications for delivering cool humidified gas include which of the following?
Postextubation edema
Upper airway inflammation
Croup (laryngotracheal bronchitis)
Epilottitis
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?
Temperture
The greater the temperature of the gas, the:
More water vapor it can hold
Gas leaving an unheated humidifier at 10° C and 100% relative humidity (absolute humidity = 9.4 mg/L) would provide what relative humidity at body temperature?
about 20%
What is the simplest way to increase the humidity output of a humidifier?
Increase the temperature of either the water or the gas
Which of the following is a common way to increase the surface area ratio of humidifiers?
Generate a water droplet aerosol
Expose the gas to a saturated wick
Use a bubble or diffusion head
All of the following are TRUE about humidification and contact time except:
Low flows decrease and high flows increase relative humidity output
Which of the following types of humidifiers are used in clinical practice?
Heat-moisture exchanger
Passover humidifier
Bubble humidifier
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 - 20 mg/L
Increasing the flow through an unheated bubble humidifier has which of the following effects?
decreasing the water vapor content
Unheated bubble humidifiers are of limited effectiveness at flows above which of the following?
10 L/min
Why should you NOT heat the reservoirs of a bubble humidifier used with an oronasal oxygen delivery system?
Condensate will obstruct the delivery tubing
The relief valve on a bubble humidifier serves which of the following functions?
It indicates when flow has been interrupted.
It protects the device from pressure damage.
To protect against obstructed or kinked tubing, simple bubble humidifiers incorporate which of the following?
Pressure relief valve
The typical pressure pop-off incorporated into most simple bubble humidifiers releases pressure above which of the following?
2 psig
When checking an oxygen delivery system that incorporates a bubble humidifier running at 6 L/min, you occlude the delivery tubing, and the humidifier pressure relief immediately pops off. What does this indicate?
normal, leak-free system
At high flow rates, what do some bubble humidifiers produce?
aerosol particles
What are some types of passover humidifiers?
Simple reservoir
Membrane
Wick
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
All of the following are TRUE regarding a membrane-type humidifier except:
A small layer of liquid water remains on both sides of the membrane.
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
Which of the following are types of heat-moisture exchangers (HMEs)?
Simple condenser
Hygroscopic condenser
Hydrophobic ceondenser
Which of the following best describes the performance of a typical hygroscopic condenser HME?
40 mg/L water vapor exhaled; 27 mg/L returned
A heat-moisture exchangers has an efficiency rating of 80%. What does this mean?
Of the exhaled water vapor, 80% returns to the patient on inspiration
An ideal heat-moisture exchanger (HME) should have an efficiency rating of at least which of the following?
90%
All of the following are features of an ideal heat-moisture exchanger (HME) except:
high compliance
All of the following are true of heat-moisture exchangers (HMEs) except:
In-use HMEs have little effect on flow resistance to breathing
For which of the following patients would you select a heated humidifier?
Patient receiving oxygen through a bypassed upper airway
Patient receiving long-term mechanical ventilation
Which of the following methods are used to heat the gas delivered by a heated humidifier system?
Using a wraparound heater (yoke or collar)
Placing a heating element in-line with gas flow
Using a reservoir immersion heater
Placing a “hot plate” at humidifier base
Which of the following is false about a simple heated humidifier (one that does not incorporate a servocontrol mechanism)?
Patient’s airway does affect the controller
Characteristics of a servo-controlled heated humidifier include all of the following except:
Monitors heater temperature
A heated humidifier should trigger both auditory and visual alarms and interrupt power to the heater when the delivered temperature exceeds which of the following?
40° C
What should happen when the remote temperature sensor of a heated humidifier becomes disconnected or fails?
Power to the heater should be interrupted.
Auditory and visual alarms should trigger.
Conditions that can cause temperature “overshoot” with servo-controlled heated humidifiers include all of the following except:
the unit reservoir is refilled with sterile water.
The temperature of gas delivered to a patient’s airway by a servo-controlled heated humidifier should not vary by more than how much?
2° C
Which of the following are necessary features to look for in selecting a heated humidifier?
Water level readily visible
Over-temperature protection
Auditory and visual alarms
Minimal temperature overshoot
Where should you place the thermistor probe for a servo-controlled heated humidifier being used on a patient receiving mechanical ventilation?
In the inspiratory limb of the circuit, near but not at the “wye”
When using a servo-controlled heated humidifier to deliver gas to an infant, the thermistor probe should be placed where?
inside the circuit, outside the incubator, or away from the radiant warmer
What are some potential problems with manually refilled heated humidifier reservoirs?
Cross-contamination and infection
Variable compliance or delivered volume
Delivery of dry and/or hot gases
Which of the following automatic feed systems are used to regulate water levels when using a humidifier with a continuous feed system?
Leveling reservoirs
Flotation controls
Optical sensors
All of the following are contraindications for heat-moisture exchangers except:
When a patient is suffering from hyperpyrexia
All of the following are potential hazards of using heat-moisture exchangers except:
Unintended tracheal lavage from condensate
All of the following are potential hazards of using a heated humidifier during mechanical ventilation except:
Hypoventilation due to increased dead space
A patient receiving ventilatory support is being provided with humidification using a heat-moisture exchanger (HME). A physician orders a bronchodilator drug administered through a metered-dose inhaler (MDI) via the ventilator circuit. Which of the following must be performed to ensure delivery of the drug to the patient?
HME must be removed from the circuit during MDI use
A patient has been supported by a mechanical ventilator using a heat-moisture exchanger for the last 3 days. Suctioning reveals an increase in the amount and tenacity of secretions. Which of the following actions is indicated?
Switch the patient to a large-volume heated humidifier
How often should heat-moisture exchangers be inspected and replaced?
when contaminated by secretions
During routine use on an intubated patient, a heated humidifier should deliver inspired gas at which of the following?
temperature of 33 ± 2° C, with a minimum of 30 mg/L of water vapor
Which of the following are the proper temperature alarm settings for a heated humidifier used during mechanical ventilation?
High 37°C
Low 30°C
The amount of condensation occurring in a heated, humidified gas delivery system depends on which of the following?
Length, diameter, and mass of the circuit
Temperature differential along the circuit
Ambient temperature
Rate of gas flow through the circuit
Which of the following is FALSE about heated humidifier condensate?
It poses minimal infection risk
Which of the following barrier precautions should be used when heated humidifier circuits are changed or removed?
Wearing gloves
Wearing goggles
Which of the following are acceptable means to help minimize the problems caused by condensation in heated humidifier circuits?
Installing water traps in the circuit
Setting heater temperature to 25 to 28° C
When using water traps to help minimize the problems caused by condensation in a heated humidifier ventilator circuit, where would you place the traps?
In both expiratory and inspiratory limbs, at low points in the circuit
All of the following are TRUE when heated wire circuits are used with heated humidifiers except:
The humidifier operates at a higher temperature.
All of the following reduce the risk of nosocomial infection when using heated humidification systems except:
Frequent changing of delivery circuits
What is the most reliable indicator that the gas delivered by a servo-controlled heated-wire humidifier system is fully saturated at the airway?
Observing a few drops of condensate at or near the patient’s airway
In checking a servo-controlled heated-wire humidifier system, you notice that a few drops of condensate tend to form but only near the patient’s airway. Based on this observation, what can you conclude?
The gas at the airway is fully saturated.
When checking a patient attached to a servo-controlled heated-wire humidifier breathing circuit, you notice no visible condensate anywhere in the tubing. Based on this observation, you can conclude that the relative humidity of the delivered gas is which of the following?
less than 100%
When is a heat-moisture exchanger (HME) performing well?
Condensate appears in the attached flex tube
When using nebulizers, where should you place them to minimize risk of contamination?
in the inspiratory limb only, at a high point in the circuit
