O2 Therapy Flashcards
Cardiopulmonary system compensates for hypoxemia by :
- increasing ventilation and cardiac output
Hypoxemia causes:
- pulmonary vasoconstriction
- pulmonary hypertension
three basic ways to determine whether a patient needs
O2 therapy :
• use of laboratory measures such as arterial blood gas testing
• based on the specific clinical problem or condition
• may cause tachypnea,
tachycardia, cyanosis, and distressed overall appearance, and
therefore bedside assessment can help identify such a need
Laboratory measures for documenting hypoxemia include :
■ hemoglobin saturation
■ partial pressure of oxygen (PaO2),
commonly a used threshold for hypoxemia:
PaO2 - <55 to 60 mm Hg
SaO2 - <87% to 90%
condition formerly known as oxygen toxicity is currently termed
hyperoxic acute lung injury.
Hyperoxia
PaO2 greater than 300 mm Hg
In hyperoxia, threshold appears clinically important at
PaO2 of greater than 150 mm Hg
Two factors determine the extent of harmful effects of O2:
• PaO2
• Exposure time
The toxicity of O2 is caused by
Overproduction of O2 free
radicals
Avoiding Oxygen Toxicity Limit patient exposure to 100% O2 to less than 24 hours whenever possible. High FiO2 is acceptable if the concentration can be decreased to 70% within 2 days and 50% or less in 5 days.
High PO2 also is associated with
• retinopathy of prematurity (ROP)
• bronchopulmonary dysplasia in infants.
Although the toxic effects of high
O2 concentrations can be serious, it is not FiO2 but rather PO2 that
results in such harmful effects
Oxygen toxicity
■ Fio2 > 60% longer than 36 hrs
■ Fio2>80%longer than 24 hrs
■ Fio2>100%longer than 12hrs
The user judges the performance of an O2 delivery system by answering two key questions:
● How much O2 can the system deliver (FiO2 or FiO2 range)
● Does the
delivered FiO2 remain fixed or vary under changing patient
demands?
Typical low-flow systems provide supplemental O2 directly to the airway at a flow of
8 L/min or less
Low-flow O2 delivery systems include:
■ nasal cannula
■ nasal catheter
■ transtracheal catheter
-Most commonly used oxygen delivery device
Nasal cannula
FiO2 Range : 22%–40%
Flow : 1/4 –6 L/min (adults)
≤2 L/min (infants)
● Flows greater than 6 to 8 L/min can cause patient discomfort
● should be replaced with a new one
(placed in the opposite naris) at least every 8 hours
● inappropriate for neonatal patients.
soft plastic tube with several small holes at the tip that is inserted by gently advancing it along the floor of either nasal passage and visualizing it just behind and above the uvula
Nasal catheter
Transtracheal catheter
thin polytetrafluoroethylene (Teflon) catheter inserted into the trachea
between the second and third tracheal rings
Transtracheal catheter
● flow is so low, no humidification is needed.
● needs approximately half of
the O2 flow to achieve a given PaO2.
Low-flow nasal systems provide O2 concentrations ranging from
22% to 45%
Common problems with low-flow O2 delivery systems include:
■ inaccurate flow
■ system leaks and obstructions
■ device displacement
■ skin irritation
Reservoir system
● incorporate a mechanism for gathering and storing O2 between patient breaths.
● generally provide higher FiO2 than low-flow systems
● can decrease
O2 use by providing FiO2 comparable with nonreservoir systems but at lower flow
Reservoir system
■ reservoir cannulas
■ mask
■ non-rebreathing circuit
Reservoir cannula
● designed to conserve O2 and are an alternative to the pulse-dose or demand-flow O2 systems
● nasal reservoir cannula operates by storing approximately
20 mL of O2 in a small membrane reservoir during exhalation
● pendant reservoir system helps overcome esthetic concerns by hiding the reservoir under the patient’s clothing on the
anterior chest wall
Reservoir mask
most commonly used reservoir systems
3 types of reservoir mask
■ Simple mask
■ partial rebreathing mask
■ non-rebreathing mask
Simple mask
● disposable plastic unit designed to cover both the mouth and the nose
● If O2 input flow ceases, the patient can draw in air through these holes and around the mask edge.
● input flow range for an adult simple mask is 5 to 10 L/min
Partial rebreathing mask
- Minimum of 10 L/min
High flow delivery system
■ air entrainment mask
■ air entrainment nebulizer
■ high-flow nasal cannula
