The overall goal of oxygen therapy is to maintain adequate tissue oxygenation, while minimizing cardiopulmonary work. Clinical objectives for O2 therapy are the following:
* correct documented or suspected acute hypoxemia
* decrease symptoms associated with chronic hypoxemia
* decrease the workload hypoxemia imposes on the cardiopulmonary system
O2 therapy corrects hypoxemia by
increasing alveolar and blood levels of O2
In addition to relieving hypoxemia, O2 therapy can help relieve the symptoms associated with certain lung disorders
including dyspnea. O2 therapy also may improve mental function among patients with chronic hypoxemia.
The cardiopulmonary system compensates for hypoxemia by increasing ___________ ____________.
ventilation and cardiac output
Patients with hypoxemia breathing air can achieve acceptable arterial oxygenation only by increasing __________.
ventilation
increased ventilatory demands increases work of breathing. O2 therapy can reduce both the high ventilatory demand and the work of breathing.
Patients with arterial hypoxemia can maintain acceptable tissue oxygenation only by increasing ____________.
Cardiac output
Hypoxemia causes
pulmonary vasoconstriction and pulmonary hypertension. Both together increase the workload on the right side of the heart. This increased work load overtime can lead to right ventricular failure.
American Association for Respiratory Care (AARC) has developed and published
clinical guidelines for O2 therapy
There are three basic ways to determine whether a patient needs O2 therapy.
1. The use of laboratory measures to document hypoxemia.
2. A patient's need for O2 therapy can be based on specific clinical problem or condition.
3. Hypoxemia has many manifestations, such as tachypnea, tachycardia, cyanosis, and distressed overall appearance, and therefore bedside can identify such a need.
Documented hypoxemia as evidenced by
PaO2 less than 60 mmHg or SaO2 less than 90% in subjects breathing room air.
O2 therapy is needed for patients with disorders associated with hypoxemia. Examples are
postoperative patients, trauma, acute myocardial infarction
Careful bedside physical assessment can disclose a patient's need for O2 therapy.
Respiratory- Tachypnea, Dyspnea, and Cyanosis
Cardiovascular- Tachycardia, Hypertension, and Hypotension
Neurologic- Disorientation, Headache, and Restlessness
Five precautions and hazards of supplemental oxygen
1) Toxicity
2) Fire
3) Depressed ventilation
4) Absorption atelectasis
5) Retinopathy of prematurity (ROP)
With FiO2 greater than 0.5
absorption atelectasis, O2 toxicity, or depression of ciliary action or leukocyte function may occur.
O2 toxicity primarily affects the _______ and _________.
lungs and central nervous system
Two primary factors determines the harmful effects of O2:
PO2 and exposure time
Oxygen toxicity effects on the CNS include
tremors, twitching, and convulsions, tend to occur only when patient is breathing O2 at pressures greater than 1 atm.
A patient exposed to a high PO2 for a prolonged period has signs similar to
Bronchopneumonia
Exposure to high PO2
first damages the capillary endothelium. Interstitual edema follows and thickens the alveolar capiollary membrane. If the process continues, type 1 alveolar cells are destroyed, and type II cells proliferate. An exudative phase follows, resulting from alveolar fluid buildup, which leads to a low ventilation/perfusion ratio, physiologic shunting and hypoxemia.
The toxicity of O2 is caused by overproduction of ____________. They are by-products of cellular metabolism. if unchecked, these radicals can severely damage or kill cells.
O2 free radicals
Rather than applying strict cutoffs, the goal should always be to use
the lowest possible FiO2 to achieve adequate tissue oxygenation
Avoiding oxygen exposure to _______% O2 within _______ hours whenever possible.
100, 24
High FiO2 is acceptable if the concentration can be decreased to _______ within ______ days and ______ or less in ____ days.
70% within 2 days
and 50% or less in 5 days
Regardless approach supplement O2
never should be withheld from hypoxic patients.
Depression of ventilation
When breathing moderate to high O2 concentrations, a very small percentage of patients with COPD and chronic hypercapnia may ____________.
ventilate less.
Hypoventilation is not typical of patients with COPD and appropriate management of hypoxemia with supplemental O2
should never be avoided in them
The primary reason some patients with COPD hypoventilate when given O2 is most likely suppression of the ___________.
hypoxic drive
__________________, is an abnormal eye condition that occurs in some premature or low-birth weight infants who receive supplemental O2.
Retinopathy of prematurity (ROP)
ROP most often affects neonates up to approximately ___________ , by which time the retinal arteries have sufficiently matured.
1 month of age
The American Academy Of Pediatrics recommends keeping arterial PO2 in an infant less than _____ mmHg as the best way to minimize the risk of ROP.
80
Giving patients __________ of O2 can help clear trapped air from the abdomen or thorax.
high levels
Because collapsed alveoli are __________________ absorption atelectasis increases the physiologic shunt and worsens blood oxygenation.
perfused but not ventilated
The likelihood of absorption atelectasis is greatest when present with other risk factors associated with low tidal volumes such as
sedation, surgical pain, or CNS dysfunction. In these cases poorly ventilated alveoli may become unstable when they lose O2 faster than it can be replaced. The result is more gradual shrinking of the alveoli that may lead to complete collapse.
_________ seem to pose the greatest risk in operating rooms and in association with selected respiratory procedures.
Fires
Some simple strategies can be used to reduce the fire risk in health care facilities. Effectively managing the __________ of O2, and heat, and feul is key. An essential component is always using the lowest effective FiO2 for a given clinical situation.
Fire triangle
1) Oxygen
2) Fuel
3) Heat
O2 delivery devices traditionally are categorized by design. Three basic designs exist:
low-flow system, reservoir system, and high-flow system
The user judges the performance of an O2 delivery system by answering two key questions
1) how much can the system deliver (FiO2 or FiO2 range)
2) Does the delivered FiO2 remain fixed or vary under changing patient demands
Whether a device delivers a _____________ FiO2 depends on how much of the patient's inspired gas it supplies.
fixed or variable
The greater the patient's inspiratory flow, the more air is breathed, and ___________.
FiO2 is lower
The ____________ always exceeds the patient's flow and provides a fixed FiO2.
high-flow system
A fixed FiO2 can be achieved with a reservoir system, which stores a reserve volume ( Flow X Time) that equals or exceeds the patients tidal volume.
Typical low-flow system provide supplemental O2 directly to the airway at a flow of ____________.
8 L/min or less
Low-flow device is always diluted with air; the result is a ___________.
low and variable FiO2
Low-flow O2 delivery systems include
nasal cannula, nasal catheter, and transtracheal catheter
In most cases a humidifier is used only when the input flow is greater than _________.
4 L/min
Cannulas should not be used in newborns and infants if their nasal passages are obstructed, and flows generally should be limited to _________ unless specialized high-flow cannula system is being used.
2 L/min
The use of nasal catheters is generally limited to ___________ O2 administration during specialized procedures such as a bronchoscopy.
short-term
A nasal catheter should be placed with a new one (placed in the opposite naris) at least every _______.
8 hours
________________ O2 catheter is a thin polytetraflouroethyle (teflon) catheter inserted into the second and third tracheal rings. Because flow is so low; no humidifier is needed.
Transtracheal catheter
Compared with a nasal cannula, a transtracheal catheter needs about _______ of the O2 flow to achieve a given arterial partial pressure of oxygen (PaO2)
half
Low-Flow nasal systems provide O2 concentrations ranging from _____________
22% - 44%
For patients with a normal rate and depth of breathing, each 1 L/min of nasal O2 increases FiO2 approximately ______.
4%
Common problems with low-flow O2 delivery system include
inaccurate flow, system leaks and obstruction, device displacement, and skin irritation.
Reservoir systems currently in use include
reservoir cannulas, masks, and nonrebreathing circuits.
There are two types of reservoir cannula:
nasal reservoir and pendant reservoir
At low flow, reservoir cannulas can reduce O2 use __________.
50% to 75%
A patient at rest who needs 2 L/min through a standard cannula to achieve an arterial oxygen saturation (SaO2) greater than 90% may need only _______ through a reservoir cannula to achieve the same blood oxygenation.
0.5 L/min
The low flow at which the reservoir cannula operates makes humidification ___________.
unnecessary
___________ are the most commonly used reservoir system
Reservoir mask
There are three types of reservoir masks:
1) simple mask
2) partail rebreathing mask
3) nonrebreathing mask
The input range for an adult simple mask is
5 to 10 L /min
The input flow for a nonreabreather is
10 to 15 L/min
At a flow less than ______ with the mask volume acts as dead space and causes carbon dioxide rebreathing.
5 L/min
Because air dilution occurs during inspiration through its ports and around its body, a simple mask provides a _______.
Variable
how much depends on the O2 input flow, the mask volume, the extent of air leakage, and the patients breathing pattern
A ____________ mask, which is much more commonly used than a partial rebreathing mask, prevents rebreathing with one-way valves. during inspiration, slight negative mask pressure closes the expiratory valves, preventing air dilution.
nonrebreathing
Because its a closed system, a leak free nonrbreathing mask with competent valves and enough flow to prevent more than one-third bag collapse during inspiration can deliver _______ source of gas.
100%
Common problems with reservoir mask include
device displacement, system leaks, and obstructions, improper flow adjustment, and skin irritation
To qualify as a high-flow device, a system should provide at least __________.
60 L/min total flow
Adult peak inspiratory flow during tidal ventilation is approximately ________.
three times the minute volume (VE)
All high-flow systems mix air and O2 to achieve a given FiO2. These gases are mixed with
airentrainment devices or blending systems.
Because AEMs dilute source of O2 with air, entrainment devices always provide less than 100% O2. The more air they entrain, the higher total output, but the delivery of FiO2 ________.
is lower
FiO2 provided by air-entrainment devices depend on two key variables
the air-to-O2 ratio and the amount of flow resistance downstream from the mixing site
In the presence of flow resistance distal to the jet, the volume of air entrained decreases. Which less air being entrained, total flow output decreases and the delivered O2
concentrations increases
The two most common air entrainment devices are
the air entrainment mask (AEM) and the air entrainment nebulizer
For controlled FiO2 at flow high enough to prevent air dilution, the total output flow of an AEM
must exceed the patient's peak inspiratory flow
Air entrainment nebulizers should be treated as fixed performance devices only when set to deliver
low O2 concentrations less than 35%
There are two way to assess whether the flow of an air-entrainment nebulizer meets the patient's needs
first, simple visual inspection (as long as mist can be seen), and secondly, assess the adequacy of nebulizer flow is to compare it with the patients peak inspiratory flow (as long as the nebulizer flow exceeds this value, the delivered FiO2 is ensured)
The simplest approach to achieving higher FiO2 with air-entrainment nebulizers is to
add a 50 to 150 ml aerosol tubing reservoir to the expiratory side of the T-tube
Increasing FiO2 capabilities of air-entrainment nebulizers
* Add open reservoir to expiratory side of T tube
* Provide inspiratory reservoir with one-way expiratory valve
* Connect two or more nebulizers together in parallel
* Set nebulizer to low concentrations; bleed-in O2: analyze and adjust
* Use a commercial dual-flow system
High-flow nasal cannula can deliver both FiO2 and relative humidity greater than _____ by using heated, humidified O2 flows up to _______.
90%
40 L/min
The primary types of O2 enclosures used for infants and children are
tents, incubators, and hoods.
With an infant hood, a minimum flow of ________ should be set to prevent accumulation of CO2.
7 L/min
The three Ps are used in the initial selection or recommendation of a change in O2 delivery system
Purpose, Patient, and performance
Patient factors in selecting oxygen therapy equipment
Severity and cause of hypoxemia
Patient age group
Degree of consciousness
Presence or absence of tracheal airway
Stability of minute ventilation
Mouth breathing vs nose breathing patient
The goal is a PaO2 greater than ________ or oxyhemoglobin saturations greater than ________.
60 mmHg
90%
When the SpO2 is consistently ______ or greater on room air, therapy is discontinued.
92%
The therapeutic range of NO is _________, and an initial dose of 20 ppm is commonly used.
2 to 20 ppm
Atmospheric pressure absolute
measure of pressure used in hyperbaric medicine; 1 ata equals 760 mmHg
Bronchopneumonia
Acute inflammation of the lungs and bronchioles, characterized by chills, fever, high pulse and respiratory rates, bronchial breathin, cough with purulent bloody putum, and chest pain.
Bronchopulmonary dysplasia
chronic respiratory disorder characterized by scarring of lung tissue, thickened pulmonary arterial walls, and mismatch between lung ventilation and perfusion. It often occurs in infants who have been dependent on long-term mechanical ventilation
Croup
infectious disorder of the upper airway occurring chiefly in infants and children that normally results in subglottic swelling and obstruction
Exudative
relating to the oozing of fluid and other materials from cells and tissues, usually as a result of inflammation or injury.
Heliox therapy
used to reduce the work of breathing, especially in patients with severe acute asthma or upper airway obstructions, until the primary problem can be resolved
High-flow system
O2 therapy equipment that supplies inspired gases at a consistent preset O2 concentrations.
High-flow nasal cannula
A variation of the standard nasal cannula that can deliver both FiO2 and relative humidity greater than 90% by using heated, humidified O2 with flows up to 50 L/min. Successfully treats moderate hypoxemia through a combination of high FiO2, distending positive airway pressure and meeting or exceeding the patients minute ventilation
Hyperbaric oxygen therapy (HBO)
therapeutic application of O2 at pressures greater than 1 atm (or 760mmHg)
Low-flow system
variable performance O2 therapy device that delivers O2 at a flow that provides only a portion of the patients inspired gas needs.
Neurovascularization
formation of new capillary beds
Neutral thermal environment (NTE)
ambient environment that prevents or minimizes the loss of body heat
Nitric oxide (NO)
an inhaled gas used to reduce pulmonary artery pressure and improve arterial oxygenation
Reservoir system
O2 delivery system that provides a reservoir O2 volume that the patient taps into when the patients inspiratory flow exceeds the device flow
Retinopathy of prematurity (ROP)
abnormal ocular condition that occurs in some premature or low birth weight infants who receive O2
What is the overall goal of O2 therapy
maintain adequate tissue oxygenation while minimizing cardiopulmonary work.
What are the clinical objectives for O2 therapy
Correct documented or suspected acute hypoxemia
Decrease symptoms associated with chronic hypoxemia
Decrease the workload hypoxemia imposes on the cardiopulmonary system
Patients with hypoxemia breathing air can achieve acceptable arterial oxygenation by
increasing ventilation
Patients with arterial hypoxemia can maintain acceptable tissue oxygenation by
increasing cardiac output
Hypoxemia causes pulmonary vasoconstriction and pulmonary hypertension. What effect does that have on the heart?
increases the workload on the right side of the heart. this increased workload over the long-term can lead to right ventricular failure.
What does AARC stand for
American Association for Respiratory Care