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