Question 1
List the clinical objectives of oxygen therapy
-Correct acute hypoxemia
-decrease symptoms of chronic hypoxemia
-decrease cardiopulmonary workload associated with hypoxemia
Respiratory therapist
-Gas therapy most common mode of care
medical gases are drugs
Along with physician
Determine desired goals of therapy
Select mode of administration
Monitor patients response
Recommend and implement appropriate changes
Goals:
Maintain adequate tissue oxyge
Question 2
List indications for oxygen therapy
-Documented hypoxemia as evidenced by:
PaO2 less than 60 mmHg or SaO2 less than 90% in subjects breathing room air.
PaO2 or SaO2 below desirable range for a specific clinical situation
-Acute care situations in which hypoxemia is suspected
-Severe trauma
Hypoxemia
an abnormal deficiency of oxygen in the arterial blood
Hypoxia
An abnormal condition in which the oxygen available to the body cells is inadequate to meet their metabolic need. Will cause increased ventilation
Question 3
Describe the different types of hypoxemia - Hypoxemic hypoxia
-Lack of oxygen in the blood
-Example: pulmonary shunting, alveolar hypoventilation, atelectasis
Question 3
Describe the different types of hypoxemia - Anemic hypoxia
-Bloods capacity to carry oxygen is reduced
-Example: decreased Hb level, CO poisoning, excessive blood loss
Question 3
Describe the different types of hypoxemia - Circulatory (stagnant) hypoxia
-Oxygen content and carrying capacity is normal but capillary perfusion is diminished
-Example: shock, decreased heart rate, decreased cardiac output
Question 3
Describe the different types of hypoxemia - Histotoxic hypoxia
-Any condition that impairs the ability of tissue cells to utilize oxygen
-Example: cyanide Poisoning, alcohol poisoning
-Clinically, the PaO2 and Pco2 are normal but tissue cells are hypoxic
What will a lack of O2 in arterial blood cause?
-Increased work of the heart.
By correcting hypoxemia we can prevent or minimize the increased cardiopulmonary workload associated with responses to hypoxemia
Correcting Hypoxemia
O2 therapy corrects hypoxemia by raising oxygen levels of: alveoli and blood
-Hypoxemia and lung disease
Relieves hypoxic symptoms associated with certain lung disorders.
COPD
Interstitial lung disease: Relief of dyspnea. Improve mental function of the ch
Minimizing Cardiopulmonary workload
-Cardiopulmonary systems compensates for hypoxemia by increasing: Ventilation and cardiac output
-Hypoxemic patients breathing room air can only achive acceptable PaO2 by increasing ventilation
-Increased ventilatory demand
-Increased WOB
-O2 therapy decr
Cardiac output compensation for hypoxemia
-When hypoxic: tissue oxygenation is maintained by increased CO
-O2 therapy increases blood oxygen content
decreased cardiac output
Does not have to pump as much blood per minute to meet tissue demands
-Important when heart is stressed by: MI, disease, tr
Hypoxemia causes pulmonary?
-Vasoconstriction(oxygen is vasodilator)
-Hypertension
-Increased work load of the right heart
chronically hypoxemia may lead to Cor Pulmonale
O2 therapy can reverse?
Pulmonary vasoconstriction
-decreased right ventricular work load
Clinical practice guidelines
-Standards for providing safe and effective patient care
-Published and developed by AARC
-Additional guidelines for
Home care oxygenation
Extended care facilities
Neonatal
Pediatric
Question 4
Describe the assessment tools and bedside skill needed to assess the need for oxygen therapy
1st- laboratory measures of hypoxemia: draw blood, saturation monitoring
2nd- Specific clinical problems or conditions
3rd- Manifestations of hypoxemia: Tachypnea, cyanosis, overall appearance and distress
4th-Bedside assessment: SpO2
Laboratory Measures - Hypoxemia
-Hemoglobin saturation
-Carboxyhemoglobin - how much carbon monoxide on hemoglobin
-PO2: PaO2 less than 60mmHg
SPaO2: less than 90%, less than 88% in COPD
-We often make recommendations based on clinical signs
errors in above reading may occur
Question 8
List the clinical problems that may cause hypoxemia
-Postoperative patients
-Carbon monoxide poisoning (CO)
Cyanide poisoning
-shock
-trauma
-Acute myocardial infarction
List clinical signs of hypoxia
Respiratory:
Mild to Moderate: Tachypnea, dyspnea, paleness
Severe: Tachypnea, dyspnea, cyanosis
What do you do if patient is showing signs of hypoxia (tachynea, cyanosis) but pulse oximeter reads 93%?
Put on oxygen since patient is showing signs regardless if saturation showing above 90%
Question 5
List the hazards of oxygen therapy (including hypoxic drive)
-Oxygen toxicity
-Depression from ventilation
-Retinopathy of Prematurity
-Absorption atelectasis
-hypoxic drive
Question 6
Define oxygen toxicity, its affects on the CNS and list precautions to avoid O2 toxicity.
-Affects the lungs and CNS
-Two factors determine harmful effects: exposure time and PO2
-Pulmonary effects may occur at clinical PO2 levels
-Oxygen toxicity CNS: Tremors, twitching, convulsions, symptoms are more pronounced with hyperbaric oxygen(usually
Question 7
List the affects of carbon monoxide poisoning and how it is treated?
effects are headache, dizziness, vomiting, nausea and possibly death
It is treated with breathing 100% of O2
Question 9
Describe how excessive PaO2 levels may cause retinal vasoconstriction.
The pressure is to much so you need to keep the pressure below 80mmHg
What two factors determine harmful effects of oxygen toxicity?
- PO2 - higher (higher FiO2 causes)
- Exposer time - longer
Oxygen Toxicity
-Patchy infiltrates (white areas on xray)
-Major alveolar injury
-Damages the capillary endothelium
-Interstitial edema: (fluids build up in interstitial)
Thickening of the alveolar capillary membrane
Type I cells destroyed
Type II cells proliferate
Oxygen Toxicity Exudative phase
-Damage to alveoli and blood vessels with influx of inflammatory cells into interstitium
-Low V/Q ratios
-Physiological shunting
-Hypoxemia
-End stage
Hyaline membranes form: cellualr debris and condensed plasma preteins that fill the alveolar spaces
Pulm
Oxygen Toxicity continued
-Lung injury worsens
-Blood oxygenation deteriorates
-Progressive hypoxemia treated with additional oxygen
Toxic effects worsen
-Tx with lower FiO2 - pulmonary damage will sometimes resolve
-Low PaO2 to increased FiO2 makes O2 toxicity to increased shunti
Oxygen Toxicity and O2 therapy
-Breathing up to 50% for extended periods without major damage.
We attempt to keep FiO2 less than the 60%
-Weigh both FiO2 and exposure time in assessing risks of high PO2
-Goal should always be to use the lowest possible FIO2 compatible with tissue oxyge
Respiratory Depression
-COPD patient breathing due to hypoxic drive(chronic hypercapnia) which is high CO2 high PaCO2
-central response to carbon dioxide is blunted and the primary stimulus to breath is due to hypoxemic stimulation to the peripheral chemoreceptors
-High levels
Depression of ventilation
-COPD patients with chronic hypercapnia tend to ventilate less when breathing moderate to high O2 concentrations
Suppression of the hypoxic drive
Response to high PCO2 is blunted
Primary stimulus to breathe is hypoxemia
sensed by peripheral chemoreceptors
What is the first priority in Oxygen therapy and COPD
Preventing hypoxia
Retinopathy of prematurity (ROP) or Retrolental Fibroplasia
-Abnormal eye problem occurring in some premature or low birth weight infants
-Excessive PaO2 levels causes retinal vasoconstriction
Leads to necrosis of blood vessels
New vessels form and increase in number
Hemorrhage of the new vessels causes scarring b
Absorption atelectasis
-FIO2 increases 0.50 (60%) percent significant risk
-O2 washes out the Nitrogen (N2) causing alveolar volume to decrease (N2 is thelargest amount of gas in alveoli and blood)
Nitrogen levels decrease thus total pressure of venous gases rapidly decrease.
O
Fire hazard
-Use the lowest effective FIO2 possible
--Scavenging systems to minimize O2 buildup beneath sterile drapes during surgery or while performing tracheostomies can help reduce fire risk
Question 10
What factors should be used in selecting an oxygen delivery system?
Design: Low flow, Reservoir &
High flow systems
enclosures
Performance
How much oxygen can it deliver
FIO2 fixed or variable
FIO2 low: less than 35%, moderate (35 - 60%), high (>60%), full range (21 to 100%)
Question 11
To assure a stable FiO2 under varying patient demands, what must an O2 delivery system do?
If you want it to be stable you must have it deliver all the patients inspired gas. If the device delivers only some of the inspired gas, the patients needs are not met.
-FIO2 variable based on patients Vt, VE(minute volume), RR and patients anatomical re
Question 12
Define and contrast low flow and high flow devices (including minimum and maximum flows) low flow
-Low flow systems: supplemental oxygen directly to the airway at flows of 8L/min or less(exception high flow n/c)
-Total inspired volume or flow is not delivered by the apparatus it is mixed with room air.
-Oxygen provided always diluted with room air.
-L
Question 13
Explain how both of the above are affected by the patients breathing patterns
-The more the patient breathes, the more air dilutes the delivered O2, and FIO2 is lowered
-If the patient breathes less with this type of device, less air dilutes the O2 and FIO2 increases.
-A system that provides only a portion of the inspired gas alway
Question 14
Describe the advantage and disadvantage of high flow nasal cannulas
Advantages: Comfortable delivery, can eat and drink and talk, broad range of flows and O2 concentrations (flexible as patient condition changes), Improved respiratory efficiency, better secretion clearance, alternative for comfort end stage, less changing
Question 12
Define and contrast low flow and high flow devices (including minimum and maximum flows) high flow
Low Flow:
Nasal cannula, .5 to 6 L/min, FiO2: 24-44%, stability: variable use humidifier over 4L
Nasal catheter, 1/4 to 8L/min, FiO2: 22-45%, stability: variable
Transtracheal, 1/4 - 4L/min, FiO2: 22-35%, stability: variable
Reservoir, 1/4 - 4L/min, FiO2:
Low flow system
-Criteria
Should have ventilatory pattern that is consistent and regular
Should have tidal vol in 300 to 700 ml range
Should have respiratory rate that is less than 25 breaths/min
-Assessment of patient
Therapist assessment
Laboratory measurements
Patient
Advantages and disadvantages of low flow system
Advantages: Easy and rapid set up, comfort, low oxygen concentration needs easily met, patient compliance
Disadvantages: variable and limited FIO2, high flow drying and irritation, dislodging, sores from equipment, complications from nasal abnormalities,
Question 15
Describe reservoir devices
-Incorporate a mechanism to gather and store oxygen between patient breaths.
-Draw on this reserve supply whenever their inspiratory flow exceeds the oxygen flow into the device.
Air dilution is reduced. Generally provide higher FIO2s than low flow system
Simple mask:
Input flow range 6-12 L/min
FIO2 range .35 to .55
-Flows greater than 12 L/min to maintain oxygenation,
you should switch to a different system.
Flows at 5L/min or less causes CO2 rebreathing.
Used in ambulance
Partial rebreathing mask
-High concentration but still low flow
-Delivers 60-80% O2 at flow rates of 6-15L/min
-Flowrate must be sufficient to keep reservoir bag at least 2/3 full at peak inspiratio
-No valves on mask
-First part of patients exhaled gas enters the reservoir bag w
Non rebreathing mask
-Delivers 80-95% at flow of 6-15L/min
-flow must be sufficient to keep reservoir bag 2/3 full at peak inspiration
-One way filter valve between mask and reservoir bag, which will not allow exhaled gases into the bag.
-1 to 2 one way flutter valves are loc
High Flow systems
-Supply oxygen concentration at flows equaling or exceeding the patients peak inspiratory flow.
-Air entrainment or blending system
-If flow delivered exceeds patient flow you can ensure a fixed FIO2
-To qualify for high flow device, a system should provi
Nasal Cannula
Normal FIO2 ranges .24- .44 FIO2
-Disposable plastic device
- .5-6L/min
-Use of humidifier above 4 L/min or if patient has drying or nose irritation
-Flows above 6-8 L/min cause patient discomfort.
Nasal dryness, bleeding
High flow N/C with humidity have
Rules of 4
For each L/min of flow an increase of the FIO2 of .04 should occur:
-1L/min: .24
-2L/min: .28
-3L/min: .32 etc
Transtracheal Catheter
-Teflon catheter surgically inserted into the trachea.
between 2nd and 3rd tracheal ring
-No humidifier required
-40 - 60% less O2 to achieve a given PaO2
low as .25L/min to achieve adequate oxygenation
-cheaper, more mobile, smaller flow needed
Performance - Low flow systems
-Nasal low flow system oxygen concentration ranges
Normal range 22% - 44%, max flow of .5L/min to 6L/min most common and most common and comfortable for patient
8L/min could be considered a comfortable flow for some and new high L/min nasal systems that m
Variable affecting FIO2 of low flow oxygen system: Increases FIO2
-Higher O2 input
-mouth closed breathing
-low inspiratory flow
-low tidal volume
-slow rate of breathing
-small minute ventilation
Variable affecting FIO2 of low flow oxygen system: Decreases FIO2
-Lower O2 input
-mouth open breathing
-High inspiratory flow
-high tidal volume
-Fast rate of breathing
-large minute ventilation
Question 16
A cooperative and alert postoperative patient taking food orally requires a low percentage of oxygen to be provided continuously. A precise oxygen concentration is not needed. What is the best choice for this patient?
nasal canula.
Question 17
Name a device that will give a specific percentage of oxygen regardless of the patients respiration's and Vt
venturi mask
Question 18
Describe the benefits and hazards of the different types of oxygen delivery systems
-Nasal Cannula: Advantages: easy, cost, disposable, well tolerated. Disadvantages: Unstable, cause dryness, bleeding, polyps, and mouth breathing lowers FiO2. Best for: patient in stable condition who needs low FiO2, home care. most common method
-Nasal C
Question 19
To ensure a stable FiO2 under varying patient demands, what must a oxygen delivery system do?
It must supply a given O2 concentration at a flow equaling or exceeding the patients peak inspiratory flow.
Question 20
Define a true high flow oxygen delivery system
To qualify as a high flow device, a system should provide at least 60L/min total flow. This flow criterion is based on the fact that the average adult peak inspiratory flow during tidal ventilation is 3x the minute volume. Because 20L/min is close to the
Question 21
Determine which oxygen device is the best choice for a specific patient
...
Question 22
Compute the oxygen percentage of a mixture of air and oxygen
Formula: %O2 = (air flow x 21) + (O2 flow x 100)/ total air
Ex: An air entrainment device mixes a fixed ratio of 3 volume of air to each volume of oxygen. What is the FiO2 %?
(3 x 21) + (1 x 100) = 63 + 100= 163/3+1 = 163/4 = 40%
Question 23
Compute the air to oxygen ratio needed to obtain a given oxygen percentage
Ex: a venti mask is set to deliver 50% O2, at an oxygen input flow of 15L/min. Calculate the air to oxygen ratio needed to obtain this percent and the total output flow delivered to the patient.
Liters of air= (100 - %O2)/ liters O2 (% O2 - 21)
(100 - 50)
Question 24
Know how to use the magic box
Determines O2:air ratio when FiO2 is known:
a. place FiO2 in center
b. subtract FiO2 from 100 and put in bottom right corner
c. subtract FiO2 from 21 and put is left corner.
d. divide value of b from value of c
e. this represents ratio of o2 and air.
f. a
Question 25
Determine what flow may be necessary to meet a patients inspiratory demand
Flow should equal or exceed three times the patients minute volume.
If minute vol is 10L/min it is 10 x 3=30
Air entrainment system
-Direct high pressure oxygen source through a small nozzle or jet surrounded by air entrainment points.
-Entrainment of air varies directly with port size.
size - larger intake, more air entrained.
velocity of oxygen - more air entrained.
-Set to deliver
High flow nasal cannula
-Also known as humidified high flow nasal cannula (HHFNC)
-Delivers high flow of blended oxygen through a special nasal cannula
-effective delivery up to 100 %
-effective humidification as high as 95-100%, heated
Who should use high flow nasal cannula?
-Numerous chronic lung disease
improve gas exchange or reduce work of breathing
-pulmonary fibrosis
-unable to tolerate traditional mask: claustrophobia, burns
-Unable to tolerate NIPPV, Dementia, DNR, End stage
-High flow oxygen therapy should be conside
Salter labs system
-no heated bubble humidifier and specialized n/c, up to 15L/min
-relative humidity 72-78% @ 6-14 L/min
non heated
Vapotherm
-Allows high flows of breathing gases to be delivered by N/C
-Molecular water vapor, saturated (no condensation) at high flows at or above body temp 95-100% humidity
-these attributes - flow, humidity and warmth allow treatment of a broad range of indicat
Mcc system
-delivers up to 100% oxygen with 3 sizes n/c
-meets patients total flow demands
-anatomical dead space flushed
-positive airway pressure throughout respiratory cycle
-optimized mucociliary clearance
-heated humidity 37C, 44 mg/L, 100 % relative humidity