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30 Cards in this Set
- Front
- Back
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What are the 3 indications for O2 therapy?
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- treat hypoxemia
- decrease work of breathing - decrease myocardial work |
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What is the formula for getting a person's normal PaO2 in the supine position? upright?
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- 103.5-(0.42 * age)
- 104.2-(0.27 * age) plus or minus 4 (standard deviation) |
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What does hypoxemia stimulate?
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- peripheral chemoreceptors, causing an increase in rate and depth of ventilation
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What will O2 therapy reduce the stimulation of?
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- peripheral chemoreceptors & reduce work of breathing
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How long will a patient w/ an increased respiratory rate to maintain an adequate PaO2 be able to maintain the PaO2? Why?
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- only for a short time
- diaphragm fatigue/O2 debt created |
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How does hypoxemia affect the heart?
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- causes increased heart rate and contraction strength
- tries to compensate for decreased PaO2 |
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What is O2 toxicity caused by?
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- FIO2 & time
- generally, an FIO2 greater than 50% for greater than 24 hours |
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How does O2 toxicity manifest itself in the body?
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- pulmonary edema & consolidation
- alveolar cell degeneration & dysfunction - atelectasis - hyaline membrane formation |
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What is hyaline membrane formation?
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- as the alveolit collapse, damaged cells collect in the airways and further affect breathing ability
- these cells are called hyaline cells |
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What are the symptoms of O2 toxicity?
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- retrosternal pain
- cough - dyspnea - paresthesia (tingling, numbing sensation of digits, extremities &/or lips) |
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Explain absorption atelectasis
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- normally N fills 78% of space in alveoli
- w/ high FIO2's (50% & greater), N is washed out - if alveoli is obstructed, O2 will continue to be absorbed from the alveoli to the blood - when alveoli falls below critical volume, it collapses |
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What are the 2 necessary components for absorption atelectasis?
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- high FIO2s
- obstruction |
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Explain O2 induced hypoventilation
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- chronically hypercarbic patients (high CO2 w/ relatively normal pH)
- patient no longer responds to central chemoreceptor stimulation to breathe - responds to stimulation of peripheral chemoreceptors in the carotid bodies to breathe (stimulated mainly at PaO2 less than 60mmHg) - administration of too much O2 can decrease ventilation resulting in increased PaCO2 & acidemia |
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What is RLF?
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(Retrolental Fibroplasia or Retinopathy of Prematurity)
- blindness in premature infants caused by PaO2 greater than 80mmHg for an extended period of time - high PaO2 causes vasoconstriction in retina which leads to necrosis of the blood vessels - new vessels form but they tend to hemorrhage which causes scarring of retina leading to blindness - infants up to 1 month of age are at risk |
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What percentages of O2 concentrations rarely cause O2 toxicity?
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less than 40%
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Has 100% O2 been shown to cause toxicity when used less than 24 hours?
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no
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How do you assess the need for O2 therapy/
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- Lab measurements (Hb sat. & PaO2)
- specific clinical problems in which hypoxia is an attribute or side effect - astute bedside techniques |
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What happens to the first 1/3 of exhaled gas when using a partial rebreather mask?
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- goes back into the bag (from anatomical dead space)
- similar to inspired gas |
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Should you use a partial rebreather mask at low flow rates to increase a patient's PaCO2?
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no
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What do high flow systems meet?
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- meets all patient's demands for gas delivered
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What is HAFOE?
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- High Air-Flow Oxygen Entrainment system
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What are some characteristics of Cascades (combined flow systems)?
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- need a blender or 2 sources to titrate FIO2
- most any FIO2 obtainable - most any flow obtainable |
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What is the formula for determining the FIO2 w/ any combined flow system?
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(1st FIO2 * 1st flow) + (2nd FIO2 * 2nd flow)
_____________________________________________ 1st flow + 2nd flow |
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What is Hypberbaric Oxygen Therapy (HBOT)?
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- therapeutic use of O2 at pressures greater than 1 atm
- pressures are usually expressed in multiples of atmospheric pressure absolute (1 ATA= 760mmHg) |
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How does HBOT affect trapped gas bubbles in the body?
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- decreases their size (Boyle's Law)
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What occurs during HBOT due to increased partial pressure of O2?
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- supersaturation of the plasma (Henry's Law)
- PaO2 levels can reach 1500mmHg - increases O2 transport to areas that are poorly perfused |
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What does generalized vasoconstriction due to HBOT do?
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- can reduce edema & swelling in burns, cerebral edema, and crush injuries
- maintains oxygenation due to increased PaO2 |
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What is the half-life of carboxyhemoglobin under HBO of 3 ATA?
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- 23 minutes
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What is the half-life of carboxyhemoglobin in a patient breathing 100% oxygen?
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- 80 minutes
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What is the half-life of carboxyhemoglobin in a patient breathing room air?
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- 5 hours
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