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Flashcards in Resp. therapy equipment Deck (28):

Why is SpO2 so important?

- the presence of hypoxia may change clinical management in over 90% of cases


What are the 2 types of pulse oximeters?

- transmission: light passes through tissue to sensor on the otherside
- reflectance: the sensor and the light source are side by side


What law are the principals of oximetry based on?

- Beer-lambert law
- the concentration of an absorbing substance in a solution is related to the intensity of light transmitted through that solution


What are the 2 diodes that emit alt. light wavelengths?

- red light: absorbed by deoxygenated blood
- infrared light: absorbed by oxygenated blood
- ratio of absorption is measured and the O2 saturation of hb is derived


What are the diff. oximeter probes?

- finger
- ear
- hand/foot (Neonates)
- forehead


What SaO2 % = PaO2 of 80 mmHg?
PaO2 50 mm Hg = ?
What is the nomral PaO2?

- 80 mm Hg = 95% SaO2
- 50 mm Hg = 80% SaO2
- normal PaO2 80-100 mmHg


What indicates that there is a good signal on the oximeter?

- dicrotic notch -> 2 peaks
- but without a good waveform the reading is unreliable (dependent on circulation being intact)


What factors may affect the pulse ox?

- skin pigment: darker pigment may sometimes cause erroneous readings
- nail polish: usually not a problem but darker polish may decrease light transmission
- acrylic nails: decreases accuracy
- motion
- ambient or excessive light
- hypoperfusion: may overestimate
- hypoxia: less reliable below 80%
- dyshemoglobinemias: COHb absorbs light in red wavelength similar to oxyhemoglobin (falsely elevated)
- methemoglobin: Fe3+ vs normal Fe2+ (absorbs red and infrared light)
- IV dyes: methylene blue, indocyamine green, and indigo carmine
- anemia: for any given saturation the PaO2 is lower than normal
- cyanide poisoning: will read a high O2 sat which is true because the O2 is bound very tightly with the Hgb but this isn't the true picture of actual O2 tension in the tissue (very low)


What are indications for use of peak flow meters?

- asthma
- some pts with COPD who have a component of reactive airways disease


What do peak flow meters tell us?

- objective measurement of severity of airway obstruction
- can help providers and pts assess asthma
- may help ID triggers
- peak flow can show changes before the pt becomes symptomatic
- take best out of 3 measurements and determine normals off of chart that comes with the meter
- children and adults use different meters


What should be administered first if on multiple inhalers?

- bronchodilator should be admin first


When are spacers recommended? What is the advantage of them?

- recommend use in elderly and children
- advantage: improve coordination b/t delivery of med from the inhaler and breathing it into the bronchial tubes
- they reduce the amt of med that settles in the mouth and throat


What are the goals of oxygen therapy?

- improve oxygenation
- long term O2 therapy in COPD if needed improves survival, quality of life and decreases all cause hospitalizations. These effects may have an even greater impact on women


Indications for long term oxygen therapy?

- PaO2 less than 88%
- cor pulmonale


What are the different O2 delivery systems?

- nasal cannula
- simple face mask
- venturi mask
- bag-valve mask
- can be delivered with Bi-PAP and CPAP


What are the methods used to deliver home oxygen?

- 3 types of systems are available:
compressed oxygen (Tanks)
liquid oxygen
oxygen concentrators
- oxygen either inhaled through mask or nasal cannula


How does a nasal cannula work? How much O2 does it provide?

- provides up to 44% O2 (6L)
- low flow system in which the Vt mixes with room air
- inspired O2 concentration depends on flow rate through the cannula and the patient's tidal volume


How much does the % FlO2 go up by increasing the O2 flow rate by 1 L/min?

- about 4%
- 1 L/min: 21-24%
- 2 L/min: 25-28%
- 3 : 29-32%


How much O2 can be supplied through a simple face mask?

- 40-60% O2 can be supplied through the O2 port at 5-10 L/min
- minimum flow needed is 5 L/min (need enough flow to wash out CO2 or they are just going to inhale the exhaled CO2)


Describe the venturi mask?

- accurately controls the proportions of inspired O2
- O2 concentrations can be adjusted to 24, 28, 31, 35, and 40%
- used for pt who can retain CO2 and pts who have moderate to severe hypoxemia


Describe the non-breather mask?

- simple mask with reservoir
- provides up to 90% O2
- need flow rates of 8-10 L/min


When should you use a non-breather mask?

- seriously ill, responsive and spontaneously breathing who require high O2 content
- to avoid tracheal intubation if acute intervention produces a rapid change


What is a bag valve mask/ambu bag?

- One way valve
- O2 port for supplemental O2
- adult bags: 1600-2000 ml of tidal volume


What is the disadvantage of the bag valve mask/ambu bag?

- mask must be sealed tightly over mouth and nose. Less volume inspired due to leak or the fact that a one handed squeeze doesn't elicit as much volume
- need to coordinate breaths with any spontaneous respiratory effort


What is oxygen toxicity?

- parenchymal lung injury due to supplemental oxygen
- thought to be secondary to the production of O2 free radicals that result in tissue destruction


What are the potential adverse effects of supp O2?

- absorptive atelectasis: wash out of alveolar N2 and atelectasis may occur if O2 diffuses out of the capillaries faster than entering
- extrapulmonary toxicity: seizures, retinopathy of prematurity can develop in neonates with prolonged elevated PaO2 of greater than 80 mm Hg
- coronary vasoconstriction, decreased stroke volume and cardiac output, bradycardia, and increased vascular resistance
- accentuation of preexisting hypercapnia: increased CO2 assoc with supplemental O2 in pts with chronic compensated respiratory acidosis
- airway injury: larger airway inflammation, erythema and edema, within 6 hours of 90% FlO2
-parenchymal lung injury: destruction of alveolar tissue likely secondary to O2 free radicals causing inflammation and cellular death


How do you prevent oxygen toxicity?

- FlO2 less than 60% likely safe without toxicities
- aim for PaO2 60-70 mm Hg or spO2 90-93% with therapies
- don't be afraid to use O2 if needed short term


What is hypoxic drive?

- chemoreceptors normally rely on CO2 levels to regulate ventilation
- if chronic elevated CO2 levels occur the body resets and becomes less sensitive to elevated CO2 and the drive to breath shifts over to rely on lower levels of O2
- in these pts the addition of supp O2 can decrease the drive to breath and maintain their minute ventilation leading to worsening respiratory failure