Module 10 Flashcards
What percent of O2 is carried in the plasma
2%
How many mL of O2 in 100mL of blood
19mL
How much O2 is dissolved in 100mL of plasma
.3mL
Plasma dissolved oxygen doesn’t play a significant role in oxygen transport
Arterial oxygen concentration is proportional to
HGB saturation
What causes a left shift in the dissociation curve?
Decreased: temp
2,3 DPG
H+
CO
What causes a right shift in dissociation curve
Increased: temp
2,3 DPG
H+
REDUCED AFFINITY
Oxyhemoglobin dissociation curve is a representation of
The relationship between the amount of oxygen bound to the HGB and the partial pressure of oxygen in the blood
Vital tool for comprehending how blood transports & releases oxygen
Saturations greater than 90% are
Independent of PAO2
What is the bore effect?
Tissues have higher amounts of CO2 & therefore hydrogen, which causes a right shift of the curve & unloading of oxygen from the HGB molecule
Tissue light absorbance
Contain pulsations times with HR due to the normal variation in arterial blood volume during each heart beat
Pulse oximetry became standard in
1986
Beer Lambert law states
The concentration of solutes can be determined by the intensity of light transmitted though a substance
Intensity & absorbance are
Inversely related
Of incidence of light intensity & the distance transmitted through a solution is equal, then the
Concentration of solutes can be determined in the extinction coefficient for each solute is know
What are the 4 most common hemoglobin species
Meth
Oxy
Reduced
Carboxy
The pulse oximeter estimates arterial HGB saturation by
Measuring light transmission at 2 wavelengths through a pulsating vascular bed
Light absorbance in tissue can be a
Constant component
Pulsating component
The pulsating component is the result of
Arterial blood pulsations & therefore by comparing light absorbance of the 2 components, the absorbance of the arterial blood can be determined
Most pulse odometers use 2 wavelengths of light
660 (red)
940 (infrared)
The light absorbance of the pulsatilla wavelength is divided by the light absorbance of the non pulse stoke wavelength, yielding
The pulse added absorbance which are independent of intensity & incidence
The pulse added absorbance for both wavelengths are calculated & the ratio is related to
The arterial HGB saturation
What 3 assumptions are made for pulse oximetry to work?
2 light absorbers
Pulsations are all caused by fluctuations in blood volume
One curve is valid for everyone
What are the most common sources of errors with oximetry readings
Dyshemoglobins & IV dyes
Wavelength variability
Signal to noise ratio
Motion
Pulse oximetry can only deal with what 2 concentration
Oxyhemoglobin & reduced HGB
Both carboxy & methe
Absorb light at 1 or both of the wavelengths commonly used
Significant concentrations of either will produce erroneous pulse oximetry values
At the red wavelength of 660, carboxy
Has the same absorbance as oxy
Methe absorbs light at
Both 660 & 940, which means it adds to both the numerator & denominator of the ratio
Rising HGB causes pulse oximetry values to
Decrease until reaching a plateau of 85%
What has little effect on pulse oximetry
Fetal HGB & sickle cell
Nail polish varies—causes low reading
Highly opaque can prevent detection
Diodes vary as much as
15nm
LES light transmission can be corrected by
Measuring dioxide wavelength & discarding outside rage
Utilize different algorithms that correspond to different LED Wavelength
Variability doesn’t affect the ability to follow changes in saturation but can produce differences between sensors
Pulsations component can be less than
1% of the amplitude of the non pulsations component l, which can occur during low profusion states or when the non pulsations component is increased such as with ambient light
What can decrease light interference
Drape or towel
What happens if a pulse is weak
The pulse oximetry will use an automatic gain control that adjusts either the LED intensity or the photodetector amplifier gain
Amplifying gain will also
Amplify background noise
Most pulse odometers display
A waveform that represents pulsation strength after amplification
As ASA physical status increases
Pulse oximetry failure rates increase
A Mispositioned pulse oximetry can
Display correct HR. It an erroneous oxygen value
How is loss of signal compensated?
Increasing signaling average time & ECG synchronization
Should determine the noise signal and then subtract it from the total signal
Difference between earlobe & finger pulse oximetry
Earlobe responds quicker
Finger is more reliable
Response time is also affected by
Signal averaging time
Can range from 1-15 seconds
Longer is more reliable
Pulse pressure variation is the
Aria took it pulse pressure with respirations
Pulses paradox is tied to
Fluid responsiveness especially with positive pressure ventilation
Higher values of PVI are suggestive of
Lower intravascular volume status & stronger probability of hemodynamic response to fluid infusion
As intravascular fluid is infused, variability
Diminishes greatly
PVI is sensitive for any
Physiological factor that diminishes CO
In non wealth environment,
Oxygen or electrical services may/may not be available so equipment must be compact, portable & robust
Cost shouldn’t be a limiting factor, but often is
For volatile agents to be vaporized
A carrier gas must pass through a vaporizing chamber, driven by positive pressure or drawn thigh utilizing the patients inspiratory effort
Drive over is an alternative when
Oxygen cylinder isn’t available
A draw over system has what 4 components
Reservoir tube
Vaporizer
Self inflating bag
Non rebreathing system
The self inflating bag is for
Controlled or assisted ventilation that’s separated by a 1 way valve
Valves ensure flow is directed towards the patient and cannot be Re-entered into the vaporizer
Vaporizer & tubing should be
Low resistance so spontaneous breathing can occur
This is often used as a source of oxygen
Atmospheric air by utilizing a portable oxygen concentrator (inhaled concentration can be increased)
Zeolite granules are used to
Absorb nitrogen from compressed air & the residual oxygen is send to the patient
By using 2 columns of Zeolite, a continuous supply of 95% oxygen can be produced
Zeolite doesn’t exhaust and doesn’t require changing for many years
Oxygen concentrator are able to produce
A supply of oxygen at a rate of 5-10L/min
Why are mechanical ventilators difficult
Due to electrical supply
High gas usage if they are powered by compressed gases
Bellows below the beam expand with
Exhalation & the adjusted weight above the beam & compressed bellows, delivering tidal volume
Important to have monitors that function
Under battery & implement safety features that prevent hypoxia gas delivery
Elevated alveolar anesthetic gas concentration cause
Hypoventilation & decreased intake
Keep I. Mind oxygenation & CO2 removal
