Test 4 Flashcards
pH
is a measure of the arterial blood’s hydrogen ion concentration and can reveal an acidic or alkalotic condition that can be the result of respiratory or metabolic abnormalities.
PaCO2
is a measure of arterial carbon dioxide and is an important indicator of the adequacy of ventilation.
HCO2
is hydrogen bicarbonite, or bicarbinate for short. It is a product of the renal system used as a buffer to balance CO2 and maintain a normal pH.
BE
Base Excess: represents the amount of an acid required to return pH to normal levels
Norm ranges -2 to 2
BD
Base Deficit represents the amount of a base required to return pH to normal levels.
SaO2
is a measure of the percentage of hemoglobin saturated with oxygen in arterial blood; it is a more accurate depiction of oxygenation than the noninvasive Spo2 provided through pulse oximetry.
Kg to tidal volume
6ml/ kg
How to get RR from target Ve
Using a target V̇e of 100 mL/kg and an established Vt, a RR of 16 bpm would be required to provide adequate V̇e.
If a patient is in volume control ventilation, the respiratory therapist can select either a (wave forms)
constant (square) or decelerating ramp inspiratory flow waveform
With flow triggering
a set level of flow must be subtracted from the bias flow in the ventilator circuit before the machine will deliver a breath.
With pressure triggering
the pressure in the system must decrease to a set level before the machine will deliver a breath.
Flow Volume loop
help identify asynchrony
-also be used to evaluate the degree of airway obstruction and the response to a bronchodilator medication.
Inspiratory flow rate
determines how quickly a volume breath will be delivered and has an impact on the ration of inspiration to expiration (I:E ratio).
-Lower inspiratory flow rates result in longer inspiratory times and shorter expiratory times.
-Higher flow rates result in shorter inspiratory times and longer inspiratory times.
=In volume control ventilation, inadequately set flow may show up as a dip in the pressure waveform as the patient attempts to pull more flow than is available.
air trapping is the same as
auto peep (expiratory hold) -can also be detected on the volume, flow, and pressure waveforms.
Auto-PEEP can be corrected by
extending the expiratory time, or compensated for by setting PEEP close to auto-PEEP levels to reduce the excessive trigger effort required by the patient
One of the main causes of oxygenation defects is
Ventilation/ perfusion (V/Q) mismatch
The primary determinants of oxygenation during mechanical ventilation are
FiO2 and Mean airway pressure (Paw)
Factors that contribute to Paw during mech. ventilation, including
PIP
PEEP
I:E ratio
Flow
The easiest way to manipulate oxygenation across all modes of ventilation is through adjustments in
FiO2 and PEEP
With a current Paco2 of 56 mm Hg and a RR of 16 bpm, we are close to the patient’s normal value, but the pH remains acidic. In an attempt to correct it, we can estimate what the Paco2 will be if we increase the RR to 18 bpm.
Current PaCO2 x Set RR = changed RR x X
56 x 16 = 18 x X
896 = 18x
x = 49.7
While a Pao2 of 110 mm Hg is great by most standards, remember that the patient is on 100% Fio2. We need to wean Fio2 as soon as possible, but we do not want the patient’s oxygenation to fall below acceptable standards. We can predict how much Fio2 is needed to obtain our minimum standard of a Pao2 of 55 mmHg.
Current PaO2/ Current FiO2 = Desired PaO2/ x
110/ 100% = 55/ x
110 x 55/ 100 = x
x = 60.5 or 60% FiO2
Alveolar Ventilation factor of
RR, Vt, Deadspace (Vd/Vt)
The amount of air ventilating active alveoli determine the PaCO2
ABG: pH and CO2
Capnography
Desired RR
Known PaCO2 x known RR/ Desired PaCO2
Desired Vt
Known PaCO2 x known Vt/ Desired PaCO
When not to change PaCO
remember pH is primary
If a metabolic acidosis is present then a low PaCO2 may be helpful
Low PaCO2’s are desirable in neurologic problems
Do not under ventilate to compensate for metabolic alkalosis
If patient is assisting and hyperventilating
Rulee out hypoxemia, anxiety, pain etc
Change to SIMV to allow smaller assisted breaths
Sedate
Add mechanical deadspace (not recommend)
To Increase PaO2 other than increasing FiO2
Increase Mean Airway Pressure (MAP) PEEP Increase I time -Slower flows -Decelerating ramp -wave pattern -Insp. Pause
Effects of PEEP
Increases FRC by recruiting alveoli increases lung compliance improves gas distribution improves oxygenation by reducing shunting
Indications
PaO2 < 60 on FiO2 > 60% A-aDO2 >300 on 100% PaO2 increases less than 10 with FiO2 change of 20% (refractory hypoxemia) shunt > 30% atelectasis reduced Cl
PEEP should be increased/ decreases in incruments of
3-5. allow 5 minutes in between changes
Set PEEP at
influction point
as seen as pressure/ volume loop
set above or below this point
Check before and after change in PEEP
Heart Rate, Rhythm, SaO2, Blood Pressure
