Ventilators Flashcards
Basic starting vent settings for asthma patient
Vt, FiO2, f, I:E, control type, PPlat, PIP
Vt-6-8 ml/kg
Fio2- 100% (1.0)
f- 8-10
I:E- 1:4 or 1:5
Pressure control preferred
PPlat- <30 cm/H20
PIP < 50 cm/H20
permissive hypercapnia
What is the starting peak inspiratory flow volume? (L/min)
50-60 L/min
What is CMV (AC) and what characteristics are involved.
- no spon. resp.
- sets min # of bpm with SET Vt
- can deliver an assisted breath to augment a spon one at a SET Vt
SIMV
- patient must have some spon. breaths
- get a min. # of bpm at SET Vt
- Spon breaths at the patients Vt
What is PSV and how does it affect the patient?
Assist inhalation by giving additional pressure to “blow the breath in”. Decreased WOB.
What is Volume controlled ventilation?
MD sets Vt for each breath
the pressure required to achieve that Vt can vary
Describe Pressure controlled ventilation? (what it is, wave form and effect on the patient).
MD sets insp. pressure and I:E ratio
creates a decelerating wave form pattern
less WOB than VCV
What may unprogrammed auto-PEEP indicate?
breath stacking/CO2 retention
What components determine the Ve?
minute volume
usually 100ml/kg
comprised of f and Vt
smaller Vt require faster f
slower f requires higher Vt to achieve the same Ve
What is Vt ? How much is the volume generally? How is this volume distributed in the lungs?
Tidal volume, 500ml or 5-8ml/kg in men. represents the volume in inhaled air that reached the alveoli of about 350ml plus another 150ml in the anatomic dead space.
What is the IRV?
inspiratory reserve volume- how much more air can you breath in after a normal breath
What is the RV?
residual volume- the amount of air remaining in the lungs after MAXIMAL expiration
What is the IC?
inspiratory capacity- the maximal volume of air that can be inspired after maximal exhalation.
What is the VC?
vital capacity- the volume of air that can be exhaled after the deepest possible inspiration
What is the FRC?
functional residual capacity- the volume of air remaining in the lungs at the end of a normal expiration
Two main types of resp failure
Hypoxic and hypercapnic/failure to oxygenate or failure to ventilate
What is the Flow rate? What is the measurement?
the SPEED at which a prescribed Vt is given. Usually 40-60L/min.
Pros & Cons of high flow rates
- decrease inspiratory time (allowing for longer exp time, allowing for less air trapping and CO2 exhalation PRO
- Increases PIP 2nd more turbulent flow CON
- may lead to maldistribution of gases in alveoli CON
- required to achieve high MV CON
Pros & Cons of low flow rates
- increased inspiratory time
- decreased PIP 2nd more laminar flow
- may improve as distribution in alveoli
What are the Pores of Kohn?
holes between alveoli allowing for collateral airflow between alveoli
Four main types of flow wave patterns
- square
- sinusoidal
- accelerating
- decelrating
Four Benefits of decelerating flow wave?
- may improve gas distribution in alveoli
- decreases dead space
- increases PaO2 tension
- reduces PIP
PxO2/PxCO2, what are the four x components?
a- arterial
A-alveolar
v - venous
c- capillary
PxO2/PxCO2, what are the x components
a- arterial
A-alveolar
v - venous
c- capillary
What is the PaO2 and it’s range?
75-100 mmHg Partial pressure of O2 in the arterial blood
What is the PvO2 and it’s range?
30-40 mmHg (remember it is similar to pH) Partial pressure of O2 in the venous blood
What is the PaCO2 and its range?
35-45 mmHg Partial pressure of CO2 in the artery
What is the PvCO2 and it range?
40-50 mmHg (remember it will be higher than arterial because venous blood carries CO2 back to lungs for exhalation) Partial pressure of CO2 in the vein
What is the SpO2 and it’s range?
peripheral O2 saturation at >92% to 100%
What is the SaO2 and its range?
SaO2 is the percentage of available binding sites on hemoglobin that are bound with
oxygen in arterial blood 95-100%
Vent correction for excessive oxygenation and ranges?
PaO2>100mmHg or SaO2 100% - decrease f or FiO2
Vent correction for inadequate oxygenation and ranges?
PaO2 <60mmHg or SaO2 < 90% - ^ FiO2, ^ PEEP
Vent correction for resp. acidosis and ranges ?
Ph < 7.35 or PaCO2 > 45 mmHg - ^Vt, ^ RR
Essentially, Ve must be increased.
Vent correction for resp. alkalosis and ranges? (pH and CO2 levels)
pH >/= 7.45 or PaCO2 <35mmHg -
< f because they are blowing off too much CO2
What part of the wave form would indicate a patient triggered breath?
a negative deflection from baseline
What kind of waveform would indicate a machine triggered breath?
No negative deflection from baseline just prior to inspiration.
What type of breathing pattern would likely produce a sinosoidal wave pattern?
Spontaneous breaths
The expiratory flow scalar not returning to baseline prior to the next inspiration is indicative of what condition?
Air trapping
If an expiratory volume scalar does not return to baseline at the end of expiration, what two conditions could this indicate?
Air trapping or an air leak. Not as much air returned as was put in the lung. It either escaped (leak) or stayed in the lung (air trapping). The leak could be a anatomical like a pneumothorax or an equipment leak.
How would you diagnose a leak using scalar waves?
If the volume scalar wave it not returning to baseline, but the flow waveform is.
How would you diagnose air trapping with the volume and flow waveforms?
Both waveforms will fail to return to baseline at the end of expiration.
What does the Pplat measure?
The pressure in the alveoli
How is the Pplat obtained?
Via an inspiratory hold at the end of inspiration.
What does the PIP measure?
Alveolar pressure plus the pressure in the airways (bronchus etc).
What is the Paw?
Mean airway pressure over one breath cycle
Describe the relationship between volume and pressure between PCV and VCVC
With PCV pressure is set and volumes vary, with VCV, volumes are set and pressures vary
What is the delta P and how is it calculated?
The Pplat - PEEP
First adjustment to make for an elevated CO2
decrease mechanical dead space if capable then Increase f
What is the formula for a new f to address an increase in CO2?
New f = known f x known co2 / desired CO2
What is the formula for a new Vt to address an increase in CO2?
New Vt = known Vt x Known C02 / desired CO2
What is the formula for a new Ve to address an increase in CO2?
New Ve = known Ve x known CO2 / desired CO2
Va stands for?
Alveolar ventilation
VCO2 stands for
CO2 production
Ve stands for? and is comprised of ?
Minute ventilation, f and Vt
Vd stands for ?
Deadspace ventilation
How is respiratory acidosis corrected via vent settings?
By altering Vt or f
OHDC left shift mnemonic
“Low Down Paco”. All parameters go down EXCEPT for PaCO2
OHDC right shift mnemonic
“UpHright”. All components EXCEPT pH go UP
Components of OHDC
pH, PaCO2, temp, 2-3 DPG
How does 2-3 DPG affect O2 binding?
A decrease causes a left shift and tighter O2 binding.
Three causes of lowered 2-3 DPG
- Multiple blood transfusions
- HyPOphosphatemia
- HyPOthyroidism
Three causes of elevated 2-3 DPG
- Anemia
- Chronic Hypoxemia
- Hyperthyroidism
What is static compliance? How is is measured?
Measures the elasticity of the lung tissues. Vt / Pplat-PEEP. Usually 45-50 cmH2O
“Static compliance describes pulmonary compliance when there is no airflow, like an inspiratory pause. This is defined as the change in lung volume by the change in pressure, in the absence of flow.” Physiopedia
What is dynamic compliance and how is it measured?
The elasticity of the airways. Vt / PIP-PEEP. usually between 45-50 cmH20
“Dynamic compliance describes the compliance measured during breathing, which involves a combination of lung compliance and airway resistance. This is defined as the change in lung volume by the change in pressure, in the presence of flow” physiopoedia
Disease processes involving dynamic compliance?
Asthma
Disease processes involving static compliance?
ARDS, pneumonia
How does an increase in compliance effect the patient?
It effects the work of breathing making it more difficult through the loss of elastic recoil
What parameters determine a prescribed Vt??
By IBW and lung compliance
General Vt?
6-10 ml/kg(IBW)
Lung protective Vt?
4-6 ml/kg(IBW)
Female IBW formula?
45.5kg plus 2.3kg for each inch over 5 feet