Mech Vent and Anesthesia Flashcards
Pleural pressure surrogate
Esophageal pressure
- target Pes < 25cm/H2O
- Calculate by subtracting Pes from inspiratory hold on LTV
Ways to improve oxygenation:
- Increase FiO2
- Increase PEEP
- Paralyze patient
- Pressure control (square waveform)
- Lengthen I-time (inverse ratio)
- Recruitment maneuver
- Prone positioning
- Don’t forget to consider a fluid bolus to improve West Zone physiology
Low Pressure Alarm
Not enough Pip was created to hit the low pressure limit (usually set 5cm/H2O above PEEP). Check for…
- Leak in the circuit/disconnect
- ETT cuff deflation
- ETT displacement
High Pressure Alarm
Could mean increased resistance or worsened compliance. Check for…
- ETT secretions/foreign body
- Patient biting on tube
- Bronchospasm/constriction
- Patient airway mal-alignment
- Decreased lung compliance (edema, fibrosis, pneumonia)
- Decreased thoracic compliance (burns, MSK trauma)
- Kinked circuit
- Patient dysynchrony
LTV weight ranges
- Neonates: 5-10kg
- Pediatric: 10-40kg
- Adult: 40kg +
Describe Lung Compliance…
- Change in pressure divided by change in volume
- If a lot of pressure is required for not a big change in volume, you have a non-compliant lung.
- Can relate to inner (lung) and outer (MSK, integuementry, abdomen)
Describe the resistance/compliance relationship…
Resistance is the force that needs to be overcome to get air into the alveoli. Once air gets into the alveoli, compliance is the force that needs to be overcome to inflate them.
What factors adjust the I:E ratio?
Resp rate
I-time
What is the ideal vCalc and what factors influence it?
50-60lpm
I-time and tidal volume
What contributes to autoPEEP?
- Increased RR (not enough time to exhale)
- Minute volumes are too high
- Bronchospasm
- ETT too small
- Mucus plug in ETT
What are the three breath types?
- Machine (control)
- Assisted (pressure support, BPAP, ACV, SIMV)
- Patient (SIMV, CPAP)
Ventilator dyssynchrony is associated with badness. What is it and how do you go about addressing it?
Dyssynchrony is associated with ALI, respiratory fatigue (increased VO2) and a longer duration of mechanical ventilation. Increasing sedation to make the patient more compliant will also possibly lead to ICU delirium. Look for what the patient needs and give it to them. That being said, if you have too much other shit going on, paralyze the patient and get things under control before you go about fine tuning the vent.
Discuss Pip
- Highest pressure measured during the respiratory cycle
- Is a function of both resistance and compliance of the respiratory system
Discuss Pplat…
- Measured during a no-flow state at the end of inspiration
- Reflects static compliance of the respiratory system including the lung parenchyma, chest wall and abdomen
What does an increased Pip with a wide delta P (Pip- Pplat) indicate?
- Increased airway resistance
- Check for secretions/mucus plug, kinked circuit, bronchospasm, biting, tube position
What does an increased Pip and increased Pplat with a normal or narrow delta P signify?
- Suggest a worsening respiratory system compliance
- Check for right main stem, pneumothorax, atelectasis, pneumonia, ACS, edema, DOPES…
What is bias flow?
Flow within the circuit (usually 10lpm) that senses a patient breath (usually at 2lpm) and triggers the ventilator.
Common complications of mechanical ventilation…
- Diminished cardiac output (IVC compression)
- Increased right sided afterload (pulmonary vasculature compression)
- Pulmonary barotrauma/volutrauma (pneumothorax)
- VALI/ARDS
- AutoPEEP
- Elevated ICP
- VAP
- Pressure ulcerations
Considerations for venting a TBI
- There will be reduced ICP drainage
- Don’t let the patient become hypercapnic (target paCO2 to 35-40mm/Hg)
Ways to reduce VAP
- HOB at 30 degrees
- Swap out HME filters
- Ensure proper ETT cuff inflation
Ventilation strategies for obstructive pulmonary disease…
- vCalc of 80-100lpm
- I:E of at least 1:3
- 10 to 14 frequency (monitor EtCO2 waveform)
- Keep tidal volumes below 8mL/kg
- Allow permissive hypercapnia; target pH instead
- Keep Pplat <30cm/H20
- Monitor autoPEEP carefully
- Suction, larger ETT, bronchodilators, take off vent, reduce demand)
Target PaCO2 for elevated ICP? For herniation?
Increased ICP: 35 to 40mm/Hg
Herniation: 30 to 35mm/Hg
Effects of ACS on lungs
- Compresses lung parenchyma, reduces surface area
- Increases intrapulmonary shunt fraction
- Increases alveolar deadspace
- Will require higher Pips, MAP and Pplat (consider permissive hypercapnia)
DOPES for acute MV decompensation:
- Displaced ETT
- Obstructed ETT
- Pneumothorax
- Equipment failure
- Stacked breaths
Correct autoPEEP
- Change vent settings (increase vCalc, decrease rate, decrease TV)
- Reduce ventilator demand (treat fever, pain, anxiety)
- Reduce airway resistance (suction ETT, bronchodilators, larger ETT)
- Take circuit off of patient and let them fully exhale over an uncomfortably long period of time.
Effects of PPV on hemodynamics
- Increased intrathoracic pressure decreases preload.
- Alveolar over-inflation compresses pulmonary vascular bed, increasing PVR and reducing RV output.
- Increased PVR causes intraventricular septal shift which impairs diastolic filling and reduces CO of LV.
- Reduced afterload due to improved pressure difference in LaPlace’s law. Decreased wall tension = decreased MVO2.
Effects of PPV on neurological system…
- Can cause hyperemia/increased ICP by inhibiting cerebral drainage
- pH affects vascularity and cerebral blood flow.
- Changes in cerebral pH could affect respiratory center in brainstem.
Effects of PPV on respiratory system…
- Trauma (barotrauma, volutrauma, biotrauma, sheer trauma)
- Over-inflation of alveoli will compress blood vessels and cause VQ mismatch/shunt
Effects of PPV of GI/GU…
- GI bleeding from stress ulcerations
- Impaired renal blood flow and possible AKI due to decreased CO (pre-renal failure)
- Gut ischemia causes translocation of bacteria
- Liver dysfunction (decreased oncotic pressure, decreased coagulation)
Effects of PPV on immune system…
- Induces pulmonary inflammation
- Translocation of tracheal bacteria into bloodstream
Equation of Motion
P(mus) + P(vent) = V/C + (Raw x flow)
Setting alarm parameters on LTV 1200
High Pressure: 10cm/H2O above set Pip
Low Pressure: 5cm/H2O above PEEP
Low Minute Volume: 10% below minute volume.
Low minute volume alarm
- Breathstacking
- Cuff leak
- Leak in circuit/disconnect
- Decreased lung compliance in PC mode
Turn on CPAP mode
Toggle CPAP/SIMV
Dial breath rate to –
Dial in PEEP from 0-20cm/H2O and pressure support to –
Describe the apnea back up ventilation mode (pressure support, CPAP)
- After 20 seconds of apnea, the ventilator will start ventilating at the preset breath rate, or at least 12 breaths if nothing programmed.
- Mode shuts off after 2 consecutive patient breaths or when alarm silenced.
How long does an alarm stay silenced for after hitting silence once?
60 seconds. It needs to be tapped twice to shut it off.
List the three ways a ventilator breath is cycled (switches from inspiration to expiration).
Time
Pressure
Volume
Minimum I-time on LTV 1200
300ms
You have an LTV 1200 with pressure control of 20cm/H2O and a PEEP of 10cm/H2O. What’s your Pip and delta P?
Pip: 30cm/H2O
Delta P: 20cm/H2O
Battery phases of LTV 1200
“Bat Low” light is amber. You have 10 minutes until the light turns red, alarm constantly sounds “Bat Empty” and then you only have approximately 5 minutes until the ventilator turns off.
Consider even less time if settings are high or patient dysynchrony.
What’s the difference between CPAP and NIPPV?
CPAP is for intubated patients breathing on their own. NIPPV is for masks and accounts for greater degree of air leakage.
Low PEEP alarm
Patient continues to breathe in after the ventilator cycles into exhale mode, thereby creating a negative pressure in the circuit and reducing the PEEP.
-Check ventilator settings and consider increasing tidal volume/pressure.
What does holding the FiO2 button down for 3 seconds do?
Provides 100% oxygen for 60 seconds
The LTV can handle oxygen pressures of 35-85 psi. If you need to deliver oxygen at a lower pressure, what must you change on the machine?
“Low Oxygen Pressure”
*Use a tubing nipple and screw it onto the high pressure valve.
What does a sustained “HIGH PRES” alarm indicate?
High pressures have been hit 4 x the set I-time. LTV will dump turbine and you need to BVM patient.
What three buttons are still active in control lock mode?
- Select
- Silence
- Manual breath
High PEEP alarm
Patient is forcing out more on exhalation.
Default setting in extended features is +5cm/H2O
-breath stacking
-kinked circuit
-adjusted PEEP valve on circuit
-kinked exhalation port
Is the LTV 1200 and open or closed loop circuit?
Open loop.
Even though it will dump a breath in the setting of a high pressure alarm, it doesn’t take fine inputs from the patient and modify its outputs.
Dr. Vu’s goals of mechanical ventilation:
There’s nothing good about putting someone on a ventilator
- Oxygenate adequately
- Ventilate appropriately
- Optimize pH
True or False: Decreasing respiration rate will blow off more CO2 in an air trapping patient?
True and False. It depends on their level of autoPEEP.
Compare Pra and right sided heart functions in PPV vs spontaneous breathing patients:
-PPV increases right atrial pressure (Pra) which decreases flow to RA which decreases RV preload and CO. It’s the opposite in spontaneous breathing patients.
Nine measurements you should always monitor to help confirm you’ve picked the right ventilation strategy.
- Tv
- RR
- I:E
- MAP
- Pip
- PEEP
- Flow
- VE
- EtCO2
How does increasing the PEEP actually reduce the Pplat in some patients?
Recruitment maneuvers and increasing PEEP can recruit atelectic lung tissue and improve lung compliance. This will decrease intrathoracic pressures and lower Pplats.
What gives you more time under the curve: Volume or pressure mode?
Pressure mode has a square waveform which allows for better oxygenation. It also dissipates pressure evenly throughout the alveoli
You’ve successfully recruited lung tissue in an ARDS patient. Now you need to suction their airway. What must you be aware of?
Suctioning will potentially collapse their PEEP so you may need to do a lung recruitment maneuver after the suction.
5 prerequisites for NIPPV
- Conscious and spontaneously breathing
- Protecting their airway
- Managing their secretions
- Appropriate seal
- Physiology to support it
- Can they handle it for the duration of flight and be in a comfortable position?
What is the P:F ratio?
Divide the patient's PaO2 by the FiO2 they are receiving. Normal: 400-500 Mild: <300 Moderate: <200 Severe: <100
Primary goal of any good ICU according to Vu.
End organ oxygen delivery
Management of laryngospasm:
- Tight fitting mask with high flow O2
- Gentle BVM with high PEEP
- Suction any noxious substances from oropharynx
- Paralyze if necessary
Broadly speaking, there are two body systems that can be responsible for respiratory insufficiency:
CNS
Pulmonary System
The LTV 1200 has a max minute volume. What happens if you suspect the patient has a higher MV than the machine can handle such as a DKA patient?
Avoid paralyzingly patient and see if pressure support will work.
List 4 causes of hypotension following induction:
- SNS ablation from sedatives
- PPV compression of vasculature
- Myocardial depressant and vasodilatory action of drugs
- Patient could be catecholamine deplete
Kinda left field approach to inducing a TBI or aortic stenosis patient…
1% Xylocaine @ 1mg/kg
What’s your induction plan for sick cardiac patients:
Low dose ketamine (30mg) with high dose fentanyl (+1.5mcg/kg). Then use ketamine/midazolam for maintenance.
*Remember that time of onset of induction agents will be delayed if cardiac output is reduced.
When topicalizing an airway, what three areas do you want to target?
- Base of tongue
- Tonsilar pillars
- Valecullar folds
Infusion of choice for the crashing patient…
Give ‘em the Epi!
Two leading causes of cardiac arrest during peri-intubation
Hypoxia
Hypotension
Describe your approach to intubating a critically ill patient (no pulmonary hypertension)
- NODESAT
- Get an arterial line
- Start Levophed
- Give 1L of crystaloid
- Provide an increased PEEP if BVMing, or BiPAP
- Consider NaHCO3- if K+ is already elevated
How do you calculate if you have recruitable lung tissue using an esophageal balloon?
Calculate your transpulmoanry PEEP (TPPEEP). The value should be 0-10. Anything less than 0 is sheer trauma. Anything greater than 10 is baro/volutrauma.
TPPEEP = LTV set PEEP - (Esophageal PEEP on exp. hold x 1.3)
Two causes for a large delta CO2:
- PE
2. Cardiogenic shock
Calculate safe plateau pressures using an esophageal balloon:
TPP = LTV Inspiratory hold - (Esophageal balloon pressure on inspiratory hold x 1.3)
Safe plateau pressures with esophageal balloon = <25
*Pt must be paralyzed and on volume control.
How is it possible that increasing PEEP leads to a worsening of PaO2?
If you add too much PEEP, you can turn WZ II, III physiology into WZ I due to overinflated alveoli and vasculature compression.
Drop an esophageal balloon and titrate PEEP accordingly. You can also try a fluid bolus if supine positioning improves SpO2.
How do you calculate the PAO2?
PAO2 = FiO2 (PB - H2O) - (PaCO2/r) PB = Barometric pressure (usually 760) H2O = Water vapour (47) r = Coefficient (.8)
PAO2 = .21(760-47) - (40/0.8) PAO2 = 100
How do you perform a recruitment maneuver?
- Paralyze
- Switch to pressure control
- Prolong I time
- Increase PEEP + PiP to 40 for three breaths
- Clamp tube on end-inspiration and hold for 40 seconds
- Dial in new vent settings with increased PEEP.
- Monitor VTe for improvement.
Calculate PPlat
VTE/Static Compliance = Driving Pressure
Driving Pressure + Total PEEP = PPLAT (+/- 2)
How does static compliance relate to tidal volume?
If static compliance is 23, then you will get 23mL of air per 1 cm/H2O of Pip (under normal lung compliance)
