03 Ventilator

Ventilator
1. Mode
2. Setting

DOPE (displaced tube, obstructed tube, pneumothorax, equipment failure)

Mechanical Ventilation:
Modes:
1. AC (assist control): volume control
- Assist: patient triggers (vent assists)
- Control: apneic (vent controls)
- preset tidal volume or peak pressure is delivered
- if peak pressure is used, then it’s called IPPV (Intermittent Positive Pressure Ventilation) but initiation timing is the same
- you set RR and TV and that’s what the patient gets; if patient is unconscious, then the machine will give you this rate and volume; if patient decides to breathe, then they initiate the breath and the machine does all the work (patient is work-free)
- this is probably the only mode we use in ED which is for ALI or ventilatory problems – unless we tube for protection of airway where the lungs are fine, then you can use other modes
- least work of breathing although can overventilate (tachypnea)

2. SIMV (Spontaneous Intermittent Mandatory Mode)
- more work of breathing, ventilator delivers Vt/pressure dependent on patient’s effort and not fixed like AC
3. PS (Pressure support)
- needs spontaneous breathing, once triggered, vent gives pressure to help patient draw in Vt
4. SIMV with PS
- SIMV with extra boost of pressure support to get in more Vt (not dependent on patient’s effort)
5. CPAP
- spontaneously breathing; analogous with PEEP
- constantly on selected pressure
6. CPAP with PS
- BiPAP on a vent
- decreased work of breathing compared to CPAP alone
7. Controlled Mechanical Ventilation (CMV).
- ventilator provides a mechanical breath on a preset timing, Patient respiratory efforts are ignored
- uncomfortable

Oxylog 3000 Modes:
IPPV/IPPVAssist
- IPPV is for apneic patient, IPPVAssist synchronizes on partially breathing patients; IPPA Assist is automatically activated if Trigger is activated to have a value (small value = high sensitivity)
- Intermittent Positive Pressure Ventilation
- Controlled and assisted volume-constant ventilation with PEEP for CPPV
SIMV/ASB
- Synchronized Intermitted Mandatory Ventilation
- Assisted spontaneous breathing
- Procedure for weaning patients off the ventilator after they have started spontaneous breathing, with adjustable pressure assist during spontaneous breathing
CPAP/ASB
- Continuous positive airway pressure
- Spontaneous breathing with positive airway pressure and adjustable pressure assist
BIPAP/ASB
- Biphasic Positive Airway Pressure
- Pressure-controlled ventilation combined with free spontaneous breathing during the complete breathing cycle, and ajustable pressure assisted on CPAP level

4 Dials 70kg
VT 500
RR 18
Pmax: maximum airway pressure; peak pressure, this is the alarm limit 50mbar
FiO2 100%


Peak pressure
- topmost pressure after inspiration
- pressures on upper/major airways and ET tube
- does not mean anything

Plateau pressure (link)
- after peak pressure, tell the ventilator don’t allow the patient to exhale = inspiratory hold (0.5-1 second), don’t allow expiratory airflow = all the pressures along ventilatory circuit equalizes = what pressure the vent sees is the same as the pressure in the alveoli = plateau pressure
- pressure along lower airways/alveoli, maintained <30cmh2o cstat=" Vt/Pplat" cstat =" Static" vt =" tidal" pplat =" Peak" peep =" Positive" name="Title" content="">

2 Strategies (you ventilate 2 groups of patient) in ED
1. Lung injury or prone to it, or
2. Obstruction like asthma/COPD

Things to remember: use predicted body weight PBW
1. Mode
2. Numbers
(1) TV (Vt) = 6-8 cc/kg;protection

- should not be adjusted for ventilation (not to adjust pCO2)
- ALI/ARDS: 6 cc/kg
- adjusted only to prevent baro/volutrauma
(2) IFR: inspiratory flow rate 60-80 lpm comfort
- controls how quickly air goes in

- this can affect I:E ratio
(eg. for high Vt, I:E ratio should be 1:2, but in bronchoconstriction, it’s less than <1:2, rr =" ventilation
- on normal TV non-intubated: Va (alveolar ventilation) is 60cc/kg/min to maintain normal pCO2
- when tubed and ventilated, Va is doubled up to 120 cc/kg/min because of increased dead space (machine circuit and tube itself steals the volume away, so minute ventilation should be higher)
--
eg. 70kg patient, what is the minute ventilation?
70 x 120 = 8400 or 9000 cc/min
If you set Vt at 500 cc (which is 70kg x 7cc/kg)
how much should be your RR? = 18
therefore, normally ventilated 70kg should have
Vt = 500cc
RR = 18

- if RR is lower, say 10, minute volume decreaseds= hypercapnia since less pCO2 is released

*minute ventilation (respiratory minute volume) = TV x RR
*minute ventilation (V) = Va + dead space ventilation (Vd)
V
- volume of air that can be inhaled or exhaled per minute
- normal: 5-8L/min
- higher V higher pCO2 is released and vice versa

*adjust RR for ventilation where you want your pCO2, you can make RR to 30 or 40 unless it’s obstructive

Male: 50 + 0.91 (cm of height – 152.4)

Famale: 45.5 + 0.91 (cm of height – 152.4)

Males: 50 + 2.3 (height (in) – 60)

Females: 45.5 + 2.3 (height (in) – 60)
(4) FiO2/PEEP = oxygenation
- start 100% FiO2 and PEEP of 5, after 5 minutes get ABG
- down 40%
- adjust with PEEP scale
- target 88-95% saturation (make it 90%)

Lower PEEP/higher FiO2

FiO2 0.3 0.4 0.4 0.5 0.5 0.6 0.7 0.7

PEEP 5 5 8 8 10 10 10 12

FiO2 0.7 0.8 0.9 0.9 0.9 1.0

PEEP 14 14 14 16 18 18-24

--

Problems on Mechanical ventilation:
1. Too high Vt = overdistended = PTX
2. Shunt but PEEP is not increased:
*If saturation is <90% fio2 =" shunt"> shunt does not respond to more oxygen because the alveoli are collapsing (fills with fluid) -> more lung injury
*PEEP scale forces the alveoli from collapsing during expiration, alveoli stay more open and easier to oxygenate
*FiO2 more than 40% does not really help unless you bump up the PEEP

Plateau pressure:
- to make sure patient is safe in ventilator
- pressure applied on smaller airways and alveoli = can cause ventilator induced lung injury
- should be <30cmh20 style="">Peak pressure:
- pressure on major upper airways, ET tube = airway resistance
- does not mean anything

- in obstructive disease, this could be very high but it does not matter as it does not affect the alveoli

Opioid: Fentanyl or Morphine
1. Analgesia: tube is shoved in your throat
2. Blunts hypercapnia
Sedation:
- after opioid is given
- benzo or propofol (so you’re patient won’t remember these)

Obstructive Setting: Asthma/COPD

Goal is to give as much expiratory time as possible
Use large ET tube (8 Fr)

Mode-Assist Control

Vt-8 cc/kg by PBW

IFR-80-100 lpm (shortens inspiration, more time to exhale)

PEEP-0

FiO2-use whatever you need, most folks are fine at 40% (unless there is something else like pneumonia)

RR-Start at 10 bpm. Look for I:E of 1:4 or 1:5 Adjust the rate to achieve this.

Permissive Hypercapnia

Patients will need tons of sedation/opioids

Keep pH above 7.1; rarely, you may need a bicarb drip to accomplish this
Don’t adjust RR, don’t adjust Vt; get permissive hypercapnia instead of airtrapping, autoPEEP

FiO2
PEEP
RR

Oxylog 3000


Asthma
AC (Assist Control) volume

TV: 8mL/kg
higher IFR (inspiratory flow rate): 80L/min
FiO2: 40%
PEEP: 0
RR (most important): start at zero
*plateau pressure

Arrest Ventilated COPD/Asthma
1. Disconnect from ventilator
2. External compress x 1
- if no improvement
3. Bilateral needle thoracostomy, bedside U/S if you have time
- check the rest of DOPE
- Displaced = EtCO2
- Obstructed = sucker
- Equipment failure = bag
4. Fluids 2L (they are dehydrated)

PEEP (positive end expiratory pressure)
- especially in low Vt, at the end of expiration, the lower/distal airways/alveoli collapses, PEEP prevents it by acting like a ”stent”
AutoPEEP
- problem in AC, tachypneic or those with reduced expiratory airflow may not have enough time to exhale the large Vt = the air the remains in the alveoli at the end of expiration creates PEEP or auto PEEP = impair cardiac output or causes barotrauma
- decreasing Vt may help but will not completely cure it
IMV: Intermittent Mandatory Ventilation
- invented (1971) to counter problems with AC
- originally for neonates with RR of 40/min and has RDS
- combination of AC + spontaneous respiration
Permissive Hypercapnia:

- low Vt prevents VILI but low Vt accumulates CO2

Qualitative ETCO2:


- purple to yellow (litmus paper)


- pearls:


1. should be after 6 breaths (swallowed CO2 in the stomach)


2. not reliable in vomiting patient (litmus paper is affected)

3. not reliable in epinephrine via ET tube (again, litmus paper)


4. not reliable in cardiac arrest (could not measure low CO2), in this case quantitative ETCO2 is needed to see wave form