Ventilator Management

2 sets of patients:

1. ALI/ARDS and everything else

2. Obstructive (COPD/Asthma)

Mode

= when not sure use A/C

= you set the TV and RR

= patient initiates, and machine gives preset of Vt eg 500c

4 things you have to know about ALI (ARDSnet)

Vt = lung protection; 6-8 cc/kg IBW

Flow rate = patient comfort

RR = ventilation

FiO2/PEEP = Oxygenation

Vt = PROTECTION

- goal is to lower to 6cc/kg

- not adjusted according to ventilation (eg CO2 of 60, don't increase Vt or if low, don't lower Vt)

Inspiratory flow rate/IFR/peak flow = COMFORT

- how quickly a breath is delivered

- if high breath duration is quick

- 60-80 lpm

- if patient is sucking, not getting enough air = increase IFR

RR = VENTILATION

- 60 cc/kg/min to maintain eucapnia

- once intubated, requirement doubles due to deadspace of the circuit -> 120 cc/kg/min

70 x 120 = 8400

8400cc/500cc = 17

therefore start 16-18/min to prevent hypercapnia

- if hyperventilating, go down; if hypoventilating CO2 is low, RR to go up

* for acidotic patients, needs high minute ventilation

minimum 240 cc/kg/min, at least 36/min and adjust up

to prevent hypercapnia, to prevent acidosis

FiO2/PEEP =OXYGENATION

- if low O2, increase FiO2/PEEP tandem

- start 100% FiO2, wait x 5 minutes, get ABG

- drop to 40%, after 2 minutes wait for result

- use the PEEP scale for PEEP/FiO2, target 90-95% saturation (not more than >95%, at saturation of 100%, you won't know if the PaO2 is 80% or 400% which is too much), adjust every 10 minutes

- PEEP does not pop lungs!

PEEP

- good: Improves V/Q, decreases shunt, decreases atelectasis/trauma, improves spont breathing

- bad: decreases venous return (you can work it out, give more fluid)

- myth: causes pneumothorax, head explodes

*alveoli is like balloon: easier to blow if there's some air already in there

How to avoid pneumothorax

- check plateau pressure (or alveolar pressure), should be <30cmH20

- check every 30 minutes, if >30, adjust PROTECTION which is Vt (if too high drop Vt from 8 to 7)

- peak pressure means nothing

Ventilation curve pattern/ventilation pressure wave form on VC mode

- air rushes to ET tube, tracheobronchial tree = high initial pressure = Peak pressure

- after system has equilibrated with alveolar, it plateaus = Plateau pressure

Peak pressure: PIP/Peak Inspiratory pressure

- means nothing to patient's safety

- does not affect the alveoli

- only purpose is to alarm the vent

Plateau pressure:

- this reflects small airway and alveolar pressure

- not measured by vent directly (after delivering the oxygen, vent drops very quickly)

- should be less than 30cmH20

- press inspiratory hold button (0.5-1 second) once patient breathes = plateau pressure

*Peak pressure: pressure on major airways (+ ET tube) = alarm

Plateau pressure: pressure on smaller airways (+ alveoli) = matters

PIP: peak airway pressure

Pplat: Plateau pressure

Paw: airway pressure

SUMMARY:

Vt: if plateau pressure >30, decrease Vt

IFR/Peak flow: if patient is sucking, not getting enough air = increase IFR

RR = ventilation, if CO2 too high, increase RR

FiO2/PEEP: increase this if <90% saturation with target 90-95%

analgesia:

- fentanyl or morphine

- comfort for pain, blunts effects of hypercapnia

then sedation:

- propofol, ativan, versed

OBSTRUCTION (asthma, COPD)

- goal: give patients time to expire

- mode: AC

Vt: 8cc/kg IBW

IFR/peak flow: make inspiration shorter therefore higher to expire slower: 80-100 lpm

FiO2: 40-100%, usually no Oxygenation problem, leave at 40% if you want (they desaturate because they tire out)

PEEP: zero

RR: - most important setting, set this low

- start at 10

IE ratio: 1:4 or 1:5

Permissive Hypercapnia

- CO2 of >50, as long as pH is 7.2, 7.1 (because of hypercapnia) that's fine

- bicarb has no pathophysiologic reason

AVOID air-trapping and autoPEEP

- air trapping: alveoli are closed off cuz of mucous plugging and air could not go out, needs suctioning/pulmonary toilet

- auto PEEP: dynamic overinflation of alveoli, goes away if they are allowed to breathe

Airtrapping: normally there is a space between fully expiring gas and the next inspiration

in obstructive disease, the air is not fully exhaled and inspiration comes in immediately, stacking air/gas

- if this happens, lower RR

AutoPEEP

- if vent doesnt have this, look at plateau pressure

*peak pressure

- does not mean anything

- represents ET tube, large airways

- constricted on obstructive disease, therefore this is high like 80-90, therefore this always alarms, just increase upper treshold of alarm, cuz this does not mean anything

* plateau pressure: if >30, significant auto PEEP, decrease RR

if <30, autoPEEP is not significant

Scenario

- Asthmatic, crashing on the vent (low sat low BP)

DISCONNECT the vent, leave the ET tube

- if air rushes, the air-stacked will go out

- if no air rush, no improvement of vital signs = use DOPE

Sedated completely (you intubated this patients due to muscle fatigue, so dont let them breathe)

- propofol: has bronchodilatory effect too

analgesia: fentanyl/morphine; blunts hypercapnia, for comfort

SUMMARY:

Vt: 8cc/kg

IFR: 80lpm

FiO2: just maintain sats >90

RR: 10

- if airtrapping on curve, decrease down to 8 to 6

- if >30 plateau pressure; down RR

-----

pdf Vent Handout from Dr Scott Weingart

Crashing post intubation

D - isplacement

O - osbstruction

P - PTX

E - Equipment failure

S - in asthma, stacked breaths

Stacked breaths - disconnect the vent circuit

- if air gushes out, patient improves

- if no improvement, no air gushing = proceed to DOPS

Equipment failure - attached BVM (eg kinked tube, machine failure, no O2 in vent etc)

D - tube Displacement: check ETCO2 colorimetric or wave form

O - obstruction: suction, if too thick plug, can push with bougie, but the plug will go deeper

P - tension PTX, check with US if with time, otherwise....

Perform bilateral finger thoracostomies!!!

Level of ET tube: from teeth, Caucasian 23 M, 21 F; Asian 22 M, 20 F