2550 - Hamilton G5

Ventilator function overview

- microprocessor controlled
- electronically controlled pneumatic ventilation system
- AC power + internal battery backup (extended battery backup optional)
- internal gas mixer for air-O2, option for heliox

What's the purpose of heliox as an adjunct therapy?

Mixture of helium + oxygen --> used in pts w high resistance
- He less dense than air --> so lighter --> higher R not as impactful (wouldn't prevent gas from reaching alveoli)
- dec tendency for flow to be turbulent w high R

Still setting flow RATE, but now flow PATTERN is dif (turbulent vs laminar)

Limitation to heliox/ when it's not beneficial

If FiO2 greater than 40% --> heliox ineffective

If FiO2 is higher --> less useful
- bc delivering more gas --> gas mixture heavier

What is special about the flow sensor?

1. Uses propriety proximal flow sensor @ pt wye
2. Flow sensor has variable bidirectional flow

Why is flow sensor proximal to pt?

Hoping that bc flow sensor is closer to pt --> it can sense changes in flow faster (vs if it was internal like 840 or 980)
- so potentially more synchronous w pt
- v sensitive to water + secretion build-up in circuit --> often get high priority alarm saying flow sensor needs to be changed

Ventilator tests (3)

1. Start up test
- occurs when ventilator power is on (~15sec)

2. Pre-operational test
- sensor calibration + tightness test

3. Oxygen cell calibration
- ensures delivery of desired FiO2

How does vent trigger? (3)

1. Pressure
2. Flow
3. Manual

If pt were to trigger, how would you know it was pt triggered vs time? (3)

1. Colour of waveform changes
2. Top L corner C if controlled, A if pt triggered
3. Any triangle under time axis means it was pt triggered

Dif colour triangles under time axis

Yellow triangle --> flow triggered
Pink triangle --> pressure triggered

^^signifies diaphragm

Pressure trigger

Vent is triggered when P drops below baseline sensitivity setting

Flow trigger --> what is bias flow?

Bias flow is 4LPM if sensitivity is equal or less than 2LPM

Bias flow becomes 2x sensitivity if greater than 2LPM

If sensitivity was 3, what would the bias flow through the system be?

6LPM

Patient set-up

- input gender + height
- IBW determined from these
- option of selecting last pt

What is S(CMV)

(Spontaneous) controlled mandatory ventilation
- under AC mode --> allowing pt to trigger
- VC

Set parameters on S(CMV)

VT, RR, flow, PEEP, FiO2

Flow waveforms on S(CMV)

1. Square
2. Decelerating
- option to set decelerating to 0 or to half
3. Sinusoidal (would never use)

How can you measure Pplat on (S)CMV?

Input an insp pause on every breath
- activate TIP button --> will tell you your Pplat every breath
*but don't do bc uncomfy for pt

Instead do manual insp pause under "tools" function

What is P-CMV

PC

Set parameters in P-CMV

PC (above PEEP) --> relative, not absolute
Ti is set by RR and %Ti
P-ramp

What is RCT

Resp cycle time, same as TCT

How is Ti set in P-CMV?

Ti is a % under PC (not setting absolute time for Ti)
- so dependent on RR and TCT (aka RCT)

If RCT = 5sec and Ti is set to 50%, Ti = ?

2.5sec

What is P-ramp?

Analogous to rise time
- measured in milliseconds (ms), not % or 1-9

What is SIMV? What is P-SIMV?

Combo of mandatory + spontaneous breaths
SIMV = VC breaths
P-SIMV = PC breaths

How does SIMV work?

Each SIMV interval includes Tmand + Tspont portions
- cycle time set by SIMV control
- mandatory breaths set similar to its corresponding control mode (VC vs PC)

What's different about SIMV in Hamilton compared to PB and LTV?

Nothing different besides what's set

??

What is APV?

Adaptive pressure ventilation
- volume guarantee w PC breath
- Hamilton's version of PC+

2 APV options (+ what they're similar to)

1. APVcmv
- like AC-VC+ on PB
2. APVsimv
- like SIMV-VC+ on PB
- Option for AC mode u want + spont mode u want (so it means you've set APV as AC mode u want)

What do you set for APV?

VTarget, RR, PEEP, high P limit

How does APV work?

Vent delivers 3 test breaths to determine pt's vol/ pressure response
- sees what vol is coming back --> adjusts P to deliver the set vol

What is the min P delivered by APV?

3cm/H2O --> but adjusted by +/- 2cmH2O to achieve set VT

APV limitations + how to mitigate

Same as VC+
- runaway P due to air leak
- air hungry pts --> vent dec P to dec vol --> pt has to work harder for more support --> pt-vent asynchrony

So make sure to set safe limits/ alarms

What are the spontaneous modalities of the Hamilton?

1. DuoPAP
2. APRV
3. Spont

What are DuoPAP + APRV (+ what are they similar to?)

Two related modes to support spontaneous breathing on 2 alternating levels of CPAP (combo of mandatory + spontaneous breaths)

DuoPAP = duo positive airway pressure
APRV = airway pressure release ventilation

^^same thing basically
Similar to bilevel

DuoPAP set variables

Phigh, PEEP, PS

APRV set variables

Phigh, Plow, PS

How is cycling defined on DuoPAP?

By P setting + time settings: Thigh + rate
- rate is like release breath --> responsible for CO2 clearance

How is cycling defined on APRV?

By P settings Phigh and Plow, and time settings Thigh and Tlow
(rate not set)
- not setting breaths directly --> they're a function of TH and TL

APRV: If TH is 5.5 and TL is 0.5, release breaths = ?

TCT = TH + TL = 5.5 + 0.5 = 6sec
Release breaths = 60/TCT = 60/6 = 10

What is PS in duoPAP/ APRV and when is it given?

PS is above PEEP (duo) or Plow (APRV)

Is PS given at Phigh? (DuoPAP/APRV)

Only if PS is less that target P

Why use APRV?

For pts w ARDS to spend more time at higher PEEP --> inc MAP --> recruit alveoli --> improve lung compliance + gas exchange

Pt can and should breathe spontaneously @ higher P

What is SPONT + what is it

PS (labelled SPONT on Hamilton)

Set PS + demand flow system

Set parameters on SPONT

PS set above PEEP (relative), P-ramp, ETS (expiratory trigger sensitivity), FiO2, sensitivity

What does "demand flow system" mean?

Flow is variable to meet pt demands

What is P-ramp? Units?

Similar to rise time % --> how fast P changes from PEEP to PS u set
- milliseconds

What's ETS?

Expiratory trigger sensitivity
- similar to Esens --> when it'll cycle to exp

If PS is set to 0, what is that?

CPAP
?

What should you always ensure to set on SPONT?

Apnea ventilation --> chooses the mode for when pt is in apnea

What apnea ventilation mode is available for PS (SPONT)?

P-CMV
(so basically PS defaults to PC?)

What apnea ventilation mode is available for SIMV?

(S) - CMV
- spont
(so basically SIMV defaults to VC?)

What apnea ventilation mode is available for APVsimv?

APVcmv
(so basically VC+ w SIMV defaults to VC+ AC)

How can apnea ventilation be reset if activated?

By pt triggering 2 consecutive breaths

What is TRC?

Tube resistance compensation (similar to TC in PB)
- designed to offset the flow resistance imposed by the ETT or tracheostomy tube
- active for use w spontaneously breathing pts

What do you set for TRC?

Artificial airway size + type, % compensation
- so if u set 100% compensation --> vent overcomes entire R of tube + pt just has to overcome their own airway resistance

How could a kink impact TRC?

Kink could cause inc R --> TRC (or TC) wouldn't compensate for that
- so any changes in R to tube (kink or buildup of secretions) --> machine won't compensate
- only knows R of tube w/o additional effects

What is NIV?

Non-invasive ventilation
- ventilator functions as demand flow system
- spontaneous breaths can be supported w PS level set (so like PS but giving breath non-invasively)

In NIV, is PS is set to 0, what does it function as?

CPAP

What's NIV-ST?

Mandatory breaths: PC, time-cycled
Spontaneous breaths: PS, flow-cycled
Automatic leak compensation

(similar to V60 STE?)

Why is NIV-ST like SIMV?

- set rate + mandatory-type breath, and pt can breathe spontaneously btwn those mandatory-type breaths
- mandatory breaths are PS-like --> cycle off to Ti
- the rest of the period is spontaneous --> PS but flow-cycled

Why do you set RR in NIV-ST?

Used as a semi-backup for pt so if they happen to go apneic --> can get some backup breaths

If under NIV-ST + BGA shows v high CO2 (hypercapnic), what could you do?

1. Could inc RR --> but this could be a band-aid soln for something that's a bigger problem --> pt clearly not tolerating NIV
2. So escalate care --> intubate --> so strict control of their CO2 clearance (e.g. w VC)

Does NIV-ST have leak sync?

No. But it automatically compensates for leak
- gives idea of how well mask is fitting pt face

How much leak can NIV-ST compensate for?

If P sensitivity --> can compensate for 1L/min
If flow sensitivity --> can compensate up to 30L/min

What's special about the Hamilton graphic display?

Shows lung C + R with a lung graphic
- low C --> rounder lungs
- high C --> more angular lungs
- low R --> airways less shaded (grey)
- high R --> darker airways (black)

Don't make therapeutic decisions based on this graphic.

PV curve 0AECD (everything shaded)

Total mechanical work of insp

PV curve straight line

Static compliance (C = vol/P)

PV curve 0ABCD (green/ everything above straight line)

Inspiratory WOB to overcome elastic resistance (potential energy available for PASSIVE exp)
- expand lung against natural elastance

PV curve AECB (blue/ bottom half of almond)

Insp WOB to overcome non-elastic resistance (e.g. airway resistance)

PV curve ABCF (pink/ top half of almond)

Energy required to overcome resistance to airflow DURING expansion
- energy to overcome R from exhalation (R exists on airway on way out too)

Why do you need less effort on exhalation?

If lungs not diseased --> passive exhalation
- as u inspire --> build up potential energy in lungs --> converted to kinetic energy when u exhale (so no extra effort needed)
- lungs, diaphragms, etc go back to resting state

How would PV curve look for a pt w COPD?

Would be way larger
- way larger P and V
- EPP occurs closer to alveoli --> pinching --> air-trapping --> inc RV --> so FRC in

What happens at the Lower Inflection Point (LIP) on the PV curve?

Marks shift from low to high C (slope inc)

What happens at the Upper Inflection Point (UIP) on the PV curve?

C shifts from high to low (slope dec)
- lungs nearing TLC --> already inflated --> dec C as elastance wants to take over bc lungs wanna recoil back to resting vol

Why is too low of a PEEP sub-optimal? (e.g. blue line in this pic)

Breathing back to this low P every breath --> constantly opening + closing alveoli bc putting pt back to low C @ end of every breath
- atelectrauma --> VILI

What is an optimal PEEP? (pink circle on pic)

@ P of LIP --> point of highest compliance (steepest slope on PV curve)
- keeps pt in higher C state --> don't have to re-recruit alveoli each breath
- wanna keep pt in high C part of curve

PV tool requirements (3)

1. Pt has to be intubated + paralyzed (can't make effort/ movement)
- can't do w NIV
- if they take breath @ high P --> can cause pt-induced lung injury

2. Minimum C = 5 mL/cmH2O
- pretty low

3. No gas leak
- bc using higher P so don't want any leaks to occur

Can you re-paralyze a pt to use PV tool?

Risky to re-paralyze pt bc paralytics have risks --> like they drive muscle atrophy
- could do it once or twice but risky
- also they need to be sedated (don't paralyze w/o sedation!!!)

What are PV tool indications? (3)

1. Determining optimal pt PEEP
2. Decreased C (ARDS)
3. Recruitment maneuver (RM)
- use this tool to create high P to recruit alveoli

What are PV tool contraindications? (5)

1. Spontaneous breathing
- don't want pt overriding

2. Unstable CV status
- if hyper-perfused --> don't wanna do this bc delivering high P --> offset CV elements (preload, afterload, etc.)

3. Inc ICP
- high P in lungs --> backflow of blood to R-heart --> SVC --> feeds back to head --> inc ICP

4. Leaks

5. Vulnerability to barotrauma + volutrauma (e.g. BP fistula)

How to access/use PV tool + what is set

Under "TOOLS" button
- info window pops up (read + acknowledge)
- set: Pstart, Ptop, EndPEEP, Ramp speed, Tpause (Tmaneuver is a function of Tpause)
- when ready --> hit "START/STOP Maneuver"

What's a good Ptop?

Ptop = max P
- good to put ~40

What's the optimal EndPEEP value?

P at LIP (16 in pic)

e.g. Pstart = 0, EndPEEP = 16

What is "40 for 40" on PV tool?

40 for 40 sec --> standard of time u want pts to undergo maneuver
- 27sec on this slide example --> to reach 40sec --> set Tpause to 13sec
- so P will reach 40 @ 27sec --> then hold 40 for 13sec --> til 40sec reached (27 + 13 = 40)

Builds up to 40 over 27sec, then holds for 13 sec (ex)

How do you find LIP/ optimal PEEP on PV tool?

DV graph shows what vol change was during maneuver --> highest C yields highest vol change --> so put cursor on highest point of graph --> correlates to LIP --> optimal PEEP

^^proof that LIP yielded highest C

If DV graph plateaus + largest P occurs for long time period, which time would you pick for your PEEP?

Set it @ lowest time point w that P
- every incremental P change doesn't yield higher vol --> don't wanna subject pt to more time @ P w/o more reward

14 in pic

What's ASV?

Adaptive Support Ventilation
- maintains min MV that's independent of pt's activity

Why is ASV useful?

To maintain optimal breathing pattern for pt that avoids deadspace ventilation, excess P
- optimal combo of RR + vol to be delivered to pt to target MV that doesn't cause harm

Ensure safe + ideal MV for pt

How does ASV work?

Shifts btwn passive + active mode depending on what pt is doing (w/o you changing anything)
- so it adapts
- utilizes OTIS eqn

Passive mode

APV
- vol-targeted, PC, time-cycled

Active mode (when is this activated?)

VS-like
- vol-targeted, PS, flow-cycled

When pt makes effort --> breathing spontaneously

What is set on ASV?

- set % MV
--> so it'll target MV by automatically adjusting RR, VT, and Ti based on lung mechanic changes + pt effort

Combo of active and passive?

Looks like SIMV --> grey zone --> so not just passive OR active

How does ASV deliver optimal MV?

Uses OTIS eqn to give pattern w lowest WOB
- vent chooses RR + VT according to R and C

ASV pt set-up

- input gender
- input pt height (cm)
- vent will determine pt's IBW based on ^^
- anatomical deadspace is automatically calculated from IBW determined by pt's height

What's set on ASV?

% MV, P-ramp, ETS, P ASV limit, P-trigger, PEEP/CPAP, FiO2

What does 100% MV mean?

100mL/kg/min = normal for adults
--> so 100% is 100, over 100% is more, under 100% is less

(based on healthy adult --> may need to compensate for disease pathology of pt)

How could HME impact MV? How to overcome?

HME can add deadspace --> add 10% to IBW to overcome + account for added deadspace

What's P-ramp?

How fast P rises from PEEP to max P
- in passive mode --> vol-targeted PC
- in active mode --> vol-targeted PS

What is ETS?

Expiratory trigger
- applies during active
- if pt under sedation + paralytics --> purely passive --> ETS won't take effect (no pt effort)