Monitoring of Mechanical Ventilation

Pr Jean-Christophe M Richard

Pôle SAMU 74 Urgence et Réanimation Centre Hospitalier Annecy Genevois

CONFLICTS OF

INTEREST

- Air Liquide Medical Systems (part time)

Financial support for research (Genève /Annecy/Angers)

-VYGON (personal fee for lectures)

-SHILLER

-MAQUET (NAVA)

-COVIDIEN (PAV+) (personal fee for lectures)

-DRAGER (SmartCare)

-GE (FRC)

Monitoring of ventilation based on flow

and Paw time curves

Volume assist control

Equation of motion of the respiratory systemduring controlled ventilation

Paw = (flow . R) + (Volume . E) + P0

patient

Pressure-targeted Flow-targeted

P

V

t

target P

V

t

target

Monitoring of MV based on flow and

airway pressure curves

valve

Ventilator

Pressure

Flow60 l/min

Pressure mesured

Volume Control (flow regulated)

Tins

Oc

end-exp

Alv. Pressure

end-insp

Alv. Pressure

Pres

Pel

• R= Pres / Flow

• R= [Ppeak – Pplat] / Flow cmH20.L-1.s

• C= Vol / Pel

• C= Vol / [Pplat – PEEPtot] mL. cmH20-1

• C= Vol / [Driving Pressure]

Driving pressure = Pplat - PEEPtot

Amato et al. NEJM 2015

How to set inspiratory flow ?

Inspiratory flow

• R= Pres / Flow

• R= [Ppeak – Pplat] / Flow cmH20.L-1.s

• R= [Ppeak – Pplat] / 1 L/sec

60L/min (1L/sec)

Volume Controlled

Rrs = 5 Rrs = 10 Rrs = 25

Ppeak

Pressure

Flow

Volume

Pressure

Flow

Volume

Crs = 50 Crs = 30 Crs = 20

Volume Controlled

Ppeak

Ventilator

Pressure

setting

Airway pressure

0

20

20

Pressure regulated mode

1010

155

20

20 cmH2O

Pressure Controlled

Pressure

Flow

Volume

Rrs = 5 Rrs = 10 Rrs = 25

Vol min

Crs = 50 Crs = 30 Crs = 20

Pressure Controlled

Pressure

Flow

Volume

Vol min

Monitoring of Vt during Pressure Controlled

R

C

V= V0 e-t/t

t = R x C

V

t

V0

3t = 96% V0

Dynamic hyperinflation and intrinsic PEEP

Intrinsic PEEP: 3 causes

• Dynamic hyperinflation

• Flow limitation

• Expiratory muscle recruitment

Paw

cm H20

Flow

L/s

Volume

L

20

40

0

Exp Pause Insp Pause

ΔPEEP = 102. Reduce PEEP

3. Record expired Vt

4. Record Pplat

1. Reduce RR

Chen L e al. Crit Care 2017

Evaluation of Alveolar Derecruitment

ΔPEEP = 102. Reduce PEEP

3. Record expired Vt

4. Record Pplat

1. Reduce RR

ΔEELV = [PEEP 1 – PEEP 2 ] x C

Vrec = ΔEELV – Vt exp

Vrec = 300ml – 450ml = 150 ml

Compliance = 30 ml/cmH2O

Conclusions

During volume targeted mode of ventilation Paw (Ppeak & Plat) permit

to simply monitor occurrence of clinical events

During pressure targeted mode flow & volume carry similar information

but much more tricky to monitor

Routine use of end expiratory and end inspiratory occlusion is possible

in both volume control and pressure control

Occlusion pressure permit to reliably assess pressure inside the

respiratory system wich is of high clinical value.