interest of the esophageal pressure measurement

Interest of the Esophageal

Pressure Measurement

Antonio Pesenti

University of Milan

Italy

antonio.pesenti@unimi.it

Brux ref 2018

DEFINITIONS

• Compliance : change in volume that

generates a unit change in pressure

• Cpl = DV/DP

• Elastance = Change in Pressure to obtain

a unit change in volume

• E = DP/DV

• Cpl = 1/ E

DEFINITIONS

• Compliances in parallel add up

• Elastances in series add up

Cpl = 0.05 l/cm H20

El = 20cmH20/l

Cpl = 0.1 l/cm H20El = 10cmH20/l

Cpl = 0.025 l/cm H20

El = 40cmH20/l

Lung and Chest Elastances

StiffStiff

EtP

1515 1515

EwPwELPL

“Soft”“Soft”“Soft”“Soft”

StiffStiff

EtP

2525 55

EwPwELPL

cmH2O

rs rs

P es is determined solely by DV and Ccw

cwC

VP

DD

+500

DPpl

CL =100

Ccw =100

CL =50

CL =10

5

5

5

Esophageal Balloon

• Low- pressure balloon

• 9 – 10 cm long.

• Optimal fill vol. is 0.5

– 1.0 ml of air.

• Position the bottom of

balloon 40 cm from

incisor.

Courtesy of D.Talmor

Pressures acting on P eso

• 1) Elastance of the rib cage (Erc)

• 2) Weight or load of the rib cage (PWrc)

• 3) Elastance of the lung (El)

• 4) Elastance of the diaphragm and, if any, of the abdomen

(Edi)

• 5) Weight or load of the abdomen (PWab)

• 6) Elastance of the esophageal wall (Ees)

• 7) Weight or load of the mediastinal organs (PWmed)

• 8) Elastance of the esophageal balloon, if over-inflated (not

indicated in figure).

From Hedenstierna Minerva Anest 2012

Why esophageal pressure?Esophageal balloon is inflated to directly transmit the pressure within the esophagus, which is a collapsible virtual cavitybetween the lungs and the chest wall.

Pes value should reflect pleural pressure (Ppl) at that level.

Dependent lung

Non dependent lung

Negative values = collapse

Pelosi et al Am J Respir Crit Care Med. 2001;164:122

What is Transpulmonary Pressure?

• Is the Pressure needed to inflate the lung up

to the given volume

• Is the result of the elastic forces that the

lung spends to oppose its change in volume

• Is the pressure that makes the lung explode

• Is the cause of VILI ( Delta Plung?)

Plung = Prs-Pcw

DPlung = DPrs-DPcw

Intrathoracic Pressures and Lung Stretching.

Slutsky AS, Ranieri VM. N Engl J Med 2013;369:2126-2136

Intrathoracic Pressures and Lung Stretching.

Slutsky AS, Ranieri VM. N Engl J Med 2013;369:2126-2136

Plung = Prs-Pcw

DPlung = DPrs-DPcw

DPlung= ( Elung * Dvlung)

If DV lung = 0 then DPlung = 0

Am J Respir Crit Care Med 189, 520–531, 2014

HOW TO ASSESS CHEST WALL CONTRIBUTION?

QUANTITATIVE APPROACH 1

Measured Pes is a reliable estimate of absolute pleural pressure.

Talmor D et al, NEJM 2008

Talmor D et al, NEJM 2008

Positive esophageal pressures at

FRC

• Could pleural pressures be positive?

• Could transpulmonary pressures be

negative?

Some Common (Un)Definitions

• Ppl is not always negative during normal

breathing!

• Transpulmonary Pressure:

Paw-Ppl vs Palv- Ppl

• Pl= Paw (El/Ers) vs DPl= Dpaw(El/Ers)

Gattinoni L, et al. Eur Respir J Suppl 2003; 47:15s-25s.

+ PL at Paw(0)

Crit Care Med 2013, 41, e9

AJRCCM 2016 :194:1452

Positive esophageal pressures at

FRC

• Could pleural pressures be positive? Yes

• Could transpulmonary pressures be

negative? Yes

• Use elastance-based estimates to avoid

negative transpulmonary pressures? Nyes

Same Elastance Different Volumes

P

V0 1 2 3

1

2

3

4

Sharp JT JAP 1964

Sharp JT JAP 1964

ECMO

Grasso S ICM 2012

NO ECMOGrasso S ICM 2012

…

Pontoppidan NEJM 1972: 287: 690

Chest Wall Elastance

• Chest wall is not only chest wall

• Diaphragm and abdomen are part of the chestwall

• Passive breathing «moves» a huge mass ( abdominal organs, abdominal wall)

• Should we consider Chest Wall elastance maydiffer between static and dynamic conditions?

Transpulmonary Pressure

• May be useful in all ARDS patients

• Recommended in

– High IAP

– Obese Pts

– Secondary ARDS

• Investigational

– Early Spontaneous Breath Application

– Work of Breathing

Work of Breathing - Controlled

Paw

Pes

Volume

CPAP PSV

Flow

(L/sec)

Paw

(cmH2O)

EAdi

(microV)

Pes

(cmH2O)

THANK YOU!