interest of the esophageal pressure measurement
TRANSCRIPT
Interest of the Esophageal
Pressure Measurement
Antonio Pesenti
University of Milan
Italy
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!