Áp lực đẩy: Khái niệm, Sinh lý học, Giá trị và giới hạn, Điều chỉnh trong bệnh nhân ARDS

VILI Pressure Resp Rate Volume Flow Lung Edema Edema Location... Pressure.[r]

Driving Pressure

Definition, Physiology, Value and Limitations

JOSHUA SOLOMON, MD ASSOCIATE PROFESSOR OF MEDICINE

NATIONAL JEWISH HEALTH

DENVER, CO

• Background

• What is Driving Pressure?

• Value of Driving Pressure

• How do we use it in clinical practice

• Limitations

“Functional Lung”

“Functional Lung”

Lungs aren’t STIFF – they are SMALL!

Safety Zone

Tonetti et al Annals of Trans Med 2017; 5: 286

VILI – Ventilator Induced Lung Injury

Tonetti et al Annals of Trans Med 2017; 5: 286

Pressure

Resp Rate

Volume

Flow

Lung Edema

Edema

Location

Resp Rate Volume

Flow

Gattinoni et al Int Care Med 2016; 42: 1567-1575

Transpulmonary Pressure (P TP )

different due to the extra work to recruit and

inflate alveoli

Lung Compliance

ARDS Net Trial

◦ Low tidal volume

NEJM 357:1113, 2007

Where is the most benefit?

• Low VT

• Low plateau pressures

• High PEEP

Driving Pressure

• DP normalizes the tidal volume to the

compliance of the respiratory system

△P = Vt / CRS

△P = Plateau – PEEP Plateau – PEEP = Vt / CRS

• Both have same Vt

How to determine Driving Pressure

J Pediatr 2007; 83(2 Suppl): s100-8

How to determine Driving Pressure

Limitations to Driving Pressure

• Its value is dependent on compliance

◦ Low compliance will result in low VT

◦ Hard to develop a universal DP

• Doesn’t accurately reflect transpulmonary

pressure

◦ Need to take into account chest wall pressure

Amato et al NEJM 2016; 372: 747-755x

• Hypothesis that △P would be more predictive of survival than PEEP and tidal volume

• Looked at data on 3562 patients in 9 prior ARDS

trials

• Used rare and complicated statistical method

(multilevel mediation) to determine isolated

effect of △P on survival

Amato et al NEJM 2016; 372: 747-755

VARIABLES IN MODEL

Treatment group (lung protective, control)

Patient Characteristics Severity of disease (APACHE, SAPS, Pao2:Fio2) Ventilator variables (VT, plateau pressure, PEEP, △P)

Amato et al NEJM 2016; 372: 747-755

• One standard deviation increase in △P (7cm

H2O) increases mortality by 40% (p < 0.001)

◦ This holds true for patients on “protective” plateau and

VT (mortality increase 36%, p < 0.001)

• Changes in VT or PEEP didn’t improve mortality

unless they were associated with changes in △P

Amato et al NEJM 2016; 372: 747-755

◦ Patients CAN’T be breathing

◦ Can’t extrapolate to Pplat>40, PEEP <5, RR > 35

◦ Didn’t measure transpulmonary pressure

◦ Retrospective – hypothesis generating

Driving Pressure and

Transpulmonary Pressure

In a patient with decreased chest wall compliance (e.g obesity, ascites), this large △P wouldn’t lead to a large

PTP.

• Looked at 7 studies (5 secondary analyses and 2

observational) with 6062 patients

• Association between higher △P and mortality

• Suggest a target pressure of 13 to 15 cmH2O

Aoyama et al CCM 2018; 46: 300-306

How to use it today

• Not ready to start adjusting ventilators to a target △P

• Continue with VT and Pplat

What we need

• Prospective randomized trial looking at:

◦ Variables : △P, Pplat, Vt and transpulmonary pressure, PEEP

◦ Target : Ventilator days, mortality, VILI, biomarkers of inflammation (ICAM-1, IL-6, IL-8 etc)

• We should still use VT of 6cc/kg and Pplat as

targets in ARDS ventilation

• Prospective studies are needed