Recognition that mechanical ventilation, although life-saving ... - SRLF

« Recognition that mechanical ventilation,
although life-saving, can contribute to patient
morbidity and mortality has been the most
important advance in the management of
patients with ALI and ARDS »

Mechanical ventilators, by applying high
transpulmonary pressure to the nonuniformly
expanded lungs of some patients who would
otherwise die of respiratory insufficiency, may
cause the hemorrhage and hyaline membranes
found in such patients’ lungs at death.
Mead, JAP 1970

Webb and Tierney, ARRD 1974

« Before we began this project, we were an
unlikely team »

Mechanism of edema
• Hydrostatic : increased filtration through
– extra-alveolar vessels (pulmonary
interdependence)
– alveolar vessels: surfactant inactivation
• Only?

Parker, JAP 1984
6

Egan
J. Physiol 1976

Dreyfuss and Saumon AJRCCM 1998

Dreyfuss et al, ARRD, 1985

Dreyfuss et Saumon, AJRCCM 1998
10

Dreyfuss et Saumon, AJRCCM 1998
11

Dreyfuss et al., ARRD 1985

Respective roles of pressure and volume
Dreyfuss et al, Am Rev Respir Dis, 1988
13

Effect of Peep
Dreyfuss et al, Am Rev Respir Dis, 1988
14

zeep
Peep may reduce
VILI
Dreyfuss et al.
ARRD 1988
10 cmH2O
peep
15

Effect of peep set above the LIP
Argiras
1987
Sandhar
1988
Muscedere
1994
Sohma
1992
Type of injury
saline lavage
saline lavage
saline lavage
HCl instillation
Effect of high
Peep
Reduction of
injury
Reduction of
injury
Reduction of
injury
No effect
16

Dreyfuss et Saumon,
AJRCCM 1998

Peep may favor VILI
Dreyfuss ARRD 1993
19

Cytokines in BAL ex vivo
Ricard et al, AJRCCM, 2001.
21

Cytokines in BAL in vivo
Ricard et al, AJRCCM, 2001.
22

Mercat et al.
27

Meade et al.
28

Conclusions
• VILI caused by overdistension of open units
– Experimental data: overwhelming evidence
– Clinical relevance: plausible
– Major importance of end-inspiratory lung volume
• VILI caused by opening and collapse
– Experimental data: ambiguous
– Clinical relevance: remains to be demonstrated after 3 negative
RCTs
– Peep need not be « high » (except in case of major hypoxemia
despite high FIO 2 )
• Respective importance of physiologic studies and RCTs in
the improvement of prognosis of ARDS?

A plea for paleo-physiology
34