In the era of lung protective ventilation, is it time to consider a cardioprotective ventilatory strategy for patients with severe ARDS.

1. Dr Mohamad Abdelsalam
ICU Department
KFHJ

2. Why Is RV Failure
Particularly Important In
ARDS?

3. Acute right ventricular failure
can adversely affect the outcome
of acute respiratory distress
syndrome.

4. How Does RV Failure
Affect LV Function?

5. Acute RV failure can compromise
LV function by decreasing LV
diastolic filling.

6. In acute pressure or volume
overload, RV dilatation shifts the
interventricular septum to the left,
thereby decreasing LV volume,
diastolic filling and cardiac output.

8. Also, low right-sided cardiac output
can result in left-sided underfilling
and decreased LV stroke volume.

9. By reducing cardiac output, acute
decompensation of the right
ventricle can compromise oxygen
delivery and initiate or potentiate
tissue hypoxia.

10. Role Of Mechanical Ventilation In
Acute RV Failure.

11. Mechanical ventilation plays a
key role in the development of
acute RV failure in patients with
ARDS.

12. How Does High PEEP
Alter RV Function?

13. By increasing intrathoracic
pressure, PEEP may reduce venous
return and decrease RV preload.

14. By increasing airway pressure,
PEEP may overdistend alveoli and
compress alveolar capillaries,
resulting in an increase in
pulmonary vascular resistance and
hence RV afterload.

15. PEEP may reduce cardiac
output either by decreasing RV
preload or increasing RV
afterload.

16. Plateau Pressure As An
Important Predictor Of Acute
Cor Pulmonale In ARDS.

17. Low Tidal Volume Ventilation Has
Become The Standard Of Care For
Patients With ARDS
The progressive reduction in tidal volume
and plateau pressure has been associated
with a dramatic decrease in the incidence of
acute cor pulmonale.

18. A recent study of more than 350
patients with ARDS has found a strong
relationship between plateau pressure
and the incidence of acute cor
pulmonale.
Jardin and Vieillard-Baron. Intensive Care Med, 2007.

19. For a plateau pressure < 27 cm H2O,
the incidence of acute cor pulmonale
was very low (~ 10%).

20. When the plateau pressure ranged
from 27 to 35 cm H2O, the incidence
of acute cor pulmonale reached 30%.

21. At a plateau pressure >35 cm H2O,
60% of the patients developed acute
cor pulmonale.

22. The right ventricle rapidly
fails as the plateau pressure is
progressively increased.

23. Serial echocardiography in a patient with severe ARDS illustrating the impact of
plateau pressure on RV function and hemodynamics.

24. PEEP As A Predictor Of
Acute Cor Pulmonale In
ARDS.

25. Does Increasing PEEP While
Limiting Plateau Pressure Alter
RV Function?

26. In a small series of patients with severe
ARDS, a group of investigators compared a
low level with a high level of PEEP titrated
for a plateau pressure of 30 cm H2O.
Mekontso et al. Intensive Care Med, 2009.

27. In the high PEEP group,
echocardiography showed marked
RV dilatation with paradoxical
septal movement.

28. Panel A, ARDS patient ventilated with a PEEP of 7 cm H2O and plateau pressure
of 27 cm H2O. Panel B, 15 minutes after increasing PEEP to 14 cm H2O, with the
same plateau pressure (by decreasing tidal volume).

29. Increasing PEEP while limiting
plateau pressure may alter RV
function and depress cardiac output.

30. Another group of investigators studied the
effect of increasing PEEP on RV function in
patients with severe ARDS ventilated with
low tidal volume and limited plateau
pressure.
Fougeres et al. Crit Care Med, 2010.

31. They found that increasing PEEP
while limiting plateau pressure to 30
cm H2O did not increase the incidence
of acute cor pulmonale.

32. Open lung strategy with high PEEP,
low tidal volume and limited plateau
pressure may be hemodynamically
well tolerated.

33. Why Does The Impact Of PEEP On
RV Function Vary Greatly Among
Patients With ARDS?

34. Data are conflicting regarding the
hemodynamic impact of high PEEP
on RV function during lung
protective ventilation.

35. Is It The Effect Of PEEP On The Lung
(Recruitment vs. Overdistension) That
Determines Its Impact On The Right
Ventricle?

36. The effect of PEEP on RV function
may be determined by its ability to
recruit the lung.

37. Lung recruitment improves lung
compliance, decreases plateau pressure
and improves oxygenation, all of which
are beneficial to the right ventricle.

38. PEEP-induced lung recruitment may unload the right
ventricle by decreasing plateau pressure and increasing
PaO2.

39. The greater the lung is recruited, the less the right
ventricle is overloaded.
Slutsky et al. NEJM 2006.

40. Conversely, when PEEP fails to recruit
the lung, it may induce overdistension,
thereby compressing pulmonary
capillaries and increasing RV afterload.

41. What is good for the lung (recruitment)
may be good for the heart (unloading)
and what is bad for the lung
(overdistension) may be bad for the
heart (overloading).

42. Improved Oxygenation Does Not
Necessarily Mean Improved
Outcome.

43. Three large randomized controlled
trials did not show a survival benefit
of high PEEP over low PEEP during
lung protective strategy.

44. High PEEP improved arterial
oxygenation but failed to
improve survival of patients
with ARDS.

45. RV failure may explain why
high PEEP failed to improve
outcome of ARDS.

46. Despite its beneficial effect on lung
recruitment, high PEEP could have
been detrimental to RV function,
cardiac output and oxygen delivery.

47. SaO2 vs. SvO2 ─ What Should Be
Our Goal?

48. Cardiac Output Is The Major
Determinant Of Oxygen
Delivery.

49. Decreased cardiac output associated
with high PEEP counterbalances the
increase in oxygen saturation, and
oxygen delivery is ultimately
reduced.

50. PEEP May Paradoxically
Reduce Oxygen Delivery.

51. The primary goal of mechanical
ventilation is to maintain adequate
tissue oxygenation, while avoiding
ventilator-induced lung injury.

52. The adequacy of tissue oxygenation is
better assessed by measuring mixed or
central venous oxygen saturation rather
than arterial oxygen saturation.

53. SaO2 represents arterial
oxygenation, while SvO2 reflects
the balance between oxygen
delivery and oxygen consumption.

54. SvO2 is a more reliable index of
oxygen delivery and tissue
oxygenation than SaO2.

55. SaO2 vs. SvO2 ─ What
Determines Optimal
PEEP?

56. The Ultimate Goal Of PEEP
Is To Increase Oxygen
Delivery.

57. Optimal PEEP may be the level of
PEEP at which oxygen delivery
(rather than oxygen saturation) is
maximal.

58. Accordingly, PEEP can be adjusted
to achieve the highest SvO2 (or
ScvO2) rather than SaO2.

59. Cardioprotective Ventilatory
Strategy.

60. Echocardiography is considered
the best method for noninvasive
assessment of RV function.

61. Abnormal echocardiographic findings
in ARDS include RV dilatation,
paradoxical septal motion and biphasic
pattern of pulmonary blood flow, which
indicates severe acute cor pulmonale.

62. TEE of mechanically ventilated patient with severe ARDS
showing RV dilatation and paradoxical septal motion.
Caille and Viellard-Baron. Open nuclear Med J, 2010.

63. Echocardiography allows the
adjustment of ventilator settings (tidal
volume, PEEP and plateau pressure)
according to RV function.

64. In the presence of echocardiographic
evidence of RV failure, ventilatory
management should aim to limit the
plateau pressure to < 27 cm H2O.

65. At a plateau pressure below 27
cm H2O, the incidence of acute
cor pulmonale is very low.

66. Plateau pressure limitation, on the
other hand, requires progressive
reduction of tidal volume which often
leads to hypercapnia, a potent
pulmonary vasoconstrictor.

67. Correcting hypercapnia by increasing
respiratory rate may induce intrinsic
PEEP, which can adversely affect the
function of the right ventricle.

68. Balancing the cardioprotective effect of
pressure-limited ventilation with the
adverse hemodynamic consequence of
permissive hypercapnia is particularly
challenging in ARDS.

69. Low PEEP As An Important
Component Of The
Cardioprotective Ventilatory
Strategy

70. PEEP should be high enough to protect
against lung injury caused by
recruitment/derecruitment and to keep
the lung open at end expiration.

71. At the same time, PEEP should be low
enough to avoid alveolar
overdistension which is both
detrimental to the lung and to the right
ventricle.

72. PEEP should be titrated to open
the lung and keep it open without
overloading the right ventricle.

74. Protect The Lung And
The Heart As Well.

75. Remember that limiting plateau
pressure to below 27 cm H2O (by
decreasing tidal volume and PEEP) is
the most important component of
cardioprotective ventilatory strategy.

76. Do No Harm Rather
Than Do Good.

77. Remember that the only strategy that
improved outcome of ARDS did so
because of doing no harm (avoiding
ventilator-induced lung injury) NOT
doing good (improving oxygenation).

78. Thank You