How Positive Pressure Ventilation Affects Vital Organs Functions

Shao-Hsuan Hsia, MD.Pediatric Critical Care Medicine, Chang Gung Children’s Hospital

Why is this topic important?

One’s meal is another one’s poisonRespiration affects several major body compartments: thorax, abdomen, cranium, muscle tissue spaces.Take care of the whole body, not only one organ systemAdverse effects of mechanical ventilation existRespiratory system dysfunction is potentially a cause of multiple organ dysfunction syndrome (MODS)

How Positive Pressure Ventilation Affect Vital Organs Functions

Respiratory system-cardiovascular system Respiration as exercise Increased lung volume Intrathoracic pressure Respiratory acidosis/alkalosis, inhalation gases

Respiratory system-vital organs Brain Liver Kidney

Oxygen toxicity

DO2=CO(1.34HbSaO2+0.003PaO2)

Increased Lung VolumeVt<12ml/kg: vagal withdrawaltachycardiaVt>15ml/kg: sympathetic withdrawal bradycardiaHumoral factors: cyclo-oxygenase inhibition, NOMechanical compression of LVPulmonary vascular resistanceVentricular interdependence

Pulmonary Vascular Resistence

Ventricular interdependence

*Positive pressure ventilation can restrict RV volume and decrease ventricular interdependence effects

*Ventricular interdependence can be worsened by pulmonary hypertension

Intrathoracic Pressure

Venous returnRV preload and afterloadLV preload and afterloadPulmonary resistence

Systemic Venous Return(RV Preload)

0Systemic Venous Return

Max

RAP

Spontaneous Breathing

PPV increases RAP

Volume expansion shifts the line to right

右心與正壓呼吸

RA

RV

Vena Cava

胸腔內 壓力上升PA

正壓呼吸器壓力

正壓呼吸器壓力

左心與正壓呼吸

LA

LV

Ao

Lung Lung正壓呼吸器壓力

正壓呼吸器壓力

Thoracic pump augmentation

左心與正壓呼吸

正壓呼吸與肺血管阻力

9.4

4.6

9.4

3.8

1.6

3.7

2.32.9

2.4

0

2

4

6

8

10

Paw PVR CI

Pre

HFJV

Post

* *

* ** *

Effect of HFJV on PAH

Meliones Circ 1991

*P<0.01 vs. HFJV

(n=13)

血液酸鹼值與肺血管阻力

0

5

10

15

20

25

30

35

40

CTL

Hypoxia

Resp alkalosis

Meta alkalosis

Hypoxia

**

Lyrene RK 1985

PV

R

*P<0.01 vs hypoxia

Effect of pH on PVR

呼吸氣體與肺血管阻力

呼吸氣體與肺血管阻力

42

27

0

5

10

15

20

25

30

35

40

45

0 ppm 20ppm

PAP (mmHg)

87

96

82

84

86

88

90

92

94

96

0 ppm 20 ppm

SaO2

Journois J T CVS 1994

NO for PAH post OP for CHD

How Positive Pressure Ventilation Affect Vital Organs Functions

Respiratory system-cardiovascular system Increased lung volume Intrathoracic pressure Respiratory acidosis/alkalosis, inhalation

gases

Respiratory system-vital organs Brain Liver Kidney

Oxygen toxicity

腦血流量監測

010

20304050

6070

Reduced Normal Elevated

GR/MDSD/PVSDead

CBF Groups

% of Patients

CBF vs. Glasgow outcome score: 3 months post injuryRobertson et al. 1992

Positive Pressure Ventilation and Cerebral Perfusion

Cerebral perfusion pressure=mean arterial pressureintracranial pressure CPP=MAP ICP (CVP when CVP>ICP)

PEEP ITP, VR, CVP Normal ICP: PEEP>10cmH2O ICP Increased ICP: PEEP<ICP is safe

McGuire et al 1997

PaCO2

PEEP vs. normal ICP

0

2

4

6

8

10

12

14

16

0 5 10 15PEEP

mm

Hg

79

80

81

82

83

84

85

86

87

ICP

CPP

* *

*p<0.05

PEEP vs. elevated ICP

0

5

10

15

20

25

30

35

0 5 10 15PEEP

mm

Hg

88

88.5

89

89.5

90

90.5

91

ICP

CPP

正壓呼吸與腦血流量

-0.1

-0.05

0

0.05

0.1

0.15

PIP off PIP on

CBV

HbO2

DOHb

Volum

e change(ml/100m

l brain)

Palmer, Acta Paediatr 1995

Impaired Pressure-Flow Autoregulation

Maximal Normal MaximalVasodilation Autoregulation Vasoconstriction

0 25 50 75 100 125 150 CPP (mmHg)

CBFUnexpected Ischemia

Unexpected Hypermia

Normal AutoregulationDisrupted AutoregulationPartial Disrupted Autoreg

經顱骨超音波都卜勒監測 -TCD

40 35 30 25 PaCO2

ICP PulsatilityIndex (PI)

Hyperventilation Vasoconstriction (Ischemia): ICP but PI

腦代謝率 CMRO2之監測

CMRO21.81.51.20.90.60.30

0 0.4 0.8 1.2

2.0

4.0

6.0

CBF(ml/gm/min)

AV

DO

2(m

ol/ml)

ischemia

infarction hyperemia

normal

hypo- perfusion

Robertson J of Neurosurg 1989

Positive Pressure Ventilation and Liver Function

Patients with sepsis, trauma and ARDS usually combine liver dysfunction—endotoxin, shock, hypoxemia and DICCO hepatic artery and portal vein blood flowITPhepatic vein pressure (Phv)hepatic flowDescending diaphragm compression intrahepatic closing pressure (Pc) sinusoidal cell-blood contact timePeak-inspiratory RAP hepatic blood flow pressure gradientabdominal pressure Ppv, and Pc

Pha

Rha

Ppv

Rpv

Ps Pc Phv

Pra

Diaphragm

Pab

Qha

Qpv

QLQvc

Matushak et al J Crit Care 1989

Hepatic blood flow interactions

0

20

40

60

80

100

IPPV1 PEEP1 PEEP2 IPPV2

ml/k

g/m

in CO

QLemf*P<0.001

+p<0.05

N=6

Matuschak et al. J Appl Physiol 1987

Positive Pressure Ventilation and Renal Functions

PPV may decrease CO and MAPThe partial occlusion of IVC increase renal vein pressure (RVP) and retention of Na and waterSympathetic nervous system/renin-angiotensin-aldosterone system/atrial natriuretic factor (ANF) system.

Positive Pressure Ventilation and Renal Functions

venous returndeactivate low pressure baroreceptor reflexesrenal blood flow, reninvenous return ANFNa and water retention

Renal Blood Flow vs. PEEP

-60

-40

-20

0

20

40

60

RVP

CO

RBF

ZEEP PEEP 10

RVP 10 PEEP 20

RVP 20

***

* **

Masahiro et al. CCM 1988

PEEP and Hormones

0

50

100

150

200

250

300

ANF PRAx20 Aldo NEx100 Epi

ZEEP

PEEP

Pierre et al. J Appl Physiol 1991

P<0.0001

P<0.02

PEEP and Natriuresis

0

50

100

150

200

250

300

Urine FeNa%x100 GFR SBP

ZEEP

PEEP

Pierre et al J Appl Physiol 1991

P<0.0003

P<0.0002

Schuller et al. Chest 1991, 100(4): 1068

-4

-3

-2

-1

0

1

2

3

4

5

6

0 12 24 36 48 60 72TIME (HOURS)

TO

TA

L I

/O (

L)

NON-SURVIVORS

SURVIVORS

Schuller et al. Chest 100(4): 1068, 1991

0

20

40

60

80

100

120

140

160

180

200

Survivors Non-survivors

Rat

e of

flui

d ac

cum

ulat

ion

(ml/h

r)

Survivors

Non-survivors

P=0.0005

Schuller et al. Chest 100(4): 1068, 1991

Conclusions (1)DO2 = CO (1.34 Hb SaO2 + 0.003PaO2)

Use heart-lung interactions Restrict airway pressure for RV failure Expand fluid volume to compensate venous

return Use positive pressure ventilation in LV

failure Optimize PEEPFRC to optimize PVR Avoid hypercapnea for pulmonary

hypertension

Conclusions (2)Avoid prolonged use of hyperventilation in IICPMonitor ICP and CPP vs. PEEPAvoid prolonged use of positive pressure ventilation in neonates with risk of ICHWatch liver function and coagulation factors Allow spontaneous (negative pressure) breath (IMV, SIMV)Watch fluid balance and NaUse constant flow in healthy lung

Mean Airway Pressure Decelerating Constant

Flow(l/sec)

AirwayPressure(cmH20)

MAP = Area Under Curve

PIP PIP

Gas Distribution