This document discusses mechanical ventilation for head injured patients. It provides an overview of various ventilator modes and settings including: 1) Volume control, pressure control, PRVC which aim to deliver a set tidal volume or pressure with variable volumes. Basic parameters like rate, PEEP and FiO2 are discussed. 2) Spontaneous modes like SIMV and PS which allow some patient breathing above a set rate with pressure support. 3) The importance of lung protective strategies using lower tidal volumes, optimal PEEP to recruit and splint alveoli open to prevent injury. New closed loop technologies aim to improve patient-ventilator synchrony and outcomes.

1. Mechanical Ventilation of
The Head Injured Patient
PJ Papadakos MD FCCM
Director CCM
Professor Anesthesiology, Surgery and Neurosurgery
Rochester NY USA

2. Do you
Know
This Guy ?

3. International Collaboration 1988-

4. There are Many
Modes

5. Where to Start ?
ASV, APRV, AutoFlow, AutoMode, AutoPEEP,
BiLevel, BiPAP, Closed Loop, CPAP, Control
Variables, Demand Flow, Differential Output,
Duty Time, EPAP, Flow Control Valves, Fluid
Logic, HFJV, HFOV, HFFI, HFPV, IPAP, Linear
Drive Piston, Mandatory Breath, MAP, MMV,
NEEP, PEEP, PIP, Phase Variables, Pplateau,
PCV, PCIRV, PRVS, PRVC, PSV, PV, Proportional
Amplifier, PAV, Rotary Drive Piston, Static
Compliance, SIMV, Threshold Resistor, Total
Cycle Time, Trigger Variable, Variable Pressure
Control, VCIRV, Volume Support, WOB…
from SP Pilbeam, Respiratory Care Equipment, Mosby

6. Outcome in intensive care depends on
ventilator settings.
Barbas, Amato, et al. Ap Card Path Nov 1996

7. GOALS OF MECHANICAL
VENTILATION
Provide oxygen for cellular metabolism

 Remove waste product of cellular
metabolism (carbon dioxide)

8. Basic Physiology
The Base of Good Care

10. 6.3 cc/kg
Tenny SM, Remmers JE Nature 1963. 197:54-6

11. ARDS Net
Showed that we are mammals!

12. Physiology of Atelectasis

17. Fact !
Each lung has
a tendency to
collapse

23. Factors
promoting
atelectasis
Low functional residual capacity (FRC)

Diminished surfactant function

Increased lung weight


24. The cycle opening and
closing of Alveolar Units
Deplete Surfactant and lead to
further collapse.

25. Intra-alveolar
proteins inactivate
pulmonary
surfactant in a
dose-dependent
way
Lachmann; Intens Care Med; 1994; 20:6-11

26. SURFACTANT
INACTIVATION
DECREASED
SURFACTANT
ACTIVITY
HIGH INCREASED
PERMEABILITY SURFACE TENSION
EDEMA AT ALVEOLAR WALL
INCREASED
SUCTION
FORCES ACROSS
ALVEOLAR
WALL

29. Presence of
atelectasis
Leads to impairment of host
defense
promotes nosocomial pneumonia

31. From our Lab in Rotterdam:

34. Effect of ventilation on renal
failure
100
% of renal failure
entry
75
72-96 h
50 535.9
507.2
280.1
25
86
14 18
18
0
Protective
Conventional
ventilation
ventilation
(n=22)
(n=22)

35. Effect of ventilation on hepatic
failure
% of hepatic failure
40
entry
30
72-96 h
20 535.9
507.2
280.1
10
23 9 5
0
0
Protective
Conventional
ventilation
ventilation
Ranieri et al. JAMA 2000;284, 43-
44
(n=22)
(n=22)

37. VENTILATOR MODES

38. Why Important ?
Managing the Patient/Ventilator system is

less difficult with an understanding of the
fundamentals of operation, alarms, and
capabilities.

39. Where to Start ?
ASV, APRV, AutoFlow, AutoMode, AutoPEEP,
BiLevel, BiPAP, Closed Loop, CPAP, Control
Variables, Demand Flow, Differential Output,
Duty Time, EPAP, Flow Control Valves, Fluid
Logic, HFJV, HFOV, HFFI, HFPV, IPAP, Linear
Drive Piston, Mandatory Breath, MAP, MMV,
NEEP, PEEP, PIP, Phase Variables, Pplateau,
PCV, PCIRV, PRVS, PRVC, PSV, PV, Proportional
Amplifier, PAV, Rotary Drive Piston, Static
Compliance, SIMV, Threshold Resistor, Total
Cycle Time, Trigger Variable, Variable Pressure
Control, VCIRV, Volume Support, WOB…
from SP Pilbeam, Respiratory Care Equipment, Mosby

40. Basic Ventilator Parameters
FiO2 Tidal volume (VT)
 
Fractional concentration of The amount of gas that is
 
inspired oxygen delivered delivered during inspiration
expressed as a % (21-100) expressed in mls or Liters.
Inspired or exhaled.
Breath Rate (f)

Flow

The number of times over a

one minute period inspiration The velocity of gas flow or

is initiated (bpm) volume of gas per minute

41. Control Modes

42. Volume Control
Rate
Tidal Volume
PEEP
FiO2
Inspiratory Time (set by cycle time)
Flow- which is set

43. Volume Control
Volume is constant
PIP’s are variable
Flow is either constant (square wave)
If patient breathes above set frequency
each breath will be the full preset volume.
Usually used for long term ventilation-
Home Care patients.

44. Volume Ventilation
50
Paw SEC
cmH20 1 2 3 4 5 6
-20
60
.
SEC
V
LPM 1 2 3 4 5 6
60

45. Orders: VC
Vt 600
Rate 12
FiO2 .40
PEEP 8

46. Typical Monitoring
Tidal Volume
Vent Rate
Patient Rate
PIP
FiO2
PEEP

47. Additional Considerations
Plateau Pressure
Airway Resistance (PIP-Plateau)
Compliance
Flow Rate
Inspiratory Time / Expiratory Time

48. Pressure Control
Rate
Inspiratory Pressure
PEEP
FiO2
Inspiratory Time
Inspiratory time controls I:E
200 L/Min Potential Flow

49. Pressure Control
PIP’s are constant
Volume is variable
Flow is decelerating pattern
If patient breathes above set frequency
each breath will be the full preset
pressure.

50. PC – What’s Different?
Flow is unrestricted
Lung may fill earlier in cycle
Specific control of inspiratory time
Potential for improved blood gas results
General improvement in comfort and
synchrony

51. Pressure Control
60
Paw
SEC
cmH20
1 2 3 4 5 6
-20
120
.
V
SEC
LPM
1 2 3 4 5 6
120

52. Pressure vs. Volume
Waveform
60
Paw
cmH20 1 2
-20
120
.
V
LPM 1 2
120

53. PRVC
Pressure Regulated Volume Control
Inspiratory pressure is titrated to achieve
the set tidal volume.
Pressure is regulated based on the patient
and system resistance/compliance during
the previous breath(s).
Tidal Volume is a target
(not absolute).

54. PRVC
Rate
Tidal Volume
PEEP
FiO2
Inspiratory Time

55. PRVC
Inspiratory Pressure is variable (3 cmH2O)
Tidal Volume is approximate
Decelerating (pressure) flow pattern
Hybrid mode that strives to achieve Vt at
lowest PIP.

56. Target Volume
Target Breath PTARGET
Pressure
PTARGET
PTARGET
CL increases
CL decreases
Insp VT (600 ml)
VT (500 ml)
restored
Target volume
Flow
(500 ml) VT (500 ml)
VT restored
VT (400 ml)
Exh

57. CMV MODE
Mode seen on Drager XL vents
Acts just like PRVC on Servo 300
Has feature called auto flow
CMV without the auto flow feature is
Volume Control
The I time on the XL is independent of the
rate. Therefore patients can be on lower
rates without a longer I time.

58. APRV
theory and use

59. APRV: description
APRV has been described as continuous

positive airway pressure (CPAP) with
regular, brief, intermittent releases in
airway pressure.
 The release phase results in alveolar
ventilation and removal of carbon dioxide
(CO2)

60. Theory of APRV
The CPAP level in APRV drives

oxygenation (CPAP generated with long
inverse I:E Ratio’s)
 The timed releases aid in CO2 clearance
(pressure release )
 APRV allows unrestricted, spontaneous
breathing throughout the entire
ventilatory cycle

61. T Low (time of low pressure duration) -

goal is to terminate the expiratory gas
flow at about 75% - 25% of peak flow.

63. Weaning APRV

64. Use the “Drop & Stretch” Method (decrease

the P High and increase the T High, make
sure you wean the P High slowly so the lungs
so not de – recruit)
When the T High reaches 10 – 15 seconds,

switch the patient to CPAP

65. Spontaneous
Modes

66. SIMV
Intermittent Mechanical Ventilation
Can be delivered by:
Volume
Pressure
Can use lower rates- So patient can breath
more on their own
The patient must now generate their own
tidal volume above the set rate

67. PS
Pressure Support
Inspiratory Pressure
Spontaneous Mode
(no rate or may be used in conjunction with IMV)
PEEP
FiO2
Decelerating Flow Pattern
Inspiratory time is terminated by flow and is
typically different for each type of ventilator.

68. PS
Constant IP
Volume is variable
Rate is variable (spontaneous effort above set rate)
Decelerating Flow Pattern
Inspiratory time is variable
 Terminates on declining flow at 5-25% above
baseline

69. Proper Mechanical Ventilation

71. Regional Spectrum of Opening Pressures
Opening
Pressure
Superimposed
Pressure Inflated 0
Small Airway 10-20 cmH2O
Collapse
Alveolar Collapse
40-60 cmH2O
(Reabsorption)
Consolidation
(modified from Gattinoni)

72. Once we recruit do we splint

73. PEEP
Physiologic
Lung Protective Strategy
Lung Recruitment
Remember:
PEEP IS GOOD!!

74. High volume injures, PEEP
protects
PIP=14, PEEP=0
PIP= 45, PEEP=10
PIP= 45, PEEP = 0
Webb&Tierney ARRD
1974;110;556

75. PEEP
Mathematical model
3000
Open-lung
PEEP 18 cmH2O
2500
Max tidal
2000
compliance
Volume (ml)
Decremental
1500
PEEP 15
Set PEEP here (after RM)
1000
500
Not here (LIP)
0
0 10 20 30 40 50 60
Hickling K. AJRCCM 2001;163:69-78. Pressure (cmH2O)

76. New Technology is in the forefront

77. Closed Loop Will Change Practice
Provide real time control

Provide weaning 24/7

Support complex patients

Decrease bedside

physician, nurse, and
therapist time
Improve Physiologic

Parameters.

78. Today

79. Neuro Control of Ventilator
NAVA
2009

80. NAVA concept
Nature 1999

81. Why NAVA?
Improves patient
ventilator synchrony
Turning
PSV NAVA
of switch
Data from Spahija, Sinderby et al
Sacre Coeur Hospital, Montreal
*

82. Acquiring Edi Signal

83. Further Reading

84. Many Thanks!

85. Many Thanks