Mechanical Ventilation for Head Injury

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

Do you Know This Guy ?

International Collaboration 1988-

There are Many Modes

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

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

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

Basic Physiology The Base of Good Care

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

ARDS Net Showed that we are mammals!

Physiology of Atelectasis

Fact ! Each lung has a tendency to collapse

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

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

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

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

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

From our Lab in Rotterdam:

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)

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)

VENTILATOR MODES

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

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

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

Control Modes

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

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.

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

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

Typical Monitoring Tidal Volume Vent Rate Patient Rate PIP FiO2 PEEP

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

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

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.

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

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

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

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).

PRVC Rate Tidal Volume PEEP FiO2 Inspiratory Time

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.

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

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.

APRV theory and use

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)

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

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

Weaning APRV

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

Spontaneous Modes

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

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.

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

Proper Mechanical Ventilation

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)

Once we recruit do we splint

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

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

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)

New Technology is in the forefront

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.

Neuro Control of Ventilator NAVA 2009

NAVA concept Nature 1999

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

Acquiring Edi Signal

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Mechanical Ventilation for Head Injury

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