2011 New ventilation modes in Anaesthesiology

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New modes of mechanical ventilation in

AnaesthesiologyJan P Mulier MD PhD

Sint-Jan Brugge-Oostende

K U Leuven

J P Mulier New Ventilation modes Wintersymposium Leuven 8 1 2011

1150 1850 1947 1977 2010


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Do we need New Ventilation Modes?

Old problems not solved ?Atelectasis: peep & recruitmentSynchronisation problems

New patient population? Extreme age, sizeNeonati - very old – surgery less invasiveMorbid obese - anorexia

New insight in physiology?Volutrauma is more important than barotraumaPermissive hypercapnia, hypoxia instead of biotrauma

Measuring atelectasis

Attention & Awareness

Use of peep and recruitment


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Do we need New Ventilation Modes?Old problems not solved or new problems?

Ventilator associated tracheitis (VAT) to ventilator associated pneumonia (VAP)

Synchronisation problems


New insight in physiology?Volutrauma is more important than barotraumaPermissive hypercapnia, hypoxia instead of

biotrauma


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Do we need New Ventilation Modes?

New problems or old problems not solved?Atelectasis problems,

VAT to VAPSynchronisation

problems

Not a problem in anesthesia ?


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New insight in physiology?Volutrauma is more important than barotraumaPermissive hypercapnia, hypoxia instead of

biotrauma


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New insight in physiology?Volutrauma is more important than barotraumaPermissive hypercapnia, permissive hypoxia,

prevention of biotrauma


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Do we have New Ventilation Technology?

A. Support matched with the patient demand: synchronisation problem: not for anesthesia Proportional assist ventilation (PAV) Neurally adjusted ventilatory assist (NAVA)

B. Breath-to-breath variability: improves oxygenation: more physiologic in anesthesia? Biologically variable ventilation (BVV) Fractal ventilation (FV)

C. Complex closed loop technology: ventilation is continuously adapted to the patient’s lungfunction: usefull

in anesthesia? The adaptive support ventilation (ASV)


9Proportional assist ventilation PAV

• Instantaneously delivered positive pressure throughout inspiration in proportion to patient- generated flow (flow assist) and - volume (volume assist).

• PMUS =R×V+E×VT +PEEPi−PAW

• PAW=FA×V+VA×VT

• An increased effort would correspond to increased support: the more the patient requests, the more the ventilator delivers.

• Unlike other assistance techniques, flow, volume, and airway pressure are not preset.


10Neurally adjusted ventilatory assist NAVA

Overcomes the limitations of PAV

The electrical activity of the crural dia- phragm (EAdi) by means of an esophageal array of bipolar electrodes is measured.

Synchrony between neural and mechanical inspiratory time is guaranteed both at the onset and at the end of inspiration, regardless of PEEPi, air leaks, and respiratory mechanics

Intact respiratory centers, phrenic nerves, and neuromuscular junctions needed.

Ventilatory drive is suppressed by drugs during anesthesia!


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Biologically variable or fractal ventilation BVV

Mimics spontaneous breath-to-breath variability, incorporating natural variable noise into a volume-targeted, controlled mode.

The ventilator modulates respiratory rate and tidal volume while maintaining a fixed minute ventilation.

alveolar recruitment achieved by high volumes exceeds the de-recruitment caused by small volumes


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Adaptive Support Ventilation ASV

A closed-loop control mode that may switch automatically from a PCV-like behaviour to a PSV-like behaviour, according to the patient status.

Pressure levels and ventilation rate are automatically adjusted according to measured lung mechanics at each breath.

ASV provided a safe and effective ventilation in patients with normal lungs, restrective or obstructive diseases.


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What do we need in anesthesia?


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Let us take something simple that improves outcome. First step

1. Increasing blood pressure at end of surgery allows surgeon to find possible bleeding arteries and by clipping preventing post operative bleeding.

J. Mulier Obes Surg 2007; 17: 1051

110/57 145/78


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ASA 2010


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Let us take something simple that improves outcome. First step

1. Increasing blood pressure at end of surgery allows surgeon to find possible bleeding arteries and by clipping preventing post operative bleeding.

How can we increase blood pressure? Vasoconstriction or cardiac output increase?

Preload-, heart rate- or contractility rise, afterload increase.

Why not using hypercapnia: it stimulates sympathetic output, increasing heart rate and contractility, decreasing peripheral resistance.


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Hypercarbia effects

Bille-Brahe NE Acta Chir Scand Suppl. 1976; 472: 127-32. Cardiovascular effects of induced hypercarbia during halothane-nitrous oxide anaesthesia.

Heart rate, cardiac index, systemic and pulmonary blood pressures rose as pCO2 was increased. Stroke volume, systemic and pulmonary vascular resistance remained unchanged.

In conclusion the primary effect of hypercarbia was an increased heart rate and a resultant increase of cardiac output.

The pressure changes merely reflect the effect on cardiac output.


18Hemodynamic effects of Hypercapnia (vs hypoxia)

Peripheral chemoreceptor contributions to sympathetic and cardiovascular responses during hypercapnia.

Shoemaker JK Can J Physiol Pharmacol. 2002; 80: 1136.


19Hypercapnic vs. hypoxic control of cardiovascular, cardiovagal, and sympathetic function. Steinback CD Am J Physiol Regul Integr Comp Physiol. 2009; 296: R402.


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Permissive Hypercapnia vs Normocapnia under general anesthesia in obese patients while giving ephedrine to elevate SAP

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SAP et PCO20

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J Mulier Anesthesiology ESA 2008 A174

ephedrine CO min vol0

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normocapnyhypercapny


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Let us take something simple that improved outcome. Second step

1. How do you increase blood pressure at end of operation to find surgical bleeding?

Permissive hypercapnia

2. But breathing against ventilator with elevated CO2.Deep NMB or support ventilation without NMB?


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Let us take something simple that improved outcome. Second step


Permissive hypercapnia

2. But breathing against ventilator with elevated CO2.Deep NMB or support ventilation without NMB?

3. PSV is possible at partial NMB. To what depth of NMB is this impossible? TOF 1 or 0 ?


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To what depth of NMB is PSV possible?

TOF 4/

4 10

0 %

TOF 4/

4 50

%

TOF 3/

4

TOF 2/

4

TOF 1/

4TO

F 0/

4 PT

C 10

PTC

5

PTC

0

0

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RR

min vol

Profound muscle relaxation does not disturb pressure support ventilation. J Mulier 2009 PGA


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PSV during infusion of total dose 2 mg/kg rocuronium over 10 minutes

PSVPro during esmeron infusion

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0

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time

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EtCO2

NMT count

RR(CO2)

PTCount

SpO2

Profound muscle relaxation does not disturb pressure support ventilation. J Mulier 2009 PGA


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Is deep NMB usefull? Effect of deep muscle relaxation on IAP (intra

abdominal pressure) with constant IAV (intra abdominal

volume)

Gradual pressure drop until flat line

Max effect at TOF = 0/4

No need to drop until PTC = 0effect of deeping relaxation with cst IAV

0

500

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1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76

TO

F a

ns

we

r

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IAP

NMT(R1)

NMT(R4)

IAP

TOF 4/4 TOF ¼ PTC 10 PTC 5 PTC 0

J Mulier 2009 PGA


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Effect of deep muscle relaxation on abdominal PV loop

TOF > 90%

TOF = 0/4

TOF 0/4 and PTC < 5

02468

101214161820

-1 -0,5 0 0,5 1 1,5 2 2,5

J Mulier 2009 PGA


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Let us take something simple that improves outcome.


Permissive hypercapnia Increase in cardiac output reduces wound infection!Hypercapnia reduces VILI, but peep needed

2. But breathing against ventilator with elevated CO2.Support ventilation is possible during deep muscle relaxationHypercapnic PSV allows faster awakening.

3. Is support ventilation possible during NMB?Even at maximum depth, TOF 0 and PTC 0, PSV is possible!When is PSV not possible? Respiratory center depression?


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High dose Morphine blocks respiratory center making PSV impossible.

0:00 0:02 0:05 0:08 0:11 0:14 0:17 0:20 0:23 0:25 0:280

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Respiratory Rate

RR

TO

F 4

/4

TO

F 1

/4

PTC

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TO

F 0

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PTC

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Roc

Suf

Escape PCV

1. I Casier, J Mulier ESA 2010

Aestiva S/5 with a trigger sensitivity of less than 0.6 L/min. Backup ventilation mode was set to start after 30 second of no ventilation.

Rocuronium infusion was given at 500mg/h till TOF and PTC were 0.

Then Rocuronium infusion was stopped en Sufentanil 25µg was given.


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Dosing sufentanil to maximum level without respiratory depression opens new method to optimize immediate post

operative pain treatment

Before after extra 5 ug Sufentanil

I Casier, J Mulier ESA 2010


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Effect of et CO2 on blood pressure


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Health & Medicine

2011 New ventilation modes in Anaesthesiology