Selling Auto mode. . .

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Selling Auto mode. . .
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Consensus Conference On Weaning
Chest. 2001120375S-396S Evidence-Based
Guidelines for Weaning and Discontinuing
Ventilatory Support A Collective Task Force
Facilitated by the American College of Chest
Physicians the American Association for
Respiratory Careand the American College of
Critical Care Medicine Neil R. MacIntyre,
Chairman, MD, FCCP
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Decreased LOS - Weaning

• 2 recent large multi-center randomized studies
• Large population randomized studies
• studied the success rates of T-piece, SIMV, and
  PS
• Estaban and Tobin study showed T-piece better
• Esteban, A., I. Alía, J. Ibañez, S. Benito, M. J.
  Tobin, and the Spanish Lung Failure Collaborative
  Group. 1994. Modes of mechanical ventilation and
  weaning a national survey of Spanish hospitals.
  Chest 106 1188-1193
• Esteban, A., F. Frutos, M. J. Tobin, I. Alía, J.
  F. Solsona, I. Valverdú, R. Fernández, M. A. de
  la Cal, S. Benito, R. Tomás, and et al. 1995. A
  comparison of four methods of weaning from
  mechanical ventilation. N. Engl. J. Med. 332
  345-350
• Brochard study showed PS better
• Brochard, L., A. Rauss, S. Benito, G. Conti, J.
  Mancebo, N. Rekik, A. Gasparetto, and F. Lemaire.
  1994. Comparison of three methods of gradual
  withdrawal from ventilatory support during
  weaning from mechanical ventilation. Am.
  J. Respir. Crit. Care Med. 150 896-903

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Decreased LOS - Weaning

• Most important information out of both studies
• Over half of the patients to be enrolled in the
  study could not be enrolled Why?
• Researchers needed to demonstrate that patients
  were ventilator dependant
• Well over 50 didnt need the ventilator
• Conclusion No idea which mode works best
• SIMV, although the most widely used method,
  probably works poorest

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Decreased Time on the Ventilator - Weaning

• Recent meta-analysis of all published work on
  weaning suggest that modes or methods of weaning
  have little statistical benefit
• ACCP Collective Task Force - MacIntyre, Chest.
  2001120375S-396S
• Evidence based review of the literature suggests
• Search for all possible causes of underlying
  pathology
• Test earlier if dependence pathology is resolved
• Patients may be more ready than you think
• 30 120 minute spontaneous breathing trials (SBT)

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What If They Fail The SBT

• Does this mean that it doesnt matter how they
  are supported until then?
• Probably not patients need to use respiratory
  muscles to prevent disuse atrophy while also
  avoiding fatigue from overuse
• How that partial support should be carried out
  remains under debate

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What If They Fail The SBT

• Support should decrease potential for fatigue
  while underlying causes of failure are corrected
• MacIntyre, Chest. 2001120375S-396S
• New support modes vary support levels to maintain
  minimum ventilation goals
• VS, and Auto mode are less weaning modes as good
  support modes
• Decreases fatigue as patient underlying problems
  are addressed

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Assisted Ventilation Breath Types
Pressure ConstantAssisted Ventilation
Volume Constant Assisted Ventilation

• Volume Ventilation (in CMV or SIMV)
• PRVC/VC/AutoFlow/APV
• VS/ASV/MMV

• PC (in A/C or SIMV)
• PS
• SPAP/BiLevel/PCV/BiVent
• Conventional IE or APRV

Auto-On
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Volume Support General Description

• Similar in function to PRVC except that patient
  drive controls insp time
• The clinician presets the target tidal volume
• Pressure rises or falls to maintain the set
  volume targets
• The overall clinical goal is to keep the tidal
  volumes at a clinician set level
• But allow more control over each breath by the
  patient

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VS Screen Shot
Demand decreases Spont Vt 7-Jul-09
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Volume Support Auto mode
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Potential VS Benefits Waking From Anesthesia or
Drug Overdose

• As patients begin to recover respiratory drive,
  it is not uncommon for staff to frequently turn
  PS up and down to keep patients stable
• VS offers automatic withdrawal or increase of
  spontaneous support as patients wake up

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Limitations To Volume Support For Waking Patients

• Patients may increase their workload too much
  after critical surgeries
• Increasing drive may lead to low support
  pressures
• Settable low pressure alarms can notify staff of
  low support
• Patients may lapse back into apnea causing
  excessive alarming
• Inspiration answer
• Auto mode

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Inspiration Solution - Auto mode

• Auto mode is not really a mode itself but a
  combination of using 2 modes at the same time
• Basically it works similar to the way apnea
  ventilation now works
• The patient can be ventilated in either a
  spontaneous or CMV mode
• If the patient stops breathing for an operator
  set time of apnea the ventilator switches from
  the spontaneous mode to the CMV mode
• If the patient triggers 2 sequential breaths the
  ventilator switches back to the SPONT mode

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Auto mode Description

• One advantage of Auto mode is in its simplicity
• There are no alarms for transitions in either
  direction
• Typically much shorter apnea times are chosen
  compared to alarmed apnea ventilation
• This creates a seamless transition for patients
  who may be in pressure or volume modes of
  ventilation
• But require routine backup ventilation and then
  recover spontaneous drive

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Transition Partners in Auto mode

• The transition is always between CMV and SPONT
  modes
• It simply and effortlessly transitions between
• SIMV is not involved in Auto mode
• V-CMV or PRCV-CMV VS
• P-CMV SPONT

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Potential VS Benefits Comfort And Safety During
Ongoing Support

• If set at satisfying tidal volumes, VS can make
  some patients more comfortable
• Often used in Peds and Neonates
• Improved synchrony and decreased sedation
• Popadakas State University of New York
• NICU patients are sometimes put on VS once they
  are over their acute disease and are growing

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Potential VS Benefits Waking From Anesthesia or
Drug Overdose

• As patients begin to recover respiratory drive,
  it is not uncommon for staff to frequently turn
  PS up and down to keep patients stable
• VS offers automatic withdrawal or increase of
  spontaneous support as patients wake up

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Advantages Of Auto Mode

• Advantages compared to SIMV weaning during the
  post operative period
• Decreased need for staff intervention
• 1/10TH the number of ventilator manipulations
• Decreased alarms and shorter time on the vent
• Decreased time of over and under ventilation
• Decreased variability of PaC02
• Roth, Crit Care Med 2001 2747-51

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PS Can Cause Central Apnea During Sleep
Especially in Heart Failure Pts.

• Hypocapnea combined with lack of wakefullness
  drive causes
• Central sleep apneas and sleep fragmentation
• Partharsarathy, Tobin, Am J Respir Crit
  Care Med 2002166(11)1423-1429

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PS Can Cause Central Apnea During Sleep

• Combined with lack of wakefullness drive causes
• Central sleep apneas and sleep fragmentation
• Partharsarathy, Tobin, Am J Respir Crit Care
  Med 2002166(11)1423-1429
• Automode could allow patients to remain on PS
  improving sensitivity to patient drive when
  present
• But add the backup support as breathing slows

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Selling Auto mode

• Applications for Auto mode are varied but the
  best and easiest to understand are in patients
  waking from anesthesia
• As patients go from asleep to partially awake it
  is often difficult to determine when they are
  ready to be extubated
• Many go back and forth in their breathing efforts
  for the first hour or two
• If they are left on V-CMV they are likely to
  fight as they wake
• If they are placed on PS, they may likely fall
  back under and stop breathing or have weak
  efforts and small tidal volumes causing alarms
  and stress
• Auto mode with VS and PRVC is particularly good
  at guaranteeing adequate ventilation in CMV while
  allowing comfortable ventilation