Ventilation Modes and Current Trends

Denny Gish, BSRT, RRTClinical Specialist, Adult Respiratory Care

Legacy Emanuel Hospital and Health Center

Objectives

• Review current ventilator modes– Mode descriptions

• Review trends in Respiratory Care– ARDS Network recommendations – Best PEEP– Recruitment Maneuvers

• Identify various methods of High Frequency Ventilation

Modes of Ventilation

The Critical Question...

How do you choose ?

Ventilation Strategy

Anticipated short-term need for ventilatory support or otherwise stable patient with DNI status

Place on conventional ventilation

Does patient improve?

Does pt have non-compliant lungs, ARDS or meet moderate criteria for

ISS?

Is pt on appropriate PEEP, recruitment maneuvers, and/or appropriate fluid / volume support?

Apply combination of optimal PEEP, recruitment maneuvers, and/or

cardiovascular support.

Pt improvement over the past 12 hours? (P/F ratio >200)

Continue with conventional ventilation

Patient improvedP/F ratio over 8-12

hours

Consider APRV, ARDS Network Protocol or VDR

Does the patient have a large volume of secretions, thermal lung injury, wet ARDS, extremely narrowed airways or uncontrolled air leak?

Place on VDR

Place on APRV or ARDS Network

Protocol See attached document

Patient improvement over 8-12 hours? (P/F ratio >200)

Continue APRV

Use APRV and check the following - Is patient trapping 70% of airflow? - Is pHigh at a maximum setting? - Have recruitment techniques been applied? - Is cardiac support adequate? - Is there unilateral lung disease? - Is there severe airway obstruction?

Patient improvement over 8-12 hours? (P/F ratio >200)

Continue APRV

Consider VDR

Consider Non InvasiveVentilation.

Does patient improve?

Continue NIV

Place on APRV

Continue APRV or ARDS Network protocol

Continue conventional ventilation.

Consider SmartCare mode / Best Practice Bundle to prepare for extubation.

What Starts the Breath ?

• Controlled or timed breaths• Controller is really an interval timer• Assisted breaths are triggered by patient

inspiratory effort in addition to Controlled breaths

• Spontaneous breaths allowed in some modes

What Ends the Breath ?

• Preset pressure reached• Preset volume is delivered• Preset time has elapsed

Ventilator Settings• Mode: Volume control, Pressure control, Spontaneous, etc

(how the breath goes in)

• Vt:Tidal Volume (size of breath 8-10 cc/kg, 4-6cc/kg for ARDS)• “Volutrauma” can be as damaging as “Barotrauma”

• f : Frequency (rate # breaths per minute 10-15 bpm)

• PEEP: Positive End Expiratory Pressure (>/= 5 cmH20)

• IP: Inspiratory Pressure (ideally < 30 cmH20)

• FIO2: Fraction of Inspired Oxygen

All ordered by MD or by unit protocol• Ti or V: Inspiratory time or Flowrate (how long it takes the breath

to go in - generally per RT discretion based on pt comfort & condition)

Ventilator Measurements• Vt = tidal volume - cc’s or ml’s

• f = frequency, # breaths per minute - bpm• Ve = minute ventilation ( Vt * f) liters per minute

• I:E Ratio= insp time to exp time (norm is 1:2)• PIP (or PAP) = Peak Inspiratory Pressure – cmH20• MAP = Mean Airway Pressure – cmH20• PEEP = Positive End Expiratory Pressure – cmH20• Pplat = Plateau or Static Pressure (true lung inflation

pressure (eliminates airway & tubing resistance) – cmH20

• Cstatic = Static Compliance (normal 40-60 ml/cmH2O)Learn to read measurements off vent screen

Some Basic Modes

• Volume Control: set Vt & f, pt may assist

• Pressure Control: set IP & f, pt may assist

• Synchronized Intermittent Mandatory Ventilation: set Vt & f, pt may take unassisted spontaneous breaths as well– Mandatory Minute Volume Ventilation – MMV: mandatory breaths

are only provided if spontaneous breathing is not sufficient and below the prescribed minimum ventilation.

• Pressure Support: pt’s own Vt & f, supported by insp boost to augment pt’s insp efforts. Pt may breathe deep or shallow, fast or slow w/o intervention from vent.

Name that Mode of Ventilation

Evita XL – Ventilation Modes

• CMV– Continuous Mandatory Ventilation

*AKA- Assist/Control

• MMV– Mandatory Minute Ventilation

*AKA-Smart SIMV

• PCV–Pressure Controlled Ventilation

*used when PIP is >35

• APRV– Airway Pressure Release Ventilation

*Low compliance disorders

• CPAP-Continuous Positive Airway Pressure – with or without PS

Draeger V 500Ventilation mode

VC-CMV - Draeger XL has CMV, but it is NOT the same!

VC-AC–Works like CMV on the Draeger XL

VC-MMV-Draeger XL has MMV and it performs exactly like the VC-MMV on the V500

PC-AC – Draeger XL has PCV

PC-APRV with AutoRelease - Draeger XL does not have an autorelease function

SPN-CPAP/PS/VS-Draeger XL has CPAP mode that has Pressure Support capabilities, but no Volume Support

Now…Puritan Bennet 840

Viasys Avea

Servo I buy

More Advanced Modes• Volume Support: pt’s own f w/PS for goal Vt. Vent

guarantees Vt by adjusting the PS based on lung compliance and/or resistance to ensure a preset tidal volume.

• Pressure Regulated Volume Support: set f and goal Vt, pt may assist. Ventilator automatically adjusts pressure up or down, from breath to breath, as patient's airway resistance and lung compliance changes, in order to deliver the goal tidal volume.

• Volume Control Plus: same as PRVC

• Airway Pressure Release Ventilation: High and low pressures set w/minimal timed releases to facilitate gas exchange, high MAP w/very Inverse I:E ratio. Pt may breathe spontaneously during high pressure holds.

ARDS Current Definition

• Onset - Acute and persistent• Radiographic - Bilateral pulmonary

infiltrates • Oxygenation - regardless of the PEEP, with

a Pao2/Fio2 ratio 300 for ALI and 200 for ARDS

• Exclusion criteria - Clinical evidence of Left Atrial Hypertension or a PAOP of 18 mm Hg.

Bernard GR et al., Am J Respir Crit Care Med 1994

The 1994 North American-European Consensus Conference The 1994 North American-European Consensus Conference (NAECC) Criteria:(NAECC) Criteria:

Tidal Volume Strategies in ARDS

Traditional ApproachTraditional Approach

High priority to traditional High priority to traditional goals of acid-base balance goals of acid-base balance and patient comfortand patient comfort

Lower priority to lung Lower priority to lung protectionprotection

Low Stretch ApproachLow Stretch Approach

High priority to lungHigh priority to lung protectionprotection

Lower priority to Lower priority to traditional goals of acid-traditional goals of acid-base balancebase balance

and comfortand comfort

Physiologic Benefits vs Patient-Important Outcomes

PaO2 improvementPaO2 improvement vs vs Survival BenefitSurvival Benefit• For ARDS, inhaled nitric oxide For ARDS, inhaled nitric oxide improves PaO2, but not improves PaO2, but not

mortalitymortality(Taylor et al, JAMA 2004;291:1603)

• High tidal volumes in patients with ARDS High tidal volumes in patients with ARDS improvesimprovesPaO2PaO2, , but mortality is lower for small tidal volumesbut mortality is lower for small tidal volumes

(ARDSnet, N Engl J Med 2000; 342:1301)

• For ARDS, prone position For ARDS, prone position improves PaO2, but notimproves PaO2, but notmortalitymortality

(Gattinoni, N Engl J Med 2001;345:568)

ARDS Network Low VT Trial

Patients with ALI/ARDS of < 36 hours

Ventilator procedures • Volume-assist-control mode• 6 vs. 12 ml/kg of predicted body weight Vt

(PBW/Measured body weight = 0.83)• Plateau pressure 30 vs. 50 cmH2O• Ventilator rate 6-35 to achieve a pH goal

of 7.3 to 7.45 • Oxygenation goal: PaO2 55 - 80 mmHg, SpO2 88 - 95%

) ARDS Network. N Engl J Med. 2000.

Lung Recruitment

First and foremost performed to provide an arterial oxygen saturation of 90% or greater at an FiO2 of less than 60%

Recruitment of nonaerated lung units (open-lung concept) but risk of regional lung overinflation :

a highly controversial issue!

Recruitment Maneuvers (RMs)Effective in improving arterial oxygenation at low PEEP and small tidal volumes. Recruitment maneuvers may be poorly effective or deleterious, inducing overinflation of the most compliant regions, hemodynamic instability, and an increase in pulmonary shunt resulting from the redistribution of pulmonary blood flow toward nonaerated lung regions.The effect of recruitment may not be sustained unless adequate PEEP is applied to prevent derecruitment.Many questions still need to be answeredMany questions still need to be answered

PEEP in ARDS:How much is enough ?

PEEP, by avoiding repetitive opening and collapse of atelectatic lung units, could be protective against VILIPEEP, has been shown to prevent surfactant loss in the airways and avoid surface film collapse. The lung is kept open by using PEEP to avoid end-expiratory collapse.High PEEP should make the mechanical ventilation less dangerous than low PEEP.

Levy MM. N Engl J Med. 2004.Rouby JJ, et al. Am J Respir Crit Care Med. 2002.Gattinoni L, et al. Curr Opin Crit Care. 2005.

Optimizing PEEPOptimizing PEEP

• Optimizing PEEP.– PEEP level is at low

lung volume and below critical opening pressure.

– PEEP increased to optimize compliance.

larson

ARDS Network Low VT Trial

Allowable combination of FiO2 and PEEP:

FiOFiO22 0.3 0.4 0.4 0.5 0.5 0.6 0.7 0.7 0.7 0.8 0.9 0.9 0.9 1.0 1.0 1.0 0.3 0.4 0.4 0.5 0.5 0.6 0.7 0.7 0.7 0.8 0.9 0.9 0.9 1.0 1.0 1.0 1.01.0PEEP 5 5 8 8 10 10 10 12 14 14 14 16 18 18 20 22 PEEP 5 5 8 8 10 10 10 12 14 14 14 16 18 18 20 22 2424

APRV Mode

• First described 1987• Baseline airway pressure is the upper CPAP

level, and the pressure is intermittently “released” to a lower level, thus eliminating waste gas

• Time spent at low pressure (short expiratory time): prevents complete exhalation; maintains alveolar distension

APRV Evidence

• Prospective, randomized intervention study (N=45); PC/PS vs. APRV; patients with ALI

• Oxygenation was significantly better in APRV group

• Sedation use and hemodynamics were similar

Puntsen, Am J Respir Crit Care Med,2001

APRV settings

Flow

Paw

Thigh Tlow

Phigh

Plow

insp

exp

“If this...

why not this?”

- John B. Downs, MD

High Frequency Ventilation

HFOVOscillatory

HFJVJET

HFPVPercussive

High Frequency Percussive Ventilation

HFPV

• -High Frequency Percussive Ventilation (HFPV) is a hybrid form of high frequency ventilation.

• -This concept of pneumatic diffusive / convective protocols is not related to high frequency vibration, jet insufflation or electronically controlled crank or magnetically servoed dynamic oscillators.

Rationale for HFV-Based Lung Protective Strategies

• HFV uses very small tidal volumes– Avoids excessive end-inspiratory lung volumes– Allows for higher end-expiratory lung volumes

to achieve better recruitment• HFV uses much higher respiratory rates

– Allows for maintenance of normal PaCO2 even with very small tidal volumes

High-frequency Ventilation• HFOV may improve oxygenation when used as a rescue

modality in adult patients with severe ARDS failing CV.HFOV may be considered for patients with severe ARDS:• FiO2 > 0.60 and/or SpO2 < 88% on CV with PEEP > 15 cm H2O,

or• Plateau pressures (Pplat) > 30 cmH2O, or• Mean airway pressure 24 cm H2O, or• Airway pressure release ventilation Phigh 35 cm H2O

HFOV for adults with ARDS is still in its infancy and requires further evaluations.

Higgins J et al., Crit Care Med 2005

High Frequency Percussive Ventilation

HFPV• -High Frequency Percussive Ventilation (HFPV) is

a hybrid form of high frequency ventilation.• It is a combination of convective style ventilation

and percussive high frequency linked together.

Inverse Ratio Ventilation

• Technique used prior to latest generation of vents• Used in refractory hypoxemia• Another way to increase FRC• Expiratory time is longer than inspiratory time.• Heavy sedation/paralytics required • Fluids, pressors usually needed as well due to

decrease in venous return to thorax

Sometimes occurs inadvertently by erroneous vent changes or pt agitation & high RR. Must be corrected!

Other Advanced InterventionsRequire separate or additional machines

• Inhaled Nitric Oxide selective pulmonary artery vasodilator. Used for pulm htn, lg saddle PE’s, to reduce intrapulmonary shunting & improve V/Q matching. Prohibitively expensive, may cause methemoglobin buildup

• High Frequency Ventilation high frequency (>200 breathes per min) – HFOV, HFJV, HFPV

• Extracorporeal Membrane Oxygenation (ECMO) similar to bypass pump used in cardiac surgery

Adjuncts

• Recruitment Maneuver– PEEP - does not recruit alveoli, but can help

maintain alveolar stability

• Prone positioning – has not changed morbidity or mortality outcomes in ARDS, but has been shown to help improve oxygenation

A man suffered from insomnia and dyslexia. He was also an

agnostic. What did he do?

He stayed up all night wondering if there was a DOG.