VENTILATION STRATEGIES

Alyssa Morris, R4July 15, 2010Thanks to Dr J Lord

OBJECTIVES Indications for ventilation Ventilation terminology Ventilation modes

NIPPV IPPV*

Cases ARDS Metabolic acidosis Asthma

SCM order sets

INDICATIONS

Rosen’s Chapter 11. Failure to maintain or protect

the airway2. Failure of oxygenation or

ventilation3. Anticipated clinical course and

potential for deterioration

TERMINOLOGY

f, RR = breaths per minute VE= VT x f (minute volume)

Amount of air that moves in and out of lungs/min

6-10L/min VT= VA + VD

4-10cc/Kg IBW FiO2= fractional concentration of inspired

oxygen 0.3-1.0 decrease to 0.6 or less asap

TERMINOLOGY

PEEP= positive end expiratory pressure 5-20 cmH20 Set vs. auto/intrinsic PEEP

Pinsp= set inspiratory pressure I time= inspiratory time (0.8-1.7s) E time= expiratory time I:E Ratio= I time : E time

TERMINOLOGY/PHYSIOLOGY Peak Inspiratory Pressure (PIP)

Occurs during inspiration >35cmH20 leads to alveolar over-distension/injury

Plateau Pressure Measured by occluding vent for 3-5 sec at end of

inspiration Should not exceed 30cmH20

Paw-mean= mean airway pressure= MAP Corresponds to area under the curve in P over T

curve Correlates with O2 delivered Inc I time = inc mean peak pressure= inc O2

delivery per ventilation

IBW PREDICTION RULES

MODES OF VENTILATION NIPPV

CPAP▪ Hypoxemic resp failure▪ Increasing the compliance decreases the WOB▪ Start at a pressure of 0-15ccH2O and increasing

as tolerated to decrease FiO2 BiPAP▪ Combo of CPAP and pressure support ventilation▪ use in fatigued pt b/c >support during inspiration▪ IPAP/EPAP (ex start at 10/5 or 12/6)▪ Has to be a pressure gradient of at least 5 ▪ Increase IPAP as tolerated

MODES OF VENTILATION

Indications for NIPPV (2 or more of): pH<7.35 with PaCO2> 44mmHg

respiratory distress with moderate to severe dyspnea

RR>25

NIPPV Contraindications

Cardiac or respiratory arrest Non-respiratory organ failure Severe encephalopathy (GCS<10) Severe UGIB Hemodynamic instability or dysrhythmia Facial surgery or trauma or deformity Upper airway obstruction Inability to cooperate/protect airway Inability to clear secretions High risk for aspiration

MODES OF VENTILATION IPPV

Volume-Cycled▪ Ventilator seeks to deliver a constant preset VT

▪ Do not take into account lung compliance Pressure-Cycled▪ Ventilator alters gas flow to achieve a preset

airway pressure over a preset I time ▪ Variable volumes are delivered to not exceed

preset airway pressure▪ Reduces alveolar overdistension

Combination Pressure-Volume cycled

MODES OF VENTILATION

Mode

Volume-cycled Pressure-cycled

CMV Both PSV AC SIMV PCV

MMV

CMV

Controlled Mechanical Ventilation Apneic, paralyzed, anesthetized patients Vent provides breaths at a set rate

regardless of pt effort▪ Each breath is triggered, limited and

cycled by the vent Rarely used now

ACAssist Control

Ventilator delivers preset VT at a set minimum rate

If patient attempts breath, vent delivers a full breath at the preset volume/pressure▪ AC-PC▪ AC-VC

Common initial setting Preset RR- patient can breath above or

machine will ensure gets preset rate Q: Can you see any problems that could arise with this setting?

ACAC-VC

Every breath is a controlled volume preset mandatory breath

Need to have normal lung and chest wall compliance

Advantage▪ When minute volume requirements are high

(ie. metabolic acidosis) Disadvantages▪ High peak pressures when compliance is low

ACAC-PC

Every breath is a controlled pressure preset mandatory breath

Indications▪ High pressures when using AC-VC▪ Inverse ratio ventilation▪ ALI/ARDS

Advantage▪ Airway pressure will not exceed level of set pressure

Disadvantage▪ When lung/chest compliance falls VT drops and

hypercapnia may occur

PSVPressure Support Ventilation

Use only in spontaneously breathing pts

Pressure support is given by vent on each patient initiated breaths

More comfortable Might not get enough volume, reach

mean airway pressure (decreased oxygentation)

Use when weaning

SIMVSynchronized intermittent

mandatory ventilation Pt receives only the set number of volume

controlled mandatory breaths which are synchronized with the pt

Additional breaths above set rate are pressure supported

More comfortable way to deliver volume controlled mandatory breats

Can use in inverse ratio ventilation and ALI/ARDS or pts with periodic apnea

SIMV

MMV

Mandatory Minute Ventilation Pressure support ventilation with a

volume-controlled back-up rate:▪ Set minimum minute ventilation ▪ If patient breathing above this, all PSV breaths▪ If patient not meeting minimum, volume-controlled breath(s) delivered to ensure MV

MODES OF VENTILATION

SETTINGSNo matter what mode of

ventilation you use, certain settings will need to be considered: Tidal volume RR PEEP FiO2 I:E

SETTINGS Tidal Volume

Normal lung- 8-10cc/kg IBW Diseased lung – 6-8cc/kg IBW

RR Usually start at 10-12/min▪ Exceptions: metabolic acidosis, asthma, ARDS

Base on the patient need and PaCO2 on gas FiO2

Start at 85-100% and quickly wean to 60% SaO2 goal usually >92%

SETTINGS PEEP

“physiologic” PEEP = 5cmH2O Use 5 as a minimum More depending on FiO2, intrinsic lung

dz, extra-thoracic pressure PEEP trial at the bedside ▪ Can use more to help wean to Fi02<60%

SE:▪ Increases intrathoracic pressure decreased

venous return decreased cardiac output

SETTINGSI:E

In normal spontaneous breathing it is 1:4

In intubated pt it is set at 1:2 to 1:4Sensitivity

Negative pressure required to trigger delivery

Usually set at 1-2cmH2O Intrinsic PEEP makes it harder for the

vent to sense a pt triggered breath

TROUBLESHOOTING

Adjusting the vent pCO2 too high pCO2 too low PO2 too high pO2 too low

pCO2 TOO HIGHPatient’s minute ventilation is too

low1. Increase rate or VT or both2. Improve dead space3. Decrease production: decrease temp,

stop seizures, decrease feedsSometimes you have to live with

the high pCO2 (Permissive hypercapnea) Target pH >7.2 May need bicarb infusion if pH <7.2

pCO2 TOO LOW

Minute ventilation is too high Lower either the rate or tidal volume Consider pain control or treating

anxiety

pO2 TOO HIGH

Your settings are working great Turn down the FiO2

pO2 TOO LOW

Increase the FiO2 or mean airway pressure Try to avoid FiO2>70% To increase MAP

1. Increase PEEP 2. Change modes and increase

inspiratory pressure or I time3. Recruitment maneuvers

QUESTIONS?

CASE 1

58M with 4d Hx of fever, productive cough and anorexia. O/E: T= 39.2, P= 111, RR= 32, 02= 91%

NRB, BP= 110/75 He looks very very tired and has

decreased AE thru’ out PMHx: HTN Meds: HCTZ

CASE 1

CASE 1 QUESTIONS What is the definition of ALI and

ARDS? What is your mode of airway

management? What are your settings going to be?

VT PEEP FiO2 RR I:E

Objective Determine whether ventilation with

lower tidal volumes would improve the clinical outcomes in pts with ALI/ARDS

ARDS NETInclusion

Intubated and mechanically ventilated

Acute decrease in PaCO2/FiO2 <300 Bilateral pulmonary infiltrates w

presence of edema No evidence of increased L atrial

HTN

ARDS NET Exclusion

>36hrs since they met the above criteria <18 Enrolled in other trials Pregnant Increased ICP Neuromuscular dz Sickle cell dz Severe chronic respiratory dz Burns >30% BSA Bone marrow or lung transplant Any condition w 6m survival <50% Chronic liver dz

ARDS NET METHOD

RCT Vent Procedures▪ AC until weaned or for 28 days minimum ▪ Control: 12cc/kg predicted weight with a plateau

pressure of 50cmH20▪ They could decrease by 1cc/kg to maintain pressure goal

▪ Treatment: 6cc/kg predicted weight w/I 4 hrs of randomization with a plateau pressure of 30cmH20 ▪ Could only increase to 8cc/kg to maintain pressure goal▪ Could give HCO3 for acidosis

Monitored for 28d

ARDS NET

Outcomes Death before pt was d/cd home and was

breathing w/o assistance Number of days w/o ventilator use from

D1-28 # of days w/o organ or system failure

and the occurrence of barotrauma Results

N= 861

ARDS NET

Lung Protective Strategy Low VT of 6cc/kg IBW in first 4h Plateau airway pressure of 30cmH20 Increased RR

Maintains adequate minute ventilation Permissive hypercapnea PEEP

Higher than you would think And decreased I:E ratio

1:1 to 1:3

CASE 2

32F with known asthma comes in in respiratory distress.

O/E: T= 36.6, P= 112, RR= 29, Sa02= 90%

Looks terrible, ++ accessory muscle use

You have tried aggressive bronchodilators, steroids, fluids, Mg but she is failing and needs airway management.

CASE 2 QUESTIONS Is there a role for NIPPV in asthma? How will you vent this patient?

VT PEEP FiO2 RR I:E

NIPPV and ASTHMA Well proven in AECOPD, so

theoretically should work in asthma No RCT, few small studies

2 very small prospective studies showed benefit

Cochrane concluded that it remains controversial despite some promising evidence

Ideal pt Moderate resp distress pH 7.25-7.35, PaCO2 45-55

IPPV and ASTHMA Goal: adequate oxygenation and

minimizing hyperinflation No RCT to guide mode and settings “Controlled hypoventilation” and

“permissive hypercapnia” with resultant acidosis Minute ventilation that maximizes E time but

provides enough ventilation to keep PaCO2 and pH reasonable

Reduces intrinsic PEEP and plateau pressures

Controlled hypoventilation and permissive hypercapnia

I TIME and E TIME in ASTHMA E time most nb determinant of

hyperinflation Maximize E time by shortening I time▪ Increasing the insp flow rate and using a

constant flow pattern Increase E time by reducing RR

CASE 3

24F with type I DM, in DKA, altered LOC, not protecting airway.

O/E: T= 38.1, P= 113, RR= 29, O2= 93%, BS= 34, BP= 110/60, GCS= 7

pH= 7.1

CASE 3 QUESTIONS

What mode of ventilation will you use?

What will your settings be? VT PEEP FiO2 RR I:E