ventilation strategies
DESCRIPTION
Alyssa Morris, R4 July 15, 2010 Thanks to Dr J Lord. VENTILATION STRATEGIES. OBJECTIVES. Indications for ventilation Ventilation terminology Ventilation modes NIPPV IPPV* Cases ARDS Metabolic acidosis Asthma SCM order sets . INDICATIONS. Rosen’s Chapter 1 - PowerPoint PPT PresentationTRANSCRIPT
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