2007 july lecture series mechanical ventilation
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2007 July Lecture Series “Mechanical Ventilation”. A July Intern’s Guide to Ventilators. Kevin P Simpson, MD. Ventilator Management. Indications for Intubation Classification of Respiratory Failure Initial Ventilator Settings ….and other orders! Daily Assessment of the Ventilated Patient

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2007 July Lecture Series “Mechanical Ventilation”

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2007 july lecture series mechanical ventilation

2007 July Lecture Series“Mechanical Ventilation”

A July Intern’s Guide to Ventilators

Kevin P Simpson, MD


Ventilator management

Ventilator Management

  • Indications for Intubation

    • Classification of Respiratory Failure

  • Initial Ventilator Settings

    • ….and other orders!

  • Daily Assessment of the Ventilated Patient

  • Trouble Shooting:

    • Increased Peak Pressures

    • ETT Position

    • Desaturation

    • Cuff Leaks

    • Self-Extubation

    • Shock – Pneumothorax/Auto-PEEP

    • Patient-Ventilator Dyssynchrony

    • “Double-Triggering”

    • Trach Trouble

  • Weaning

  • Specifics of ARDS and Asthma; Permissive Hypercapnea


Ventilator management stepwise

Ventilator Management:Stepwise

  • Recognize Respiratory Failure

  • Stabilize on the Vent

  • Talk with your nurse!

  • Figure out why?

  • Daily Routine

    • Sound like a doc on rounds.

  • Trouble Shooting

    • That’s what interns do

  • Weaning


Indications for intubation

Indications for Intubation

  • “VOPS” vs “The Look”

    • Ventilation

    • Oxygenation

    • Airway Protection

    • Secretions

  • No single “level” of any vital sign, physical exam finding, or lab value is an indication for intubation


Why did this happen classification of respiratory failure

Type I: Acute Hypoxemic Respiratory Failure

Severe Hypoxia

Refractory to Supplemental Oxygen

Type II: Acute Ventilatory Failure

Imbalance between Load and Strength

Why did this happen?Classification of Respiratory Failure


I acute hypoxemic respiratory failure ahrf etiologies

I. Acute Hypoxemic Respiratory Failure (AHRF)….Etiologies

  • Normal Alveoli

    • Intra-cardiac Shunts

      • PFO

      • VSD,ASD

    • Intrapulmonary Shunts

      • AVM

      • Hepato-Pulmonary Syndrome

  • Abnormal Alveoli

    • Pulmonary Edema

      • High Pressure

        • CHF

      • Low Pressure

        • ARDS

      • Mixed

        • ? Neurogenic

    • Pneumonia

    • Alveolar Hemorrhage

    • Atelectasis

Rarely Acute

Commonly Acute


Ii acute ventilatory failure

II. Acute Ventilatory Failure

Strength

Load


Acute ventilatory failure

Increased Load

Resistance

COPD, Asthma

Elastance

ILD, Effusions

Minute Ventilation

DKA, Sepsis

Decreased Strength

Reduced Drive

Impaired Transmission

Muscle Weakness

Acute Ventilatory Failure


If you don t know where you are going you might wind up someplace else

“If you don't know where you are going, you might wind up someplace else.”

  • Try to figure out ‘why’ the patient is requiring intubation.


Typical initial settings

Typical Initial Settings

  • Mode:

    • Goal = “REST”

    • Four Options:

      • SIMV

      • A/C

      • Pressure Support

      • Pressure Control


Spontaneous breathing

Spontaneous Breathing

? TV

Inspiration Expiration


Spontaneous breathing1

Spontaneous Breathing

  • Patient does ALL work of breathing

  • TV depends entirely upon patient effort and lung mechanics


Synchronized intermittent mandatory ventilation simv

Synchronized Intermittent Mandatory Ventilation (SIMV)

“Set” TV

? TV


2007 july lecture series mechanical ventilation

SIMV

Peak Pressure depends upon TV and lung mechanics


2007 july lecture series mechanical ventilation

SIMV

  • Patient does ALL work of breathing on the spontaneous breaths.

    • Plus some work on the SIMV breaths.

  • TV on the spontaneous breaths depends entirely upon patient effort and lung mechanics.

  • Overall, not good for resting the patient.


Assist control volume control

Assist Control/Volume Control


Assist control volume control1

Assist Control/Volume Control

“Set” TV


Assist control volume control2

Assist Control/Volume Control

Peak Pressure depends upon TV and lung mechanics


Assist control volume control3

Assist Control/Volume Control

  • Patient does ONLY the work necessary to “trigger” the vent.

    • Typically, minimal (i.e., 2 cm H2O)

  • TV is always the “set” TV.

  • Overall, a very good mode for resting the patient.


Pressure support ventilation

Pressure Support Ventilation

? TV


Pressure support ventilation1

Pressure Support Ventilation

Peak Pressure depends solely upon the amount of Pressure Support


Pressure support ventilation2

Pressure Support Ventilation

  • Patient does a VARIABLE amount of work of breathing:

    • If “adequate” pressure, work is limited to simply that required to trigger.

  • TV depends upon the combination of patient effort/lung mechanics AND the amount of pressure applied.

    • Overall, CAN achieve rest if administer enough pressure.

  • NO back up rate:

    • Not appropriate if fluctuating level of mental status.

  • Limits Peak Pressures


Simv pressure support

SIMV + Pressure Support

“Set” TV

? TV


Simv pressure support1

SIMV + Pressure Support

  • If “adequate” pressure support, work of breathing is minimal.

    • Only that necessary to trigger the vent.

  • If “inadequate” pressure support, work of breathing is similar to SIMV alone.

    • PS = 5 cm H2O is almost always inadequate


Pressure control ventilation

Pressure Control Ventilation

Specifically Set Inspiratory Time

Reduced Expiratoy Time


Pressure control ventilation1

Pressure Control Ventilation

Peak Pressure depends solely upon the amount of pressure applied.


Pressure control ventilation2

Pressure Control Ventilation

  • Almost never used as initial setting:

    • Reserved for refractory hypoxemia.

    • MAY increase gas exchange.

    • Limits Peak Pressure.

  • Prolonged Inspiratory Time results in Reduced Expiratory Time

    • Potential for auto-PEEP


Typical initial settings1

Typical Initial Settings

  • Mode: Desire “Rest”

    • Either:

      • A/C or SIMV with “adequate” PS


Typical initial settings2

Typical Initial Settings

  • Mode: A/C


Typical initial settings3

Typical Initial Settings

  • Mode: assist control

  • RR: 12 -16


Typical initial settings4

Typical Initial Settings

  • Mode: assist control

  • RR: 12 -16

  • Tidal Volume:

    • 7-8 cc/kg if “normal” lungs

    • 7-8 cc/kg if typical med-surg patients

    • 6 (or less) cc/kg if ARDS

    • ? Which weight – predicted body weight


Typical initial settings5

Typical Initial Settings

  • Mode: assist control

  • RR: 12 -16

  • Tidal Volume: 500 cc


Typical initial settings6

Typical Initial Settings

  • Mode: assist control

  • RR: 12 -16

  • Tidal Volume: 500 cc

  • FIO2:

    • 100% to start

    • Avoid O2 Toxicity

    • Titrate by pulse oximeter (> 92%)


Typical initial settings7

Typical Initial Settings

  • Mode: assist control

  • RR: 12 -16

  • Tidal Volume: 500 cc

  • FIO2: 100%

  • PEEP:

    • Typically start with 5 cm H2O

      • Increase if needed to reach non-toxic FIO2

    • How much PEEP?


Typical initial settings8

Typical Initial Settings

  • Mode: assist control

  • RR: 12 -16

  • Tidal Volume: 500 cc

  • FIO2: 100%

  • PEEP: 5 cm H2O

  • Goal is to “REST” the patient

    • No distress

      • Don’t forget about sedation


Talk with your nurse

Sedation/Pain Control:

Midazolam

(100 mg in 100cc)

Start 1 mg/hr and titrate to sedation score = 0

Fentanyl

(2500 mcg/50cc)

Start 1 mcg/kg/hr and titrate to relief of pain

CXR

immediate and daily

Restraints

Dobhoff

CNU consult for TF’s

Change meds to suspension or IV

Titrate FIO2 to maintain SpO2 > 92%

? ABG ?

? MDI’s

NOTIFY FAMILY

Talk with your nurse!


Daily assessment

Presentation Style:

Hx:

Since yesterday…

Overnight…

Presently…

Vitals

Exam

Ventilator Settings:

Mode/Rate/Volume…

FIO2/PEEP

(PS)

On these…

Total RR ____

Peak/Plateau__ /__

Raw____

Compliance____

ABG:

pH/pCO2…/pO2/Sat

Daily Assessment


What are peak and plateau pressures

What are Peak and Plateau Pressures?


2007 july lecture series mechanical ventilation

PIP:complianceresistancevolumeflow

PEEP

Pressure

PEEP

time


2007 july lecture series mechanical ventilation

No active breathing

Treats lung as single unit

PIP

resistance

flow

Pplat

end-inspiratory

alveolar pressure

compliance

tidal volume

PEEP


Airways resistance and compliance but you said there would be no math

Airways Resistance and ComplianceBut you said there would be no math….

  • Raw:

    • [Peak – Plateau]/Flow Rate

      • Flow Rate is in L/sec and is typically ~1 L/s

    • Normal < 10 (cm H2O/L per sec)

  • Static Compliance:

    • TV (cc)/ [plateau – PEEP]

    • Normal > 60 mL/cm H2O

    • Awful! < 20


Peak and plateau pressures pattern recognition

Peak and Plateau Pressures:Pattern Recognition

  •  Ppeak with a Normal Pplateau

    = Increased Raw

    • ETT trouble, Bronchospasm

    • Give Bronchodilators

  •  Ppeak with a  Pplateau

    = Decreased Compliance

    • ARDS, IPF, Pneumothorax, Effusions, …

    • Check a CXR


  • Prima non nocere peak and plateau pressures

    Avoid:

    Ppeak> 45 cm H2O

    Pplateau> 32 cm H2O

    Prima non nocere…Peak and Plateau Pressures


    Flow rates

    Flow Rates

    • “Normal” ~ 1 L/sec or 60 L/min

      • “Abnormal” Flow Rates

        • May be uncomfortable and increase WOB

        • May induce tachypnea, double-triggering, auto-PEEP, ALARMS!

    • May be adjusted directly or indirectly

      • By changing the flow profile


    2007 july lecture series mechanical ventilation

    PRESSUREALARM

    80

    Pao

    .

    V

    x

    Ti

    Te

    Ti

    Te

    TIME

    Choose Your Poison Pressure:

    Peak or auto-PEEP


    Flow rates1

    Flow Rates

    • Consider adjusting when:

      • Elevated Peak Pressures

      • Unexplained tachypnea

      • Patient discomfort

      • Auto-PEEP

    • Increasing Flow Rate:

      • Reduces auto-PEEP but increases peak pressures

    • Decreasing Flow Rate:

      • Reduces peak pressures but increases auto-PEEP


    Patient ventilator dyssynchrony

    Patient Ventilator Dyssynchrony

    Nilsestuen, Respir Care 2005; 50:202-232


    Airway pressure waveforms

    Airway Pressure Waveforms

    • “During true relaxed/passive inflation, the airway pressure tracing shows a smooth rise, it remains convex upward, and it is highly reproducible from breath to breath.”

    • “In a patient who is receiving partial (‘inadequate’) ventilator support, the degree of deformation and scooping of the airway pressure provides a means of monitoring the amount of effort expended by the patient.”

      Charles Alex, MD…..Loyola


    Auto peep

    Auto-PEEP


    Measuring auto peep

    Measuring Auto-PEEP

    • Apply an “expiratory hold”

    • Assess pressure rise


    Trouble shooting

    Trouble Shooting

    • Increased Peak Pressures:

      • Look at the patient

        • Distress, biting the ETT?

      • Pass suction catheter through ETT

        • Biting the ETT, crusted ETT?

      • Check Peak/Plateau Pressures

        • Primarily increased Raw ….. Bronchodilators

        • Primarily decreased compliance….check CXR

      • Consider Lower TV, Lower Flow Rate, Sedation


    Trouble shooting1

    Trouble Shooting

    • ETT Position:

      • What’s correct:

        • Below the larynx

        • At least 2 cm above the carina

      • How do you know?

        • “corner of the mouth”

          • Average 22 cm in women, and 23 cm in men

        • CXR position

          • ? Variation with head position


    Trouble shooting2

    Trouble Shooting

    • Desaturation

      • 100% FIO2, Suction/Bag Patient

    • Cuff Leak (Exhaled TV < Inhaled TV)

      • Inflate Balloon, Replace ETT

    • Self-Extubatioin

      • URGENT assessment, “Dr. Respiratory”

    • Shock

      • Pneumothorax, Auto-PEEP

    • Trach Trouble

      • ENT (Don’t replace yourself if a fresh trach)


    Weaning

    “Weaning”

    • Daily Assessment


    Weaning1

    “Weaning”

    • Daily Assessment

    • Weaning Parameters

      • RSBI

        • RR/TVL < 100 predicts success

      • NIF (or MIP)

        • Less negative than -20 cm H2O predicts failure


    Weaning2

    “Weaning”

    • Daily Assessment

    • Weaning Parameters

      • RSBI

      • NIF

    • T-Piece Trial

      • Pressure Support possibly equivalent

      • SIMV delays extubation


    Weaning trials

    Weaning Trials

    Tobin et al, NEJM 1995;332:345-350


    Weaning trials1

    Weaning Trials

    Tobin et al, NEJM 1995;332:345-350


    Weaning3

    “Weaning”

    • Daily Assessment

    • Weaning Parameters

      • RSBI

      • NIF

    • T-Piece Trial

    • Trial of Extubation


    General rules of mechanical ventilation

    General “Rules” of Mechanical Ventilation

    • Indications for Intubation….

      • “The Look”

    • “Rest”…

      • Get rid of “The Look”

    • Keep the Pressures Low…

      • Peak < 45 cm H2O

      • Plateau < 32 cm H2O

    • Forget the PaCO2….

      • “Permissive Hypercapnea”


    Who s watching the patient

    Who’s Watching the Patient?

    Pierson, IN: Tobin, Principles and Practice of Critical Care Monitoring


    General rules of mechanical ventilation1

    General “Rules” of Mechanical Ventilation

    “Make the Beeping Stop”


    Status asthmaticus

    Status Asthmaticus

    • Maximize Medical Therapy

      • Nebulized Albuterol

      • Nebulized Ipratropium Bromide

      • IV Steroids

      • IV Magnesium

      • NOT:

        • CPT

        • Acetylcysteine

        • Antibiotics – unless infection


    Status asthmaticus1

    Status Asthmaticus

    • Heliox

      • Decreased WOB

      • Unclear Role

    • Ventilator Strategy

      • High Inspiratory Flow Rate

        • 80-100L/min

        • Accept High Peak Pressures

        • Increase Expiratory Time

          • Reduces auto-PEEP

    • Try to avoid neuromuscular blockade

      • Risk of prolonged weakness


    Permissive hypercapnea

    “Permissive Hypercapnea”

    • Accept Hypercapnea

      • Rather than impose high pressures

        • Minimizes risk of barotrauma

        • Reduces ventilator-induced lung injury

    • ? Bicarbonate Drip

      • If pH unacceptably low

        • ? “permissive acidosis”


    Ards definition

    ARDS…Definition

    • Severe Hypoxemia

      • P/F ratio < 200

    • Diffuse CXR Lesion

      • 3 of 4 quadrants

    • Normal Pcwp

      • “no CHF”

    • ’d Compliance


    Ards treatment of hypoxia

    ARDS…Treatment of Hypoxia

    • Treat the Underlying Cause

    • Supplemental O2

    • Diuresis

    • PEEP

    • Optimize the Mixed Venous O2

    • Prone Positioning


    Treat the underlying cause

    Pneumonia

    Sepsis

    Aspiration

    Trauma

    Multiple Transfusions

    Pancreatitis

    Inhalational Injury

    Treat the Underlying Cause

    1/3 No Identifiable Cause


    Supplemental o 2

    Supplemental O2

    • Mainly Shunt

      • therefore poor response to O2

    • ? O2 Toxicity

      • Only use “toxic” FiO2 if significant improvement on PaO2


    Supplemental o 21

    Supplemental O2

    • Mainly Shunt

      • therefore poor response to O2

    • ? O2 Toxicity

      • Only use “toxic” FiO2 if significant improvement on PaO2

    O2

    Hgb

    PmvO2 = 40 mmHg

    PaO2 = 40 mmHg


    Decrease drive to edema formation

    Decrease Drive to Edema Formation


    Decrease drive to edema formation1

    Decrease Drive to Edema Formation


    Decrease drive to edema formation2

    Decrease Drive to Edema Formation


    2007 july lecture series mechanical ventilation

    Good….

    Recruits Alveoli

    Redistributes Pulmonary Edema Fluid

     PaO2

    Bad….

    ’d Venous Return / C.O.

    ’s Risk of Barotrauma

    PEEP

    How Much PEEP?

    (more later)


    2007 july lecture series mechanical ventilation

    Effect of PEEP on

    Distribution of Lung Water

    PEEP 3

    PEEP 13

    Malo et al, J Appl Physiol 1984;57:1002


    2007 july lecture series mechanical ventilation

    Chest 1989;96:449


    2007 july lecture series mechanical ventilation

    Withdrawal of PEEP:

    Three Minute PEEP Trial

    *

    5 cm H2O

    *

    PEEP

    3 min

    Time

    * ABG sample


    Optimize the mixed venous o 2

     O2 Consumption

    Treat Fever

    Decrease WOB

    Sedation

    Analgesia

    Muscle Relaxation

     O2 Delivery

    DaO2 = CO X CaO2

    CaO2 = 1.39 X Hgb X Sat

    +

    0.0031 X PaO2

    Optimize the Mixed Venous O2


    2007 july lecture series mechanical ventilation

    Prone Positioning


    Effect of prone positioning on pao 2

    Effect of Prone Positioning on PaO2

    Gattinoni L, et al. NEJM 2001;345:568-73.


    Ards treatment

    ARDS…Treatment

    • Treat the Underlying Cause

    • Supplemental O2

    • Diuresis

    • PEEP

    • Improve Mixed Venous O2

    • Prone Positioning


    Acute ventilatory failure1

    Acute Ventilatory Failure


    Acute ventilatory failure2

    Acute Ventilatory Failure

    Load

    Strength


    Acute ventilatory failure3

    Acute Ventilatory Failure

    • Manifested by:

      • Hypercapnea or

      • Eucapnea with Increased MV Requirements or

      • Increased “Work of Breathing”

    • PaCO2 = (VCO2 x k)/VA

      • VA =MV (1 – VD/VT)

    • Therefore, Hypercapnea requires:

      •  VCO2(extremely rare)

      •  MV(easily recognized)

      •  VD/VT(don’t forget!)


    Acute ventilatory failure v d v t

    Acute Ventilatory Failure: VD/VT

    • Dead Space:

      • Ventilated but Non-Perfused Alveolar Units

    • Anatomic Dead Space

      • Averages 1 cc/kg (or 30% of a typical TV)

    • Physiologic Dead Space:

      •  Zone 1

        •  Pulmonary Perfusion (i.e., volume depletion)

        •  Alveolar Pressures (i.e., PEEP)

      • Pulmonary Vascular Disease

        • Pulmonary Hypertension

        • Pulmonary Embolism


    Acute ventilatory failure4

    Increased Load

    Resistance

    COPD, Asthma

    Elastance

    ILD, Effusions

    Minute Ventilation

    DKA, Sepsis

    Decreased Strength

    Reduced Drive

    Impaired Transmission

    Muscle Weakness

    Acute Ventilatory Failure


    Acute ventilatory failure neuromuscular disease

    Acute Ventilatory Failure:Neuromuscular Disease

    • Vital Capacity

      • ? Intubate when < 15 cc/kg (~1 liter)

    • Spinal Cord Injury

      • C3-C5

    • Phrenic Nerve Injury

      • Post-Cardiac Surgery, Traumatic, Post-Lung Transplant

      • Unilateral, rarely problematic

      • Severe Orthopnea, Thoraco-Abdominal Paradox


    Acute ventilatory failure treatment

    Acute Ventilatory Failure: Treatment

    • Underlying Cause

    • Oxygen

      • May increase PaCO2

        • NOT by “Blunting Drive to Breath”

        • Promotes VQ Mismatch and Dead Space

    • Assisted Ventilation

      • Nasal CPAP / BiPAP

      • Intubation


    Cpap bipap indications

    CPAP/BiPAP Indications

    • Acute Pulmonary Edema

    • “Severe” COPD Exacerbations

    • Acute Respiratory Failure in the Immunosuppressed

    • To Facilitate Early Extubation in COPD

      • Note: NOT for extubation failures

    HOWEVER

    DO NOT DELAY INTUBATION

    IF INDICATED!!!


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