Mechanical Ventilation in Adult Patients

Joshua R. Rosenberg M.D.

A July Guide to Ventilators

Disclosure I have no knowledge of stock in

pharmaceutical companies, medical device companies, or any company affiliated with the Medical Industry.

Any stock owned is through the Continuum retirement plan with Fidelity. It is rapidly loosing money.

I am not a paid speaker, lecturer, consultant for any company.

Brand name products will be discussed. Proprietary and copyrighted ventilator

modes will be discussed.

Ventilator Management Indications for Intubation

Classification of Respiratory Failure Modes of Ventilator Management Initial Ventilator Settings Daily Assessment of the Ventilated Patient and Weaning Trouble Shooting:

Increased Peak Pressures ETT Position Desaturation Cuff Leaks Self-Extubation Shock – Pneumothorax/Auto-PEEP Patient-Ventilator Dyssynchrony “Double-Triggering”

The Greatest Quotable Yankee

“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. “In theory there is no difference between theory and practice. In practice there is.” Hearing the information is nice but no substitute for gaining experience in ventilator management.

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

Keep the FiO2 Low PaO2 70-80

Keep the Tidal Volumes near 6 ml/kg IBW You don’t have to correct it all at once

Permit some hypercapnea initially to lower airway and lung pressures.

Ventilator Management:Stepwise

1. Recognize Respiratory Failure2. Stabilize on the Vent3. Figure out why?4. Talk with your nurse!5. Trouble Shooting

Initial assessment of common problems

6. Weaning

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

A minimally experienced clinician can tell when a patient is in trouble.

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

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

Abnormal Alveoli Pulmonary Edema

ARDS CHF Neurogenic Drug Induced

Pneumonia Alveolar Hemorrhage Atelectasis

Normal Alveoli Intra-cardiac Shunts

PFOVSD,ASD

Intrapulmonary ShuntsAVMHepato-Pulmonary

Syndrome

Rarely Acute Commonly Acute

Acute Ventilatory Failure

Increased Load Resistance

COPD, Asthma

Elastance ILD, Effusions

Minute Ventilation DKA, Sepsis

Airway Obstruction Foreign Body, laryngeal

fracture, airway deviation.

Decreased Strength Reduced Drive Impaired Transmission Muscle Weakness

Typical Initial Settings Common Modes: We pick one from each

Two timing Options: SIMV (Synchronized Intermittent Mechanical

Ventilation) A/C (Assist Control)

Three delivery Modes Volume Control (VC) Pressure Control (PC) VC+ or PRVC (depending on manufacturer)

Pressure Support (PS) Method of augmenting spontaneous patient

driven respirations only

Assist Control

Machine assists on every single breath

Assists on patient initiated breaths Assists on machine driven breaths Set Rate is the Minimum rate of

ventilation Can be combined with VC, PC, or VC+

SIMV

Machine assists for set number of breaths only.

Other breaths patient is on their own with or without pressure support.

For machine delivered breaths can be combined with VC, PC, or VC+

Spontaneous breaths – PS only!

Pressure Support Respiratory rate is completely patient

dependent Machine augments the patient’s breath by

at a flow rate which adjusts itself to the patient’s effort.

A relatively constant, preset airway pressure is sustained during inspiration.

This added flow is terminated when the patient exhales.

Can deliver high or low level support.

Volume Control

We set the Tidal volume (TV) delivered

We set the Respiratory Rate (RR) We set the Flow (V) We do not control Airway Pressures

Pressure Control

We set the airway pressure We set the Time of inspiration Ti

We do not have control of tidal volume

We must closely monitor to ensure adequate tidal volumes are achieved.

VC+ / PRVC Pressure Control Ventilation to a Specific

Volume Target We set target TV We set Ti Machine adjusts pressure needed to

achieve TV in set Ti. It uses the returned TV of recent past

breaths to constantly fine tune required pressure

Physiologically closest to normal breathing outside of Pressure Support.

PEEP

Positive End Expiratory Pressure Helps keep aveoli inflated High peep can help recruitment in

ARDS and has been shown to have no negative impact on mortality.

PEEP can affect blood pressure and contribute to hypotension.

Spontaneous Breathing

? TV

Inspiration Expiration

Spontaneous Breathing

Patient does ALL work of breathing TV depends entirely upon patient

effort and lung mechanics

Pressure Support Ventilation

? TV

Pressure Support Ventilation

Peak Pressure depends solely upon

the amount of Pressure Support

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. Back up rate comes with loud alarms only:

Not appropriate if fluctuating level of mental status. Limits Peak Pressures

Assist Control/Volume Control

Assist Control/Volume Control“Set” TV

Assist Control/Volume Control

Peak Pressure depends upon TV and lung mechanics

Essentials of Ventilator Graphics ©2000 RespiMedu

Assisted Mode(Volume-Targeted Ventilation)

Assisted Mode(Volume-Targeted Ventilation)

FlowFlow

PressurePressure

VolumeVolume

Time (sec)Time (sec)

(L/min)(L/min)

(cm H(cm H22O)O)

(ml)(ml)

Essentials of Ventilator Graphics ©2000 RespiMedu

Assisted Mode(Volume-Targeted Ventilation)

Assisted Mode(Volume-Targeted Ventilation)

FlowFlow

PressurePressure

VolumeVolume

Time (sec)Time (sec)

(L/min)(L/min)

(cm H(cm H22O)O)

(ml)(ml)

Assist Control/Volume Control Every Breath You Take

Machine assists on every breath. Patient does ONLY the work necessary to

“trigger” the vent. Diaphragm is used and exercised in respiratory

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

TV is always the “set” TV. Overall, a very good mode for resting the

patient.

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

Synchronized Intermittent Mandatory Ventilation (SIMV)

? TV“Set” TV

SIMV

Peak Pressure depends upon TV and lung mechanics

Essentials of Ventilator Graphics ©2000 RespiMedu

SIMV(Volume-Targeted Ventilation)

SIMV(Volume-Targeted Ventilation)

Time (sec)Time (sec)

FlowFlow

PressurePressure

VolumeVolume

(L/min)(L/min)

(cm H(cm H22O)O)

(ml)(ml)

Essentials of Ventilator Graphics ©2000 RespiMedu

SIMV(Volume-Targeted Ventilation)

SIMV(Volume-Targeted Ventilation)

Time (sec)Time (sec)

FlowFlow

PressurePressure

VolumeVolume

(L/min)(L/min)

(cm H(cm H22O)O)

(ml)(ml)

SIMV + Pressure Support

“Set” TV ? TV

SIMV Patient does ALL work of breathing on the

spontaneous breaths. Plus some work on the SIMV breaths.

Not frequently used in MICU as primary setting.

Frequently used by Surgeons for weaning. TV on the spontaneous breaths depends

entirely upon patient effort and lung mechanics.

Overall, not good for resting the patient.

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 VentilationSpecifically Set Inspiratory

Time

Reduced Expiratoy

Time

Pressure Control VentilationPeak Pressure

depends upon the amount of pressure

applied plus intrinsic pressure of the

patient.

Pt = Paw + PL +Pcw

Pressure Control Ventilation

Almost never used as initial setting: Reserved for refractory hypoxemia. MAY increase gas exchange. Limits Peak Pressure. Very useful in ARDS settings.

Pressure Control Ventilation

Prolonged Inspiratory Time results in Reduced Expiratory Time Potential for auto-PEEP

Requires constant monitoring as changes in patient status will dramatically affect tidal volumes.

As the patient improves it will be necessary to decrease the inspiratory pressure.

VC+ / PRVCPeak Pressure

depends upon the amount of pressure needed to achieve target tidal volume

in desired time.

Typical Initial Settings Mode: A/C assist control or VC+ RR: 12 -16

Higher if patient has acidosis Tidal Volumes

6 – 8 cc/kg Ideal body weight 6 cc/kg Ideal body weight strict if ARDS If VC+ Ti of approx 0.8- 1.25 seconds.

Oxygen If severe hypoxia FiO2 80-100% Titrate FIO2 to PaO2 of 70-80

Peep of 5 unless severely hypotensive.

Talk with your nurse! Sedation/Pain Control:

Versed (100 mg in 100cc) Start 1 mg/hr and

titrate to Richmond Agitation 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

What are Peak and Plateau Pressures?

Pressure

time

PIP:complianceresistancevolumeflowPEEP

PEEP

PEEP

PIP

Pplat

resistanceflow

compliancetidal volume

No active breathingTreats lung as single unit

end-inspiratoryalveolar pressure

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

Peak and Plateau Pressures

Avoid: Ppeak > 45 cm H2O

Pplateau > 30 cm H2O

Elevated peak pressures can cause barotrauma

Elevated plateau pressures rip holes in lung tissue.

Nilsestuen, Respir Care 2005; 50:202-232

Patient Ventilator Dyssynchrony

Measuring Auto-PEEP Retained air at end

of breath Another name for

breath stacking Apply an

“expiratory hold” Assess pressure

rise

Trouble Shooting

1. 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 Shooting

2. 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

A 77 year old woman is brought to the ER for respiratory distress and emergently intubated. The ICU team is called due to hypoxia, tachycardia, and elevated airway pressures. Physical exam reveals harsh sounds on the right side with greatly decreased sounds on the left side.

The most appropriate treatment is:A. Needle decompression of the right

sideB. Needle decompression of the left sideC. STAT Albuterol treatmentD. Urgent CXR

Trouble Shooting

3. Desaturation 100% FIO2, Suction/Bag Patient

4. Cuff Leak (Exhaled TV < Inhaled TV) Inflate Balloon, Replace ETT

5. Self-Extubatioin URGENT assessment, “Dr. Respiratory”

6. Shock Pneumothorax, Auto-PEEP

7. Trach Trouble You should be able to handle this….

Weaning - Daily Assessment Did we fix the initial problem???Did we fix the initial problem??? Is the patient hypoxic – PaO2/FIO2 > 200 Is the patient hemodynamically stable? Does the patient have a moderate to severe

metabolic or respiratory abnormality? Are we planning any major procedures today

outside of Tracheotomy? What is the RASS?

Modes of Weaning

Pressure Support SIMV T – Piece Further Questions

Has the patient failed multiple weaning attempts before

Does the patient have a tracheotomy?

Weaning Trials

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

Weaning Trials

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

Trials of trials…

Multiple studies have shown that PS trials with low pressure (5-8) performed once daily are equally effective as T – piece studies.

Some trials have shown SIMV weans take longer to get there - additional ventilator days.

The jury is still very much out.

What do We Do? Daily assessment to hold sedation

(Sedation Vacation). Daily assessment by respiratory therapy to

evaluate for weaning. If minute ventilation is < 13, patient is HD

stable and neurologically able to cough, we try. IF ETT ≤ 7.5, PS 8 for 40 minutes IF ETT ≥ 8, PS 5 for 40 minutes

Patient is watched at bedside for first 10 minutes for signs of distress.

ABG at 40 minutes.

Weaning Trial

Is RSBI (Rapid Shalow Breathing Index) - RR/TV is < 110 at end of 40 minutes?

Does the ABG shows no acute acidosis?

If yes to both, can extubate.

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

Keep the FiO2 Low PaO2 70-80

Keep the Tidal Volumes near 6 ml/kg IBW You don’t have to correct it all at once

Permit some hypercapnea initially to lower airway and lung pressures.

Who’s Watching the Patient?

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

Thank You

Feel free to pop by the ICU anytime!