Mechanical Ventilation

David Marcus, MD@EMIMDoc – EMIMDoc.org

Emergency Medicine/Internal Medicine/Medical Ethics, LIJ Medical CenterNassau University Medical Center – 1/272016

Goals

General principlesWhat to use when

Basic settings and modificationsMonitoring

Trouble Shooting

To vent or not to vent?

85 y/o M c CHF, rales on physical exam, breathing comfortably, O2 sat 90%

45 yr old F, morbidly obese c OSA in extreme respiratory distress

20 y/o F c h/o asthma, multiple intubations in the past, audible wheeze, RR 22

94 y/o F, minimally responsive c HR 32, BP 60/palp, RR 10, O2 sat 95% ORA

On two things the world stands

Ventilation Oxygenation

RRVt

FiO2V/Q

Types of mechanical ventilation

Uses of NIPPV• COPD: Fewer intubations, mortality benefit.

• CHF: Fewer intubations, mortality benefit

• PNA: May use for hypoxia. No clear evidence.

• Asthma: Impending respiratory failure. Unclear data.

• DNI

• OSA

• DSIOTHER…

Modes

CPAPWhen CO2 OK, but cannot oxygenate

BiPAP For CO2 help (+/- O2 problem)

To decrease CO2, increase deltaTo increase O2, increase i/ePAP

Running the Numbers

• Initial BiPAP setting: 10/5 cmH2O

• Max iPAP 20-25 cmH2O

• Max ePAP 10-15 cmH2O

• Start FiO2 at 1.0 and titrate • Back up rate 12-16 / min

Know This!

• Contraindications: – Cardiac arrest– MI – Apnea– Sufficiently impaired LOC– Copious secretions/emesis– Facial trauma/impaired AW

• Likely to fail in severe acidosis, ARDS

Invasive

Indications for Intubation

• Failure to maintain AW (loss of reflexes)• Failure to maintain AW tone• Failure to ventilate• Failure to oxygenate• Clinical course expected to result in any of

the above

Contraindications

Loss of upper AW anatomyTotal upper AW obstruction

Relative contraindication:Anticipated difficult AW

Vents• Control mechanisms

1. VCV (fixed volume) 2. PCV (fixed pressure)

• Variables:– Trigger (what starts a breath): flow, pressure,

time– Limit: Pressure, Flow– Cycle (what ends a breath): Time, flow,

Pressure, Volume

Modes1. CMV – Machine breaths only

2. AC – fixed number of machine breaths + pt triggered breaths at fixed volume.

3. SIMV – fixed rate/volume machine breaths + pt triggered breaths limited by pt effort

4. May use pressure support (PSV) in SIMV or CPAP – provides additional support during spontaneous inspiration (to overcome resistance of system).

Other modes• APRV (airway pressure release ventilation)

• PAV (proportional assist ventilation)

• Prone positioning

• IRV (inverse ratio ventilation)

• Permissive hypercapnia (goal = decreased peak AW pressure, i.e. in asthmatics) Via lower RR, lower Vt.

Settings

RateFiO2

VtPEEP (Pressures)

i:e ratio

PEEP

– Uses– Risks

• Decreased venous return• Barotrauma• Increased ICP• GI Ulceration• Fluid retention (increased ADH vs decreased ANP)

PEEP

Benefits• Improved V/Q Matching• Decreased Shunt• Decreased atelectasis• Decreased alveolar trauma• Supported spontaneous breathing

Doctor, what settings would you like?

• Mode• Rate (12-14)• FiO2 (Start at 1.0 and titrate down)• PEEP (~5 cmH2O)• Vt (6-8 ml/kg)• (I:E ratio)

Patient Specific Management• 56 yr old M, traumatic PTX/rib fractures

• 28 yr old obese F, severe influenza, ARDS

• 76 year old M, subarachnoid hemorrhage

• 18 yr old F, severe asthma, now intubated

• 82 yr old M, septic shock

Monitoring

• Clinical Observation• Pulse Oximetry• ABG/VBG• Capnometry (End Tidal CO2)• BMP• Peak and Plateau pressures, Auto-PEEP• Volumes/Air Leak

Alarms!Don’t Ignore Alarms!

You’re Doing Great!

• Your intubated patient is doing well. • Sats are good, he appears comfortable.

• And then…

Alarms!Don’t Ignore Alarms!

Don’t Worry – It’s All DOPE(s)

Why is the patient is hypoxic? • D – Dislodged Tube/Disconnect • O – Obstructed system• P - Pneumothorax• E – Equipment Failure• (S – Stacked breaths, if asthmatic)

Don’t Worry – It’s All DOPE(s)

DOPES

Check connections, confirm tube placement via ETCO2 (+/- direct visualization)

Check all tubing, suction deep into ETT

Ultrasound or CXR to r/o pneumothorax

Disconnect the vent and attach a BVM

In asthmatics, disconnect the vent and listen

Though, it’s more like SEDOP

• First, disconnect the vent,• then switch to a BVM.• Confirm tube placement,• Suction, check for obstructions• Verify and reconnect tubing• Check for PTX (depending on suspicion)

When to come off the vent?

• As soon as possible• Two questions:

– Can the pt protect the AW?– Can the pt oxygenate and ventilate?

Decision toolsRSBI = RR/Vt(Liters)

RSBI>105 = poor prognosis for weaning (PPV 65%, NPV 95%)

First --- oxygenating well on low FiO2 and low PEEP

Also: • Determine cause of ventilatory dependance• Rectify correctible problems • Address:

– Fluid balance– Mental status and psychological factors– Acid-base status– Electrolyte disturbance

Weaning Methods

• T tube trial• IMV• PSV• NPPV

Vent complications

• PTX• Biotrauma (the injury formerly known as

barotrauma): overdistention or rupture, alveolar hypoperfusion, and repetitive shear stresses across alveolar walls

• Hemodynamic compromise• VAP

Summary

• What’s the patient’s problem? – CO2/O2/AW

• NIPPV– Know settings, contraindications!

• IPPV– Modes, General vent settings– DOPE(s)

• Further reading: Vent strategies for restrictive vs obstructive lung disease

Summary

• 45 yr old F, morbidly obese c OSA in extreme respiratory distress?– NIPPV?– IPPV?– No mechanical ventilation?

NIPPV may be used in all of the following, except:

1. COPD2. CHF3. CPR4. Pneumonia5. Asthma6. Myesthenia gravis

The most appropriate Mode/Vt for a sedated, ventilated patient with normal

lungs:

1. CMV/6-8 ml/kg TBW

2. CMV/6-8 ml/kg IBW

3. AC/10-15 ml/kg TBW

4. AC/6-8 ml/kg IBW

THANK YOU!

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