MECHANICAL VENTILATIONMarc Charles Parent

PresentationDifferent settings to considerMonitoring of the patientDifferent type of patient

COPD, AsthmaARDSTrouble shooting

Ventilator settings

Ventilator settingsVentilator modeRespiratory rateTidal volume or pressure settingsInspiratory flowI:E ratioPEEPFiO2Inspiratory trigger

CMV

A/CV

SIMV

PSV(pressure support ventilation)

Spontaneous inspiratory efforts trigger the ventilator to provide a variable flow of gas in order to attain a preset airway pressure.Can be used in adjunct with SIMV.

Respiratory Rate

What is the pt actual rate demand?

Tidal Volume or Pressure setting Maximum volume/pressure to achieve good ventilation and oxygenation without producing alveolar overdistention

Max cc/kg? = 10 cc/kg

Some clinical exceptions

Inspiratory flowVaries with the Vt, I:E and RR

Normally about 60 l/min

Can be majored to 100- 120 l/min

I:E Ratio

1:2

Prolonged at 1:3, 1:4,

Inverse ratio

FIO2The usual goal is to use the minimum Fio2 required to have a PaO2 > 60mmhg or a sat >90%

Start at 100%

Oxygen toxicity normally with Fio2 >40%

Inspiratory TriggerNormally set automatically

2 modes:

Airway pressureFlow triggering

Positive End-expiratory Pressure (PEEP) What is PEEP?

What is the goal of PEEP?

Improve oxygenation

Diminish the work of breathing

Different potential effects

PEEPWhat are the secondary effects of PEEP?

BarotraumaDiminish cardiac output

Regional hypoperfusionNaCl retentionAugmentation of I.C.P.?Paradoxal hypoxemia

PEEPContraindication:

No absolute CI

BarotraumaAirway traumaHemodynamic instabilityI.C.P.?Bronchospasm?

PEEPWhat PEEP do you want?

Usually, 5-10 cmH2O

Monitoring of the patient

Look at your patientQuestion your pt

Examine your pt

Monitor your pt

Look at the synchronicity of your pt breathing

Pressures

Compliance pressure (Pplat)Represent the static end inspiratory recoil pressure of the respiratory system, lung and chest wall respectively

Measures the static compliance or elastance

PplatMeasured by occluding the ventilator 3-5 sec at the end of inspirationShould not exceed 30 cmH2O

Peak Pressure (Ppeak)Ppeak = Pplat + Pres

Where Pres reflects the resistive element of the respiratory system (ET tube and airway)

PpeakPressure measured at the end of inspiration

Should not exceed 50cmH2O?

Auto-PEEP or Intrinsic PEEP What is Auto-PEEP?

Normally, at end expiration, the lung volume is equal to the FRC

When PEEPi occurs, the lung volume at end expiration is greater then the FRC

Auto-PEEP or Intrinsic PEEPWhy does hyperinflation occur?

Airflow limitation because of dynamic collapseNo time to expire all the lung volume (high RR or Vt)Expiratory muscle activityLesions that increase expiratory resistance

Auto-PEEP or Intrinsic PEEPAuto-PEEP is measured in a relaxed pt with an end-expiratory hold maneuver on a mechanical ventilator immediately before the onset of the next breath

Auto-PEEP or Intrinsic PEEPAdverse effects:

Predisposes to barotraumaPredisposes hemodynamic compromisesDiminishes the efficiency of the force generated by respiratory musclesAugments the work of breathingAugments the effort to trigger the ventilator

Different types of patient

COPD and AsthmaGoals:

Diminish dynamic hyperinflationDiminish work of breathingControlled hypoventilation (permissive hypercapnia)

Diminish DHIWhy?

Diminish DHIHow?

Diminish minute ventilation

Low Vt (6-8 cc/kg)Low RR (8-10 b/min)Maximize expiratory time

Diminish work of breathingHow:

Add PEEP (about 85% of PEEPi)

Applicable in COPD and Asthma.

Controlled hypercapniaWhy?

Limit high airway pressures and thus diminish the risk of complications

Controlled hypercapniaHow?

Control the ventilation to keep adequate pressures up to a PH > 7.20 and/or a PaCO2 of 80 mmHg

Controlled hypercapniaCI:

Head pathologiesSevere HTNSevere metabolic acidosisHypovolemiaSevere refractory hypoxiaSevere pulmonary HTNCoronary disease

A.R.D.S.Ventilation with lower tidal volume as compared with traditional volumes for acute lung injury and the ARDS

The Acute Respiratory Distress Syndrome Network

N Engl J Med 2000;342:1301-08

MethodsMarch 96 March 9910 university centersInclusion:

Diminish PaO2Bilateral infiltrateWedge < 18ExclusionRandomized

MethodsA/C 28d or weaning2 groups:

1. Traditional Vt (12cc/kg)2. Low Vt (6cc/kg)

End point:

1. Death2. Days of spontaneous breathing3. Days without organ failure or barotrauma

ResultsThe trails were stopped after 861 pt because of lower mortality in low Vt group

Trouble Shooting

Trouble ShootingDoctor, doctor, his pressures are going up!!!

What is your next step?

Trouble ShootingCall the I.T., he will take care of it!Where is the staff?I dont know this pt, and run!Ask which pressure is going up

Trouble ShootingPpeak is up

Look at your Pplat

Trouble ShootingIf your Pplat is high, you are faced with a COMPLIANCE problem

If your Pplat is N, you are faced with a RESISTIVE problem

DD?

Trouble Shooting

Trouble ShootingDoctor, doctor, my patient is very agitated!

What is your next step?

Trouble ShootingGive an ativan to the nurse!Give haldol 10mg to the patient!Take 5mg of morphine for yourself!Look at your pt!

Trouble ShootingAt the time of intubation, fighting is largely due to anxiety

But what do you do if pt is stable and then becomes agitated?

Trouble ShootingRemove pt from ventilatorInitiate manual ventilationPerform P/E and assess monitoring indicesCheck patency of airwayIf death is imminent, consider and treat most likely causesOnce pt is stabilized, undertake more detailed assessement and management

Trouble Shooting

Conclusion

Feuil1

Type of patientTidal VolumeRRPEEPFIO2Ins. FlowI:ENoteNote

Normal10 cc/kg10 to 120 to 5100%.60 l/min1:2.

ARDS6 cc/kg10 to 125 to 15100%.60 l/min1:2.

COPD6 cc/kg10 to 125 to 10100%.100 to 1201:3 to 1:4PH>7.2

PCO2