MECHANICAL VENTILATION

Seyed Alireza Mahdavi

Ventilator settings

Ventilator settings

1. Ventilator mode

2. Respiratory rate

3. Tidal volume or pressure settings

4. Inspiratory flow

5. I:E ratio

6. PEEP

7. FiO2

8. Inspiratory trigger

CMV

A/CV

SIMV

SpontaneousBreathing

Mechanical Ventilation

Pre

ssur

eP

ress

ure

Pre

ssur

eP

ress

ure

Pre

ssur

e

Time

Time

Time

Time

Time

CMV

SIMV

Bivent

APRV

CPAP

Concepts and Modes of Mechanical Ventilation

Positive End-expiratory Pressure (PEEP)

What is PEEP?

What is the goal of PEEP?

Improve oxygenation

Diminish the work of breathing

Different potential effects

PEEP

What are the secondary effects of PEEP? Barotrauma Diminish cardiac output

Regional hypoperfusion NaCl retention Augmentation of I.C.P.? Paradoxal hypoxemia

Monitoring of the patient

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 than the FRC

Auto-PEEP or Intrinsic PEEP

Why does hyperinflation occur?

Airflow limitation because of dynamic collapse

No time to expire all the lung volume (high RR or Vt)

Expiratory muscle activityLesions that increase expiratory resistance

Auto-PEEP or Intrinsic PEEP

Auto-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 PEEP

Adverse effects:

Predisposes to barotrauma Predisposes hemodynamic compromises Diminishes the efficiency of the force

generated by respiratory muscles Augments the work of breathing Augments the effort to trigger the ventilator

Different types of patient

COPD and Asthma

Goals:

Diminish dynamic hyperinflationDiminish work of breathingControlled hypoventilation

(permissive hypercapnia)

Diminish DHI

Why?

Diminish DHI

How?Diminish minute ventilation

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

Diminish work of breathing

How: Add PEEP (about 85% of PEEPi)

Applicable in COPD and Asthma.

Controlled hypercapnia

Why?

Limit high airway pressures and thus diminish the risk of complications

Controlled hypercapnia

How?

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

Controlled hypercapnia

CI:Head pathologiesSevere HTNSevere metabolic acidosisHypovolemiaSevere refractory hypoxiaSevere pulmonary HTNCoronary disease

Restrictive Pattern

Intrapulmonary:

Intra-alveolar filling processes

Alterations in lung interstitium

Extrapulmonary

Pleural disease

Chest wall abnormalities

Neuromuscular disease

Management of Mechanical Ventilation

Volume

Pressure

I:E ratio

Mode

Thank You