1. Mechanical Ventilation 1

2. Copyright 2008 Society of Critical Care Medicine
Objectives
Discuss indications and techniques for noninvasive positive pressure ventilation (NPPV)
Describe types of breaths and modes of mechanical ventilation
Outline settings and monitoring for initiation of mechanical ventilation
Copyright 2008 Society of Critical Care Medicine

3. Copyright 2008 Society of Critical Care Medicine
Case Study
65-year-old with an exacerbation of COPD
Using accessory muscles and wheezing after 2 bronchodilator treatments
HR 110 beats/min, BP 160/110 mm Hg, RR 30 breaths/min, T 99F(37.2C)
ABG on 3 L/min O2: pH 7.24, PCO2 60 mm Hg (8 kPa), PO2 65 mm Hg (8.7 kPa)
Present case and then reveal question.
Ask what is the main problem-- oxygenation or ventilation.
As students respond, note that positive pressure ventilation may be noninvasive or invasive. Note that noninvasive ventilation may be an appropriate trial for this patient.
What type of respiratory support should
be initiated?
Copyright 2008 Society of Critical Care Medicine

4. Copyright 2008 Society of Critical Care Medicine
Candidates for NPPV
Respiratory condition expected to improve in hours
Alert, cooperative
Hemodynamically stable
Able to control airway secretions
Able to coordinate with ventilator
No contraindications
Before revealing list, ask students which patients would be good candidates for NPPV.
After discussion, ask what are contraindications to NPPV.
Cardiorespiratory arrest
Hemodynamic instability
Myocardial ischemia/arrhythmias
Inability to cooperate
Inability to protect airway, high risk for aspiration
Active GI hemorrhage
Severe encephalopathy, etc
Discuss which respiratory conditions are likely to respond to NPPV.
Acute exacerbation of COPD
Cardiogenic pulmonary edema
Asthma
Patients who are not candidates for intubation
Respiratory failure in immunocompromised patients
Copyright 2008 Society of Critical Care Medicine

5. Copyright 2008 Society of Critical Care Medicine
Case Study
What are advantages of using non-invasive positive pressure ventilation in this patient?
Avoids complications of intubation
Preserves airway reflexes
Improved patient comfort
Less need for sedation
Shorter hospital/ICU stay
Improved survival
Slide comes up with question only. Allow discussion before revealing list.
May also discuss disadvantages of NPPV.
Claustrophobia
Facial/nasal pressure lesions
Increased work for respiratory therapist
Unprotected airway
Delay in intubation
Gastric distension, etc
Copyright 2008 Society of Critical Care Medicine

6. Copyright 2008 Society of Critical Care Medicine
Case Study
ABG on 3L/min O2: pH 7.24, PaCO2 60 mm Hg (8 kPa), PaO2 65 mm Hg (8.7 kPa)
HR 110 beats/min, BP 160/110 mm Hg, RR 30 breaths/min
What are the goals for respiratory support?
What settings should be selected for NPPV?
First question about goals of respiratory support appears with case information.
Decrease work of breathing
Improve oxygenation
Improve ventilation
Reveal next question and discuss NPPV settings, how TV is determined and how IPAP and EPAP affect oxygenation and ventilation. Flip chart could be used to write down student suggestions.
Set FIO2 at 1.00
Hypoxemic failure: Inspiratory pressure (IPAP) 10 cm H2O, expiratory pressure (EPAP) 5 cm H2O, titrate EPAP and IPAP in 2 cm H2O increments
Ventilatory failure: IPAP 10 and EPAP 4 cm H2O, titrate IPAP in 2 cm H2O increments
Make changes every minutes
Reveal question on monitoring.
Vital signs, appearance, pulse oximetry and blood gases
If there is time, ask students where patient should be admitted.
How should the patient be monitored?
Copyright 2008 Society of Critical Care Medicine

7. Copyright 2008 Society of Critical Care Medicine
Case Study
After 1 hr of NPPV, the patient has not improved
Arterial blood gas on 40% O2: pH , PaCO2 65 mm Hg (8.7 kPa), PaO2 58 mm Hg (7.8 kPa)
HR 115 beats/min, BP 142/98 mm Hg, RR 32 breaths/min
Review new case information before revealing question.
Discuss reasons for failure of NPPV and need for intubation.
Clinical worsening
No improvement of ABG in 1-2 hrs
Therapeutic goals not reached
What is the next step?
Copyright 2008 Society of Critical Care Medicine

8. Copyright 2008 Society of Critical Care Medicine
Case Study
Orotracheal intubation is performed
What ventilator mode should be selected?
What tidal volume is optimum?
What rate of ventilation should be set?
Note that now several settings must be chosen on the ventilator.
Before answering questions, some background information is needed. Proceed to next slides before discussing.
Copyright 2008 Society of Critical Care Medicine

9. Airway Pressure (cm H2O)
Respiratory Cycle
Triggering
Cycling
Respiratory Cycle
Expiration
Inspiration
Time (sec)
Airway Pressure (cm H2O)
Discuss determinants of triggering for initiation of inspiration and cycling for termination of inspiration
Triggering: drop in airway pressure or diversion of a constant gas flow
Cycling: volume, decrease in flow rate or elapsed time
Reveal text on types of breaths for discussion.
Volume-cycled breath--Preset tidal volume
Time-cycled breath--Pressure control breath, constant pressure for preset time
Flow-cycled breath--Pressure support breath, constant pressure during inspiration
Types of breaths: volume-cycled, time-cycled, flow-cycled
Copyright 2008 Society of Critical Care Medicine

10. Modes of Mechanical Ventilation
Interface of breath types with patient
Assist-control (AC)
Pressure support (PSV)
Synchronized intermittent mandatory (SIMV)
Continuous positive pressure airway pressure (CPAP)—not a mode of ventilation
Note that putting breaths together determines the mode of ventilation; mention 3 main modes.
Reveal and comment on CPAP information.
Copyright 2008 Society of Critical Care Medicine

11. Airway Pressure/Flow Tracings
Spontaneous ventilation
CPAP
Expiration
Inspiration
Pressure
Time
Explain airway pressure over time diagram for spontaneous breathing.
Then reveal CPAP and discuss determinants of respiratory rate, tidal volume
Allows spontaneous breathing at elevated baseline pressure, patient controls rate and TV.
Pressure
Time
Copyright 2008 Society of Critical Care Medicine

12. Modes of Mechanical Ventilation
Assist-control ventilation
Volume or time-cycled breaths
Pressure support ventilation
Flow-cycled breaths
Inspiration
Expiration
Volume assist-control
Cover AC and discuss determinants of respiratory rate, tidal volume for volume and time-cycled breaths.
Discuss advantages and disadvantages.
Reveal PSV diagram and discuss same issues.
Copyright 2008 Society of Critical Care Medicine

13. Modes of Mechanical Ventilation
Synchronized intermittent mandatory ventilation
Volume or time-cycled breaths
SIMV + PSV
Volume-cycled breath
Spontaneous
Discuss determinants of respiratory rate, tidal volume for volume and time-cycled breaths for SIMV.
Discuss advantages and disadvantages.
Reveal diagram for SIMV+PSV.
Copyright 2008 Society of Critical Care Medicine

14. Copyright 2008 Society of Critical Care Medicine
Case Study
Patient with COPD exacerbation who failed NPPV
What ventilator mode should be selected?
What tidal volume is optimum?
What rate of ventilation should be set?
Return to case to discuss initial ventilator settings for the patient. A flip chart or blackboard may be helpful to post suggested settings.
Approach from standpoint of initial ventilator settings as listed in text. Reveal questions sequentially.
Mode: AC or SIMV (discuss potential problems with either mode depending on student response; AC may result in overventilation and SIMV may not decrease work of breathing sufficiently)
FIO2 100%
Tidal volume 8-10 mL/kg PBW
Respiratory rate to achieve desired minute ventilation
PEEP 5 cm H2O
Use next slide to confirm/review discussion.
What FIO2 should be delivered?
Copyright 2008 Society of Critical Care Medicine

15. Initiation of Mechanical Ventilation
Familiar ventilation mode
Initial FIO2 = 1.0; decrease to maintain SpO2 >92% to 94%
Initial tidal volume = 8-10 mL/kg
Rate and minute ventilation appropriate for clinical needs
PEEP to support oxygenation
Call critical care consultant for help
Review recommended initial ventilator settings.
Copyright 2008 Society of Critical Care Medicine

16. Copyright 2008 Society of Critical Care Medicine
Case Study
What monitoring and assessment is needed after initiation of mechanical ventilation?
Chest radiograph
Vital signs
SpO2
Patient-ventilator synchrony
Arterial blood gas
Inspiratory pressures
Inspiratory: expiratory ratio
Auto-PEEP
Ventilator alarms
Question appears when slide presented.
Allow students to discuss types of monitoring/assessments before revealing lists. Items in left list will probably be mentioned in the discussion. Items in right list may be new to students. Indicate that these will be expanded on.
Copyright 2008 Society of Critical Care Medicine

17. Inspiratory Pressures
Peak inspiratory pressure (Ppeak)
Inspiratory plateau pressure (Pplat)
Indicator of alveolar distension
Inspiration
Expiration
Ppeak
Pplat
Ppeak
Pplat
Pplat 30 cm H2O
Introduce 2 inspiratory pressures and reveal diagram to help explain.
Discuss determinants of pressures.
Ppeak= airway resistance + elastic recoil of lungs and chest wall
Pplat= elastic recoil of lungs and chest wall
Reveal tracing from ventilator to reinforce the measurements.
Ask what the goal is for Pplat and reveal value
Ask what are the consequences of high inspiratory pressures.
Barotrauma
Volutrauma
Decreased cardiac output
Ask how Pplat can be decreased.
Decrease TV
Decrease PEEP
Copyright 2008 Society of Critical Care Medicine

18. Inspiratory: Expiratory Ratio
Determinants of inspiratory time with volume ventilation
Tidal volume
Inspiratory flow rate
Inspiratory waveform
Inadequate expiratory time
Incomplete exhalation
Breath stacking
Review inspiratory/expiratory components of respiratory cycle.
Discuss determinants of inspiratory time.
Use example of larger TV leading to longer I time.
Result is inadequate expiratory time.
Copyright 2008 Society of Critical Care Medicine

19. Copyright 2008 Society of Critical Care Medicine
Auto-PEEP
Diagnosis
Measurement
Waveform analysis
Gas
flow
After discussing development of auto-PEEP, ask what clinical conditions would predispose to auto-PEEP during mechanical ventilation.
Obstructive lung disease (asthma, COPD)
High respiratory rates with high tidal volumes
Auto-PEEP
Auto-PEEP
Copyright 2008 Society of Critical Care Medicine

20. Copyright 2008 Society of Critical Care Medicine
Auto-PEEP
Consequences
 Inspiratory pressures
Hypotension
Worsened oxygenation
Interventions to decrease auto-PEEP
 Respiratory rate
 Tidal volume
 Gas flow rate
Ask what the consequences of auto-PEEP are before revealing items.
Then discuss ways to decrease auto-PEEP before revealing items.
Copyright 2008 Society of Critical Care Medicine

21. Copyright 2008 Society of Critical Care Medicine
Questions
Copyright 2008 Society of Critical Care Medicine

22. Copyright 2008 Society of Critical Care Medicine
Key Points
Goals of NPPV and mechanical ventilation are support of oxygenation and ventilation and reduction in work of breathing
NPPV is best used in the alert, cooperative patient whose condition will improve in hours
Consider the advantages/disadvantages of different modes when selecting ventilatory support
Use guidelines when initiating mechanical ventilation and adjust based on monitoring
Copyright 2008 Society of Critical Care Medicine