1. Principles of Mechanical Ventilation
RET 2284
Module 3.0
Modes of Ventilation

2. Modes of Ventilation Mode
Description of a breath type and the timing of breath delivery
Terms or acronyms used to describe the way a ventilator performs in a particular situation; often invented by physicians, therapists, or manufacturers
Basically there are three breath delivery techniques used with invasive positive pressure ventilation
CMV – controlled mode ventilation
SIMV – synchronized
Spontaneous modes

3. Modes of Ventilation CMV Continuous Mandatory Ventilation
All breaths are mandatory and can be volume or pressure targeted
Controlled Ventilation – when mandatory breaths are time triggered
Assist/Control Ventilation – when mandatory breaths are either time triggered or patient triggered

4. Modes of Ventilation CMV Continuous Mandatory Ventilation
Controlled Ventilation – when mandatory breaths are time triggered
Mandatory breath – ventilator determines the start time (time triggered) and/or the volume or pressure target

5. Modes of Ventilation CMV Controlled Ventilation
Appropriate when a patient can make no effort to breathe or when ventilation must be completely controlled
Drugs
Cerebral malfunctions
Spinal cord injury
Phrenic nerve injury
Motor nerve paralysis

6. Modes of Ventilation CMV Controlled Ventilation
In other types of patients, controlled ventilation is difficult to use unless the patient is sedated or paralyzed with medications
Seizure activity
Tetanic contractions
Inverses I:E ratio ventilation
Patient is fighting (bucking) the ventilator
Crushed chest injury – stabilizes the chest
Complete rest for the patient

7. Modes of Ventilation CMV Controlled Ventilation
Adequate alarms must be set to safeguard the patient
E.g., disconnection
Sensitivity should be set so that when the patient begins to respond, they can receive gas flow from the patient
Do not lock the patient out of the ventilator!

8. Modes of Ventilation CMV Assist/Control Ventilation
A time or patient triggered CMV mode in which the operator sets a minimum rate, sensitivity level, type of breath (volume or pressure)
The patient can trigger breaths at a faster rate than the set minimum, but only the set volume or pressure is delivered with each breath

9. Modes of Ventilation CMV Assist/Control Ventilation Indications
Patients requiring full ventilatory support
Patients with stable respiratory drive
Advantages
Decreases the work of breathing (WOB)
Allows patients to regulate respiratory rate
Helps maintain a normal PaCO2
Complications
Alveolar hyperventilation

10. Modes of Ventilation CMV Volume Controlled – CMV
Time or patient triggered, volume targeted, volume cycled ventilation
Graphic (VC-CMV)
Time-triggered, constant flow, volume-targeted ventilation

11. Modes of Ventilation CMV Volume Controlled – CMV
Time or patient triggered, volume targeted, volume cycled ventilation
Graphic (VC-CMV)
Time-triggered, descending-flow, volume-targeted ventilation

12. Modes of Ventilation CMV Pressure Controlled – CMV
PC – CMV (AKA – Pressure control ventilation - PCV)
Time or patient triggered, pressure targeted (limited), time cycled ventilation
The operator sets the length of inspiration (Ti), the pressure level, and the backup rate of ventilation
VT is based on the compliance and resistance of the patient’s lungs, patient effort, and the set pressure

13. Modes of Ventilation CMV Pressure Controlled – CMV
Note inspiratory pause

14. Modes of Ventilation
CMV
Pressure Controlled – CMV
Note shorter Ti

15. Modes of Ventilation CMV Pressure Controlled – CMV
Airway pressure is limited, which may help guard against barotrauma or volume-associated lung injury
Maximum inspiratory pressure set at 30 – 35 cm H2O
Especially helpful in patients with ALI and ARDS
Allows application of extended inspiratory time, which may benefit patients with severe oxygenation problems
Usually reserved for patient who have poor results with a conventional ventilation strategy of volume ventilation

16. Modes of Ventilation CMV Pressure Controlled – CMV
Occasionally, Ti is set longer than TE during PC-CMV; known as Pressure Control Inverse Ratio Ventilation
Longer Ti provides better oxygenation to some patients by increasing mean airway pressure
Requires sedation, and in some cases paralysis

17. Modes of Ventilation IMV and SIMV
Intermittent Mandatory Ventilation – IMV
Periodic volume or pressure targeted breaths occur at set interval (time triggering)
Between mandatory breaths, the patient breathes spontaneously at any desired baseline pressure without receiving a mandatory breath
Patient can breathe either from a continuous flow or gas or from a demand valve

18. Modes of Ventilation IMV and SIMV
Intermittent Mandatory Ventilation – IMV
Indications
Facilitate transition from full ventilatory support to partial support
Advantages
Maintains respiratory muscle strength by avoiding muscle atrophy
Decreases mean airway pressure
Facilitates ventilator discontinuation – “weaning”

19. Modes of Ventilation IMV and SIMV
Intermittent Mandatory Ventilation – IMV
Complications
When used for weaning, may be done too quickly and cause muscle fatigue
Mechanical rate and spontaneous rate may asynchronous causing “stacking”
May cause barotrauma or volutrauma

20. Modes of Ventilation IMV and SIMV Synchronized IMV
Operates in the same way as IMV except that mandatory breaths are normally patient triggered rather than time triggered (operator set the volume or pressure target)
As in IMV, the patient can breathe spontaneously through the ventilator circuit between mandatory breaths

21. Modes of Ventilation IMV and SIMV Synchronized IMV
At a predetermined interval (respiratory rate), which is set by the operator, the ventilator waits for the patient’s next inspiratory effort
When the ventilator senses the effort, the ventilator assists the patient by synchronously delivering a mandatory breath

22. Modes of Ventilation IMV and SIMV Synchronized IMV
If the patient fails to initiate ventilation within a predetermined interval, the ventilator provides a mandatory breath at the end of the time period

23. Modes of Ventilation IMV and SIMV Synchronized IMV Indications
Facilitate transition from full ventilatory support to partial support
Advantages
Maintains respiratory muscle strength by avoiding muscle atrophy
Decreases mean airway pressure
Facilitates ventilator discontinuation – “weaning”

24. Modes of Ventilation IMV and SIMV Synchronized IMV Complications
When used for weaning, may be done too quickly and cause muscle fatigue

25. Modes of Ventilation Spontaneous Modes
Three basic means of providing support for continuous spontaneous breathing during mechanical ventilation
Spontaneous breathing
CPAP
PSV – Pressure Support Ventilation

26. Modes of Ventilation Spontaneous Modes Spontaneous breathing
Patients can breathe spontaneously through a ventilator circuit; sometimes called T-Piece Method because it mimics having the patient ET tube connected to a Briggs adapter (T-piece)
Advantage
Ventilator can monitor the patient’s breathing and activate an alarm if something undesirable occurs
Disadvantage
May increase patient’s WOB with older ventilators

27. Modes of Ventilation Spontaneous Modes CPAP
Ventilators can provide CPAP for spontaneously breathing patients
Helpful for improving oxygenation in patients with refractory hypoxemia and a low FRC
CPAP setting is adjusted to provide the best oxygenation with the lowest positive pressure and the lowest FiO2

28. Modes of Ventilation Spontaneous Modes CPAP Advantages
Ventilator can monitor the patient’s breathing and activate an alarm if something undesirable occurs

29. Modes of Ventilation Spontaneous Modes
PEEP (Positive End Expiratory Pressure)
“According to its purest definition, the term PEEP is defined as positive pressure at the end of exhalation during either spontaneous breathing or mechanical ventilation. However, use of the term commonly implies that the patient is also receiving mandatory breaths from a ventilator.” (Pilbeam)
PEEP becomes the baseline variable during mechanical ventilation

30. Modes of Ventilation Spontaneous Modes PEEP
Helps prevent early airway closure and alveolar collapse and the end of expiration by increasing (and normalizing) the functional residual capacity (FRC) of the lungs
Facilitates better oxygenation
NOTE: PEEP is intended to improve oxygenation, not to provide ventilation, which is the movement of air into the lungs followed by exhalation

31. Modes of Ventilation Spontaneous Modes
Pressure Support Ventilation – PSV
Patient triggered, pressure targeted, flow cycled mode of ventilation
Requires a patient with a consistent spontaneous respiratory pattern
The ventilator provides a constant pressure during inspiration once it senses that the patient has made an inspiratory effort

32. Modes of Ventilation
Spontaneous Modes
PSV

33. Modes of Ventilation Spontaneous Modes PSV Indications
Spontaneously breathing patients who require additional ventilatory support to help overcome
WOB, CL, Raw
Respiratory muscle weakness
Weaning (either by itself or in combination with SIMV)

34. Modes of Ventilation Spontaneous Modes PSV Advantages
Full to partial ventilatory support
Augments the patients spontaneous VT
Decreases the patient’s spontaneous respiratory rate
Decreases patient WOB by overcoming the resistance of the artificial airway, vent circuit and demand valves
Allows patient control of TI, I, f and VT

35. Modes of Ventilation Spontaneous Modes PSV Advantages
Set peak pressure
Prevents respiratory muscle atrophy
Facilitates weaning
Improves patient comfort and reduces need for sedation
May be applied in any mode that allows spontaneous breathing, e.g., VC-SIMV, PC-SIMV

36. Modes of Ventilation Spontaneous Modes PSV Disadvantages
Requires consistent spontaneous ventilation
Patients in stand-alone mode should have back-up ventilation
VT variable and dependant on lung characteristics and synchrony
Low exhaled E
Fatigue and tachypnea if PS level is set too low

37. Modes of Ventilation Spontaneous Modes Flow Cycling During PSV
Flow cycling occurs when the ventilator detects a decreasing flow, which represents the end of inspiration
This point is a percentage of peak flow measured during inspiration
PB 7200 – 5 L/min
Bear 1000 – 25% of peak flow
Servo 300 – 5% of peak flow
No single flow-cycle percent is right for all patients

38. Modes of Ventilation Spontaneous Modes Flow Cycling During PSV
Effect of changes in termination flow
A: Low percentage (17%)
B: High percentage (57%)
Newer ventilators have an adjustable flow cycle criterion, which can range from 1% - 80%, depending on the ventilator

39. Modes of Ventilation Spontaneous Modes PSV during SIMV
Spontaneous breaths during SIMV can be supported with PSV (reduces the WOB)
PCV – SIMV with PSV

40. Modes of Ventilation Spontaneous Modes PSV during SIMV
Spontaneous breaths during SIMV can be supported with PSV
VC – SIMV with PSV

41. Modes of Ventilation Spontaneous Modes PSV
NOTE: During pressure support ventilation (PSV), inspiration ends if the inspiratory time (TI) exceeds a certain value. This most often occurs with a leak in the circuit. For example, a deflated cuff causes a large leak. The flow through the circuit might never drop to the flow cycle criterion required by the ventilator. Therefore, inspiratory flow, if not stopped would continue indefinitely. For this reason, all ventilators that provide pressure support also have a maximum inspiratory time.

42. Modes of Ventilation Spontaneous Modes PSV
Setting the Level of Pressure Support
Goal: To provide ventilatory support
Spontaneous tidal volume is 10 – 12 mL/Kg of ideal body weight
Maintain spontaneous respiratory rate <25/min
Goal: To overcome system resistance (ET Tube, circuit, etc.) in the spontaneous or IMV/SIMV mode
Set pressure at (PIP – Pplateau) achieved in a volume breath or at 5 – 10 cm H2O

43. Modes of Ventilation Spontaneous Modes PSV
Exercise: Using the PIP and the PPlateau from the pressure waveform below, recommend a pressure support setting for this patient (patient is in VC-SIMV mode) 35 25
Answer: 10 cm H2O

44. Modes of Ventilation Spontaneous Modes PSV - The results of your work
35 cm H2O
10 cm H2O

45. Modes of Ventilation Spontaneous Modes
Bilevel Positive Airway Pressure (BiPAP)
An offshoot of PEEP/CPAP therapy
Most often used in NPPV
AKA
Bilevel CPAP
Bilevel PEEP
Bilevel Pressure Support
Bilevel Pressure Assist
Bilevel Positive Pressure
Bilevel Airway Pressure

46. Modes of Ventilation Spontaneous Modes
Bilevel Positive Airway Pressure (BiPAP)
Commonly patient triggered but can be time triggered, pressure targeted, flow or time cycled
The operator sets two pressure levels
IPAP (Inspiratory Positive Airway Pressure)
IPAP is always set higher than EPAP
Augments VT and improves ventilation
EPAP (Expiratory Positive Airway Pressure)
Prevents early airway closure and alveolar collapse at the end of expiration by increasing (and normalizing) the functional residual capacity (FRC) of the lungs
Facilitates better oxygenation

47. Modes of Ventilation Spontaneous Modes
Bilevel Positive Airway Pressure (BiPAP)
The operator sets two pressure levels
IPAP
EPAP
NOTE: The pressure difference between IPAP and EPAP is pressure support

48. Modes of Ventilation
Questions?