1. Advanced Modes of Ventilation PRVC, MMV, VS, and ASV
By Joshua and Marissa

3. Lets review!!!
What are the 3 modes?

4. Review continued…
What are the 3 different breath types?

5. REVIEW!! What is PEEP? Why is it used?
What do you need to be careful of when using PEEP?
What is “optimal PEEP”?
How do you assess for auto-PEEP? How is it treated?

6. Ventilator Graphics Which breath type is this??
VOLUME CONTROL
PRESSURE CONTROL

7. Understanding Ventilator Mechanics and Physics
Various pressures involved in inspiration/expiration. The same are either provided or overcome by the ventilator

8. Problems With Conventional Modes of Ventilation
Often they fail to match the patient­based requirements
A ventilator setting appropriate for one point of time may not be optimal with patient deterioration or improvement (These ventilators only deliver the set parameters and take no feedback from patient variables).

9. “Open-loop” vs. “Closed-loop” Systems
All the classical volume/pressure control modes are “Open Loop” (the feedback loop is absent). The newer modes target to make alterations with the changing lung and take feedback from patient parameters, thus completing the feedback loop and are “Closed loop” type.
The control, cycle, or the limit variables undergo self­adjustment and these variables are no longer limited to single parameter determinant but if the threshold of one component is reached they shift to the other alternate set parameter.

10. Benefits of Advanced Modes of Ventilation
Adaptable to a wide variety of patients.
Able to adapt to changing lung mechanics on a breath to breath basis.
Utilizes lung protective strategies
Shortens the weaning time
Shortens time of mechanical ventilation

11. Drawbacks/Limitations of Advanced Modes of Ventilation
Many do not give an “exact” pressure or tidal volume but instead pressure and Vt are “targeted”.
Some modes may favor a faster RR and sacrifice a lower Vt
Mean Airway Pressure is variable
If auto-PEEP is present, the ventilator may not be able to recognize to correct, and/or it may not operate properly

12. Goals of Advanced Modes of Ventilation
Limit the duration of invasive ventilation
Prevent patient ventilator asynchrony
Be applicable to a wide variety of patients and automatically adapt to changes in lung and respiratory mechanics

13. Modes and Ventilator Names

14. Ventilator Modes and Available Ventilators on the Market

15. PRESSURE REGULATED VOLUME CONTROL (PRVC)

16. Short History
PRVC was introduced in 1991 created by Siemens Servo 300 ventilator.

17. PRVC is also called… Auto flow Adaptive pressure ventilation
Volume control + (VC+)
Volume targeted Pressure control
Pressure control volume guaranteed

18. SERVO 300
GALILEO

19. What is PRVC?
Pressure regulated volume control delivers pressure controlled breaths with a target tidal volume
However PRVC can increase or decrease the vent will just adjust the inflation pressure to achieve target volume.
In other words PRVC has an average minimal tidal volume but not a max.
PRVC is pressure limited and time cycled

20. CONTINUED
The ventilator will measure tidal volume delivered if the delivered tidal volume is less or more the ventilator will increase or decrease pressure delivered until set tidal volume and delivered are equal

22. How does PRVC differ from AC-PC?
The pressure level adjust on a breath to breath analysis to reach a target tidal volume.

23. SETTINGS??? Target tidal volume Inspiratory time Rate Rise time FIO2
PEEP
Sensitivity
Pressure limit (in alarms)
On SIMV same settings add PS or VS

24. HOW DOES PRVC WORK??
The ventilator assesses the previous breath and adjust pressure from 1-3 cm H20 while assessing the tidal volume.

25. First breath
Which is known as the test breath is 5-10 cm H20 above peep
The test breath consists of an inspiratory hold to obtain a plateau pressure on the next breath.
During the next three breaths pressure is increased to 75 percent needed for set tidal volume.
After that the pressure will only change +/- 3 cm H20 per breath
Time ends inspiration

27. Quick review

28. What we should keep in mind..
The vent will ALARM when delivered pressure rises to 5 cm H20 below the set upper pressure limit.
Flow varies automatically to patient demands.
During each breath there is a constant pressure however the pressure varies from breath to breath

29. Disadvantages to PRVC Mean airway pressure varies
Can cause auto peep or make it worse
When patient demand is increase pressure level may diminish when support is needed.
Sudden increase in RR and demand may result in a decrease in vent support.
Since the pressure delivered is dependent on tidal volume from the previous breath sudden inspiratory effort such as cough or yawning can result in different volumes that can be higher or lower than the setting.

30. Advantages to PRVC Helps maintain a low PIP Targeted tidal volume
Little WOB requirement
Decelerating flow waveform for improved gas distribution

31. INDICATIONS..
Patients who require the lowest PIP and a target tidal volume
Acute lung injury/ARDS to help limit PIP to protect the lung
Patients requiring high or variable flow
Patient with the possibility of changing lung compliance or Raw

32. COOL thing about PRVC..
Is that it combines volume ventilation and pressure control
Targeted tidal volume
Vent adjust level of pressure control breath by breath analysis
Can provide better synchrony for the patient because it adapts to pt changing output.
Ventilator estimates volume/pressure relationship with each breath
Inverse relationship between volume and pressure if the pressure goes up volume goes down if the volume goes up the pressure will go down

33. When not to use PRVC.. Patients with erratic breathing patterns
Cheynes stokes breathing
Excessive coughing
seizures

34. PRVC with volume support weaning protocol
1.) switch to PRVC-SIMV with VS 2.) decrease tidal volume by percent Assess weaning parameters RSBI < 100 RR< 30 VE <10 L/min Sp02>92% Pa02> 60mmHg Hemodynamically stable

35. Weaning continued MIP <-20 cmH20 MVV > 20 L/min
Watching vital signs decrease to 50 percent of original tidal volume
Volume support 5-10 cmH20
Abg normalized
Call physican for order to extubate!

36. Volume Support Mode (VS)

37. What is Volume Support?
VS is an entirely spontaneous mode that assists with patients who are breathing spontaneously in order to help them achieve a “target” volume.
Pressure limited, Volume targeted, and flow cycled
Basically, VS is pressure support with a set “target” Vt.
It adjusts pressure (up or down) to achieve the target volume.
Maximum adjustment in pressure from breath-to-breath is 1-3 cm H2O
If flow reaches within 5% of peak flow during the breath, the ventilator will cycle off.

38. Ventilation Graphics in Volume Support Mode (VS)

41. Benefits of VS
Helps to decrease a patient’s WOB and assists with weaning for patients who are breathing spontaneously.
It automatically weans patient off of pressure support as long as the minimum Vt is being met.
Gives pressure supported breaths using the lowest required pressure
Allows patient to control I:E time
Breath to breath analysis and varies minute ventilation to meet patient demand.

42. Disadvantages of VS May tend to give smaller tidal volumes Varying MAP
If auto-PEEP is present, the mode may not work properly
A sudden increase in RR or patient demand may result in a decrease in ventilator support (coughing, hiccups, seizure, etc.)

43. PRVC with Auto-mode and Volume Support
Available with the Servo I and Galileo ventilators
When the patient begins to breathe, the ventilator automatically switches from PRVC to Volume support.
If there are no spontaneous breaths, the ventilator switches to PRVC.

44. MANDATORY MINUTE VENTILATION (MMV)

45. Mandatory minute ventilation
MMV is also known as minimum minute ventilation or augmented minute ventilation.
However this mode is not widespread due to limitations and lack of understanding.

46. History..
MMV is an original mode of mechanical ventilation introduced by Hewlett et al. in 1977 in this mode the patient is guaranteed a predetermined minute volume called preset minute volume. If the patient is able to spontaneously breath and reach the preset minute volume the ventilator does not deliver any mechanical breaths. If however the spontaneous breathing does not reach the minute ventilation the needed minute ventilation will be delivered.

47. How does it work?
Rt sets a minimum minute ventilation which is usually between percent of patients current minute ventilation.
The ventilator will provide the part of minute ventilation that the patient is unable to accomplish.
This is done by increasing the breath rate or the preset pressure.

48. Indications
Used on any patient who is spontaneously breathing and is deemed ready to wean
Patients with unstable ventilatory drive
Advantages:
-Full to partial ventilatory support
-Allows spontaneous ventilation with safety net
-Patients minute ventilation stays stable
-Prevents hypoventilation

49. Disadvantages
Adequate minute ventilation may not be sufficient (shallow breathing)
High rate alarm must be set low enough to alert for RSB
Mean airway pressure is variable
Inadequate set minute ventilation can lead to inadequate support and patient fatigue
Excessive minute ventilation with no spontaneous breathing can lead to total support.

50. Limitations when using MMV
Development of fast and ineffective breathing
Development of auto peep
Delivering dangerously high tidal volumes
Increased dead space

51. Adaptive Support Ventilation (ASV)

52. What is ASV?
ASV is a new ventilatory mode, which uses a closed-loop controlled mode between breaths.
The ventilator allows the clinician to set a maximum plateau pressure and desired minute ventilation based on the patient's ideal weight.
It automatically selects the target ventilatory pattern based on user inputs, as well as taking into account the respiratory mechanics data from the ventilator monitoring system (resistance, compliance, auto-PEEP).
This mode can be safely used during initiation, maintenance, or weaning phases of the mechanical ventilation.
ASV's goal is to ensure an effective alveolar ventilation level, minimize the WOB, and lead the patient to an optimal ventilatory pattern in order to reduce complications such as volutrauma or barotrauma and air trapping.

53. Background History of ASV
ASV evolved as a form of mandatory minute ventilation (MMV) implemented with adaptive pressure control, and described by Hewlett in 1977.
 ASV first clinical application was described in 1994 by Laubscher et al. It became commercially available in Europe in 1998, but it was not until 2007 that it was marketed in the United States.

54. About ASV
The machine selects a Vt and frequency that the patient's brain would presumably select if the patient were not connected to a ventilator.
This pattern is assumed to encourage the patient to generate spontaneous breaths.
This mode provides specific minute ventilation and a breathing pattern optimized to the point of the smallest total energy expenditure, and it is based on patient's requirements.

55. ASV vs. “other modes”
Among the closed-loop systems available are Proportional Assist Ventilation (PAV), Neurally Adjusted Ventilatory Assistance (NAVA), Knowledge-Based Systems (KBS), and ASV. The first three (PAV, NAVA, and KBS) are basically advanced versions of Positive Pressure Support Ventilation (PSV) and therefore are considered to be "ventilatory modes". On the other hand, ASV combines various ventilatory modes:
PSV, if the patient's respiratory rate (RR) is higher than the target
Pressure controlled ventilation, if there is no spontaneous breathing
Synchronized intermittent mandatory ventilation (SIMV), when patient's RR is lower than target. 

56. Hamilton ASV Sensors Proximal Flow Sensor Volumetric Capnography
The proximal flow sensor precisely measures the pressure, volume, and flow directly at the patient’s airway opening. This provides the required sensitivity and response time, and prevents dead space ventilation. The patient is better synchronized and has less work of breathing as a result. 
Volumetric Capnography
Integrated SpO2 Sensor

57. What The User Sets ASV vent settings:
Height of the patient (based on this, the vent will automatically calculate ideal body weight and dead space)
Gender
% Min Vol: %
Normal 100%, Asthma 90%, ARDS 120%, Others 110%
Add 20% if body temp is >101.3 degrees Fahrenheit
Add 5% for every 1640 feet above sea level (500 m)
Trigger: flow trigger of 2 L/min
Expiratory trigger sensitivity: Start with 25% and 40% in COPD
Tube resistance compensation: Set to 100%
High pressure alarm limit: 10 cm H 2 O be the limit of ↓ and ↑ least 25 cm H 2 O of PEEP/continuous positive airway pressure (CPAP)
 PEEP
FiO2

58. What the Ventilator Calculates Automatically
Dead space based on the ideal weight (dead space [Vd ] = 2.2 ml/kg)
ASV selects the respiratory pattern in terms of RR, VT, Inspiratory:Expiratory time (I:E ratio) for mandatory breathing and reaches the respiratory pattern selected. Thus, it is volume and pressure limited. Basically, ASV uses the Otis et al. and Mead et al. equation developed in 1950, that states that for a given level of alveolar ventilation, there is a particular RR which achieves a lower WOB. Therefore it is more energy efficient to minimize the cumulative effects of elastic and resistive load imposed on the respiratory system.

59. How Does ASV Work?
Closed-loop feedback system. The operator presets a target tidal volume (VT), through a feedback signal, the system measures the tidal volume of the patient (VT observed). The target VT and VT observed are compared (added or subtracted) and then an error signal is sent to the controller, which regulates the received signal and makes adjustments as needed to send an output signal, resulting in a desired breathing pattern, which can be eventually measured

60. How The “Closed-loop” System Works
In the closed-loop system, the output of gas is measured by providing a feedback signal that can be compared with the input value. The classical system of negative feedback control differentiates between input and output of gases, thus generating an error signal used to adjust the output so that it matches the input. The feedback control forces the gas output to become stable in the presence of environmental changes (such as leakage of the circuit, changes in lung mechanics, and respiratory muscle strain). This also automatically applies lung protection strategies, reducing the risk of errors committed by the operators.

61. Point A shows that in order to maintain alveolar ventilation with very low RR, it is needed to use large VTs, which implies a high level of WOB. On the other hand, Point B, shows that a high amount of muscular effort is required to maintain adequate alveolar ventilation at high RRs (and low volume) in an attempt to overcome the resistance to flow. However, there is an optimal RR, which is the least costly in terms of WOB (Point C).

62. The operator sets % VM, Pmax , PEEP and FiO 2
The operator sets % VM, Pmax , PEEP and FiO 2 . The system by calculations and by a dual closed-loop system (RR goal and target VT) it calculates the RR and volume in which there is the lowest WOB (thus more efficient ventilation) within safety margins, adjusting inspiratory pressure and I:E ratio to achieve the desired goals.

63. ASV mode is based on lung protective strategies, which aim to reach the RR and VT target, inside a security boundary area, where the highest energy efficiency is obtained and complications such as apnea, volutrauma, barotrauma and/or dead space ventilation are avoided

65. Safety limits calculated based on these parameters.

66. ASV Initiation
Once started, ASV provides a series of test breaths or test mode P-SIMV (with RRs between 10 and 15 min according to ideal body weight and assigned to inspiratory pressure above 15 cm H 2 O pressure basal), in which it measures the expiratory time constant for the respiratory system, and uses this along with the estimated dead space and normal minute ventilation in order to calculate an optimal breathing frequency in terms of mechanical work. During this breathing test, the ventilator measures compliance, Rce , VT, and RR based on selected inspiratory time (Ti ), mandatory rate (f), and inspiratory pressure (Pinsp ), according to the height (adult or pediatric age range) that the operator sets. In order to have a VT and RR target are determined within safety limits. This means that the pressure limit is automatically adjusted to achieve an average delivered VT equal to the target. The ventilator continuously monitors the mechanics of the respiratory system and adjusts its settings accordingly.

67. Changes to Make Based Off ABG

68. Benefits of ASV
Can be used safely and effectively in over 98% of patients.
Reduce time on the ventilator by over 50%
2 controlled studies show that while less user interaction is required and fewer alarms occur, ASV also facilitates shorter time on the ventilator: 6 hours with ASV as compared to 14 hours with conventional ventilation.
Studies show that ASV:
can be used to ventilate virtually all intubated patients whether active or passive and regardless of the lung disease
requires less user interaction, adapts to the patient’s breathing activity more frequently and causes fewer alarms
adapts to changes in the patient’s lung mechanics over time
works comparable to experienced clinicians
allows shorter weaning times
allows shorter ventilation times
ASV adapts to lung mechanics by automatically applying lower tidal volumes in ARDS patients.

69. Benefits (continued) Start weaning at intubation
The unique closed-loop ventilation system ASV automatically promotes spontaneous breathing for patients in all ventilation modes and phases. It encourages spontaneous activity right from the start of ventilation and promotes weaning from first deployment.
Studies show the results: a shorter length of ventilation and a shorter weaning time.
 ASV employs lung protective strategies to minimize complications from AutoPEEP and barotrauma. ASV also prevents apnea, tachypnea, excessive dead space ventilation and excessively large breaths.

70. Further ASV Research Studies show that:
In passive patients, ASV selects different tidal volume / respiratory rate combinations for normal lung, COPD, and ARDS patients (Arnal 2008).
In active patients, ASV decreases work of breathing and improves patient-ventilator synchrony (Wu 2010, Tassaux 2010). 
In the ICU, ASV decreases the weaning duration in medical patients (Chen 2011) and COPD patients (Kirakli 2011).
In post-cardiac surgery, ASV allows earlier extubation than conventional modes (Gruber 2008, Sulzer 2001) with fewer manual adjustments (Petter 2003) and fewer ABG analyses performed (Sulzer 2001). 

71. Advantages and Disadvantages of ASV

72. Advantages/Disadvantages (cont.)

73. Drawbacks/Limitations of ASV
Clinician's lack of understanding results in inappropriate programming.
Inability to recognize dead space ventilation or shunts to make adjustments to ventilation.
In clinical conditions where lung physical parameters remain unchanged (pulmonary embolism), the mode fails to adapt to patients requirements.
Auto­PEEP may become problem in chronic obstructive pulmonary disease (COPD) patients needing longer expiratory times which are currently unaccounted in current protocols of automatic adjustments.

74. Conventional vs. Adaptive Weaning

75. The FUTURE of Advanced Ventilation Modes

76. History of Ventilation
NEGATIVE PRESSURE VENTILATIORS
FROM THE 19TH CENTURY

77. Cutting Edge Ventilators of Today
Closed-loop adaptive ventilators
Hamilton S-1
Galileo

78. Future Ventilator Capabilities

79. ASV Set Up And Use On A Real Patient

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Citations