Monday, November 23, 2015


In a previous post "APRV in the operating room is it practical?"  I argue that bringing a ICU ventilator into the operating room to utilize APRV is not practical and may lead to hypoventilation and hypoxia due to administration of anesthetic agents [1].

During surgical procedures the patient is maintained in stage 3 of anesthesia known as the "surgical stage". Stage 3 is broken down into four distinct planes, "from onset of automatic respiration to respiratory paralysis" [2]. The patient is usually maintained in Plane 3 (intercostal muscle paralysis) or Plane 4 (diaphragmatic paralysis) leading to the cessation of spontaneous breaths.

One key advantage of APRV is that the patient may breathe spontaneously contributing to the overall minute volume, with the termination of spontaneous efforts the patient will become severely hypercapnic.

Below is an image (fig 1) I captured from a "Pressure Control Ventilation Simulator" [3] demonstrating an ARDS patient on APRV.

Figure 1. Pressure Control Ventilation Simulator, notice patients PaCO2 at 100.7 mmHg.

Notice in figure 1 the outcome for a patient not contributing to the overall minute ventilation the PaCO2 would be 100.7 mmHg. 

Another example of how APRV maybe harmful in the operating room is when trying to mimic APRV with a anesthesia delivery system.

Wednesday, November 4, 2015

The Volume Control Ventilation Fallacy

Volume Control- Continuous Mandatory Ventilation with a “Set-point” targeting scheme (VC-CMV(s)) is likely the most utilized mode of mechanical ventilation in adult patients in North America. This is due to a few a reasons:

1.      VC-CMV is a standard mode on almost every intensive care ventilator and anesthesia delivery system.
2.      VC-CMV is one of the first modes of mechanical ventilation.
3.      VC-CMV is easy to understand in both theory and operation.
4.      VC-CMV is the standard of care when ventilating patients with Acute Respiratory Distress Syndrome (ARDS) and Acute Lung Injury (ALI).
5.      VC-CMV is the standard of care for adult patients intraoperatively.

The key advantage of VC-CMV(s) is the safety and simplicity of the set-point targeting scheme. The operator can manually set all parameters of the volume/flow waveform and adjust the minimum minute ventilation parameters (relating to frequency and tidal volume). “One can quickly trouble-shoot a patient’s situation, so during a change the operator can diagnose the problem and intervene rapidly”. [1]

When one sees a mode of ventilation labeled “Volume Control”, “VC”, “Volume A/C”, or “CMV” it affirms that the breathing pattern delivered to the patient will consist of a constant tidal volume and inspiratory flow waveform (fig. 1) 

Figure 1. Volume Control Ventilation Breath Pattern.

Figure 2. Volume and Flow waveform remains constant even-though compliance decreased to 25, compared to Figure 1.  

regardless of changes in a patient’s respiratory system mechanics and/or inspiratory drive (fig. 2) [2]. Conversely, due to no industry standard for ventilator mode taxonomy and medical device manufacturers marketing schemes the actual breath delivered to the patient does not resemble the predicted breath pattern and may result in a tidal volume much larger than the expected preset value.

How does this happen?

Sunday, September 20, 2015

Ventilator Mode Map App

Ventilator Mode Map Mobile App

Due to no industry standard for ventilator mode taxonomy and over 170 unique names for modes of ventilation.  Learning and understanding ventilator mode classification can be problematic.   Ventilator Mode Map provides a easy to use handheld solution.   With this app one can choose from 12 different vendors,  37 different models (with pictures) and provides hundreds of definitions. One would have to review various text books and journal articles to compile this knowledge base.

This app is for android devices, I have a copy on my Samsung Galaxy tablet & Motorola phone, works fine on both devices. Available on Google Play see link below.


Ventilator Mode Map

Friday, September 18, 2015

Free Virtual Mechanical Ventilator

OPENPediatrics website provides a free virtual mechanical ventilator that allows users to review mechanical ventilator knowledge, play scenarios, and test their skills with case simulations.

One just needs to register for free on their "Clinician Community Site" to utilize the simulator. 



Thursday, November 6, 2014

Intelligent Targeting Schemes

A Intelligent targeting scheme is "a ventilator control system that uses artificial intelligence programs such as fuzzy logic, rule based expert systems, & artificial neural networks" (Chatburn, 2012). Examples of modalities that use  Intelligent targeting are Smartcare & IntelliVent-ASV.

Please view the above video for more information on Intelligent targeting schemes.


Chatburn, R. (2012). Standardized Vocabulary for Mechanical Ventilation. Mandu Press. 

*Note- this reference is available under the link free mechanical ventilation handouts.

Monday, November 3, 2014

Optimal Targeting Schemes

A Optimal targeting scheme is a "ventilator control system that automatically adjusts the targets of the ventilatory pattern to either minimize or maximize some overall performance characteristic" (Chatburn, 2002). 

Please view the above video for more information on Optimal targeting. 



Chatburn, R. (2012). Standardized Vocabulary for Mechanical Ventilation. Mandu Press. 

*Note- this reference is available under the link free mechanical ventilation handouts.

Friday, October 31, 2014

Adaptive Targeting Schemes

Adaptive targeting schemes use "a control system that allows the ventilator to automatically set some (or all) of the targets between breaths to achieve other preset targets" (Chatburn, 2012). Adaptive Pressure Control is most likely the most recognized and most used modality that uses a adaptive targeting scheme.

 Please review the above video for a more detailed description. 

Adaptive Pressure Control Playlist


Chatburn, R. (2012). Standardized Vocabulary for Mechanical Ventilation. Mandu Press. 

*Note- this reference is available under the link free mechanical ventilation handouts.

Tuesday, October 28, 2014

Servo Targeting Schemes

Ventilator modes that use Servo targeting schemes are very responsive and provide the most comfort and synchrony in the spontaneous breathing patient. Servo targeting is "a control system for which the output of the ventilator automatically follows a varying input. This means that the inspiratory pressure is proportional to inspiratory effort" (Chatburn, R.). 

The below videos give a brief description of Servo targeting schemes and ventilator modes that use Servo targeting schemes. 

Thursday, September 25, 2014

Automatic Tube Compensation

Automatic Tube Compensation is "a feature that allows the operator to enter the size of the patient's endotracheal tube & have the ventilator calculate the tubes resistance & then generate just enough pressure to compensate for the added resistive load" (Chatburn, R. 2012).

Free Mechanical Ventilation Handouts

Servo Targeting 


Chatburn, R. (2012). Standardized Vocabulary for Mechanical Ventilation. Mandu Press. 

*Note- this reference is available under the link free mechanical ventilation handouts.

Tuesday, September 23, 2014

Saturday, September 20, 2014

Correcting flow mismatch by increasing ventilator flow rate

Flow mismatch is a common patient ventilatory asynchrony associated with volume ventilation, which may lead to cardiovascular instability, increased oxygen consumption, increased carbon dioxide production, increased patient discomfort and prolonged mechanical ventilation[iv]. Fortunately, flow mismatch can be simply identified with the proper assessment of the pressure waveform.

To correct flow mismatch titrate the flow rate to match the patient’s inspiratory demands. Another corrective action is switching from a constant flow pattern to a decelerating flow pattern this provides a high initial peak flow. One must consider that changes in ventilatory demand may result in unnecessary higher than average assist resulting in ventilator induced diaphragm dysfunction[ii], a lower PaCO2 set-point, and delay in liberation.


Creating Flow Mismatch with a Simulator

Oxylog 3000 Simulator

Why I do not use Draeger ventilator simulators

Flow mismatch: patient ventilator asynchrony associated with volume ventilation

Waveform of the week: Flow Mis-match

Decreasing Dyspnea During Mechanical Ventilation

Friday, September 12, 2014

Creating Flow Mismatch with a simulator

I know in the past I stated I did not use Draeger simulators. However this Oxylog simulator is responsive and I will be using it in a few videos. This video demonstrates that with this simulator, one can create "Flow Mismatch" a patient-ventilator asynchrony common in VC-CMV.


Oxylog 3000 Simulator

Why I do not use Draeger ventilator simulators

Flow mismatch: patient ventilator asynchrony associated with volume ventilation

Waveform of the week: Flow Mis-match

Decreasing Dyspnea During Mechanical Ventilation

Sunday, September 7, 2014

Dual Targeting Schemes

Dual targeting schemes are a step above Set-point targeting in regards to engineering hierarchy. These modes can switch from volume-control to pressure-control during the inspiratory phase. 

The above video overviews dual targeting schemes and presents the advantages and disadvantages of these modalities. 


Chatburn, R. (2012). Standardized Vocabulary for Mechanical Ventilation. Mandu Press. 

*Note- this reference is available under the link free mechanical ventilation handouts.

Friday, September 5, 2014

Targeting Schemes

A Targeting Scheme is "A model of the relationship between operator inputs and ventilator outputs to achieve a specific ventilatory pattern, usually in the form of a feedback control system" [1]. The targeting scheme describes the main functionality of a ventilator mode and helps one differentiate modes of mechanical ventilation. 

This is not only helpful when classifying a mode for academic purposes, but the knowledge of a targeting scheme is beneficial when selecting a ventilator mode to best match its capabilities to the clinical goals of mechanical ventilation. 

Thursday, June 26, 2014

Arterial Waveform Analysis Devices

Image 1: From PiCCO @ Bedside, iOS Mobile app [1]. 

Due to the results of the March 2014 "ProCess Trial" indicating that early goal directed therapy in septic shock did not improve outcomes [2] , there has been less interest in using pulse contour analysis devices to optimize fluid management in the critically ill patient. 

The main reason for this is that these devices, even though less invasive then the pulmonary artery catheter still require at the minimum an arterial line and in addition (depending on device) a central venous catheter

However, before letting these devices collect dust on a shelf, I believe this tool can be still be very beneficial in two patient populations.

One, is the high risk surgical patient to optimize fluid management.
This strategy is currently termed "Goal directed Intra-operative fluid administration".

Fluid overload during surgery has been associated with [3]:

-Increased length of stay
-Bowel wall edema
-Edema organ dysfunction
-Adverse outcomes

Additionally, patients receiving fluid and hemodynamic optimization during surgery are at an decreased risk of renal impairment. 

The second type of patient that may benefit from minimally invasive cardiac output monitoring is the critically ill cardiovascular patient.

 With these patients the ICU physician is always questioning [4]:

-"Is the patient's pre-load sufficient to obtain adequate Cardiac output"?
-"Does the patient need volume (fluids) or forced diuresis"?
-"What is the patient's cardiac function"?
-"Does the patient need inotropes or pressors"?

In these patients'  not optimizing fluid management can be detrimental. 


All devices calculate cardiac output based on the traditional equation:


CO = Cardiac Output
SV= Stroke volume
HR= Heart rate 

However, each device uses a proprietary method to calculate stroke volume or a modification of the Fick principle. Below is a table I created that compares and contrast three different pulse contour analysis devices.  

Image 2: Table comparing Pulse Contour Analysis Devices.

For more information on Arterial Waveform Analysis Devices one can visit the Society of Critical Care Medicine and take the online course "Less-Invasive Hemodynamic Monitoring" [5]. 


3. Optimization of the High Risk Surgical Patient. SCCM, lecture 2014

4. Transpulmonary Thermodilution. SCCM, lecture 2014. 

Thursday, June 19, 2014

ASV Behind the Scenes

The advantage of using Adaptive Support Ventilation (ASV) is that it automatically enforces the three primary clinical goals of mechanical ventilation, which include safety, comfort, and liberation.

To accomplish these goals ASV uses rules to set lung protective boundaries. 
Many of these rules are out of view from the device operator and are not affected by operator selection of inputs. The rules fall into two categories 'hard rules' and 'soft rules' or a combination of both types.

A Hard Rule is a pre-set limit which is unaffected by the operators interaction or by measured patient lung mechanic values (a "behind the scene" action). An example of this is the minimum & maximum mandatory breath limits and I:E ratio limits.

A Soft Rule is a limit based on an operator input and/or measured values of the patients respiratory mechanics. An example of this is the minimum & maximum inspiratory pressure threshold, which is determined by the operator directly setting the PEEP (affects lower PIP threshold) and the ASV pressure limit (affects the high PIP limit).

These rules are similar to techniques used by the experienced device operator, in which one uses to optimize ventilator settings. Now the less experienced device operator can provide the same standard of care as a seasoned practitioner in regards to enforcing the clinical goals of mechanical ventilation.

In upcoming blog posts and YouTube videos I will be presenting the the ASV rules in more detail.


Richey, S. (2010). Adaptive Support Ventilation: Guidelines  Standards for Using ASV. 

Thursday, February 27, 2014

ASV & ABGS: Adjusting %Min Vol Based on Arterial Blood Gases

Adjust %Min Vol setting during ASV in regards to ABG analysis

I often get asked how do I adjust my settings during Adaptive Support Ventilation based on my arterial blood gas (ABG) results.
 Above is a snap shot of a flow chart from my new ASV guide I'm currently working on. 
This chart provides a brief overview of adjusting the percent minute volume setting based on ABG results, the guide will provide more details. 


Monday, February 3, 2014

A Synopsis of Strategies in Difficult Intra-Operative Ventilation

Image from:

“Strategies in Difficult Intra-Operative Ventilation” was a continuing education course originally presented at the 2012 American Academy of Anesthesiologist convention. 

Now the course is available online through the ASA website for continuing education units. I would not recommend this course for the ICU practitioner because it overviews strategies that we practice daily or weekly, however for the anesthesia provider that is not familiar with lung protective strategies the course may be beneficial. 

Below is a synopsis of the course and a hyperlink to the website. 

Tuesday, January 7, 2014

What the Sales Guy Won't Tell You. Why You Won't Save $200,000 in Anesthetic Agent

In a previous post "How to Save $200,000 in Anesthetic Agent" I demonstrated how one anesthesia department could save close to a quarter of a million dollars by changing efficiency. I presented this many times using a mathematical modeling tool (Anesthesia Agent Analysis. S. Richey & R. Hazlett)  a colleague and myself created. 

Anesthesia Companies have used this same modeling in their marketing and device claims in regards to saving anesthetic agent. 

Example 1: Draeger Medicals "Low Flow Wizard" 
This is a decision support tool to help practitioners feel comfortable with using low to minimal flow anesthesia. 

Example 2: GE Healthcare's "ecoFlow"
This is GE's product to compete with & similar to the Low Flow Wizard (Draeger's was released first).


However, these tools are not novel. 

Dr. James H. Philip, the creator of "Gas Man" [1] has been a advocate, and teacher of minimal flow & closed system anesthesia for almost two decades. 
Dr. Philips software & courses demonstrate that one can provide minimal flow anesthesia using any modern day anesthesia delivery system, not just the Draeger Apollo or GE Avance with ecoFlow. 

The key factor in minimal flow anesthesia is patient safety, which translates to patient monitoring, which is not accomplished by the Low Flow Wizard or ecoFlow. These tools only look at the anesthesia device (gas uptake & system leaks) not hemodynamic status, metabolic demand, SpO2, EtCo2, rebreathed gas, etc. 

Additionally, the medical device companies marketing claims provide a false prediction of actual cost savings related to decreased anesthetic agent usage. 

In the following post I will present why you will not obtain these savings.

Thursday, December 5, 2013

Why I Do Not use Draeger Ventilator Simulators

I get asked often why do I not use other simulators in my videos.
Specifically the Draeger ventilator simulators.
It is very simple, they cannot perform the functions I need to teach modes of ventilation & pulmonary mechanics as demonstrated in the video. 

Saturday, November 16, 2013

Adaptive Pressure Control Ventilation Video Series

After finishing my videos on the mathematical models of PC-CMV, I decided to create videos on Adaptive Pressure Control (APC) ventilation.

These videos compare and contrast between APC, VC, & PC during changes in pulmonary dynamics & various patient conditions/ interactions.

Tuesday, November 12, 2013

Incorporating Proportional Assist into Ventilator Protocols

Image 1: PAV+ Work of Breathing bar. 

PAV+ may be used for the initial mode of ventilation during the acute phase of mechanical ventilation. However, from my experience I have had the most success and efficiency with PAV+ utilizing the mode to rest patients after a failed spontaneous breathing trial. After reviewing the literature it is still unclear the best way to wean or liberate a patient from PAV+. However, a traditional T-piece trail has been supported by many peer reviewed journals, so at my institution we still use a 30 minute to one hour T-Piece trial to screen patients for extubation.
How to incorporate PAV+

Tuesday, November 5, 2013

The Fastest Ambulance on TED

Whats in your pockets? Are you a Prepper or Macgyver?

In a previous post (The RT Hoarder) I mention that I carry very little on me when I'm at work. 
Yes, I believe in being prepared, however I try to practice the "Macgyver" philosophy [1], versus the "Dooms Day Prepper" mentality [2].

This post presents my Everyday Carry (EDC) [3] from when I first started in the field of respiratory therapy to what I carry now. I will describe "what is in my pockets" and why, also notice the progression throughout the years.

What items do I get rid of & what do I always need to practice the profession?

EDC as a RT student & new graduate.