Wednesday, July 18, 2012

Vent Graphics Contest WINNERS

First, I would like to thank all my readers who entered the "Vent Graphics Contest" , I appreciate all of the efforts.

First Prize

John Priest

Equipment Used: Epiphan 

Image 1 & 2: Preventing auto-triggering.

Enter John 

A 2 year old 8kg female with restrictive cardiomyopathy presented to the cardiac ICU. The patient was intubated on day five of admission due to cardiopulmonary failure; respiratory support was maintained on PC-SIMV. Flow and pressure trigger were set to 1L/min and -2cmH2O respectively. No auto-triggering was observed. 

Heart function continued to deteriorate and on day fifteen a BiVAD was placed. The patient was not breathing and auto-triggering was detected almost immediately. In order to prevent auto-triggering, flow and pressure trigger sensitivities were set to 1.5L/min and -2.5cmH2O. As the patient recovered, chemical paralytics were lifted and the patient began making spontaneous respiratory efforts.

 It was technically difficult to set an optimal flow and pressure trigger in order to prevent auto-triggering while preventing dysynchrony and allowing spontaneous triggering. To determine the presence of spontaneous effort we turned the flow and pressure trigger to 10L/min and 10cmH2O respectively. If a negative deflection in pressure was associated with a positive deflection in flow (fig. 1), it was concluded that the patient was making spontaneous efforts. 

Upon making this determination, it was found that a flow trigger of 2L/min and pressure trigger 2.5cmH2O prevented auto-triggering but allowed adequate patient triggering (fig. 2).The patient was assessed for extubation and was extubated on day 26 to a nasal cannula".

 "This case illustrates the impact of a BiVAD on the respiratory system and highlights the importance of discerning patient effort from auto-triggering. Because VADs are often implanted within the chest, it is possible for the pumping action of the VAD to cause changes in intrathoracic pressure. 

Although these changes are small, they may be enough to cause flow changes in the airway, leading to auto-triggering, hypocapnea, and respiratory alkalosis. The ability to specifically determine spontaneous respiratory efforts in this case, ensured appropriate ventilator management in a patient at high risk for auto-triggering and patient-ventilator dysynchrony.

Second Prize

Sean Kirby

Equipment used: Ventview & screen capture software

Image 3: Screen Shot of Mandatory Minute Ventilation (MMV) demonstrating rapid shallow breathing. 
Enter Sean

We sometimes use Mandatory Minute Ventilation (MMV) at our facility to help promote a transition to spontaneous breathing. This can be great for post cardio-thoracic or vascular surgery recovery however is not optimal for every patient.

 Some people believe that this is a great mode and that it is safer then traditional modes, since the operator can set a minimum minute ventilation. However, the machine does not know what breathing pattern met the minute ventilation requirement. 

Example: Set minute ventilation threshold = 5 lpm

Frequency 5 x 1000 Vt

Frequency 50 x 100 Vt

Frequency 100 x 50 Vt

These breathing patterns would all be acceptable to the machine. 

Image 3 (above) demonstrates this. This patient had rapid shallow breathing, a measured frequency of 49 & a tidal volume of 140 ml. Conversely, this met the minimum minute ventilation setting so no mandatory breaths were delivered. 

The patient started to get fatigued, not able to meet the minute ventilation requirement so the ventilator started to provide mandatory breaths. Shown in the below image (image 4). 

Image 4: Patient is unable to meet minute ventilation threshold, so the ventilator provides control breaths. 

Scott- This is a great example on how practitioners may believe one mode may be used on many different types of patients, however there are limitations with every mode. 
MMV can be basically a control mode, IMV mode, or spontaneous mode. It can be one of the worst modes for patient comfort. 
...I will go over this mode in detail in the new book. 

Third Prize

Incognito (wanted to remain anonymous) 

Equipment used: iPhone

Image 5: Using both the patient monitor & anesthesia delivery monitor to evaluate patient comfort. 

Enter Incognito

This is an example of ventilator asynchrony and patient discomfort during general anesthesia. 
In the above image (image 5) you notice both the patient monitor & the screen of the anesthesia system. Ventilator asynchrony can be hard to distinguish from pain during surgery, so you have to use multiple tools for assessments. 

If you look just at the patient monitor (left side) you can see a high respiratory rate and heart rate, so this might be a indication of pain. The anesthesia provider could administer more anesthetics however this would decrease the patients ventilatory drive (however they can control the minute ventilation with the vent). 

Reviewing the right screen one notices a few things a high EtCO2 (74) & flow asynchrony (scooping/camel backing) in the green flow waveform. This patient had a very high inspiratory demand and the pressure control setting was not high enough. 

Right before the picture, the pressure control was only set at 10 cmH2O and the measured respiratory rate was in the high 30's. The pressure control was increased as well as the respiratory rate to promote patient comfort. 

Scott- this is a great example on how one has to use multiple assessment tools to optimize patient comfort. Additionally, one needs to know all of the asynchronies related to the ventilator mode they are using. Practitioners use pressure control due to its capability of delivery variable flow. However may not even consider the importance of the driving pressure as in the above example. The operator who solely just focuses on the delivered tidal volume will think that the patient is doing fine just because their tidal volume is adequate and may decrease the amount of pressure control, thus leading to distress then fatigue. 
...More detail in the new book.