Basic Ventilator concepts

[ccfems540]

Does anyone know of a website that can explain basic ventilator concepts and the physiologic effects?

 

[VentMedic]

Does anyone know of a website that can explain basic ventilator concepts and the physiologic effects?

You have asked about a very broad topic. How about narrowing it down to what you need specifically?

What type of ventilator?

ATV?

Something slightly more sophisticated like the Eagle 754?

Pulmonetics LTV?

What type of application?
Ventilating the almost dead from the field for 911 EMS?
CCT or Specialty where you may have to translate the settings of an ICU to your transport ventilator?

What type of patient? Age group?

Every patient and application is different and every ventilator mode, and the are many, will have a different effect.

The type of ventilator you use will also influence your settings and protocols for sedation. The flow, demand valving, sensitivity, internal or external PEEP and internal turbine capability all play an important role and will vary greatly from on machine to the next especially when it comes to portable ventilators. The many different machines will also have different terminology for similar modes but somewhat different by the factors I just mentioned.

Thus, it is difficult to advise you on a good site as there are textbooks just covering how the many different ventilators work and more textbooks covering some of the modes but not all since technology in medicine as well as the applications change and are constantly evolving.

 

[alphatrauma]

Google rocks!

Does anyone know of a website that can explain basic ventilator concepts and the physiologic effects?

try this for starters

Ventilator Management

 

[VentMedic]

try this for starters

Ventilator Management

That is a very generic article. Be very, very careful when just pulling an article off the internet and trying to adapt it to a transport ventilator.

This paragraph from that article is probably one that supports my statement best.

Many different strategies of positive-pressure ventilation are available; these are based on various permutations of triggered volume-cycled and pressure-cycled ventilations and are delivered at a range of rates, volumes, and pressures. Poor ventilatory management can inflict serious pulmonary and extrapulmonary damage that may not be immediately apparent.

The paragraph below and definition of AC and CMV will not work on all ventilators as the terminology varies as do the modes although they classify them as the same here. Many ventilators are manufactured in Europe which also complicates those learning the terms and their modes may be called the same or even similiar but are very different in delivery due to the design of the values and internal tubine or compressor.

Assist-control ventilation
The ventilator delivers preset breaths in coordination with the respiratory effort of the patient. With each inspiratory effort, the ventilator delivers a full assisted tidal volume. Spontaneous breathing independent of the ventilator between A/C breaths is not allowed. As might be expected, this mode is better tolerated than CMV in patients with intact respiratory effort.

The paragraphs listed below are outdated and just plain misleading. I can not think of where SIMV has even be put forth in the literature as a primary mode during the last 20 years. It had its place in the early 1980s but like the MAST, new evidence is found that leads us to a better understanding of the methods used. Thus, that leaves IMV as a very old mode that few in medicine who have less than 10 years of experience may have even encountered. Of course there are a couple of cheap transport machines that function as an old IMV machine and thus, I hope you can use a lot of sedation and paralytics.

Intermittent mandatory ventilation
With intermittent mandatory ventilation (IMV), breaths are delivered at a preset interval, and spontaneous breathing is allowed between ventilator-administered breaths. Spontaneous breathing occurs against the resistance of the airway tubing and ventilator valves, which may be formidable. This mode has given way to synchronous intermittent mandatory ventilation (SIMV).

Synchronous intermittent mandatory ventilation
The ventilator delivers preset breaths in coordination with the respiratory effort of the patient. Spontaneous breathing is allowed between breaths. Synchronization attempts to limit barotrauma that may occur with IMV when a preset breath is delivered to a patient who is already maximally inhaled (breath stacking) or is forcefully exhaling.

The initial choice of ventilation mode (eg, SIMV, A/C) is institution and practitioner dependent. A/C ventilation, as in CMV, is a full support mode in that the ventilator performs most, if not all, of the work of breathing. These modes are beneficial for patients who require a high minute ventilation. Full support reduces oxygen consumption and CO2 production of the respiratory muscles. A potential drawback of A/C ventilation in the patient with obstructive airway disease is worsening of air trapping and breath stacking.

This is also not a current article since the term "Swan-Ganz" is still used.

This paragraph below also has some very deceptive information.

An initial TV of 5-8 mL/kg of ideal body weight is generally indicated, with the lowest values recommended in the presence of obstructive airway disease and ARDS. The goal is to adjust the TV so that plateau pressures are less than 35 cm H2 O.

We do not start at the lowest which would be 5 ml/kg even for ARDS. If you look up the ARDnet site, you will see we start at 8 ml/kg and check the plateau pressure. You will also find several articles about the complications of low volume ventilation. The article also fails to discuss the amount of PEEP, pressors, sedation and paralytics required to run a low volume protocol.

For the next paragraph it mentions very little about minute ventilation and if you are running a low volume protocol, you may need to use a rate of 30 -35. It also doesn't tell you that if you give only 5 breaths/minute to an asthmatic, that patient will have to be sedated and paralyzed. That is also an outdated methods as newer technological advances starting over 25 years ago have reduced the need for such extremes and the overall use of paralytics.

Respiratory rate
A respiratory rate (RR) of 8-12 breaths per minute is recommended for patients not requiring hyperventilation for the treatment of toxic or metabolic acidosis, or intracranial injury. High rates allow less time for exhalation, increase mean airway pressure, and cause air trapping in patients with obstructive airway disease. The initial rate may be as low as 5-6 breaths per minute in asthmatic patients when using a permissive hypercapnic technique.

The next paragraph definitely needs more explanation. There are also some transport machines that barely hit 40 liters per minute. The authors also forgot to mention the flow rate for PCV and PSV which are very different.

Inspiratory flow rates

Inspiratory flow rates are a function of the TV, I/E ratio, and RR and may be controlled internally by the ventilator via these other settings. If flow rates are set explicitly, 60 L/min is typically used. This may be increased to 100 L/min to deliver TVs quickly and allow for prolonged expiration in the presence of obstructive airway disease.

For the next paragraph, if the authors had bothered to actually look at the ARDS studies that are on the ARDSnet site, especially since they have advocated for the low volume stategy, they would have known more about how PEEP goes with the concept. It has been extensively studied for several decades and the graphic packages available even for transport ventilators help us determine appropriate PEEP levels. Which brings up another very important issue. Just like being able to read waveforms on ETCO2 monitors, one should understand ventilator wave patterns if they do CCT for critically ill ICU patients.

Positive end-expiratory pressure

PEEP has several beneficial effects and may be clinically underutilized. Research underway is examining the utility of high (>10 cm H2 O) PEEP in disease states ranging from COPD/asthma to ARDS. PEEP has been found to reduce the risk of atelectasis trauma and increase the number of "open" alveoli participating in ventilation, thus minimizing V/Q mismatches. However, note that in disease states such as ARDS, the degree to which alveoli function has been compromised varies tremendously within the lungs and there is no single "ideal" PEEP appropriate for all alveoli; rather, a compromise PEEP must be selected.

Use solid sources for your information and start with what you don't know about respiratory diseases. Then, do your search based on your ventilator and applications. You can also go to the RT department of a college or hospital for more personalized help with maybe some hands on.

If you provide some answers to the questions I asked earlier, I might be able to direct you to some appropriate sources.

 

[46Young]

I'll assume that the OP wants some general understanding on how various txp vents work, how to troubleshoot, so on and so forth. I asked that myself a while ago with this thread:

http://www.emtlife.com/showthread.php?t=12687&highlight=vent+lecture

Medic classes give hardly any attention to vent ops. Most of what we learn is on the job, or through a lame inservice. The OP would probably like a deeper understanding, as it pertains to paramedic level IFT ops.

 

[redcrossemt]

Medic classes give hardly any attention to vent ops. Most of what we learn is on the job, or through a lame inservice. The OP would probably like a deeper understanding, as it pertains to paramedic level IFT ops.

Yeah, seriously. Amen to the lame inservice remark.

My regional medical control authority requires only 4 hours of training on ventilators (plus other training) to be able to run at the "Critical Care" level.

The UMBC CCEMTP class was interesting and got my feet wet in ventilator technologies, but still doesn't have much.

To the OP, if you are interested in furthering your career and learning a little about a lot of CC topics, check out a UMBC CCEMTP class. If you just had some simple questions about ventilators, you can search google, or ask your neighborhood RRT or ICU/CC MD/DO.