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Monday, January 7, 2008

Negative pressure ventilation come full circle?

The respiratory therapy profession basically began with the iron lung, or negative pressure ventilator. Wouldn't it be ironic if this type of therapy made a comeback, and negative pressure ventilators were the wave of the RT future.

The latest negative pressure ventilator is called the Biphasic Cuirass Ventilation, and one such ventilator is the Medivent Hayek RTX Biphasic Cuirass Ventilator made by Medivent International, and involves a simple shell placed over the patient's chest, instead of over the entire body as was the case with the inconvenient iron lung of the 1950s.

I can certainly see some advantages of the cuirass ventilator. For one thing, you would avoid the barotrauma associated with positive pressure ventilators and the risk of pulmonary infection because you wouldn't have a tube in the patient's airway nor a tracheotomy.

According to this company, since negative pressure ventilation is "more normal," it would be more comfortable for the patient, and allow RTs greater control over tidal volume and respiratory rate, and, ultimately, make weaning easier.

Likewise, the company claims that the vent "helps to maintain and redevelop the respiratory muscles which often wither and waste with respiratory failure and mechanical ventilation (and also) improves cardiac output."

Here are some more uses, as listed on Medivent International's website:

  • It can be used as an aid in weaning a patient from conventional positive pressure vents, particularly those difficult to wean patients.
  • Assists patient with removal of secretions, and is used as a glorified chest physiotherapy machine. It has been used in this way for Cystic Fibrosis patients and COPD patients.
  • Can be used similar to BiPAP to provide treatment for patients before their condition deteriorates, and thus requiring intubation.
  • Can be used as an at home vent and in hospitals for neuromuscular diseases and head and spinal injuries.
  • It has been used on post-operative patients
  • Can be used on Asthma and COPD patients
This type of therapy would be better for the patient in that they wouldn't have to have a tube in their throat, which can be very uncomfortable and annoying, and requires, most of the time, that sedative be used to make the patient more comfortable, or to forget the event all together. Sometimes this can make weaning difficult.

However, despite these claims, I'm not convinced this machine would be anything more than a glorified and expensive BiPAP machine, of course without the annoying and often difficult to get used to nasal or face mask.

I can also think of some cases where this type of ventilator would not be beneficial, especially if you had excessive secretions or pulmonary edema. Of course, even in these cases, nasal tracheal suctioning would always be an option.

However, this type of breathing apparatus would not protect the patient's lungs from aspiration, may not allow for adequate removal of CO2, and may not be effective for obese patients. In these cases, RTs and doctors would have no choice but to opt for the more conventional positive pressure ventilator.

Wikepedia has a nice write up about the curiass ventilator, but it would appear someone from Medivent International transcribed the copy here from their own website, as it's basically the same information not even reworded.

Anyway, that's my review of this ventilator based on some quick research I did. I wonder if this has been used anywhere in the U.S. If so, I wonder what the general opinion of this innovative therapy is, as so far most of what I've learned regarding this vent has been from the company.


Michelle said...

When I was admitted last year for retaining too much CO2, the doctors initially put me on BiPap. Then they had me try the Cuirass for about a week. At first, I liked it better because I didn't have to deal with a mask. My sides became sore though, no matter how many times the straps were adjusted. And in my case, the Cuirass didn't bring down my CO2 very much.

Now I'm fine and just living with a trach (plus ventilator at night) :)

Freadom said...

Thanks for responding. I had no clue that the cuirass was even used in reality. What did you think of it. What kind of ventilator do you use? What's your illness? I'm very curious if you care to share more.

Terry at Counting Sheep said...

Interesting concept. I'd love to see it in action.

Breathingthroughschool said...

Interesting post. I had no idea they even used Curiass ventilators anymore. It would be interesting to see if they are even in use anywhere in North America.
In regards of what Michelle said, they don't look they would be very comfortable especially when the lady with CF was using it in their promotional video.

Gary Mefford RRT said...

Been a fan of this blog for a while, just now found this older posting. I am the Clinical Coordinator for Hayek Medical. I think you would be very surprised at what the RTX and Biphasic Cuirass Ventilation is capable of. It is in the US, but it is still quite rare. It has many indications, improves CO2 clearance and oxygenation as well as provides a very potent means of airway clearance that includes a cough assist. It can be used adjunctively with PPV also to assist weaning and improve oxygenation pulmonary perfusion and cardiac output. Anyone who would like to learn more can contact me at The Wikipedia article is not bad, but I believe it characterizes BCV as a mode that can only work independently of PPV which is incorrect. Patients with ET tubes and trachs even while on PPV can benefit from BCV. It is better if it is used early enough to prevent the need for an artificial airway, but if needed it can still improve the outcome. It it generally very comfortable for the patient. Every patient that has used BiPAP acutely that has used the RTX prefers BCV. Here is a link to one of the more general articles on its uses. Some of the functions on the international version of the RTX are not yet approved in the US, but essential functions are the same.

Rick Frea said...

Thanks Mr. Mefford. I didn't know you had a blog. I'll add it to my list. I forgot about this old post. Perhaps -- and with a little help from you -- it's time to do an update. Thanks again. Rick.