# Negative Pressure Ventilators



## Lifeguards For Life (Dec 26, 2009)

Do any of you have any experience with negative pressure ventilators? Are they still in use, and what would indicate their use over positive pressure ventilators?


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## Akulahawk (Dec 26, 2009)

You mean modern-day equivalents of the old Iron Lung?

If so, it seems that there's still some in use. I have no direct experience with them though.


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## Lifeguards For Life (Dec 26, 2009)

Akulahawk said:


> You mean modern-day equivalents of the old Iron Lung?



yep. cuirass, pneumowrap, etc.

I think I recently found my answer,but hoping this thread may stimulate some discussion/debate.


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## Akulahawk (Dec 26, 2009)

Newer methods of negative pressure ventilation... Unfortunately, I've no experience with those.


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## Lifeguards For Life (Dec 26, 2009)

Akulahawk said:


> Newer methods of negative pressure ventilation... Unfortunately, I've no experience with those.



apparently there is still a demand for them in modern medicine. I have never encountered one myself though.

Negative Pressure ventilators(NPV) differ from Noninvasive Postitve Pressure Ventilators(NPPV), in the fact that they apply negative pressure around the chest wall, resulting in a negative intra-thoracic pressure, drawing air into the patients lungs.

From my reading, NPV is indicated for patients that can manage their own airway(patient can not have an artificial airway) who suffer from respiratory neuromuscular syndromes or as a "weening step" in removing patients from NPPV.

What would make a negative pressure ventilator, a more efficient therapy than Intermittent Mandatory Ventilation, synchronized Intermittent Ventilation, Pressure support Ventilations, or airway pressure release ventilations?


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## Lifeguards For Life (Dec 26, 2009)

types of NPV

Cuirass






Iron Lung





autopulse?


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## Lifeguards For Life (Dec 27, 2009)

this topic has been briefly discussed in the following thread:
http://emtlife.com/showthread.php?t=14649&highlight=negative+pressure+ventilators

It contains more information.


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## Lifeguards For Life (Dec 27, 2009)

Lifeguards For Life said:


> What would make a negative pressure ventilator, a more efficient therapy than Intermittent Mandatory Ventilation, synchronized Intermittent Ventilation, Pressure support Ventilations, or airway pressure release ventilations?





> The iron lung is our first choice of treatment for several reasons. Patients with acute exacerbation of CRF often present inspiratory muscle weakness, rapid shallow breathing, and excessive CO2 retention. The iron lung improves the performance of respiratory muscles and restores sufficient respiratory compensation.16 Furthermore, many patients in the early phase of ARF are restless and do not tolerate NPPV with nasal or full face mask, whereas with the iron lung these patients receive ventilation effectively. Tracheobronchial secretions are often a problem in patients treated with NIMV and require efficient cleaning of the airways (with catheter or fiberoptic bronchoscope). This is achieved more easily when the iron lung is used.22 Noncontrolled studies232425 indicate a better survival rate when patients with COPD and ARF are treated with the iron lung vs IMV. Using controlled ventilation via iron lung, patients with COPD in hypercapnic-induced coma can be safely treated.26



Full article here:http://chestjournal.chestpubs.org/content/125/6/2217.full.html

complications associated with longterm intubation include: 
Sore throat
Laryngeal oedema
ETT sutured to trachea or bronchus Hoarseness
Laryngeal oedema Nerve injury
Aspiration of oral or gastric contents 
Superficial laryngeal ulcers
Laryngeal granuloma
Glottic and subglottic granulation tissue
Laryngeal synechiae
Vocal cord paralysis 
Tracheal stenosis
Tracheomalacia
Tracheo-oesophageal fistula
Tracheo-innominate fistula

All of the above can be avoided with Negative pressure ventilations.

When Negative Pressure Ventilations are not indicated, impracticable due to the subject’s characteristics or ineffective after 2 h of treatment, the use of intermittent positive pressure ventilation  may avoid endotracheal intubation.


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## TomB (Dec 27, 2009)

I think it's just not practical for the prehospital environment. One nice thing about PPV is that it works for a pneumothorax and it's beneficial for acute pulmonary edema. CPAP is already doing a great job keeping conscious and breathing patients with pulmonary edema off of the ventilator, for example.

Tom


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## Akulahawk (Dec 27, 2009)

I was thinking about one of the neg pressure devices that was liked from one of the threads here, and I had the distinct impression that for prehospital use, how the heck are "we" going to find the physical space to store 11 different sizes of chest pieces? It appears to work, but IMO, it takes a LOT less space to store 3 or 4 each of ETT sizes 3-9 than it would to store 11 of those chest pieces. Or for that matter, less space to store several different CPAP masks than it would to store those chest pieces. 

It would, however, be a good idea to at least be familiar with neg pressure devices so that if we encounter one in the field, we've got a better idea about how to deal with it.


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## piranah (Dec 27, 2009)

I must say I agree..It is just not practical, although knowing and understanding the mechanism might help you treat someone you may encounter in the field with this type of Tx....but in the field..PPV is what we can do.


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