ERRORS CONCERNING NEBULIZATION WITH BIPAP AND MECHANICAL VENTILATION

LUNGLORD  REFUTATION:

INFLUENCE OF TYPE, POSITION AND BIAS FLOW ON AEROSOL DRUG DELIVERY IN SIMULATED PEDIATRIC AND ADULT LUNG MODELS DURING MECHANICAL VENTILATION

Aru Ari Phd RRT PT CPFT,   Orcin Telley Ataley Phd PT,   Robert Harwood MSA etal

Respir Care 2010;55(7):845-851

The above study should be scrutinized concerning several key assumptions regarding the use of bronchodilators on ventilators and Bipaps for the adult clientele.

LIMITATION ONE

ALL TESTS IN THE STUDY WERE PERFORMED ON CLOSED CIRCUIT VENTILATOR CIRCUITS HEATED TO THIRTY FIVE DEGREES CENTIGRADE

DEVIATION FROM CLINICAL PRACTICE

NO INFORMATION IN THIS STUDY CAN BE APPLIED TO BIPAPS SINCE THEY ARE NEITHER TOTALLY CLOSED SYSTEMS,  HAVING BOTH ORAL LEAKS AND MECHANICAL CIRCUIT LEAKS, NOR ARE THEY USUALLY HEATED TO 35C  AT ANY TIME EXCEPT FOR TRACHEOSTOMY.            

RATIONALE FOR ARGUMENT

Bipaps are used dry at first in their administration. Some facilities deem that the first four hours of Bipap use is a temporary use and therefore the expense of humidification is unwarranted. Once a chronic need for ventilation is deemed appropriate, room air temperature passover humidification is used to partially bring the dry gas towards the moisture content of the room. In many institutions, such as at LUNGLORD’s facility, Bipaps are never heated regardless of length of patient stay, a point for discussion at another venue. What is gained in humidity is lost in patient compliance. Obtunded people reject our ventilatory lung sauna, though LUNGLORD  does try to sell the idea as a lung spa to those that are dioxide narcotic.

Reflect on this idea. Relative humidity in most hospitals is regulated to very low levels to retard bacteria growth. Therefore, it is a reasonable conclusion that, a mix of bone dry source oxygen and relatively dry entrained gas passing momentarily through a cold chamber will achieve only minimal amounts of humidity. 

A fair question concerning an RCP’s goal of highest possible reason and best practice should be asked here.

Consider. When we’ re giving a conventional nebulizer treatment, the mist disappears once it has traveled four to eight inches from the cup. Why? The very dry air robs the mist of moisture by evaporation, reducing particle size until the medicine is far below optimal size, in fact has an infinitesimal particle size. 

How much of this medication would be at optimal particle size after traveling seventy two inches through a corregated ( thus turbulent) BIPAP circuit or a ventilator circuit where it is well tumbled in dry gas?

Is any of the medicine at proper size for absorption?

LUNGLORD believes it is exceptionally imprudent and unreasonable that these questions weren’t asked by these Phds.

How much of the medicine gets past the pilot hole built into the circuit? 

How much is lost in the passover or heated humidifier?

We know that particle sizes that are too small are exhaled and not absorbed at all because they lack enough mass for inertial impaction.  

CONCLUSION:  NONE OF THIS INFORMATION AS PRESENTED BY THE AUTHORS  APPLIES TO THE EFFFICACY OF UNHEATED VENTILATORS AND BIPAPS.

LIMITATION TWO

THE FILTER USED TO COLLECT THE BRONCHODILATOR IS AN ABSOLUTE FILTER, THAT IS, 100% EFFICIENT AT CAPTURE OF ALL PARTICLES COMING TOWARDS IT.

LOGIC ERROR: STUDY DEVIATES FROM THE PHYSIOLOGICAL REALITY COMMON  TO ALL HUMAN ANATOMY

NO BIOLOGICAL SYSTEM OF THE BODY IS 100% EFFICIENT. ONLY PARTICLES LESS THAN A CERTAIN SIZE CAN GET INTO THE LUNG.  FURTHER, THE LUNG ONLY RETAINS PARTICLES IN A CERTAIN MICRON RANGE.  THIS STUDY IS OF LIMITED VALUE IN THAT IT DOES NOT SPECIFY WHICH SIZE PARTICLES AND THEIR PERCENT OF THE WHOLE ARE ARRIVING AT THE FILTER.

RATIONALE FOR ARGUMENT

Obviously, cigarette smokers exhale smoke, these particles too small and of insufficient mass to impact on the bronchial or alveolar walls.  Larger particles rain out in the upper airway resulting in stained teeth. Likewise with these aerosols, particle size must be right sized to impact and to prevent exhalation. The study used HCL to remove and sluice all albuterol from the filter. It was then weighed without regard to particle size. Only the crude amount was considered. 

This lack of specificity results in a lack of utility. 

Had the authors used absolute filters that would send the gas first through  a 5 micron,  then 4, then 3,  2, 1, .5,  .25, .15 and <.15 particle sizes in successive filter traps, the whole premise  of the study might have illuminated the elephant in the room.

The elephant here is that aerosol particles robbed of their liquid suspension have an unspecified mass and their particle size is far out of the specified range. 

True the meds are captured in the 100% filter, but this is sleight of hand.  This is a huge confidence distractor and reflects sloppiness on the part of the researchers who would have certainly known that the useable particle size would be an important consideration since is represents efficacy of retention of the lung in the lung, especially in any environment less than 37c.

An argument can be made that MDIs also aerosolize anhydrous albuterol, therefore what is the difference.  Simply, these MDI meds are formulated with HFAs and CFCs previously to a high degree of precision to achieve proper particle size.  No description of particle size is being offered by this study.

SUMMARY

Colleagues, is it not reasonable that the more proximal the HHN is to the patient, the more medication they will receive both in volume and in proper particle size, having avoided all these losses?   

LUNGLORD would humbly recommend that in the future all nebs be inserted in the circuit with a spring loaded T piece, that is, between the Bipap mask and the pressure sensor/pilot hole, as a matter of policy and practice. The spring loaded T piece is essential for safety, for should the neb disconnect, no pressure would be generated in the circuit.

Let us abandon the both convenient and highly inefficient practice of placing the HHN on the main flow filter where it comes out of the ventilator or Bipap, this some six feet from the patient.

The medicine our patient’s need to reduce their WOB should be placed as proximal and as close to an ideal particle size as possible.  This improvement in practice might well be the difference between intubating our COPD, CB, and asthmatic clients.  Consider the cost and morbidity such a change in your methodology might make to your clients and their LOS.

 What is factual and correct in the study is that the inspiratory limb can serve as a spacer, a plenum for the neb during exhalation, the mist building in volume and moving closer to the Y during this time, that is if the neb is backed away from the Y a foot or so and the circuit is heated. For this information, LUNGLORD is grateful to the researchers.

2 responses to “ERRORS CONCERNING NEBULIZATION WITH BIPAP AND MECHANICAL VENTILATION

  1. I am a Resp. therapist and I have a question concerning humidification with bipap. Also, From what I just read and from how I understand it, if giving a pt a HHN, it should be placed between the mask and the pressure sensor/pilot hole. I though that adding in the spring t piece at that spot, it makes the exhalation port farther from the mask. I thought that was NOT suppose to be farther from the pt? I was also wondering, would an HME be able to be used with a bipap? Thanks for taking the time to answer my questions. Thank you!

    • You are correct in your statement that the HHN should be placed as proximal to the mask as possible, that is between the mask and the pilot hole. moving the distance of the proximal port two inches is not a factor. You can do as LL does. Try a bipap mask on and put the spring loaded T in. I felt no difference in sensitivity.

      In the article the nebulizer was placed far upstream from the patient and so, as described in the criticism, most of meds are tumbled in dry, turbulent air, robbed of their particle size. After this a portion exits the gas into the humification chamber or out the port of last resort near the mask. This is not best practice. They get little if any meds.

      As for HME with a Bipap. These are contraindicated. Try breathing through an HME. There is resistance. Put an HME inline with your bipap trial when you wear the mask to test the nebulizer T above. There will be significant drag on your breath. It is a pleated filter of sorts. Once an HME is wet there is more resistance. If the patient is labored exhalation can be additional work. HME? Not reccomended. Get a humidifier like a Fisher Paykel or Concha to give the humidity you need. Good question though.

      LL

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