Saturday, September 26, 2009

A High Frequency Oscillatory Ventilator Design For Use in Pandemics

This is a continuation of some of the ideas I expressed in a previous post on HFOV design. You can see it here: http://panvent.blogspot.com/2009/08/crisis-is-near-now.html

Some of the news items I have been reading say that there will be a particular shortage of high frequency oscillatory ventilators. Many ICU units do not have any or may only have one. This type of ventilator is required to care for patients with the most damaged lungs. Here is a little more information on a design for an HFOV. This is very preliminary. It surely needs more work. Someone would have to to build and test a prototype to determine if it is feasable.


What is HFOV?

An HFOV (High Frequency Oscillatory Ventilator) is an advanced ventilator design that is sometimes used in ARDS (Acute Respiratory Distress Syndrome) patients when a conventional ventilator will no longer provide adequate ventilation. Using a HFOV is considered a “lung sparing” technique.

When using conventional ventilators, the ventilation levels can be increased by increasing the percentage of oxygen fed to the ventilator, increasing the stroke volume, or increasing the rate or frequency. Other measures to improve ventilation can be increased PEEP (Positive Expiratory End Pressure) levels, reversed I/E (Inspiration/Expiration) ratios, methods to increase the average airway pressure, or even PLV (Partial Liquid Ventilation) has been tried, where a perflourocarbon solution (perfluorooctyl bromide) is put into the lungs to reduce lung damage without reducing oxygen transfer. ECMO (Extra Corporeal Membrane Oxygenation) is another method that can prevent damage to lungs by the use of high pressures and oxygen levels in conventional ventilation.

The HFOV can maintain a fairly high mean airway pressure, resulting in better ventilation without causing as much lung damage. With the high rates required for HFOV, each breath is less than the dead space in the lungs. There are various mechanisms that explain how it works (http://priory.com/cmol/hfov.htm), but it does work quite effectively. The breathing mechanism is similar to a dog panting at a high rate.


How HFOV Works

To make a HFOV work, you need to have a system that maintains a set average airway pressure and then have another device that oscillates this column of air at a desired rate, amplitude and I/E ratio. That’s the fundamentals of what it does.

Now to optimize this design you need to have a gas management system that controls the oxygen level, temperature, humidity and inlet pressure and flows to the HFOV device. We do not have to worry about designing these parts. They are all standardized respiratory equipment that is also used on conventional ventilators.

Other design considerations are that the air flow goes through the tubing in such a way as to optimize gas exchange, and we will also need other alarms to warn us of low or high pressures, improper rates and loss of supply gas. We may also want additional alarm systems that warn us of equipment failure modes. The tubing should be relatively non-compliant and the system should have minimal dead space.











Fig 1. HFOV design from IEEE Transactions on Biomedical Engineering
this link.

This design would be based mostly on the diagram in Fig 1. The controls and operator interface could be modeled to be similar to the 3100B from Sensormedics. The 3100B is the most commonly used HFOV for adults. Many RTs are already trained in its operation. By making the controls and alarms similar to the 3100B, it could be more easily deployed in a pandemic situation.

This is how the device in Fig 1 works:

  • A filtered, humidified air/oxygen mixture is fed into the feed tube near the ET (Endo Tracheal) tube. The flow rate is monitored and controlled by the mass flow meter
  • It travels down the tube towards the oscillator unit and exits via the servo controlled restriction valve.
  • The pressure sensor is that thing on the tube between the inlet and outlet ports. The electronics control system will receive this pressure signal and adjust the servo controlled restriction valve so that the average airway pressure is equal to the desired set point.
  • The pneumotach is not really required for operation. They have to do measurements for their study. Vacuum is not really required either, as average airway pressures will always be positive.
  • The oscillator is that plunger looking thing on the right hand side. It looks and works like a speaker in the 3100B but is really a special purpose built device. They call it the driver.
  • The plunger moves in and out at the desired rate, wave shape and amplitude as determined by the driver circuitry and the operator settings.
  • Now, you can see, that column of air is going to push and pull air in and out of the ET, which goes into the lungs. When the air comes out of the ET, the fresh bias flow gas will flush it away and out toward the servo controlled restriction valve. Fresh bias air is pushed into the lungs when the plunger moves toward the ET tube.
  • The oscillations of the plunger will change the instantaneous pressure in the tube positive and negative with respect to the average pressure.
  • The position feedback device improves the performance of the oscillator circuit and can also be used as a part of a safety system

Parts And Controls

I will group parts into 3 general categories.

  • Oscillator driver and driver circuit.
  • Sensor, actuator and associated circuitry.
  • Control and display system.

Oscillator Driver and Driver Circuit

For the oscillator driver we would want to use a big, high power subwoofer type speaker. It should be tough and able to handle high duty cycles and long periods of operation. It should have a metal cone to make it inflexible. We might have to glue a metal plate to the cone to make it more rigid. In order to reduce the dead space, we could make a mold of the front of the cone surface in resin or silicone with an air access hole drilled in the center to mate with the speaker cone assembly.


I am not certain how well a speaker will work though. There must be technical reasons why the designers of the 3100 use that design. Speakers, even subwoofers have a certain compliance and harmonic resonance built into them that is at a higher frequency than the rates we would need to use. It may require a large speaker using only a small portion of it's maximum designed excursion in order to minimize the effects on the output airflow pattern caused by the damping effects of the speaker cone suspension.

I am not sure if a position sensor is absolutely required, but something can be attached to the back of the cone if it is. Cooling may also be required. We could use lots of air and fans, or perhaps an active system using peltier devices.

The drive circuit would be a high output audio amplifier. I think it is best to use one designed for automotive use. These are generally more rugged, modular and can easily run on a 12 volt battery for electrical backup purposes.


Sensor, Actuator and Associated Circuitry

The sensor and circuitry would be similar to the one my son Jeff used in his ventilator design (Norman). It would convert the pressure pulse to a digital value encoded and sent on an RS232 port. We may wish it use more than one pressure sensor in order to provide redundancy for safety reasons. The pressure controller and alarm board would be a servo controlled valve and driver circuitry that operates by RS232. It could also house the audio alarm. This alarm would also engage and cause the valve to open if communications were lost. These circuits would have to be hand built unless there is a commercially available alternative.

Control and Display System

The control and display system would be a computer. It would probably be a PC and probably a laptop. A laptop has its own integral battery backup system. A program such as Labview can be run to show a display that looks similar to the control interface from the 3100B.

The instantaneous pressure readings received from the sensors could be integrated over time for display. The minimum and maximum pressures would be the peak recurring pressure extremes integrated over a short time interval. The average pressure would be integrated over a longer time period.

Operating parameters could be entered by selecting the appropriate box on the screen and entering the parameter via the keyboard. Alarms could also be displayed and color coded.

The computer would also output an audio signal to the speaker amplifier. This wave shape is normally a square wave pulse produced by a pulse circuit with variable duty cycle, frequency and amplitude in the 3100B. In our machine, we would have full control of the waveform via software. We could add pre-emphasis and custom wave shaping to the output to compensate for physical design shortcomings in the speaker and driver circuit or shortcomings in the housing and tube.
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Here are some resources if you want to learn more about HFOV.

Guidlines for the use of HFOV
http://priory.com/cmol/hfov.htm

HFOV guidelines from Stanford Hospital and Clinics
http://scalpel.stanford.edu/ICU/HFOV%20Guidelines.pdf

The use of HFOV in surgical patients.
http://www.surgicalcriticalcare.net/Guidelines/High%20frequency%20ventilation.pdf

Slide show of HFOV in the adult patient.
http://intranet.unchealthcare.org/hospitaldepartments/respiratorycare/practice-education-and-research/inservices-presentations/HFOV%20in%20the%20Adult%20Patient.pdf?searchterm=suction

University of Virginia experience with HFOV.
http://www.healthsystem.virginia.edu/internet/respiratory/Research/Retired/HFOVposter.pdf

ARDS and HFOV from Express Healthcare.
http://www.expresshealthcare.in/criticare2009/criticarefrontiers200912.shtml

Ventilation article from Answers.com.
http://www.answers.com/topic/mechanical-ventilation

Wickipedia Article about HFOV (please improve this)
http://en.wikipedia.org/wiki/High_frequency_ventilation

Spec sheet for the 3100B
http://www.viasyshealthcare.com/prod_serv/downloads/062_3100B_Spec_Sheet.pdf

Picture of a 3100 HFOV
http://commons.wikimedia.org/wiki/File:HFOV_3100A.jpg

Competency exam for 3100B operators.
http://www.viasyshc.com/smc/Reference/Critical_Care/Exams/3100BExam.pdf

Video showing operation of the 3100B
http://www.youtube.com/watch?v=jLroOPoPlig

Video showing initial operator calibration of the tubing set for the 3100B
http://www.youtube.com/watch?v=O2TaDyzxQAY

Thursday, September 24, 2009

HFOV design is Coming Soon

If you are looking for my ideas on using a dialysis machine to do ECMO treatments you should visit my previous post here: http://panvent.blogspot.com/2009/09/using-dialysis-machine-to-do-ecmo.html

A lot of people have been looking at my ECMO post, and I have now had somefeedback on it. I am in the process of making contacts with local people to see if they will look at my idea and discuss its merits and drawbacks. I am not sure what the best strategy is to pursue this, through the Pandemic Ventilator Project or by other means.

Another idea I am working on is to produce a design for an HFOV (High Frequency Oscillatory Ventilator) using readily available components. See here: http://panvent.blogspot.com/2009/08/crisis-is-near-now.html .
I visited an ICU and saw one in operation. I talked to an RT about how it works and how they manage the device (thanks, Sue). I have also obtained some technical details and specifications for existing designs. I have a few days free this weekend and I hope to work on this idea a little more. Hopefully I can have some more info on the blog for Sunday night.

Here I reprint an excellent article I read on Propublica.org. The original is available at:
http://www.propublica.org/article/flu-nightmare-officials-ponder-disconnecting-ventilators-from-some-pat-923
This article is one of the most comprehensive, balanced and well written pieces I have read so far on the subject of ventilator shortages in the H1N1 pandemic. I hope that it is widely read by the public, as well as planning and “deciding” individuals.



Flu Nightmare: In Severe Pandemic, Officials Ponder Disconnecting Ventilators From Some Patients
by Sheri Fink, ProPublica, September 23, 2009 6:15 pm EDT















With scant public input, state and federal officials are pushing ahead with plans that -- during a severe flu outbreak -- would deny use of scarce ventilators by some patients to assure they would be available for patients judged to benefit the most from them.

The plans have been drawn up to give doctors specific guidelines for extreme circumstances, and they include procedures under which patients who weren’t improving would be removed from life support with or without permission of their families.

The plans are designed to go into effect if the U.S. were struck by a severe flu pandemic comparable to the 1918 outbreak that killed an estimated 50 million people worldwide. State and federal health officials have concluded that such a pandemic would sicken far more people needing ventilators than could be treated by the available supplies.

Many of the draft guidelines, including those drawn up by the Veterans Health Administration, are based in part on a draft plan New York officials posted on a state web site two years ago and subsequently published in an academic journal. The New York protocol, which is still being finalized, also calls for hospitals to withhold ventilators from patients with serious chronic conditions such as kidney failure, cancers that have spread and have a poor prognosis, or "severe, irreversible neurological" conditions that are likely to be deadly.

New York officials are studying possible legal grounds under which the governor could suspend a state law that bars doctors from removing patients from life support without the express consent of the patient or his or her authorized health agent.

State and federal officials involved with drafting the plans say they have been disquieted by this summer’s uproar over whether Medicare should pay for end-of-life consultations with families. They acknowledged that the measures under discussion go far beyond anything the public understands about how hospitals might handle a severe pandemic.

By every indication, state and federal officials expect to weather this year’s flu season without having to ration ventilators. That assumes that the H1N1 virus will not mutate into a more serious killer, the vaccines against it and the other seasonal flus will continue to prove effective, and any dramatic surges in the number of patients in need of ventilators will occur in different parts of the U.S. at different times.

In recent months, New York officials have met three times with physicians, respiratory therapists and administrators to rehearse how their plan might play out in hospitals in a severe epidemic. In one of those “tabletop exercises,” participants suggested that the names of triage officers charged with making life and death choices among patients at each hospital should be kept secret. The secrecy would be needed, participants said in interviews, to avoid pressure and blame from colleagues caring for patients who were selected to be taken off life support.

When they posted their plan on the web in coordination with a video conference in 2007, New York officials promised to solicit public input. Since then, they have consulted with medical and legal professionals and other experts, but few members of the general public, and the plan has remained unchanged. They declined to make the comments they have gathered immediately available for review, and those comments are not published on the Health Department's Web site [1].

In the initial proposal, officials called public review “an important component in fulfilling the ethical obligation to promote transparency and just guidelines.”

The academic publication of the plan envisaged the use of focus groups to solicit comment from “a range of community members, including parents, older adults, people with disabilities, and communities of color.” Those have not been held.

Beth Roxland, the current executive director of the New York State Task Force on Life and the Law, said the ethicists included in the state's planning process focused largely on vulnerable populations. "Even if we didn’t have direct input from vulnerable populations," she said, "their interests have been well accounted for." Roxland said that public comment solicited when the ventilator plan was posted on the Health Department Web site was "sparse."

Dr. Guthrie Birkhead, Deputy Commissioner of the Office of Public Health for New York State said he wondered whether it was possible to get the public to accept the plans. "In the absence of an extreme emergency, I don’t know. How do you even engage them to explain it to them?"

Even so, other states, hospital systems and the Veterans Health Administration—which has 153 medical centers across all states -- have drafted protocols that are based in part on New York’s plan. The inclusion and exclusion criteria for access to ventilators, however, are different. For example, under the current drafts, a patient on dialysis would be considered for a ventilator in a VA hospital in New York during a severe pandemic, but not in another New York hospital that followed the State’s plan, which excludes dialysis patients. The VA’s exclusion criteria are looser because the patient population it is charged with serving is typically older and sicker than in other acute care hospitals. Different states, reflecting different values, have also established different criteria for who gets access to lifesaving resources.

The Institute of Medicine, an independent national advisory body, is expected to release a report on Thursday morning, at the request of the U.S. Department of Health and Human Services, that will recommend broad guidelines to help guide planners crafting altered standards of care in emergencies. At an open meeting held to inform the report on Sept. 1, participants described successful public exercises related to allocating scarce resources in Utah and in a Centers for Disease Control and Prevention study conducted in Seattle.

Questions about how hospitals would handle massive demand for life support equipment arose when New York state health department officials ran exercises based on a scenarios involving H5N1 avian influenza.

“They kept running out of ventilators,” said Dr. Tia Powell, director of the Montefiore-Einstein Center for Bioethics and former executive director of the New York State Task Force on Life and the Law, which was asked to address the problem. “They immediately recognized this is the worst thing we’ve ever imagined. What on earth are we going to do?”

Officials calculated that 18,000 additional New Yorkers would require ventilators in the peak week of a flu outbreak as deadly as the 1918 pandemic. Only a thousand machines would be available, the officials estimated. The state’s acute care hospitals in 2005 had about 6000 ventilators, 85% of which were normally in use. A moderately severe pandemic would have resulted in a shortfall of 1256 ventilators, health officials found.

In 2006, New York planners convened a group of experts in disaster medicine, bioethics and public policy to come up with a response. After months of discussion, the group produced the system for allocating ventilators. They first recommended a number of ways that hospitals could stretch supply, for example by cancelling all elective surgeries during a severe pandemic. The state has also since purchased and stockpiled 1700 Pulmonetic Systems LTV 1200 ventilators (Cardinal Health Inc., NYSE) -- enough to deal with a moderate pandemic but not one of 1918 scale.

Officials realized those two measures alone would not be enough to meet demand in a worst-case scenario. Ventilators were costly, required highly trained operators, and used oxygen, which could be limited in a disaster.

The group then drew up plans for rationing of ventilators. The goal, participants said, was to save as many lives as possible while adhering to an ethical framework. This represented a departure from the usual medical standard of care, which focuses on doing everything possible to save each individual life. Setting out guidelines in advance of a crisis was a way to avoid putting exhausted, stressed front line health professionals in the position of having to come up with criteria for making excruciating life and death decisions in the midst of a crisis, as many New Orleans health professionals had to do after Hurricane Katrina [2].

The group based its plans, in part, on a 2006 protocol developed by health officials in Ontario, Canada which relied on quantitative assessments of organ function to decide which patients would have preference for an intensive care unit bed. The tool, known as the Sequential Organ Failure Assessment (SOFA) score, is not designed to predict survival, and not validated for use in children, but the experts adopted it in light of the lack of an appropriate alternative triage system.

This summer, New York officials brought the state’s plan to groups from several New York hospitals for the tabletop exercises. They met behind closed doors to assess how hospitals might implement the proposed measures if the H1N1 pandemic turned unexpectedly severe this fall. In the fictional scenario, paramedics were ordered not to place breathing tubes into patients until physicians “can assess whether they meet the criteria to be placed on a ventilator.’’

Problems were immediately apparent. Dr. Kenneth Prager, a professor of medicine and director of clinical ethics at Columbia University Medical Center, was concerned about the lack of awareness of the plan among the larger public and the majority of the medical community. Societal input “is totally absent,” he said and called for more outreach to the public. “Maybe society will say, 'We don’t agree with your plan. You may think it’s ethically OK; we don’t.'"

The protocol, he said, would also place a great burden on clinicians charged with selecting which patients would be removed from life support. Physicians were concerned doctors involved in the legitimate and painful selection processes might be inappropriately construed as "death squads." “We facetiously dubbed them the ‘death squad’ or the ‘guys in the back room’,” Prager said. He envisioned family members breaking down and screaming when they found out their loved ones would be disconnected from ventilators. “It really is a nightmare.”

Even so, he felt that the plan – and its effort to save the greatest number of patients – was ethically appropriate. “If we don’t use triage, people will die who would have otherwise been saved,” he said, because a number of ventilators are “being used to prolong the dying process of patients with virtually no chance of surviving.”

Doctors at the exercises feared that they would be sued by angry patients if they followed the draft guidelines. “There’s absolutely no legal backing for physicians,” said Lauren Ferrante, a medical resident at Columbia University Medical Center. “Who’s to say we’re not going to get sued for malpractice?”

New York State law forbids doctors from removing living patients from ventilators or other life support except in cases where the patient has clearly stated such wishes, for example in a living will, or through his or her legal health care agent. Other sources of liability could come from federal and state anti-discrimination laws or claims of denial of due process.

New York officials said they were currently working out legal options for implementing the plans, such as gubernatorial emergency declarations or emergency legislation.

“You can take something today that’s not necessarily active and overnight flip the switch and make it into something that has those teeth in it,” said Dr. Powell, who served on the committee that drafted the plan.

Dr. Powell cautioned that it is critically important to maintain flexibility in the guidelines. Any rationing measures taken in a disaster must be calibrated to need and severity.

Guidelines can also promote investment in new technology, such as cheaper, easier to use ventilators, that would make rationing less likely. Already at least one company, St. Louis-based Allied Healthcare Products, is marketing a line of ventilators [3] specifically for use in disasters.

Some states, including Louisiana and Indiana, have adopted laws that immunize health professionals against civil lawsuits for their work in disasters. Other states, including Colorado, have drawn up a series of relevant executive orders that could be applied to address these issues.

Dr. Carl Schultz, a professor of emergency medicine at the University of California at Irvine and co-editor of the forthcoming textbook, Koenig and Schultz’s Disaster Medicine (Cambridge University Press), is one of the few open critics of the establishment of altered standards of care for disasters. He says the idea “has both monetary and regulatory attractiveness” to governments and companies because it relieves them of having to strive to provide better care. “The problem with lowering the standard of care is where do you stop? How low do you go? If you don’t want to put any more resources in disaster response, you keep lowering the standard.”
Federal officials disagree. “Our goal is always to provide the highest standard of care under the circumstances,” said RADM Ann Knebel , deputy director of preparedness and planning at the Office of the Assistant Secretary for Preparedness and Response, Department of Health and Human Services. “If you don’t plan, then you are less likely to be able to reuse, reallocate and maximize the resources at your disposal, because you have people who’ve never thought about how they’d respond to those circumstances.”

Tuesday, September 8, 2009

Using a Dialysis Machine to do ECMO

(There is more on ECMO on my Oct 1, 2009 Posting)


Many of the recent case reports indicate that sophisticated machines are required to treat the patients infected by the current novel H1N1 strain of influenza. Basic ventilators such as the existing Pandemic Ventilator Project designs may not be adequate for these H1N1 patients that develop ARDS. Pandemic Ventilator Project type units, however could possibly be utilized on other existing patients to free up more sophisticated equipment for patients requiring advanced therapies. I have also found a design for high frequency oscillatory ventilator that I posted (here).

Another technology that almost certainly will be in shortage during the pandemic is access to ECMO (Extra Corporeal Membrane Oxygenation) machines. ECMO machines oxygenate the blood directly using a gas permeable membrane. These machines can keep people with severely damaged lungs alive long enough for their bodies to repair their damaged lung tissues. There is very little of this equipment around. Many centers do not have any ECMO machines, or have only one.

Consider this:
An ECMO machine pumps blood from the patient, adds an anticoagulant, runs it past a gas exchange membrane to remove CO2 and add O2, regulates the blood temperature with a heat exchanger, removes air bubbles via drip chambers, checks incoming and return pressures, and has safety systems to ensure air is not infused, or pressure limits are not exceeded.

A dialysis machine pumps blood from the patient, adds an anticoagulant, runs it past a dialyzing membrane to stabilize electrolytes and remove toxins and fluid, regulates the blood temperature by controlling dialysate temperature, removes air bubbles via drip chambers, checks incoming and return pressures, and has safety systems to ensure air is not infused, or that pressure limits are not exceeded.

Hemodialysis System





































They are pretty similar eh?

Note that terminology for blood access is opposite in ECMO vs hemodialysis.

  • In ECMO, the port where the blood is drawn into the pump is termed the Venous line and the port where the blood is returned to the body is termed the Arterial line.
  • In Hemodialysis, the port where the blood is drawn into the pump is termed the Arterial line and the port where the blood is returned to the body is termed the Venous line.
  • In CRRT, (a form of hemodialysis) the port where the blood is drawn into the pump is termed the access line, and the port where the blood is returned to the body is termed the Return line.

The Hemodialysis picture is from METU BIOMAT, and the ECMO picture is from Medscape. (Note there is an error in the Medscape ECMO drawing, both pressure ports are named "Post-Membrane Pressure Monitor". The lower one should be named "Pre-Membrane Pressure Monitor) Note also that fluids and heparin are normally infused post pump in hemodialysis, as this method is usually considered a safer method. Air removal, and monitoring safety systems are also not in the ECMO picture. Both VV-ECMO and Hemodialysis can use a Jugular Venous Dual Lumen Catheter for access.

VA-ECMO vs. VV-ECMO
There are two types of ECMO. VA-ECMO or Venous-Arterial ECMO, has a more complicated method of attaching to the patients circulation system. VA-ECMO operation is similar to the use of a heart-lung bypass machine in that it replaces the function of both the heart and lungs of a patient. VV-ECMO or Venous-Venous ECMO, has a less complicated method of blood system access. It is done using high flow central line catheters similar to the ones used for dialysis. It replaces only the lung function of the patient.

Some patients with H1N1 are getting lung damage and progressing to ARDS. They may require ECMO because their lungs are so damaged that they can no longer provide enough gas exchange to maintain other body functions. A ventilator may not be adequate in these situations. The heart is not usually compromised. These patients could benefit from VV-ECMO if a machine was available. As stated earlier, available ECMO machines would probably be in very short supply during the pandemic.

You can see that the equipment for ECMO is very similar to the equipment required to perform dialysis. In fact CRRT or SCUF are sometimes done in order to control electrolyte and fluid volume levels by adding a dialyser to an ECMO machine without needing any additional equipment.

It seems to me that one could do VV-ECMO treatments using a dialysis machine with a diffusion membrane oxygenator attached in line on the blood tubing set. Some extra gas and oxygen regulators and controls may also be required. If a standard hemodialysis machine is used, it can be run at a low dialysis flow rate (available on machines such as the Fresenius 2008K) to run in a SLED (Sustained Low Efficiency Dialysis) mode continuously. I would like to hear comments from people that have worked with ECMO equipment to hear if they think this is at all feasible.

This Just in (Sept 15, 2009)

Article in New York Times about ECMO use in H1N1 pandemic and potential shortage of ECMO machines.
http://www.nytimes.com/2009/09/16/health/research/16flu.html

Lancet article about the efficacy of ECMO for severe influenza treatment.
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(09)61069-2/fulltext

Bloomberg article on using ECMO for near death swine flu cases.
http://www.bloomberg.com/apps/news?pid=20601080&sid=a3B182GF_auk

Belfast Telegraph article about ECMO
http://www.belfasttelegraph.co.uk/news/health/article14493762.ece;jsessionid=80D2A25F7E4033BF410D32971134D6DA?postingType=posting&mode=thanks&postingId=14493924

Update, Sept 18 2009

I have been thinking about this doing ECMO using a dialysis machine for a few days now. So far I have not had any comments either for or against on this blog.

I have done some further research into the equipment required for ECMO and some of the problems with ECMO therapies. It appears that maintaining systemic coagulation using heparin is sometimes a problem. Patients may not properly respond to the heparin therapy, they may have allergies, or there may be bleeding problems associated with systemic coagulation. These are problems that are also very common in hemodialysis and CRRT therapies. One solution to this problem is to use regional citrate anticoagulation. Citrate is infused into the blood circuit at the blood access port to initiate anticoagulation and calcium is infused at the blood return port to cancel the effect of the infused citrate.

This can be more complex than straightforward heparin infusion because the infusion of these chemicals also alters the calcium, pH, fluid volume and sodium levels of the patient. In CRRT and SLED therapies these parameters are monitored and controlled by adjusting the sodium and bicarbonate levels of the dialyzing and infusion fluids. Patient fluid volumes are also easily controlled by the dialysis machine.

Regional citrate anticoagulation has been shown to significantly extend the filter (dialyser) life compared to heparin coagulation by reducing clotting. It is sometimes used when the patient has HIT (Heparin Induced Thrombocytopenia). Regional citrate anticoagulation can also reduce other complications that would occur when using systemic anticoagulation protocols.

During a pandemic, it may be difficult to obtain enough membrane oxygenators to do ECMO. It is reasonable to assume that regional citrate anticoagulation could also extent the serviceable life of the membrane oxygenator by reducing clotting in the device. It will be important to make the best use of whatever supplies one has on hand. If it is indeed possible to use a dialysis machine to do ECMO, and also employ regional citrate anticoagulation with it, this could be a good way to save more lives with the possibly limited supplies available.

Here is a link to a PubMed abstract of an ASAIO journal article about using regional citrate anticoagulation with ECMO.
http://www.ncbi.nlm.nih.gov/pubmed/16883129?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum

Some More Info if this Intrigues You...

JAMA article shows that most patients with severe H1N1 that are treated with ECMO survive http://jama.ama-assn.org/cgi/content/full/2009.1535

Some general Info on ECMO systems and complications
http://www.anzcp.org/CCP/Clinical%20applications/ecmo.htm

Here is a link to a Patent for an ECMO system
http://www.google.com/patents/about?id=QoIcAAAAEBAJ&dq=ECMO

CDC info on the use of ECMO and CRRT on novel A H1N1 patients.
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm58d0710a1.htm



Response to the first comment by Anonymous (see below)

Thank you for your comments. I have been waiting to get some feedback on this issue. Just to clarify, ELSO is Extracorporeal Life Support Organization centered at the University of Michigan.

Now you have question about the origin, purpose and legitimacy of the Pandemic Ventilator Project. It was started on Feb 22, 2007 to promote alternative methods of supplying additional ventilators during a pandemic. In order to reduce the death toll of people either ill from a pandemic or those who would be denied life support so that the ventilator they are using could be used to save a pandemic victim (due to triage protocols). Now when you question legitimacy, I am not quite sure what you are after. I am not trying to defraud or manipulate anyone, and my motives for the project are entirely humanitarian. It is not a commercial venture; in fact I have spent a fair bit of my own time and money on it. All of my work and postings are available for you to view and see for yourself. Now if by legitimacy, you mean authority, I really have none. The opinions I express are my own. It is up to the reader to determine if my arguments are rational and my sources of information are valid.

Now when you warn against an untrained person just setting up ECMO on a dialysis machine when no prior testing or feasibility studies have been done you are absolutely correct. When I proposed this idea, it was for people that are qualified to do ECMO treatments to try to find innovative alternative ways to provide this potentially life saving treatment even if there were a shortage of existing ECMO equipment during a pandemic. I was hoping that knowledgeable people could look at the idea and see if they could make it work safely rather than dismiss it out of hand. Perhaps a someone could find a solution to this problem with the pumps that you mentioned.

Now when you assuredly state that there will be NO shortage of ECMO systems in the US, I do not think you can say that for sure. When we have Dr. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota (CIDRAP) http://www.cidrap.umn.edu/ worried about a shortage of ECMO machines http://legal-ledger.com/item.cfm?recID=12283 , http://www.startribune.com/lifestyle/health/59253022.html?elr=KArksD:aDyaEP:kD:aUbP:P:Q_V_MPQLa7PYDUiD3aPc:_Yyc:aUHDYaGEP7eyckcUr, and with Dr Dr. Giles Peek of Glenfield Hospital in Leicester, England talking about how few the number of ECMO machines are available in Britain. http://latimesblogs.latimes.com/booster_shots/2009/09/bypassing-lungs-helps-swine-flu-pneumonia-victims.html The World Health Organization is also warning developed countries "to anticipate this increased demand on intensive care units, which could be overwhelmed by a sudden surge in the number of severe cases." http://news.eirna.com/209051/h1n109-who-issues-warning-on-second-wave-of-pandemic

There is agood chance that the current H1N1 pandemic will remain mild and within the ability of our current infrastructure and surge capacity to manage, But I do not believe anyone can definitely say that this will be the case.

What you say about legal liabilities is unfortunately sadly true. The heroic measures undertaken by individuals during the polio epidemic to build their own ventilators to save the lives of children could never happen in today’s legal liability climate. The only hope for that is if legislatures provide legal liability exemptions to the individuals that decide who gets which machine and treatment in a pandemic. Under today’s legal climate it is more prudent for a physician let his patient die by denying access to a potentially life saving treatment than to risk a lawsuit by using an uncertified device.

I must say in defence of any nephrology professionals that read this, hemodialysis is also a type of life supporting treatment that is done extracorporeally. Most of the complications that can occur in VV-ECMO can also occur in hemodialysis. Hemodialysis is routinely done in a safe mode by trained individuals. There were over 300,000 patients safely dialyzed for more than 150 million hours of treatment in more than 4000 centers in the US last year alone.

Clarence Graansma

Monday, September 7, 2009

Are the H1N1 Death Numbers Low?

The Number of Deaths Due to H1N1 Compared to the Number of Deaths Due to Seasonal Flu.


I keep hearing about how the numbers of deaths from H1N1 are really quite low worldwide. In one respect, this is true, and I hope that it stays that way. Here is a CBC article from Sept 4 2009.

If you read discussion forums or the comments section on some news websites, many people use the currently low death ratio to argue that the H1N1 pandemic declared by WHO is a non-event, and that we are spending way too much time and energy on it. There are even conspiracy theories regarding vaccination programs.

So here are some raw numbers:
About 36,000 deaths per year on average due to seasonal flu in the USA alone.
2,837 worldwide from H1N1 flu since the pandemic began.

From these numbers, it seems like the H1N1 pandemic is very small compared to the seasonal flu epidemics. These numbers are deceiving though. First of all you have to look at how the numbers are counted. The H1N1 fatalities are all confirmed, reported H1N1 cases. The 36,000 annual US death number for seasonal flu is based on a statistical method. If only confirmed, reported seasonal flu deaths were counted, the seasonal flu number would be about 2,000. That is not to say that the 36,000 figure is incorrect, it is just that very few death certificates actually list flu as the cause of death. They usually list a complicating factor such as pneumonia or heart failure.

Another thing to consider is that deaths from seasonal flu are more common among the elderly and persons with chronic conditions that compromise their immune systems. The H1N1 virus as well, is more likely to cause death if the infected person also has some other compromising medical condition, but it is not age specific in favoring the elderly. In fact it has more of a bias to causing severe disease in younger persons.

Another thing to consider is that as the time of year that flu typically increases in the northern hemisphere approaches; the incidence of all types of flu is expected to rise dramatically.

Here is an article from Slate magazine about this

Here is an article from JAMA that you can download



And, one more thing...

The Pandemic Ventilator Project has been referenced in a book by Tom Atlee. This book has contributions by many people that are very knowledgeable in the field of sharing intelligence to improve the world.

It is called Collective Intelligence: Creating a Prosperous World at Peace

It is available at Amazon in hardcover here.

It is appropriately published under Creative Commons, same as this blog.

If you want to see it in PDF format you can get it here.

This is the section that has the Pandemic Ventilator Project Reference in it (page 457)
. It is written by Mark Tovey.