Doctors and apps

Epidemiologist David Van Sickle spent years studying asthma, but like many researchers of the chronic disease, he was frustrated by the obstacles to determining precise triggers of an individual attack. That frustration gave him an idea for a rescue inhaler topped with a GPS sensor. The invention would map the user’s location every time he took a puff and send that information back to his doctor.

Such a device, Van Sickle thought, would give doctors data about when and where attacks occurred, helping them figure out possible environmental causes and allowing them to plan treatment accordingly.

In 2006, he began work on a prototype, an endeavor that turned out to be harder than he had imagined, chiefly because the sensor attachment had to be as durable as the inhalers themselves.

“The first prototypes were very ugly — like a coffee machine alongside of an inhaler,” Van Sickle recalls. He says colleagues joked that just carrying one around might be stressful enough to induce an asthma attack.

In 2008, Van Sickle launched a study of the device that was funded by the Centers for Disease Control and Prevention. He also founded Asthmapolis, a company that has continued to fine-tune the device. The latest version of the inhaler is equipped with a smaller, Bluetooth-based device that sends usage information to a Web portal that can display when and where patients have used their inhalers.

Rajan K. Merchant, of Dignity Health’s Woodland Clinic Medical Group outside Sacramento, began enrolling patients in another Asthmapolis trial last spring. He called the device the first major advance since the advent of the anti-inflammatory steroid inhaler in the 1950s.

‘Place should be a vital sign’

The Asthmapolis inhaler is part of a burgeoning field called geomedicine, which uses geographic information system (GIS) technology to correlate environmental conditions with health risks. The hope is that this data, integrated into a patient’s medical history, will help doctors and researchers fine-tune their diagnoses and treatments.

“Place should be a vital sign,” says Ethan Berke, a spatial epidemiologist at Dartmouth Medical School in Hanover, N.H., and a family physician.

Doctors have long connected place and health, Berke says, pointing to John Snow, often called the father of modern epidemiology for his work linking London’s 1854 cholera outbreak to drinking water contaminated by raw sewage. But today, technology has given them more precise and powerful ways to understand role of location in patients’ health.

“I would love it if I could bring up [a] map and see the grocery stores, parks” that patients have recently visited “right there while you are checking their blood pressure,” Berke says. Such information would allow him to better tailor his medical advice based on a patient’s lifestyle.“I can do that now, but I don’t have many GIS tools in the exam room.”

Mapping health

One of the chief instigators of geomedicine is Bill Davenhall, a manager at the GIS software company Esri. After he had a heart attack that he suspected was linked to environmental factors, Davenhall got Esri to build an app that integrates places a person has lived with a report of toxins found within three miles of those locations. Users can share that information with doctors.

Davenhall has been working with Loma Linda University Medical Center outside Los Angeles to integrate geography into patient treatment.

Dora Barilla, director of community health development at the medical center, says that it intends by early March to launch software interfaces that map the health status and local environments of more than a million of its patients.

The medical center plans to include on its public Web site information about disease hot spots and other data that until now have been stored in unwieldy databases. The site will also show maps of public resources such as grocery stores and parks.

These initiatives seek to reveal how the place where you live affects the quality of your health, and then map out ways to address problems. For instance, soon Loma Linda doctors and case managers will be able pinpoint food pantries and soup kitchens in the medical center’s service area, making it easier to suggest ones near the homes of low-income patients who need to improve their diet.

Other geomedicine technologies under development include Health Begins, a social networking platform that seeks to make clinicians more aware of socioeconomic factors that can affect health. The site, now in the testing phase, allows doctors, patients and family members to update entries, such as where to apply for affordable housing or how to contact a legal clinic for reporting unhealthy working conditions. The site also has a section that shows the latest research assessing links between social, economic and environmental factors and health.

Rishi Manchanda, the founder of Health Begins, says he became interested in geomedicine while working as a primary-care physician in a poor section of Los Angeles, where he linked a patient’s leaky, damp and moldy apartment to her allergy, sinus and migraine problems.

Rich Roth, vice president of strategic innovation at Dignity Health and others say they expect to eventually see “place” tools incorporated into electronic records to streamline use by doctors, nurses, social workers and others in the health-care team.

Privacy concerns

But such tools come with some potential downsides. Kate Black, an attorney focusing on health privacy at the Office of the National Coordinator of Health Information Technology, part of the U.S. Department of Health and Human Services, says, “Geomedicine is one of the great opportunities for technology in health care,” but app developers ignore privacy concerns at their peril.

While patient information is filtered to remove names and other personal data, details can sometimes be traced back to the individual. “There’s always a risk,” Black says.

Apps that query information already in public view — such as the Google flu tracker — are less problematic than ones that ask users to input personal information, she says, because people may not understand that they are disclosing information that may later be sold to third parties without their knowledge or consent. This information could then be used to market to them products or services they don’t want or used against them to determine such things as health-care coverage and premiums. And, she adds, people have reason to worry how such data can be used against them.

If companies can “learn that you’ve lived in these 14 neighborhoods, exposed to these 14 different risks, that might be the basis for denying you coverage,” she notes.

“These apps need to be very clear about the data they use and whether they are disclosing it and how it will be used. Most of these apps don’t do that,” Black says.

Barilla, at the Loma Linda medical center, says privacy is such a big concern that administrators opted not to directly link patient medical records to the geographical tools. Instead, case managers will plug the patient’s address into the publicly available databases on the medical center’s Web site.

All it would take is one privacy-related controversy “to kill off this work,” Barilla says. “So we are being cautious about privacy.”

Van Sickle at Asthmapolis says his company gives “patients options to decide how much, if any, information they want to share. But we think there is lots to be gained by sharing,” he says, adding that so far the company has found plenty of trial participants with “a willingness to give up a little bit of privacy as long as there are protections and trust and an agreement that [the information] will be used to help them and others with asthma.”

Asthma hot spots

Aggregate patient information is of interest to researchers such as Meredith A. Barrett, who works at the Center for Health and Community at the University of California at San Francisco.

“We’ll be looking for hot spots in cities,” she says, trying to figure out why people get asthma and what can trigger attacks. “And you could take climate-change information and use this type of geolocated data” to help predict outcomes, says Barrett, an ecologist who examines how environmental factors affect health.

In July, Van Sickle’s GIS-enhanced inhaler received clearance as a medical device from the Food and Drug Administration. (The SmartTrack, a similar inhaler that received FDA market clearance in 2009, is sold just to companies and universities for research studies and pilots.)

Since July, Asthmapolis has signed contracts to manage asthma patients for a Medicaid managed-care organization and a hospital.

And there have been surprises: The company’s study in rural Wisconsin found people puffing on their inhalers more than urbanites, a finding that goes against what asthma researchers have long believed.

“It’s these kinds of insights that we think will help us understand the origins of the disease,” Van Sickle says.

For Tim Frank, a 44-year-old chef who lives in Woodland, Calif., the Asthmapolis inhaler has already yielded new insights about the asthma he’s had since childhood. He says since he enrolled in the clinical trial last spring, he has noticed how often he needs his inhaler when driving past agricultural fields, where dust in the air apparently triggers his symptoms.

“It really helps, because I could avoid that area if I had to,” he says. “I think that’s the whole idea.”

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How do batteries work?

Here is a quote from a science-like show I saw recently. In the scene, two individuals were talking about using batteries for an electric motor. It should be noted that one of these individuals is labeled as “a physicist.” And no, I am not going to name the show.

It’s a matter of how much acid you need to store enough charge so that the two cells – the positive and negative, can create current to drive that motor. And you need that many to have the amp-hours which is another way to say capacity so that you can drive for some distance.

It’s not that the narrative is terrible (but it is terrible). It’s that this is supposed to be coming from the mouth of a physicist. What non-physicists hear is that batteries are super complex and there is nothing anyone can understand about them. It’s true that batteries are indeed complicated, but this could have been worded better. If it were my show, here’s what I would say about batteries.

There are two main things to consider with your battery choice. Can it produce enough current to drive your motor and does it have enough stored energy to last you enough time? That’s really it.

See? Isn’t that better? My primary suggestion for shows is that less of an explanation is better. Fewer terms means more likely to be “not wrong.” You can’t always be exactly correct, but you can be completely wrong. So just say the minimum.

But do batteries store electric charge? In short, no. Let’s look at a simple and complicated explanation of a battery.

Simple Battery Physics

But what about a more complicated explanation of a battery? How does a battery store energy? How does it make an electric current? Let me start with the most basic explanation.

A battery maintains a nearly constant change in electric potential across its terminals. When a complete circuit is connected from one terminal to the other, there is an electric current. Of course this current isn’t for “free”. It takes energy to move this current through a circuit. Where does the energy come from? There is energy stored in the battery in the form of chemical potential energy.

Yes, it is true that a current can be described as moving electrical charges. However, it is not true that these charges are “stored in the battery”. Let me give a simple analogy. If electric current is like water, then a battery is like a water pump. In the scene above, the guy describes the battery as if it were a water balloon shooting out water. That’s not how it works.

If you wanted to say a capacitor stores charge, that would be ok. But in this case the guy is using a battery and not a capacitor.

What is the Electromotive Force?

Now for a more sophisticated model of a battery. Many physics textbooks have a model similar to this, but I think Matter and Interactions (my favorite intro physics textbook) does the best job of explaining the term “electromotive force”. Oh, Matter and Interactions also has the best connection between electric fields and electric currents in circuits. Trust me, if you haven’t looked at this textbook, take a look.

For this model, let’s start with a capacitor. Yes, I know I just said a capacitor isn’t a battery but just hang on. Here is a parallel plate capacitor that isn’t connected to anything.

In this parallel plate capacitor you can make one plate positive by taking electrons away and putting on the other plate making it negative. Once you get these charges on the plates, there is a mostly constant electric field between these plates. If the field has a strength of E and the plate separation is s, then the change in electric potential from one plate to the other is:

Great. But like I said, a capacitor is not a battery. With a battery you would like the change in electric potential to be nearly constant. If you hook a lightbulb up to a capacitor, the charge from one plate leaves to produce an electric current. This decreases the charge on the plate and thus also decreases the electric potential. How could you solve this problem? What if you put a little conveyor belt inside the plates and this belt moved electrons from the positive plate to the negative plate?

Yes, this isn’t a real conveyor belt – it’s just a model. However, what happens as more and more electrons get added to the right plate? Yes, the electric field inside the capacitor increases. At some point the electric field inside the capacitor becomes great enough that it exerts an electric force on the electron with a magnitude equal to the force that the conveyor belt pushes on the charge. Beyond this charge (and electric potential across the battery) no more electrons can be moved to the right plate.

So, let’s write this as an equation. When it is fully charged, there are two forces on an electron in middle. There is the electric force from the charges (I will call this FC) and there is the force from the “battery” or whatever it is (Fb).

Here I just rewrote the electric force on the charge in terms of the electric field and I am using e to represent the charge of the electron. But if the battery voltage is ΔV, then I can also write the following expression for the electric field inside the capacitor (assuming constant electric field):

The voltage across the battery depends on this force from the belt in the battery model to push it across (and also the distance between the plates). Historically, we call this change in electric potential across the battery the emf which usually stands for ElectroMotive Force. But clearly, it isn’t a force since it has units of volts. But it also isn’t just a change in electric potential. Suppose you have a 1.5 volt battery. If you integrated the electric field from one plate to the other, you would get -1.5 volts (this has to be true since it’s path independent). The only way for you to get a zero change in potential around the circuit would be to have this emf across the battery.

But how does this “conveyor belt” really work? I think at this point, it’s best for me to just say “it’s a chemical process” and leave it at that. However, the belt model is useful when the battery is hooked up to a circuit. If you connect this battery to a lightbulb, electrons move through the wire and leave the right plate. This reduces the electric field inside the capacitor so that the belt can put more electrons on the plate. Of course this belt requires energy – the battery doesn’t last forever.

In fact, I think this battery doesn’t even have to have a chemical process to replace the conveyor belt. It seems that you could use an actual belt. This is what happens in a Van de Graaff generator (the metal ball that you put your hand on to make your hair stand up). However, I will save the analysis of a Van de Graaff generator for another day.

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