Research Interests
These are in no particular order.  General practice, in theory, offers great potential for research because of the volume of patients seen and the diverse medical conditons one encounters.  In practice, there is no time to do formal double-blind studies, but the observational studies I've been doing provide a good starting point for research projects.  If any drug company is willing to pay me to take a year off my practice to do a research project properly, I'll be happy to oblige.  Only some of the entries in my list below have been expanded as of 24/1/2007.

Obstructive sleep apnea
This is an incredibly common condition in general practice and for a while was very underdiagnosed.  There is a spectrum of sleep disordered breathing ranging from physiologic sleep apnea that occurs in most people during REM sleep to people who might breathe once or twice a minute the whole time they're asleep.  The most common symptoms that people come to see me with that suggest OSA are daytime sleepiness, hypertension and frequent urination during the night.  Screening for OSA is very simple and involves doing an overnight home pulse oximetry.  Home diagnosis of OSA is becoming more and more common with referrals to sleep labs being done far less often than when I first started practicing.  Dr. John Remmers of Calgary has designed a device (the Remmers sleep recorder) which can perform almost all of the functionality of a sleep lab at home. 

My interest in OSA goes back many years since I've always had an interest in sleep (and I'm told that I'm quite good at it when I get a chance to get some) and with my background in computerized data acquisition, it seemed obvious to start playing around with oximeter data.  I was lucky to get to know the people at Clinical Sleep Solutions who have been exceedingly helpfull in providing prompt overnight home pulse oximetry studies and CPAP machines to those diagnosed with OSA.

Treatments for OSA range from methods to ensure that one sleeps on ones side, continuous positive airway pressure (CPAP) machines and dental appliances.  A CPAP machine, if tolerated by someone with OSA, is the most effective treatment with dental appliances being less effective but much preferred by some people.  If snoring is the primary problem, then a dental appliance is likely to reduce snoring significantly.  A number of dentists in Vancouver have expertise in fitting people for dental appliances and I have dealt primarily with Dr. David Monaghan at Fifth Avenue Dental.

My observational studies have looked at:
- incidence of OSA in general practice
- relationship between hypertension and OSA in general practice
- mood disorders and OSA
- pharmacologic treatment of OSA
- home sleep studies hardware/software.  I couldn't resist making my own system which will be described here RSN (a partial description of the system is in my blog).

Respiration and blood pressure.
This was an incidental finding when I first had a pulse oximeter to play with in my practice (courtousy of Clnical sleep solutions).  As with every new toy, I played with it a lot.  When patients came in to see me, I'd stick a pulse oximeter probe on their finger and watch the oxygen saturation while I talked to them.  It quickly became apparent that there were two types of patterns one could detect.  The most common was the rather boring one of people having an SaO2 of 98-99% which didn't change over a period of minutes.  The more interesting pattern was one in which SaO2 varied over a large range during a 5 minute interval.  Often these people would have a low SaO2 of around 90-92% and once I pointed it out to them they would start breathing more deeply, the SaO2 would rise and then they'd go back to their normal breathing pattern which was underbreathing in comparison to the former group with the boring SaO2 pattern.  The first few patients I saw in my practice with low SaO2's were all hypertensive and it didn't take long for me to start wondering what would happen to their bp  if I got them to breathe more deeply and recheck their blood pressure at an SaO2 of 98% instead of 92%.  This experiment was a very simple one which yielded immediate results; the first 10 or so patients I had perform this maneuver had significant drops in their systolic bp with mild hyperventilation.  The results were quite astounding at times with the record being almost 100 mm Hg in one patient whose bp didn't seem to respond to anything.

Once I took the pulse oximeter home to do nightly sleep studies on myself, I changed the protocol to take a patients bp, have them take 3 very deep breaths and then take the bp again in about 5-10 seconds.  In the vast majority of cases the bp reading after 3 deep breaths is lower than the initial reading.  I was intrigued and figured that someone else must have described this phenomenon in the medical literature and was astounded when I found not a single reference to this doing a medline search in 2005.  The only references I found were in the psychologic literature where techniques of controlling bp by retraining breathing were described.  Also, people with panic disorder apparently have a bp rise with hyperventilaton; something I have also cofirmed.

I was in a bit of a quandry once I had found this as I wanted to publish it, but this would mean designing a proper double blind study and this would take time.  I elected to record the two bp's I got in the chart and have probably done this test on over 100 people in the last two years.  One unexpected byproduct of dong blood pressures in this way was that many of my hypertensive patients would start to hyperventilate before I had a chance to take their bp.  Their bp control was better than before, but it was clear I couldn't do a double blind study as they had been conditioned to hyperventilate at the sight of a sphymomanometer. 

RSN I'm going to go through my data and publish the average effect and raw data here.  Patients of mine with labile hypertension have used this technique to great advantage when having insurance medical exams.  One patient of mine routinely had a bp of 120/70 when I took it in my office without hyperventilation, but during an insurance medical exam with a nurse that rubbed him the wrong way, his bp was recorded at 170/100.  Hyperventilation solved the problem on a repeat insurance examination.

This leads to some interesting questions as to what constitutes a normal bp?  There are a large number of patients (I estimate about 25% of my hypertensives) who have white coat hypertension.  Their home bp's are fine and their 24 hour bp records are also normal, but they can exhibit quite marked varibility in their blood pressure.   A significant number of these patients have been found to have OSA and irregularities in their awake SaO2 levels.  As soon as I can get access to an ambulatory pulse oximeter I'd like to study some of these people to see what their SaO2 does during the day.  I suspect that many of these people hypoventilate in stressfull situations.  I haven't done the experiment yet to take an individual with a flat, boring, SaO2 pattern and have them hold their breath to see what happens to their blood pressure.

My hypothesis is that what I'm seeing are "pink puffers" and "blue bloaters" without lung disease.  These colorfull terms are applied to the two types of COPD patients one sees.  Pink puffers have normal SaO2 and are very sensitive to hypoxemia.  Blue bloaters, on the other hand, have much lower SaO2's and retain CO2.  They are bloated because of the edema they get from right heart failure.  It appears that these individuals represent two distinct types of respiratory drive and I believe this is genetic.  There, now I've finally written up something about this very interesting phenomenon and what I really need is a resident who wants to do this as their research project to get it written up in a peer reviewed journal.

Page last updated:  24/1/2007 T:=00:49
(C) Dr. Boris Gimbarzevsky 2007