A “shallow water blackout” is a silent killer

In Jacksonville, Florida, a 50-year-old woman was found at the bottom of her backyard swimming pool. She was an experienced scuba diver who “often stayed at the bottom of the 9-foot deep end without oxygen to increase [her] lung capacity for future dives.”

Despite receiving CPR from her son, she could not be revived.

The Associated Press story about this tragic incident did not explain why a swimmer with her background drowned.

It appears to be a classic case of “shallow water blackout.” This phenomenon occurs when people hyperventilate before diving.

An increasing level of carbon dioxide (CO2) is what triggers the urge to breathe. Hyperventilating causes hypocapnia, a reduced amount of CO2 in the blood. If a swimmer uses up enough oxygen to pass out before the CO2 trigger point for breathing is reached, drowning will occur without notice. Victims are usually found at the bottom of the pool.

Here’s what it looks like in a diagram from Wikipedia:

A physician who lost her son to this little-known phenomenon started a websiteto heighten awareness of the problem. The site contains more information and stories about other drownings caused by shallow water blackouts.

Here is a video of a woman swimming laps of a pool underwater. Advance to the 0:50 point and watch what happens as she begins to slow down. [Addendum 8/13/15 12:50 pm: Warning. The video is graphic. It shows the unconscious swimmer being pulled from the water.]
 

A shallow water blackout may have been responsible for the death of Natalia Molchanova, the world’s foremost freediver, who went missing a few days ago.

Hyperventilating prior to diving is not recommended. Tell your friends.

Read More..

Why in hospital deaths are not a good quality measure

You may be tired of hearing about the Surgeon Scorecard—the surgeon rating system that was recently released by an organization called ProPublica. Like many others, I have pointed out some flaws in it. You can read my previous posts here and here.

I had decided to stop commenting about it because enough is enough, but a recent paper in the BMJ raises a question about one of the criteria ProPublica used to formulate its ratings.

ProPublica defined complications 1) as any patient readmission within 30 days and 2) "any patient deaths during the initial surgical stay."

The authors of the BMJ paper randomly selected 100 records of patients who died at each of 34 hospitals in the United Kingdom. The 3400 records were reviewed by experts to determine whether a death could have been avoided if the quality of care had been better.

The number of patient records in which a death was at least 50% likely to have been avoidable was 123 or 3.6%.

There was a very weak association between the number of preventable deaths and the overall number of deaths occurring at each hospital. By two measures of overall hospital deaths, the hospital standardized mortality ratio and the summary hospital level mortality indicator, the correlation coefficient between avoidable deaths and all deaths was 0.3, not statistically significant.

From the paper: "The absence of even a moderately strong association is a reflection of the small proportion of deaths (3.6%) judged likely to be avoidable and of the relatively small variation in avoidable death proportions between trusts [hospitals]. This confirms what others have demonstrated theoretically—that is, no matter how large the study the signal (avoidable deaths) to noise (all deaths) ratio means that detection of significant differences between trusts is unlikely."

The Surgeon Scorecard was derived from administrative data. No individual analysis of patient deaths was undertaken. According to a ProPublica article discussing some key questions about their methodology, "As for deaths, we took a conservative approach and only included those that occurred in the hospital within the initial stay."

Maybe that wasnt such a conservative approach after all.

And maybe we need to rethink that 2013 paper claiming that medical error caused up to 440,000 deaths per year.

Read More..

Big data is not big enough

Today ProPublica released its “Surgeon Scorecard” touting it as the best way to pick the right surgeon.

It took me less than a minute to discover some interesting omissions from the application.

For laparoscopic cholecystectomy, the only general surgery procedure listed, the app omits approximately one-third of the hospitals in my state including two where I have practiced.

It looks like the problem is that using Medicare fee-for-service data does not yield enough surgeons performing 20 or more cases in some categories such as laparoscopic cholecystectomy for the five years included in the database.

At one of the biggest hospitals in my state, apparently only one surgeon performed 20 laparoscopic cholecystectomies on fee-for-service Medicare patients in the five years studied; 23 other surgeons were listed as having performed fewer than 20 laparoscopic cholecystectomies on patients in the target population. I don’t see how patients who want to use that hospital for their gallbladder surgery will benefit from the Surgeon Scorecard.

In general, the complication rate for laparoscopic cholecystectomy is low, but I think I understand why ProPublica chose that procedure to review. They needed to select a procedure that was done frequently enough to yield a sufficient number of cases for analysis. Unfortunately, because of the limitations of the Medicare fee-for-service data and the low complication rate of the procedure, the Surgeon Scorecard is useless for anyone looking to compare general surgeons.

Similar problems with the scorecard may be in play for prostate surgery. Again, the procedure was chosen because of its high frequency, but in quickly looking through some searches in that area, I note that a number of urologists I know also did not perform 20 cases on fee-for-service Medicare patients.

Perhaps the next iteration of the scorecard will utilize a data set that contains enough patient and surgeon records to make a meaningful comparison.

Until then, general surgeons can relax. They will not have to explain away their complications but will simply have to explain why they aren’t listed in the Surgeon Scorecard.

Read More..

That time Skeptical Scalpel wasn’t skeptical enough

Yesterday I retweeted a link to “Live Action News,” a website with a video claiming that Planned Parenthood was selling fetal organs.

I had watched the video and read the accompanying article but failed to engage my skeptical radar. It turns out that the video was maliciously edited to portray Dr. Deborah Nucatola, Senior Director of Medical Services for Planned Parenthood, in the worst possible way. The video showed her “having lunch with actors posing as buyers who are interested in purchasing the body parts of babies who have been aborted” and discussing prices.

The website Media Matters describes some of the edits and explains why they are deceptive. It turns out that of the 150 minutes of the original footage, only 8 minutes were used in the "Live Action News" clip.

If I had watched the video more closely, I wouldn’t have needed Media Matters or the 150 minutes of original footage to see the flaws.

First of all, it begins with an introduction by a former ABC News anchor Connie Chung promising something shocking. But as you can see in the screen shot below in the lower left corner, it clearly says “ABC News 20/20 March 8, 2000.”

Another obvious clue is that the date and time stamp in the lower left-hand corner of the edited video itself is “2014 07 25.” In retrospect, it does not seem plausible that an anti-abortion organization would have sat on this inflammatory story for almost a year before releasing it.

In addition, the times differ greatly as the video progresses which obviously should have told me that major editing had taken place.





The "Live Action News website looks pretty bogus too.


I am very disappointed in myself for having fallen for this dishonest garbage.

It won’t happen again.

Read More..