Tag: specimen stability

Guest Post: Drone Transport of Specimens

On a hot afternoon in late September 2016 the Johns Hopkins Medical Drones team drove to a flight field in the Arizona desert with 40 vacutainer tubes filled with human blood obtained from volunteers. The individually wrapped tubes sat in two custom-designed white plastic cooler boxes which had wires coming out of one end, ventilation holes at the other, and ran off the drone’s battery power. We carefully placed one of the boxes on the drone, stood back, and flew the samples around for 260 kilometers in what seemed like an unending series of concentric circles. Great. But why would doctors be involved in this exercise?

For the last 3 years, the Johns Hopkins medical drones team has examined the stability of human samples transported via drone. Our approach has been similar for each study. Get two sets of samples, fly one on the drone, then take both sample sets back to laboratory for analysis to see if there are any changes. However, until this study in Arizona we had only flown these samples up to about 40km, in mild weather, and for up to 40 minutes at a time. A request to set up a drone network in a flood-prone area of a country in Southwestern Africa made us realize that we needed to repeat the stability tests in warmer weather and for longer flights. This drone network would serve clinics that were up to 50 km away from each other, therefore requiring round-trips of at least 100km. Once we received this request it became clear pretty quickly that our previous tests flying for to 40km were not good enough for an aircraft that would have to fly in a hot environment between several clinics that were each 50km away from each other.

After the 3-hour 260km flight, we took both sets of samples back to the Mayo Clinic laboratories in Scottsdale, Arizona and performed 19 different tests on the samples. Each pair of samples was compared to check for differences between the flown and not-flown sample sets. Although results from sample pairs were similar for 17 of the 19 tests, small differences were seen in Glucose and Potassium, which do also vary in other transport methods. We suspect the differences seen in this test arose because the not-flown samples were not as carefully temperature controlled as the flown samples in the temperature-controlled chamber. This study (which is the longest flight of human samples on a drone to date) shows that drones can be used for blood samples even for long flights in hot conditions. However, the temperature and other environmental variables must be well-controlled to keep the blood stable.

 

TimAmukele-small

-Dr. Timothy Amukele is an Assistant professor in the Department of Pathology at the Johns Hopkins School of Medicine and the Director of Clinical Laboratories at Johns Hopkins Bayview Hospital. He is also the Medical Director of two international research laboratories in Uganda and Malawi. He has pioneered the use of unmanned aerial systems (colloquially known as drones) to move clinical laboratory samples.

Jeff Street-small

-Jeff Street is an unmanned systems engineer and pilot at the Johns Hopkins School of Medicine with more than 10 years of experience in the development of new and innovative vehicles. He is leading the Johns Hopkins aircraft development efforts for a wide range of medical cargo applications.

 

 

 

Sample Stability and PO2–A Learning Opportunity

One of the interesting things about working in the field of laboratory medicine is that there are always opportunities for learning new things. Almost every call I get from my colleagues outside the lab allows me and the lab team these opportunities. And sometimes we are reminded of the reason we do the things we do, basically re-learning them.

Case in point: An ICU physician contacted the lab, understandably concerned. He had been monitoring the pO2 in a patient using an I-Stat point of care analyzer. Values had been in the range of 50-70 mmHg, and he had been adjusting ventilation on the basis of those results. A blood gas sample was sent to the main lab, analyzed on an ABL analyzer and gave a result of 165 mmHg, repeated shortly thereafter on a new sample with a 169 mmHg. Understandably, the physician wanted to know which analyzer was wrong and how he should be adjusting his patient’s ventilation.

We quickly did an investigation and determined an interesting fact that we hadn’t paid much attention to previously. A blood gas sample that is sent through the tube system that has any amount of air in the sample, will give falsely elevated pO2 result. We investigated this by collecting blood gas samples, running them on both the I-Stat and the ABL, and then sending them through the tube system and rerunning them on both instruments after tubing. The pO2 values matched on both instruments, both before and after tubing. But interestingly, if there was any air in the collection device when the device was sent through the tube system, the pO2 after tubing still matched on the two instruments, but the values were more than double the original values. If no air was present, there was very little change before and after tubing. We tested this by expressing all air from one set of samples before tubing and leaving air in the syringe on the other set.

The collection process for blood gas samples in our institution has always specified that the collector should express any air in the sample before sending the sample to the lab through the tube system, and after this incident the reason for that step became clear. However, the staff collecting blood gases on the floors needs to be periodically retrained in the collection, and the lab staff needs to be reminded that air in a blood gas syringe arriving through the tube station is a reason to reject the sample. We were reminded that education needs to be a continuous process. We also learned that when we discover the reason for a process, it’s a good idea to document that reason in order to both understand the need and to help motivate people to follow it.

-Patti Jones PhD, DABCC, FACB, is the Clinical Director of the Chemistry and Metabolic Disease Laboratories at Children’s Medical Center in Dallas, TX and a Professor of Pathology at University of Texas Southwestern Medical Center in Dallas.