Blood sampling made easy by automated system
22 April 2009
Blood tests are common procedures in medicine and sometimes several are required over a prolonged period. Hormones, for example, fluctuate throughout the day and need multiple samples to monitor.
Most people find the process unpleasant, and even the approach by a nurse can cause stress and anxiety.
"Current techniques for repetitive sampling require a nurse or healthcare worker to draw blood through a syringe connected to an intravenous line," says Dr David Henley, from the Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology at the University of Bristol.
"This is a particular problem if doctors are measuring stress hormones, as the blood tests can provoke anxiety and affect the levels of the hormone. Being manually intensive it is also prone to sampling error."
A new computer-controlled system, devised by Dr Henley and colleagues, aims to reduce stress and improve the accuracy of blood tests for monitoring patients.
The system takes blood samples unobtrusively from patients at regular intervals over extended periods, allowing for greater consistency in the timing and quality of samples.
Samples are taken without the need for a needle to be inserted each time and often without the patient noticing. This has particular benefits for overnight monitoring, allowing the patient to sleep undisturbed.
So far, the researchers have tested their system successfully on five volunteers at a Bristol hospital, safely collecting samples of good consistency every ten minutes over a 24-hour period. They were able to measure the levels of the stress hormones adrenocorticotropin (ACTH) and cortisol accurately and at the same time.
"What makes this a particularly powerful tool is that it can be programmed to receive input signals from other devices, and can therefore be linked to physiological events," says Dr Henley. A sampling cycle could, for example, be triggered by an increase in heart rate or blood pressure, providing data on how these factors correlate with the level of hormones or other compounds in the blood.
"This is possible because of automation, and would be very difficult and highly prone to inaccuracy with manual techniques," Dr Henley adds.
The researchers are now looking to adapt the system for use with children, and develop a compact version that could be used in a patient's home.
Image: Blood samples in test tubes; Flickr/littlepomegranate
Henley D E et al. Development of an automated blood sampling system for use in humans. J Med Eng Technol 2009;33(3):1-10.