A new bedside ABG sensor may offer clinicians the patient-dedicated blood analyzer they need to provide faster and more frequent readings, without traditional obstacles.


Since 1670 when Robert Hooke and Robert Boyle obtained air from blood via a vacuum pump, blood gas analysis (ABG) has been the subject of discussion and research from many scientists. Researchers, including Poul Astrup, Ole Sigaard-Andersen, Leland Clarke, John Severinghaus and many others, have contributed to better understanding of blood gas analysis and have created machines to effectively measure ABG. The research efforts of Severinghaus, in particular, brought clarity to the importance of blood gas analysis as it relates to anesthesia and cardiopulmonary and respiratory physiology.

Clinicians have come to understand the value that monitoring blood gas can have on a patient’s overall condition. Many scientific experiments, discoveries, failures and successes in the ensuing years have led to more efficient and less invasive procedures.

Most recently, researchers compared a blood gas analyzer attached to the patient with a traditional bench-top analyzer in a hospital-based study,1 providing some interesting insight and promise for a cutting-edge patient monitoring tool.

According to an article by Gavin Troughton, vice president, business development for Sphere Medical, arterial blood gas readings provide critical information that can assist in the “maintenance of tissue oxygenation, ventilation and acid-base status” of patients in the intensive care unit (ICU). However, such measures are typically taken intermittently, rather than continuously, which presents a challenge in effectively managing patients. Not only might blood gas samples obtained irregularly offer outdated information, but they could also compromise blood conservation efforts.

Troughton pointed out the necessity for a patient-dedicated blood analyzer that would offer faster and more frequent readings. But, he added, current models do not lend themselves to such efficiency. Large complex machines that require calibration, flushing, sorting the blood and controlling temperature pose a technological challenge. Instead, Troughton lobbied for a chip-based system that would capture all relevant data, including pH, pO2, pCO2, lactate and calcium changes, and return the blood to the patient.

To address these issues, Sphere Medical in the UK developed a disposable sensor that is placed in the arterial line and connected to a monitor within the patient’s own bed space. The Proxima System withdraws blood samples, analyzes them and then returns the blood to the patient. To test the efficacy of this method, Sphere conducted a study at Queen Elizabeth Hospital in Birmingham, England where 20 patients in the intensive care unit (ICU) with various conditions, including trauma, head injury, post-surgical recovery and sepsis, were monitored with the Proxima System for as many as three days.

In addition to testing the patient’s blood with the Proxima System, the study authors examined a concurrent blood sample using the hospital’s bench-top analyzer. During the study, more than 300 measures of pH, pO2, pCO2, hematocrit and K+ between the newer closed method and traditional bench-top method proved to be comparable.

Along with reporting blood gas analysis accuracy, the study suggested that a patient-dedicated system would reduce adverse effects in patients with serious medical conditions where life-threatening changes to blood gas chemistry can occur suddenly. Results from the Proxima System are available immediately and displayed on the patient’s bedside monitor for clinician review. Also, the study authors asserted that continuous bedside monitoring would reduce the workload for nursing staff while still monitoring patients.

The study also cited the preservation of blood as another positive outcome. A closed system allows for blood withdrawal and return, eliminating blood loss and reducing the risk of hospital-acquired anemia and the need for transfusions.

Furthermore, placing the sensor within the arterial line eliminates the need for additional procedures, which reduces costs. Training to use the Proxima System was minimal; staff at Queen Elizabeth Hospital underwent a 90-minute training session before using the system. RT

Phyllis Hanlon is a contributing writer to RT. For further information, contact [email protected].