Oxygen Deficit: Objective, Sensitive Measure of Impaired Gas Exchange

The concept of determining the oxygen deficit using a non-invasive method was pioneered by John B. West, a globally known physiologist (medical text book author of Respiratory Physiology The Essentials), and a team of respiratory physicians at UC San Diego (UCSD) Medical School.

Oxygen Deficit is an objective measure that indicates the degree of impaired gas exchange.  It is obtained non-invasively from a patient’s breathing gas samples at rest and from pulse oximetry.  Oxygen Deficit is the difference between end-tidal O2 in the lungs (PAO2) and a calculated partial pressure of arterial oxygen (gPaO2TM = calculated PaO2 by the MediPines Gas Exchange Monitor).  In essence, it reports the degree of inefficiency of the lung to transfer oxygen into the capillary blood.  The Oxygen Deficit is calculated as follows: O2Deficit = PETO2 (PAO2– Calculated PaO2 (gPaO2TM). The value is calculated by the MediPines Gas Exchange Monitor using samples taken during normal breathing at rest and is expressed in mmHg.  

In patients with worsening gas exchange, Oxygen Deficit is a more sensitive indicator than oxygen saturation.   For example, a patient’s arterial oxygen saturation (SpO2) may fall by only 2% or 3% but their Oxygen Deficit tends to increase by a much wider margin (e.g., 10 mmHg) than SpO2, providing a more sensitive indicator of gas exchange impairment. This wider margin assists medical professionals in quickly recognizing deteriorating conditions and a patient's response to therapy.

 

Oxygen Deficit has been shown to be highly sensitive to gas exchange impairment due to respiratory diseases like COPD.

A New, Noninvasive Method of Measuring Impaired Pulmonary Gas Exchange in Lung Disease: An Outpatient Study. West, John B. et al. CHEST, Volume 154, Issue 2, 363-369. 

 

 Above data, as shown, is based on a clinical study conducted and published in 2017/2018, normal subject data were captured under hypoxic conditions.

UCSD Data Graph

 Source: A New, Noninvasive Method of Measuring Impaired Pulmonary Gas Exchange in Lung Disease: An Outpatient Study. West, John B. et al CHEST, Volume 154, Issue 2, 363-369.