Comparative Analysis of Oxygen Saturation by Pulse Oximetry and Arterial Blood Gas in Hypoxemic Patients in a Tertiary Care Hospital
Introduction: Oxygen saturation is essential for medical care and is closely regulated within the body.
Arterial blood gas (ABG) analysis is used to evaluate critically ill individuals'
ventilation, oxygenation, acid-
base status, and metabolic condition. Pulse oximetry is an easy and non-invasive way to measure the status
of oxygen saturation non-invasively in clinical settings and provides a quick and precise assessment of
oxygenation and reduces medical errors. SpO2 may not always be a reliable predictor of arterial oxygen
saturation (SaO2), and hypoxemic, hemodynamically compromised, and critically ill patients may have lower
SpO2 accuracy. A study is needed to assess and compare various oxygen saturation methods.
Aims and objectives: The study aimed to compare the oxygen saturation levels measured by pulse oximetry
and ABG analysis in hypoxemic patients. The objectives were to compare the values between SaO2, PaO2,
and SpO2 values obtained from the patients, and correlate the study parameters among both techniques.
Materials and methods: The study was conducted from February 2021 to June 2022 among the 102
hypoxemic patients who were admitted to the emergency and surgical intensive care unit (ICU) of Sree Balaji
Medical College and Hospital in Chennai. Primary data on ABG analysis and pulse oximetry readings were
collected from the study subjects. The patient and their past medical records, physical exam, chest x-ray
findings, pulse oximetry, and ABG results were all reviewed. Each patient had their ABG, and pulse oximetry
measured simultaneously. A comparison was made between SpO2 and partial pressure of oxygen (PaO2) and
arterial oxygen saturation (SaO2) parameters using a paired t-test. The correlation was done against the
SpO2 and ABG parameters and assessed for association using the correlation coefficient value; gender was
also considered while correlating.
Results and discussion: An observational study was done among 102 study samples to comparatively analyze
the oxygen saturation by two methods, namely pulse oximetry and ABG, in hypoxemic patients. While
comparing the mean values of SaO2 and SpO2, they were 84.41 ± 4.24 and 80.58 ± 5.77, respectively, and this
difference was statistically very significant (p < 0.001). While comparing the mean values of PaO2 and SaO2,
they were 61.02 ± 5.01 and 84.41 ± 4.24, respectively, and this difference was statistically significant (p =
0.043). While comparing the mean values of PaO2 and SpO2, they were 61.02 ± 5.01 and 80.58 ± 5.77,
respectively, and this difference was statistically significant (p = 0.054). Among the study population, with
regard to the correlation factor, there is notably a very high and strong positive correlation between SaO2
and SpO2 and between SpO2 and PaO2. There was a negative correlation between SpO2 and finger
abnormalities and between SpO2 and blood pressure.
Conclusion: The ABG method is considered the gold standard. When SpO2 levels fall below 90%, pulse
oximetry may not be accurate enough to reliably assess oxygenation. In such cases, where alveolar
hypoventilation is suspected, it is recommended to complement pulse oximetry with ABG studies. This is
because ABG analysis provides a more comprehensive assessment of oxygenation and acid-base status,
which can aid in the diagnosis and management of respiratory conditi
Arterial blood gas (ABG) analysis is used to evaluate critically ill individuals'
ventilation, oxygenation, acid-
base status, and metabolic condition. Pulse oximetry is an easy and non-invasive way to measure the status
of oxygen saturation non-invasively in clinical settings and provides a quick and precise assessment of
oxygenation and reduces medical errors. SpO2 may not always be a reliable predictor of arterial oxygen
saturation (SaO2), and hypoxemic, hemodynamically compromised, and critically ill patients may have lower
SpO2 accuracy. A study is needed to assess and compare various oxygen saturation methods.
Aims and objectives: The study aimed to compare the oxygen saturation levels measured by pulse oximetry
and ABG analysis in hypoxemic patients. The objectives were to compare the values between SaO2, PaO2,
and SpO2 values obtained from the patients, and correlate the study parameters among both techniques.
Materials and methods: The study was conducted from February 2021 to June 2022 among the 102
hypoxemic patients who were admitted to the emergency and surgical intensive care unit (ICU) of Sree Balaji
Medical College and Hospital in Chennai. Primary data on ABG analysis and pulse oximetry readings were
collected from the study subjects. The patient and their past medical records, physical exam, chest x-ray
findings, pulse oximetry, and ABG results were all reviewed. Each patient had their ABG, and pulse oximetry
measured simultaneously. A comparison was made between SpO2 and partial pressure of oxygen (PaO2) and
arterial oxygen saturation (SaO2) parameters using a paired t-test. The correlation was done against the
SpO2 and ABG parameters and assessed for association using the correlation coefficient value; gender was
also considered while correlating.
Results and discussion: An observational study was done among 102 study samples to comparatively analyze
the oxygen saturation by two methods, namely pulse oximetry and ABG, in hypoxemic patients. While
comparing the mean values of SaO2 and SpO2, they were 84.41 ± 4.24 and 80.58 ± 5.77, respectively, and this
difference was statistically very significant (p < 0.001). While comparing the mean values of PaO2 and SaO2,
they were 61.02 ± 5.01 and 84.41 ± 4.24, respectively, and this difference was statistically significant (p =
0.043). While comparing the mean values of PaO2 and SpO2, they were 61.02 ± 5.01 and 80.58 ± 5.77,
respectively, and this difference was statistically significant (p = 0.054). Among the study population, with
regard to the correlation factor, there is notably a very high and strong positive correlation between SaO2
and SpO2 and between SpO2 and PaO2. There was a negative correlation between SpO2 and finger
abnormalities and between SpO2 and blood pressure.
Conclusion: The ABG method is considered the gold standard. When SpO2 levels fall below 90%, pulse
oximetry may not be accurate enough to reliably assess oxygenation. In such cases, where alveolar
hypoventilation is suspected, it is recommended to complement pulse oximetry with ABG studies. This is
because ABG analysis provides a more comprehensive assessment of oxygenation and acid-base status,
which can aid in the diagnosis and management of respiratory conditi