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Study of Oxygen Saturation by Pulse Oximetry and Arterial Blood Gas in ICU Patients: A Descriptive Cross-sectional Study

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Nabin Rauniyar
Nabin Rauniyar
Nabin Rauniyar
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Shyam Pujari
Shyam Pujari
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Pradeep Shrestha at Patan Academy of Health Sciences
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Introduction: Pulse oximetery is expected to be an indirect estimation of arterial oxygen saturation. However, there often are gaps between SpO2 and SaO2. This study aims to study on arterial oxygen saturation measured by pulse oximetry and arterial blood gas among patients admitted in intensive care unit. Methods: It was a hospital-based descriptive cross-sectional study in which 101 patients meeting inclusion criteria were studied. SpO2 and SaO2 were measured simultaneously. Mean±SD of SpO2 and SaO2 with accuracy, sensitivity and specificity were measured. Results: According to SpO2 values, out of 101 patients, 26 (25.7%) were hypoxemic and 75 (74.25%) were non-hypoxemic. The mean±SD of SaO2 and SpO2 were 93.22±7.84% and 92.85±6.33% respectively. In 21 patients with spO2 less than 90%,the mean±SD SaO2 and SpO2 were 91.63±4.92 and 87.42±2.29 respectively. In 5 patients with SpO2 less 80%, the mean±SD of SaO2 and SpO2 were: 63.40±3.43 and 71.80±4.28, respectively. In non-hypoxemic group based on SpO2 values, the mean±SD of SpO2 and SaO2 were 95.773±2.19% and 95.654±3.01%, respectively. The agreement rate of SpO2 and SaO2 was 83.2%, and sensitivity and specificity of PO were 84.6% and 83%, respectively. Conclusions: Pulse Oximetry has high accuracy in estimating oxygen saturation with sp02>90% and can be used instead of arterial blood gas.
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JNMA I VOL 58 I ISSUE 230 I OCTOBER 2020
Study of Oxygen Saturation by Pulse Oximetry and Arterial Blood Gas
in ICU Patients: A Descriptive Cross-sectional Study
Nabin Kumar Rauniyar,1 Shyam Pujari,1 Pradeep Shrestha2
1Department of Internal Medicine, Nepal Police Hospital, Nepal, 2Department of Internal Medicine, Dhaulagiri Zonal
Hospital, Baglung, Nepal.
ABSTRACT
Introduction: Pulse oximetery is expected to be an indirect estimation of arterial oxygen saturation.
However, there often are gaps between SpO2 and SaO2. This study aims to study on arterial oxygen
saturation measured by pulse oximetry and arterial blood gas among patients admitted in intensive
care unit.
Methods: It was a hospital-based descriptive cross-sectional study in which 101 patients meeting
inclusion criteria were studied. SpO2 and SaO2 were measured simultaneously. Mean±SD of SpO2
and SaO2 with accuracy, sensitivity and specicity were measured.
Results: According to SpO2 values, out of 101 patients, 26 (25.7%) were hypoxemic and 75 (74.25%)
were non–hypoxemic. The mean±SD of SaO2 and SpO2 were 93.22±7.84% and 92.85±6.33%
respectively. In 21 patients with SpO2<90%, the mean±SD SaO2 and SpO2 were 91.63±4.92 and
87.42±2.29 respectively. In 5 patients with SpO2 < 80%, the mean ± SD of SaO2 and SpO2 were: 63.40
± 3.43 and 71.80±4.28, respectively. In non–hypoxemic group based on SpO2 values, the mean±SD of
SpO2 and SaO2 were 95.773±2.19% and 95.654±3.01%, respectively. The agreement rate of SpO2 and
SaO2 was 83.2%, and sensitivity and specicity of PO were 84.6% and 83%, respectively.
Conclusions: Pulse Oximetry has high accuracy in estimating oxygen saturation with sp02>90%
and can be used instead of arterial blood gas.
________________________________________________________________________________________
Keywords: arterial blood oxygen saturation; arterial blood gases; hypoxemia; pulse oximetry.
________________________________________________________________________________________
_____________________________
Correspondence: Dr. Nabin Kumar Rauniyar, Department
of Internal Medicine, Nepal Police Hospital, Maharajgunj,
Kathmandu, Nepal. Email: nabinrauniyar1@gmail.com, Phone:
+977- 9851281585.
INTRODUCTION
Pulse oximetry (PO) is a useful tool for clinical and
investigational purposes for indirect measurements of
oxygen saturation.1-3 Measurement of oxygen saturation
with SpO2 can be used for evaluation and control of
hypoxemia. As PO is a non–invasive device, it can be
used instead of ABG. Some studies suggest that this
method does not exactly reect the values of ABGs.2,5-7.
The majority of patients admitted in ICU show gaps
between arterial oxygen saturation measured by ABG
and PO. Many studies suggest that pulse oximeters
are inaccurate at low saturations8-12, because as SaO2
decreases, bias will be increased, while precision (the
standard deviation of the differences) will be decreased,
with SpO2 increasingly overestimating SaO2.13
This study aims to study on arterial oxygen saturation
measured by pulse oximetry and arterial blood gas
among patients admitted in intensive care unit.
ORIGINAL ARTICLE J Nepal Med Assoc 2020;58(230):789-93
CC
BY
doi: 10.31729/jnma.5536
CC
BY
JNMA I VOL 58 I ISSUE 230 I OCTOBER 2020
790
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METHODS
A descriptive cross-sectional study was conducted in
ICU of Bir Hospital, Mahaboudha, Kathmandu from
Oct 2017 to Oct 2018 after taking ethical clearance
from Institutional Review Board, National Academy
of Medical Sciences (Ref: 1054). History, clinical
examination, chest X-ray ndings, pulse oximetry and
ABG were reviewed. Patients admitted in ICU with
or without hypoxemia during the study period were
included in the study after obtaining informed consent.
Inclusion Criteria
a. Patient older than 18 years admitted in ICU.
b. Arterial blood gas analysis and pulse oximetry should
be taken simultaneously
c. Informed consent is given by the patient (and from
the relatives of the patients who were unconscious).
Exclusion criteria
a. Data were excluded when SaO2 was less than 60% or
PaO2 were higher than 100mmHg.
b. Patients under 18 years of age.
c. Venous blood sample
Convenient sampling was done and the sample size
was calculated using the formula,
N = Z2 x (p x q) /d2
= 1.962 x (94x6)/52
= 86.6
where, Z = 1.96 ( reliability coefcient at 95 %
condence level)
p = 94 (prevelance of study)
q = 100-p
d = maximum tolerable error = 5
Z= 1.96 at 95 % CI
The calculated minimum sample size was 86.6,
however, the total sample size taken was 101. Data
were collected using a structured proforma covering the
relevant details.
ABG and pulse oximetry were taken simultaneously in
all ICU admitted patients Arterial blood sample (about
0.5ml) was obtained from the radial artery following
conrmation of collateral vessel ow by Allen’s test
or modied Allen test. These are bedside tests that
demonstrate collateral ow through the supercial
palmar arch.
Before taking the sample, the syringe lumen was
heparinized (0.1 ccs). Air bubbles, if present, was
immediately expelled from the sample; the sample
was sealed in an iced container and taken to blood
gas analyzer (ABL 80Flex Automatic Blood Gases,
Copenhagen, Denmark).
SpO2 was obtained using a pulse oximeter (Fingertip,
China). The nger probe for the unit was placed on
the index nger of the opposite arm from which the
arterial sample had been taken. Spo2 was measured
twice at 0 minutes and 2 minutes, then the average of
two was taken. In this study, ABG values were taken
as reference values. According to SpO2, the studied
patients were divided into three groups: SpO2 <80%,
90%>SpO2≥80% and SpO2 ≥ 90%. Hypoxemia was
considered as SpO2 or SaO2 <90% or partial pressure
of oxygen (Pa02) < 60mm Hg by ABG.
The data were collected and entered in MS-Excel 2007
and analyzed using the IBM Statistical Package for
Social Sciences (SPSS) version 20 software. Sensitivity,
specicity and accuracy of PO were measured and
calculated.
RESULTS
A total of 101 patients were enrolled in this study (56
Male, 45 Female). Twenty six (25.7%) were hypoxemic
and 75 (74.25%) were non–hypoxemic according to PO
and based on ABG results, SaO2 values were less than
90% in 13 (12.9%) patients, and the values were equal
or more than 90% in 88 (87.1%) patients. The mean ±
SD oxygen saturation values (SaO2) measured by ABG
analyzer system were greater than those measured
by pulse oximetry (SpO2): (SaO2=93.22±7.84%,
SpO2=92.85±6.33%).
There were differences between pulse oximetry (SpO2)
and ABG values (SaO2) in the limit of SpO2<80% and
90% >SpO2 ≥80% (Table 1).
Table 1. Statistical indexes of oxygen saturation
values measured by ABG and PO for arterial oxygen
saturation.
Statistical Analysis Oxygen saturation
(mean ± SD)
Group Methods
Overall
(n=101)
ABG
Pulse Oximetry
93.22±7.84%
92.85±6.33%
SpO2 < 80%
( n=5)
ABG
Pulse Oximetry
63.40 ± 3.43511
71.80 ± 4.280
90% > SpO2
≥80%
( n = 21)
ABG
Pulse Oximetry
91.63±4.92
87.42±2.293
SpO2 ≥ 90%
( n = 75)
ABG
Pulse Oximetry
95.6547±3.013
95.77± 2.192
In 21 hypoxemic patients (SpO2<90%), the mean ± SD
SaO2 and SpO2 were: 91.63±4.92 and 87.42±2.29.
In 5 of the hypoxemic patients (SpO2 < 80%), the
mean ± SD of SaO2 and SpO2 were: 63.40 ± 3.43
Rauniyar et al. Study of Oxygen Saturation by Pulse Oximetry and Arterial Blood Gas in ICU Patients: A...
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JNMA I VOL 58 I ISSUE 230 I OCTOBER 2020
and 71.80 ± 4.28, respectively. As patients were
dened non–hypoxemic based on SpO2 values, the
mean ± SD of SpO2 and SaO2 were 95.773 ±2.19%,
95.654±3.01%, respectively. The sensitivity and
specicity of pulse oximetry were 84.6 % and 83 %,
respectively (Table 2).
Table 2. Sensitivity, specicity and accuracy of the
Pulse oxymetry.
Arterial Blood Gas (ABG)
Hypoxic (<90) Non-hypoxic
(90 or more)
Pulse
oxymetry
Hypoxic
(<90)
11 (84.6%) 15 (17%)
Non-
hypoxic
(90 or
more)
2 (15.4%) 73 (83%)
DISCUSSION
In acute illness, patients with SpO2 ≥ 90%, PO has
high accuracy in estimating SaO2 and may be used
instead of ABG. The study suggests that in patients
with SpO2 < 90%, however, the exact estimation
of SaO2 and the evaluation of oxygenation by pulse
oximeter is not a good substitution for ABG analyzer.
Regarding the comparison between oxygen saturation
measured by pulse oximetry and ABG, many studies
have been conducted related to accuracy.
In a recent meta-analysis of the measurement of SaO2
by pulse oximetry, Jensen et al. concluded that, from
the 74 studies (1976 to 1994 ), pulse oximeters were
accurate within 2% in the range of 70-100% SaO2.14
In the study of Carter et al., the performance of pulse
oximetry deteriorated below a SpO2 of 75%.15 In
the study of Chiappini et al., a signicant difference
was found between SpO2 and SaO2 values.16 SpO2
values were lower than SaO2 (90.58±5.45% vs.
92.14±5.79%) and a lack of accuracy of the pulse
oximeter was found, but only for SpO2 values below
82%.
Study of Kenneth P Levin et al conducted in 2001,
shows that increasing the assessment of arterial
oxygenation among patients with community-acquired
pneumonia(CAP) is likely to increase the detection of
arterial hypoxemia, particularly among outpatients.
However, ABG should be considered for patients with
underlying cardiopulmonary disease, for those for
whom ventilatory failure is of clinical concern, and if
other reported sources of error for PO are present.17
Similarly, another study of Ebrahim Razi, Hossein
Akbari in 2006 done for COPD patients included 152
patients.18 The accuracy of pulse oximetry was 90.8%,
sensitivity was 93.3% and specicity was 89.1%. The
study reported that in pulmonary diseases with SpO2
≥ 80%, PO has high accuracy in estimating SaO2,
which is contradictory to our study where accuracy is
estimated when Spo2 > 90%. In patients with SpO2
< 80%, however, the result is similar to our study and
concluded that the evaluation of oxygenation by pulse
oximeter is not a good substitution for ABG analyzer.
In a study of Kanai R., Moriyama K. et al done in large
scale including 20717 arterial blood gas samples from
ICU patients, SpO2 tended to show a higher value
than SaO2 and suggest to keep SpO2 above 92% to
avoid hypoxemia in the ICU to decrease morbidity and
mortality.19
Webb et al. reported that pulse oximetry is poorly
calibrated at low saturations and generally less accurate
and less precise than at normal saturations.20 In the
study of Webb et al., nearly 30% of values reviewed
were erroneous by more than 5% at saturation of less
than 80%.
Many studies suggest that pulse oximeters are
inaccurate at low saturations 8-12, because as SaO2
decreases, bias will be increased, while precision
(the standard deviation of the differences) will be
decreased, with SpO2 increasingly overestimating
SaO2. 13 Many explanations have been proposed for
the limited performance of pulse oximeters at low
saturations. One is the slight variations in the output
wavelength of the light-emitting diodes which generate
proportionally larger errors at low saturations.21,22
Another is the generation of proportionally larger errors
in the measurement of transmitted red light versus of
infra-red light at low saturations because of the large
extinction coefcient of reduced haemoglobin.23
In the current study when oxygenation saturation was
more than 90%, there was good correlation coefcient
between the two methods of measurements (in non–
hypoxemic groups, the correlation coefcient was
0.493 and P<0.001). The study revealed that only two
patients (15.4%) out of all who were considered non-
hypoxemic according to PO were considered hypoxemic
in terms of ABG values. The obtained agreement rate
was 83.2%. Given the critical point of SpO2≥90%,
about 83.2% of cases correlated this regard. Thus,
although patients were considered as hypoxemic or
non–hypoxemic according to pulse oximetry or ABG
results, because of slight changes among the results
of the two methods and also a wide variety of cases,
correlation coefcient had shown good correlation
between two methods, especially in Spo2 ≥90% with
P<0.001.
Rauniyar et al. Study of Oxygen Saturation by Pulse Oximetry and Arterial Blood Gas in ICU Patients: A...
JNMA I VOL 58 I ISSUE 230 I OCTOBER 2020
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From the above discussion, we can conclude that PO
is easily available, painless, non-invasive continuous
monitoring and cheap method that can be considered
an appropriate substitute for ABG, especially in SpO2
≥90% with an accuracy of about 83.2%. However
in conditions with low oxygen saturation (SpO2
<90%) and in critical status, PO is a poor predictor of
hypoxemia or not a good alternative to estimate arterial
oxygen saturation. There are several limitations of the
study as the sample size is small and the accuracy rate
is only 83.2%. Futher studies are required for accuracy
and effectiveness of the PO in a large sample. In
addition, though PO measures arterial oxygenation, it
does not assess ventilation. Therefore, it needs to be
aided with ABG analysis when alveolar hypoventilation
is suspected clinically.
CONCLUSIONS
Pulse Oximetry has high accuracy in estimating oxygen
saturation with sp02>90% and can be used instead of
arterial blood gas. The study suggests that in patients
with SpO2 <90%, however, the exact estimation
of SaO2 and the evaluation of hypoxemia by pulse
oximeter is not a good alternative for ABG analyzer.
ACKNOWLEDGEMENTS
We would like to acknowledge the help from Ravi
Bhasker, Department of Community Medicine, National
Medical College, Birgunj, Nepal, for study designing and
statistical analysis.
Conict of Interest: None.
REFERENCES
4. Escourrou PJ, Delaperche MF, Visseaux A. Reliability of
pulse oximetry during exercise in pulmonary patients.
Chest. 1990 Mar;97(3):635-8. [PubMed | Full Text | DOI]
5. Thrush D, Hodges MR. Accuracy of pulse oximetry during
hypoxemia. South Med J. 1994 Apr;87(4):518-21. [PubMed |
Full Text | DOI]
6. Severinghaus JW, Kelleher JF. Recent developments in pulse
oximetry. Anesthesiology. 1992 Jun;76(6):1018-38. [PubMed
| Full Text | DOI]
7. Wukitsch MW, Petterson MT, Tobler DR, Pologe JA. Pulse
oximetry: analysis of theory, technology, and practice. J Clin
Monit. 1988 Oct;4(4):290-301. [PubMed | Full Text | DOI]
8. Iyriboz Y, Powers S, Morrow J, Ayers D, Landry G. Accuracy
of pulse oximeters in estimating heart rate at rest and during
exercise. Br J Sports Med. 1991 Sep;25(3):162-4. [PubMed |
Full Text | DOI]
9. Barker SJ, Tremper KK. Pulse oximetry: applications and
limitations. Int Anesthesiol Clin. 1987 Fall;25(3):155-75.
[PubMed | Full Text | DOI]
10. Blaisdell CJ, Goodman S, Clark K, Casella JF, Loughlin GM.
Pulse oximetry is a poor predictor of hypoxemia in stable
children with sickle cell disease. Arch Pediatr Adolesc Med.
2000 Sep;154(9):900-3. [PubMed | Full Text | DOI]
11. Lebecque P, Shango P, Stijns M, Vliers A, Coates AL. Pulse
oximetry versus measured arterial oxygen saturation: a
comparison of the Nellcor N100 and the Biox III. Pediatr
Pulmonol. 1991;10(2):132-5. [PubMed | Full Text | DOI]
12. Fanconi S. Reliability of pulse oximetry in hypoxic infants. J
Pediatr. 1988 Mar;112(3):424-7. [PubMed | Full Text | DOI]
13. Fanconi S. Pulse oximetry and transcutaneous oxygen
tension for detection of hypoxemia in critically ill infants
and children. Adv Exp Med Biol. 1987;220:159-64. [PubMed
| Full Text | DOI]
14. Schmitt HJ, Schuetz WH, Proeschel PA, Jaklin C. Accuracy
of pulse oximetry in children with cyanotic congenital heart
disease. J Cardiothorac Vasc Anesth. 1993 Feb;7(1):61-5.
[PubMed | Full Text | DOI]
15. Severinghaus JW, Naifeh KH, Koh SO. Errors in 14 pulse
oximeters during profound hypoxia. J Clin Monit. 1989
Apr;5(2):72-81. [PubMed | Full Text | DOI]
16. Nickerson BG, Sarkisian C, Tremper K. Bias and precision
of pulse oximeters and arterial oximeters. Chest. 1988
Mar;93(3):515-7. [PubMed | Full Text | DOI]
17. Jensen LA, Onyskiw JE, Prasad NG. Meta-analysis of arterial
oxygen saturation monitoring by pulse oximetry in adults.
Heart Lung. 1998 Nov-Dec;27(6):387-408. [PubMed | Full
Text | DOI]
18. Carter BG, Carlin JB, Tibballs J, Mead H, Hochmann M,
Osborne A. Accuracy of two pulse oximeters at low arterial
hemoglobin-oxygen saturation. Crit Care Med. 1998
Jun;26(6):1128-33. [PubMed | Full Text | DOI]
19. Chiappini F, Fuso L, Pistelli R. Accuracy of a pulse oximeter
in the measurement of the oxyhaemoglobin saturation. Eur
Respir J. 1998 Mar;11(3):716-9. [PubMed | Full Text]
20. Levin KP, Hanusa BH, Rotondi A, Singer DE, Coley CM,
Marrie TJ, Kapoor WN, Fine MJ. Arterial blood gas and
pulse oximetry in initial management of patients with
community-acquired pneumonia. J Gen Intern Med. 2001
Sep;16(9):590-8. [PubMed | Full Text | DOI]
21. Razi E, Akbari H. A comparison of arterial oxygen saturation
measured both by pulse oximeter and arterial blood gas
analyzer in hypoxemic and non-hypoxemic pulmonary
diseases. Turkish Respiratory Journal. 2006 Aug;7(2):43-7.
[Full Text]
22. Kanai R, Moriyama K, Kohyama T, Yorozu T. Reliability of
Oxygen Saturation by Pulse Oximeter to Detect Hypoxemia
of Patients in the Intensive Care Unit Anesth Analg. 2012
Rauniyar et al. Study of Oxygen Saturation by Pulse Oximetry and Arterial Blood Gas in ICU Patients: A...
793
Free Full Text Articles are Available at www.jnma.com.np
JNMA I VOL 58 I ISSUE 230 I OCTOBER 2020
May;113:159. [Full Text]
23. Webb RK, Ralston AC, Runciman WB. Potential errors in
pulse oximetry. II. Effects of changes in saturation and signal
quality. Anaesthesia. 1991 Mar;46(3):207-12. [PubMed | Full
Text | DOI]
24. Welch JP, DeCesare R, Hess D. Pulse oximetry:
instrumentation and clinical applications. Respir Care. 1990
Jun;35(6):584-97. [Full Text]
25. Wahr JA, Tremper KK. Noninvasive oxygen monitoring
techniques. Crit Care Clin. 1995 Jan;11(1):199-217. [PubMed]
26. Reynolds KJ, Moyle JT, Sykes MK, Hahn CE. Response of 10
pulse oximeters to an in vitro test system. Br J Anaesth. 1992
Apr;68(4):365-9. [PubMed | Full Text | DOI]
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Rauniyar et al. Study of Oxygen Saturation by Pulse Oximetry and Arterial Blood Gas in ICU Patients: A...
... В ряде исследований проводилось сравнение данных сатурации, полученных с помощью пульсоксиметрии с инвазивным способом измерения сатурации с помощью газоанализатора. Так, в исследовании Rauniyar N, et al. (2020) при изучении 101 пациента, находившихся в блоке интенсивной терапии, было получено, что процент совпадений между вышеуказанными двумя методами составил 83,2%, при этом пульсоксиметрия имела 84,6% чувствительность и 83% специфичность в измерении сатурации [20]. Авторы пришли к выводу, что пульсоксиметрия имеет высокую точность измерения сатурации при исходном ее уровне >90% и в этом случае может использоваться вместо анализа газового состава крови [20]. ...
... Так, в исследовании Rauniyar N, et al. (2020) при изучении 101 пациента, находившихся в блоке интенсивной терапии, было получено, что процент совпадений между вышеуказанными двумя методами составил 83,2%, при этом пульсоксиметрия имела 84,6% чувствительность и 83% специфичность в измерении сатурации [20]. Авторы пришли к выводу, что пульсоксиметрия имеет высокую точность измерения сатурации при исходном ее уровне >90% и в этом случае может использоваться вместо анализа газового состава крови [20]. ...
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Full-text available
  • Oct 2024
Vital signs are important health parameters because they indicate the physiological functions of the human body. Heart rate (HR), blood pressure, body temperature, oxygen saturation (SpO 2 ), and respiration rate are vital signs used to determine whether a person is healthy or not. HR is the rate at which the heart pumps blood and is measured by the number of heart beat per minute (beats per minute / BPM). Oxygen saturation (SpO 2 ) indicates the level of hemoglobin in the blood that can bind to oxygen. This study aims to develop a smart band prototype for monitoring heart rate (HR) and oxygen saturation using optical spectroscopy methods and the implementation of the Internet of Things (IoT). This smart band prototype uses the MAX30102 sensor, ESP32, push button, Blynk, and Arduino IDE AVR software. The research results show that the prototype’s accuracy for HR measurement is ±98.5%, and the accuracy for SpO 2 is ±99.3%. The measurement results can be sent and displayed in the Blynk application as well as to email. It can be concluded that this smart band can detect HR and SpO 2 in real-time and has the potential to improve the quality of healthcare services.
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... 1,87,98 The normal blood oxygen saturation level is 95-100%. 95,96 The abnormalities of oxygenation level, critically below 80%, 3,97 even for a short period may ultimately result in the failure of vital organs, especially the brain and heart, and even death. 1,2,99 Moreover, if the SpO2 level falls below 90%, it may indicate hypoxemia, 100,101 and, if left untreated, can lead to respiratory or cardiac arrest. ...
CRITICAL OXYGEN SATURATION-LEVEL ESTIMATION FROM PHOTOPLETHYSMOGRAM (PPG): A PRISMA- COMPLIANT SYSTEMATIC REVIEW AND META-ANALYSIS
Article
Full-text available
  • Oct 2024
Objectives: Photoplethysmogram (PPG) signals have become a crucial tool in the non-invasive monitoring of oxygen saturation levels (SpO2). The main purpose of the present review is to perform a meta-analysis of the involvement and consideration of critical SpO2 levels (<90%) in the research papers where SpO2 levels are calculated/ predicted from PPG and to elaborate on the impact of the critical levels when presenting the evaluation results. Data sources: PubMed, Science Direct, and Scopus were searched for papers published between January 1, 2016, and September 10, 2022. Results: This study produced several results, concerning the main objective as well as other important issues for improving the SpO2 estimation/calculation. We discovered that only 21 out of 75 papers considered SpO2 values that are in the critical domain. Many papers do not provide access to their databases or disclose the software/models used. Additionally, some studies lack sufficient testing subjects and fail to make their results reproducible. The findings reveal a preference for SpO2 calculation over prediction, limited data availability , undisclosed methodologies, and diverse evaluation metrics hinder replication and direct comparisons between studies. Also, a scoring table is offered that scores higher the papers that are more valuable for SpO2 calculation/ prediction.Conclusion: Employing PRISMA guidelines, a comprehensive search across PubMed, Science Direct, and Scopus databases initially extracted 6173 potential papers. Following rigorous screening, 75 papers were selected for detailed analysis, of which only 21 included data from critical SpO2 levels. Furthermore, this research provided information for the filtered 21 paper about the sample size of the study participants, the models utilized to derive the results, the availability of databases, the specific devices employed in the research, the methodologies employed for PPG signal measurement, and the collaborative efforts among authors from different institutions. This information is sublimed in the scoring table which gives higher scoring to those papers that are more valuable for SpO2 calculation/prediction. This study offers references to all these findings that can be used as concrete guidelines for prospective researchers and developers of new sensors for SpO2 estimation/calculation utilizing PPG signals. ABBREVIATIONS PPG = Photoplethysmogram SpO2 = Blood oxygen saturation RMSE = Root-mean-square error MAE = Mean absolute error RMSPE = Root-mean-square percentage error TRE = Total relative error AMAE = Average mean absolute error AMSE = Average mean squared error RMSEP = Root mean square error of prediction. STRENGTHS AND LIMITATIONS OF THIS STUDY • This is the first systematic review and meta-analysis to evaluate the inclusion of critical oxygen saturation levels when estimated from PPG. • Several other factors are assessed in studies examining critical SpO2 levels, including the number of subjects involved, the types of models used, database availability, device types, methods of PPG signal measurement, and collaboration between different institutions. • The main limitation of this research is the high level of heterogeneity among the studies in presenting their results, which poses challenges in assessing their quality regarding the interest of this research.
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... These attendance and dropout rates may presumably be due to individualized exercise and face-to-face supervision by continuous assessment with the RPE scale and VAS (external focus of attention) [58], which remained in safe ranges for both groups. Both scales showed no exacerbations of acute pain, even though the AE-BFR group developed greater volume over the distance run than the AE group, maintaining SpO 2 in a safe range [59] and reflecting the absence of hypoxemia. This suggests that support through various scales may be more in line with the intensity, recovery, and self-management needs of patients with fibromyalgia, with greater control, motivation, safety, effects, and feasibility of aerobic training program with blood flow restriction in this population (self-efficacy) [9]. ...
Feasibility, Safety, and Effects of an Aerobic Training Program with Blood Flow Restriction on Functional Capacity, and Symptomatology in Women with Fibromyalgia: A Pilot Study
Article
Full-text available
  • Aug 2024
Background: Evidence suggests that aerobic training with blood flow restriction is beneficial for treating fibromyalgia. This study evaluated the feasibility, safety, and effects of an aerobic training program with blood flow restriction for women with fibromyalgia. Methods: Thirty-seven women with fibromyalgia were included, and thirteen with an average age of 59 ± 3, a BMI of 26 ± 3, and who were polymedicated started the intervention period. The intervention group performed aerobic exercise with blood flow restriction using occlusive bands placed in the upper part of the rectus femoris, with a total duration of 14 min of restriction divided into two periods of 7 min with a rest period of 3 min and a total session duration of 17 min. Pressure intensity was measured using the visual pain scale (VAS), scoring 7 out of 10 (n = 7). The non-intervention group performed aerobic exercise without restriction of blood flow for the same periods, rest periods, and total duration of the session (n = 6). The intervention included 2 weekly sessions with 72 h between aerobic walking for 9 weeks. Walking was measured individually using the rating of perceived exertion scale (RPE) with an intensity between 6 and 7 out of 10. Visual and verbal support for the VAS and RPE scale was always provided throughout the sessions supervised by the investigator. Functional capacity was assessed using tests (six-minute walk test, incremental shuttle walk test, knee extension and handgrip test by dynamometer, 30 s chair stand test, and timed up-and-go test). Symptomatology was assessed using questionnaires (Widespread Pain Index, Symptom Severity Score, Fibromyalgia Impact Questionnaire, and Multidimensional Fatigue Inventory), and blood samples were collected. Results: There were no adverse effects, and only one participant in the intervention group withdrew. Between-group and intragroup differences showed that the intervention group obtained improvements in the functional tests; CST p = 0.005; 6MWT p = 0.011; Handgrip p = 0.002; TUGT p = 0.002 with reduced impact of the disease according to the questionnaires; FIQ Stiffness p = 0.027 compared with the nonintervention group. Biochemical results remained within normal ranges in both groups. Conclusions: Blood flow-restricted aerobic training may be feasible, safe, and more effective than unrestricted aerobic training as a physical exercise prescription tool to improve cardiorespiratory fitness, strength, balance, and stiffness in women with fibromyalgia.
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Remote Photoplethysmography for Heart Rate and Blood Oxygenation Measurement: A Review
Article
  • Aug 2024
Usually measured through obtrusive contact-based methods, heart rate (HR) and peripheral oxygen saturation (SpO2) are critical physiological signs used by clinicians during emergency interventions. Remote Photoplethysmography (rPPG) allows for unobtrusive sensing of these vital signs for health monitoring in various settings. We present a review of rPPG-related research conducted including related processes and techniques, such as regions of interest (ROI) selection, extracting the raw signal, pre-processing data, applying noise reduction algorithms, Fast Fourier transforms (FFT), filtering and extracting these vital signs. Further, we present a detailed, critical evaluation of available rPPG systems. Limitations and future directions have also been identified to further advance this field.
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Intermittent hypoxia exposure at sea level improves functional capacity (6MWT) at high altitude
Article
Full-text available
  • Dec 2023
  • Indian J Physiol Pharmacol
Objectives Our primary objective is to observe whether acclimatisation is elicited by the intermittent hypoxic exposure (IHE) protocol. For this, we have utilised performance in a 6-min walk test (6MWT) as a tool to assess physiological responses to high altitude (HA) both in control and IHE-exposed groups, respectively. Materials and Methods The study was a prospective cohort study conducted on Indian army volunteers ( n = 57) and they were divided into two groups, a control group (CG) and an experimental group (EG). At the sea level, a baseline study was carried out on barometric pressure. IHE was performed at sea level in the normobaric hypoxia chamber (low fraction of inspired oxygen [FiO2], at normal barometric pressure, 740 mmHg), in which the FiO2 of the chamber was artificially decreased using O2-filtering membranes. The oxygen percentage was constantly maintained at 12%-13%. After recording the baseline, the subjects were exposed to a normobaric hypoxia chamber at 12%-13% FiO2 (altitude – equivalent to 4350 m Approx). Heart rate and blood pressure (BP) were recorded with a battery-operated portable BP monitor (OMRON) at both locations. A finger pulse oximeter probe was set on the right index finger to measure the resting oxygen saturation (SpO2) level (Model MU 300). Incidence of acute mountain sickness (AMS) was scored with the help of the standard Lake Louise questionnaire (LLS). Total LLS scores more than >3 (range 0–15) were considered AMS. Results EG individuals that went through IHE performed better at 6MWT at Stage I ( P = 0.03). EG also had better SpO2, levels as compared to CG ( P = 0.00) at Stage II ( P = 0.03). Furthermore, there was a significant difference in the Borg’s Scale between CG and EG. The Delta SpO2 of EG was better as compared to CG in all stages, albeit not significant ( P = 0.07). There was a significant difference between IHE and CG groups, and CG was at an increased risk for lower SpO2 (8.00 [1.21–52.60], P = 0.03). Conclusion The findings elucidate the benefits of IHE in rapid acclimatisation, and it contributed to better distance covered as shown by 6MWT as well and reduces hypoxic incidents in HA.
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Response of 10 pulse oximeters to an in vitro test system
Article
Full-text available
  • May 1992
Pulse oximeters are often used in situations in which severe hypoxaemia may occur. We have developed an in vitro system to test the accuracy of pulse oximeter calibration. The probe of10 different oximeters was attached to a model finger in an in vitro blood circuit, and pulse oximeter readings (Spo2) were compared with multi-wavelength in vitro oximeter readings (So2 over a range of So2 values from 50 to 100%. The oximeters tested varied widely in their accuracy and linearity. We conclude that the system can test the accuracy, reproducibility and linearity of response of pulse oximeter readings at low oxyhaemoglobin saturations.
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Accuracy of pulse oximeters in estimating heart rate at rest and during exercise
Article
Full-text available
  • Oct 1991
Pulse oximeters are being widely used for non-invasive, simultaneous assessment of haemoglobin oxygen saturation. They are reliable, accurate, relatively inexpensive and portable. Pulse oximeters are often used for estimating heart rate at rest and during exercise. However, at present the data available to validate their use as heart rate monitors are not sufficient. We evaluated the accuracy of two oximeters (Radiometer, ear and finger probe; Ohmeda 3700, ear probe) in monitoring heart rate during incremental exercise by comparing the pulse oximeters with simultaneous ECG readings. Data were collected on eight men (713 heart rate readings) during graded cycle ergometer and treadmill exercise to volitional fatigue. Analysis by linear regression revealed that general oximeter readings significantly correlated with those of ECG (r = 0.91, P less than 0.0001). However, comparison of heart rate at each level of work showed that oximeter readings significantly (P less than 0.05) under-estimated rates above 155 beats/min. These results indicate that the use of pulse oximeters as heart rate monitors during strenuous exercise is questionable. This inaccuracy may well originate from the instability of the probes, sweating, other artefacts during exercise, and measurement of different components in the cardiovascular cycle.
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Reliability of Pulse Oximetry During Exercise in Pulmonary Patients
Article
  • Mar 1990
To evaluate the reliability of pulse oximetry during exercise, we studied 101 patients primarily with chronic pulmonary diseases. Three devices were used on different patients. Radial arterial blood was sampled at rest and maximal exercise simultaneously to pulse oximetric determination. Measured blood oxygen saturation was significantly different from noninvasive saturation at rest and also at exercise for each device. Nevertheless, changes in pulse oximetry from rest to exercise were significantly correlated with measured saturation for all three devices. Direction of changes in saturation from rest to exercise was correctly evaluated by transcutaneous oximetry in all but six instances where changes were less than 4 percent. Although measured and transcutaneous saturations are significantly different, we conclude that pulse oximetry reliably estimates changes in arterial saturation between rest and exercise for a clinical purpose. None of the three tested devices was better compared with the others in estimating saturation changes at exercise.
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Potential errors in pulse oximetry
Article
  • Mar 1991
  • ANAESTHESIA
The published studies of pulse oximeter performance under conditions of normal, high and low saturation, exercise, poor signal quality and cardiac arrhythmia are reviewed. Most pulse oximeters have an absolute mean error of less than 2% at normal saturation and perfusion; two-thirds have a standard deviation (SD) of less than 2%, and the remainder an SD of less than 3%. Some pulse oximeters tend to read 100% with fractional saturations of 97–98%. Pulse oximeters may be suitable hyperoxic alarms for neonates if the alarm limit chosen is directly validated for each device. Pulse oximeters are poorly calibrated at low saturations and are generally less accurate and less precise than at normal saturations; nearly 30% of 244 values reviewed were in error by more than 5% at saturations of less than 80%. Ear, nose and forehead probes respond more rapidly to rapid desaturation than finger probes, but are generally less accurate and less precise. Ear oximetry may be inaccurate during exercise. Low signal quality can result in failure to present a saturation reading, but data given with low signal quality warning messages are generally no less accurate than those without. Cardiac arrhythmias do not decrease accuracy of pulse oximeters so long as saturation readings are steady.
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Arterial Blood Gas and Pulse Oximetry in Initial Management of Patients with Community‐acquired Pneumonia
Article
  • Sep 2001
  • J GEN INTERN MED
Objective: To identify the factors associated with the use of arterial blood gas (ABG) and pulse oximetry (PO) in the initial management of patients with community-acquired pneumonia (CAP) and arterial hypoxemia at presentation. Participants: A total of 944 outpatients and 1,332 inpatients with clinical and radiographic evidence of CAP prospectively enrolled from 5 study sites in the United States and Canada. Analyses: Separate multivariate logistic regression analyses were used to 1) compare measurement of ABG and PO within 48 hours of presentation across sites while controlling for patient differences, and 2) identify factors associated with arterial hypoxemia (PaO2 <60 mm Hg or SaO2 <90% for non-African Americans and <92% for African Americans) while breathing room air. Results: Range of ABG use by site was from 0% to 6.4% (P =.06) for outpatients and from 49.2% to 77.3% for inpatients (P <.001), while PO use ranged from 9.4% to 57.8% for outpatients (P <.001) and from 47.9% to 85.1% for inpatients (P <.001). Differences among sites remained after controlling for patient demographic characteristics, comorbidity, and illness severity. In patients with 1 or more measurements of oxygenation at presentation, hypoxemia was independently associated with 6 risk factors: age >30 years (odds ratio [OR], 3.2; 95% confidence interval [CI], 1.7 to 5.9), chronic obstructive pulmonary disease (OR, 1.9; 95% CI, 1.4 to 2.6), congestive heart failure (OR, 1.5; 95% CI, 1.0 to 2.1), respiratory rate >24 per minute (OR, 2.3; 95% CI, 1.8 to 3.0), altered mental status (OR, 1.6; 95% CI, 1.1 to 2.3), and chest radiographic infiltrate involving >1 lobe (OR, 2.2; 95% CI, 1.7 to 2.9). The prevalence of hypoxemia among those tested ranged from 13% for inpatients with no risk factors to 54.6% for inpatients with > or =3 risk factors. Of the 210 outpatients who had > or =2 of these risk factors, only 64 (30.5%) had either an ABG or PO performed. In the 48 outpatients tested without supplemental O2 with > or =2 risk factors 8.3% were hypoxemic. Conclusions: In the initial management of CAP, use of ABG and PO varied widely across sites. Increasing the assessment of arterial oxygenation among patients with CAP is likely to increase the detection of arterial hypoxemia, particularly among outpatients.
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Pulse oximetry: Analysis of theory, technology, and practice
Article
  • Jan 1987
Interest in two-wavelength classic, that is, nonpulse, oximetry began early in the 20th century. Noninvasive in vivo measurements of oxygen saturation showed promise, but the methods were beset by several problems. The pulse oximetry technique, by focusing on the pulsatile arterial component, neatly circumvented many of the problems of the classic nonpulse arterial approach. Today's pulse oximeter owes a good measure of its success to the technologic advances in light emission and detection and the ready availability of microcomputers and their software. Many clinicians have recognized how valuable the assessment of the patient's oxygenation in real time can be. This appreciation has propelled the use of pulse oximeters into many clinical fields, as well as nonclinical fields such as sports training and aviation. Understanding how and what pulse oximetry measures, how pulse oximetry data compare with data derived from laboratory analysis, and how the pulse oximeter responds to dyshemoglobins, dyes, and other interfering conditions must be understood for the correct application and interpretation of this revolutionary monitor.
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Errors in 14 pulse oximeters during profound hypoxia
Article
  • Jun 1988
The accuracy of pulse oximeters from fourteen manufacturers was tested during profound brief hypoxic plateaus in 125 subject sets using 50 normal adult volunteers, of whom 29 were studied two to nine times. A data set usually consisted of 10 subjects, and 13 sets were collected between August 1987 and July 1988. In the first 6 sets, six 30-second hypoxic plateaus were obtained per subject at 556% oxyhemoglobin (O2Hb) (range, 40 to 70%). In the last 7 sets, three hypoxic plateaus were obtained at each of four levels, approximately 86, 74, 62, and 50% O2Hb, for the purpose of linear regression analysis. Inspired oxygen was adjusted manually breath by breath in response to arterial oxygen saturation computed on-line from end-tidal oxygen and carbon dioxide tensions. End-plateau arterial blood O2Hb was analyzed by a Radiometer OSM-3 oximeter, and plateau pulse oximeter saturation (SpO2) was read by cursor from a computer record of the analog output. Three to 13 instruments were tested simultaneously by using 1 to 3 duplicate instruments from each of one to seven manufacturers. Variations introduced by manufacturers were tested on subsequent sets in several instruments. An index of error, ambiguity () of oxygen saturation, was defined as the absolute sum of bias and precision (mean and SD of SpO2–O2Hb) at O2Hb=55.84.5%, preserving the sign when bias was significant atP. The data showed substantial differences in bias and precision between pulse oximeters at low saturations, the most common problems being underestimation of saturation and failing precision.
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Potential errors in pulse oximetry. II. Effects of changes in saturation and signal quality
Article
  • Apr 1991
The published studies of pulse oximeter performance under conditions of normal, high and low saturation, exercise, poor signal quality and cardiac arrhythmia are reviewed. Most pulse oximeters have an absolute mean error of less than 2% at normal saturation and perfusion; two-thirds have a standard deviation (SD) of less than 2%, and the remainder an SD of less than 3%. Some pulse oximeters tend to read 100% with fractional saturations of 97-98%. Pulse oximeters may be suitable hyperoxic alarms for neonates if the alarm limit chosen is directly validated for each device. Pulse oximeters are poorly calibrated at low saturations and are generally less accurate and less precise than at normal saturations; nearly 30% of 244 values reviewed were in error by more than 5% at saturations of less than 80%. Ear, nose and forehead probes respond more rapidly to rapid desaturation than finger probes, but are generally less accurate and less precise. Ear oximetry may be inaccurate during exercise. Low signal quality can result in failure to present a saturation reading, but data given with low signal quality warning messages are generally no less accurate than those without. Cardiac arrhythmias do not decrease accuracy of pulse oximeters so long as saturation readings are steady.
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