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blood oxygen saturation, photoplethysmography, reliability, plethysmography, perfusion index, oxygen saturation, oximeter
Cite this article as: Swain SM, Lata M, Kumar S, et al. (May 9, 2022) A cross-sectional study of the consistency of perfusion parameters measured across fingers with a handheld pulse oximeter in healthy adults. Cure 14(5): e24853. doi:10.7759/cureus.24853
Pulse oximeters measure oxygen saturation, heart rate, and perfusion index (PI) by analyzing photoplethysmographic signals. PI is a proxy for peripheral perfusion expressed as a percentage of pulsatile signal compared to non-pulsatile signal. PI measured in different locations may vary. PI may vary when measured on different fingers. In this study, we aimed to observe changes in PI between different fingers of both hands.
This cross-sectional observational study was conducted using a convenience sample drawn from a tertiary hospital in eastern India. PI was measured in apparently healthy adults in a sitting position after a five-minute rest. Attach a pulse oximeter probe to each finger and take readings after one minute. ANOVA and intraclass correlation coefficient (ICC) were calculated to compare the consistency between PIs.
Data were analyzed from 391 (229 [58.57%] men and 162 [41.43%] women) adult study participants with a mean age of 34.88 ± 10.65 years. The highest PI is the middle finger of both hands. There was a significant difference among the PI measured on different fingers, F (9, 3900) = 15.49, p <0.0001. There was a significant difference among the PI measured on different fingers, F (9, 3900) = 15.49, p < 0.0001. Между PI, измеренными на разных пальцах, была достоверная разница, F (9, 3900) = 15,49, p <0,0001. There was a significant difference between PI measured on different fingers, F(9, 3900) = 15.49, p<0.0001.不同手指测得的PI 有显着差异，F (9, 3900) = 15.49, p <0.0001。不同手指测得的PI 有显着差异，F(9, 3900) = 15.49, p<0.0001。 PI, измеренный разными пальцами, достоверно различался, F (9, 3900) = 15,49, p < 0,0001. PI measured with different fingers was significantly different, F(9, 3900) = 15.49, p < 0.0001. The ICC was 0.474, 0.368, and 0.635 for overall, right-hand, and left-hand fingers, respectively, which indicate poor (ICC < 0.5) to moderate (ICC = 0.5-0.75) levels of reliability. The ICC was 0.474, 0.368, and 0.635 for overall, right-hand, and left-hand fingers, respectively, which indicate poor (ICC < 0.5) to moderate (ICC = 0.5-0.75) levels of reliability. ICC составлял 0,474, 0,368 и 0,635 для общего пальца правой и левой руки соответственно, что указывает на низкий (ICC <0,5) или умеренный (ICC = 0,5-0,75) уровень надежности. The ICC was 0.474, 0.368, and 0.635 for the common finger of the right and left hands, respectively, indicating a low (ICC <0.5) or moderate (ICC = 0.5-0.75) level of reliability.总体、右手和左手手指的ICC 分别为0.474、0.368 和0.635，这表明可靠性较差(ICC < 0.5) 到中等(ICC = 0.5-0.75) 水平。总体、右手和左手手指的ICC 分别为0.474、0.368和0.635，这表明可靠性较差(ICC < 0.5) ICC для общего, правого и левого пальцев составил 0,474, 0,368 и 0,635 соответственно, что указывает на низкий (ICC <0,5) и умеренный (ICC = 0,5-0,75) уровни надежности. The ICC for the common, right, and left fingers was 0.474, 0.368, and 0.635, respectively, indicating low (ICC < 0.5) and moderate (ICC = 0.5-0.75) levels of reliability.
PI measured on different fingers with a household pulse oximeter can give different readings. The highest PI value is on the middle finger. Clinicians and primary care physicians should be aware of differences in PI measurements across fingers and use readings with caution for any diagnostic purposes.
Pulse oximetry is the simplest non-invasive method for measuring blood oxygen saturation [1]. Portable, consumer and affordable pulse oximeters are already on the market as home health monitoring devices [2]. In the home and hospital setting, pulse oximeters are usually attached to the fingertips and sometimes to the earlobes or toes. The meter probe contains a photoplethysmographic sensor that helps analyze the relative absorption of red and infrared waves by oxygenated and deoxygenated pulsatile blood flow [3].
In addition to measuring oxygen saturation, pulse oximeters also provide a perfusion index (PI). PI is a proxy for the status of peripheral perfusion. The pulsatile signal (generated by arterial flow) is expressed as a percentage of the non-pulsatile signal (blood stasis) to calculate PI [4]. PIs are used in a variety of clinical settings, including intensive care units, perioperative monitoring during caesarean section, and stellate ganglion blockade to measure their effectiveness [5–7].
A previous study by Sapra et al. Among medical workers, the highest PI is the ring finger of the right hand, and the lowest is the thumb of the right hand [8]. In contrast, Tripathy et al. It has been shown that PI measured on different fingers is different, with the highest value for the middle finger and the lowest value for the little finger [9]. However, to our knowledge, no studies have established the validity of PI measurements across fingers.
In this context, this study aimed to compare the PI of fingers of both hands in apparently healthy people. The results of this study will help to detect the variability and validity of PI values measured between different fingers using pulse oximetry. Based on the results, primary care physicians can decide whether the PI measured by a portable oximeter can be used to detect poor perfusion.
This study was conducted among adult (aged >18 years) research participants recruited from a tertiary care teaching hospital located in eastern India. This study was conducted among adult (aged >18 years) research participants recruited from a tertiary care teaching hospital located in eastern India. This study was conducted in adult (over 18 years of age) study participants recruited from a tertiary clinical hospital located in eastern India.这项研究是在从位于印度东部的一家三级护理教学医院招募的成人（年龄> 18 岁）研究参与者中进行的。 18 岁）研究参与者中Это исследование было проведено среди взрослых (возраст > 18 лет) участников исследования, набранных из клинической больницы третичного уровня, расположенной в восточной Индии. This study was conducted in adult (age >18 years) study participants recruited from a tertiary clinical hospital located in eastern India. Participants were informed about the aims, nature and significance of the study, with a focus on the study procedure. After the briefing, those who gave written consent to participate were included in the study. The study was formally approved by the Institutional Ethics Committee (reference: HMCH/IEC/2022/160).
This was a cross-sectional observational study conducted in the clinical physiology laboratory of the hospital. The laboratory is lit with natural light and diffused white light. There is no direct sunlight or artificial rays near the place where the measurements were taken. The study was conducted from January to February 2022.
A study by Tripathi et al. Variations in oxygen saturation and PI were found in the fingers of the left and right hands [9]. Using the study as a benchmark, we calculated the minimum sample size using the following inputs: α = 0.05 (p value ≤ 0.05 was considered statistically significant), β = 0.1 (study power was 90%), mean PI on the left and right in the middle. finger = 3.3 and 2.7, the expected standard deviation is 1.7. The estimated sample size is 337 [10].
We obtained a point-in-time convenience sample (January 2022 to February 2022) from a tertiary clinical hospital. The inclusion criteria included a declaration of apparently healthy status of the participants and providing written consent for voluntary participation by adults aged >18 years. The inclusion criteria included a declaration of apparently healthy status of the participants and providing written consent for voluntary participation by adults aged >18 years. Inclusion criteria included a statement of apparent healthy state of participants and the provision of written consent for voluntary participation by adults over the age of 18. Inclusion criteria included a statement of the participant's apparent medical condition and written consent for voluntary participation by adults over 18 years of age. Participants with any acute or chronic disease, taking any medication for a disease, having high blood pressure, having any vascular disease, and having any pigmentation disorder of the fingers were excluded from the final study sample.
All measurements were taken between 10:00 and 12:00 to avoid any potential influence of circadian rhythms. Age was recorded in the total number of years declared by the study participants. Use a handheld rangefinder to measure height with an accuracy of 0.1 cm. Weight is measured on a digital scale with an accuracy of ±0.1 kg. Use a fiberglass tape measure to measure your waist and hips to the nearest 0.1 cm to calculate your waist to hip ratio. All measurements were performed by clinical professionals experienced in anthropometric measurements in the presence of same-sex laboratory staff.
We used a BPL Smart Oxy pulse oximeter (BPL Medical Technologies Pvt. Ltd., Bangalore, India) to measure PI. On fig. 1a shows the readings of the sample on the screen of the pulse oximeter, and in fig. 1b shows a sensor attached to a finger.
(a) Screen showing heart rate, oxygen saturation, and perfusion index readings. (b) Measurement of parameters with an oximeter on the middle finger of the left hand.
Study participants were seated and PI measurements were taken after a five-minute rest. Although there is evidence that PI is lowest in the sitting position, we considered this position for the convenience of the participants and set limits [11]. Also, since this was a comparative study, the effect of posture on the measured PI was not significant. The nails are colorless and there are no temporary or permanent tattoos on the fingers. The pulse oximeter sensors are attached to the fingers one by one. After one minute of application to a specific finger, take readings and save them for further analysis by seeing stable readings on the screen for at least three seconds.
The data were tested for normality using the Shapiro-Wilk test. Accordingly, statistical tests were chosen (parametric tests for normally distributed data and non-parametric tests for non-normally distributed data) [12]. Variables between males and females were analyzed using an unpaired t-test. The variance of PI between fingers was tested using analysis of variance (ANOVA). Consistency between measurements was tested using an intra-class correlation coefficient (ICC) model corresponding to our measurement type [13]. The ICCs of <0.5, 0.5-0.75, 0.76-9, and >0.9 were considered “poor,” “moderate,” “good,” and “excellent” reliability, respectively [14]. The ICCs of <0.5, 0.5-0.75, 0.76-9, and >0.9 were considered “poor,” “moderate,” “good,” and “excellent” reliability, respectively [14]. ICC <0,5, 0,5-0,75, 0,76-9 и >0,9 считались «плохими», «умеренными», «хорошими» и «отличными» надежностью соответственно [14]. ICC <0.5, 0.5-0.75, 0.76-9 and >0.9 were considered "poor", "moderate", "good", and "excellent" reliability, respectively [14]. <0.5、0.5-0.75、0.76-9 和>0.9 的ICC 分别被认为是“差”、“中等”、“好”和“优秀”的可靠性[14]。 <0.5、0.5-0.75、0.76-9 和>0.9 的ICC ICC <0,5, 0,5-0,75, 0,76-9 и >0,9 считались «плохими», «умеренными», «хорошими» и «отличными» надежностью соответственно [14]. ICC <0.5, 0.5-0.75, 0.76-9 and >0.9 were considered "poor", "moderate", "good", and "excellent" reliability, respectively [14]. Correlation coefficients from ± 0.0 to ± 0.3, from ± 0.31 to ± 0.5, from ± 0.51 to ± 0.7, from ± 0.71 to ± 0.9 and from ± 0, 91 to ±1 were considered "minor", "low", "moderate", "high". , ", and "very high", respectively [15]. Statistical analysis was performed using GraphPad Prism 6.01 (GraphPad Software, Inc., USA) and SPSS version 20 (IBM Corp., Armonk, New York, USA). For all the tests, p-values of <0.05 were considered statistically significant. For all the tests, p-values of <0.05 were considered statistically significant. Для всех тестов значения p <0,05 считались статистически значимыми. For all tests, p values <0.05 were considered statistically significant.对于所有测试，p 值<0.05 被认为具有统计学意义。对于所有测试，p 值<0.05 被认为具有统计学意义。 Значение p <0,05 считалось статистически значимым для всех тестов. A p value <0.05 was considered statistically significant for all tests.
The number of study participants initially included in the study and the final sample after exclusion are shown in Figure 2.
Data were analyzed from 391 adult study participants with a mean age of 34.88 ± 10.65 years. Mean age was 35.1 ± 10.76 years for men (n = 229 [58.57%]) and 34.56 ± 10.52 years for women (n = 162 [41.43%]) (unpaired t- test, p = 0.62). Table 1 presents the age and anthropometric variables by sex. Male participants had higher height, weight, and body mass index (BMI).
R: right hand finger; L: finger of the left hand; 1-5: index fingers from thumb to little finger; CI: confidence interval
The PIs from thumb to little finger of the right hand were 3.98 ± 1.91, 3.57 ± 1.89, 4.66 ± 2.18, 3.45 ± 1.65, and 3.5 ± 1.78, respectively. The PIs from the left thumb to the little finger were 3.94 ± 1.99, 3.61 ± 2.11, 4.37 ± 2.07, 3.79 ± 2.32, and 3.54 ± 2.3, respectively. The highest PI falls on the middle fingers of both hands. There was a significant difference among the PI measured on different fingers (F (9, 3900) = 15.49, p <0.0001) (repeated-measures ANOVA) (Figure 3). There was a significant difference among the PI measured on different fingers (F(9, 3900) = 15.49, p<0.0001) (repeated-measures ANOVA) (Figure 3). Наблюдалась значительная разница между PI, измеренными на разных пальцах (F (9, 3900) = 15,49, p <0,0001) (ANOVA с повторными измерениями) (рис. 3). There was a significant difference between PI measured on different fingers (F(9, 3900) = 15.49, p < 0.0001) (repeated measures ANOVA) (Figure 3).在不同手指上测量的PI 之间存在显着差异(F (9, 3900) = 15.49, p <0.0001) (重复测量方差分析) (图3)。在不同手指上测量的PI 之间存在显着差异(F(9, 3900) = 15.49, p<0.0001) Наблюдалась значительная разница (F(9, 3900) = 15,49, p <0,0001) между PI, измеренными на разных пальцах (повторные измерения ANOVA) (рис. 3). There was a significant difference (F(9, 3900) = 15.49, p < 0.0001) between PI measured on different fingers (repeated measures ANOVA) (Figure 3).
"R" means "right", "L" - "left", and the numbers from 1 to 5 represent from the thumb to the little finger. Repeated-measures ANOVA result: F (9, 3900) = 15.49, p < 0.0001. Repeated-measures ANOVA result: F(9, 3900) = 15.49, p < 0.0001. Результат повторных измерений ANOVA: F (9, 3900) = 15,49, p <0,0001. Result of repeated measures ANOVA: F(9, 3900) = 15.49, p < 0.0001.重复测量方差分析结果：F (9, 3900) = 15.49，p < 0.0001。重复测量方差分析结果：F(9, 3900) = 15.49，p < 0.0001。 Результаты повторных измерений ANOVA: F (9, 3900) = 15,49, p <0,0001. Repeated measures ANOVA results: F(9, 3900) = 15.49, p < 0.0001.
According to Tukey's post hoc test, there were 17 significant group differences and 28 non-significant group differences, as shown in Figure 4.
Baseline bars indicate non-significant differences (17 significant group differences and 28 non-significant group differences). "R" means "right", "L" - "left", and the numbers from 1 to 5 represent from the thumb to the little finger.
Pearson's inter-element correlation coefficients PI, measured over 10 fingers, are shown in Table 3. Statistically significant positive correlations were shown between all pairs of elements. The coefficients range from (R3 to L2) 0.133 to (L4 to L5) 0.798.
R1-R5: right thumb to right little finger; L1-L5: left thumb to left little finger. All correlation coefficients were statistically significant. Interpretation of correlation coefficients: from ±0.0 to ±0.3, from ±0.31 to ±0.5, from ±0.51 to ±0.7, from ±0.71 to ±0.9, from ± 0.91 to ±1 are considered "minor", "low", "moderate", "high". and "Very high" respectively.
The correlation between the left and right middle finger was 0.287 (CI = 0.193 to 0.375; p < 0.0001). The correlation between the left and right middle finger was 0.287 (CI = 0.193 to 0.375; p < 0.0001). Корреляция между средним пальцем левой и правой руки составила 0,287 (ДИ от 0,193 до 0,375; p < 0,0001). The correlation between the left and right middle fingers was 0.287 (CI 0.193 to 0.375; p < 0.0001).左右中指之间的相关性为0.287（CI = 0.193 至0.375；p < 0.0001）。左右中指之间的相关性为0.287（CI = 0.193 至0.375；p < 0.0001）。 Корреляция между средними пальцами левой и правой руки составила 0,287 (ДИ от 0,193 до 0,375; р<0,0001). The correlation between the left and right middle fingers was 0.287 (CI 0.193 to 0.375; p<0.0001). The correlation with the trend line is shown in the scatter plot in Figure 5.
The ICC for all, right and left fingers was 0.474, 0.368, and 0.635 (Table 4), indicating "poor", "poor", and "moderate" measurement reliability, respectively.
According to the data, ICC Model 3 was used with the input of SPSS as a "two-sided mixed" model and a "totally consistent" type.
With regard to the fit between PIs measured on 10 fingers, we found significant differences between the measurements. The middle finger shows the highest PI measured among the fingers of the hand. Although the correlation between PI of the left and right middle fingers was statistically significant, the coefficient of determination (r2) indicated that approximately 8% of changes in the PI of the left middle finger could be predicted from the right middle finger and vice versa [16].
PI is calculated from the photoplethysmography signal by comparing pulsatile and non-pulsatile peripheral circulation. Two major factors can influence PI, cardiac output, and the balance between the sympathetic and parasympathetic nervous systems.
PI is high if cardiac output is high and/or parasympathetic predominates. Conversely, PI is low when cardiac output is low and/or sympathetic predominates. The normal range of PI is considered to be from 0.2% to 20% [17]. In our study, we found a PI of 4.37 ± 2.07% for the left middle finger and 4.66 ± 2.18% for the right middle finger. However, we did not measure cardiac output and the autonomic nervous system to comment on the respective states of the cardiac and nervous system. Our results confirm the data of Savastan et al. Apparently healthy individuals with a mean age of 42 years (interquartile range = 33–47) had a PI of 4.3 (interquartile range = 2.9–6.2) [18].
In the physiological state, posture affects the measured PI, which was found to be lowest in the sitting position and highest in the Trendelenburg position [11]. In our study, we used the sitting position for all participants. Therefore, when we compare on the fingers, we assume that the PI is at the lowest level. Because PI is the ratio of pulsatile to non-pulsatile blood flow, any disease that impairs peripheral blood flow affects PI [19]. PI in the emergency department helps determine the need for blood transfusion [20]. It also helps to assess the risk of death in patients with upper gastrointestinal bleeding and in mechanically ventilated patients [21,22]. In addition, it helps to detect hypotension during anesthesia and determine the effectiveness of ganglionic blockades [6,7]. In an intensive care setting, a pulse oximeter is an integral part of monitoring other parameters in a single hospital-level facility. However, in this study, we used consumer-grade devices. Thus, the results of this study may not be comparable to studies using hospital-grade oximeters.
Consumer grade pulse oximeters can be used by primary care physicians and general practitioners for home visits to measure a patient's oxygen saturation (SpO2) and PI. They should take precautions to minimize transmission of the disease between patients using probes or fingertips [23]. However, they must be careful as PI measured on different fingers can give different readings. Previous studies have shown that the middle finger shows higher levels of SpO2 compared to other fingers [24,25]. In this study, we found that PI also showed the highest scores in the middle finger of both limbs.
This study has some limitations. We collected samples for research from the hospital. Convenience samples are low-probability samples. Therefore, it is impossible to assess how well he represents the population. In addition, we only collected samples from apparently healthy individuals for PI determination under normal physiological conditions. Therefore, the results may not apply to people with any particular medical condition.
Portable and household pulse oximeters can measure PI differently on different fingers of the left and right hand. The highest PI values were obtained on the middle finger of each hand. The reliability of PI measured with a pulse oximeter on different fingers is low. Therefore, PI obtained with an oximeter should be interpreted with caution for any diagnostic purpose. Further research is needed to compare the reliability of hospital and consumer oximeters in measuring the PI of different fingers.
Department of Physiology, Department of Physiology, School of Medicine and Hospital, Patna, Indiana National Insurance Company Staff
Department of Physiology, Department of Physiology, School of Medicine and Hospital, Patna, Indiana National Insurance Company Staff
Department of Physiology, Department of Physiology, School of Medicine and Hospital, Patna, Indiana National Insurance Company Staff
Human Subjects: All participants in this study gave or did not give consent. Approval HMCH/IEC/2022/160 was issued by the Institutional Ethics Committee of Bhubaneswar Medical College and High Tech Hospital. Animal Subjects: All authors confirmed that no animals or tissues were involved in this study. Conflicts of Interest: In accordance with the ICMJE Uniform Disclosure Form, all authors declare the following: Payment/Service Information: All authors declare that they did not receive financial support from any organization for the submitted work. Financial Relationships: All authors declare that they do not currently or within the past three years have financial relationships with any organization that may be interested in the submitted work. Other Relationships: All authors declare that there are no other relationships or activities that may affect the submitted work.
We thank all participants for their active participation in this study. We also thank Sarika Mondal, freelance medical writer, for the technical editing of the manuscript and for contributing to the images used in this manuscript. The correspondent would like to thank Ahana Aarshi for her tender support during the preparation of this manuscript. We thank the reviewers of this manuscript for their careful review and constructive comments.
Swain SM, Lata M, Kumar S et al. (May 9, 2022) A cross-sectional study of the consistency of perfusion parameters measured across fingers with a portable pulse oximeter in healthy adults. Cure 14(5): e24853. doi:10.7759/cureus.24853
© Copyright 2022 Swain et al. This is an open access article distributed under the terms of the Creative Commons Attribution License CC-BY 4.0. Unlimited use, distribution, and reproduction in any medium is permitted, provided the original author and source are credited.
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the author and source are credited.
(a) Screen showing heart rate, oxygen saturation, and perfusion index readings. (b) Measurement of parameters with an oximeter on the middle finger of the left hand.
"R" means "right", "L" - "left", and the numbers from 1 to 5 represent from the thumb to the little finger. Repeated-measures ANOVA result: F (9, 3900) = 15.49, p < 0.0001. Repeated-measures ANOVA result: F(9, 3900) = 15.49, p < 0.0001. Результат повторных измерений ANOVA: F (9, 3900) = 15,49, p <0,0001. Result of repeated measures ANOVA: F(9, 3900) = 15.49, p < 0.0001.重复测量方差分析结果：F (9, 3900) = 15.49，p < 0.0001。重复测量方差分析结果：F(9, 3900) = 15.49，p < 0.0001。 Результаты повторных измерений ANOVA: F (9, 3900) = 15,49, p <0,0001. Repeated measures ANOVA results: F(9, 3900) = 15.49, p < 0.0001.
Post time: Nov-07-2022