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A Cross-Sectional Study on the Agreement of Perfusion Indexes Measured on Different Fingers by a Portable Pulse Oximeter in Healthy Adults

Authors:
  • ESICMCH ,Bihta
  • Raiganj Government Medical College and Hospital

Abstract and Figures

Background Pulse oximeters measure oxygen saturation, heart rate, and perfusion index (PI) by analyzing photoplethysmographic signals. PI is an indirect measure of peripheral perfusion expressed as a percentage of pulsatile signals to non-pulsatile signals. PI measured from different sites may show variation. PI may vary when measured on different fingers. In this study, we aimed to observe the variation of PI among different fingers of both hands. Methodology This cross-sectional, observational study was conducted using a convenience sample recruited from a tertiary care hospital in eastern India. PI was measured in apparently healthy adults in a sitting posture after a five-minute rest. The pulse oximeter probe was attached to each finger and readings were taken after one minute. The analysis of variance and intraclass correlation coefficient (ICC) were calculated to compare and find agreement among PI. Results Data from a total of 391 (229 [58.57%] male and 162 [41.43%] female) adult research participants with a mean age of 34.88 ± 10.65 years were analyzed. The PI was the highest on the middle finger in both hands. There was a significant difference among the PI measured on different fingers, 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. Conclusions The PI measured using consumer-grade pulse oximeters on different fingers may provide different readings. The highest PI reading is found on the middle finger. Clinicians and primary care physicians should consider the differences in measured PI among different fingers and should use the readings with caution for any diagnostic purposes.
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A Cross-Sectional Study on the Agreement of
Perfusion Indexes Measured on Different Fingers
by a Portable Pulse Oximeter in Healthy Adults
Sharada M. Swain , Manju Lata , Sandeep Kumar , Shaikat Mondal , Joshil K. Behera , Himel Mondal
1. Department of Physiology, Hi-Tech Medical College and Hospital, Bhubaneswar, IND 2. Department of Physiology,
Employees' State Insurance Corporation Medical College and Hospital, Patna, IND 3. Department of Physiology,
Raiganj Government Medical College and Hospital, Raiganj, IND 4. Department of Physiology, Saheed Laxman Nayak
Medical College and Hospital, Koraput, IND
Corresponding author: Himel Mondal, himelmkcg@gmail.com
Abstract
Background
Pulse oximeters measure oxygen saturation, heart rate, and perfusion index (PI) by analyzing
photoplethysmographic signals. PI is an indirect measure of peripheral perfusion expressed as a percentage
of pulsatile signals to non-pulsatile signals. PI measured from different sites may show variation. PI may
vary when measured on different fingers. In this study, we aimed to observe the variation of PI among
different fingers of both hands.
Methodology
This cross-sectional, observational study was conducted using a convenience sample recruited from a
tertiary care hospital in eastern India. PI was measured in apparently healthy adults in a sitting posture after
a five-minute rest. The pulse oximeter probe was attached to each finger and readings were taken after one
minute. The analysis of variance and intraclass correlation coefficient (ICC) were calculated to compare and
find agreement among PI.
Results
Data from a total of 391 (229 [58.57%] male and 162 [41.43%] female) adult research participants with a
mean age of 34.88 ± 10.65 years were analyzed. The PI was the highest on the middle finger in both hands.
There was a significant difference among the PI measured on different fingers, 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.
Conclusions
The PI measured using consumer-grade pulse oximeters on different fingers may provide different readings.
The highest PI reading is found on the middle finger. Clinicians and primary care physicians should consider
the differences in measured PI among different fingers and should use the readings with caution for any
diagnostic purposes.
Categories: Anesthesiology, Family/General Practice, Internal Medicine
Keywords: oximetry, photoplethysmography, reliability, plethysmography, perfusion index, oxygen saturation,
oximeter
Introduction
Pulse oximetry is the easiest non-invasive method to measure oxygen saturation in the blood [1]. Portable,
consumer-grade, and affordable pulse oximeters are available in the market and can be used as a home
health monitoring device [2]. Pulse oximeters are commonly attached to the fingertips in home and hospital
settings and are sometimes attached to the ear lobe or toe. The probe of the meters contains
photoplethysmograph sensors that help analyze the comparative absorption of a red and infrared wave by
oxygenated and deoxygenated pulsatile blood flow [3].
In addition to measuring oxygen saturation, pulse oximeters provide a perfusion index (PI). PI is an indirect
measure of peripheral perfusion status. The pulsatile signal (produced by arterial flow) is expressed as a
percentage of the non-pulsatile signal (stagnant blood) to compute the PI [4]. PI is used in various clinical
settings, including critical care settings, perioperative monitoring during cesarean sections, and while
performing a stellate ganglion block to measure its efficacy [5-7].
1 2 2 3 2 4
Open Access Original
Article DOI: 10.7759/cureus.24853
How to cite this article
Swain S M, Lata M, Kumar S, et al. (May 09, 2022) A Cross-Sectional Study on the Agreement of Perfusion Indexes Measured on Different Fingers
by a Portable Pulse Oximeter in Healthy Adults. Cureus 14(5): e24853. DOI 10.7759/cureus.24853
A previous study by Sapra et al. reported that the highest PI is found on the right ring finger and the lowest
on the right thumb among healthcare workers [8]. In contrast, Tripathy et al. showed that PI measured on
different fingers varies, with the middle finger having the highest value, and the little finger having the
lowest value [9]. However, to our knowledge, no study has ascertained the reliability of PI measurements on
different fingers.
With this background, this study aimed to compare PI in fingers of both hands in apparently healthy
individuals. The findings of this study would help find the variation and reliability of PI measured among
different fingers using a pulse oximeter. According to the findings, primary care physicians can decide if the
PI measured by portable oximeters can be used to detect poor perfusion.
Materials And Methods
Ethics
This study was conducted among adult (aged >18 years) research participants recruited from a tertiary care
teaching hospital located in eastern India. The participants were briefed about the aims, nature, and
implications of the study with an emphasis on the study procedure. After the briefing, those who provided
written consent for participation were included in the study. A formal clearance from the Institutional Ethics
Committee was obtained for the study (reference: HMCH/IEC/2022/160).
Type and settings
This was a cross-sectional, observational study conducted in the clinical physiology laboratory of the
hospital. The laboratory was illuminated by both natural and diffuse white light. There were no direct sun
rays or artificial light beams near the site where the measurements were done. The study was conducted
from January to February 2022.
Minimum sample size
A study by Tripathi et al. found that there is a variation in oxygen saturation and PI in left and right-hand
fingers [9]. Considering the study as a reference, we calculated the minimum sample size with the following
input: α = 0.05 (p-value ≤0.05 was considered statistically significant), β = 0.1 (power of the study was 90%),
and the mean PI in the right and left middle finger = 3.3 and 2.7 with an expected standard deviation of 1.7.
The calculated sample size was 337 [10].
Recruitment
We obtained a convenience sample from a particular point in time (January to February 2022) from a tertiary
care teaching 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. Participants
with any acute or chronic disease, taking medicine for any disease, suffering from hypertension, suffering
from any vascular diseases, and suffering from any pigment disorder of fingers were excluded from the final
study sample.
Measurements
All measurements were conducted between 10 am and 12 pm to avoid any potential effect of the circadian
rhythm. Age was recorded in completed years as declared by the research participants. Height was measured
using a portable stadiometer to the nearest 0.1 cm. Weight was measured on a digital weighing scale with an
accuracy of ±0.1 kg. Waist circumference and hip circumference were measured using a fiberglass measuring
tape to the nearest 0.1 cm to calculate the waist-to-hip ratio. All measurements were done by an expert
clinician with experience in anthropometric measurements in the presence of a same-sex attendant in the
laboratory.
We used BPL Smart Oxy Pulse Oximeter (BPL Medical Technologies Pvt. Ltd., Bengaluru, India) for
measuring the PI. Figure 1a shows a sample reading on the oximeter screen, and Figure 1b shows the probe
attached to a finger.
2022 Swain et al. Cureus 14(5): e24853. DOI 10.7759/cureus.24853 2 of 11
FIGURE 1: A portable pulse oximeter.
(a) Screen showing a reading of heart rate, oxygen saturation, and perfusion index. (b) Measuring parameters
using the oximeter on the left middle finger.
The research participants were in a sitting posture, and the PI measurements were obtained after a five-
minute rest. Although there is evidence that PI is the lowest in a sitting posture, we considered this position
for participants’ convenience and the limitations of the settings [11]. Furthermore, because it is a
comparative study, there would be a negligible effect of posture on the measured PI. The nails were without
any color, and the fingers were without any temporary or permanent tattoo. The pulse oximeter probe was
attached to the fingers one by one. After one minute of attachment on a particular finger, the reading was
taken after a stable reading was seen on the screen for at least three seconds and stored for further analysis.
Statistical analysis
Data were tested for normality using the Shapiro-Wilk Test. The statistical tests were selected accordingly
(normally distributed data by parametric test and non-normally distributed data by non-parametric tests)
[12]. Variables between males and females were analyzed using the unpaired t-test. The variance of PI among
fingers was tested by analysis of variance (ANOVA). Agreements among the measurements were tested using
the intraclass correlation coefficient (ICC) model which is suitable for 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 correlation coefficients ±0.0 to ±0.3, ±0.31 to ±0.5, ±0.51 to ±0.7, ±0.71 to ±0.9, and
±0.91 to ±1 were considered “negligible,” “low,” “moderate,” “high,” and “very high,” respectively [15]. The
statistical analyses were carried out in GraphPad Prism 6.01 (GraphPad Software, Inc., USA) and SPSS
version 20 (IBM Corp., Armonk, NY, USA). For all the tests, p-values of <0.05 were considered statistically
significant.
Results
The number of research participants initially recruited in the study and the final sample after exclusion is
2022 Swain et al. Cureus 14(5): e24853. DOI 10.7759/cureus.24853 3 of 11
shown in Figure 2.
FIGURE 2: Flowchart illustrating participant recruitment.
PI: perfusion index
Data of 391 adult research participants with a mean age of 34.88 ± 10.65 years were analyzed. The mean age
of males (n = 229 [58.57%]) was 35.1 ± 10.76 years and of females (n = 162 [41.43%]) was 34.56 ± 10.52 years
(unpaired t-test, p = 0.62). The age and anthropometric variables according to gender are shown in Table 1.
The height, weight, and body mass index (BMI) were higher among male participants.
2022 Swain et al. Cureus 14(5): e24853. DOI 10.7759/cureus.24853 4 of 11
Variable Overall (n = 391) Male (n = 229) Female (n = 162) P-value
Age (years) 34.88 ± 10.65 35.1 ± 10.76 34.56 ± 10.52 0.62
Height (cm) 152.19 ± 10.52 154.47 ± 12.43 148.97 ± 5.6 <0.0001*
Weight (kg) 61.97 ± 9.04 65.74 ± 8.09 56.64 ± 7.49 <0.0001*
Body mass index (kg/m2)27.02 ± 4.89 27.98 ± 5.17 25.66 ± 4.13 <0.0001*
Waist-to-hip ratio 0.85 ± 0.4 0.85 ± 0.04 0.84 ± 0.05 0.06
TABLE 1: Overall and sex-wise age and anthropometric parameters of the participants.
*Statistically significant p-values using the unpaired t-test.
Descriptive statistics of the measured PI on different fingers are shown in Table 2.
Statistics R1 R2 R3 R4 R5 L1 L2 L3 L4 L5
Mean 3.98 3.57 4.66 3.45 3.5 3.94 3.61 4.37 3.79 3.54
Standard deviation 1.91 1.89 2.18 1.65 1.78 1.99 2.11 2.07 2.32 2.3
Minimum 0.9 0.8 0.9 0.8 0.8 0.8 0.8 0.8 0.8 0.8
25% percentile 2.2 2.1 3 2.2 2.1 2.6 1.7 3 2.2 2
Median 3.9 4 4.6 3.3 3.1 3.4 3 4 3 3.1
75% percentile 5.4 5 5.9 4.6 5 5 5.1 5.4 5 4.4
Maximum 8.4 8.4 12.6 9.8 7 12.8 7 8.9 9.2 10
Standard error of mean 0.09 0.09 0.11 0.08 0.09 0.1 0.11 0.1 0.12 0.12
Lower 95% CI 3.79 3.38 4.44 3.29 3.32 3.74 3.39 4.17 3.56 3.32
Upper 95% CI 4.17 3.75 4.88 3.62 3.68 4.13 3.82 4.58 4.02 3.77
TABLE 2: Descriptive statistics of measured perfusion index on 10 fingers using a portable pulse
oximeter in the sample (n = 391).
R: right-hand fingers; L: left-hand fingers; 1-5: finger number from the thumb to the little finger; CI: confidence interval
The PI in the order of the right thumb to the little finger was 3.98 ± 1.91, 3.57 ± 1.89, 4.66 ± 2.18, 3.45 ± 1.65,
and 3.5 ± 1.78, respectively. The PI in the order of the left thumb to the little finger was 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 was found on 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) (repeated-measures ANOVA) (Figure 3).
2022 Swain et al. Cureus 14(5): e24853. DOI 10.7759/cureus.24853 5 of 11
FIGURE 3: Perfusion index measured on 10 fingers using a portable
pulse oximeter.
“R” indicates right and “L” indicates left, and the number from 1 to 5 indicates thumb to the little finger. Repeated-
measures ANOVA result: F (9, 3900) = 15.49, p < 0.0001.
ANOVA: analysis of variance
According to Tukey’s post-hoc test, there were 17 significant and 28 non-significant group differences, as
shown in Figure 4.
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FIGURE 4: Difference between group means in Tukey’s post-hoc test
among perfusion index measured in different fingers.
Bar touching the zero line indicates a non-significant difference (there were 17 significant and 28 non-significant
group differences). “R” indicates right and “L” indicates left, and the number from 1 to 5 indicates thumb to the little
finger.
The inter-item Pearson correlation coefficients of PI measured on 10 fingers are shown in Table 3. All items
showed a statistically significant positive correlation between the pairs. The coefficients ranged from (R3
versus L2) 0.133 to (L4 versus L5) 0.798.
2022 Swain et al. Cureus 14(5): e24853. DOI 10.7759/cureus.24853 7 of 11
R1 R2 R3 R4 R5 L1 L2 L3 L4 L5
R1 1.000
R2 0.503 1.000
R3 0.464 0.377 1.000
R4 0.223 0.430 0.496 1.000
R5 0.289 0.581 0.185 0.442 1.000
L1 0.521 0.620 0.510 0.611 0.551 1.000
L2 0.380 0.581 0.133 0.488 0.669 0.701 1.000
L3 0.420 0.393 0.287 0.443 0.470 0.592 0.648 1.000
L4 0.432 0.549 0.198 0.536 0.504 0.587 0.703 0.652 1.000
L5 0.485 0.671 0.288 0.454 0.564 0.520 0.688 0.604 0.798 1.000
TABLE 3: Inter-item correlation matrix of perfusion index measured on 10 fingers among the 391
research participants.
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 coefficient: ±0.0 to ±0.3, ±0.31 to ±0.5, ±0.51 to ±0.7, ±0.71 to ±0.9, and ±0.91 to ±1 considered to be “negligible,” “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 with the trend line is shown in a scatterplot in Figure 5.
FIGURE 5: Scatter plot of PI of the left and right middle finger with the
trendline.
PI: perfusion index
The ICC was 0.474, 0.368, and 0.635 for overall, right-hand, and left-hand fingers, respectively (Table 4),
indicating “poor,” “poor,” and “moderate” reliability, respectively, among the measurements.
2022 Swain et al. Cureus 14(5): e24853. DOI 10.7759/cureus.24853 8 of 11
ICC (single measure)
95% CI F test with true value 0
Lower bound Upper bound Value df1 df2 P
Overall 0.474 0.431 0.518 10.688 390 3510 <0.0001
Right 0.368 0.310 0.427 4.252 390 1650 <0.0001
Left 0.635 0.59 0.679 10.262 390 1650 <0.0001
TABLE 4: Intraclass correlation coefficients of overall, right, and left-hand finger perfusion index
measurement.
According to the data, ICC model 3 was used with SPSS input as a “two-way mixed” model and “absolute agreement” type.
ICC: intraclass correlation coefficient; CI: confidence interval
Discussion
Regarding the agreement among PI measured on 10 fingers, we found a significant difference among the
measurements. The middle finger showed the highest measured PI among the fingers of a hand. Although
the correlation between the PI of the left and right middle finger was statistically significant, the coefficient
of determination (r2) shows that approximately 8% of the variation in PI from the left middle finger can be
predicted from the right middle finger, or vice versa [16].
The PI is calculated from the photoplethysmographic signals by comparing the pulsatile to non-pulsatile
peripheral circulation. Two principal factors may influence PI, namely, cardiac output and the balance
between the sympathetic and parasympathetic nervous systems.
If there is higher cardiac output and/or parasympathetic predominance, there is higher PI. In contrast, when
the cardiac output is lower and/or sympathetic predominance, there is low PI. The normal range of PI is
considered to be between 0.2% and 20% [17]. In our study, we found the PI in the left middle finger to be 4.37
± 2.07% and the right middle finger to be 4.66 ± 2.18%. However, we did not measure the cardiac output and
autonomic nervous system to comment on the associated cardiac and nervous system status. Our findings
corroborate those of Savastan et al. who found the PI to be 4.3 (interquartile range = 2.9-6.2) among
apparently healthy subjects with a median age of 42 (interquartile range = 33-47) years [18].
At the physiological state, posture can affect the measured PI, and it is found that it is the lowest in the
sitting posture and the highest in the Trendelenburg position [11]. In our study, we used the sitting posture
in all participants. Hence, we presume that the PI was at the lowest level when we compared it on the
fingers. As the PI is the ratio of pulsatile to non-pulsatile blood flow, any disease that compromises the
blood flow to the periphery would affect the PI [19]. The PI in emergency departments helps in the
identification of the need for transfusion [20]. It also helps to estimate the mortality risk in patients
presenting with upper gastrointestinal bleeding and mortality in mechanically ventilated patients [21,22].
Moreover, it helps in the detection of hypotension during anesthesia and to identify the effectiveness of
ganglion blocks [6,7]. In intensive care settings, pulse oximetry is an integral part of monitoring other
parameters in single hospital-grade devices. However, we used a consumer-grade device in this study.
Hence, the results of this study may not be compared with studies where hospital-grade oximeters were
used.
Primary care physicians and general physicians may use consumer-grade pulse oximeters for home visits for
measuring the oxygen saturation (SpO2) of patients and PI. They should take precautions to minimize the
patient-to-patient transmission of disease by using probes or finger covers [23]. However, they should be
cautious that PI measured on different fingers may show different readings. Previous studies have
established that the middle fingers show higher SpO2 levels when compared with other fingers [24,25]. In
this study, we found that the PI also shows the highest reading on the middle finger in both limbs.
Limitations
This study has some limitations. We recruited the study sample from a hospital. The convenience sample is a
non-probability sample. Hence, it is not possible to estimate how well it represents the population. In
addition, we only recruited the sample from apparently healthy individuals to determine PI in normal
physiology. Hence, the study findings may not be extended to people with any particular diseases.
2022 Swain et al. Cureus 14(5): e24853. DOI 10.7759/cureus.24853 9 of 11
Conclusions
The PI measured by portable and consumer-grade pulse oximeters on different fingers of the left and right
hand may be different. The highest reading of PI is obtained on the middle finger in each hand. There is poor
reliability of measured PI on different fingers by a pulse oximeter. Hence, the PI obtained from oximeters
should be interpreted with caution for any diagnostic purposes. Further studies need to be conducted to
compare the reliability of hospital-grade and consumer-grade oximeters in the measurement of PI on
different fingers.
Additional Information
Disclosures
Human subjects: Consent was obtained or waived by all participants in this study. Institutional Ethics
Committee, Hi-Tech Medical College and Hospital, Bhubaneswar issued approval HMCH/IEC/2022/160.
Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue.
Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the
following: Payment/services info: All authors have declared that no financial support was received from
any organization for the submitted work. Financial relationships: All authors have declared that they have
no financial relationships at present or within the previous three years with any organizations that might
have an interest in the submitted work. Other relationships: All authors have declared that there are no
other relationships or activities that could appear to have influenced the submitted work.
Acknowledgements
We thank all the participants for their active participation in this study. We also thank Sarika Mondal, a
freelance medical writer, for the technical editing of the manuscript and for contributing to the images used
in this manuscript. The corresponding author would like to thank Ahana Aarshi for her affectionate support
during the preparation of this manuscript. We thank the peer reviewers of this manuscript for meticulously
reviewing the article and providing constructive comments.
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Pharmacol. 2021, 11:1411-5. 10.5455/njppp.2021.11.10392202103112021
2022 Swain et al. Cureus 14(5): e24853. DOI 10.7759/cureus.24853 11 of 11
... This is quantified as the peripheral perfusion index (PPI) and calculated as the ratio of the pulsatile component to the nonpulsatile component of the transmitted infrared light intensity [10,11]. In contrast to capillary refill time, PPI can quantitatively and continuously evaluate peripheral perfusion; therefore, they have been used in many clinical studies in recent years [9,12]. 1 1 2 1 1 Pulse oximeter probes are usually attached to the index or middle fingers [13]; however, the PPI values vary between fingers [14,15]. A pulse oximeter probe may cause burns when worn at the same site for a long time, especially in patients with peripheral hypoperfusion [16,17]; therefore, changing the site frequently has been recommended [18]. ...
... However, changes in PPI values owing to probe replacement reduce the reliability of clinical and research applications. Previous studies that reported the interfinger differences in PPI values have the problem that they evaluated by sequentially changing one probe on each finger [14,15]. As peripheral perfusion fluctuates from moment to moment in response to neural activity and other factors [19], these studies may not have been able to evaluate PPI at the same point in time. ...
... As peripheral perfusion fluctuates from moment to moment in response to neural activity and other factors [19], these studies may not have been able to evaluate PPI at the same point in time. Additionally, when a clip-type probe was used [15], differences in finger thickness may have caused changes in the pressure exerted on the finger tissue, which affected the PPI value [20]. Overall, no two fingers with equivalent PPI values suitable for probe replacement have yet been identified. ...
... Based on the available literature, there are only two studies to date that have compared the perfusion index between the fingers of the hands [21,22]. However, the measurements on the fingers were not continuous and simultaneous and only under normal SpO2. ...
... During the initial stabilization phase, the lowest median values were observed on the little finger (1.4%) and the highest median values were observed on the thumb (2.1%), with the other three fingers in between. The values of PI are basically in line with the values presented by Lima et al. [1], in contrast to the studies by Swain et al. [21] and Sapra et al. [22], where the values were 2 to 3 times higher than in the present study. ...
... In the Swain et al. study [21], the highest PI values were measured on the middle fingers and the lowest on the little fingers. PI values measured on the thumbs of both hands in the Sapra et al. study [22] were lower than on the other fingers, which is inconsistent with the results of this study. ...
... Instead, it often relies on subjective assessments of pain, temperature, and motor changes, which can be imprecise and delayed (3). Since sympathetic blockade precedes sensory and motor effects, objective measures like the PI and End-Diastolic Velocity (EDV) have gained interest (4,5). PI, derived from pulse oximetry, reflects tissue perfusion changes due to vasodilation after sympathetic blockade, while EDV, measured via Doppler ultrasound, tracks hemodynamic shifts (6). ...
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Objective There is a lack of reliable indicators for evaluating the success of ultrasound-guided Interscalene Brachial Plexus Block (ISBPB). This study investigates the effectiveness of Perfusion Index (PI) ratio and End-Diastolic Velocity (EDV) ratio for early assessment of ISBPB effects. Methods Eighty-nine patients, aged 18–65 with BMI 18–24 kg/m² and ASA grade I or II, underwent elective unilateral shoulder arthroscopic surgery. They received ultrasound-guided ISBPB with 15 mL local anesthetic (10 mL ropivacaine, 5 mL lidocaine). Patients were categorized into successful and failure groups based on needle test results after 30 min. PI and EDV of the brachial artery were recorded at baseline and at 5, 10, 15, 20, 25, and 30 min post-block. PI and EDV ratios were calculated by dividing values at each time by baseline. ROC curves were plotted at 5 and 10 min, and AUROC with 95% CI was calculated to assess block efficacy. Results Of 89 patients, 3 were excluded due to data loss and 2 withdrew, leaving 84 patients. Of these, 70 (83.3%) had successful blocks. In the successful group, both PI and EDV ratios on the blocked side significantly increased 5 min after the procedure. The PI ratio at 5 min had an AUROC of 0.894 (95% CI: 0.816–0.972), with a threshold of 1.22, sensitivity of 84.3%, and specificity of 85.7%. The EDV ratio had an AUROC of 0.706 (95% CI: 0.553–0.860), with a threshold of 1.32, sensitivity of 92.9%, and specificity of 50%. At 10 min, the PI ratio for assessing ISBPB impact had an AUROC of 0.901 (95% CI: 0.828–0.974), with a threshold of 1.4, sensitivity of 74.3%, and specificity of 92.9%. The AUROC for the EDV ratio was 0.799 (95% CI: 0.6788–0.921) with a threshold of 1.54, sensitivity of 92.9%, and specificity of 57.1%. The PI ratio at 5 min had a significantly higher AUROC than the EDV ratio, but no significant difference was found between PI ratios at 5 and 10 min. Conclusion Both PI ratio and EDV ratio assess ISBPB efficacy. The PI ratio provides a more precise evaluation, with optimal assessment at 5 min post-procedure. Clinical trial registration Chinese Clinical Trial Registry: ChiCTR2200066874.
... Even when PI is measured on fingers, there is a difference between the measured PI values depending on which finger is used for measurement. A cross-sectional study showed that the highest PI value was found on the middle finger of both hands [4]. ...
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Perfusion Index (PI) is an important vital sign in medical practice, with increasing utility in a variety of medical specialties. Its relevance extends to critical care and serves as a valuable measure of anesthetic efficacy. Despite its growing importance, there is a notable lack of literature on the potential impact of different surgical positions on PI measurements. Therefore, this study attempts to fill this gap by investigating whether PI exhibits variance in four different surgical positions: supine, prone, right and left lateral decubitus. The interventional prospective study included 27 volunteers who underwent PI measurement in each position in a randomized order. Using a one-way analysis of variance (ANOVA) for repeated measures, the results showed that at a 5% significance level, no significant differences were found in measured PI values between supine, prone, right and left lateral decubitus positions. Higher standard deviations in the right (±4.46%) and left (±4.58%) lateral decubitus positions indicate greater PI variability than in the supine (±3.91%) and prone (±3.88%) positions. The results suggest consistency of PI measurements across different surgical positions, adding to the knowledge of standardization of PI measurements and interpretation of measured absolute PI values.
... This concept is supported by several clinical studies, although until now direct systematic comparisons linking PPG amplitude to blood perfusion are lacking. PPI values obtained from a single device and their variation among fingers in 391 healthy subjects indicated a range between 3.54% to 4.66% with the middle right finger yielding the largest mean value [25]. PPI measurements in 20 healthy volunteers who experienced simulated blood volume reduction via lower body negative pressure demonstrated reduced PPI values in response [26]. ...
... Moreover, the PI value varies on different fingers [16]. In healthy adults, Swain et al. [17] found the highest PI was obtained via the middle finger, while Sapra et al. [18] recorded the maximal PI via the right-hand ring finger. Further investigations are required to validate the relevance of obtaining PI at different measurement sites. ...
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The peripheral perfusion index (PI) is derived from pulse oximetry and is defined as the ratio of the pulse wave of the pulsatile portion (arteries) to the non-pulsatile portion (venous and other tissues). A growing number of clinical studies have supported the use of PI in various clinical scenarios, such as guiding hemodynamic management and serving as an indicator of outcome and organ function. In this review, we will introduce and discuss this traditional but neglected indicator of the peripheral microcirculatory perfusion. Further clinical trials are required to clarify the normal and critical values of PI for different monitoring devices in various clinical conditions, to establish different standards of PI-guided strategies, and to determine the effect of PI-guided therapy on outcome.
... SV and SVV were monitored using a HemoSphere Advanced Monitoring Platform (Edwards, Irvine, CA, USA). PI was measured using Radical-7 (Masimo Corp., Irvine, CA, USA) at the middle finger of the contralateral arm, into which the arterial line was inserted to avoid the influence of arterial catheterisation on the digital perfusion [13,14]. The mode of display of PI was set to the "long-term" mode, which displays the averaged PI value over 30 s. ...
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Background Tracking preload dependency non-invasively to maintain adequate tissue perfusion in the perioperative period can be challenging.The effect of phenylephrine on stroke volume is dependent upon preload. Changes in stroke volume induced by phenylephrine administration can be used to predict preload dependency. The change in the peripheral perfusion index derived from photoplethysmography signals reportedly corresponds with changes in stroke volume in situations such as body position changes in the operating room. Thus, the peripheral perfusion index can be used as a non-invasive potential alternative to stroke volume to predict preload dependency. Herein, we aimed to determine whether changes in perfusion index induced by the administration of phenylephrine could be used to predict preload dependency. Methods We conducted a prospective single-centre observational study. The haemodynamic parameters and perfusion index were recorded before and 1 and 2 min after administering 0.1 mg of phenylephrine during post-induction hypotension in patients scheduled to undergo surgery. Preload dependency was defined as a stroke volume variation of ≥ 12% before phenylephrine administration at a mean arterial pressure of < 65 mmHg. Patients were divided into four groups according to total peripheral resistance and preload dependency. Results Forty-two patients were included in this study. The stroke volume in patients with preload dependency (n = 23) increased after phenylephrine administration. However, phenylephrine administration did not impact the stroke volume in patients without preload dependency (n = 19). The perfusion index decreased regardless of preload dependency. The changes in the perfusion index after phenylephrine administration exhibited low accuracy for predicting preload dependency. Based on subgroup analysis, patients with high total peripheral resistance tended to exhibit increased stroke volume following phenylephrine administration, which was particularly prominent in patients with high total peripheral resistance and preload dependency. Conclusion The findings of the current study revealed that changes in the perfusion index induced by administering 0.1 mg of phenylephrine could not predict preload dependency. This may be attributed to the different phenylephrine-induced stroke volume patterns observed in patients according to the degree of total peripheral resistance and preload dependency. Trial registration University Hospital Medical Information Network (UMIN000049994 on 9/01/2023).
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The present protocol provides general recommendations based on the best evidence currently available for physiotherapists to use as a guide for the care of stroke patients during hospitalization. The Brazilian Early Stroke Rehabilitation Task Force, comprising physical therapy experts and researchers from different Brazilian states, was organized to develop this care protocol based on a bibliographical survey, including meta-analyses, systematic reviews, clinical trials, and other more recent and relevant scientific publications. Professionals working in stroke units were also included in the task force to ensure the practicality of the protocol in different contexts. This protocol provides guidance on assessment strategies, safety criteria for the mobilization of patients with stroke, recommendations for mobilization and proper positioning, as well as evidence-based practices for treatment during hospitalization, including preventive measures for shoulder pain and shoulder-hand syndrome. The protocol also provides information on the organization of the physiotherapy service at stroke units, guidelines for hospital discharge, and quality indicators for physiotherapy services. We have included detailed activities that can be performed during mobilization in the supplementary material, such as postural control training, sensory and perceptual stimulation, task-oriented training, and activities involving an enriched environment. The protocol was written in a user-friendly format to facilitate its application in different social and cultural contexts, utilizing resources readily available in most clinical settings.
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Background Perfusion index (PI) is a simple, objective, and noninvasive method for evaluating the success of brachial plexus blocks. There is only one study which assessed the time point at which the PI had the best predictive value. Aims Of the 5 measured outcome variables (i.e.; PI at baseline, at 5 min, at 10 min, and at 15 min and PI ratio), we wanted to determine the one which had the best predictive value for block success. Materials and Methods It is a prospective observational study done in a tertiary care teaching hospital. Sixty-nine patients of either sex, American Society of Anesthesiologists Physical Status I and II, between the ages of 18 and 65 years posted for elective upper limb surgery were included. Patients were given supraclavicular blocks with a peripheral nerve stimulator. PI recorded at baseline, 5 min, 10 min, and 15 min. A PI ratio was calculated. Sensory and motor blocks were assessed at 5-min intervals. Statistical Analysis Descriptive analysis was applied by mean and standard deviation for quantitative variables and frequency and proportion for categorical variables. Receiver operating characteristic (ROC) curves were constructed. SPSS version 22 was used to detect an area under the ROCs (AUROC) curve and calculated to assess how good a test PI at 10 and 15 min and PI ratio are in predicting the outcome of a block. Results The mean PI increased continuously from the baseline till 15 min in successful blocks, but in unsuccessful blocks, the rise was not seen. ROC curves showed an AUROC curve of 0.93 in case of PI at 15 min and 0.84 for PI ratio. Conclusion We conclude that PI at 15 min is the best in our study and PI ratio is the next best as a predictor for evaluating success of supraclavicular blocks.
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Aims: The aim of this study was to research the effect of different bed head angles on the hemodynamic parameters of intensive care patients lying in the supine position. Methods: This study was a non-randomized and non-controlled, quasi-experimental repeated measures study. The study was conducted with 50 intensive care patients aged 18 and over in a general surgery intensive care unit in Turkey. With each patient in the supine position, the bed head was raised to an angle of 0°, 20°, 30°, and 45° without a pillow, and the hemodynamic parameters of central venous pressure, systolic and diastolic blood pressure, heart rate, breathing rate, and peripheral oxygen saturation were recorded after 0 and 10 min. Results: It was found that the mean central venous pressure value measured at min 0 and 10 was higher when the intensive care patients' bed head angle was raised to 45° than when the bed head was at an angle of 0° or 20° (p < .05). It was found that the patients' other hemodynamic parameters were not affected by different bed head angles. Conclusions: It was concluded as a result of this research that in intensive care patients in the supine position, only central venous pressure was affected by bed head angle, and that central venous pressure measurement can be reliably made at a bed head angle of 30°.
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Introduction Research data are first organized and visualized with the help of descriptive statistics. The next step is the inferential statistics. Result of the inferential statistics helps to conclude the finding. Many researchers and medical students may not have access to dedicated software for biostatistics. Aim This study aimed to provide a guide on the conduct of common inferential statistics that can be done online. Methods Common inferential statistical tests for both numerical data and categorical data were described in this study. All the tests were conducted online and the process is described step by step with example data. Results The following tests were described-one-sample t -test, one-sample median test, unpaired t -test, Mann–Whitney U -test, paired t -test, Wilcoxon signed-rank test, one-way analysis of variance (ANOVA), Kruskal–Wallis test, repeated-measure ANOVA, Friedman Test, Pearson correlation test, Spearman correlation test, Binomial test, Chi-square test, Fisher's exact test, and MacNemar test. All these tests could be conducted online from a computer connected to the internet. Conclusion We could conduct common inferential statistical tests online without any installed software. Anyone without prior data analysis knowledge may conduct the tests with example data on any internet browser. We presume that these would help the medical undergraduate and postgraduate students.
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Background: Consumer-grade pulse oximeters are used to monitor blood oxygen levels (SpO2) at home. Sharing a pulse oximeter with family members in isolation centers or home isolation due to COVID-19 may increase the chances of cross-infection. Aim: We aimed to find if using commonly available disposable polyethylene covers either on the finger and/or on the pulse oximeter provides the same reading of SpO2 or not. Methods: Two operators measured SpO2 on 10 healthy subjects with three randomly selected pulse oximeters. Six types of commonly available polythene bags (transparent, translucent, and opaque) were used to cover the fingers and/or device. After measuring the baseline SpO2 (i.e., without using covers), the measurements were taken with a covered finger, and/or covered oximeter probe. Results: The mean age of the research participants (five male, five female) was 23.9 ± 5.11 years. Perfusion index was 9.12 ± 1.63 (males 9.6 ± 1.42, females 8.64 ± 1.85, P = 0.38). Black opaque polyethylene bag as finger or probe cover did not detect any signal. There was no difference in SpO2 reading when a pulse oximeter probe is covered, and/or a finger is covered. There was excellent inter-observer and inter-device agreement. Conclusion: Commonly available transparent and translucent polyethylene plastic bags may be used as finger or pulse oximeter cover without compromising the SpO2 reading. However, an opaque black plastic bag is not suitable for finger or probe cover. These easily available and cheap pulse oximeter covers may be used by multiple patients or family members in an emergency like the COVID-19 pandemic with the potential to prevent cross-infection.
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Background: Many scoring systems for predicting mortality, rebleeding and transfusion needs among patients with upper gastrointestinal bleeding (UGIB) have been developed. However, no scoring system can predict all these outcomes. Objective: To show whether the perfusion index (PI), compared with the Rockall score (RS), helps predict transfusion needs and prognoses among patients presenting with UGIB in emergency departments. In this way, critical patients with transfusion needs can be identified at an early stage. Design and setting: Prospective cohort study in an emergency department in Turkey, conducted between June 2018 and June 2019. Methods: Patients' demographic parameters, PI, RS, transfusion needs and prognosis were recorded. Results: A total of 219 patients were included. Blood transfusion was performed in 174 patients (79.4%). The PI cutoff value for prediction of the need for blood transfusion was 1.17, and the RS cutoff value was 5. The area under the curve (AUC) value for PI (AUC: 0.772; 95% confidence interval, CI: 0.705-0.838; P < 0.001) was higher than for RS (AUC: 0.648; 95% CI: 0.554-0.741; P = 0.002). 185 patients (84.5%) were discharged, and 34 patients (15.5%) died. The PI cutoff value for predicting mortality was 1.1, and the RS cutoff value was 7. The AUC value for PI (AUC: 0.743; 95% CI: 0.649-0.837; P < 0.001) was higher than for RS (AUC: 0.725; 95% CI: 0.639-0.811; P < 0.001). Conclusion: PI values for patients admitted to emergency departments with UGIB on admission can help predict their need for transfusion and mortality risk.
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The plethysmographic peripheral perfusion index (PPI) is a very useful parameter with various emerging utilities in medical practice. The PPI represents the ratio between pulsatile and non-pulsatile portions in peripheral circulation and is mainly affected by two main determinants: cardiac output and balance between sympathetic and parasympathetic nervous systems. The PPI decreases in cases of sympathetic predominance and/or low cardiac output states; therefore, it is a useful predictor of patient outcomes in critical care units. The PPI could be a surrogate for cardiac output in tests for fluid responsiveness, as an objective measure of pain especially in un-cooperative patients, and as a predictor of successful weaning from mechanical ventilation. The PPI is simple to measure, easy to interpret, and has continuously displayed variables, making it a convenient parameter for detecting the adequacy of blood flow and sympathetic-parasympathetic balance.
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Home health monitoring devices are consumer-grade devices that help to monitor the health of individuals at home. These devices are usually low-cost and easily procurable, and they can be operated by patients or their caretakers with minimal training. However, improper usage of these devices may provide erroneous results, which can lead to an unnecessary hospital visit or teleconsultation. In this article, we discuss the basic technology and proper usage of some of these devices, namely automatic blood pressure monitors, blood glucose monitors, body fat monitors, pulse oximeters, electrocardiographs, digital thermometers, and infrared thermometers. This brief document intends to help primary health care professionals and their patients use these devices.
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Background and objectives: The perfusion index (PI) indicates the ratio of pulsatile blood flow in peripheral tissue to non-pulsatile blood flow. This study was performed to examine the blood perfusion status of tissues and organs of patients using synthetic cannabinoids (SCs). Materials and Methods: The records of patients aged 17 or over presenting to the adult emergency department due to SC use between 1 January 2016 and 31 December 2017 were examined in this single-center, retrospective, cross-sectional study. Examined factors included time from consumption of SC to presentation to the emergency department, as well as simultaneously determined systolic and diastolic blood pressures, heart rate (beats per min), Glasgow Coma Score (GCS), and PI values. Patients were divided into two groups, A and B, depending on the amount of time that had elapsed between SC consumption and presentation to the emergency department, and statistical data were compared. Results: The mean PI value in Group A was lower than that in Group B. Therefore, we concluded that peripheral tissue and organ blood perfusion is lower in the first 2 h following SC consumption than after 2 h. Systolic, diastolic, and mean arterial blood pressure and mean GCS values were also statistically significantly lower in Group A than in Group B. Conclusions: A decreased PI value may be an early sign of reduced-perfusion organ damage. PI is a practical and useful parameter in the early diagnosis of impaired organ perfusion and in monitoring tissue hypoxia leading to organ failure.
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Background Prognostication after an out-of-hospital cardiac arrest (OHCA) remains a challenge. The peripheral-derived perfusion index (PI) is a simple and non-invasive way to assess perfusion. We sought to assess whether the PI was able to discriminate the prognosis of patients resuscitated from an OHCA.Methods All the reports generated by the manual monitor/defibrillator (Corpuls 3 by GS Elektromedizinische Geräte G. Stemple GmbH, Germany) used for all the OHCAs who achieved ROSC treated by our Emergency Medical Service from January 2015 to December 2018 were reviewed. The mean PI value of each minute after ROSC was automatically provided by the device and the mean value of 30 min of monitoring (MPI30) was calculated. Pre-hospital data were collected according to the Utstein 2014 recommendations.ResultsAmong 1,909 resuscitation attempts, ROSC was achieved in 346 and it was possible to calculate an MPI30 in 164. MPI30 was higher in the patients who survived at 30 days [1.6 (95% CI 1.2–2.1) vs 1 (95% CI 0.8–1.3), p = 0.0017]. At the multivariable Cox regression model, after correction for shockable rhythm, witnessed status, bystander CPR, age, and blood pressure, MPI30 was found to be an independent predictor of both 30-day mortality [RR 0.83 (95% CI 0.69–0.99), p = 0.036] and 30-day mortality or poor neurologic outcome [RR 0.85 (95% CI 0.72–0.99), p = 0.04]. Overall 30-day survival with good neurologic outcome was significantly different in the three tertiles [T1: 0.1–0.8; T2: 0.9–1.8 and T3: 1.82–7.8, log-rank p = 0.007].Conclusion The post-ROSC peripheral perfusion index was found to be an independent predictor of 30-day mortality or poor neurologic outcome. It could help prognostication in OHCA patients.
Article
Background Perfusion index (PI) derived from pulse oximeter shows the ratio of the pulsatile blood flow to the nonpulsatile blood flow or static blood in peripheral tissue. Objectives The aim of this study was to investigate the relationship between PI and blood transfusion necessity in 24 h and stage of hemorrhagic shock, as well as the utility of PI according to laboratory and clinical parameters, and determining the major risk of hemorrhage. Methods PI was measured with a pulse oximeter in 338 patients (235 males, average age 41.8 ± 17.94 years). Laboratory parameters (hemoglobin, hematocrit, lactate, base deficits, pH) and clinical parameters (pulse rate, respiratory rate, SpO2, systolic blood pressure [SBP] and diastolic blood pressure [DBP]), shock index (SI) and revised trauma score (RTS) were recorded. Univariate analysis was used to determine major risk for bleeding, and the receiver operating characteristic curves were performed to compare parameters. Results PI was < 1 in 39 (11.5%) patients. Positive correlation between PI and hemoglobin (p < 0.001; r: 0.320), hematocrit (p < 0.001; r: 0.294), base deficit (p < 0.001; r: 0.315), pH (p < 0.05; r: 0.235), SBP (p < 0.001; r: 0.146), DBP (p < 0.001; r: 0.259), SpO2 (p < 0.001; r: 0.197), RTS (p < 0.001; r: 0.344), and negative correlation with lactate (p < 0.05; r: −0.117), pulse (p < 0.001; r: −0.326), respiratory rate (p < 0.001; r: −0.231), and SI (p < 0.001; r: −0.257) were detected. A difference was detected between class 1 and 2, and class 1 and 3 (both p < 0.05) in hemorrhagic shock. Thirty-one with PI < 1 had blood transfusion within 24 h (p < 0.001; odds ratio 111.98, sensitivity 75.6%, specificity 97.3, positive predictive value 79.5%, negative predictive value 96.7%). The main risk factors of the need for blood transfusions were PI, pulse rate, and SpO2. PI was more significant than lactate, base deficit, RTS, and SI measurements. Conclusion PI might be beneficial in the detection and exclusion of critical patients and blood transfusion needs in the emergency department. PI can be used with vital signs and shock parameters in the early diagnosis of hemorrhage.
Article
Aim: This study aimed to examine the prognostic significance of the perfusion index (PI) in mechanically ventilated patients. Methods: Study included sixty patients who had the risk factors for the development of acute respiratory distress syndrome and received mechanical ventilator (MV) support in intensive care unit (ICU) unit between January 2017/January 2018. The demographic characteristics, vital signs, blood gas parameters, lactate levels, prognostic scores, and use of inotropic drugs were recorded. Arterial blood gas and PI measurements at the frontal region were performed at the time of and 12th and 24th hours of admission to the ICU. The patients were followed up for 60 days, and the outcome was recorded. Results: Twelve patients (20%) died during the first 7 days, and 27 patients (45%) died within 60 days of the admission. Multivariate analyses to determine potential predictors of 7 and 30-day mortality showed that only 24th-hour lactate level was independent predictor of 60-day mortality, and the PI at 24th was the sole independent predictor of 7-day mortality. Conclusion: The PI did not predict 60-day mortality in MV patients who had risk factors for the development of Acute Respiratory Distress Syndrome (ARDS). However, the PI at 24th may be a significant predictor of 7-day mortality.