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Effect of Hemiparetic Stroke on Pulse Oximetry Readings
on the Affected Side
Christine Roffe, MD; Sheila Sills, RGN; Kathryn Wilde, PhD; Peter Crome, MD, PhD
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Background and Purpose—Hypoxia is common after stroke, and monitoring by pulse oximetry is suggested in the acute
phase. Physical changes on the affected side or intravenous infusions may affect oximeter readings. This study was
designed to test whether pulse oximetry recordings are the same on the affected and nonaffected sides in stroke patients.
Methods—Oxygen saturation (SpO2) and heart rate (HR) were assessed simultaneously in the left and right hands in
patients with hemiparetic stroke over a 3-hour period with 2 Minolta Pulsox-3i oximeters attached to the index fingers.
Results—Fifteen patients (53% men; 67% left hemiparesis; mean age, 73 years [SD, 7.5 years]) were recruited. HR and
SpO2 (12 measurements per minute) were monitored. The maximum difference between simultaneous left and right arm
readings was 2% SpO2. HR fluctuated more, but no affected/nonaffected side pattern was seen. Means for each patient
of HR and SpO2 for the affected and nonaffected sides were compared by t tests. Mean SpO2 was 96% (SD, 1%) on both
sides. Mean HR was 81 bpm (SD, 11 bpm) on the affected side and 80 bpm (SD, 10 bpm) on the nonaffected side. There
was no significant difference between the 2 sides for either parameter (n⫽15; P⫽0.86 for SpO2 and P⫽0.91 for HR).
Conclusions—Oximeters can be attached to either the affected or nonaffected side in hemiparetic stroke. (Stroke. 2001;
32:1808-1810.)
Key Words: anoxia 䡲 hemiplegia 䡲 hypoxia 䡲 oxygen 䡲 stroke management
P
atients who have suffered a stroke are prone to respiratory problems for a number of different reasons. These
include alterations in the central regulation of respiration,1
sleep apnea,2,3 weakness of the respiratory muscles on the
hemiplegic side,4 – 6 aspiration,7 chest infections,8,9 left ventricular failure,8 and pulmonary emboli.8,9 While routine
oxygen supplementation cannot be recommended by current
evidence,10 treatment guidelines for acute stroke unanimously
support treatment of hypoxia.11,12 The European Ad Hoc
Consensus Group suggested that all patients with acute stroke
should have their oxygen saturation monitored continuously
or at frequent intervals.12 Pulse oximetry allows oxygenation
to be monitored continuously and noninvasively.13
Motion artifact can be a major problem in the interpretation
of oximeter readings.13–17 In patients with stroke, such problems may be reduced by placing the oximeter probe on the
affected side. However, there is no published evidence
confirming that readings on the affected and nonaffected
sides are comparable. Stroke-related edema, changes in vasomotor tone, and skin temperature may potentially alter
oximeter readings on the affected side. Many patients with a
stroke will have an intravenous drip in situ within the first few
days, and this may also affect readings.13–17
This study was designed to test whether oxygenation, as
assessed by pulse oximetry, is the same in the affected and
nonaffected sides in hemiparetic stroke patients.
Subjects and Methods
Adults with acute hemiparetic stroke were recruited over a period of
19 weeks. The researcher interviewed the patients within 72 hours of
their admission to hospital. Patients who were moribund, those who
refused consent, those with mild hemiparesis (power ⬎2/5),18 those
with poorly perfused limbs or very thick nails, and those in whom
finger probes could not be placed or who were too restless to keep
the probes in situ were excluded. Intravenous infusions were not a
contraindication as long as the flow rate was ⬍1 L over 8 hours.
Patients were either sitting or lying down. Hands were inspected to
ensure that the fingers were warm and well perfused. Nail varnish
was removed and long fingernails were clipped, when necessary.
Excessive ambient lighting was turned off or reduced by screens.
Pulse oximeters (Pulsox-3i, Minolta, and Oximeter DownLoad
software for Windows, Stowood Scientific Instruments, Beckley)
were attached to both wrists and secured with tape. The sensory
probes were fitted to the index fingers. Measurements were performed for 3 hours, between meals, with the patient resting. The
patient was observed by the researcher to detect and record arm
movements, which might result in recording artifacts. No blood
pressure measurements were taken during the time of the study.
Values for oxygenation (SpO2) were obtained by performing a
moving average for the last 5 seconds, updated every second. Those
for heart rate (HR) were obtained by performing a moving average
for the last 8 bpm, updated every second. Descriptive data analysis
was performed on Microsoft Excel for Office 2000. Statistical tests
were conducted in SPSS version 10 for Windows.
Results
During the recruitment period, 225 patients with acute stroke
were seen by the research nurse. Of those, 132 were excluded
Received February 8, 2001; final revision received April 12, 2001; accepted April 12, 2001.
From the Department of Geriatric Medicine, Keele University, Staffordshire, UK.
Correspondence to Dr C. Roffe, Springfield Unit, City General Hospital, Stoke-on-Trent, ST4 6QK, UK. E-mail [email protected]
© 2001 American Heart Association, Inc.
Stroke is available at http://www.strokeaha.org
1808
Roffe et al
Pulse Oximetry in Stroke Patients
1809
Oximetry Results From the Left and Right Hands of 15 Acute Stroke Patients
HR, bpm
SpO2, %
Left
Right
Left
Right
Affected
Side
1
71 (14)
70 (7)
96 (1)
96 (1)
Right
No
2
88 (3)
88 (3)
96 (1)
96 (1)
Left
No
3
95 (10)
99 (10)
96 (2)
96 (1)
Right
Right
4
80 (10)
82 (7)
94 (2)
95 (1)
Left
Right
5
89 (4)
89 (3)
96 (1)
95 (1)
Right
No
6
71 (4)
71 (5)
95 (1)
95 (1)
Left
Left
7
75 (6)
75 (6)
93 (1)
93 (1)
Right
No
8
87 (11)
88 (11)
94 (1)
94 (2)
Left
Right
9
79 (7)
80 (7)
97 (1)
97 (1)
Right
Right
10
56 (4)
56 (4)
97 (1)
96 (1)
Left
Left
11
89 (9)
87 (9)
98 (1)
98 (1)
Left
No
12
78 (3)
77 (2)
97 (1)
96 (1)
Left
No
13
91 (6)
90 (5)
95 (1)
95 (1)
Left
Right
14
76 (8)
76 (7)
95 (1)
95 (1)
Left
No
15
78 (8)
78 (8)
96 (1)
96 (1)
Left
No
Patient
Intravenous Drip
In Situ
Downloaded from http://stroke.ahajournals.org/ by guest on June 16, 2017
Values are mean (SD).
because ⬎72 hours had passed since their stroke, 16 were
excluded because of reduced consciousness, none were excluded because of poor peripheral perfusion, 4 were excluded
because of confusion or restlessness, 15 were on oxygen
treatment, and 43 had no limb weakness. Fifteen patients
matched the inclusion criteria and were recruited to the study.
None of the participants dropped out during the study. All
oximetry traces were interpretable and could be used for the
final analysis.
Fifteen patients (8 men [53%], 7 women [47%]; 10 left
hemiparesis [67%], 5 right hemiparesis [33%]; mean age, 73
years [SD, 7.5 years]; median Glasgow Coma Scale score, 15
[range, 6 to 15]) were included in the trial. Seven subjects
(47%) had total anterior circulation syndrome, 4 (27%) had a
partial anterior circulation syndrome, and 4 (27%) had a
lacunar syndrome.19 A CT of the head showed cerebral
infarcts in 11 of the subjects (8 cortical, all involving the
parietal cortex; 3 lacunar) and a cerebral atrophy in 1
(clinically a lacunar stroke). Three patients died before a CT
scan could be performed; clinically all 3 had total anterior
circulation syndromes. Seven patients (47%) had an intravenous infusion in situ, 4 on the affected side and 3 on the
nonaffected side.
The raw oximetry results (12 measurements per minute)
for HR and SpO2 for the left and right hands were first
examined for each patient individually. There was never
⬎2% difference in the SpO2 readings obtained simultaneously
on the left and right sides. This equates to no difference since
the constraints of the precision and accuracy of the equipment
were ⫾2% for SpO2. HR is more sensitive to artifacts and
showed greater variation in the left and right readings. There
was, however, no pattern of either the left or right or
affected/nonaffected side being consistently higher or lower.
The mean and SD values of HR and SpO2 for the left and
right sides over the 3-hour period for each patient are shown
in the Table. The mean SpO2 was 96% (SD, 1%) on the
affected side and 96% (SD, 1%) on the nonaffected side. The
mean HR was 81 bpm (SD, 11 bpm) on the affected side and
80 bpm (SD, 10 bpm) on the nonaffected side. The mean
results of HR and SpO2 over the 3-hour period on the affected
and nonaffected sides of all patients were compared by
Student’s t tests. There was no significant difference between
the 2 sides for either parameter (n⫽15; P⫽0.86 for SpO2 and
P⫽0.91 for HR).
In the 7 patients who had an intravenous drip in situ, there
was no significant difference in oximetry readings between
the drip arm and the nondrip arm (P⫽0.44 for SpO2 and
P⫽0.96 for HR [Student’s t test]).
Discussion
In hemiparetic stroke patients, the results of pulse oximetry
are not affected by the side to which the probe is attached.
The pulse oximetry recordings are not affected by the
presence of an intravenous infusion running at a standard rate.
Pulse oximeters can therefore be attached to either the
affected or nonaffected side. Since there is likely to be less
movement artifact on the affected side, placement of the
oximetry probe on the affected side is recommended.
Acknowledgements
This study was supported by a grant from the North Staffordshire
Medical Institute. We would like to thank the North Staffordshire
Medical Institute for their generous support of the study. We would
also like to acknowledge all study participants, without whose
personal input this study would not have been completed.
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Effect of Hemiparetic Stroke on Pulse Oximetry Readings on the Affected Side
Christine Roffe, Sheila Sills, Kathryn Wilde and Peter Crome
Downloaded from http://stroke.ahajournals.org/ by guest on June 16, 2017
Stroke. 2001;32:1808-1810
doi: 10.1161/01.STR.32.8.1808
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Copyright © 2001 American Heart Association, Inc. All rights reserved.
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