BACKGROUND
Asthma could result in abnormalities in gas exchange that
lead to hypoxemia from when acute exacerbation occurs. A decrease in SpO2
suggests hypoxemia. Arterial
blood gas analyzer machine which is used in the assessment of blood gases is
the gold standard in quantification of carbon dioxide and oxygen concentration
in the blood1.
Oxygen saturation measurement
using arterial blood gas analysis is reliable and accurate but it would require
sending blood samples to a medical laboratory with facility to carry out the
investigation.1 However, the arterial blood gas analysis facilities are not
available in most hospitals in Nigeria and the procedure is painful and could
result in local hematoma, infection and occlusion or embolization.2 Therefore
the need for simple device for objective quantification of oxygen concentration
is paramount in the management of acute exacerbations of asthma.
Pulse oximeter not
invasive, simple, user friendly, portable and affordable device used in the
measurement of blood oxygen concentration. The pulse oximeter
calculates the quantity of light of two wavelengths absorbed from a source in
the probe when put onto a finger or toe.3It is very useful in
assessing the need for oxygen administration and monitoring of asthmatic
patients on emergency admission
for acute exacerbations. So oxygen
saturation could be assessed using pulse oximeters device
thus reducing the need for arterial blood gas analysis. Although some patients in acute asthmatic
exacerbation could be at the risk for respiratory failure, hypercapnea
or metabolic acidosis, assessment of oxygen levels could suffice and may not
always require analysis blood gas.4,5,6
Pulse oximeters
values could be 2% or 4% lower or higher than the person’s actual oxygen
saturation levels. A number of factors can reduce the accuracy and reliability
of the pulse oximetry reading and these include nail
varnish or nail polish, some dyes, shivering, shaking, or other bodily motions,
skin temperature, skin thickness, tobacco smokes and skin pigmentation.6
However, British Thoracic Society guidance on
oxygenation7,8 states that pulse oximetry is the “fifth vital sign” together with
temperature, pulse, blood pressure and respiratory rate so it should be carried
out for all patients presenting with acute breathlessness in primary care.
In acute asthma, oxygen saturation
is used as part of a comprehensive assessment to guide selection of appropriate
treatment. In the management of acute severe asthma in adults, oxygen
saturation is key in differentiating moderate asthma
from acute severe asthma and life threatening asthma.9 Pulse oximetry is commonly used in acute severe asthma or other
asthma exacerbations in the emergency room.10
Objective and reliable diagnosis of bronchial
asthma is usually done by carrying out spirometry.11,12
The parameters assessed include Forced
Expiratory Volume in One Second (FEV1), Forced Vital Capacity (FVC)
and FEV1/FVC ratio. FEV1/FVC ratio is a reflection of the
degree of bronchial obstruction. FEV1 correlates well with quality
of life measures.13The measured or predicted value of FEV1
is a reflection of the severity of the asthma exacerbation and the level of
asthma control.14
However,
in our setting asthma has been misdiagnosed by some practitioners by relying
only on clinical features without objective assessment and there is paucity of
knowledge of the relationship between oxygen saturation and spirometric
parameters among asthmatics.
Therefore, this study seeks to know the
proportion of suspected asthmatics that were confirmed by objective spirometric assessment to determine if clinical diagnosis
can be used as an alternative in making diagnosis of bronchial asthma in
settings where spirometry services are not
available. The study also seeks to explore
the relationship between SpO2 and spirometer parameters among these patients.
METHODOLOGY
Study design,
location and population.
This
was an observational cross-sectional descriptive study carried out among
suspected asthmatics referred to the
Chest Clinic of the NDUTH.
NDUTH is located in Okolobiri,
a suburb community of Yenagoa, the capital city of Bayelsa State, South-South,
Nigeria. The NDUTH sub-serves residents of Bayelsa
state and neighboring states of Delta and Rivers States.
A total of 150 suspected Bronchial Asthma
asthmatics referred to the Chest
Clinic of the NDUTH between January 2017 and December 2020 were recruited for
the study.
Inclusion criteria include all adult
suspected asthmatics who gave consent and were fit to carry out spirometry, and exclusion criteria include suspected
asthmatics not willing to participant in the study, acute severe and life
threatening asthma.
Methods
The
research was done in the cardio-respiratory laboratory of the department of
internal medicine, NDUTH. GINA criteria was used to make diagnosis of asthma so
all participants underwent spirometry in the
cardio-respiratory laboratory of the department of internal medicine, NDUTH
following medical history taking, general and respiratory system examinations.
Spirometry was performed
according to the American Thoracic Society(ATS)/European Respiratory
Society(ERS) guidelines.16 Before the procedure, participants were
instructed to abstain from vigorous exertion, such as running and swimming for
at least one hour, and eating of large meals for at least two hours.16 Their heights were
measured to the nearest centimeter using a tape measure on a flat surface,
while their weights were measured to the nearest 0.1 kilogram using a portable
weight machine after zero calibration check. Body mass index was calculated
accordingly.17 Participants
stood comfortably while they inspired fully, occluded their nostrils with one
hand, placed the mouthpiece of the spirometer in their mouth, and sealed their
lips tightly around the mouthpiece to prevent air leaks.16
These maneuver were
done both before and after administration of 400 micrograms of inhaled short
acting B-agonist (salbutamol). Administration of inhaled salbutamol was done by
first vigorously shaking the metered-dose salbutamol inhaler, followed by
removing the cap from the mouthpiece of the inhaler. Then, the inhaler was
primed by releasing a puff into the atmosphere before it was inserted through
its mouthpiece to a receiver end of a spacer device. Participants were told to
breathe in and out slowly, and insert the mouthpiece of the spacer device into
their mouth and breathe in through their mouth while two (2) puffs of inhaled
salbutamol were released by depressing the canister of the metered-dose
inhaler.16
Spirograms that met the ATS/ERS
criteria16 for acceptability were used. The following measurements were obtained from spirometry
(FEV1) Forced Expiratory Volume in one second (FEV1), defined as the
maximal volume of air forcefully exhaled in the first second from total lung capacity, Forced Vital Capacity, defined as the maximal
volume of air forcefully exhaled following maximal inspiration (FVC) and Ratio
of FEV1 to FVC (FEV1/FVC ).18
A portable pulse oximeter
(Gurin GO -410 Finger Pulse Oximeter)
was used to measure oxygen saturation of the study participants with a Gurin
Finger Pulse Oximeter, the right thumb of each
participant was inserted into the groove after parting the lips of the
instrument. The “power” button was then pressed down and the machine came on.
Reading of the oxygen saturation began automatically, and after a few seconds,
the values for both oxygen saturation and pulse rate appeared on the
mini-screen of the instrument and the values were recorded. Participants found
to have oxygen saturation less than 92% where admitted to the emergency for
further management.
Data analysis
Data
was documented and analyzed using the Statistical Package for Social Sciences
(SPSS) version 22.19 Descriptive statistics was performed for
socio-demographic characteristics while Pearson’s correlation was used where applicable. The results were presented as percentages and
tables as appropriate. A p-value of less
than or equal to 0.05 was considered statistically significant for all relevant
tests
Ethical consideration
Ethical
approval for the study was obtained from the Research and Ethics Committee
(REC) of the NDUTH, Okolobiri.
RESULTS
The
study participants were more in the age range of 18-44 years,
males had more participants than females. Fifty seven constituting 38.2% of the
study subjects had FEV1 /FVC Ratio% predicted of <0.75,
59 (39.2%) had bronchodilator reversibility of >12% and obstructive spirometric pattern, 139 (93.92%) had oxygen saturation (SPO2)
of >92% while 9 (6.08%) had oxygen saturation (SPO2) of
<92% as shown on table 1 below.
DISCUSSION
In
spite of it limitations3 monitoring of oxygen saturation using pulse oximeter is very useful in the management of acute disease
conditions including acute bronchial asthma in the emergency rooms, anesthesia
departments and critical care management of patients.6 The level of oxygen
saturations is a useful guide in the administration of oxygen to patients
especially in setting where arterial blood gas monitoring of patients is not
available.
The gold standard in making diagnosis of
bronchial asthma is assessment of Forced Expiratory Volume in one second
(FEV1), Forced Vital Capacity (FVC) and FEV1/FVC ratio by carrying out
spirometry.15 Peak Expiratory Flow Rate (PEFR) using Peak Expiratory Flow
Meters is useful in the emergency room management of bronchial asthma and
monitoring of asthmatic patients. 15
Some asthmatics are poor perceivers20 so may
not have severe clinical manifestations necessitating admission into the
emergency room but these patients could have poor spirometric
indices and possible low levels of oxygen saturation. Without thorough
evaluation of the spirometric indices and oxygen
saturation status of these patients, misdiagnosis and improper assessment could
occur.
Relying only on patients symptoms to make
diagnosis of bronchial asthma without carrying out spirometry
could have pitfalls including misdiagnosis of bronchial asthma.
This index study was carried out to assess
the levels of oxygen saturation using pulse oximeter,
and spirometric indices and the relationship between
them among suspected bronchial asthmatics referred to Chest Clinic of the
NDUTH.
In this study, 57 participants constituting
38.2% of the study subjects had FEV1 /FVC ratio % predicted of <0.75, and 59
(39.2%) had bronchodilator reversibility of >12% thereby fulfilling the
criteria for the objective diagnosis of bronchial asthma. This was higher
compared to a hospital based study carried out among patients who presented in
the emergency department of a hospital in Ethiopia which showed a lower
percentage (29.6%).21 This difference could be attributed to the fact that our
study was carried out among suspected asthmatics as opposed to this study which
was done among patients that presented at an emergency department.
One striking finding of this study was that
the same number of participants, 59 (39.3%) had obstructive spirometric
pattern and bronchodilator reversibility of equal to or greater than 12%.
There was a positive correlation and
significant relationship between most of the spirometric
parameters and oxygen saturation as shown on table 2. This finding was similar
to the works done by Usha et al.,22
who carried out an assessment of PEFR and oxygen saturation among the residents
in a mine tailing community.
However, the result of this index study was
in contrast to the finding of a research carried out by Renee et al23 among adults with cerebral palsy where he found no
statistically significant relationship between lung vital capacity and oxygen
saturation, and between chest expansion and oxygen saturation. In this study
oxygen saturation was within the normal range in all persons, in the face of
decreased values of the measured lung parameters. The major difference between these two
studies was the difference in the study population. This study was done among
adult cerebral palsy patients while our study was done among suspected
asthmatics.
Monitoring of oxygen saturation is
recommended only for patients with acute severe disease conditions, but routine
pulse oximetry among suspected asthma can identify
those who might benefit from oxygen therapy.
The result of our study may have clinical
relevance because nine patients that had spirometric
evidence of bronchial asthma that did not meet clinical criteria for acute
severe asthma were found to have low (<92%) SPO2 and were admitted into the
emergency room for further management based on the low level of oxygen
saturation. This finding reiterates the need to have proper evaluation of all
patients with respiratory symptoms by carrying out pulse oximetry.
Therefore, the clinical implication of the
finding of this study is the need to carry out routine assessment of oxygen
saturation among suspected asthmatics even in the outpatient setting.
CONCLUSIONS
Only
a proportion of the suspected asthmatics were confirmed by spirometry
and there was a statistically significant correlation between oxygen saturation
and FEV1, FVC and FEV1 /FVC among the participants.
RECOMMENDATION
All
suspected asthmatics should undergo pulmonary function tests including pulse oximetry in order to have an objective diagnosis and proper
evaluation of the patients.
LIMITATION
Arterial
oxygen measurement was not done in this study, that would have added more value
to the findings as it would have enabled us to use it as a standard to assess
how reliable and accurate the pulse oximeter measured
SPO2 values were.
ACKNOWLEDGEMENT
The authors wish to express our profound
gratitude to all staff of the Cardiorespiratory unit,
Department of Internal Medicine, Niger Delta University Teaching Hospital, Bayelsa State for their meaningful contributions.
REFERENCES
1.
Carruthers 1995 Carruthers DM, Harrison
BDW. Arterial blood gas analysis or oxygen saturation in the assessment of
acute asthma? Thorax 1995; 50(2):186-8.
2.
Kelly AM, McAlpine
R, Kyle E. How accurate are pulse oximeters in
patients with acute exacerbations of chronic obstructive airways disease? Respir Med 2001; 95:336-40.)
3.
Steve Holmes, Pulse oximetry:
not an infallible test – use clinical judgment. Primary Care Respiratory Update
issue 22 July 2021; 29-31.
4.
El-Sberbihy
RR, El-Ezz AA, El-raouf YM,
Taha AM. Pulse oximetry in
comparison to arterial blood oxygen saturation in children with bronchial
asthma coming to the emergency room. Tanta Med J 2018;46:93-8
5.
Collins, J.A, Rudenski, A., Gibson, J., Howard, L., O’Driscoll,
R. Relating Oxygen Partial Pressure, Saturation and Content: The Haemoglobin–Oxygen Dissociation Curve. Breathe. 11(3),
2015, 194-201
6.
Mustafa Mahmood
EidThe reliability of Oxygen saturation compared with
arterial blood gas analysis in the assessment of respiratory failure in acute
asthma. Int J Crit Care Emerg Med 2020, 6: 101vol 6 issue 2.
7.
Sotirios Fouzas Kostas N Priftis Michael B Anthracopoulos. Pulse Oximetry in Pediatric Practice PEDIATRICS 2011; 128(4):740-52
8.
British Thoracic Society Standards of Care Committee. BTS
Guidelines for the Management of Community Acquired Pneumonia in Adults. Thorax
2001; 56 (Suppl 4):iv1–64. https://doi.org/10.1136/thorax.56.suppl-4.iv1
14.
9.
Lim WS, Baudouin SV, George RC, et al. BTS guidelines for the management of
community acquired pneumonia in adults: update 2009. Thorax 2009; 64 (Suppl 3):iii1–55. https://doi.org/10.1136/thx.2009.121-434.
10. BTS/SIGN British Guideline on the Management of Chronic
Asthma; 2014.
11.
Renaud Louis, Imran Satia, Inigo Ojanguren, Florence Schleich,
Matteo Bonini, et.al.
European Respiratory Society Guidelines
for the Diagnosis of Asthma in Adult European
Respiratory Journal 2022; DOI: 10.1183/13993003.01585-2021
12.
Brian L. Graham, Irene Steenbruggen,
Martin R. Miller, Igor Z. Barjaktarevic, et.al; on
behalf of the American Thoracic Society and the European Respiratory Society. American
Thoracic Society document: Standardization of Spirometry
2019 Update. An Official American Thoracic Society and European Respiratory
Society Technical Statement.
13.
Brice Touilloux, Alexandra Lenoir, Jean-William Fitting, Peter Vollenweider, Marie-Pierre F. Strippoli, Martin Preisig, Laurent P. Nicod . The association of FVC with quality of life – The Pneumo
Laus|PsyCoLaus study. European Respiratory
Journal 2020 56: 1662; DOI: 10.1183/13993003.congress-2020.166.
14.
Ribeiro de Andrade MC, Duarte
P. Camargos. Correlation between pulse oximetry and peak expiratory flow in acute asthma. Cardoiovascular, Respiratory and Sports Medicine. Braz J Med Biol Res20074; 40 (4).
https://doi.org/10.1590/501000-879x200700040006.
15. Global Initiative for Asthma (GINA)
Global strategy for Asthma Management and Prevention 2021. Available from www.ginasthma.org
16. Brian LG, Irene S, Miller MR, Igor ZB, Brendan GC, Graham
LH, et al. Standardization of spirometry 2019 update:
An official American Thoracic Society and European Respiratory Society
Technical Statement. American Journal
of Respiratory and Critical Care Medicine, 2019; 200:8.
17. Wang Y. Chapter 2: “Use of percentiles and z-scores in
Anthropometry”. Handbook of Anthropometry. New York: Springer, 2012; p. 29.
18. Moore VC. Spirometry: step by
step. Breathe, 2012; 8: 232-240.
19. IBM SPSS Data Collection Divestiture, 2016.
20. Magadle R,
Berar-Yanay N, Weiner P. The risk of hospitalization
and near-fatal asthma in relation to the perception of dyspnea. Chest. 2002;
121: 329-333.
21. Sisay
Shine, Sindew Muhamud, Alebachew Demelash . Prevalence and associated asthma among adult patients in Derre Berhan Referral Hospuital, Ethiopia 2018: a cross-sectional study. BMC
Research Notes 12 Article number: 608 (2019)
22.
Usha G Shenoy and Karthiyanee Kutty. Peak Expiratory Flow Rate, Blood Oxygen
Saturation, and Pulse Rate among a Mine Tailing Community. Indian J
Community Med. 2018 Oct-Dec; 43(4): 294–297. doi: 10.4103/ijcm. IJCM 18518 PMCID:
PMC6319286.
23.
Renée Lampe, Tobias Blumenstein, Varvara Turova, and Ana Alves-Pinto. Lung vital capacity and oxygen saturation in adults
with cerebral palsy. Patient Prefer Adherence. 2014; 8: 1691–1697. doi: 10.2147/PPA.S72575 PMCID: PMC4267512 , PMID: 25525345.
