Interference of nail polish on the peripheral oxygen saturation in patients with lung problems during exercise 1

Aim: To assess the interference of nail polish on the reading of peripheral oxygen saturation in patients with chronic obstructive pulmonary disease on the step exercise. Methods: In this study, there was the inclusion of patients with chronic obstructive pulmonary disease, current non-smokers, of both sexes. Four different colours of nail polish were used in the present study (base, light pink, red and brown), randomly distributed among the fingers of the right hand, with the corresponding fingers on the opposite hand being controls. Saturation was measured at rest, with and without the polish, and also during the 4th, 5th and 6th minutes of the exercise programme. Results: The experimental universe included 42 patients with ages of 62.9±8.7 years. In the exercise considered, the red colour reduced it in the fourth minute of the exercise (p=0.047). In contrast, the brown colour reduced saturation at rest and also during the course of exercise (p=0.01). Conclusion: In patients with chronic obstructive pulmonary disease, the red and brown colours interfered with the reading of the peripheral oxygen saturation during exercise. This study is registered at the Brazilian Register of Clinical Trials (Registro Brasileiro de Ensaios Clínicos) under No. RBR-9vc722.


Introduction
Pulse oximetry is a significant advance in noninvasive monitoring, as it not only has low cost, but is also quick and does not need any specialised personnel.
It is widely in hospitalisation units, outpatient units, laboratories of pulmonary function, ready service units, Intensive Care therapy, home care and surgical theatres, seeking the early detection of hypoxaemia in different situations (1)(2)(3) .
Several factors can limit the accuracy of pulse oximetry readings, including the following: states of shock with poor tissue perfusion; oxygen saturation values below 70%; skin pigmentation; certain lighting systems such as surgical lamps, fluorescent lighting and fibroscopic instruments; movement of the sensor; sensor not compatible with the equipment and lack of calibration; high levels of carboxyhaemoglobin, metahaemoglobin and bilirubin (4)(5)(6)(7)(8)(9) .The effect of using nail polish on the SpO 2 readings is contradictory, as some studies have reported significant reductions (10)(11)(12) , while others have not observed any changes or have seen changes related to some specific colours (13)(14)(15)(16)(17)(18)(19)(20) .Clinical, surgical and emergency scenarios have the routine of removing nail polish.This removal means a need to have the necessary apparatus, as also to guard and/or store the gadgets and also have the consent of Shimoya-Bittencourt W, Pereira CAC, Diccini S, Bettencourt ARC.
the patient to remove the nail polish.Thus, time and resources may be saved, and also there is avoidance of a confrontation with patients who refuse to remove their polish.
In addition, in clinical practice it has been observed that the removal of the nail polish is not always due to emergency or urgency situations of the transfer of the patient from the outpatient department to the surgical centre or outpatient surgeries, to where the patient is often admitted hours before the surgical procedure (15,18) .
Oxygen saturation is also commonly used during exercise tests in patients with several different conditions to monitor the occurrence of hypoxaemia caused by exercise.
Most studies carried out have appraised the effect of nail polish on the pulse oximetry among healthy individuals at rest.In these cases, the small variations as described in SPO2 have no clinical significance, which could not be the case among people with pulmonary diseases when subjected to exercise.
The aim of the present study was that of appraising the interference of the colour of the nail polish on the reading of peripheral oxygen saturation (SpO 2 ) among patients with chronic pulmonary obstructive disease (CPOD) when taking exercise.The participants in the study were adult volunteers with stable DPOC (without any signs of respiratory discomfort and without exacerbation periods in the six weeks running up to their inclusion in the study), of both genders, non-smokers or former smokers.The seriousness of the obstruction of the DPOC was based on the criteria as proposed by the GOLD consensus (21) .

Methods
All volunteers were duly informed about the procedures and the aims of this study, and also signed a Declaration of Free and Clarified Consent before the survey got under way.
The following classes of patients were excluded from the study: patients with heart problems (cardiac insufficiency, arrhythmia); patients with osteomuscular problems, sclerodermia and omicomicosis; patients with haemoglobin values (Hb) either <13.5 or >17,5 g/dL for men or Hb <12 or >16.5g/dLfor women; haematocrit (Htc) <40.5 or >52.0% for men or <36 or >48% for women; people with total bilirubin of < 0.4 or >1.2mg/ dL and direct and indirect bilirubin of more than 0.4mg/ dL; systematic arterial hypertension; altered peripheral perfusion with capillary filling of >3 seconds; carbon monoxide measure (CO) ≥10 ppm checked with the use of the monoximeter (MicroCo meter made by Micro Medical Ltd), according to the study protocol proposed by Santos et al (2001) (22) .
Measures of SpO 2 were taken on the fingers of both hands, at the top of the nail bed, before the collection of the data, to make sure of the homeogeneity of the measurements and also to check if there has been any difference in the SpO 2 measure between the two hands.
Values of SpO 2 with a difference of ±2% were accepted.
Four different colours of nail polish were used: base, red, light pink, and brown, all being of the Risqué ® brand.The colours chosen are the most commonly used in our environment.The application of the nail polish on the right hand was made starting on the little finger, going towards the thumb.The distribution of the colours of the nail polish was random for each patient, but always following the sequence of application.
Each finger of the right hand which was subjected to the procedure had the corresponding finger on the other hand as a control.After the application of the second coat of nail polish, a spray was then used to ensure complete drying.
For the measurement of SpO 2 two portable pulse oximeters of the Nonin brand were used.The equipment was tested in advance, before the measurements of SpO 2 , and variations of ±2% in the SpO 2 readings were accepted, between the two pulse oximeters (2) .During the verification of measurements, the sensor remained on the finger without any variation in saturation value for 15 seconds, to reduce the margin of error before the SpO 2 was registered.The time was controlled using a digital chronometer (sport timer).
After the patients were made aware of the carrying out of the exercise, these were subjected to prior training to make sure they would be able to carry out the activity.The exercise used was the step exercise (23) .
The patients had to go up and down a standardised step with a height of 20 cm, both for men and for women, according to the intensity and also the rhythm of the Rev. Latino-Am.Enfermagem 2012 Nov.-Dec.;20(6):1169-75.
patient, for a period of six minutes.After every minute, they were encourageds to complete the exercise.
During the exercise, the patients used an affixing and immobilising device on both hands and forearms, and were also advised to avoid excess movements with their wrists and their fingers, in order to reduce as much as possible the movement of trhe sensor, to avoid possible changes to SpO 2 .
The SpO 2 measurements before the exercise were made both before and after the application of the nail polish, with the patient being seated confortably and with hands supported.The first measure recorded was at zero time (T 0 r), which is prior to the application of the nail polish, and the second at time one (T 1 rep), after the complete drying of the nail polish, totalling two measurements.
During exercise, the measurements were recorded at 4 (T 4 ex), 5 (T 5 ex) and 6 (T 6 ex) minutes after the start of the exercise.
The exercise would be stopped if the patients showed SpO 2 <80%, dizziness or if they asked to stop.
In case of any interruption, the test was repeated after the FC and also the SpO 2 returned to the base levels.For a comparison between different appraisal moments, there was the use of a construction of contrasts that allowed such an appraisal within the very model of ANOVA-MR, to make sure that the type I error for all comparisons was set at a fixed value of 5%.All statistical tests carried out were two-tailed.A value less than 0.05 was considered significant.

Results
Initially, 51 patients with DPOC were selected.
Out of this new reduced universe, nine patients were excluded: two for having low haemoglobin levels and haematocrit; four for levels of SpO 2 desaturation <80% during exercise; one who interrupted the test due to leg pain; one who interrupted the test because of dyspnea; and one who was not able to perform the CO measurement test.This means that a total of 42 patients were finally included in the study.The characteristics of the sample are shown in Table 1.
The average age of the subjects was 63 years, and there was a prevalence of males and non-whites.
The seriousness of the disease was homogeneous in distribution and the time as a smoker ranged from 18 to 59 years.We also see normal values for the measurements of exhaled carbon monoxide, haemoglobin, haematocrit and bilirubin.No difference was found between the saturation measurements for the right hand and for the left hand at rest, before the nail polish was applied (Table 2).

Characteristics
www.eerp.usp.br/rlaeShimoya-Bittencourt W, Pereira CAC, Diccini S, Bettencourt ARC. during the exercise periods.When the data of the right hand are compared with the respective controls over time, there was a statistically significant difference for the red and brown colours (p<0.001), for which smaller values were observed.However, the significant fall in the red and brown colours was similar to that observed in the respective controls in the same measurement periods.This fact suggests that the fall in saturation that occurred during exercise was made stronger in the case of these colours.To establish which colours differed in each of the time points that showed a significant difference, there was an analysis made based on multiple comparisons.In Table 4 we can see that, in the comparison between the base and brown colours at the time moment T 1 rep, there was a marginally significant difference.The average saturation of the pink colour was statistically greater than that shown by brown at the time moments T1rep, T4ex e T6ex (p=0.022,p=0.003 and p=0.050, respectively), and the average saturation of red was statistically greater than that shown for brown, in the three instances of appraisal (p<0.05).Thus, we can conclude that the colour brown presented an average saturation which was lelss than those observed for the other colours, at the moments T1rep, T4ex and T6ex.

Discussion
Nail polish has been described in specialised literature as one of the factors that could bring changes to SpO 2 (10-12)   .However, there is controversy about the colours which could bring changes to the values of SpO 2, and also if these changes could have repercussions on clinical practice to suggest the removal, or not, of the nail polish.
In a study carried out with healthy volunteers at rest, it was observed that the colours green and blue reduced SpO 2 by about 6%, while black and brown caused a reduction of 3% (10) .In another similar study, the colours blue, beige, purple and white brought about significant declines in SpO 2 (11).A third study, using ten different colours of nail polish on healthy volunteers, showed only brown and black to reduce SpO 2 , from 97±0.31% to 95±0.46% and 95.9±0.06% to 93.9±0.94%respectively (12) .
These differences are apparently explained by a greater difference in the absorption of light by spectrophotometry, leading the pulse oximeter to detect a greater proportion of deoxyhaemoglobin (10) .In our study, the base colour, as well as light pink and red, did not have any influence on the SpO 2 reading among bearers of DPOC at rest and also during exercise, while only brown brought SpO 2 down (95±1.8% to 93.8±2.3%), with a mean SpO 2 difference of 1.2±0.5% when at rest.
Our data has also confirmed the findings of other studies that have also observed a reduction in SpO 2 with the use of nail polish, but without any relevance on clinical practice due to the small diferences observed (15,18) .
In patients with pulmonary disease, measurements of the oxygenation of arterial blood during exercise could be important for the appraisal of the disease, accompaniment of the response to the treatment, and also the analysis of the need for supplementing the oxygen supply, the seriousness of the illness and also the symptoms associated to exercise.Several studies have shown that the pulse oximeter supplies accurate measurements of the arterial oxygen saturation in healthy individuals during exercise and also among patients with pulmonary problems (24) .
When we assess the different colours over time, we see that the base colour and also light pink have not had any influence on the SpO 2 reading.In contrast, red brought a reduction in SpO 2 in the fourth minute of exercise when compared to rest, varying from 94.8±2.0% to 93.8±3.4%, and brown reduced SpO 2 at rest and also at the different time points during the exercise.Only one study (15) assessed the variation of SpO 2 over a period of five minutes, with the SpO 2 values being recorded every minute.In this study, the authors confirmed that the SpO 2 values remained constant over time, but this study was conducted with healthy individuals and at rest.Among the four colours used, only red showed a significant interference on the SpO 2 reading.However, the altered values were still within the limits of normality, varying between 96 and 99%.
In the present study, red showed a reduction in SpO 2 , but the decline was also small (1.3±0.5%) in spite of the statistical significance.In addition, the results are different in the fact that the present study has been carried out with patients while taking exercise.
The findings of the present study are in agreement with a study carried out on healthy individuals subjected to conditions of hypoxia induced by high altitudes, at rest and also while taking exercise (walking), which did not affect the SpO 2 readings when different colours of nail polish were used, including brown, red and pink (25) .
In our study, the reduction in the SpO 2 values during exercise was significant in the case of brown, when compared to the other colours -namely base colour, light pink and red, both at the fourth and the sixth minute of exercise, showing a lower value for SpO 2 with statistical significance.The differences between the means ranged between 0.8±0.3% and 1,6±0.5% during exercise.
Important limitations in all studies here described, which make it more difficult to compare these studies, lie in the reduced size of the sample studied, as well as the limited use of the number and the type of the different colours and also the different equipment of pulse oximetry as used.At the same time, most studies were carried out on healthy volunteers.
In addition, there were no studies found that assessed the influence of nail polish on the SpO 2 value for patients with chronic obstructive pulmonary disease, during exercise.As a result, this fact makes it more difficult to compare the studies and also limits the scope of the findings to other populations and other exercise situations.
Even though in the present study a representative number of patients has been included, there has not been inclusion of any patients with significant desaturation; as also the number of colours of nail polish appraised was necessarily limited, which does not allow the present findings to be extended to other colours such as green, blue and black, as used in other similar studies.
In addition, the patients performed the step exercise for six minutes, as according to their own www.eerp.usp.br/rlaeShimoya-Bittencourt W, Pereira CAC, Diccini S, Bettencourt ARC.
rhythm and intensity, meaning that the maximum effort may not have been reached.

Conclusion
Among patients with DPOC, the use of brown nail polish brings a reduction in the SpO 2 reading, both at rest and also during exercise.The red colour only reduces SpO 2 during exercise.The clinical relevance of such findings is questionable, due to the small differences that have been found.

A
quasi-experimental study was carried out, in the pneumology outpatient department of the Júlio Müller University Hospital (Hospital Universitário Júlio Müller -HUJM) in the city of Cuiabá, State of Mato Grosso, Brazil, between November 2007 and December 2008.This study was approved by the Research Ethics Committee of HUJM (protocol No. 327/CEP-HUJM/07) and also by the Research and Ethics Committee of the Federal University of São Paulo (UNIFESP), under registration No. 1794/07.
The data was expressed as mean and standard deviation, or as a percentage.The mean values of SpO 2 were calculated before and after the application of the nail and also at the end of the exercise, for each colour of nail polish as assessed.The values observed were compared through the use of analysis of variance for repeated measurements (ANOVA-MR) with the use of the SPSS statistical software package, version 17.0 (Chicago, IL, United States).

T0=
Zero time, before the polish is applied; T 1 r = Time one at rest, after the polish is applied; T 4 e = Time four during exercise; T 5 e = Time five during exercise; T 6 e = Time six during exercise.

Table 2 -
Difference between the SpO 2 of the fingers (right -left) at rest, before the nail polish is appliedIn Table3, we can see the average SpO 2 with the different colours of polish and the respective controls,

Table 3 -
Mean ± standard deviation of SpO 2 among patients with DPOC for different colours with their respective controls, over time