Article Text
Abstract
Objective The purpose of this study was to determine the effect of different colour nail polishes and henna on the measurement of oxygen saturation and the differences among the measurements of three pulse oximetry devices.
Material and methods 33 healthy females with a mean age of 19±1.0 years and no complaints or known disease were included into the study. All the participants applied henna to one of their fingers a day before the study. Just before the study, one finger was left empty as control and the other fingers were dyed using various colours of nail polish (red, blue, beige, purple, brown, white, pink, green, colourless polish, light blue, light green and yellow). There were more than eight colour nail polishes and some fingers were used for the other colours after being completely cleaned. The same brand nail polishes were used for the study. Oxygen saturation measurements were done using three different pulse oximetry devices (device I, II, III) from the control, different colour nail polished and henna applied fingers. The measurements of different devices, different colour nail polishes, henna and control were statistically compared.
Results The mean saturations obtained from blue, beige, purple and white nail polished fingers were significantly lower than those of control and the other coloured fingers. In addition, the mean measurement of device II was significantly lower than those of other devices.
Conclusion The results suggest that blue, beige, purple and white nail polished fingers might cause pulse oximetry devices to make incorrect measurements.
- Pulse oximetry
- oxygen saturation
- nail polish
- henna
- blood gas monitoring
- critical care
- clinical assessment
- intensive care
- nursing
- respiratory
- ventilation
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- Pulse oximetry
- oxygen saturation
- nail polish
- henna
- blood gas monitoring
- critical care
- clinical assessment
- intensive care
- nursing
- respiratory
- ventilation
Introduction
Measurement of the oxygen saturation in the arterial blood with the pulse oximeter is a very valuable non-invasive method for monitoring acute and critical patients.1–5 This method is widely used when there is a risk of hypoxaemia, during and after anaesthesia, in intensive care, during invasive procedures such as bronchoscopy, endoscopy, cardiac and central catheterisation, during emergency medical resuscitation of critically ill patients, when weaning patients from mechanical ventilation and titrating oxygen, while transferring patients from the operating room and intensive care, and when monitoring patients given inotropes, vasopressors, vasodilators, sedatives or analgesics.3 5 The baseline respiratory rate and subsequent changes including apnoea are also easily identified by a standard pulse oximeter.6 It is critical to fully understand the usage and limiting characteristics of this method so that the result can be analysed correctly. Pulse oximeter probes have light sources in two different wavelengths (red and infrared) on one side and a photodetector on the other.3 7 Oxyhaemoglobin and deoxyhaemoglobin absorb light at different wavelengths (940 nm and 660 nm respectively). Pulse oximeter devices use this feature and calculate the difference to measure the percentage of oxyhaemoglobin in arterial blood with a pulse, that is the arterial oxygen saturation (Sp02).3–5 7
Measurements with the pulse oximeter probe are usually made from the fingertips, earlobes and nasal bridge as they have a peripheral pulsatile vascular bed. The finger probe's performance is accepted to be better than those used at other sites and is used more frequently.3 7 Some factors such as haemoglobinopathies such as carboxyhaemoglobinaemia and methemoglobinaemia, hypothermia, hypotension, vasodilatation, vasoconstriction, severe anaemia, paints, skin pigmentation, strong ambient light, carbon monoxide poisoning, saturation lower than 70% and inappropriate sensor position can affect the oxygen saturation measured by pulse oximetry and cause inaccurate readings.2–4 8 Although not proven yet, it is widely believed that nail polishes also affect the accuracy of pulse oximeters.4 5 7 It is therefore suggested to remove nail polish, especially those with dark colours such as blue, black or green, and to place the probe on the side of the finger when the measurements are to be taken from the finger.1–3 5 9 10
Henna is obtained from the leaves of the Lawsonia inermis plant and provides a natural red colour. It is widely used in African and Asian countries and the eastern part of Turkey to paint the hair, feet, hands and nails.11 12 A limited number of studies have shown that red henna paste on the finger does not affect the saturation measured with the pulse oximeter.12–14 However, a study on hypoxaemic patients has shown a significantly higher saturation from the finger with henna paste applied.13
The aim of our study was to determine to what extent the henna paste and nail polish of various colours used by women in our country influenced the oxygen saturation measurement by pulse oximetry and whether the results differed between different instruments.
Materials and methods
A total of 33 healthy volunteer females with a mean age of 19±1.0 who had no symptoms or known disease were included in the study. We included 33 patients in the study, thinking that a number over 30 would be adequate to apply parametric tests during statistical analyses. The henna was mixed with water to make dough and applied to one fingernail of the women as in the conventional application and then covered with thin nylon (stretch film) 1 day before the study. The henna paste was washed and cleaned at the end of approximately 10 h. Red henna paste was used for the application and a red colour that would disappear in about 2–3 months was left on the nail and finger following washing afterwards. The fingers other than the one with henna paste and the one with nothing applied to use as control were painted with 13 different colours of nail polish (red, blue, beige, purple, brown, white, pink, black, green, varnish, light blue, light green, yellow). One layer of nail polish was applied to the nail and a second one was applied after the first one was completely dry. Once the measurements were made, the nail polish was cleaned completely and the other colour nail polish applied again if the finger was going to be used for another measurement, and all fingers were treated equally. The same brand of nail polish was used for all cases. Three different models of pulse oximeter (I. Rapido Portable (South Korea), II. Petas KMA 275 Monitor (Ankara, Turkey), III. Novametrix 515 Pulse Oximeter (Wallingford, Connecticut, USA)) were used to measure the oxygen saturation from the fingers with nothing applied, with henna paste and with 13 different colours of nail polish. All measurements were made at room temperature and in the same environment. The investigator applied the probe to the fingers in the same standard position (top-to-bottom) and the values on the instrument screen were recorded when constant. The results obtained were statistically compared between the various colours and the three instruments.
Statistical analysis
The descriptive statistics of the measurements from the groups are presented as mean±SD. The effect of the nail polish on the saturation measurements of the instrument was evaluated with the one-way analysis of variance test and the posthoc comparison of the subgroups was with the Tukey honestly significant differences test. A p value <0.05 was considered statistically significant.
Ethics considerations
Ethics approval for the study was received in 2009 at the beginning of the study from the institutional ethics board. The study purposes and methods were described to the participants by the researchers. Informed consent was signed by all the participants at the beginning of the study.
Limitations
A different finger was used for each colour of nail polish during the administration. The differences in saturation between the fingers of the same hand can be a limitation of this study. This study was also performed on healthy young women and therefore cannot be generalised.
Results
Comparison of the saturation levels measured from the fingers with no nail polish, nail polish of 13 different colours or henna paste using three different models of instrument in this study revealed that the saturation values from fingers with blue, beige, purple, brown and white nail polish were not markedly but significantly lower than the values from the other fingers with nail polish. The mean saturation value from the finger with henna paste was slightly higher than the finger with no nail polish but this was not statistically significant (figure 1). Measurements with pulse oximeter II were significantly higher than with the other two instruments (figure 2). Pulse oximeter I did not measure one and pulse oximeter III six fingers with black nail polish. Pulse oximeter III did not take measurements from two subjects with brown nail polish and one with dark blue nail polish. The lowest saturation value measured from the fingers with nail polish was 92%. Pulse oximeter I provided this value from a subject with black nail polish (while the value was 97% on the control finger) and pulse oximeter II provided this value in a subject with dark blue nail polish (while the value was 99% on the control finger).
Discussion
Comparison of the saturation levels measured from the fingers with no nail polish, nail polish of 13 different colours or henna paste using three different models of pulse oximeter in this study revealed that the saturation values from fingers with blue, beige, purple, brown and white nail polish were slight lower than the saturation values from the other fingers with nail polish. However, this difference was statistically significant. Cote et al investigated the effects of different nail polish colours (blue, green, purple, black and red) on pulse oximeter measurements in 14 healthy volunteers and found black and green nail polish to cause a decrease of 6% and black polish of 3% and these differences were significant, leading them to recommend routine removal of nail polish before taking saturation measurements.10 Rubin et al have also shown a decrease of saturation from 97% to 87% with blue nail polish.15 The significant decrease with blue nail polish in our study supports the results of these two studies. Cote et al have suggested it would be possible to overcome this problem with a simple change of probe position and studies this in 10 volunteers where they found that the original values were obtained unchanged when the probe was used in a side position and that there was no need to remove nail polish before saturation measurement.9 Another study on seven healthy subjects has evaluated the effect of taking pulse oximeter measurements with the probe in the standard position top to bottom and side-to-side position on the finger where 10 different colours of nail polish (red, yellow, dark blue, light blue, brown, white, green, black, purple, fuchsia) were used. Both the black and brown nail polish caused a significant 2% decrease in the standard position measurement while the side-to-side position measurement eliminated this small effect and there was therefore no need to remove the nail polish.1 We believe the significant decrease in measurements taken with the standard position with the brown nail polish in our study is similar to the result of this study.
Another study on 27 healthy volunteers with saturation of 95% or above has used 10 different colours of nail polish (red, orange, yellow, green, blue, black, brown, white, purple, pink) and two different instruments. Measurements were taken from fingers with or without nail polish using the side-to-side position. They found a decrease that was not clinically significant (less than 1% decrease) in both instruments with the brown and blue nail polish and in one instrument with the red. It was therefore stated that nail polish did not cause a significant change in pulse oximetry in healthy subjects.4 The significant decrease with the blue and brown nail polish in our study is similar to the results of this study.
One of three different studies used 10 different colours of nail polish (black, brown, red, orange, green, blue, grey, purple, white, beige) in 12 healthy volunteers and found no significant effect on pulse oximetry.2 A second study prospectively evaluated nine different colours of nail polish (black, dark blue, light blue, dark green, light green, yellow, red, purple, varnish) in 50 patients who were in critical condition or on a mechanical ventilator but normoxic in an intensive care unit and concluded that the nail polish did not change pulse oximeter results in patients on a mechanical ventilator in a way that was clinically significant.5 The third study used nine different colours of nail polish (black, brown, blue, purple, green, varnish, pink, red, orange) and two different brands of pulse oximeter in five healthy persons who were slightly hypoxaemic (mean saturation 91.3%) at a high altitude and found mean values of 91.4±4.1% in fingers with nail polish and 91.2±3.5% in those without, leading to the conclusion that nail polish had no significant effect. They also report no significant difference between the two instruments.7 Our results are different in that we have found a significant decrease in saturation with some colours of nail polish. We also found significantly higher measurements with pulse oximeter II. We believe this result is significant as it shows that pulse oximeters can provide different saturation measurements.
The saturation value from the finger with henna paste was slightly higher than the finger with no nail polish in our study but this was not statistically significant. A prospective study from Turkey has compared the effect of henna paste on the finger on pulse oximeter oxygen saturation measurements in 40 normoxic patients and found no statistically significant difference.11 Another study on the effect on henna paste in 104 normoxic and 14 hypoxaemic subjects found no significant difference in the normoxic group while the pulse oximeter saturation results from the finger with henna paste were statistically significantly higher in the hypoxaemic group.13 A study on the effect of red and black henna paste in 40 adult healthy females showed no effect of red henna paste while the pulse oximeter could not read saturation from the finger with black henna paste, leading to the recommendation of using the ear lobe for measurements in these patients.14
In conclusion, we found that the use of blue, beige, purple, brown or white nail polish in healthy young adults may have a negative effect on saturation measurement while red henna paste did not have a similar effect. We also believe different pulse oximeters may provide different measurements. We suggest removal of nail polish from the fingers after obtaining consent from patients presenting as emergencies or their relatives if necessary. The use of the ear for saturation measurement or placing the probe to the finger in the side-to-side position may also be suggested. The same study could be repeated in hypoxaemic patients in the future.
References
Footnotes
Competing interests None.
Patient consent Obtained.
Ethics approval This study was conducted with the approval of the Gulhane Military Medical Academy Local Ethics Committee; trial registration number: 1491-847-09/1539.
Provenance and peer review Not commissioned; externally peer reviewed.
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