MEASUREMENT OF WATER VAPOR LOSS THROUGH HUMAN
`NAIL IN VIVO*
`
`DAVID SPRUIT, PE_D.
`
`ABSTRACT
`
`A capsule is descnbed which can be used for the measurement of the water vapor
`loss of the nai! with the aid of the same instrumentation that has been used for the
`measurement of the water vapor loss of sk4n.
`The effective area of the described capsule has been determined applying an electric
`analog.
`The specific water permeability of ~he nail plate appeared to be independent of nail
`thickness in the finger nails of a healthy velumeer.
`
`The water vapor loss from the ~,il is of the
`same order as the water vapor loss from the skin
`of the l~alm; it is relatively high in comparison
`with the water vapor loss from most parts of the
`human body (1-3). The reliability of the meth-
`ods used previously may be criticized because
`~he possibility of displacement, of the normal
`water flow through the nail by the rim of ~he
`measuring capsule was not considered.
`
`METIKOD5
`
`Water vapor loss measurement. Dry nitrogen or
`dry air (less than 5 ppm water by volume) is
`passed over the nail The gas is led through a cap-
`-~ule attactmd to a polyethylene tube of the same
`diameter as the opening of the capsule (Fig. 1).
`The water loaded gas is led into an electrolytic
`water analyzer. Excep~ for the polye~y]ene robe,
`rite method is exactly the same as the one pub-
`lished before for the measurement of the water
`vapor lo~s from skin (7). The pressure of the cap-
`sule upon the nail is greater than the pressure oI
`tire skin capsule upon tim skin, since considerable
`force must be exerted in order to keep the capsule
`closely connected to the nail in spite of the flexi-
`bility of the polyethylene tubing, tIowever, the
`deformation caused by the pressure of the capsule
`in skin measurements is not aignific~mt in measure-
`merits performed on the more rigid nail material.
`The environmenLal circumstances of the meas-
`ment are the same as those for the measurement
`of water vapor loss from the palm, The main pre-
`cautio.na are to keep the subject calm and the tem-
`perature of the environmenL at about 18--19° C in
`order to avoid sweat gland activity.
`The water vapor loss from the naris of all fin-
`gers of a healthy volunteer was measured for 15
`minutes on fl~.ree successive days.
`
`Received October 12, 1970; accepted for publi-
`cation December 7, 1970.
`* From the Department of Dermatology of the
`University of Nijmegen, The Netherlands, Java-
`straat 104.
`
`The standard de~ iation of flae measurements was
`determined subsequentl~y and wa~ found ~o bE less
`than i5%.
`Thickness mea.s.ureme~d. The thickness of the
`nail plate was measttrt, d by me:m: of a vernier cal-
`iper.
`Electric a~,alog. The re~ etYcc~lve c:tpsule area
`was determined by mean, Of an electric analog
`(Fig. 2). The interfaces a) nail plate/inside of cap-
`sule, b) nail piat~,outside atmosphere, c) nail
`plate/nail bed, were represented by copper plates;
`the interface d) nail plateipolyetil.vlene tube of
`capsule, was represented by a plastic insulating
`ring. Tim water potential between the nail bed and
`the nail plate was represemed by a 30 mV electric
`potential. The nail plate material was represented
`by a 2% acid copper sulfate solution in dioxane.
`This so]ution was chosen since it undergoes mini-
`real electrolytic decomposition with a 30 mV elec-
`tric potent.ial. The flfickness of the nail plate was
`represented by the distance between the copper
`plates. The water permeation was therefore repre-
`sented by the electric current measured.
`Figure 2 shows the apparatus set up as an ana-
`log of the actual water loss measurements on
`skin, indudh~g the effects of the displa(:ed flow due
`to the rim of the polyethylene tubing. By lowering
`the insulating ring, through tim copper sulfate so-
`lution, to t~e lower copper plate, a model is ob-
`tained of the situation where no lateral "potential
`flow" occurs. The ratio between the two values ob-
`tained from the analog provides a correction fac-
`tor for the sldn measurements.
`
`B, ESULTS
`
`Water vapor toss. The standard deviation ex-
`pressed as a percentage of the water vapor loss
`measurements was ll%; the same value as has
`been found in water vapor loss measurements on
`the .ddn of the forearm and the palm (6).
`Results of the measurements of the water
`vapor loss from normal finger nails are shasta in
`column B of the Table. The results are similar
`
`359
`
`ARGENTUM EX1038
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`~60
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`THE JOURNAL OF I~rES’£IGATIVE DERMATOLOGY
`
`to the results of other investigators (1-3). It is
`moreo~-er obvious that the thicker nail 3detds the
`~¢maller water vapor loss. Therefore the "spe-
`cffic" water vapor loss has been calculated from
`the values of column B by multiplying these
`vaJues with t,he thickness of the relevant nail
`
`:F2a. 1. Capsule for earr>dng water loaded gas
`from d~e nail surface to the analyzer.
`
`pk~te (Cdumn A). The results are shown in
`column C.
`Electric analog. The results of the experiments
`with the electric analog indicated that when the
`thic -lmess of the nail plate was between 0.4 and
`0.8 man and the humidity of the ambient atmos-
`phere was between 20 and 80% at 19" C, the
`effective area of the described capsule appeared
`to be between 0.27 and 0.25 em-~. For the sake of
`simpScity the effective area. of the capsule was
`considered to be 0.26 cm~. The actual inner di-
`ameter was 0.20 cm~, and the outer was 0.38
`ell1~.
`
`DISCUSSION
`
`Normal water vapor loss is disturbed by plac-
`ing ~he capsule upon the nail plate. Because of
`the relative thictmess of the nail plate the water
`from the nail bed will reach the inside of the
`capsule ~hrough the nail plate along the flow
`hues which indicate the direction of the poten-
`t.in! gradient, illusCrated schematically in the
`
`po[yel’hyle,ne ~u be
`
`A
`
`nail bed
`
`’
`
`’
`
`l. 1ram " -i :1. - ;
`[
`~ ,.
`[ .....
`
`1
`
`.
`
`,::,~,":
`:,
`
`1
`
`central , I ’,
`
`plafe
`
`J
`
`~- <<
`
`~-iass dish confainin,.g 2%~id
`copper sulphate e~lution in dioxa ne
`
`pper pla~e
`
`lcrn
`I
`
`3~
`
`FIo. 2. The upper part of the figure (A) shows the route of the water penetrating the nai!
`plate when a capsule has been mounted. The lower part of ~e figure (B) illustrates 4:e elec-
`tale analog used for the determination of the effective permeating area under conditions of
`variable humidity of the outer atmosphere (variable voltage between outer and lower cop-
`per plate) and of variable nail thickness (variable distance between upper and lower copper
`plates).
`
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`

`W&TER LOSS THROUGH ~’AIL
`
`361
`
`upper part of Figure 2. The amount of water
`reaching the in, de of the capsule will, therefore,
`be related to an area of the n~]l which exceeds
`*,.he 0.20 cm= internal area of the capsule. The
`effective area of permeation is dependent upon
`the thickness of the nail piate and the humidity
`of the outer atmosphere. The influence of the
`thickne.*~ of the nail plate wa~ studied ~th the
`electric analog (Fig. 2, lower part) by raising
`~nd lowering the lowest copper plate; the influ-
`ence of the humidity of the a~mosphere was
`studied by varying the electric potential of the
`outer copper plate. The results of these varia-
`tions are largely dependent on the dimen~ons of
`the analog, which are anaIogous to the dimen-
`sion~ of the capsule used in the measurement of
`x he water vapor loss. The sum of these variables
`given an effective permeation area of 0.27-0.25
`ca= ~,nd is. therefore, only valid for the de-
`~(rribed (.,psu]e when used on t,he nail and simi-
`larly thick Iavers. The effeedve capsule area is
`~herefore 025 -_ 0.01 ca’-’. This variation may
`be ]~nored in the measurement of the water
`vapor loss as it causes an error of less than 4%;
`while the relative standard deviation of the
`measurement of the water vapor toss is some
`!0%.
`The nail plate has been described as consisting
`of three different layers; a dorsal, an intermedi-
`ate and a vemral part (4}. Lewis (5) states that
`there is "a dissimilar variable pattern in the
`mature digit:". If there were any marked differ-
`ences between the permeability of those different
`layers, this would appear as a difference in the
`permeabifity per unit thickness found for differ-
`eni nails; tiffs is not, seen.
`The specific permeability of various finger
`nails may therefore b,e compared to each other.
`The specific water vapor loss (Table, column C)
`being the product of the measured total water
`v’lpor loss and the thiclmezs of the nail (Table,
`(’olurans B and A) has been calculated assuming
`that this "specific" water vapor loss is constant
`for all of the healthy nails of one individual. The
`mean specific water vapor loss appeared to be
`0.t30 mg!(cm.hr) in the inveztigated individ-
`ual; the values of the various individual nails
`
`TABLE
`Permeation of water through the nails of the
`10 firugers of a healthy human being
`
`Hand
`
`Finger
`
`C
`(= B,0.1 A)
`Water
`Specific
`A
`vapor
`water va~or
`Nail
`]loss per-
`loss (sp~c.
`~hic "kness
`.mention,)
`permeabil-
`m: rag,
`it},) ha: rag/
`(cm-O-5our)
`tom-hour)
`
`left
`right
`left
`righ~
`left
`r~ght
`left
`right
`left
`right
`
`I humb
`thumb
`index
`index
`middle
`middle
`ring
`ring
`little
`little
`
`0,70
`0.65
`0.58
`0.60
`0.54
`O. 48
`
`O.4g
`o. 46
`o. 47
`
`1 85
`1 .,91
`1.,}8
`2.18
`2.41
`9 "23
`
`2,65
`3.07
`2.77
`
`O. 130
`O. 125
`0.120
`O. 130
`0.130
`0.1t0
`O, 145
`{I. 135
`0.1’40
`0.130
`
`Mean of Ml n::,ils
`
`0.54
`
`2.40
`
`0. 130
`
`are .~cattered about tbi~ average value, including
`the thick thumb nail and the thin nail of the
`little finger, the standard dexiafon being only
`7.59;. Obviously in these experiments the specific
`water vapor lo~ was the same for all nails of the
`fingers of the healthy mdividual.
`
`REFERENCES
`
`1. Blank, I. H,: Further observations on factors
`which influence the water content of tlne stra-
`tum corneum. 5, tnves u Derm.. ~1 : 259. 1953,
`2. Burch. G. E. and Winsor, T, : Diffusion of water
`~hrough dead plantar palmar and torsal hu-
`man skin and through me. n:,i]~. Arch. Derm,
`Syph., 53: 39. 1946.
`3. Jacobi, 0,: Die Niigel des lebenden Menschen
`und die Perspirado insensibilis. Arch. Klin.
`Exp. Derm.. ~t~: 559. 1962.
`4. Jan’ett, A. and Spearman. R. I. C. : The histo-
`chemistry of tt~e human nail. Arch. Derm., 9~:
`652. 1966.
`5. Lewis, B, L,: Microscopic studies of fetal and
`m at,ure nail and surroundmz soft tissve. Arch.
`Derm.. 70: 782. 1954.
`6. Spruit. D. and Molten, K. E_: Epidermal water-
`barrier formation after stril~ping of normal
`skin. J. Invest. Derm.. 45: 6. 1965.
`7. Sp.ntit, D. and Molten, K. E.: The regeneration
`rate of the water vapour loss of heavily dam-
`aged skin. Dermatologica, 182: i15. 1966.
`
`Page 3
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