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The nasal volume of children as measured by Manometric Rhinometry
R4l%RNATlONALJO~LOF
Pediitric International Journal of Pediatric Otorhinolaryngology 35 (1996) 51-57
ELSEVIER
The nasal volume of children as measured by Manometric Rhinometry M.J. Porter*“, LG. Williamsonb,
D.H. Kerridgeb, A.R. Maw”
“ENT Department, St. Michael’s Hospital, Bristol, UK bDepartment of Primary Care, University of Southampton, Southampton, UK Received 3 April
1995; revision received 20 September 1995; accepted I October 1995
Abstract
A new method of measuring nasal volume has been developed called ‘Manometric Rhinometry’. We describe the principle behind its use and present the results of measuring two groups of normal children aged 4410. The total volume of the nasal cavity, paranasal sinuses and postnasal space in these children averaged 81 ml in 4-year olds and 140 ml in IO-year olds when measured using an open cell foam plug. Where a rigid nasal tip was used the volume averaged 67 ml in 4-year olds rising to 99 ml in 8-year olds. Correlation with age, weight, height and head circumference showed the greatest correlation with height (r = 0.66). Multiple regression analysis did not add further explanatory power. Keyword.s:
Manometric rhinometry; Nasal volume; Nasal cavity; Paranasal sinuses; Postnasal
space
1. Introduction The volume of the airspace in the nose and paranasal sinuses is difficult to measure. There have been studies in adults based on anatomical dissection [6],
displacement of the air by water [2] or acoustic rhinometry [3]. In children only acoustic rhinometry has been used. This measures the volume of the nasal cavity and nasopharynx [l] but excludes the sinuses. As the child grows, not only does the * Corresponding
author.
0165-5876/96/$15.00 0 1996 Elsevier Science Ireland Ltd. All rights reserved SSDI 0165-5876(95)01288-M
52
M.J. Porter et al, / Int. J. Pediatr. Otorhinolaryngol.
35 (1996) 51-57
nasal cavity enlarge but the sinuses also develop from rudimentary outgrowths into large air-filled cavities. A new method of measuring the volume of the airspace within the nasal cavity, nasopharynx and sinuses in both adults and children has been described [4,5]. It has been called ‘Manometric Rhinometry’. The principle is to turn the nasal cavity into a closed system and then extract a given volume of air from it. According to Boyle’s Law of Gases (PV = nRT) any change in the volume of air within such a closed cavity results in a pressure change. This pressure change can be measured and the original volume of the system can be calculated from it. 2. Materials and methods The device is illustrated schematically in Fig. 1. An anterior nasal seal has been obtained by several methods. Originally we used a rigid circular plastic tip through which both tubes passed whilst occluding the other nostril by digital pressure. This method was used by two of the authors (IGW and DHK) for data collection. The other authors (MJP and ARM) obtained a seal by inserting a foam plug (Nicolet Ltd.) into each nostril. These plugs each have a hollow core to which is attached one of the two tubes from the rhinometer. The nasopharynx is closed by asking the child to blow a party blower (Fig. 2). Each time the child blows, the operator activates the rhinometer and records the pressure change. The wave form of the pressure change is displayed on an LCD screen and the reading of the maximum
Fig. 1. Schematic diagram of the Manometric Rhinometer.
M.J. Porter et al. 1 lnt. 1. Pediatr. Otorhinolaryngol.
35 (1996) 51-57
53
Fig. 2. Taking measurementsof nasal volume from a 4-year old child. Blowing the party blower elevates the soft palate to close off the nose posteriorly.
pressure change expressed as a figure in arbitrary units. Examination of the waveform of the pressure change enables the operator to determine whether an adequate seal has been obtained. The manometric rhinometer is calibrated by connecting the two tubes to a mechanical model of the nose and sinuses. The model is filled with water and that water is then extracted to produce an exponential curve of reading against volume. This curve can be transformed into a straight line by plotting the log of reading against the log of volume. Using a linear regression analysis this straight line is expressed mathematically and the volume can be calculated from the pressure reading according to the formula: Volume = exp( 12.051 -
1.477 In (Reading))
This mathematical model can be used to convert pressure readings directly into a volume measurement on a computer spreadsheet. We have used this method to examine two groups of normal children and to discover how the nasal volume changed in relation to the age, height, weight and head circumference of the children. In group A, 62 children aged 4-10 years old were examined (using the foam plug method of sealing anteriorly). In group B, 39 children aged 3- 10 years were examined using the rigid tip. Group A came from 2 schools in Bristol and group B came from 2 general practices near Southampton. In group A the children were questioned to exclude a history of known nasal or ear disease, previous surgery, intercurrent infection or disease. The age, height,
54
M.J. Porter et al. / Int. J. Pediatr. Otorhinolaryngol.
35 (1996) 51-57
weight and maximum head circumference for each child was recorded and then recordings of the nasal volume were made. Ten readings were taken from each child and the average of all 10 was converted into a volume using the above formula. The use of 10 readings per subject is an arbitrary one, however we have demonstrated that the test-retest correlation for this method is 0.94 in children [4]. The coefficient of variance for each subject in this group ranged from 2.92-14.76% (mean 9.32%). In group B the age of every child was recorded, and in certain cases height, weight and head circumference were also measured. Using data from their medical records, a history of middle ear effusion, ear surgery, nasal surgery and intercurrent illness was excluded. Three to five readings were taken of the nasal volume and the average used. This figure was converted to a volume using the calibration curve pertinent to that machine. The results were analysed on an IBM compatible PC using the SYSTAT statistics programme. A stepwise multiple regression analysis was performed and then a forced regression analysis was performed forcing each of the independent variables in turn into the analysis. 3. Results The average volume of the airspace within the nose paranasal sinuses and nasopharynx as measured in group A was 81 ml (S.D. 24 ml) at the age of 4 and rose to 140 ml (SD. 43 ml) by the age of 10. The correlation coefficients between each of the independent variables and the nasal volume is shown in Table 1. The nasal volume best correlates with height (r = 0.657). The plot of nasal volume against height is shown in Fig. 3. The results of a stepwise multiple regression analysis allowing possible inclusion of all 4 explanatory variables shows that the height accounts for 43% of the variance. Once height has been included in the mathematical model all the other factors are no longer significant. If height is excluded from the regression analysis age and weight can both be included but the total variation explained only reaches 41%. In group B the nasal volumes obtained were 67 ml ( + 25 ml) at 4 years of age rising to 99 ml ( + 22 ml) at age 8. In this group the nasal volume also correlated with age (v = 0.569) (Fig. 4). Table 1 Correlation coefficients for various independent variables for nasal volume as the dependent variable Dependent variable
Correlation coefficient (r)
Height Age Weight Head circumference
0.657 0.628 0.572 0.275
M.J. Porter et al. / hr. J. Pediafr. Otorhinohyngol.
55
35 (1996) 51-57
VOLUME ml
0 I
50
Fig. 3. Nasal
70
volume
90
110 HEIGHT cm
130
150
170
plotted against height for 62 children aged 4-10 years.
4. Discussion
The purpose of this study was to evaluate the new technique of ‘Manometric Rhinometry’ on a group of normal children. We wished to establish whether the technique can be used on a normal population, what the range of values obtained in that population was and to investigate how these volumes depended on likely factors such as age, height, weight and head circumference. This is an essential preliminary before further studies on populations with disease or after therapeutic manoeuvres. The results for the two groups of children differ slightly and this is probably due to differences in the exact methodology. In absolute terms these volumes appear prima face to be large. We believe that there are 3 reasons for this. (1) The nasal cavity volume and sinus volumes are combined. Using a mechanical model we have shown that if two volumes are connected by a tube as small as 0.5mm in diameter then the total volume is measured. (2) Unlike the mechanical model used for calibration the nose is not rigid. Any degree of compliance in the system will result in a lower pressure change and a higher apparent volume. (3) In children it is not yet possible to obtain a perfectly air tight seal. Leakage probably occurs anteriorly
56
M.J. Porter et al. / Int. J. Pediatr. Olorhinolaryngol.
35 (1996) 51-57
around and through the nasal plug. The Nicolet plug is an open cell foam and probably accounts for why the volumes appear higher than with the silastic tip. The plug however is easier to use. We are working to solve this technical problem and are experimenting with a closed cell plug. Preliminary results with specially made closed cell foam plugs gave similar values to those obtained with the plastic tip. Theoretically there may be a degree of velopharyngeal incompetence whilst blowing against a resistance but this was not clinically evident. If it had been present the effect of extracting air from the nose would have tended to reinforce the seal. An excessive leakage would also have been detected by the waveform of the pressure change and the results excluded. Although fluroscopic examination might have confirmed velopharyngeal closure this would have been both impractical and unethical. The results of the multiple regression analysis show how the nasal volume is dependent on the variables of age, height and weight. Because these variables are themselves closely interrelated the correlation between volume and each of these is similar and the variance accounted for by each term is also similar ranging from 33% for weight alone or 39% for age alone to 43% for height alone. Head
VOLUME ml 250
.
200
150
100
50 . l
*
0 0
2
4
6 AGE
8
10
Yrs Fig. 4. Nasal volume plotted against age for 39 children aged 3-10 years.
12
M.J. Porter et al. / Int. J. Pediatr. Otorhinolaryngol.
35 (1996) 51-57
57
circumference was a poor predictor of nasal volume. Although the two groups were examined independently using a slightly different technique the results are similar. The correlation of nasal volume and age was 0.63 for group A and 0.57 in group B. This strengthens the argument that these observations record a real phenomenon and that the technique is a valid one. The volume of the airspace in the nose, sinuses and nasopharynx will be affected by almost all the anatomical, physiological and pathological abnormalities that are likely to interest an Otolaryngologist. A method that can easily and reliably measure this space without the need for bulky and expensive equipment is needed and manometric rhinometry has the potential to fill this need. Although it lacks the spatial resolution of CT scanning, manometric rhinometry can be used in a laboratory or office setting for the repeated examination of individuals or groups where CT examination would be inappropriate, uneconomic, impractical or unethical. Unlike methods such as acoustic rhinometry or rhinomanometry the results are not determined principally by the point at which air flow is rate limited. Manometric rhinometry is still in its infancy but it has the potential to be a valuable tool in research and possibly clinical practice. It has been shown to be sensitive enough to measure the decongestant effect of xylometazoline in adults and further development of both hardware and software will improve the sensitivity and reliability of the technique. When examining children we have to take into account the added dimension of growth. These data show that nasal volume increases with the height, age and weight of children. Acknowledgements
Our thanks to the staff, parents and pupils of Torwood House school and Colston’s Primary school, Bristol for their co-operation with this study and also to patients and parents of Aldermoor, Southampton and Padnell Road, Cowplain practices for their kind co-operation with this study. Statistical advice from Mr. A. Hughes, senior lecturer in Epidemiology, University of Bristol. References [I] Elbrond, O., Hilberg, O., Felding, J.V. and Bleguad Anderson, 0. (1991) Acoustic rhinometry used as a method to demonstrate changes in the volume of the nasopharynx after adenoidectomy. Clin. Otolaryngol. 16, 84-86. [2] Gleeson, M.J., Youlton, L.J.F., Shelton, D.M. and Siodlac, M.Z. (1986) Assessment of nasal airway patency: a comparison of four methods. Clin. Otolaryngol. II, 99- 107. [3] Grymer, L.F., Hilberg, O., Pederson, O.F. and Rasmussen, T.R. (1991) Acoustic rhinometry; values from adults with subjective normal nasal patency. Rhinology 29, 35-47. [4] Porter, M.J., Williamson I., Kerridge, D. and Maw, A.R. (1995) Manometric Rhinometry a new method of measuring nasal volume. Rhinology 33, 86688. [5] Porter, M.J., Williamson, I.G., Kerridge, D.H. and Maw, A.R. (1995) Manometric rhinometry. Clin. Otolaryngol. 20, 3033304. [6] Ritter, F.N. (1978) The paranasal sinuses, Anatomy and surgical technique. C.V. Mosby company, St. Louis, MO.
Pediitric International Journal of Pediatric Otorhinolaryngology 35 (1996) 51-57
ELSEVIER
The nasal volume of children as measured by Manometric Rhinometry M.J. Porter*“, LG. Williamsonb,
D.H. Kerridgeb, A.R. Maw”
“ENT Department, St. Michael’s Hospital, Bristol, UK bDepartment of Primary Care, University of Southampton, Southampton, UK Received 3 April
1995; revision received 20 September 1995; accepted I October 1995
Abstract
A new method of measuring nasal volume has been developed called ‘Manometric Rhinometry’. We describe the principle behind its use and present the results of measuring two groups of normal children aged 4410. The total volume of the nasal cavity, paranasal sinuses and postnasal space in these children averaged 81 ml in 4-year olds and 140 ml in IO-year olds when measured using an open cell foam plug. Where a rigid nasal tip was used the volume averaged 67 ml in 4-year olds rising to 99 ml in 8-year olds. Correlation with age, weight, height and head circumference showed the greatest correlation with height (r = 0.66). Multiple regression analysis did not add further explanatory power. Keyword.s:
Manometric rhinometry; Nasal volume; Nasal cavity; Paranasal sinuses; Postnasal
space
1. Introduction The volume of the airspace in the nose and paranasal sinuses is difficult to measure. There have been studies in adults based on anatomical dissection [6],
displacement of the air by water [2] or acoustic rhinometry [3]. In children only acoustic rhinometry has been used. This measures the volume of the nasal cavity and nasopharynx [l] but excludes the sinuses. As the child grows, not only does the * Corresponding
author.
0165-5876/96/$15.00 0 1996 Elsevier Science Ireland Ltd. All rights reserved SSDI 0165-5876(95)01288-M
52
M.J. Porter et al, / Int. J. Pediatr. Otorhinolaryngol.
35 (1996) 51-57
nasal cavity enlarge but the sinuses also develop from rudimentary outgrowths into large air-filled cavities. A new method of measuring the volume of the airspace within the nasal cavity, nasopharynx and sinuses in both adults and children has been described [4,5]. It has been called ‘Manometric Rhinometry’. The principle is to turn the nasal cavity into a closed system and then extract a given volume of air from it. According to Boyle’s Law of Gases (PV = nRT) any change in the volume of air within such a closed cavity results in a pressure change. This pressure change can be measured and the original volume of the system can be calculated from it. 2. Materials and methods The device is illustrated schematically in Fig. 1. An anterior nasal seal has been obtained by several methods. Originally we used a rigid circular plastic tip through which both tubes passed whilst occluding the other nostril by digital pressure. This method was used by two of the authors (IGW and DHK) for data collection. The other authors (MJP and ARM) obtained a seal by inserting a foam plug (Nicolet Ltd.) into each nostril. These plugs each have a hollow core to which is attached one of the two tubes from the rhinometer. The nasopharynx is closed by asking the child to blow a party blower (Fig. 2). Each time the child blows, the operator activates the rhinometer and records the pressure change. The wave form of the pressure change is displayed on an LCD screen and the reading of the maximum
Fig. 1. Schematic diagram of the Manometric Rhinometer.
M.J. Porter et al. 1 lnt. 1. Pediatr. Otorhinolaryngol.
35 (1996) 51-57
53
Fig. 2. Taking measurementsof nasal volume from a 4-year old child. Blowing the party blower elevates the soft palate to close off the nose posteriorly.
pressure change expressed as a figure in arbitrary units. Examination of the waveform of the pressure change enables the operator to determine whether an adequate seal has been obtained. The manometric rhinometer is calibrated by connecting the two tubes to a mechanical model of the nose and sinuses. The model is filled with water and that water is then extracted to produce an exponential curve of reading against volume. This curve can be transformed into a straight line by plotting the log of reading against the log of volume. Using a linear regression analysis this straight line is expressed mathematically and the volume can be calculated from the pressure reading according to the formula: Volume = exp( 12.051 -
1.477 In (Reading))
This mathematical model can be used to convert pressure readings directly into a volume measurement on a computer spreadsheet. We have used this method to examine two groups of normal children and to discover how the nasal volume changed in relation to the age, height, weight and head circumference of the children. In group A, 62 children aged 4-10 years old were examined (using the foam plug method of sealing anteriorly). In group B, 39 children aged 3- 10 years were examined using the rigid tip. Group A came from 2 schools in Bristol and group B came from 2 general practices near Southampton. In group A the children were questioned to exclude a history of known nasal or ear disease, previous surgery, intercurrent infection or disease. The age, height,
54
M.J. Porter et al. / Int. J. Pediatr. Otorhinolaryngol.
35 (1996) 51-57
weight and maximum head circumference for each child was recorded and then recordings of the nasal volume were made. Ten readings were taken from each child and the average of all 10 was converted into a volume using the above formula. The use of 10 readings per subject is an arbitrary one, however we have demonstrated that the test-retest correlation for this method is 0.94 in children [4]. The coefficient of variance for each subject in this group ranged from 2.92-14.76% (mean 9.32%). In group B the age of every child was recorded, and in certain cases height, weight and head circumference were also measured. Using data from their medical records, a history of middle ear effusion, ear surgery, nasal surgery and intercurrent illness was excluded. Three to five readings were taken of the nasal volume and the average used. This figure was converted to a volume using the calibration curve pertinent to that machine. The results were analysed on an IBM compatible PC using the SYSTAT statistics programme. A stepwise multiple regression analysis was performed and then a forced regression analysis was performed forcing each of the independent variables in turn into the analysis. 3. Results The average volume of the airspace within the nose paranasal sinuses and nasopharynx as measured in group A was 81 ml (S.D. 24 ml) at the age of 4 and rose to 140 ml (SD. 43 ml) by the age of 10. The correlation coefficients between each of the independent variables and the nasal volume is shown in Table 1. The nasal volume best correlates with height (r = 0.657). The plot of nasal volume against height is shown in Fig. 3. The results of a stepwise multiple regression analysis allowing possible inclusion of all 4 explanatory variables shows that the height accounts for 43% of the variance. Once height has been included in the mathematical model all the other factors are no longer significant. If height is excluded from the regression analysis age and weight can both be included but the total variation explained only reaches 41%. In group B the nasal volumes obtained were 67 ml ( + 25 ml) at 4 years of age rising to 99 ml ( + 22 ml) at age 8. In this group the nasal volume also correlated with age (v = 0.569) (Fig. 4). Table 1 Correlation coefficients for various independent variables for nasal volume as the dependent variable Dependent variable
Correlation coefficient (r)
Height Age Weight Head circumference
0.657 0.628 0.572 0.275
M.J. Porter et al. / hr. J. Pediafr. Otorhinohyngol.
55
35 (1996) 51-57
VOLUME ml
0 I
50
Fig. 3. Nasal
70
volume
90
110 HEIGHT cm
130
150
170
plotted against height for 62 children aged 4-10 years.
4. Discussion
The purpose of this study was to evaluate the new technique of ‘Manometric Rhinometry’ on a group of normal children. We wished to establish whether the technique can be used on a normal population, what the range of values obtained in that population was and to investigate how these volumes depended on likely factors such as age, height, weight and head circumference. This is an essential preliminary before further studies on populations with disease or after therapeutic manoeuvres. The results for the two groups of children differ slightly and this is probably due to differences in the exact methodology. In absolute terms these volumes appear prima face to be large. We believe that there are 3 reasons for this. (1) The nasal cavity volume and sinus volumes are combined. Using a mechanical model we have shown that if two volumes are connected by a tube as small as 0.5mm in diameter then the total volume is measured. (2) Unlike the mechanical model used for calibration the nose is not rigid. Any degree of compliance in the system will result in a lower pressure change and a higher apparent volume. (3) In children it is not yet possible to obtain a perfectly air tight seal. Leakage probably occurs anteriorly
56
M.J. Porter et al. / Int. J. Pediatr. Olorhinolaryngol.
35 (1996) 51-57
around and through the nasal plug. The Nicolet plug is an open cell foam and probably accounts for why the volumes appear higher than with the silastic tip. The plug however is easier to use. We are working to solve this technical problem and are experimenting with a closed cell plug. Preliminary results with specially made closed cell foam plugs gave similar values to those obtained with the plastic tip. Theoretically there may be a degree of velopharyngeal incompetence whilst blowing against a resistance but this was not clinically evident. If it had been present the effect of extracting air from the nose would have tended to reinforce the seal. An excessive leakage would also have been detected by the waveform of the pressure change and the results excluded. Although fluroscopic examination might have confirmed velopharyngeal closure this would have been both impractical and unethical. The results of the multiple regression analysis show how the nasal volume is dependent on the variables of age, height and weight. Because these variables are themselves closely interrelated the correlation between volume and each of these is similar and the variance accounted for by each term is also similar ranging from 33% for weight alone or 39% for age alone to 43% for height alone. Head
VOLUME ml 250
.
200
150
100
50 . l
*
0 0
2
4
6 AGE
8
10
Yrs Fig. 4. Nasal volume plotted against age for 39 children aged 3-10 years.
12
M.J. Porter et al. / Int. J. Pediatr. Otorhinolaryngol.
35 (1996) 51-57
57
circumference was a poor predictor of nasal volume. Although the two groups were examined independently using a slightly different technique the results are similar. The correlation of nasal volume and age was 0.63 for group A and 0.57 in group B. This strengthens the argument that these observations record a real phenomenon and that the technique is a valid one. The volume of the airspace in the nose, sinuses and nasopharynx will be affected by almost all the anatomical, physiological and pathological abnormalities that are likely to interest an Otolaryngologist. A method that can easily and reliably measure this space without the need for bulky and expensive equipment is needed and manometric rhinometry has the potential to fill this need. Although it lacks the spatial resolution of CT scanning, manometric rhinometry can be used in a laboratory or office setting for the repeated examination of individuals or groups where CT examination would be inappropriate, uneconomic, impractical or unethical. Unlike methods such as acoustic rhinometry or rhinomanometry the results are not determined principally by the point at which air flow is rate limited. Manometric rhinometry is still in its infancy but it has the potential to be a valuable tool in research and possibly clinical practice. It has been shown to be sensitive enough to measure the decongestant effect of xylometazoline in adults and further development of both hardware and software will improve the sensitivity and reliability of the technique. When examining children we have to take into account the added dimension of growth. These data show that nasal volume increases with the height, age and weight of children. Acknowledgements
Our thanks to the staff, parents and pupils of Torwood House school and Colston’s Primary school, Bristol for their co-operation with this study and also to patients and parents of Aldermoor, Southampton and Padnell Road, Cowplain practices for their kind co-operation with this study. Statistical advice from Mr. A. Hughes, senior lecturer in Epidemiology, University of Bristol. References [I] Elbrond, O., Hilberg, O., Felding, J.V. and Bleguad Anderson, 0. (1991) Acoustic rhinometry used as a method to demonstrate changes in the volume of the nasopharynx after adenoidectomy. Clin. Otolaryngol. 16, 84-86. [2] Gleeson, M.J., Youlton, L.J.F., Shelton, D.M. and Siodlac, M.Z. (1986) Assessment of nasal airway patency: a comparison of four methods. Clin. Otolaryngol. II, 99- 107. [3] Grymer, L.F., Hilberg, O., Pederson, O.F. and Rasmussen, T.R. (1991) Acoustic rhinometry; values from adults with subjective normal nasal patency. Rhinology 29, 35-47. [4] Porter, M.J., Williamson I., Kerridge, D. and Maw, A.R. (1995) Manometric Rhinometry a new method of measuring nasal volume. Rhinology 33, 86688. [5] Porter, M.J., Williamson, I.G., Kerridge, D.H. and Maw, A.R. (1995) Manometric rhinometry. Clin. Otolaryngol. 20, 3033304. [6] Ritter, F.N. (1978) The paranasal sinuses, Anatomy and surgical technique. C.V. Mosby company, St. Louis, MO.