Evaluation of the Effect of Localized Skin Cooling on Nasal Airway Volume by Acoustic Rhinometry1,2
MIKIKAZU YAMAGIWA, OLE HILBERG, OLE F. PEDERSEN, and GUNNAR R. LUNDQVIST
Introduction
T he vascular reaction of the nasal mucosa to cold exposure was investigated, with special attention to susceptibility to the common cold and hypersensitivity to nonimmunologic factors (1-5). Most investigators in the 1930s claimed that cooling of localized parts of the skin such as on hands, feet, or the back with cold water or air usually caused a shrinkage ofthe nasal mucosa (4). In contrast, some of the earlier and recent investigators have reported that they could not observe any definite reaction (4, 6), or they could observe swelling (5) instead of shrinkage. Thus, the results disagree. In those studies, the vascular reaction of the nasal mucosa was estimated by spirometry (6) or by balloon (3) or conventional rhinomanometric methods (4, 5). If the reactions were subtle and not well defined, difficulties could arise in assessing the reaction pattern by these methods. In the present study, we applied an acoustic method (7) to assess the vascular reaction of the nasal mucosa to cold exposure. Reflections of an acoustic pulse were analyzed to provide an estimate of nasal cross-sectional area as a function of the distance from the nostril, after which integration gave an estimate of nasal airway volume. This method has been used to make in vivo cross-sectional area measurements of the trachea (8, 9), the pharynx (10, 11), and the supraglottal oral cavity (12, 13),and in vitro measurement of the trachea and central airways in lung casts (14). A recent study in this institute has shown that the acoustic reflection method (acoustic rhinometry) provides an accurate method for measurement of the geometry of the nasal cavity (15). Acoustic rhinometry has made it possible to easily estimate nasal airway volume changes caused by vascular reactions of the nasal mucosa elicited by localized skin cooling. The aim of the present study was to apply acoustic rhinometry to investigate the reaction patterns of the nasal mucosa to exposure of localized skin 1050
SUMMARY Ten healthy SUbjects (four men and six women) were subjected to localized skin cooling by submersion for 5 min of both feet and, in another experiment, one hand and forearm into ice-cold water. Repeated measurements of nasal cavity volumes by a new method, acoustic rhinometry, showed characteristic patterns ranging from marked increases In volumes lasting the entire exposure period to transient monophasic or biphasic responses to no change at all. The pattern in individual SUbjects was reproducible with the two methods of cooling, and it could be characterized by five types when related to baseline measurements during the preexposure period. Because of large minute-to-minute variations, probably determined by local differences and fluctuations in blood flow in tissues through the nose, evaluation of induced changes in the nasal cavity volume cannot be based on single measurements as has frequently been done in the past by using rhinomanometry as the experimental method. The mechanisms behind the characteristic patterns in immediate human nasal response to local skin cooling challenge remains to be explored. AM REV RESPIR DIS 1990; 141:1050-1054
areas to cold. There are two reasons for doing this, one is to clarify whether unique patterns of reaction exist, the other is to find out the best way to describe reactions in the nose caused by environmental exposure. Methods Subjects Ten healthy subjects (four men and six women) who had no significant complaints or rhinoscopically overt nasal abnormalities were studied. Their ages ranged from 24 to 54 yr (mean ± SD, 32.1 ± 11.0). They were staff members of the institute or medical students (indoor occupation). Their annual number of common colds ranged from 0.8 (Subject 2) to 4 (Subject 7) (mean ± SD, 2.0 ± 0.9). Four subjects (Subjects 1, 3, 7, and 10)reported that exposure to cold often caused their common colds.
Environmental Conditions Except for the first four cooling experiments performed in a laboratory where the temperature was 18 to 19° C, the remaining experiments were carried out in a climate chamber (temperature, 22.1° C; relative humidity, 45 ± 5070; ventilation rate, 3 to 5 times/h). The subjects were dressed in their own casual indoor clothing with clo values (1 clo unit equals a heat resistance of 0.18° C m-h/kcal or 0.155° C m 2 / W ) (16)ranging from 0.6 to 0.8, providing thermal comfort at the given room temperature, air velocity, and physical activity (sitting). As the difference in room temperatures between the two experimental situations was considered insignificant, all results
were pooled together. All subjects were acclimatized to the indoor environment before the cold exposures.
Recording of Temperatures The temperature of the cold water was measured by a mercury thermometer. Surface temperatures of the nasal tip and the dorsal aspect of the terminal phalanx of the forefinger and the big toe were measured and recorded every minute by using thermocouples made of copper and constantan wire attached to the skin surface. Temperature recording was performed by a programmed setup of an HP3421A data acquisition control unit and an HP-85 computer (Hewlett-Packard, Cupertino, CA). Room temperature and humidity weremeasured by a thermoelectric instrument (Vaisala, type HM 14; Helsinki, Finland). Acoustic Rhinometry The experimental equipment for acoustic reflection measurements has been described previously (15) and will be only briefly described here. The apparatus includes (1) a computer (IBM AT-3) with an AID-converter (Dash-16; Metrabyte, Taunton, MA) for data acquisition and processing, (2) a trigger mod-
(Received in original form February 27, 1989 and in revised form August 7, 1989) 1 From the Institute of Environmental and Occupational Medicine, University of Arhus, Arhus, Denmark. 2 Correspondence andrequests forreprints should beaddressed to MikikazuYamagiwa, Department of Otolaryngology, MieUniversity School of Medicine, 2-174 Edobashi, Tsu, Mie 514 Japan.
1051
SKIN COOLING AND THE NASAL CAVITY
ule (Model TM-IlA; EG & G, Salem, MA), which produces the acoustic pulse, (3) a wave tube (internal diameter, 1.5 cm; length, 90 em) and a pieozo-electricmicrophone (Model 377; BBN, Cambridge, MA), and (4) a 20 dB amplifier and a 10 kHz low-pass filter. A spark, generated by the trigger module, is discharged between two electrodes placed in the end of the wave tube. This creates an acoustic pulse that propagates down the wave tube. It passes the microphone and enters the nasal cavity via the nosepiece, where it is reflected by changes in the local acoustic impedance resulting from changes in the crosssectional area of the nasal cavity. The analog signal from the microphone is amplified, lowpass-filtered, and digitized at a sampling rate of 40 kHz. The data are converted to an areadistance function by software described previously (7). The cross-sectional areas are determined for a distance up to 20 cm with a spatial resolution of approximately 0.4 em. The measurement itself lasts 8 ms, and it takes altogether 20 s for the complete data acquisition and storing process.
Feet Cooling Both feet, protected from the water by a thin plastic bag, were cooled by immersion in a large round tu b (height and bottom diameter were 43 and 45 em, respectively) containing ice and water. The temperature of the water was zero to 4 0 C, and the depth to which the legs were immersed was around 30 em from the heel. Hand and Forearm Cooling One hand and forearm, protected from the water by a thin plastic bag, was cooled by immersing in a bucket (height and bottom diameter were 25 and 20 ern, respectively) containing ice and water. The temperature ofthe water was zero to 4 C, and the arm was immersed to around 23 em from middle finger tip. One of the 10subjects did not participate in this study. 0
Experimental Protocol For each subject, the feet- and hand-cooling experiments were carried out on two separate days. The experiments were performed in quiet surroundings without observers to avoid distracting the subjects. During the whole cooling experiment, the temperatures of various parts of skin and the room temperature were recorded at I-min intervals. Reading ofthe water temperature was taken after stirring the water before and after immersing the feet or the hand. Three subjects (Subjects 1, 2, and 5) participated in repeated feet cooling experiments on separate days to investigate reproducibility; only data obtained at the first experiment wereused to calculate mean responses. Preexposure Measurements For at least 10 min (range, 10 to 25 min) before exposure, acoustic rhinometric measurements were carried out, first on the right side
and then on the left side every 1 to 4 min to determine a preexposure basic value of nasal airway volume.
cant change in exposure volumes was observed in the remaining six subjects. The toe temperature drop took place immediately after the onset of cooling. Measurements during Exposure Within the 5-min cooling period, no Acoustic rhinometric measurements wereperformed every 20 s during the 5-min exposure recovery was observed in the toe temperperiod, yielding possibly 15pairs of right and ature, and the minimum temperatures for left acoustic rhinometric measurements dur- each subject ranged from 4.8 to 17.6 C, ing the period if all were successfully made. but the magnitude of these temperature drops was not correlated with the magPostexposure Measurements nitude of nasal airway volume change. For at least 40 min (range 40 to 60 min), In the hand-cooling experiment (nine postexposure measurements were carried out subjects), the exposure volume was sigat the same frequency as preexposure meanificantly higher than the preexposure surements to investigate the postexposure reactions. Data from the first and second 20- volume in one subject, lower in two, but not significantly different in six. The foremin periods were treated separately in order to separate initial and later postexposure finger temperature drop took place immediately after the immersion of the arm effects. and never recovered until the end of the Data Analysis 5-min exposure period. The lowest temA program using ASYST (McMillan Scien- peratures recorded from each subject tific program) was written and used for analwere distributed from 5.3 to 13.60 C. ysis of the acoustic rhinometric data. Airway In the hand-cooling period, temperavolumes of the right and left nasal cavities tures of the nasal tip, contralateral forebetween 2 and 8 em from the nostrils were calculated separately and added. Changes of finger, and toe decreased clearly in six, this summed nasal airway volume provided nine, and two subjects, respectively. The an estimate of vascular reactions of nasal comparison of averaged volumes of each period did not seem very useful for estimucosa to the cold exposure. mation of rapid nasal volume change Statistics caused by cold exposure. Therefore, we The Mann-Whitney rank-sum test was used plotted volumes of nasal airway volume for comparison of means of nasal volume against time, and paid attention to the values in the exposure and the postexposure change of nasal airway volume in the periods with that of the preexposure period. period that started 5 min before the cooling and ended 5 min after the cooling: Results 15 min altogether. Results from a hand-cooling experiment In the majority of the subjects, the naare shown in figure 1. During the expo- sal airway volume increased just after the sure period, the skin temperature on the start of cooling, but decreased again beexposed hand dropped to about 10 C. fore the end of exposure. In half of the After exposure, the temperature increased experiments, the volume decreased to a towards the preexposure values. The con- level lower than the preexposure level tralateral hand temperature decreased within 5 min after the end of cooling. significantly, whereas the nose temperaBy analyzing the volume change in that ture did not change in this subject. The period, we could classify the response nasal cavity volume increased during ex- pattern of nasal airway volume into five posure. There was some fluctuation in basic types, as shown in figure 2. the nasal volume during the entire exType A. This pattern was characterperimental period. ized by continuous increased nasal airThe principal data of the effect of way volume during the exposure period. localized skin cooling on nasal airway After the end of exposure, the volume volume for the different periods in the started to decrease and returned to the individual subjects are summarized in ta- preexposure level (AI) or returned to a ble 1. The results are means and standard level lower than the preexposure level deviations of all measurements in the giv- (A2). en periods. The nasal volume varied beType B. This pattern was characterized tween the defined periods in a rather un- by increased nasal airway volume just afsystematic way. In the exposure period, ter the start of exposure. It was followed however, the volume during the feet- by a decrease of the volume within the cooling experiment was significantly high- exposure period. After the end of the exer than the preexposure volumes in four posure, it returned to the preexposure levof the 10 subjects, and none showed sig- el (BI) or returned to a level lower than nificantly lower values. But no signifi- the preexposure level (B2). 0
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YAMAGIWA, HILBERG, PEDERSEN, AND LUNDQVIST
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MIKIKAZU YAMAGIWA, OLE HILBERG, OLE F. PEDERSEN, and GUNNAR R. LUNDQVIST
Introduction
T he vascular reaction of the nasal mucosa to cold exposure was investigated, with special attention to susceptibility to the common cold and hypersensitivity to nonimmunologic factors (1-5). Most investigators in the 1930s claimed that cooling of localized parts of the skin such as on hands, feet, or the back with cold water or air usually caused a shrinkage ofthe nasal mucosa (4). In contrast, some of the earlier and recent investigators have reported that they could not observe any definite reaction (4, 6), or they could observe swelling (5) instead of shrinkage. Thus, the results disagree. In those studies, the vascular reaction of the nasal mucosa was estimated by spirometry (6) or by balloon (3) or conventional rhinomanometric methods (4, 5). If the reactions were subtle and not well defined, difficulties could arise in assessing the reaction pattern by these methods. In the present study, we applied an acoustic method (7) to assess the vascular reaction of the nasal mucosa to cold exposure. Reflections of an acoustic pulse were analyzed to provide an estimate of nasal cross-sectional area as a function of the distance from the nostril, after which integration gave an estimate of nasal airway volume. This method has been used to make in vivo cross-sectional area measurements of the trachea (8, 9), the pharynx (10, 11), and the supraglottal oral cavity (12, 13),and in vitro measurement of the trachea and central airways in lung casts (14). A recent study in this institute has shown that the acoustic reflection method (acoustic rhinometry) provides an accurate method for measurement of the geometry of the nasal cavity (15). Acoustic rhinometry has made it possible to easily estimate nasal airway volume changes caused by vascular reactions of the nasal mucosa elicited by localized skin cooling. The aim of the present study was to apply acoustic rhinometry to investigate the reaction patterns of the nasal mucosa to exposure of localized skin 1050
SUMMARY Ten healthy SUbjects (four men and six women) were subjected to localized skin cooling by submersion for 5 min of both feet and, in another experiment, one hand and forearm into ice-cold water. Repeated measurements of nasal cavity volumes by a new method, acoustic rhinometry, showed characteristic patterns ranging from marked increases In volumes lasting the entire exposure period to transient monophasic or biphasic responses to no change at all. The pattern in individual SUbjects was reproducible with the two methods of cooling, and it could be characterized by five types when related to baseline measurements during the preexposure period. Because of large minute-to-minute variations, probably determined by local differences and fluctuations in blood flow in tissues through the nose, evaluation of induced changes in the nasal cavity volume cannot be based on single measurements as has frequently been done in the past by using rhinomanometry as the experimental method. The mechanisms behind the characteristic patterns in immediate human nasal response to local skin cooling challenge remains to be explored. AM REV RESPIR DIS 1990; 141:1050-1054
areas to cold. There are two reasons for doing this, one is to clarify whether unique patterns of reaction exist, the other is to find out the best way to describe reactions in the nose caused by environmental exposure. Methods Subjects Ten healthy subjects (four men and six women) who had no significant complaints or rhinoscopically overt nasal abnormalities were studied. Their ages ranged from 24 to 54 yr (mean ± SD, 32.1 ± 11.0). They were staff members of the institute or medical students (indoor occupation). Their annual number of common colds ranged from 0.8 (Subject 2) to 4 (Subject 7) (mean ± SD, 2.0 ± 0.9). Four subjects (Subjects 1, 3, 7, and 10)reported that exposure to cold often caused their common colds.
Environmental Conditions Except for the first four cooling experiments performed in a laboratory where the temperature was 18 to 19° C, the remaining experiments were carried out in a climate chamber (temperature, 22.1° C; relative humidity, 45 ± 5070; ventilation rate, 3 to 5 times/h). The subjects were dressed in their own casual indoor clothing with clo values (1 clo unit equals a heat resistance of 0.18° C m-h/kcal or 0.155° C m 2 / W ) (16)ranging from 0.6 to 0.8, providing thermal comfort at the given room temperature, air velocity, and physical activity (sitting). As the difference in room temperatures between the two experimental situations was considered insignificant, all results
were pooled together. All subjects were acclimatized to the indoor environment before the cold exposures.
Recording of Temperatures The temperature of the cold water was measured by a mercury thermometer. Surface temperatures of the nasal tip and the dorsal aspect of the terminal phalanx of the forefinger and the big toe were measured and recorded every minute by using thermocouples made of copper and constantan wire attached to the skin surface. Temperature recording was performed by a programmed setup of an HP3421A data acquisition control unit and an HP-85 computer (Hewlett-Packard, Cupertino, CA). Room temperature and humidity weremeasured by a thermoelectric instrument (Vaisala, type HM 14; Helsinki, Finland). Acoustic Rhinometry The experimental equipment for acoustic reflection measurements has been described previously (15) and will be only briefly described here. The apparatus includes (1) a computer (IBM AT-3) with an AID-converter (Dash-16; Metrabyte, Taunton, MA) for data acquisition and processing, (2) a trigger mod-
(Received in original form February 27, 1989 and in revised form August 7, 1989) 1 From the Institute of Environmental and Occupational Medicine, University of Arhus, Arhus, Denmark. 2 Correspondence andrequests forreprints should beaddressed to MikikazuYamagiwa, Department of Otolaryngology, MieUniversity School of Medicine, 2-174 Edobashi, Tsu, Mie 514 Japan.
1051
SKIN COOLING AND THE NASAL CAVITY
ule (Model TM-IlA; EG & G, Salem, MA), which produces the acoustic pulse, (3) a wave tube (internal diameter, 1.5 cm; length, 90 em) and a pieozo-electricmicrophone (Model 377; BBN, Cambridge, MA), and (4) a 20 dB amplifier and a 10 kHz low-pass filter. A spark, generated by the trigger module, is discharged between two electrodes placed in the end of the wave tube. This creates an acoustic pulse that propagates down the wave tube. It passes the microphone and enters the nasal cavity via the nosepiece, where it is reflected by changes in the local acoustic impedance resulting from changes in the crosssectional area of the nasal cavity. The analog signal from the microphone is amplified, lowpass-filtered, and digitized at a sampling rate of 40 kHz. The data are converted to an areadistance function by software described previously (7). The cross-sectional areas are determined for a distance up to 20 cm with a spatial resolution of approximately 0.4 em. The measurement itself lasts 8 ms, and it takes altogether 20 s for the complete data acquisition and storing process.
Feet Cooling Both feet, protected from the water by a thin plastic bag, were cooled by immersion in a large round tu b (height and bottom diameter were 43 and 45 em, respectively) containing ice and water. The temperature of the water was zero to 4 0 C, and the depth to which the legs were immersed was around 30 em from the heel. Hand and Forearm Cooling One hand and forearm, protected from the water by a thin plastic bag, was cooled by immersing in a bucket (height and bottom diameter were 25 and 20 ern, respectively) containing ice and water. The temperature ofthe water was zero to 4 C, and the arm was immersed to around 23 em from middle finger tip. One of the 10subjects did not participate in this study. 0
Experimental Protocol For each subject, the feet- and hand-cooling experiments were carried out on two separate days. The experiments were performed in quiet surroundings without observers to avoid distracting the subjects. During the whole cooling experiment, the temperatures of various parts of skin and the room temperature were recorded at I-min intervals. Reading ofthe water temperature was taken after stirring the water before and after immersing the feet or the hand. Three subjects (Subjects 1, 2, and 5) participated in repeated feet cooling experiments on separate days to investigate reproducibility; only data obtained at the first experiment wereused to calculate mean responses. Preexposure Measurements For at least 10 min (range, 10 to 25 min) before exposure, acoustic rhinometric measurements were carried out, first on the right side
and then on the left side every 1 to 4 min to determine a preexposure basic value of nasal airway volume.
cant change in exposure volumes was observed in the remaining six subjects. The toe temperature drop took place immediately after the onset of cooling. Measurements during Exposure Within the 5-min cooling period, no Acoustic rhinometric measurements wereperformed every 20 s during the 5-min exposure recovery was observed in the toe temperperiod, yielding possibly 15pairs of right and ature, and the minimum temperatures for left acoustic rhinometric measurements dur- each subject ranged from 4.8 to 17.6 C, ing the period if all were successfully made. but the magnitude of these temperature drops was not correlated with the magPostexposure Measurements nitude of nasal airway volume change. For at least 40 min (range 40 to 60 min), In the hand-cooling experiment (nine postexposure measurements were carried out subjects), the exposure volume was sigat the same frequency as preexposure meanificantly higher than the preexposure surements to investigate the postexposure reactions. Data from the first and second 20- volume in one subject, lower in two, but not significantly different in six. The foremin periods were treated separately in order to separate initial and later postexposure finger temperature drop took place immediately after the immersion of the arm effects. and never recovered until the end of the Data Analysis 5-min exposure period. The lowest temA program using ASYST (McMillan Scien- peratures recorded from each subject tific program) was written and used for analwere distributed from 5.3 to 13.60 C. ysis of the acoustic rhinometric data. Airway In the hand-cooling period, temperavolumes of the right and left nasal cavities tures of the nasal tip, contralateral forebetween 2 and 8 em from the nostrils were calculated separately and added. Changes of finger, and toe decreased clearly in six, this summed nasal airway volume provided nine, and two subjects, respectively. The an estimate of vascular reactions of nasal comparison of averaged volumes of each period did not seem very useful for estimucosa to the cold exposure. mation of rapid nasal volume change Statistics caused by cold exposure. Therefore, we The Mann-Whitney rank-sum test was used plotted volumes of nasal airway volume for comparison of means of nasal volume against time, and paid attention to the values in the exposure and the postexposure change of nasal airway volume in the periods with that of the preexposure period. period that started 5 min before the cooling and ended 5 min after the cooling: Results 15 min altogether. Results from a hand-cooling experiment In the majority of the subjects, the naare shown in figure 1. During the expo- sal airway volume increased just after the sure period, the skin temperature on the start of cooling, but decreased again beexposed hand dropped to about 10 C. fore the end of exposure. In half of the After exposure, the temperature increased experiments, the volume decreased to a towards the preexposure values. The con- level lower than the preexposure level tralateral hand temperature decreased within 5 min after the end of cooling. significantly, whereas the nose temperaBy analyzing the volume change in that ture did not change in this subject. The period, we could classify the response nasal cavity volume increased during ex- pattern of nasal airway volume into five posure. There was some fluctuation in basic types, as shown in figure 2. the nasal volume during the entire exType A. This pattern was characterperimental period. ized by continuous increased nasal airThe principal data of the effect of way volume during the exposure period. localized skin cooling on nasal airway After the end of exposure, the volume volume for the different periods in the started to decrease and returned to the individual subjects are summarized in ta- preexposure level (AI) or returned to a ble 1. The results are means and standard level lower than the preexposure level deviations of all measurements in the giv- (A2). en periods. The nasal volume varied beType B. This pattern was characterized tween the defined periods in a rather un- by increased nasal airway volume just afsystematic way. In the exposure period, ter the start of exposure. It was followed however, the volume during the feet- by a decrease of the volume within the cooling experiment was significantly high- exposure period. After the end of the exer than the preexposure volumes in four posure, it returned to the preexposure levof the 10 subjects, and none showed sig- el (BI) or returned to a level lower than nificantly lower values. But no signifi- the preexposure level (B2). 0
0
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YAMAGIWA, HILBERG, PEDERSEN, AND LUNDQVIST
25
(Subject MY,
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-
0
1988-03-07)
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