J . COMMUN . DISORD . 24 (1991), 141-156
RESPIRATORY DYNAMICS AND SPEECH INTELLIGIBILITY IN SPEAKERS WITH GENERALIZED DYSTONIA GARY R . LaBLANCE Departments of Communication Disorders and Otolaryngology, Head-Neck Surgery, Saint Louis University
DAVID R . RUTHERFORD Department of Communicative Sciences and Disorders, Northwestern University
This study investigated aspects of respiratory function, during quiet breathing and monologue, in six adult dystonic subjects and compared the findings to a control group of four neurologically intact adults . Additionally, breathing dynamics were compared with speech intelligibility . Respiratory inductive plethysmography was used to assess breathing rate, periodicity of the breathing pattern . and inspiratory lung volume . Ear oximetry was used to assess arterial blood oxygen saturation . Speech intelligibility was rated by a panel of five judges . Breathing patterns differed between groups ; the dystonic subjects showed a faster breathing rate, less rhythmic breathing pattern, decreased lung volume, and apnealike periods accompanied by a decrease in arterial blood oxygen saturation . These differences were observed during quiet breathing and monologue . Decreased speech intelligibility was strongly related to differences in breathing dynamics .
INTRODUCTION Generalized dystonia is a progressive neuromuscular disorder of unknown pathophysiology . It is often found in persons of Eastern European ancestry and is characterized by sustained, involuntary twisting movements, which may affect muscle groups of varying size in the face, neck, trunk, and/or limbs (Fahn, 1988) . The symptoms generally appear between the ages of 6 and 16 years . The initial symptoms usually present in the foot and progress quickly to involve the limbs and trunk. The rate of progression slows noticeably after adolescence . When in an advanced form, the dystonia may affect tongue motion, speech, and swallowing (Ribera and Cooper, 1960) . Little is known about the pathophysiology or the neurological/bioAddress correspondence to Gary R . LaBlance . Department of Otolaryngology HeadNeck Surgery, Saint Louis University School of Medicine, 3660 Vista, Suite 312, St . Louis, MO 63110. ® 1991 by Elsevier Science Publishing Co ., Inc. 655 Avenue of the Americas, New York, NY 10010
141 0021-9924/91/$3 .50
142
G . R . LaBLANCE and D . R . RUTHERFORD
chemical pathologies of dystonia . Although no convincing neurobiochemical or histological changes have been identified, past literature has associated the disorder with an abnormality involving the basal ganglia (Denny-Brown, 1962 ; Cooper, 1976 ; Grossman and Kelly, 1976 ; Hedreen, Zwieg, DeLong, Whitehouse, and Price, 1988) . Most drug$ used in the management of neurologic disorders have been tried in the treatment of dystonia ; however, few have proven effective and those that do seldom result in more than limited success (Marsden, 1981) . Surgical procedures such as cryothalmectomy and implantation of a dorsal column stimulator have also been utilized, but, as with drugs, have failed to achieve universal or long-term effects (Marsden, 1981) . The literature on dystonia mentions associated speech disturbances . Abnormal muscle tone and movements in postural musculature have been observed to interfere with phonation (Zeman and Dyken, 1968 ; Eldridge, 1970 ; Isgreen, Fahn, Barrett, Snider, and Chutorian, 1976) . The speech disturbance has been called slow hyperkinetic dysarthyria by Darley, Aronson, and Brown (1975) and is characterized by excessive variations in loudness, audible inhalations, slow rate, aphonic breaks, short phrases, and transient breathiness . These speech characteristics suggest some aberration in breathing . Disturbances in respiratory dynamics have been described in various other extrapyramidal disorders including cerebral palsy (Hull, 1940 ; Perlstein and Shere, 1946 ; Blumberg, 1955a ; Blumberg, 1955b ; Westlake and Rutherford, 1961 ; McDonald and Chance, 1964), Parkinson's disease (Wolf and Lennox, 1928 ; Turner and Critchley, 1925 ; Grewel, 1957 ; Mier, Boshes, and Canter, 1960 ; Mier, 1967 ; Kim, 1968 ; Lilker and Woolf, 1968 ; Bendall, 1976), and Huntington's disease (Hansotia, 1968) ; yet, to date, respiratory dynamics in individuals with dystonia have gone unstudied . In the absence of research, this investigation was designed to systematically study breathing rate and pattern, inspiratory volume, and arterial blood oxygen saturation and to compare these findings with speech intelligibility .
METHOD Subjects All subjects in the experimental group underwent orthopedic, genetic, and neurological assessment by their private physicians and were diagnosed by their private neurologist as having generalized dystonia . All subjects had a normal perinatal history and no other sign of neurological damage . No subject had a history of encephalitis, brain trauma, or cardiac or pulmonary disturbance . Pertinent characteristics of the dystonia group are shown in Table 1 .
BREATHING AND SPEECH INTELLIGIBILITY IN DYSTONIA
143
Table 1 . Characteristics of Dystonia Subjects Sex Age at onset (years) Years since onset Family history Eastern European ancestry Surgical procedures Cryothalmectomy Deep brain stimulator Number of surgeries Current medication Artane Clonopin Cogentin Resent Symmetrel Valium Site of involvement Upper face Lower face Neck Upper extremities Trunk Lower extremities
S#l
S#2
S#3
S#4
S#5
S#6
M 14 17
M 24 9
F 15 8
F 23 15
F 11 8
M 12 16
+
+
+
+
+
+
+ -
+ +
-
+
+ -
3
3
3
0
8
2
-
+
+
-
-
+
+ + + + + +
+ + + + + +
+ +
+ + + + +
+
+
-
+ + + + +
+ + + + + +
+ + + + + +
Experimental subjects included three men and three women between the ages of 19 and 38 years (mean = 28 .65 years) . Ages of subjects at onset of the disorder ranged from 11 to 24 years (mean = 12 .17 years) . All dystonia subjects except subject 4 had undergone thalamic surgery . Most had repeated surgeries . Subject 3 also underwent implantation of two deep brain (pulvinar) stimulators and one spinal column stimulator ; all stimulators were functioning during the recordings made for this investigation . Subject 4 had received no surgical intervention . All subjects with dystonia were taking medication at the time of the study . No changes in medication had been made in the six-month period prior to the study . While all subjects reported a reduction in the severity of the dystonia as a result of the various forms of treatment, none experienced a total remission of the symptoms . No subject was taking any medication that is known or suspected to have an effect on respiratory function . A control group of four neurologically intact subjects was used to confirm normative data derived from pulmonary studies previously reported in the literature . The group of two men and two women ranged from 23 to 37 years (mean = 29 .21 years) . None had a personal or family history
144
G. R . LaBLANCE and D. R . RUTHERFORD
of neurological, respiratory, or circulatory disorders . Control subjects were selected on similarities in age, height, and weight to the dystonic subjects . Instrumentation Recording of rib cage and abdominal movements was accomplished via respiratory inductive plethysmography (Respitrace, manufactured by Ambulatory Monitoring, Inc .) . One transducer was placed around the rib cage, as close to the axillae as possible . The second transducer was placed around the abdomen in the midthoracic region between the lower ribs and the top of the pelvis . The size of the transducer was carefully selected for each subject to ensure a snug fit and to eliminate the risk of slippage . Positioning marks were made so that movement of the transducers could he detected . The transducers were periodically checked for slippage ; however, none was noted . Respiratory movements detected by the rib cage and abdominal transducers were processed by the Respitrace unit and were used to measure breathing rate and pattern . In addition, a third channel provided a summation of these two transducers . The signal from the summing circuit was used as a measure of inspiratory lung volume (Hunker, Bless, and Weismer, 1981 ; Cohn, Rao, Broudy, Birch, Watson, Atkins, Davis, Stott, and Sackner, 1982 ; Zimmerman, Connellan, Middleton, Tabora, Goldman, and Pride, 1983) . Ear oximetry (Biox IIA, manufactured by Biox Technology Inc . and distributed by Ambulatory Monitoring, Inc .) provided a measure of arterial oxygen saturation . Speech was recorded via a head-mounted Shure SM12 unidirectional dynamic microphone . All data were simultaneously recorded on a Beckman type R Dynograph and on a Hewlett-Packard 3968A Instrumentation Recorder . Equipment Calibration A multistep calibration procedure was used in the investigation (Cohn, 1982) . The first step calibrated the Respitrace amplifier gains to ensure equal voltage outputs for equal input signals . An internal reference voltage that approximate a signal deflection equal to a 1-liter displacement was utilized . With the reference voltage applied, the gains of the rib cage and abdominal amplifiers were adjusted so that the output signals read 1 .0 volts each . The second step of the procedure involved calibration of the Dynograph . The output signals of the Respitrace unit were sent to the Dynograph ; the preamplifiers of the Dynograph were adjusted to permit an equal excursion of each channel .
BREATHING AND SPEECH INTELLIGIBILITY IN DYSTONIA
145
The third step of the calibration adjusted the Respitrace signals to a volume measure . A Spirobag was used in the calibration procedure (Cohn, 1982) . A Spirobag is a perforated piece of cardboard tubing covered with a flexible plastic bag . The bag used had a fixed volume of 1 .3 liters . Subjects were asked to inhale to midinspiratory capacity, place the Spirobag into their mouth, and blow until the device became fully extended . The subjects were then instructed to inhale until the Spirobag was fully collapsed . This procedure was repeated 10 times in a semisupine position (160° angle) with the rib cage and abdominal transducers in place . A nose clip was used to prevent air from escaping through the nose . The volume data obtained during this calibration procedure were validated by wet spirometry . The procedure described above was repeated with a spirometer in place of the Spirobag (Cohn, 1982) . Ten representative breaths were selected from the test of the Spirobag and ten breaths from the spirometer . No statistically significant differences were noted . Calibration and standardization of the Biox 11A Ear Oximeter are preset . The calibration was checked by the manufacturer immediately prior to the initiation of this study and therefore required no additional calibration .
Artifact Subjects were placed in a semisupine position (approximately 160° angle) for comfort and to reduce movement artifact . Instances of head, trunk, and extremity movement were noted in writing on the Dynograph chart at the time of their occurrence, as were instances of yawning and coughing . These movement artifacts, representing less than 3% of the data collected, were not included in the analysis .
Experimental Procedures Continuous data recordings were made on five of the six dystonic subjects during two different 3-hour sessions scheduled approximately one week apart . Subject 1 became ill and could not return for the second session . Each of the four control subjects was studied for a single 3-hour session . A second session was not scheduled for the controls since the data obtained matched that reported in the literature for neurologically intact adults . Each session was divided into two 85-minute periods separated by a 15-minute rest . Data recording was halted during the rest period but the transducers and microphone remained in place . Calibration of the equipment was checked prior to resumption of data collection but in no case was recalibration required . Each 85-minute period began with 15 minutes of quiet breathing, followed by six 5-minute segments of spoken monologue . Each monologue
146
G . R. LaBLANCE and D . R . RUTHERFORD
was separated by five minutes of quiet breathing . Each period ended with an additional 15 minutes of quiet breathing . Measures of breathing rate and pattern, inspiratory volume, and arterial blood oxygen saturation were continuously and simultaneously recorded during quiet breathing and monologue for each 85-minute period . The 30 minutes of monologue obtained from the first session were tape recorded and played for a panel of five certified speech-language pathologists, each having a minimum of seven years of clinical experience . Each speech-language pathologist phonetically transcribed the monologues . A percentage of understood speech was calculated, as was interjudge reliability .
Data Analysis Each complete breathing cycle during quiet breathing and monologue was analyzed to determine rate of respiration, periodicity of the breathing pattern, inspiratory volume, and arterial blood oxygen saturation . The rate of respiration, defined as the average breaths per minute (bpm), was calculated by counting the number of complete respiratory cycles per task (quiet breathing or monologue) and dividing by the number of minutes required to complete that task . Task rates were averaged across trials within subjects and were reported as mean breathing rates . Variations across repetitions of a task within subjects were reported as standard deviations . Measures of cycle duration (inspiratory and expiratory phase of one respiratory cycle) were made to assess breathing patterns . The length of each respiratory cycle, from the point of maximum exhalation of one cycle to maximum exhalation of the adjacent cycle, was measured and reported . Since average duration of the respiratory cycle is the reciprocal to breathing rate, analysis of breathing pattern focused on variability of cycle duration, not average cycle duration . Lung volume was calculated by measuring the amplitude of each cycle in the summation trace and dividing the amplitude by a calibration factor . The calibration factor was determined in the calibration procedure of the Respitrace system by dividing the amplitude of the respiratory cycles taken during calibration by the volume of the Spirobag (Cohn, 1982) . All breaths within each task were measured . Means and standard deviations were calculated within subjects for each task . The Biox IIA Ear Oximeter provided calibration signals equivalent to 84 .9% saturation and 98 .2% saturation (SaO 2 ) . These two calibration signals were traced on the Dynograph print-out at the start of each session . The distance, in millimeters, from the 84 .9% Sa0 2 trace to the 98 .2% Sa02 trace was calculated . This distance was divided by the difference in percent saturation of the two signals to determine the percent saturation
BREATHING AND SPEECH INTELLIGIBILITY IN DYSTONIA
147
per millimeter on the printout . The distance between the actual Sa0 2 trace and the 84 .9% calibration trace was measured . Each measurement was multiplied by the calibration factor ; the product was then added to the 84 .9% base line . This calculation resulted in the determination of percent oxygen saturation at each 7 .5-second interval . The mean arterial oxygen saturation and standard deviation were calculated for each task .
RESULTS AND DISCUSSION Breathing Rate Figure 1 illustrates the differences in quiet and monologue breathing rates between the dystonic and control subjects . The mean rate of respiration during quiet breathing ranged from 14 to 27 bpm for dystonic subjects and was approximately 17 bpm for each control subject . The difference between the groups for this measure was not statistically significant (Mann-Whitney U test, U obs = 8, p > .05) . There was a statistical significance between the standard deviations for the dystonic subjects (1 .2-2 .6 bpm) and the control subjects (0 .9-1 .0 bpm) (Mann-Whitney test, Uo b s = 0, p n5 .05) . The average breathing rates during monologue were statistically different for the two groups with the dystonic group being higher (MannWhitney test, Uo b, = 0, p ~ .05) . Rates ranged from 15 to 24 bpm for
Dystonic subjects Control subjects
1
2
3
4
5 6 SUBJECT
= Quiet Breathing
7
B
9
10
Monologue
Figure 1 . Mean and standard deviation of respiratory rate by subject .
148
G . R . LaBLANCE and D . R. RUTHERFORD
individuals in the dystonic group and from 12 to 14 bpm for the controls . Standard deviations for the dystonic subjects ranged from 1 .1 to 5 .9 bpm, in comparison to 0 .5-0 .8 bpm for control subjects . Standard deviations were found to be statistically significant as well (Mann-Whitney test, U„b , =0,p :s .05) . Unexpectedly, the rate of breathing during monologue was more rapid than in quiet breathing for 5 of the 6 dystonia subjects .
Breathing Pattern Figure 2 illustrates the variability in duration of respiratory cycles in quiet breathing and monologue breathing for the two subject groups . Greater variability in cycle-to-cycle duration of quiet breathing was seen in the dystonic subjects, with standard deviations ranging from 0 .27 to 0 .83 seconds, compared to the control subjects range of 0 .18-0 .28 seconds . This difference was found to be statistically significant MannWhitney test, Uob , = l, p t .05) . Similarly, variations in the cycle duration during monologue were found between groups . Significant differences in standard deviations of 0 .290 .96 seconds were found in the dystonia group while standard deviations of 0 .16-0 .28 seconds were found in the control group (Mann-Whitney test, Uoh, = 0, p
RESPIRATORY DYNAMICS AND SPEECH INTELLIGIBILITY IN SPEAKERS WITH GENERALIZED DYSTONIA GARY R . LaBLANCE Departments of Communication Disorders and Otolaryngology, Head-Neck Surgery, Saint Louis University
DAVID R . RUTHERFORD Department of Communicative Sciences and Disorders, Northwestern University
This study investigated aspects of respiratory function, during quiet breathing and monologue, in six adult dystonic subjects and compared the findings to a control group of four neurologically intact adults . Additionally, breathing dynamics were compared with speech intelligibility . Respiratory inductive plethysmography was used to assess breathing rate, periodicity of the breathing pattern . and inspiratory lung volume . Ear oximetry was used to assess arterial blood oxygen saturation . Speech intelligibility was rated by a panel of five judges . Breathing patterns differed between groups ; the dystonic subjects showed a faster breathing rate, less rhythmic breathing pattern, decreased lung volume, and apnealike periods accompanied by a decrease in arterial blood oxygen saturation . These differences were observed during quiet breathing and monologue . Decreased speech intelligibility was strongly related to differences in breathing dynamics .
INTRODUCTION Generalized dystonia is a progressive neuromuscular disorder of unknown pathophysiology . It is often found in persons of Eastern European ancestry and is characterized by sustained, involuntary twisting movements, which may affect muscle groups of varying size in the face, neck, trunk, and/or limbs (Fahn, 1988) . The symptoms generally appear between the ages of 6 and 16 years . The initial symptoms usually present in the foot and progress quickly to involve the limbs and trunk. The rate of progression slows noticeably after adolescence . When in an advanced form, the dystonia may affect tongue motion, speech, and swallowing (Ribera and Cooper, 1960) . Little is known about the pathophysiology or the neurological/bioAddress correspondence to Gary R . LaBlance . Department of Otolaryngology HeadNeck Surgery, Saint Louis University School of Medicine, 3660 Vista, Suite 312, St . Louis, MO 63110. ® 1991 by Elsevier Science Publishing Co ., Inc. 655 Avenue of the Americas, New York, NY 10010
141 0021-9924/91/$3 .50
142
G . R . LaBLANCE and D . R . RUTHERFORD
chemical pathologies of dystonia . Although no convincing neurobiochemical or histological changes have been identified, past literature has associated the disorder with an abnormality involving the basal ganglia (Denny-Brown, 1962 ; Cooper, 1976 ; Grossman and Kelly, 1976 ; Hedreen, Zwieg, DeLong, Whitehouse, and Price, 1988) . Most drug$ used in the management of neurologic disorders have been tried in the treatment of dystonia ; however, few have proven effective and those that do seldom result in more than limited success (Marsden, 1981) . Surgical procedures such as cryothalmectomy and implantation of a dorsal column stimulator have also been utilized, but, as with drugs, have failed to achieve universal or long-term effects (Marsden, 1981) . The literature on dystonia mentions associated speech disturbances . Abnormal muscle tone and movements in postural musculature have been observed to interfere with phonation (Zeman and Dyken, 1968 ; Eldridge, 1970 ; Isgreen, Fahn, Barrett, Snider, and Chutorian, 1976) . The speech disturbance has been called slow hyperkinetic dysarthyria by Darley, Aronson, and Brown (1975) and is characterized by excessive variations in loudness, audible inhalations, slow rate, aphonic breaks, short phrases, and transient breathiness . These speech characteristics suggest some aberration in breathing . Disturbances in respiratory dynamics have been described in various other extrapyramidal disorders including cerebral palsy (Hull, 1940 ; Perlstein and Shere, 1946 ; Blumberg, 1955a ; Blumberg, 1955b ; Westlake and Rutherford, 1961 ; McDonald and Chance, 1964), Parkinson's disease (Wolf and Lennox, 1928 ; Turner and Critchley, 1925 ; Grewel, 1957 ; Mier, Boshes, and Canter, 1960 ; Mier, 1967 ; Kim, 1968 ; Lilker and Woolf, 1968 ; Bendall, 1976), and Huntington's disease (Hansotia, 1968) ; yet, to date, respiratory dynamics in individuals with dystonia have gone unstudied . In the absence of research, this investigation was designed to systematically study breathing rate and pattern, inspiratory volume, and arterial blood oxygen saturation and to compare these findings with speech intelligibility .
METHOD Subjects All subjects in the experimental group underwent orthopedic, genetic, and neurological assessment by their private physicians and were diagnosed by their private neurologist as having generalized dystonia . All subjects had a normal perinatal history and no other sign of neurological damage . No subject had a history of encephalitis, brain trauma, or cardiac or pulmonary disturbance . Pertinent characteristics of the dystonia group are shown in Table 1 .
BREATHING AND SPEECH INTELLIGIBILITY IN DYSTONIA
143
Table 1 . Characteristics of Dystonia Subjects Sex Age at onset (years) Years since onset Family history Eastern European ancestry Surgical procedures Cryothalmectomy Deep brain stimulator Number of surgeries Current medication Artane Clonopin Cogentin Resent Symmetrel Valium Site of involvement Upper face Lower face Neck Upper extremities Trunk Lower extremities
S#l
S#2
S#3
S#4
S#5
S#6
M 14 17
M 24 9
F 15 8
F 23 15
F 11 8
M 12 16
+
+
+
+
+
+
+ -
+ +
-
+
+ -
3
3
3
0
8
2
-
+
+
-
-
+
+ + + + + +
+ + + + + +
+ +
+ + + + +
+
+
-
+ + + + +
+ + + + + +
+ + + + + +
Experimental subjects included three men and three women between the ages of 19 and 38 years (mean = 28 .65 years) . Ages of subjects at onset of the disorder ranged from 11 to 24 years (mean = 12 .17 years) . All dystonia subjects except subject 4 had undergone thalamic surgery . Most had repeated surgeries . Subject 3 also underwent implantation of two deep brain (pulvinar) stimulators and one spinal column stimulator ; all stimulators were functioning during the recordings made for this investigation . Subject 4 had received no surgical intervention . All subjects with dystonia were taking medication at the time of the study . No changes in medication had been made in the six-month period prior to the study . While all subjects reported a reduction in the severity of the dystonia as a result of the various forms of treatment, none experienced a total remission of the symptoms . No subject was taking any medication that is known or suspected to have an effect on respiratory function . A control group of four neurologically intact subjects was used to confirm normative data derived from pulmonary studies previously reported in the literature . The group of two men and two women ranged from 23 to 37 years (mean = 29 .21 years) . None had a personal or family history
144
G. R . LaBLANCE and D. R . RUTHERFORD
of neurological, respiratory, or circulatory disorders . Control subjects were selected on similarities in age, height, and weight to the dystonic subjects . Instrumentation Recording of rib cage and abdominal movements was accomplished via respiratory inductive plethysmography (Respitrace, manufactured by Ambulatory Monitoring, Inc .) . One transducer was placed around the rib cage, as close to the axillae as possible . The second transducer was placed around the abdomen in the midthoracic region between the lower ribs and the top of the pelvis . The size of the transducer was carefully selected for each subject to ensure a snug fit and to eliminate the risk of slippage . Positioning marks were made so that movement of the transducers could he detected . The transducers were periodically checked for slippage ; however, none was noted . Respiratory movements detected by the rib cage and abdominal transducers were processed by the Respitrace unit and were used to measure breathing rate and pattern . In addition, a third channel provided a summation of these two transducers . The signal from the summing circuit was used as a measure of inspiratory lung volume (Hunker, Bless, and Weismer, 1981 ; Cohn, Rao, Broudy, Birch, Watson, Atkins, Davis, Stott, and Sackner, 1982 ; Zimmerman, Connellan, Middleton, Tabora, Goldman, and Pride, 1983) . Ear oximetry (Biox IIA, manufactured by Biox Technology Inc . and distributed by Ambulatory Monitoring, Inc .) provided a measure of arterial oxygen saturation . Speech was recorded via a head-mounted Shure SM12 unidirectional dynamic microphone . All data were simultaneously recorded on a Beckman type R Dynograph and on a Hewlett-Packard 3968A Instrumentation Recorder . Equipment Calibration A multistep calibration procedure was used in the investigation (Cohn, 1982) . The first step calibrated the Respitrace amplifier gains to ensure equal voltage outputs for equal input signals . An internal reference voltage that approximate a signal deflection equal to a 1-liter displacement was utilized . With the reference voltage applied, the gains of the rib cage and abdominal amplifiers were adjusted so that the output signals read 1 .0 volts each . The second step of the procedure involved calibration of the Dynograph . The output signals of the Respitrace unit were sent to the Dynograph ; the preamplifiers of the Dynograph were adjusted to permit an equal excursion of each channel .
BREATHING AND SPEECH INTELLIGIBILITY IN DYSTONIA
145
The third step of the calibration adjusted the Respitrace signals to a volume measure . A Spirobag was used in the calibration procedure (Cohn, 1982) . A Spirobag is a perforated piece of cardboard tubing covered with a flexible plastic bag . The bag used had a fixed volume of 1 .3 liters . Subjects were asked to inhale to midinspiratory capacity, place the Spirobag into their mouth, and blow until the device became fully extended . The subjects were then instructed to inhale until the Spirobag was fully collapsed . This procedure was repeated 10 times in a semisupine position (160° angle) with the rib cage and abdominal transducers in place . A nose clip was used to prevent air from escaping through the nose . The volume data obtained during this calibration procedure were validated by wet spirometry . The procedure described above was repeated with a spirometer in place of the Spirobag (Cohn, 1982) . Ten representative breaths were selected from the test of the Spirobag and ten breaths from the spirometer . No statistically significant differences were noted . Calibration and standardization of the Biox 11A Ear Oximeter are preset . The calibration was checked by the manufacturer immediately prior to the initiation of this study and therefore required no additional calibration .
Artifact Subjects were placed in a semisupine position (approximately 160° angle) for comfort and to reduce movement artifact . Instances of head, trunk, and extremity movement were noted in writing on the Dynograph chart at the time of their occurrence, as were instances of yawning and coughing . These movement artifacts, representing less than 3% of the data collected, were not included in the analysis .
Experimental Procedures Continuous data recordings were made on five of the six dystonic subjects during two different 3-hour sessions scheduled approximately one week apart . Subject 1 became ill and could not return for the second session . Each of the four control subjects was studied for a single 3-hour session . A second session was not scheduled for the controls since the data obtained matched that reported in the literature for neurologically intact adults . Each session was divided into two 85-minute periods separated by a 15-minute rest . Data recording was halted during the rest period but the transducers and microphone remained in place . Calibration of the equipment was checked prior to resumption of data collection but in no case was recalibration required . Each 85-minute period began with 15 minutes of quiet breathing, followed by six 5-minute segments of spoken monologue . Each monologue
146
G . R. LaBLANCE and D . R . RUTHERFORD
was separated by five minutes of quiet breathing . Each period ended with an additional 15 minutes of quiet breathing . Measures of breathing rate and pattern, inspiratory volume, and arterial blood oxygen saturation were continuously and simultaneously recorded during quiet breathing and monologue for each 85-minute period . The 30 minutes of monologue obtained from the first session were tape recorded and played for a panel of five certified speech-language pathologists, each having a minimum of seven years of clinical experience . Each speech-language pathologist phonetically transcribed the monologues . A percentage of understood speech was calculated, as was interjudge reliability .
Data Analysis Each complete breathing cycle during quiet breathing and monologue was analyzed to determine rate of respiration, periodicity of the breathing pattern, inspiratory volume, and arterial blood oxygen saturation . The rate of respiration, defined as the average breaths per minute (bpm), was calculated by counting the number of complete respiratory cycles per task (quiet breathing or monologue) and dividing by the number of minutes required to complete that task . Task rates were averaged across trials within subjects and were reported as mean breathing rates . Variations across repetitions of a task within subjects were reported as standard deviations . Measures of cycle duration (inspiratory and expiratory phase of one respiratory cycle) were made to assess breathing patterns . The length of each respiratory cycle, from the point of maximum exhalation of one cycle to maximum exhalation of the adjacent cycle, was measured and reported . Since average duration of the respiratory cycle is the reciprocal to breathing rate, analysis of breathing pattern focused on variability of cycle duration, not average cycle duration . Lung volume was calculated by measuring the amplitude of each cycle in the summation trace and dividing the amplitude by a calibration factor . The calibration factor was determined in the calibration procedure of the Respitrace system by dividing the amplitude of the respiratory cycles taken during calibration by the volume of the Spirobag (Cohn, 1982) . All breaths within each task were measured . Means and standard deviations were calculated within subjects for each task . The Biox IIA Ear Oximeter provided calibration signals equivalent to 84 .9% saturation and 98 .2% saturation (SaO 2 ) . These two calibration signals were traced on the Dynograph print-out at the start of each session . The distance, in millimeters, from the 84 .9% Sa0 2 trace to the 98 .2% Sa02 trace was calculated . This distance was divided by the difference in percent saturation of the two signals to determine the percent saturation
BREATHING AND SPEECH INTELLIGIBILITY IN DYSTONIA
147
per millimeter on the printout . The distance between the actual Sa0 2 trace and the 84 .9% calibration trace was measured . Each measurement was multiplied by the calibration factor ; the product was then added to the 84 .9% base line . This calculation resulted in the determination of percent oxygen saturation at each 7 .5-second interval . The mean arterial oxygen saturation and standard deviation were calculated for each task .
RESULTS AND DISCUSSION Breathing Rate Figure 1 illustrates the differences in quiet and monologue breathing rates between the dystonic and control subjects . The mean rate of respiration during quiet breathing ranged from 14 to 27 bpm for dystonic subjects and was approximately 17 bpm for each control subject . The difference between the groups for this measure was not statistically significant (Mann-Whitney U test, U obs = 8, p > .05) . There was a statistical significance between the standard deviations for the dystonic subjects (1 .2-2 .6 bpm) and the control subjects (0 .9-1 .0 bpm) (Mann-Whitney test, Uo b s = 0, p n5 .05) . The average breathing rates during monologue were statistically different for the two groups with the dystonic group being higher (MannWhitney test, Uo b, = 0, p ~ .05) . Rates ranged from 15 to 24 bpm for
Dystonic subjects Control subjects
1
2
3
4
5 6 SUBJECT
= Quiet Breathing
7
B
9
10
Monologue
Figure 1 . Mean and standard deviation of respiratory rate by subject .
148
G . R . LaBLANCE and D . R. RUTHERFORD
individuals in the dystonic group and from 12 to 14 bpm for the controls . Standard deviations for the dystonic subjects ranged from 1 .1 to 5 .9 bpm, in comparison to 0 .5-0 .8 bpm for control subjects . Standard deviations were found to be statistically significant as well (Mann-Whitney test, U„b , =0,p :s .05) . Unexpectedly, the rate of breathing during monologue was more rapid than in quiet breathing for 5 of the 6 dystonia subjects .
Breathing Pattern Figure 2 illustrates the variability in duration of respiratory cycles in quiet breathing and monologue breathing for the two subject groups . Greater variability in cycle-to-cycle duration of quiet breathing was seen in the dystonic subjects, with standard deviations ranging from 0 .27 to 0 .83 seconds, compared to the control subjects range of 0 .18-0 .28 seconds . This difference was found to be statistically significant MannWhitney test, Uob , = l, p t .05) . Similarly, variations in the cycle duration during monologue were found between groups . Significant differences in standard deviations of 0 .290 .96 seconds were found in the dystonia group while standard deviations of 0 .16-0 .28 seconds were found in the control group (Mann-Whitney test, Uoh, = 0, p
