The Journal of

Laryngology and Otology (Founded in 1887 by MORELL MACKENZIE and

NORRIS WOLFENDEN)

December Clinical research in speech pathology By J. K. F. ANTHONY and I. MALCOLM FARQUHARSON

(Edinburgh) OUR previous paper (Farquharson and Anthony, 1970) on Speech Pathology described specialized apparatus and a number of new techniques of measurement that had been developed in the Voice and Speech Disorders Clinic of the Royal Infirmary of Edinburgh. This paper will be more concerned with the results of applying these techniques and will present findings from a selection of clinical cases. Research, however, has continued on two long-standing problems. One is the provision of a more efficient method for the visual examination of the larynx which would allow it to be studied as it functions normally. The other is to find ways of investigating the organization of the thoracic and respiratory system in the speech production process? Indirect laryngoscopy using the classic technique of head reflector and laryngeal mirror was the method used from the start in this clinic, but even at quite an early stage it was realized that, even with synchronized stroboscopy, it seldom gave satisfactory information on how the larynx performed in speech. The tongue, in normal practice, must be held extended before the laryngeal area can be seen and the production of any kind of voicing is found extremely difficult by the average patient; any study of laryngeal function while the patient speaks is impossible. The answer seemed to lie in the development of a fibre-optic (Baird, 1927; Hopkins and Kapany, 1954) instrument combining viewing and illumination facilities which would have a small enough outside diameter to allow it to be passed through the nose into the pharynx to observe the larynx directly. A number of optical companies were asked to consider the manufacture of such an instrument, but without success, and research here 1169

J. K. F. Anthony and I. Malcolm Farquharson had to be confined to rigid fibre laryngoscopes designed to be introduced through the mouth. It was not until 1967 that the Olympus Optical Company of Japan (Sawashima and Hirose, 1968) produced a thin fibreoptic laryngoscope, and in 1970 one of these was obtained for evaluation in this laboratory. At first the laryngoscope was used for research work in phonation and in establishing what the practical problems would be in using it clinically. As experience was gained, however, it came more and more into general use and it has now supplanted the old method (Farquharson, Anthony and Williams, 1974). The original light source provided tungsten light which was not entirely satisfactory for viewing or photography, but our new high-power source gives true colour rendering with daylight type illumination and allows 16 mm. colour cine-photography. We had not used this laryngoscope long before we realized that a great deal of information about the larynx was lost to us by not having stroboscopic light. The provision of an efficient stroboscopic source poses some serious optical problems because the light-emitting area of the strobe tube is so much larger than the area of the end of the light-carrying conduit. We were fortunate in having Barr and Stroud in Glasgow design and produce a coupling device in 1971, and although the amount of light at the vocal cords is not as great as we would wish, the vibration movement can be seen quite clearly and with good synchronization it can be studied in slow motion. This facility has proved invaluable in investigations into hoarseness and voice disorders in general. It should be stressed perhaps that what is seen is very close to the true movement because the viewing instrument does not interfere with the articulatory or phonatory mechanism. When we turn to the problem of ascertaining how we organize our lung volume and thoracic system (Donald, 1953) for the needs of speech we find ourselves faced with three fundamental questions. First, how does the lung volume change as we speak? (Gutzman, 1928) Secondly, is there any kind of conflict between the requirements of breathing and speaking? Thirdly, do we predict in any way the actual volume of air that we are about to use? (Weiss, 1967) These aspects of speech have been more than a little neglected in the past, but it was essential for our work in the pathology of speech production to know how the human being modifies his respiration for the function of speech (Draper, Ladefoged and Whitteridge, i960; Abercrombie, 1967). The experimental results cannot be given in full, but it is important to discuss the conclusions reached because many of the clinical findings to be reported here depend on them. In brief, if 'Quiet Breathing' is taken as a base-line and we compare the flow rates, timings and lung volume changes found in speech with those of respiration there are well-marked differences. In general, for instance, the average rate of inspiratory flow 1170

Clinical research in speech pathology immediately before a phrase is much greater than that for the corresponding part of the quiet breathing cycle, and this inflow is of shorter duration. The average flow rate during speech is by contrast less, though, on the whole, not much less, than that of the expiratory phase of quiet breathing. On the other hand, if lung volume changes are considered there are interesting contrasts not only between speech and respiration but between different kinds of speech, i.e. text read aloud, and conversational question and answer. One reason may be that the text reader is severely restricted in the phrase divisions that he can make, whereas the spontaneous speaker is not; further study will be necessary to establish how strong is the influence of the various kinds of text. Analysis of the records suggests that the major problem in normal speech production is the maintenance of adequate expiration, not inspiration; as far as possible the speaker keeps his average lung volume near that appropriate to quiet breathing although the actual value at any time will vary up to perhaps 50 to 60 per cent of his Vital Capacity. He may, at other times, reduce his lung volume to 30 or even 20 per cent of his Vital Capacity at the end of a spoken phrase, but it would be unusual, if not abnormal, to find him going below this level (Bonhuys, Proctor and Mead, 1966). Vital Capacity and Functional Reserve Capacity are determined most satisfactorily and accurately by means of some form of Plethysmograph or 'body-barrel' (Menzies, 1790; Mead, i960), but this is too awkward and cumbersome a method to be used routinely and it requires the patient to inhale and exhale maximally. Another method derives lung volume from chest girth measurement at two levels of the thoracic cage (Konno and Mead, 1967; Hixon, Goldman and Mead, 1973), but again the time required would be considerable and, in any case, not all patients would be able to achieve the control of the respiratory system that is essential. The method used in the early stages of our research required the patient to fill his lungs to their fullest extent and then to exhale for as long as possible maintaining a vowel at steady loudness and constant pitch. The patient wore a mask covering nose and mouth so that instantaneous airflow could be measured. Integration of this signal gave the measure of volume and estimates could then be made of the Vital Capacity (Yanigihara, Koike and von Leden, 1968). The physical effort involved in performing this manoeuvre satisfactorily was clearly beyond most of our patients, and the values that were obtained from several attempts varied widely; only in young normal subjects did they seem to bear the expected relationship to lung volume. This procedure, therefore, is seldom used in our clinical investigations now and instead the Vital Capacity and the Functional Reserve Capacity (FRC) level are estimated from the lung volume changes during quiet breathing (Konno and Mead, 1967). This is not an exact procedure but given that the lung volume rise and fall can be calculated within a 10 per cent error then we can see how the speaker 1171

J. K. F. Anthony and I. Malcolm Farquharson succeeds or does not succeed in arranging a supply of air for the production of speech while, at the same time, maintaining adequate respiration. If the average level of air held in the lungs lies above the FRC level then he is drawing on his Inspiratory Reserve Capacity and, if the average level is below, then he is using air from his Expiratory Reserve Capacity. Under normal conditions we could expect that the Average Lung Volume Level in speaking lies somewhat above that for quiet breathing (QB) and it is indeed the case that the ALVL for text (Arthur) and the ALVL for spontaneous question and answer and conversation (Spont) have higher values than ALVL (QB). If the difference were very great, however, it would indicate a form of breathholding in that a large volume of air had been held in the lungs for longer than necessary. On the other hand, if ALVL (Arthur) lay a little below ALVL (QB) that could not be considered abnormal by itself but, if it lay very much below, then some form of hyperventilation would probably betaking place. The Average Lung Volume Level promises in many ways to be a good measure of the ability of the thoracic system to sustain speech, but further investigation is needed with a large number of subjects. The findings given later in this paper show that high positive values are found with the speech disorder of stammeringand low negative values with advanced Parkinson's Disease. We have a much clearer understanding now of how the basic function of respiration is modified for the production of human speech, but there are many basic questions still to be answered. We would like to know, for instance, how much physical effort is required of the human being in producing speech, and, from the clinical point of view, we must try to relate the changes which occur in the thoracic system with age and disease to the reduction in the ability to generate the necessary aerodynamic power. Airflow analyses included in the clinical reports presented here are based on records made using a conventional pneumotach system and a high-speed ink-jet oscillograph; the basic principles were given in the previous paper and no important changes have been made. The Laryngograph, however, as a new and practical method of laryngeal investigation (Fourcin, 1974), should be described in some detail. One of the most difficult factors to obtain from the speech signal has always been the fundamental frequency (generally accepted as 'pitch'). The extraction of the fundamental frequency, which is the frequency of vibration of the vocal cords, from the acoustic waveform at the lips is not usually possible to the accuracy required because of the complex effects of the vocal tract and the rapid articulation changes. Efforts have been made to obtain the vibrational waveform from the surface of the neck directly above the larynx or the trachea but neither of these sites has been found to be free from these acoustic effects. The Laryngograph, because it responds only to the physical movements at the larynx, produces a clean waveform of 1172

Clinical research in speech pathology vocal cord vibration which is ideal for pitch derivation. Small flat electrodes are placed on the skin of the neck above the thyroid cartilage and the mechanical vibration of the cords is sensed as a variation in the electrical impedance of the path across through the larynx. The waveform for a normal larynx in vibration has a well-defined shape and it is the change in this shape with laryngeal malfunction that is of primary interest and importance. The examination procedure

An examination normally commences with a tape recording being made of the patient giving his name, address and age. He is then asked to read a part of the standard phonetically-balanced text (Arthur the Rat) (see Appendix) and, if possible, some relaxed conversation with him is also recorded. The lower track of the tape is always reserved for the laryngograph signal so that, if necessary, the waveform of the vocal cord vibration can be recovered and used for the derivation of fundamental frequency and the intonation. The larynx is then examined by steady illumination or synchronized stroboscopy and the patient's ability to perform normal laryngeal actions is closely studied. The mask incorporating the pneumotach head is then placed over the patient's nose and mouth and airflow oscillograph records are made; first, of respiration under quiet breathing conditions, and, secondly, of the standard text being read again. From these records of what appears to be a fairly well-specified phonetic task we hope to obtain two sets of data: one for short-term aspects of speech such as the average rate of intake of air immediately before each spoken phrase, the average rate of air usage while actually speaking, the rate of speaking and so on, and the other for the long-term, describing how the lung volume varies over a particular period of breathing and speaking. The kind of record obtained is shown in Figure i, and the lay-out is as follows: Trace Function 1 (topmost) Timing signal (50 Hz mains frequency) 2 Chest Girth, an approximation to the circumference of the upper chest—increasing girth is shown as a deflection upwards 3 Expiratory Air Volume, the integration of positive flow (outwards)—each reset represents approximately 100 ml. (millilitres) 4 Airflow in millilitres per second (ml./sec.)—expiratory gives positive upwards deflection 5 Inspiratory Air Volume, the integration of negative flow (inwards)—each reset represents approximately 100 ml. "73

J. K. F. Anthony and I. Malcolm Farquharson 6 7 8

Fundamental frequency of vocal cord vibration (Fo) Laryngograph output (Fx)—vocal cord vibration and gross movement of the larynx Audio—the acoustic pressure waveform from a microphone in front of the mouth.

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The airflow and airvolume oscillograph record provides the raw data for computer analysis and the print-out from the first programme presents a full listing along with various ratios for each inspiratory and expiratory phase, totals and overall averages. The second programme extracts the data for Regression analysis. Parkinson's disease

The deterioration of speech with Parkinson's disease is well-known and follows a general pattern (Allan, 1970). The volume (loudness) decreases steadily with progress of the disease and as phonation and articulation become more and more feeble, intelligibility is reduced almost to zero. The first investigations of this clinic were concerned with the results of stereotaxic surgery on speech production (Farquharson and Anthony, 1969) and, while we feel that this type of treatment (Gillingham, Tsukamoto and Walsh, 1973) will probably provide the most significant information of all on the central control of the organization of speech (Herman et al., 1966), the investigation here is concerned primarily with 1174

Clinical research in speech pathology the assessment of the drug L-dopa. What we are trying to do is to apply what we know about normal articulation and phonation along with our new-found knowledge of lung function to a particular kind of abnormal speech in order to develop quantitative descriptions which can be compared at the various stages of treatment (Mawdsley et at., 1972). One of our patients was 78 years old when first seen and, unfortunately, had already been stabilized on the drug, but he has been chosen for presentation here because of the many interesting features which were found and the many questions that were raised in the analysis of his records. He was examined in the usual way. He was recorded giving his name, address, and age, and then he was asked to read the standard text (Arthur the Rat). His speech when he began though low in volume was understandable, but it gradually became fainter and fainter with less and less articulation until only slight movement of the lips could be seen and nothing could be heard. Correspondingly the Laryngographic record started with normal amplitude for voicing and normal changes for the gross movements of the larynx, but, as the speech deteriorated, voicing stopped and finally all activity ceased. Under stroboscopic light his larynx showed the characteristic bowing of the cords in Parkinson's disease. The vocal cords could not be brought into close contact all along the centre-line. Muscle action appeared hypotonic, and in voicing the vibration movement was slack and the quality produced was hoarse. Airflow records were then made, using the mask with the pneumotachographic system, and one form of subsequent analysis is given in Table I. Here the results are shown for each ratio first as the parameters of a First Order Regression Equation where A is the slope and B is the constant term (r is the Correlation Coefficient and P is the Significance Level) and secondly as simple mean values. The results are presented for three conditions which are, (a) quiet breathing over a period of some minutes, (b) quiet breathing immediately before speaking, and (c) the production of speech. None of the four basic ratios for {a) achieve the statistical significance that had been chosen at that time for normals, although the means are certainly within the normal range. We might conclude then that the figures are misleading and that his respiration was normal under these conditions, but his performance in speaking was far from normal and one would suspect that his respiratory system was partly to blame. In any case, these figures could hardly by themselves describe such a complex function as respiration, and they were not intended to. They simply establish measures of airflow and lung volume which can be used in the comparison between speech and breathing. The dynamic pattern of respiration waveform however cannot be neglected, and when this is looked at in detail (Fig. 2) two abnormal features can "75

J. K. F. Anthony and I. Malcolm Farquharson TABLE I No. I

Name

Ratio

n

VI/TI

12

V2/T2

12

T2/TI

12

1

•49

19

V2/VI

12

0

•58

220

V1/T1

14

81

434

V2/T2

14

288

—100

T2/T1

14

0-28

V2/V1

14

0-76 —87

V1/T1

15

172

471

0-41

V2/T2

15

173

196

0-57

T2/T1

15

V2/VI

15

V2/S\il.

15

Syll./T2

15

A

Map

Visit 1

G. McB. B

r

P°/ ^ . 0

r

Mean

77

368

0

•31

XS

291

80

339

0

•13

XS

239

0 •40

XS

0

•40

XS

0

•36

0-08 0

41

38 •4 4 •25

i-10

2'T5

1 -24

398

0-93

Clinical research in speech pathology.

The Journal of Laryngology and Otology (Founded in 1887 by MORELL MACKENZIE and NORRIS WOLFENDEN) December Clinical research in speech pathology By...
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