Учебники / Evaluating Voice Therapy - Measuring the Effectiveness of Treatment Carding 2000

two different therapy approaches: ‘confidential voice therapy’ and ‘resonant voice therapy’. All patients received instruction in general vocal hygiene before being assigned to their treatment group. ‘Confidential voice therapy’ focuses on the elicitation of a minimal inten­ sity, low effort and slightly breathy mode of phonation in speaking confi­ dentially at close range. ‘Confidential voice therapy’ is considered to be particularly useful during the initial stages of treatment for maximum early reduction of vocal fold lesions as a result of habitual hyperfunc­ tional voice use. ‘Resonant therapy’ involves vibratory sensations on the alveolar ridge and other facial areas during phonation. These sensations are thought to arise from a relative acoustic tuning of the supraglottal cavities with the glottal source spectrum (Verdolini-Marston et al., 1995).

Prosek et al. (1978) and Stemple et al. (1980) both describe the use of electromyographic (EMG) biofeedback in the treatment of patients with hyperfunctional voice disorders. The first study used a noise gener­ ator to alert the patient to excessive muscle tension. This enabled the patient to have simultaneous biofeedback during phonation tasks. The second study used a more latent biofeedback device, which calculated a general muscle-tension score of the laryngeal area after the speaking of phonetically balanced vocal tasks. Both techniques demonstrated that patients could voluntarily reduce the degree of laryngeal muscle tension when aided by the EMG biofeedback devices.

Yamaguchi et al. (1993) evaluated a ‘pushing exercise programme’ to correct for functional glottal incompetence. The pushing method is a voice therapy technique designed to reduce glottal inefficiency by increasing glottal closure. This method uses the principle that, in order to build up thoracic pressure, it is necessary to close the larynx. Thus, the technique takes advantage of the synchronous responsive adduction of the vocal folds when the neck and the upper arms are consciously strained in any manner that requires intrathoracic pressure build-up. The preliminary results demonstrated improvements in the three patients reported on.

Roy and Leeper (1991) measured the effects of a manual reduction technique for laryngeal musculoskeletal tension as a treatment of functional voice disorder. This treatment approach involved ‘kneading the laryngeal musculature and lowering the position of the larynx in the neck ‘ (page 243). The technique includes encircling the hyoid bone with the thumb and middle finger, and exerting light pressure in a circular motion. A similar procedure is repeated in the thyrohyoid space and over the superior borders of the thyroid cartilage. Seventeen ‘functional dysphonia’ patients were treated using this approach.

Fex et al. (1994) studied 10 functional dysphonia patients treated with voice therapy using the ‘accent method’ (Bergendal-Fex, 1976).

This method focuses on developing a relaxed body position, abdominal breathing and a natural optimal pitch. Sustained phonation with varia­ tions in loudness (accents) is used, demonstrated first by the therapist and then copied by the patient.

In other studies, the authors have described in detail the assessment and measurement of dysphonic patients, but have not included the description of the voice therapy treatment programme. Davis (1977) analysed a range of acoustic features in a patient receiving voice therapy after surgical removal of undifferentiated vocal fold oedema. Davis used acoustic measurements to monitor progress throughout the treatment programme, and to demonstrate the successful outcome of therapy. However, details of the treatment programme were not given. Schneider (1993) described a range of perceptual and instrumental techniques to track voice change in a 27-year-old woman with ‘hyperfunctional dysphonia’. The intensive vocal hygiene therapy programme was not described at all. Hayward and Simmons (1982) evaluated the use of group relaxation therapy in the treatment of 33 dysphonia patients. Each group’s therapeutic direction varied according to the needs of the individuals within that group. They did not document the treatment programme of each member of each group individually.

The literature demonstrates that there are many different voice therapy techniques for the treatment of dysphonia patients. The voice therapist selects a treatment programme that reflects their perception of the cause of the problem and that is appropriate to the needs and expec­ tations of the individual. This point is illustrated in the description of voice therapy for 17 patients with vocal fold granuloma (Bloch et al., 1981). The authors stated that their voice therapy methods ‘varied according to each patient’s needs’ (page 49). They described a general regimen of voice treatment, but were keen to point out that some aspects were more pertinent to some patients than to others. ‘When there was evidence of excessive hard glottal attack, the patient was made aware of this in an effort to eliminate them’ (page 49). Most clinicians combine a variety of therapy techniques in order to find the most suitable approach for any individual patient (Boone and McFarlane, 1988). This means that, in a group study, the therapy programme may not be identical for each patient. In such a situation it is important to document the intervention for each patient.

Defining what ‘effectiveness’ means

‘Effectiveness’ is a difficult term to define. The interpretation of its mean­ ing influences the design of the study, the definition of the independent and dependent variables, and the choice of outcome measures. There is a

discussion of the difference between ‘efficacy’ and ‘effectiveness’ in Chapter 1. However, a definition of ‘effectiveness’ should incorporate a number of issues: first, treatment effectiveness should be linked to the goals of the intervention; second, measurement of effectiveness should be multi-dimensional and as comprehensive as possible; finally, studies about treatment effectiveness should be concerned with the investigation of the benefits of intervention in a clinically relevant setting. These points are all discussed further below.

Goal-specific effectiveness

Treatment can be said to be effective if it reaches the goals that it set out to attain. An important stage in defining ‘effective’ treatment is therefore to define the specific goal(s) of the therapy against which the actual outcome can be judged. The clearer the therapy goals, the easier it is to determine whether or not these goals have been achieved. The clearer the goals, the easier it is to decide on the outcome measures. A study that does not state the goals of treatment cannot be clear about what the outcome measures are. This, of course, allows the authors to select the outcome measures that show a significant change after therapy and discard those that do not. This is termed a ‘false-positive’ response.

Some studies state clearly the criteria on which the success of treat­ ment will be judged. For example, Bloch et al. (1981) stated that successful voice therapy for patients with contact granuloma was when the laryngologist judged that there was complete disappearance of the vocal fold lesion, when the speech and language therapist judged that full voice recovery and normal manner of phonation had occurred, and when the patient judged himor herself to be completely free of symptoms. Studies that examine treatment of patients with discrete laryngeal pathology caused by voice abuse/misuse or habitual vocal hyperfunction have an in-built success criterion. Effective treatment should result in elimination of or at least significant reduction in the size of the lesion. This may explain the disproportionate number of studies that have examined the efficacy of treatment for vocal nodules. With less definite laryngeal diagnosis (i.e. ‘glottal incompetence’ – Yamaguchi et al., 1993 – or ‘non-organic dysphonia’ – Carding et al., 1999), the situa­ tion is much less clear. In these studies, it may not be possible to document any physical changes in the larynx and so effectiveness must be judged against specific treatment aims.

Comprehensive effectiveness

Effectiveness can mean different things to different people. A study that considers effectiveness from one perspective only may be considered lim­ ited or even potentially biased. There are several examples of efficacy

specific acoustic parameters and perceptual voice quality parameters. Measures of voice therapy effectiveness that incorporate a number of related measures are likely to produce results that are more comprehen­ sive, more valid and more convincing.

Clinically relevant effectiveness

Conture and Wolk (1990) suggest that voice therapy effectiveness is closely related to whether or not it was ‘successful’ for the patient. If a patient presents with a number of voice symptoms that are subsequently resolved or significantly improved, the therapy may be seen to have been effective. In this case, the criteria for measuring treatment efficacy are related to outcomes for the patient, i.e. how their voice sounds or func­ tions. Several research studies in speech and language therapy have stressed the importance of examining successful outcomes of therapy in terms of the overall impact on the client (Kluppel-Vetter, 1985; Bain and Dollaghan, 1991; Enderby, 1992). Many medical and health-related pro­ fessions are now developing patient-centred efficacy measurements as opposed to clinician-based criteria (Finlay et al., 1992; Aharony and Strasser, 1993; Gupta et al., 1993; Boston, 1994; Jacobson et al., 1999).

The potential discrepancy between what is being measured and what is actually important to the patient is addressed in the concept of ‘clinically significant change’. Bain and Dollaghan (1991) defined effec­ tive treatment as ‘treatment resulting in clinically significant improve­ ment in the client’s performance’ [my italics]. This is not synonymous with statistically significant improvement. A measured improvement that is statistically significant may be of little consequence to the client if he or she still complains of the same problem. Similarly, the client may report significant improvement in his or her condition, which cannot be measured by the techniques chosen. Clinical significance is concerned with the overall impact of the level of change for the patient. Assessments of the overall impact of a change are likely to be based on such factors as the importance assigned to the aspect that has changed (relative to other aspects) and the extent to which the change is believed to be a prerequisite to subsequent successful functioning by the patient. A related aspect of overall impact of the change concerns the effect of the change on other areas of the patient’s functioning. The treatment effects that impact on the patient’s ability to function (i.e. enabling the patient to participate in social functions, enabling the patient to return to work, etc.) are likely to be viewed as more clinically significant than the effects that are limited to one aspect of a patient’s voice problem (e.g. levels of acoustic noise in the speech signal).

Chapter 4

Techniques for measuring change in voice over time

Choosing appropriate outcome measures is crucial in the design of a good efficacy study. The wrong and inappropriate choice of outcome measures can invalidate an otherwise well-designed study. Outcomes are multidimensional. Olswang (1998) observes that outcomes are only defined in terms of the agent. Thus, the outcomes can be:

•clinically derived, i.e. clinical measures such as maximum phona­ tion time, ability to sustain phonation, etc.

•functional, i.e. ability to use the telephone, ability to resume teaching job, etc.

•administrative, i.e. number of times seen, client referral patterns, etc.

•financial, i.e. cost of treatment programme

•client defined, i.e. perceived improvement in quality of life.

As we are concerned in this book with effectiveness and not efficiency, we can limit ourselves to considering outcomes that are clinical, functional and patient-centred. Enderby (1992) states that outcome measures are too often related to only one aspect of care, leading to the false impressions of treatment effectiveness. Yet we are still left with a difficult situation with regard to which measurement techniques to choose. There are no established voice outcome packages available and no clear procedures to aid appropriate selection. Furthermore, there are a large number of voice assessment techniques to choose from. Hirano (1989) identified over 50 techniques that were being used for the evaluation of the human voice throughout the world. These techniques can be divided into six broad categories.

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