5 Puesta en funcionamiento
5.3 Instrucciones para el funcionamiento seguro del aparato – ATEX, IECEx
The contemporaneous decision making (Appendix 28) of the nurses suggested that they had four main areas of concern when implementing the screening tool:
confidence; format; interpretation of terms; too many management options.
Nurses were not confident enough with the BESST to rate people as suitable for soft diet or thickened fluid. This is exemplified by some of their comments:
“It does get quite difficult and you really do have to think quite carefully about it, it‟s not actually very simple really from my point of view”
“...felt a bit better today about doing the test a second time”
Similarly, concerns regarding the format of the tool were expressed:
“Using a new form it can take few times to actually get used to using how it‟s all laid out”
“I‟m also finding the sections A, B, C and D having quite a lot of information in them and can be quite easy to go wrong when following through like A and then going to box C and then A, B, C and D are not clearly standing out initially”
“The middle section does appear to be a little sort of more fiddly especially when you get to the different actions that you are supposed to go to”
Interpretation of the terms used within the form also caused some concern when the form was utilised in clinical practice, despite the lack of concern from the stakeholders in the face validity examination of the screen:
“...was a bit confused about „cough stroke throat clear‟”
“...multiple swallows, I ticked this box because he took two swallows but I still wasn‟t sure whether multiple swallows was three or more swallows”
Having multiple options available appeared to cause further consternation on behalf of the nurses:
“Following actions 1, 2, 3 and 4 is really complicated when you are looking for NADs at various things and whether or not they‟ve got up or down jaw movements it does get quite difficult and you really do have to think quite carefully about it”
7.2 Discussion
This section provides a synopsis of the results from the pilot study. It explores the potential diagnostic accuracy of the BESST compared to the bedside clinical
assessment of the SLT thereby allowing patients to have their swallowing managed within the acute stages of stroke rather than waiting for further specialist assessments by SLT. A larger validation study would facilitate further examination of the advantages and limitations of the BESST when compared to nurses‟ current clinical practice, i.e. using the water swallow screening tool (SSA).
The pilot was integral to the development of the BESST because it highlighted several areas of study methodology and content of the tool that would potentially improve the diagnostic accuracy of the BESST.
7.2.1 Sample group
The pilot aimed to make the sample representative of the range of severity of dysphagia in the acute stroke population by restricting the exclusion criteria, broadening the inclusion criteria and purposeful sampling by the SLT. Other studies, including the GUSS (Trapl et al., 2007), excluded patients who were not medically alert and co-operative and those with cognitive or language difficulties. However, practical considerations regarding time
constraints and recruitment required modification of the approach to sampling to allow for consecutively admitted stroke patients in the validation study.
7.2.2 Sensitivity and specificity
In order to be clinically effective, the BESST needs to be able to accurately identify patients with aspiration (high sensitivity) whilst recognising all those patients who do not present with aspiration (high specificity). The BESST demonstrated excellent sensitivity (100%) with both N1 and N2 when compared to the SLT. The specificity demonstrated by both N1 (44.4%) and N2 (33.3%) was poor. The BESST pilot results do not compare favourably with the specificity of 90% identified in the SSA (Perry, 2001a,b) and that of 69% identified in the GUSS (Trapl et al., 2007). The low specificity may be a result of the nurses being overcautious, placing six patients nil by mouth compared with the SLT rating of normal diet. In this pilot the use of the BESST may have overestimated the number of patients at risk of aspiration.
7.2.3 Changes in methodology
The range of ratings by the different raters demonstrate that the nurses tended to rate the patients as either normal or nil by mouth, tending to rate more patients nil by
mouth. They made limited use of the middle ratings of soft diet and thickened fluid. This tendency to revert to usual clinical practice had consequences when diagnostic
performance of the BESST was tested. It was found to have excellent sensitivity but relatively poor specificity. The conservative approach, by both nurses, led to a high proportion of false negatives, which explained the low specificity of the BESST. Thus, where the nurses were certain that a patient did not have a swallowing problem they were confident enough to rate the patient as able to have a normal diet. However, as soon as a patient‟s response to the BESST suggested some sort of swallowing
problem, the nurses moved swiftly from normal to nil by mouth, despite the presence of a potentially more appropriate management option, e.g. soft diet. Both nurses behaved similarly with the BESST and therefore had good agreement on ratings of normal or nil
by mouth. This meant that the BESST had good intra- and inter-rater reliability when comparing nurses with each other.
In order to address the lack of confidence demonstrated by the nurses in their contemporaneous reasoning for management options in the feasibility study, it was decided to allow the nurses to discuss their findings with the SLT following the completion of the BESST when conducting the main study. The aim was to more accurately reflect the clinical environment and to increase the nurses‟ learning and confidence over time whilst still removing the time constraints of training nurses in dysphagia. This is more reflective of clinical practice in which the BESST would be utilised.
7.2.4 Changes in content of the BESST Format
The pre-screening observations were expanded, offering a continuum of difficulty for each of the pre-screening clinical determinants. Terminology for these expanded determinants was informed by World Health Organisation definitions (WHO, 2009b): unconscious; stuporosed; rousable; and alert. The terminology were coded red, to reinforce termination of the screen, and green, to indicate continuation of the screen, to facilitate completion of the pre-screening stage. The format of the BESST was modified giving a traffic light colour-coding system and clearer „yes‟, „no‟ options for each of the testing materials.
When testing for evidence of clinical determinants for water and thickened water swallows, rather than a tick box, nurses were given a „yes‟, „no‟ option. Screening for 5 ml swallows three times was eliminated from the screening tool because this is accounted for when the patient takes the first three sips of water during the 50 ml swallow screen. The initial trial of thickened water from a teaspoon was eliminated from the BESST because this was subsumed within the 100 ml thickened water trials.
Interpretation of terms
Further clarity was added to the information sheet by defining the continuum of clinical determinants used in the pre-screening stage and the clinical determinants of
aspiration in the oral trials stage. The quantities of thickener for the volume of water required were more clearly defined. Utensils were also specified as changes in the amount of bolus offered would affect the number of multiple swallows identified.
Management options
The BESST provided the nurses with four options. The options of soft diet and
thickened fluids were in addition to standard clinical practice, which would be normal or nil by mouth. The preponderance of normal and nil by mouth ratings meant that few of the ratings took advantage of the additional options. Management options were reduced to: normal diet and fluids, modified diet and fluids and nil by mouth. This offered the nurses one further option to the SSA that still allowed for some oral intake if no clinical signs of aspiration were noted on thickened fluids and puree diet. This is discussed further in the next chapter.
7.3 Conclusion
The results of this pilot study suggest that the BESST is potentially a practical alternative to the SSA. The high sensitivity suggests that it may be useful in the identification of aspiration of thin drinks and thickened puree-consistency oral intake in stroke patients: the use of the screen would not increase the risk to the patient over current clinical practice. The data from the 12 patients in the pilot study suggest that the BESST has no benefit over the SSA in relation to its ability to identify aspiration. At the same time the data do not indicate that using the BESST would put patients at increased risk of aspiration. Further work with the BESST can be considered because it has the potential benefit of offering a modified oral intake option. The contemporaneous reasoning offered by the nurses suggests that only minor changes were required to the BESST in order to improve its use.
A larger validation study was therefore performed to examine the validity (ability to accurately identify dysphagia as present or not), and the utility (suitable for use with stroke population) of the BESST and to ensure that it can be used by the health care professionals who would undertake screening in the clinical setting.
7.4 Summary
The results from this pilot suggested that some modifications to the BESST and its implementation, outlined in the next chapter, may improve its diagnostic performance and reliability.