Discussion
With the incidence rate of laryngeal cancer increasing year by year in China,15 more and more patients undergo partial laryngectomy.5 After partial laryngectomy, the structure、local nerve、muscle and coordination function of larynx and pharynx are affected, resulting in dysphagia.16 The most serious dysphagia occurs weeks after the surgery, and most patients could get different degrees of improvement through oral intake training, but the remaining problems of swallowing would affect the long-term life of patients, such as repeated pneumonias, change of eating habits and reducing or even refusing of social intercourse.2Therefore, it is imperative to evaluate and rehabilitate the swallowing abilities of the patients after partial laryngectomy, especially in early postoperatively period.5
VFSS is the gold standard for swallowing examinations.4, 7, 17 Traditional VFSS usually uses barium as contrast agent that has some drawbacks. Once the barium is aspirated into the trachea and lung, it will be difficult to remove and absorb, and may cause damages of the lung function. Ioiohexol solution is a non-ionic contrast agent, which has the advantages of high-water solubility, low viscosity, low osmotic pressure and low toxicity.18 Therefore, we improved VFSS using Iohexol Injection to instead of barium.
However, VFSS also has some disadvantages and it is necessary to develop new evaluation tools. So far, almost all swallowing assessment tools require patients to swallow liquid food directly,19while ignoring the swallowing ability of food of other characteristics.20, 21 GUSS chose three kinds of food to complete the test sequentially, but the evaluation sequence was not suitable for patients with partial laryngectomy. This was based on the following observation: the risk of aspiration of swallowing solid food was lower than that of swallowing semisolid food, and the risk of aspiration of swallowing semisolid food was lower than that of swallowing liquid food. Therefore, we modified the sequence of food trails to minimize the risk of aspiration during the examination and to identify patients who could intake solid, semi-solid or liquid food respectively. This point is important because it guides the rehabilitation.
In our research, we classified modified GUSS into 4 grades according to the severity rating of GUSS, and corresponded to 4 grades of risks of aspiration. The benefit was that both dysphagia and aspiration were evaluated at the same time. And we reported that the severity rating and grades of risks of aspiration assessed by modified GUSS were excellent consistent by comparing with VFSS. It indicated that modified GUSS could distinguish patients suffering from dysphagia with varying degrees of risks of aspiration and even recommend food of different characteristics. Although the recommendations were not drafted by us, they must be dissimilar to those of GUSS because of the modified sequence.
Moreover, we demonstrated that modified GUSS had substantial to excellent interrater reliability for all classification categories. The predictive values were also acceptable. For the chosen no dysphagia grade, it had 100.0% sensitivity and 100.0% specificity VFSS; for the chosen moderate and severe dysphagia grade, it had 90.0% sensitivity and 100.0% specificity; for the chosen severe dysphagia grade, it had 84.2% sensitivity and 100.0% specificity. The all 100.0% specificities meant extremely low misdiagnosis rates, and the high sensitivities meant very low missed diagnosis rates. However, the results revealed that some patients with severe or moderated dysphagia were graded with a lower severity degree, and also indicated that these patients were particularly difficult to swallow semi-solid food and liquid food, while relatively easy to swallowing solid food. In order to adjust this result and identify the false negative patients, daily evaluation by modified GUSS was recommended.
In addition, we revealed that the higher the modified GUSS scores, the less the days from oral feeding to gastric tube extubation. Although we did not set objective criteria for removing the gastric tube, just based on the subjective assessment of the patients by the doctors, we confirmed that the modified GUSS scores could predict the time to remove the gastric tube generally.
In summary, on the basis of GUSS, we introduced a bedside evaluation tool that had good reliability and validity for assessment of swallowing function and risks of aspiration before oral feeding in early period after partial laryngectomy. However, there is still a lot of work to be done according to modified GUSS, such as swallowing rehabilitations、food recommendations、long term evaluation effectiveness and standards for gastric tube extubation.