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between different levels of hyposmia (Tsukatani, Reiter et al. 2005). For these reasons, a combination of tests is usually applied (see a.o. Van Dam et al. (Van Dam, Hilgers et al. 1999)).\u000D5.3.4.2 Recovery of olfactory function after laryngectomy\u000DTwo methods are commonly used for restoring the sense of smell after a laryngectomy: using aids or acquiring a new technique. Several aids are available to reproduce nasal airflow after a total laryngectomy. With these aids the sense of smell (if normal pre-operatively) can be carefully measured and monitored (Tatchell, Lerman et al. 1985, Schwartz, Mozell et al. 1987, Tatchell, Lerman et al. 1989). The aid most commonly used for this is the so-called larynx bypass. This involves the use of a flexible tube connecting the mouth with the stoma, so that the patient may relatively easily create nasal airflow by breathing through the nose and via the mouth (Schwartz, Mozell et al. 1987). Research shows that laryngectomees are able to recover their sense of smell with the help of this aid (Tatchell, Lerman et al. 1985). However, the larynx bypass is of little use in everyday life. It is only suitable as a diagnostic and not as a therapeutic aid. A study by Lennie et al. showed that, despite the availability of these aids and the incorporation of \u2018behavioural treatment\u2019 in the rehabilitation of laryngectomees, restoring the sense of smell receives little emphasis (Lennie, Christman et al. 2001). A mere 9% of patients received instructions on smelling technique. The explanation given for this was the lack of clarity surrounding the feasibility and effectiveness of the available aids.\u000D5.3.4.3 Efficacy of olfactory rehabilitation after laryngectomy\u000DThe growing awareness of the possibility of recovering the sense of smell was shown by research performed at the Dutch Cancer Institute-Antoni van Leeuwenhoek (NKI-AVL). It was found in this study that patients who were able to smell after a laryngectomy (approximately a third of the study population) showed more muscle activity in the face and the neck than patients who could not smell (Van Dam, Hilgers et al. 1999). This observation led to the development of the so-called \u2018Nasal Airflow Inducing Manoeuvre\u2019 (NAIM), which allows the patient to induce a controlled (active) nasal airflow. The NAIM was first described by Hilgers et al. and is also referred to as the \u201Cpolite yawning technique\u201D (Hilgers, Van Dam et al. 2000, Van der Molen, Kornman et al. 2013). The NAIM involves the rapid and repeated movement of the jaw, floor of the mouth, tongue and soft palate, while the lips remain closed. This causes negative pressure in the oral cavity and oropharynx, allowing the air to be induced via the olfactory epithelium. For the training of patients in this technique a water manometer is used, which is connected to the nose and thereby visualises the nasal airflow. The direct visual feedback has been found to be useful in improving and refining the technique.\u000DIt was assessed in an intervention study whether the sense of smell of laryngectomees could be rehabilitated with the help of this manoeuvre. 89% of the patients could be taught the NAIM in under thirty minutes. The percentage of smelling patients increased from 25% before the intervention to 57% after. This study shows that it is indeed possible to restore olfaction in a large number of laryngectomees by using this method. It was also found that patients who could already smell through their own, often unconsciously acquired, technique improved their sense of smell by learning the NAIM, because they were now able to perform the technique on demand.\u000DA follow-up study by Hilgers et al. showed that extended and more intensive practice was needed to implement the smelling manoeuvre in all facets of everyday life (Hilgers, Jansen et al. 2002). The patient must become aware that \u2018passive\u2019 olfaction is no longer possible and that they should always use the \u2018active\u2019 NAIM method to be able to smell. Via a transfer process from unconscious\u000D114\u000D