Continuous Laryngoscopy Exercise (CLE) Test for Exercise Inducible Laryngeal Obstruction (EILO)
Exercise Inducible Laryngeal Obstruction (EILO) is a condition where the larynx appears normal at rest, but during high volume ventilation induced by ongoing exercise, people experience inappropriate inspiratory laryngeal adduction (closure), leading to airflow obstruction and breathing problems. Assessment during exercise is therefore necessary. A variety of diagnostic methods have been applied over the years to diagnose EILO; however, continuous visualisation of the larynx by laryngoscopy during a high-intensity exercise test (continuous laryngoscopy during exercise, or continuous laryngoscope exercise ‘CLE’) is widely acknowledged as the ‘gold standard’.
This test involves real-time visualisation of the larynx throughout a complete exercise session as it unfolds from rest to exhaustion, or to the onset of intolerable symptoms. The setup offers important insights into the severity of the condition, as well as identification of the specific structures within the larynx responsible for the obstruction, including details of the development and timing of the pathological laryngeal response. The CLE test has helped establish that EILO often arises from supraglottic (i.e., aryepiglottic fold) obstruction, and that this is followed by a glottic fold adduction (i.e., vocal cord) in most cases, whereas pure glottic obstruction is less common.
Step-by-step guide on how to perform a CLE test
1. Preparation
- Administer an adrenergic agonist in the nostril.
- Apply local anaesthesia (Lidocaine) to the nasal cavity 10 minutes before the test
2. Laryngoscope
- Utilise a flexible fiber-optic laryngoscope with the smallest possible diameter. The level of discomfort increases with the diameter, which should preferably be kept below 3.5 mm.
- Introduce the laryngoscope through the “most open nostril”, and advance the tip into the pharyngeal space until a clear view of the larynx is achieved.
- If integrating the CLE test with a cardiopulmonary exercise test (CPET), it is recommended to use a modified facemask with a pre-made hole for introducing the laryngoscope. If this is not the intended approach, securing the laryngoscope can be achieved using medical tape.
- To retrospectively evaluate the test and document the findings, it is advisable to connect the endoscope to a video camera system for recording. Store the recording securely as part of the patient’s charts.
3. Preventing Equipment Displacement
- Best possible stability of the equipment is achieved if the laryngoscope is secured with tape to a mask (or alternatively to the nose) in a position ensuring a clear view of the laryngeal entrance, including supraglottic structures and vocal folds.
- Further, best stability is achieved if the handle of the laryngoscope is secured to a custom-made headgear. If ergometer cycling is used, the laryngoscope may simply be hand-held if headgear is not available.
4. Exercise Test
- Conduct exercise to complete exhaustion or intolerable symptoms.
- The optimal approach to evaluate a patient’s symptoms is to employ the mode of exercise in which the patient reports symptoms occurring. However, this may pose challenges in a laboratory setting, both technically and in terms of time constraints.
- Ideally, the mode and the intensity of the exercise should be tailored to the individual patient, based on triggers identified from their medical history.
- Treadmill running, ergometer cycling, rowing, swimming or stair climbing have all been used in a diagnostic setting to reproduce real-life symptoms of EILO.
- For most young people, treadmill exercise is preferable to cycling when the goal is to achieve the highest possible ventilation.
- Research and follow-up on progress after treatment interventions require a carefully planned approach to standardizing the exercise tests in the laboratory, ensuring exercise to complete exhaustion or intolerable symptoms.
5. Exercise Test in Combination with a Cardiopulmonary Exercise Test (CPET)
- While not essential for diagnosing EILO, a combined CLE and CPET allows for simultaneous assessment of maximal oxygen uptake, cardiac performance, and other potential causes or co-morbidities of exertional dyspnoea, which may present with similar symptoms.
- Performing CPET with a CLE set-up, therefore, facilitates simultaneous evaluation of other potential causes of exertional dyspnoea.
- CPET data obtained from a CLE setting have been shown to be comparable to data obtained from a standard CPET.
- Currently, the diagnostic value of routine CPET data for diagnosing EILO is limited.
6. Recordings
- The laryngeal obstruction should be evaluated directly during the test, but it is also highly recommended to store the video recordings of the test-session.
- Video recordings allow for detailed evaluation including in slow-motion, and for later diagnostic considerations and validation, and for future comparisons with baseline after therapeutic interventions.
- Simultaneously recording of the upper body and breath sounds is preferred for a more accurate diagnose, and for evaluation and verification of symptoms.
7. Evaluation
- Score laryngeal movements in a systematic way and at specified exercise intensities using a predefined scoring system.
- Assess glottic and supraglottic levels separately and address the timing of any potential events.
- Ideally, two experienced raters should be involved in the visual scoring.
- For research, we recommend that two experienced raters independently evaluate the video recordings blinded, and disagreements to be resolved through consensus.
8. CLE scoring
- The most commonly used scoring system for EILO today is the semi-ordinal categorical scale called CLE-score (Maat et al., 2009).
- The CLE score assesses the relative degree of inspiratory adduction of the supraglottic and vocal folds during increasing exercise.
- Laryngeal obstruction should be evaluated on both glottic or supraglottic level at moderate and maximum exercise, and rated from 0 to 3 at each level, giving a score ranging from 0 to 12 (CLE score).
- A score of 0-1 on both the glottic and supraglottic levels is considered normal and typically a score of 2 or more is considered abnormal.
- However, it’s important to note that determining cut-off levels for distinguishing between normal and abnormal laryngeal responses to exercise is an area that requires further research.
- A supraglottic score of 2 has been described in individuals with no perception of respiratory problems, so this might be considered normal.
- Glottic and supraglottic scores of 1 have been observed in patients with inspiratory respiratory problems. This is a diagnostically challenging situation. Expert input should be obtained on interpretation and the differential diagnosis should be revisited. Possibilities include EILO which did not meet criteria during testing, and breathing pattern dysfunction.
- CLE scores rests on judgements made by raters, meaning there is an aspect of subjectivity involved.
- Experience is a key factor that influences the repeatability of the rater.
- Despite subjectivity in judgments, CLE is the most objective measure of EILO severity, and it is regularly used in everyday clinic worldwide.
9. Recording of symptoms and signs
- The test leader should assess and record the symptom presentation, the breath sounds, and the overall appearance of the patient during the test.
- The assessment should also include recording of the patient’s subjective experience, including their identification of symptoms as the breathing issues for which they sought medical assistance.
10. Diagnosis and biofeedback
- The CLE-test not only aids in diagnosing EILO, but also offers valuable insights for therapeutic interventions and biofeedback.
- Biofeedback, achieved by keeping the laryngoscope in place after the test to illustrate laryngeal responses during various breathing exercises, serves valuable therapeutic purposes.