3 Clinical evidence

3 Clinical evidence

Summary of clinical evidence

3.1 Full details of all clinical outcomes considered by the Committee are available in the assessment report overview.

3.2 The key clinical outcomes presented in the decision problem for the Ambu aScope2 in patients undergoing emergency intubation with difficult airways were:

  • incidence of delayed or failed intubation

  • clinical consequences associated with delayed or failed intubation:

    • death

    • hypoxic brain injury

    • intensive care unit length of stay

    • hospital length of stay

  • incidence of contamination and cross-infection

  • device-related adverse events.

3.3 The clinical evidence for the Ambu aScope2 was based on 11 studies. These comprised 4 published and 2 unpublished randomised controlled trials and 5 published case series reports. Three of the studies evaluated the Ambu aScope2 and 8 evaluated the Ambu aScope, which is the immediate predecessor device.

Patient-based randomised studies

3.4 In a randomised controlled trial, Kristensen (2013) compared the Ambu aScope against a multiple-use fibre optic endoscope in 60 patients with expected normal airways and expected difficult airways. All patients were successfully intubated. The median total intubation time, including the administration of local anaesthetic, was 278 seconds for the Ambu aScope and 234 seconds for the multiple-use endoscope. Although this was statistically significant in favour of the multiple-use fibre scope (p<0.03), the investigators concluded that it was not clinically important because the difference was likely to be less than the hypothesised non-inferiority margin of 120 seconds.

3.5 In a randomised controlled trial Schoettker et al. (2012) compared Ambu aScope2 against a multiple-use fibre optic endoscope in 100 patients with difficult airways (simulated by a semi-rigid cervical collar). The use of the Ambu aScope2 was associated with a longer time to intubation compared with the fibre optic endoscope (69.5 versus 49.5 seconds, mean difference of 20 seconds, p<0.05). Overall, the image quality provided by the Ambu aScope2 was lower than with the fibre optic endoscope although the quality was judged subjectively to be excellent in 24 out of 50 cases and acceptable in another 22 out of the 50 cases. Two attempts were needed in 4 out of 50 cases with the Ambu aScope2 compared against 8 out of 50 for the multiple-use fibre optic endoscopes. There was a 100% intubation success rate in less than 4 minutes for both devices.

Manikin-based studies

3.6 Piepho et al. (2010) conducted a randomised controlled trial that compared the Ambu aScope against a multiple-use fibre optic endoscope by examining the performance of 21 anaesthetists during an easy and a difficult intubation simulation in a manikin. The mean time to intubation for difficult airways was 63 seconds with the Ambu aScope compared against 56 seconds for the comparator (mean difference 7 seconds; 95% confidence interval [CI] −11.66 to 25.66), which was statistically non-significant. In the difficult intubation scenario, the intubation success rate was lower when using the Ambu aScope compared against using the fibre optic endoscope (67% versus 81%, p=0.02), which the authors concluded was mainly caused by the low image quality. Overall the Ambu aScope scored a rating of 'satisfactory' compared against a rating of 'good' for the multiple-use fibre optic endoscope.

3.7 Vijayakumar et al. (2011) conducted a randomised controlled trial that compared the manoeuvrability and ease of use of the Ambu aScope against a multiple-use fibre optic endoscope in manikins set to simulate difficult fibre optic endoscope placement of an endotracheal tube. The mean time to task completion was 63 seconds for the Ambu aScope compared against 53 seconds for the fibre optic endoscope (p=0.08). The estimated 95% CI (1.26 to 18.74) did not overlap with a difference of more than 30 seconds between the Ambu aScope and the multiple-use fibre optic endoscope (which was considered to be a clinically important difference). The mean number of tip surface collisions was slightly higher with the Ambu aScope at 2.7 compared against the fibre optic endoscope at 2.5. The ease of use impression was rated at 65 for the Ambu aScope compared against 77 for the fibre optic endoscope (100 being extremely easy to use).

3.8 A study by Scutt et al. (2011) compared the Ambu aScope against a multiple-use fibre optic endoscope in 2 simulated settings. In the first setting, 22 participants (all who were familiar with, or skilled in, fibre optic intubation) performed paired oral and nasal fibre optic intubations in 3 different airway training manikins (a total of 264 intubations). In the second setting 21 participants intubated 1 airway trainer manikin using 3 supraglottic airway devices: classic and intubating laryngeal mask airways, and i‑gel (a total of 66 intubations). For each intubation the time to intubate was recorded from starting the endoscopy with a preloaded tracheal tube to the first lung ventilation. In both settings, time to intubation was similar between the Ambu aScope and the multiple-use fibre optic endoscope (p=0.18). Use of the Ambu aScope was associated with more reported problems than the multiple-use fibre optic endoscope (32% versus 17% respectively, p=0.04), including difficulties with manipulation, railroading tubes and picture quality. The Ambu aScope was rated a mean score of 7.7 versus 8.5 for the multiple-use endoscope (10 being the highest in terms of ease of use and image quality). In the first setting, 88% of intubations were successful on the initial attempt. In the second setting, there were 4 failures at the first intubation attempt in 126 attempts (3%).

Small case series

3.9 Piepho et al. (2010) described a case series in which the Ambu aScope was used in 5 patients with expected and unexpected difficult airways. Typical landmarks such as the uvula, tongue, epiglottis and larynx were adequately identified in all 5 patients using the Ambu aScope. Intubations via a nasal route were performed in 3 awake patients and advancing the tracheal tube was smooth and easy in these patients. The Ambu aScope was also used in 2 patients via an oral route and in 1 of these patients, airway secretions obstructed vision on the monitor. This was resolved following suctioning and cleaning of the Ambu aScope lens using a sterile swab. Tracheal intubation was successfully achieved in all 5 patients.

3.10 In a case series of 10 patients by Pujol et al. (2010), 9 of 10 intubations with the Ambu aScope were performed and completed without incident. Intubation could not be accomplished in 1 patient. Tube insertion was considered easy in 8 patients, easy but with some manoeuvres needed in 1 patient and impossible in 1 patient. In all 10 patients, a complete view of the glottis was obtained. The image quality was considered adequate in 5 patients and poor in another 5 patients. Fogging of the lens occurred in 6 patients and was cleared easily by gently touching the airway mucosa in 4 patients and by removing the endoscope and cleaning the tip in the other 2 patients. In 2 cases there were secretions that could not be suctioned but they did not result in difficult tube insertion.

3.11 Jamadarkhana et al. (2011) described a case series of 10 patients in whom Ambu aScope2 was used to perform percutaneous dilatational tracheostomy. The average time to set up the endoscope and monitor was less than 5 minutes. The procedure time from needle puncture of the trachea to tracheostomy tube placement ranged from 5 to 10 minutes. All the anaesthetists reported easy handling and manoeuvrability because Ambu aScope2 was light-weight. They scored the clarity and quality of endoscopic view to be between 8 and 10 out of a maximum of 10. No complications were reported during use of the Ambu aScope2.

3.12 In a case series of 10 patients needing a percutaneous tracheostomy, Perbet et al. (2011) found that 7 of the 10 operators rated the Ambu aScope 'very satisfactory', and 3 rated it as 'satisfactory' across all parameters. The presence of the screen was deemed useful in all of the cases.

3.13 Vincent et al. (2011) described a case series of 8 patients with expected difficult airways. All 8 patients were successfully intubated while awake using the Ambu aScope2; 7 by the nasal route and 1 orally. The mean time it took to position the endoscope to visualise the carina was 254.5 seconds, with the shortest time taken being 62 seconds. The mean time for confirming the position of the tube in the trachea after visualising the carina was 51.5 seconds. Of the 8 operators, 6 reported an excellent view of anatomical landmarks, and 2 reported the view as poor, but adequate for intubating the trachea. The mean score for manoeuvrability was 6.8 (range 3–9 with 10 classed as extremely manoeuvrable) and the mean score for usefulness of the endoscope was 7.4 (3–10 with 10 classed as extremely useful).

Unpublished patient-based study

3.14 A study by Lenhardt et al. (2011) has been published as a poster presentation but the Committee considered detailed findings presented as academic-in-confidence data. The randomised controlled trial compared the Ambu aScope against a pre-formed stylet (multiple-use fibre optic endoscope) in 140 patients with expected difficult airways. All patients were successfully intubated and no serious complications were encountered. The time to intubation was similar for the use of the Ambu aScope and a pre-formed rigid stylet (95±63 seconds versus 104±100 seconds, p=0.6). The rating for ease of use was found to be similar for the Ambu aScope and the pre-formed stylet.

Adverse events

3.15 No adverse event reports relating to the Ambu aScope were reported in a search of the US Food and Drug Administration (FDA) Manufacturer and User Facility Device Experience (MAUDE) database. The Medicines and Healthcare products Regulatory Agency (MHRA) has not received any reports of adverse events relating to the Ambu aScope2.

Committee considerations

3.16 The Committee noted that the clinical evidence was from studies in manikins or patients with expected (or simulated) difficult airways. There were no controlled trials in patients with unexpected difficult airways but the Committee recognised the considerable difficulties of conducting such studies.

3.17 The Committee judged that the studies provided evidence that the Ambu aScope2 was an acceptable alternative to multiple-use fibre optic endoscopes. In addition, the Committee received expert advice that although the Ambu aScope2 has poorer image quality than standard multiple-use fibre optic endoscopes and its lens needs cleaning during use, it is an acceptable alternative in situations in which a multiple-use fibre optic endoscope is not available.

3.18 The Committee noted that in the studies in which manikins were used, the anaesthetists had previous experience of using standard multiple-use fibre optic endoscopes, but lacked experience of using the Ambu aScope. Therefore, the longer time to intubation observed for the Ambu aScope might have been influenced by the anaesthetists' lack of experience in using the device.

3.19 The Committee was mindful that potential consequences of failed intubation include severe brain injury and death. It accepted that the immediate availability of the Ambu aScope2 in situations where multiple-use fibre optic endoscopes are not available may lower the risk of these consequences occurring. The Committee noted that clinical evidence on these outcomes was not available.

3.20 The Committee considered the fact that the Ambu aScope (the predecessor of the Ambu aScope2) was used in 8 of the 11 studies presented. It judged that the data derived from these studies were relevant and valid for this submission because the Ambu aScope2 has the same mode of action and design as the Ambu aScope, but with certain modifications which were likely to improve, rather than impair, its performance.

  • National Institute for Health and Care Excellence (NICE)