1 Introduction
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McGrath Mac (Fig. 1): A videolaryngoscope with the LCD screen enabling vari-angle position. It has removable disposable plastic blades of different sizes that match one device and it includes a 250-min battery with a minute-by-minute on-screen.×
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Vividtrac (Fig. 3): The image from the videolaryngoscope is displayed on the connected device such as a laptop or a tablet and for the sake of proper operation vividvision should be used. It is powered through the USB port of the device. It has a track for the endotracheal tube. There is no need to tilt a head during videolaryngoscopy what is perceived as an advantage by the manufacturer. Vividtrac is one size only—adult 3.×
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Cmac Dblade (Fig. 4): The device produced by Storc. It is equipped with an internal rechargeable battery. This videolaryngoscope has buttons to take screenshots. Images are stored in an easily accessible memory card. The manufacturer placed the device in a convenient carrying case protecting it against external influences. The laryngoscope has a one-size blade [8, 9].×
2 Materials and methods
2.1 Mechanical parameters of the devices
2.2 Measurements of endoscopic light intensity
2.3 The optical parameters of the devices
3 Results
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Kingvision: In case of this device one of the disadvantages could be the rigid fixation of the LCD screen and a relatively large cross-section of the device which may bring some difficulties during the difficult intubation in a patient with slight oral dilation. The lack of opportunity to rotate the LCD screen causes that the operator focusing on the correct laryngoscope’s insertion in the mouth cannot see the screen for the first phase of intubation. Only after the insertion of the laryngoscope and passing the patient’s uvula, the angle between the eye of the operator and the screen is reduced so that the operator can effectively evaluate what is seen on the screen. It is also worth mentioning that the power supplied by three AAA batteries is not sufficient for a long-term use.
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McGrath Mac: In our opinion this device is relatively handy. The great advantage is that it has removable, disposable plastic blades, which reduces the risk of scratching the patient’s teeth. The screen provides a relatively wide field of view in the vertical direction. During visualization of the epiglottis, the patient’s uvula is still in the field of view. Unfortunately, due to technical reasons (no external connection to a computer), it was impossible, as in the case of the Kingvision, to take a screenshot. We have tried to take LCD screen’s pictures using a camera, but the interference alters the image so that it is not suitable to be shown in the article. The movable LCD screen is a very useful thing. The operator depending on the existing situation can freely change the angle of the screen. Considering that the power supply is a battery that can only be purchased from the manufacturer because its shape is unique and fits only for this unit, it can be perceived as a disadvantage.
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Vividtrac: From the point of view of the operator, the device is very convenient to use. Comparing to the previous devices, when it is used with a laptop, there is a very large screen. The disadvantage of this device is that a strong flash causes the mucous membranes overexposure. Furthermore, the vividvision program moves hue towards red with the result that sometimes the operator may feel that the mucosa is congested. The drawback of this device was fogging of the camera which was hard to clean and made the videolaryngoscopy difficult to continue. A significant advantage from the educational point of view is the ability to take pictures while using the vividvision program. The device requires no power source. The device is powered by the equipment to which it is connected through the USB interface.
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Cmac D-blade: This device has a well-chosen color balance therefore the operator can see more details in the image. The LCD screen is not in large size, but sufficient to identify all structures of the airways in the field of view. Recording buttons and taking pictures buttons are both in the device’s screen and on the laryngoscope handle what facilitates taking pictures. From the educational point of view, it is a very big advantage because the images are stored in a universal format in the memory card and then can be presented to students in any medium. The handle is ergonomically designed. One size of the laryngoscope blade can be a disadvantage. In our opinion, in terms of powering, it is the best device, because the internal battery can be recharged by line voltage. There is also a unique protective bag attached to the device by the manufacturer which perfectly harmonizes with the device and protects it from any external factors.
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The mechanical parameters of the devices
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The measurement of the intensity of the endoscopic light
McGrath MAC | KingVision | VividTrack VT-A100 | C-MAC 8401 ZX | |
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The distance between the camera and the distal blade tip (mm) | 60 | 34 | 60 | 35 |
McGrath MAC | KingVision | VividTrack VT-A100 | C-MAC 8401 ZX | |
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C mercury (Lx) | 540 | 6800 | 1900 | 8000 |
L incandescent (Lx) | 620 | 6600 | 1880 | 6600 |
F fluorescent (Lx) | 540 | 5500 | 1830 | 7200 |
S daylight (Lx) | 570 | 6000 | 1860 | 7800 |
Lamp type | White led | LED |
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The optical parameters of the devices
Screen type | McGrath MAC | KingVision | VividTrack VT-A100 | C-MAC 8401 ZX |
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Vertical | Horizontal | Horizontal | Horizontal | |
Area observed in the OX axis (mm) | 30 | 34 | 58 | 43 |
Area observed in the OY axis (mm) | 41 | 24 | 28 | 23 |
The virtual image of the OY axis (mm) | 44 | 26 | 45 | 31 |
The viewing angle of the OX axis (°) | 28.1 | 51.8 | 51.6 | 63.1 |
The viewing angle of the OY axis (°) | 40.3 | 40.8 | 41.1 | 47.8 |
Reference to the best result for the OX axis (%) | 44 | 82 | 82 | 100 |
Reference to the best result for the OY axis (%) | 84 | 85 | 86 | 100 |
McGrath MAC | KingVision | VividTrack VT-A100 | C-MAC 8401 ZX | |
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Screen resolution (px) | b.d. | 320 × 240 QVGA | n.d. | 800 × 480 |
Screen technology | LED | OLED | n.d. | LCD |
Size of the screen (inch) | 2.5 | 2.4 | n.d. | 7.0 |
Recording speed (fps) | b.d. | 30 | 30 | 12 |
Camera resolution (px) | b.d. | 640 × 480 VGA | 640 × 480 VGA | 320 × 240 QVGA |
Sensor technology | CMOS | CMOS | CMOS | CMOS |
Pixel density [resolution (px/cm PPCM)] | b.d. | 187 | 109 | 75 |
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The field of view
McGrath MAC | KingVision | VividTrack VT-A100 | C-MAC 8401 ZX | |
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Fare | 26,000 | 8000 | 500 | 29,000 |
4 Discussion
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McGrath Mac: In the literature, there are some reports on the effectiveness of the laryngoscope, both in clinical practice and in the case of young medical students training [10‐12]. There are also some deficiencies of this device mentioned. In Ray’s study [10] it was discovered that students in spite of the noticeable increase of the field of view, had a problem with placing the endotracheal tube in the trachea. The operators did not notice this drawback in our study. Comparing the technical parameters in our study (Table 2) we find that of all comparable devices the McGrath has definitely the weakest endoscopic lamp. Its field of view (Fig. 5) extends in the vertical axis, ensuring good visibility, but the question whether it is needed has to be answered. Seeing the entrance to the larynx, still in accordance with the above, we have patient’s uvula in the field of view. This feature of the device is not negative, but it also does not bring any benefits.
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Kingvision: Searching the literature one can find very few reports concerning the effectiveness of this device in both clinical practice and in the form of training for students. Most of the reports came from Japan [13, 14] They point to the fact that the device is easier to use in the case of difficult intubation than standard Macintosh blades, and that it provides a good field of view. Our research shows that the Kingvision has a very strong endoscopic lamp (Table 2), which definitely brightens the observation area well. Unfortunately this device compared to others, cannot be distinguished by a wide field of view (Fig. 5) or a camera resolution (Table 4). According to the subjective opinions of operators working at least 15 years as anesthesiologists, there is a concern that, in the case of a difficult intubation due to a slight oral dilation, the device will not go through the mouth. Moreover, as previously mentioned, the LCD screen in view of a rigid fixing does not enable full visualization on the early stages of entering the mouth. The operator has to lean over the patient to have an overview of the preliminary stage of a laryngoscope placement in the mouth.
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Vividtrac: While collecting references for this article we have not found extensive research reports indicating the positive effects of the use of this device. The single films demonstrating the efficacy of this device can be found on the manufacturer’s web pages. This device appeared to be very convenient to use according to our practical knowledge. In our opinion, its small size and structure fits very well to supply the patient with a difficult airway. The great possibility is that it can be connected to almost any device with a USB port. This device has an endoscopic lamp with a strong intensity (Table 2) and although it is not the strongest of all comparable devices, sometimes the observed tissues were overexposed when placing too close to the camera (Fig. 12), and also there is a tendency to move hue towards red which promotes the impression of congestion. However, this device has definitely the largest field of view in the horizontal axis. In our opinion, it affects positively the clinical aspects related to the use of this device. From our point of view, the disadvantage is that it is a disposable device, while at the same time due to a possibility of combining with other electronic devices it suits educational purposes well.×
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Cmac: According to the presented literature this device exceeds almost every videolaryngoscopes in the individual rankings. The authors emphasize a shorter duration of intubation, less possibility of complications and high intubation performance indicators [15‐17]. In our study, this device was found to have definitely the strongest endoscopic light (Table 2). It has a camera with the widest viewing angle, which in combination with the largest diagonal size of the display enables the operator to see the details relevant to clinical practice. It also affects the color balance, which is excellent and the images are not overexposed (Fig. 12). In our opinion, this device is very convenient to use and due to the attached protective bag it is suitable for rapid transport and almost immediate use. Owing to an easily accessible memory card which stores the pictures and videos, it is ideal for research and educational purposes. This device wins in almost every test conducted in this study. In the opinion of the operators who had held it in hands, the Cmac is definitely the best device in this comparison. In the literature, there are no data comparing simultaneously four videolaryngoscopes, but in the individual rankings [15‐20] the Cmac is also shown as the best device to manage the difficult airway in wide range of patients.
4.1 Limitations
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A limitation of our study may be the fact that due to a lack of possibility to take a screenshot of the Kingvision and the Mac McGrath on the electronic media, we were not able to compare all the parameters of the other devices. The One size of the laryngoscope blade can be a disadvantage in McGrath MAC videolaryngoscope. Cmac and Kingvision devices have several different sizes of blades for adults and children. The measurement error is also influenced by the fact that the cameras are hidden inside the devices and it was impossible to measure the exact distance between the sensor and the distal blade tip.
5 Conclusions
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In the following statement, the Cmac has better specifications than other devices in almost all examined aspects.
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The Vividtrac is definitely best suited to train students in the context of clinical practice in real-time due to the possibility of transferring the image on the big screen.
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It would be useful to reflect on possible improvements in particular devices that could eliminate the identified limitations in their use. It is worth to lead the next benchmarking and broaden this knowledge.