WO2017005768A1

WO2017005768A1 - Insertion tube for flexible bronchoscope

Info

Publication number: WO2017005768A1
Application number: PCT/EP2016/065916
Authority: WO
Inventors: Antoine GUILLON
Original assignee: INSERM (Institut National de la Santé et de la Recherche Médicale); Universite De Tours Francois Rabelais; Chru De Tours
Priority date: 2015-07-06
Filing date: 2016-07-06
Publication date: 2017-01-12
Also published as: FR3038507A1; BE1023973A1; BE1023973B1

Abstract

The invention relates to an insertion tube (12) for a flexible bronchoscope (1) for use during intensive care procedures, comprising a proximal portion (121), a distal portion (122), a camera docking terminal (124) at the distal end of the distal portion (122) and at least one connecting and transmitting wire (125) running from the camera docking terminal (124), along the insertion tube (12) up to the proximal end of the proximal portion (121); each of the proximal and distal portions (121, 122) having an inner diameter of at least 2 mm, preferably of at least 2.1 mm, forming a suction channel and an outer diameter; wherein the outer diameter of the proximal portion (121) is at most 4 mm, the length of the proximal portion (121) being at least 20 cm, preferably at least 25 cm, preferably at least 30 cm, preferably at least 35 cm. The invention also relates to a flexible bronchoscope (1) comprising such an insertion tube (12), a method for selecting an insertion tube for the flexible bronchoscope and a method for using the flexible bronchoscope.

Description

INSERTION TUBE FOR FLEXIBLE BRONCHOSCOPE

Technical field of the invention The present invention relates to the technical field of bronchoscopy and tools for carrying out bronchoscopy. More particularly, the present invention relates to the technical field of bronchoscope, especially flexible bronchoscope for use during intensive care procedures involving an endotracheal tube and its components.

The invention also relates to methods for selecting an insertion tube for the bronchoscope and for using the bronchoscope.

Prior art

Flexible bronchoscopes belong to the mandatory tools in intensive care units. They are essential for optimal management of (mechanically) ventilated patients, and are used for both diagnostic and therapeutic purposes. They comprise a suction channel for removing secretion produced inside the lung and optical fibres that guide light into and from the operation site.

Bronchoscopy in ventilated patients, i.e. patients who can breathe normally without artificial assistance, is generally safe and does not present any particular technical problem [Lindholm CE, Turner, Terzi, 1-3].

However, when patients cannot breathe on their own, intensive care procedure must be taken and intubation is needed to provide the patient with mechanical ventilation: air (or another gas mix) is introduced into the lungs of the patient in positive pressure through an endotracheal tube. When intubating the patient, the size of the endotracheal tube, i.e. length and diameter, is usually selected according to the patient's morphology and not with the aim to be able to insert a flexible bronchoscope if needed later. Indeed, not all patients received in intensive care unit will need a bronchoscopy and for patients intubated over a long period of time, endotracheal tubes with dimensions adapted to their morphology are less invasive and as such minimise medical complications. In some instances, bronchoscopy is needed in these mechanically ventilated patients, notably when secretion fills their lung. In order to extract the secretion, flexible bronchoscopes present a suction channel.

Now, bronchoscopy during intensive care procedures is more delicate since it involves inserting the flexible bronchoscope through the endotracheal tube with which the patient is intubated. As such, the bronchoscope can significantly affect ventilation because it partially obstructs the passage of gas flow through the endotracheal tube and increases resistance inside the endotracheal tube and the lungs, thereby limiting inspiratory and expiratory flow [Lawson RW, 4], thus leading to life-threatening situations, in particular, since the rapid decrease of expiratory flow results in trapped volume of air within the lung and may eventually lead to pneumothorax [Nay MA, 5]. Indeed, cases of pneumothorax were reported in both major observational studies examining the safety of bronchoalveolar lavage performed with flexible bronchoscope in mechanically ventilated patients [Turner, Steinberg 2, 6] .

Further, bronchoscopy can be particularly challenging in patients with acute respiratory distress syndrome (ARDS): the occurrence of pneumothorax in mechanically ventilated patients with ARDS is about 6.5-12% [Anzuetto, Gamon 7, 8]. Patients with ARDS require lung-protective ventilation strategies to avoid ventilator- induced lung injury [Molooney 9] .

To make fibre-optic bronchoscopy safer for intubated patients, narrower bronchoscopes have been developed [Diaz Fuentes, 10]. However, the reduction in width of the existing bronchoscopes involves the reduction in width of the suction channel due to the presence of optical fibres within the walls of the flexible bronchoscopes. Optical fibres are needed for visualisation of the operation site within the body of the patient. The presence of optical fibres makes it impossible to thin the walls.

Now, as indicated above, intubated patients have thick secretions that need to be removed from the lung. Narrower suction channel makes it practically impossible to remove secretions or to perform bronchoalveolar lavage.

Therefore, the existing solutions are not satisfactory and there is still a need for an improved flexible bronchoscope. Summary of the invention

One objective of the invention is thus to overcome at least one drawbacks of the prior art. More in particular, one objective of the invention is to provide a flexible bronchoscope that enables both use with an endotracheal tube and sufficient suction capacity.

To this aim, the present invention provides an insertion tube for a flexible bronchoscope for use during intensive care procedure involving an endotracheal tube, comprising a proximal portion, a distal portion, a camera docking terminal at the distal end of the distal portion and at least one connecting and transmitting wire running from the camera docking terminal, along the insertion tube up to the proximal end of the proximal portion;

each of the proximal and distal portions having an inner diameter of at least 2 mm, preferably of at least 2.1 mm, forming a suction channel and an outer diameter;

wherein the outer diameter of the proximal portion is at most 5 mm, preferably at most 4,6 mm, preferably at most 4 mm, the length of the proximal portion being at least 20 cm, preferably at least 25 cm, preferably at least 30 cm, preferably at least 35 cm.

The present invention also provides an insertion tube for a flexible bronchoscope for use during intensive care procedure involving an endotracheal tube having a lumen cross section and a length,

the insertion tube comprising a proximal portion to remain inside the endotracheal tube, a distal portion to extend outside the endotracheal tube, a camera docking terminal at the distal end of the distal portion and a connecting and transmitting wire running from the camera docking terminal, along the insertion tube up to the proximal end of the proximal portion;

each of the proximal and distal portions having an inner diameter of at least 2 mm, preferably of at least 2.1 mm, forming a suction channel and an outer diameter, the outer diameter of the proximal portion being at most 5 mm, preferably at most 4 mm;

wherein the proximal portion has an outer cross section selected so that the area difference between the lumen cross section of the endotracheal tube and the outer cross section is at least 20 mm², preferably at least 23 mm², preferably at least 29 mm²;

wherein the proximal portion is longer than the length of the endotracheal tube. The invention also provides an insertion tube for a flexible bronchoscope for use during intensive care procedure, comprising a proximal portion, a distal portion, and a camera docking terminal at the distal end of the distal portion and a connecting wire running from the camera docking terminal, along the insertion tube up to the proximal end of the proximal portion;

wherein the outer diameter of the proximal portion is 4 mm, the length of the proximal portion being at least 30 cm.

Such insertion tubes ensure that the cross-section of the air passage between the endotracheal tube and the insertion tube is sufficient for ventilating the intubated patient with minimised risk and at the same time enables effective extraction of secretion from within the lung of the patient, also at a minimised risk.

In one embodiment of any of the insertion tube above, the distal portion has an outer cross section wider than the outer cross section of the proximal portion.

Additionally or alternatively, the insertion tube further comprises a light source docking terminal at the distal end of the distal portion.

The insertion tube described above is used as a component of a flexible bronchoscope for use during intensive care procedures. This flexible bronchoscope advantageously further comprises a camera permanently docket to or releasably dockable to the camera docking terminal. This flexible bronchoscope advantageously further comprises a light source permanently docked to or releasably dockable to the light source docking terminal when the insertion tube is provided with such a terminal. This flexible bronchoscope advantageously further comprises_a handle with a bending control, the handle being permanently connected to or releasably connectable to the proximal end of the proximal portion of the insertion tube.

In another aspect of the present invention, a method for selecting an insertion tube for a flexible bronchoscope for use during intensive care procedure involving an endotracheal tube is provided. In this method, the endotracheal tube has a lumen cross section and a length and the insertion tube comprises a proximal portion with an outer cross section, a distal portion and a camera docking terminal at the distal end of the distal portion and connecting and transmitting wire running from the camera docking terminal, along the insertion tube up to the proximal end of the proximal portion;

wherein the insertion tube is selected so that the area difference between the lumen cross section of the endotracheal tube and the outer cross section is at least 20 mm², preferably at least 23 mm², preferably at least 29 mm², and so that the proximal portion is longer than the length of the endotracheal tube.

The endotracheal tube usually has a length of 20 cm, 30 cm or more.

The endotracheal tube may have an inner diameter of 6.5 mm, 7 mm, 7.5 mm and 8 mm respectively, the outer diameter of the proximal portion of the selected insertion tube being thus at most 4.10 mm, 4.85 mm, 5.55 mm, 6.21 mm respectively, preferably at most 3.60 mm, 4.44 mm, 5.19 mm, 5.89 mm respectively.

Preferably, the outer diameter of the proximal portion of the selected insertion tube is 4 mm.

In still another aspect of the present invention, a method for using a flexible bronchoscope as described above is provided. This method comprises the steps of:

- selecting an insertion tube for the flexible bronchoscope according to the corresponding method described above;

- inserting the flexible bronchoscope through the endotracheal tube at least until the distal portion of the insertion tube completely comes out of the endotracheal tube.

Drawings

Further objectives, advantages and features of the present invention will be apparent from the following description of exemplified embodiments together with the illustrating ad non-limiting accompanying drawings, wherein:

Figure 1 is a schematic representation of a flexible bronchoscope according to the invention inserted through an endotracheal tube;

Figure 2 is a diagram showing the percentage of minute ventilation against the baseline (minute ventilation measured without the flexible bronchoscope inserted through the endotracheal tube) for healthy lungs at PIPmax of 60 cmH₂0;

Figure 3 is a diagram showing the percentage of minute ventilation against the baseline for ARDS lungs at PIPmax of 60 cmH₂0; Figure 4 is a diagram showing the difference of PEEP in the lungs after insertion of the flexible bronchoscope into the endotracheal tube, with regards to the baseline for healthy lungs at PIPmax of 100 cmH₂0;

Figure 5 is a diagram showing the difference of PEEP in the lungs after insertion of the flexible bronchoscope into the endotracheal tube, with regards to the baseline for ARDS lungs at PIPmax of 100 cmH₂0;

Figure 6 is a diagram showing the suction flow in a bronchoscope with the insertion tube of the invention and in a paediatric bronchoscope at vacuum level of - 150 mmHg; and

Figure 7 is a diagram showing the suction flow in a bronchoscope with the insertion tube of the invention and in a paediatric bronchoscope at vacuum level of - 300 mmHg.

Description of the invention The insertion tube of the invention is a component of a flexible bronchoscope that is dedicated for use during intensive care procedure involving an endotracheal tube. As previously mentioned, endotracheal tubes vary in size, especially in length and inner diameter. In order to enable sufficient ventilation, it is important to select the insertion tube correctly. An endotracheal tube typically comprises an elongated body with lumen therein.

The insertion tube of the invention is described hereafter with reference to figure 1.

The insertion tube 12 comprises a proximal portion 121, a distal portion 122, a camera docking terminal 124 and at least one connecting and transmitting wire 125.

In the present disclosure, "proximal" and "distal" are two opposite terms and are considered with regards to the operator and not the patient. "Proximal" is intended to mean closer to the operator hand, wherein "distal" is intended to mean farther from the operator hand.

The proximal portion 121 is intended to remain inside the endotracheal tube 2 while the distal portion 122 is intended to extend outside the endotracheal tube 2 in operation. Each of the proximal and distal portions 121, 122 of the insertion tube 12 presents an inner diameter defining a suction channel 123 and an outer diameter. The inner diameter of the proximal and distal portions 121, 122 is at least 2 mm, preferably of at least 2.1 mm.

The outer diameter of the proximal portion 121 is at most 5 mm, at most 4.5 mm, preferably at most 4 mm. The length of the proximal portion 121 is at least 20 cm, preferably at least 25 cm, preferably at least 30 cm, preferably at least 35 cm.

Alternatively, the proximal portion 121 has an outer cross section defined by the outer diameter selected so that the area difference between the lumen cross section of the endotracheal tube (defined by its inner diameter) and the outer cross section is at least 20 mm², preferably at least 23 mm², preferably at least 29 mm². The proximal portion 121 also needs to be longer than the length of the endotracheal tube 2, and the inner diameters forming a suction channel 123 of both the proximal and distal portions 121, 122 of the insertion tube 12 are at least 2 mm, preferably of at least 2.1 mm.

The dimensions of the distal portion 122 of the insertion tube 12 that are not mentioned hereabove must be sufficient to receive a miniaturised camera and for the distal portion 122 to be inserted into the endotracheal tube 2 through the proximal end of the endotracheal tube 2 and exit at the distal end of the endotracheal tube 2. Since only the proximal portion 121 of the insertion tube 12 is responsible for the obstruction of the air flow path through the endotracheal tube 2, the outer diameter of the distal portion 122 does not need to meet other requirements that the one mentioned above. Thus, the distal portion 122 may have an outer cross section wider than the outer cross section of the proximal portion 121 particularly in order to receive a miniaturised camera, or in other words an outer diameter wider than the outer diameter of the proximal portion 121. For example, the outer diameter of the distal portion 122 is lower than 5.3 mm while still greater than the outer diameter of the proximal portion 121. The length of the distal portion 122 is preferably 8 cm or lower.

The camera docking terminal 124 is located at the distal end of the distal portion 122. The camera docking terminal 124 is intended to receive a miniaturised camera 16 for acquiring image of the operation site within the body of the patient. The camera docking terminal 124 is preferably integrated into the wall of the distal portion 122, e.g. a small non-through hole provided at the end of the distal portion 122, the cross section of which is chosen so that the miniaturised camera 16 to be docked within perfectly fits in without play. Preferably the depth of the small non-through hole corresponds to the length of the miniaturised camera 16 to be docked within. As such, the camera docking terminal 124 is positioned side by side with the suction channel 123.

Using a miniaturised camera 16 for visualisation at the operation site only requires a connecting and transmitting wire 125 that extends along the insertion tube 12, possibly outside the insertion tube 12 but preferably inside or integrated within the wall of the insertion tube 12, from the camera docking terminal 124 up to the proximal end of the proximal portion 121.

It is not necessary to have optical fibres, which are usually incorporated within the wall of a flexible bronchoscope of the prior art, what made it impossible to thin the wall of the insertion tube 12. On the contrary, in the insertion tube 12 according to the invention, the connecting and transmitting wire 125 makes it possible to have a thinner wall for the insertion tube 12, thereby making it possible to decrease the outer diameter of the insertion tube 12 and to have a wide suction channel 123 at the same time.

The connecting and transmitting wire 125 both powers the miniaturised camera 16 and transmits the data acquired by the miniaturised camera 16, for example to an ΓΓ system for processing and display of the data. Here, the insertion tube 12 is described with only one connecting and transmission wire 125, however, it is possible to provide one wire for connecting, i.e. powering, the miniaturised camera 16 and another wire for transmitting the data acquired by the miniaturised camera 16. The term "connecting and transmitting wire" encompasses the meaning of one wire dedicated to connecting and another one dedicated to transmitting. The outer diameter of the connecting and transmitting wire is preferably 1 mm or lower. When there are one wire dedicated to connecting and another one dedicated to transmitting, the outer diameter of each of these wires is preferably 1 mm or lower.

The insertion tube 12 typically is free from optical fibres that are used to convey light from the distal portion 122 to the proximal portion 121 so that an image of the operation site is obtained. Indeed image data are transmitted from the miniaturised camera 16 through the transmitting wire 125.

The insertion tube 12 usually also comprises two guiding cables that run all along the length of the insertion tube 12, preferably integrated inside the wall of the insertion tube 12. Each of the guiding cables comprises a connecting end for connecting to handle (see below), the other end being placed within the distal portion 122. These guiding cables are sufficiently thin so that their integration within the wall of the insertion tube 12 is not a limiting factor to the suction channel. The outer diameter of the guiding cables is preferably 0.5 mm or lower.

The insertion tube 12 may further comprise a light source docking terminal 126 at the distal end of its distal portion 122 to receive a light source 17. The insertion tube 12 may further comprise a power wire 127 for powering the light source 17, possibly outside the insertion tube 12 but preferably inside or integrated within the wall of the insertion tube 12. The outer diameter of the power wire is preferably 1 mm or lower.

The insertion tube 12 can be used as a component of a flexible bronchoscope 1. Advantageously, the insertion tube 12 is disposable, thus forming a disposable part of the flexible bronchoscope 1.

The flexible bronchoscope 1 can further comprise a camera 16, preferably a miniaturised camera 16. The camera 16 can be permanently docked to the camera docking terminal 124. In such case, the insertion tube 12 is provided with the camera 16 and if disposable, the camera 16 is also a disposable camera. Alternatively, the camera 16 is releasably dockable to the camera docking terminal 124. In order for the camera 16 to be connected to the connecting and transmitting wire 125, a connexion can be provided on the camera docking terminal 124 that is used to connect and fix the camera

16 onto the camera docking terminal 124 at the same time. The camera 16 typically comprises an objective coupled with light sensors. The light sensors are then connected to an output port connected to the transmitting wire 125.

The flexible bronchoscope 1 can further comprise a light source 17. The light source

17 is typically a LED system comprising at least one LED, preferably a white LED system. The light source 17 can be permanently docked to the light source docking terminal 126. In such case, the insertion tube 12 is provided with the light source 16 and if disposable, the light source 17 is also a disposable light source. Alternatively, the light source 17 is releasably dockable to the light source docking terminal 126. In order for the light source 17 to be connected to the powering wire 127, a connexion can be provided on the light source docking terminal 126 that is used to connect and fix the light source 17 onto the light source docking terminal 126 at the same time.

The combination of the use of a miniaturised camera and of a light source disposed directly at the distal portion of the insertion tube provide one of the best results, notably because the outer diameter of the proximal portion can be lowered down to 4 mm and below, whereas the need of optical fibres in the bronchoscope of the prior art precluded this innovation. Further, the use of a miniaturised camera and a light source make is possible to manage without any bulky and cumbersome appliances for producing light and for processing the light received from the operation site into image data.

The flexible bronchoscope 1, advantageously, comprises a handle 14 with a bending control. The bending control controls the other ends of the guiding cables either in two opposing directions (e.g. up/down or right/left) or in two pairs of opposing directions, one pair of opposing directions being preferably normal to the other pair of opposing directions. In one embodiment, the handle 14 is permanently connected to the proximal end of the proximal portion 121 of the insertion tube 12. In such case, the insertion tube 12 is provided with the handle 14. Alternatively, the handle 14 is releasably connectable to the proximal end of the proximal portion 121 of the insertion tube 12.

The table 1 below sums up the different possibilities:

Table 1: possible combinations

The term "releasably" means that the components are meant to be connected to one another and disconnected from one another by the user. The term "permanently" means that the components are not meant to be disconnected from one another by the user.

The different embodiments of the above table have different advantages. For instance, in embodiment A, it is possible to provide a handle and a camera that are reusable; only the insertion tube is disposable. This reduces the burden of cleaning the insertion tube between uses for different patients. The handle and the camera are preferably reusable due to their manufacturing costs. In embodiment D, both handle and camera are permanently connected to the insertion tube. This reduces the burden of mounting the flexible bronchoscope before use and might be very useful in emergency case when medical actions must be taken rapidly in order to save the patient's life.

A method for selecting an insertion tube for a flexible bronchoscope for use during intensive care procedure involving an endotracheal tube having a lumen cross section and a length is hereafter described.

This method is to be used with the insertion tube described above. The method comprises selecting the insertion tube so that the area difference between the lumen cross section of the endotracheal tube and the outer cross section of the proximal portion of the insertion tube is at least 20 mm², preferably at least 23 mm², preferably at least 29 mm², and so that the proximal portion is longer than the length of the endotracheal tube.

In the case where endotracheal tube has a length of 20 cm, 30 cm or more, the proximal portion of the insertion tube must be at least 20 cm, 30 cm or more respectively.

When the endotracheal tube has an inner diameter of 6.5 mm, 7 mm, 7.5 mm and 8 mm respectively, the outer diameter of the proximal portion of the selected insertion tube being thus at most 4.10 mm, 4.85 mm, 5.55 mm, 6.21 mm respectively, preferably at most 3.60 mm, 4.44 mm, 5.19 mm, 5.89 mm respectively, preferably at most 2.31 mm, 3.48 mm, 4.40 mm, 5.20 mm respectively.

In one preferred embodiment, the outer diameter of the proximal portion of the selected insertion tube is 4 mm. This seems to be an optimal diameter useable with most of the existing endotracheal tubes.

A method for using the flexible bronchoscope according to the invention comprises the steps of:

- selecting an insertion tube for the flexible bronchoscope according to the method described above; and

- inserting the flexible bronchoscope through the endotracheal tube at least until the distal portion of the insertion tube completely comes out of the endotracheal tube. In case the bronchoscope is provided as a kit, the different components of the bronchoscope are mounted to one another before inserting the flexible bronchoscope through the endotracheal tube. Examples

Flexible bronchoscopes with insertion tubes with various outer diameters of the proximal portion have been tested in endotracheal tubes of various inner diameters.

Four different endotracheal tubes with different inner diameters were used: 6.5 mm; 7.0 mm; 7.5 mm and 8.0 mm in diameters (labelled "ETT X.X" in the figures). Six different insertion tubes were tested with outer diameters of their proximal portion being 5.3 mm, 4.6 mm, 4.0 mm, 3.3 mm and 2.6 mm.

Table 2 shows the difference between the lumen cross section of the endotracheal tube used and the outer cross section of the proximal portion of the insertion tube used.

( values are in mm and mm²)

* Comparative examples

Table 2: area differences between the lumen cross section of the endotracheal tube and the outer cross section of the proximal portion of the insertion tube

All combinations were tested on a high fidelity breathing simulator (Model 5600i, Dual Adult Pneuview System, Michigan Instruments, Grand Rapids, USA). This breathing simulator simulates respiratory mechanics in adults with normal lung compliance and airway resistance (thereafter called "healthy lungs") and with pathological lung functions corresponding to severe acute respiratory distress syndrome (thereafter called "ARDS lungs").

Parameters for the ARDS lung were based on the PROSEVA study [Guerin,l l] and correspond to severe ARDS according to the Berlin definition criteria. An EVTTA XL ventilator (Drager Medical GmBH, Liibeck, Germany) was used for mechanical ventilation; it was connected to the endotracheal tube (thereafter labelled "ETT") and lung model using standard ventilator tubing, and a volume control ventilation mode was used.

Ventilation simulation for healthy lungs was carried out as follows: tidal volume at 550 ml, respiratory rate at 14/min, positive end-expiratory pressure (PEEP) at 5 cmH₂0 (4.90 mbar), inspiratory flow (IF) at 60 L/min, compliance at 100 mL/cmH₂0 (101.97 mL/mbar), inspiratory/expiratory ratio time at 0.5.

Ventilation simulation for ARDS lungs was carried out as follows: tidal volume at 380 ml, respiratory rate at 27/min, PEEP at 10 cmH₂0 (9.81 mbar), IF at 60 L/min, compliance at 35 mL/cmH₂0 (35.69 mL/mbar), inspiratory/expiratory ratio time at 0.5.

In practice, when a flexible bronchoscope is in place in a mechanically ventilated patient, the high-pressure limit is often increased up to the maximal value to maintain ventilation. For the need of the tests, high-pressure limit (PIPmax) was first arbitrarily set at 60 cmH₂0 (58.84 mbar) and efficiency of mechanical ventilation was observed. Efficiency of mechanical ventilation is measured by the minute ventilation, assessed by the spirometer of the ventilator

The results are shown in figure 2 for "healthy lungs" and in figure 3 for "ARDS lungs", where measured minute ventilations MV are given in percentage of the baseline minute ventilations, e.g. without the flexible bronchoscope inserted into the endotracheal tube.

Minute ventilations were considered "unmodified" if MV is 95-100 % of baseline, "acceptable" if MV is 75-95 % of baseline and "significantly altered" if MV is lower than 75 % of baseline.

The lung model provided readings for alveolar pressures with a manometer, which were used to determinate total PEEP. Increase of PEEP in the lungs (total PEEP - initial PEEP) was measured after the high-pressure limit was increased up to the maximal value.

The two levels of maximal peak inspiratory pressure were, thus, 60 cmH₂0 (58.84 mbar) and 100 cmH₂0 (98.07 mbar).

The results are shown in figure 4 for "healthy lungs" and in figure 5 for "ARDS lungs". Increase of equal or less than 2 cmH₂0 (1.96 mbar) of total PEEP is considered clinically acceptable.

Concerning "healthy lungs", when the PIPmax was set at 60 cmH₂0 with a 5.3mm bronchoscope, ventilation was "unmodified" only for the 8.0 mm endotracheal tube, and "significantly altered" for the other endotracheal tubes (60% of MV was delivered with the 7.5 mm endotracheal tube, 40% of MV with the 7.0 mm endotracheal tube, and ventilation was impossible with a 6.5 mm endotracheal tube). With a 4.6 mm bronchoscope, ventilation was "unmodified" for the 7.5 mm endotracheal tube, "acceptable" for the 7.0 mm endotracheal tube and was "significantly altered" for the 6.0 mm endotracheal tube. With a 4.0 mm bronchoscope, ventilation was "unmodified" for the 7.0 mm and 7.5 mm endotracheal tubes, and was "acceptable" for the 6.5mm endotracheal tube. For all the smaller sizes of bronchoscope, ventilation was "unmodified" for all the endotracheal tubes.

When PIPmax was set to 100 cmH20, the lung was efficiently ventilated but the total-PEEP increased proportionally leading to an equivalent increase of the plateau pressure. More precisely, the delivery volume was unchanged from baseline after the insertion of the bronchoscopes, except for the 5.3 mm bronchoscope in the 6.5 mm and 7.0 mm endotracheal tubes and the 4.6 mm bronchoscope in the 6.5 mm endotracheal tube. However, the total-PEEP and the plateau pressure increased immediately following insertion of a 5.3 mm bronchoscope in all conditions. With the 4.6 mm bronchoscope, Atotal-PEEP was only clinically acceptable for the 7.5 and 8.0 mm endotracheal tube. With a 4.0 mm (or narrower) bronchoscope, Atotal-PEEP was clinically acceptable for all of the endotracheal tube, except for the 6.5 mm endotracheal tubes. The increase of the plateau pressure was almost identical to the increase of the PEEP in all conditions.

Concerning ARDS lungs, when the PIPmax was set to 60 cmH₂0, with a 5.3 mm bronchoscope, ventilation was only possible with 7.5 mm or 8.0 mm endotracheal tubes, and was "significantly altered" for the 7.5 mm endotracheal tube; ventilation was impossible with the smaller endotracheal tubes. With the 4.6mm bronchoscope, ventilation was "unmodified" with the 7.5 mm endotracheal tube, "significantly altered" with the 7.0 mm endotracheal tube and impossible with a 6.5 mm endotracheal tube. When PIPmax was set to 100 cmH₂0, the delivery volume recovery was identical to that for the "healthy lung" condition (see above); however, the total-PEEP increased substantially and led to an equivalent escalation of plateau pressure. With a 5.3 mm bronchoscope, the total-PEEP and the plateau pressure increased immediately in all conditions. The Atotal-PEEP was clinically acceptable only with an 8.0 mm endotracheal tube, and Atotal-PEEP was +5 cmH₂0 with a 7.5 mm endotracheal tube, and +6 cmH20 with a 7.0 mm endotracheal tube. With a 4.6 mm bronchoscope, Atotal- PEEP was clinically acceptable for 7.5 mm and 8.0 mm endotracheal tubes; Atotal- PEEP increased by +4 cmH20 with a 7.0 mm endotracheal tube and +7 cmH₂0 with a 6.5 mm endotracheal tube. With a 4.0 mm bronchoscope, Atotal-PEEP was clinically acceptable for 7.0 mm to 8.0 mm endotracheal tubes, and was +3 cmH₂0 with a 6.5mm endotracheal tube. For all the smaller sizes, Atotal-PEEP was clinically acceptable for all endotracheal tubes. In all the conditions, the change in the plateau pressure was equal to the increase of the PEEP.

The present authors have shown that although the insertion tube of a paediatric bronchoscope may exhibit a narrower diameter in comparison with bronchoscope used for adults, its suction channel is however insufficiently wide to ensure efficient suction when used for adults. Indeed, they have compared the efficacy of the suction channel of a bronchoscope comprising the insertion tube of the present invention with that of a paediatric bronchoscope (model FI-10RBS, Pentax, Hamburg, Germany). This paediatric bronchoscope presented an outer diameter of the insertion tube of 3.5 mm and an inner diameter of 1.3 mm (suction channel). The insertion tube of the present invention presented an outer diameter at the proximal portion of 3.6 mm and of 5.3 mm at the distal portion, which was about 2 cm long. The inner diameter was 2.1 mm (suction channel).

To test the capacity of the suction channel of each flexible bronchoscope, the suction flow was measured with two vacuum levels, -150 mmHg and -300 mmHg, using a Lagoon 600 apparatus from Air Liquid Medical System, Puteaux, France and by measuring the time required to aspirate 100 mL of sterile water (from Versylene Fresenus, Louviers, France) or 100 mL of viscous water to simulate thick secretions. Viscous water was obtained from a dilution of 3% of ultrasound gel (Uni'gel, Aseptln Med, Quint Fonsegrives, France) in water. Each Experiment was made in triplicate; average values of suction flow are reported.

A high fidelity breathing simulator (Model 5600i, Dual Adult Pneuview System, Michigan Instruments, Grand Rapids, USA) was used to simulate respiratory mechanics of adults with pathological lung functions corresponding to severe ARDS. Parameters for the ARDS lung were based on the PROSEVA study [11] and corresponded to severe ARDS according to the Berlin definition criteria [12]. An EVETA XL ventilator (Drager Medical GmBH, Liibeck, Germany) was used for mechanical ventilation; it was connected to the endotracheal tube and lung model using standard ventilator tubing. In accordance with the guidelines for the management of severe ARDS ventilator settings [13], volume control ventilation mode at a tidal volume at 380 mL, respiratory rate at 27 min^-1, PEEP at 10 cmH₂0, inspiratory flow at 60 L/min and inspiratory time at 0.5 was used. The compliance of the artificial lungs was 35 mL/cmH₂0. In practice, when a bronchoscope is in place in a ventilated patient, the high-pressure limit is often increased up to the maximal value to maintain ventilation. First, the inspiratory pressure limit was arbitrarily set to 60 cmH₂0 and the efficiency of ventilation was observed. The inspiratory pressure limit was then increased up to the maximal value (100 cmH₂0).

The bronchoscopes were evaluated in endotracheal tubes with internal diameters of 6.5, 7.0, 7.5 and 8.0 mm (Mallinckrodt, Covidien, Tullamore, Ireland). Consequently, 8 bronchoscope/ETT combinations were tested. Measures were taken both with and without the bronchoscopes in place, and repeated 3 times for each combination. Experiments were performed in triplicate; average values following a 1-min run are reported.

Animal experimentation were performed on two healthy piglets (Large White, 2-3 months of age) according to the guidelines of the Council Directive no. 86/609 of the European Economic Community of 24th November 1986, The protocol was approved by the "Comite d'Ethique en Experimentation Animale Val-de-Loire" (n° 00028.01). Animals were sedated with intramuscular xylazine (2 mg/kg) and ketamine (20 mg/kg), and then anaesthetised with inhaled isoflurane. After tracheal intubation with a 7.0 mm endotracheal tube, animals' lungs were mechanically ventilated with a Fabius Tiro Ventilator (Drager, Telford, PA, USA). Noteworthy, piglets of this age have low pulmonary compliance compared to human (< 40 cmH₂0/mL).

At vacuum level of -150 mmHg, suction flow provided by the paediatric bronchoscope was clearly inferior to the bronchoscope with the insertion tube of the invention (almost 2 fold inferior) as shown by figure 6:

bronchoscope of the invention: 247 + 5 mL/min for water and 176 + 8mL/min for viscous fluid; and

paediatric bronchoscope: 147 + 2 mL/min for water and 100+2 mL/min for viscous fluid.

Decreasing the vacuum level from -150 to -300 mmHg slightly increased the suction flow of the paediatric bronchoscope but was not a solution to significantly increase the suction performance thereof (figure 7):

bronchoscope of the invention: 444 + 19 mL/min for water and 392 + 13 mL/min for viscous fluid; and

paediatric bronchoscope: 198 + 4 mL/min for water and 158 + 4 mL/min for viscous fluid.

Bibliography

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Claims

1. An insertion tube (12) for a flexible bronchoscope (1) for use during intensive care procedures, comprising a proximal portion (121), a distal portion (122), a camera docking terminal (124) at the distal end of the distal portion (122) and at least one connecting and transmitting wire (125) running from the camera docking terminal (124), along the insertion tube (12) up to the proximal end of the proximal portion (121);

each of the proximal and distal portions (121, 122) having an inner diameter of at least 2 mm, preferably of at least 2.1 mm, forming a suction channel (123) and an outer diameter;

wherein the outer diameter of the proximal portion (121) is at most 4 mm, the length of the proximal portion (121) being at least 20 cm, preferably at least 25 cm, preferably at least 30 cm, preferably at least 35 cm.

2. An insertion tube (12) for a flexible bronchoscope (1) for use during intensive care procedure involving an endotracheal tube (2) having a lumen cross section and a length, the insertion tube (12) comprising a proximal portion (121) to remain inside the endotracheal tube (2), a distal portion (122) to extend outside the endotracheal tube (2), a camera docking terminal (124) at the distal end of the distal portion (122) and at least one connecting and transmitting wire (125) running from the camera docking terminal (124), along the insertion tube (12) up to the proximal end of the proximal portion (121);

each of the proximal and distal portions (121, 122) having an inner diameter of at least 2 mm, preferably of at least 2.1 mm, forming a suction channel (123) and an outer diameter, the outer diameter of the proximal portion (121) being at most 4 mm;

wherein the proximal portion (121) has an outer cross section selected so that the area difference between the lumen cross section of the endotracheal tube (2) and the outer cross section is at least 20 mm², preferably at least 23 mm², preferably at least 29 mm²; wherein the proximal portion (121) is longer than the length of the endotracheal tube (2).

3. The insertion tube (12) of claim 1 or claim 2, wherein the distal portion (122) has an outer cross section wider than the outer cross section of the proximal portion (121).

4. The insertion tube (12) of any one of claim 1 to 3, further comprising a light source docking terminal (127) at the distal end of the distal portion (122).

5. A flexible bronchoscope (1) for use during intensive care procedures, comprising the insertion tube (12) of any claim 1 to 3.

6. The flexible bronchoscope (1) of claim 4, further comprising a camera (16) permanently docked to or releasably dockable to the camera docking terminal (124).

7. The flexible bronchoscope (1) of claim 4 or claim 5, wherein the insertion tube (1) comprises a light source docking terminal (127) at the distal end of the distal portion (122), and wherein the flexible bronchoscope further comprises a light source (17) permanently docked to or releasably dockable to the light source docking terminal (127).

8. The flexible bronchoscope of any one of claim 5 to 7, further comprising a handle (14) with a bending control, the handle (14) being permanently connected to or releasably connectable to the proximal end of the proximal portion (121) of the insertion tube (12).

9. A method for selecting an insertion tube for a flexible bronchoscope for use during intensive care procedure involving an endotracheal tube having a lumen cross section and a length, wherein the insertion tube comprises a proximal portion with an outer cross section, a distal portion and a camera docking terminal at the distal end of the distal portion and connecting and transmitting wire running from the camera docking terminal, along the insertion tube up to the proximal end of the proximal portion; wherein the insertion tube is selected so that the area difference between the lumen cross section of the endotracheal tube and the outer cross section is at least 20 mm², preferably at least 23 mm², preferably at least 29 mm², and so that the proximal portion is longer than the length of the endotracheal tube.

10. The method of claim 9, wherein the endotracheal tube has a length of 20 cm, 30 cm or more.

11. The method of claim 9 or claim 10, wherein the endotracheal tube has an inner diameter of 6.5 mm, 7 mm, 7.5 mm and 8 mm respectively, the outer diameter of the proximal portion of the selected insertion tube being thus at most 4 mm, preferably at most 3.60 mm.

12. A method for using the flexible bronchoscope of claim 4, comprising the steps of:

- selecting an insertion tube for the flexible bronchoscope according to the method of any claim 9 or 11 ;