GB2338902A

GB2338902A - Micro ventilation anaesthetic circuit

Info

Publication number: GB2338902A
Application number: GB9917113A
Authority: GB
Inventors: Falah Hasan Ali
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-07-21
Filing date: 1999-07-21
Publication date: 2000-01-12
Anticipated expiration: 2019-07-21
Also published as: GB2338902B; GB9917113D0

Description

2338902 MODIFIED MICRO VENTELATION ANAESTBETIC CIRCUIT This invention

relates to a modified micro ventilation araesthetic circuit. Micro ventilation anaesthetic circuit having the patent specification no. GB 2318518, by the same inventor, is based on the use of a double lurnen endotracheal tube, a narrow one for continuous fresh gas flow ( FGF) and a larger tube for interrupted expiratory flow using an occluder ( solenoid) valve to accomplish this interruption. For economic reasons and to reduce pollution, this circuit is modified according to this invention to include a closed system to be used on need, in addition to its basic function of automatic ventilation, Criteria and benefits of a modified micro ventilation anaesthetic circuit.

------------------------ 1. To overcome the drawbacks of IPPV on the haemodynamics of pulmonary and systemic circulation, and to avoid the potential hazards of high frequency ventilation. The lung can be ventilated with a minimal positive intra. pulmonary pressure ( few cms H20).

2. Economy is one of its criteria using relatively lower FGF, as a closed circle, in comparison to the original micro ventilation anaesthetic circuit mentioned above, and it is less polluting. 3. Positive End Expiratory Pressure ( PEEP) during controlled ventilation, and Continuous Positive Airway Pressure ( CPAP) in spontaneous ventilation can be provided on need.

4. Oxygenation is secured as far as the FGF is continuously flowing in to the broncheal tree, irrespective of lung movement. This fact reduces mortality and morbidity caused by hypoxia during anaesthesia, and when used in ICU cases, dramatically.

5. Minimal lung movement is enough to washout C02. Therefore, significant hypercapnoea 2 will not be established unless the lung is in apnoea. However, there is a safety period of about 10 -- 15 min. in apnoea. Thereafter, alveolar C02 partial pressure will rise sharply. 6. The circuit is suitable for ICU cases needing long term ventilation if a suitable humidifier, air -- 02 mixer and other essential equipments are added. 7. Weaning; As far as oxygenation is practically separated from C02 washout, it is so easy to control C02 level which is needed to stimulate respiratory centre without affecting oxygenation. 8. Paediatric use; This circuit can be modified for paediatric use. 9. Increased airway resistance in chronic obstructive lung diseases will not interfere with the function of this circuit because ventilation doesn't depend on using big tidal volumes. Dealing with lungs of low compliance is explained on the same basis. 10. The circuit provides the beneficial criteria of high frequency ventilation. 11. It is a low pressure circuit, relatively free of the hazards of barotrauma. 12. There is no need to use high cuff inflation pressure to protect the trachea, reducing the possibility of sloughing to the trachea] mucosa. 13. Using this circuit, there is a good time for suctioning of the broncheal tree through the expiratory tube as far as FGF is continuous. 14. In bronchoscopy; Fibroptic broncoscope is introduced via the expiratory tube Cobb's suction connector. 15. in expected difficult intubation, FGF source is attached early during the procedure 3 so that to prevent hypoxia. A newly trained doctor may utilise this benefit during intubation. 16. In emergency cases, the use of the double lumen tube alone with FGF source is sufficient to perform efficient ventilation. manual interruption of expiratory flow is needed to ventilate the lung during apnoea. 17. Single lumen tubes of deferent types can be modified to be used in this circuit e.g. plastic tracheostomy tube. 18. Thorpcic anaesthesia; A specially designed four lumen tube is needed to perform one lung ventilation, having the same mentioned benefits. 19. Types of ventilation performed by this circuit; There are two phases-, a. Phase one or closed circuit.

I, spontaneous ventilation.

2. controlled manual ventilation. b. Phase two or semi closed circuit.

1. spontaneous ventilation.

2. automatic ( solenoid interruption) ventilation. According to the present invention there is provided a closed micro ventilation anaesthetic circuit comprising a double lumen tube having a narrow lumen for continuous FGF and a larger lumen for expiratory flow. There are two corrugated tubes, one is the inspiratory limb and the other is the expiratory limb, with two unidirectional valves. The circuit contains soda lime absorber, expiratory valve and reservoir bag. There is a solenoid valve for automatic ventilation.

4 A specific embodiment of the invention will now be described by way of example with reference to the accompanyir:g drawings in which; Figure I shows in perspective the components of a modified micro ventilation anaesthetic circuit.

Figure 2 illustrates the details of the electronic compartment of the solenoid valve. Figure 3 shows the modified Waters's'to & fro'C02 absorber.

Referring to the drawing the modified micro ventilation anaesthetic circuit can provide the following types of ventilation; Closed circuit; ----------------- FGF I of about I -- 3 litres ( 30% -- 50% 02) is given through the inspiratory lumen 2. The expiratory flow moves via expiratory tube 3 to the expiratory limb. Cobb's suction connector 3 is used for suctioning of the broncheal tree. Connection piece 8 connects the capnograph 29 to the circuit. The expired gas moves through the expiratory limb 13 via the branch I I of the Y connection piece 9 which is attached to the proximal end 12 of the expiratory limb 13. The latter is attached to the unidirectional valve 15 via its distal end 14. The expired gas moves through the solenoid valve 22 which is'off'i.e. opened in this situation.

The expiratory flow is directed toward the soda lime absorber 20 through the diversion valve 2 1. Thereafter, the flow moves partly toward reservoir bag 27 and partly toward the patient through the inspiratory limb 17. The latter is connected to the unidirectional valve 19 at its distal end 18, and to the branch 10 of the Y piece 9 via its proximal end 16. The gas moves always in clock,,Aise direction due to the presence of the unidirectional valves 15 & 19.

The face mask 31 is used during induction and recovery from anaesthesia. It has two ways connection piece 32, the small one 33 is to connect the FGF1 and the big one 34 is to connect the Y piece 9. The mask is of deferent sizes. In controlled ventilation, using reservoir bag 27, the patient receives purified gas mixture through the inspiratory limb 17 as well as the FGF I. The expiratory gas moves toward the expiratory limb 13 and then to the soda lime absorber 20.

Semi closed circuit; --------- -- ---- --In case of using the semi closed aspect of this circuit, a relatively higher FGF is needed. In spontaneous ventilation, patient breaths a mixture of FGF and from the reservoir bag 27 through the inspiratory limb 17. Expired gas moves through the expiratory limb 13. The excess of gas moves out through the expiratory valve 26.

In automatic ventilation, solenoid valve 22 is s!t ' on The diversion valve 21 is shifted to direct the flow toward the bypass tube 24 which is attached to the sidearm 23 of the diversion valve 2 1. This bypass tube 24 is attached to the cross connection 25. The bypassed gas moves down to the reservoir bag 27. When solenoid valve 22 closes, the valve 19 closes as well giving the chance for the FGF to provide the lung with the pre set tidal volume. GENERAL NOTES; Expiratory valve 26 spills gases upstream of the absorber 20, to conserve soda lime.

The diversion valve 21 is shifted toward the bypass tube 24 to change the exhausted soda lime Unidirectional valve; is a horizontal flat disc valve of low weight sitting on a vertical valve seat under a transparent dome allowing the anaesthetist to make a visual inspection of valve 6 operation. These valves may be replaced with a fan circulator driven by a gas turbine, electric motor or a Venturi device, as seen in new generationsof closed circles. The capacity of the modified micro ventilation closed circuit is about 5 litres, to provide a safety margin for 02 failure. The vaporiser in this case is out side the circuit i.e. ( VOC This is chosen to simplify the use of this circuit to be connected to most of the anaesthetic machine. Air suction valve seen in the patent no. GB 2318518 is cancelled. The patient can breath freely during automatic ventilation against closed solenoid valve. Capnography, it gives a new signiture for this circuit which needs to be studied to differentiate the normal from abnormal configuration. Reservoir bag 27 ( 2 litres) is used; 1. To control ventilation manually. 2. For visual monitoring of ventilation. 3. At weaning. 4. During induction and recovery from anaesthesia. 5. To assess lung compliance and airway resistance manually. 6. To check doubtful endobroncheal intubation. The corrugated tubes are non expanding to reduce wasting during ventilation. Solenoid valve interrupts at a rate up to 100 / min., giving a tidal volume as low as 50 -- 100 mls. There is expected reduction in the dose of muscle relaxant needed, 7 Expiratory valve 26, in addition to its basic function, it can initiate PEEP ( in automatic ventilation) & CPAP ( in spontaneous ventilation). Airway pressure inside the circuit is measured by the pressure sensor 30 which is attached to the side tube 6 of the endotracheal tube. A simple pressure gauge may be used instead. A pop off valve may be added to the circuit between the solenoid valve 22 and the patient. The following table shows the recommended measurements of the inspiratory tube sizes and the total tube sizes suitable for automatic microventilation; Inspiratory tube size Total tube size ------------------------ ----------------- I mm ID (internal diameter) 3.5 mm ID 1.5 mm ID 4, 4.5 mm ID 2 mm ID 5, 5.5 mrn ID 2.5 mm ID 6.5 mm. ID & above.

The following table shows the recommended measurements of the inspiratory tube sizes and total tube sizes suitable for closed micro ventilation circuit; Inspiratory tube size Total tube size -------------------------------------- I mm DD 4, 4.5 mm UD 1.5 mm ID 5, 5.5 mm ID 2mrn ID 6 mm ID & above These measurements are done using FGF of the anaesthetic machine. Figure 2 illustrates the details of the electronic compartment of the solenoid valve22; The inspiratory time control 35 is working at a range of 0.4 -- 1.2 seconds. The expiratory time control 31 is working at a range of 0.4 - - 1.4 seconds. The lamp 34 indicates the main electricity supply. The visual alarm 32 and the audible alarm 33, signal when the pressure inside the circuit is at zero level for about 30 seconds unless it is set' off' during suctioning.

8 Figure 3 shows the modified Waters's'to & fi-o'C02 absorber which is composed of the following parts; a double lumen tube, a FGF source 36, a soda lime carister 38, a reservoir bag 39, and an expiratory valve 37. The Cope's modification of the Waters's absorber is included in this invention, 9

Claims

CLAIMS 1. A modified micro ventilation anaesthetic circuit comprising a

double lumen endotracheal tube having a narrow lumen for continuous inspiratory flow and a larger lumen for expiration; an inspiratory & expiratory limb; a soda lime absorber; a solenoid valve; a double unidirectional valves; and an expiratory valve with a reservoir bag. 2. A modified micro ventilation anaesthetic circuit as claimed in claim I, wherein the expiratory valve is placed upstream of the absorber in order to conserve soda lime. 3.A modified micro ventilation anaesthetic circuit as claimed in claim 2, wherein the capacity of the circuit is about 5 litres. 4. A modified micro ventilation anaesthetic circuit as claimed in claim 3, wherein the diversion valve 21 allows the flow to move in one direction, either to the soda lime absorber 20 or to the bypass tube 24. 5. A modified micro ventilation anaesthetic circuit as claimed in claim 4 wherein, the flow inside the circuit is always in clockwise direction. 6. A modified micro ventilation anaesthetic circuit as claimed in claim 5 wherein, the inspiratory limb 17 facilitates spontaneous breathing against closed solenoid valve in automatic ventilation. 7. A modified micro ventilation anaesthetic circuit as claimed in claim 6 wherein, the cross connection 25 connects many parts of the circuit, altogether. 8. A modified micro ventilation anaesthetic circuit as claimed in claim 7 wherein, the corrugated tubing are non expanding to reduce wasting during ventilation. 9. A modified micro ventilation anaesthetic circuit as claimed in claim 8 wherein, the unidirectional valves are horizontal flat discs of low weight sitting on a vertical seat under a transparent dome. 10. A modified micro ventilation anaesthetic circuit as claimed in claim 9 wherein, the Y connection piece 9 connects both respiratory limbs, 13 & 17. 11. A micro ventilation anaesthetic circuit as claimed in claim 10 wherein, the circuit is economic and less polluting. 12. A modified micro ventilation anaesthetic circuit as claimed in claim I I wherein, the soda lime absorber is placed down stream of the occluder ( solenoid) valve, in order not to interfere with its function by soda lime particles. 13. A modified micro ventilation anaesthetic circuit as claimed in claim 12 wherein, the alveolar C02 partial pressure is measured by capnography or other available means.

I I Amendments to the claims have been filed as follows CLAIMS LA modified micro ventilation anaesthetic apparatus comprising a double lumen endotracheal tube having a narrow lumen for continuous inspiratory flow and a larger lumen for expiration, said larger lumen b6ng connected to a circuit comprising an inspiratory and expiratory limb being connected at one end to a unidirectional valve; an expiratory valve; a reservoir bag; a soda lime absorber and a solenoid valve.
2. A modified micro ventilation anaesthetic circuit as claimed in claim I, wherein the expiratory valve is placed upstream of the absorber in order to conserve soda lime.
3. A modified micro ventilation anaesthetic circuit as claimed in claim 2, wherein the capacity of the circuit is about 5 litres.
4. A modified micro ventilation anaesthetic circuit as claimed in claim 3), wherein a diversion valve 21 allows the flow to move in one direction, either to the soda lime absorber 20 or to a bypass tube 24.
5. A modified micro ventilation anaesthetic circuit as claimed in claim 4 wherein, the flow inside the circuit is always being in the same direction.

0 off
6. A modified micro ventilation anaesthetic circuit as claimed in claim 5 wherein, the inspiratory limb 17 facilitates spontaneous breathing against closed solenoid valve in automatic ventilation.
7. A modified micro ventilation anaesthetic circuit as claimed in claim 6 wherein, a cross connection 25 connects the bypass tube 24, the inspiratory limb 17, the soda lime absorber 20 and the reservoir bag 27, altogether, to achieve the functions which are mentioned in the description.

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8. A modified micro ventilation anaesthetic circuit as claimed in claim 7 wherein, the inspiratory and expiratory limbs comprise non-expanding, corrugated tubing to reduce waste during ventilation.
9. A modified micro ventilation anaesthetic circuit as claimed in claim 8 wherein, the unidirectional valves are horizontal flat discs of low weight sitting on a vertical seat under a transparent dome.
10. A modified micro ventilation anaesthetic circuit as claimed in claim 9 wherein, a Y connection piece 9 connects both respiratory limbs, 13 & 17.
11. A modified micro ventilation anaesthetic circuit as claimed in claim I I wherein, the soda lime absorber is placed down stream of the occluder ( solenoid) valve, in order not to interfere with its function by soda lime particles.
12. A modified micro ventilation anaesthetic circuit as claimed in claim 12 wherein, the alveolar C02 partial pressure is measured by capnography or other available means.

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