Unit for insufflating and cleaning gas

A insufflation unit for distending a body cavity such as a uterus which is to be examined or treated endoscopically has a gas control circuit which connects a gas supply unit to the endoscope via a flowmeter, a shut-off valve and a filter. Associated with this gas control circuit is an extractor circuit which comprises a pump whose suction end is coupled up to the output of the flowmeter. A pressure-measuring transducer logs the pressure at the suction end of the pump and its measurements, together with those from the flowmeter, are made use of in analyzer electronics by switching off the pump before a pressure likely to put the patient at risk occurs should there be a fault in the extractor circuit.

BACKGROUND OF THE INVENTION 
(a) Field of the Invention 
This invention relates to an insufflation unit for use in endoscopic 
operations and in particular in human medicine, in which a gas which is 
introducible into a body cavity such as the uterus from a gas supply 
device via an instrument channel in the endoscope is monitored for 
pressure and flow rate and can be fed through a filter-equipped extractor 
circuit to filter out smoke and/or vapor. 
(b) Description of the Prior Art 
Units of this kind are needed to distend in the requisite manner a body 
cavity which is to be examined and treated in the course of an endoscopic 
operation. At the same time it is necessary that the pressure inside the 
body cavity should be kept as constant as possible during the operation. 
It is known from DE-OS-3739003 (U.S. Pat. No. 5,013,294) to provide an 
insufflation unit with two flow paths and which is able constantly to 
compensate for minor losses of gas. Larger losses of gas, which may be be 
caused by a change of instruments or the like, can quickly be compensated 
for by changing over to the second flow path before the preselected lower 
pressure limit is reached. It is also ensured that, should the preselected 
upper pressure limit be overrun, the supply line and pump and any other 
ancillary devices which are connected to the outlets and operated by the 
analyser electronics are switched off and no more gas is fed into the body 
cavity. 
DE-PS 3329784 (U.S. Pat. No. 4,538,594) discloses another unit of this kind 
which is suitable for use with coagulating instruments such as lasers. In 
this case there is a requirement that the smoke produced during the 
coagulation should be withdrawn as quickly as possible because it hampers 
the visual monitoring of the operation, and the withdrawal process must be 
carried out without the pressure in the body cavity changing. In the 
present prior art device this is done by extracting the smoke together 
with secretion and insufflation gas, the gas being cleaned by a filter and 
fed back into the body cavity in closed circuit. 
Known insufflation units which have high gas flow-rates to produce the 
desired fast correction of pressure are not suitable for endoscopy in 
small body cavities like the uterus because in this case it is important 
for the maximum infeed of gas which is acceptable under the given 
physiological conditions not to be exceeded. 
The main object of the present invention is to overcome the disadvantage 
that the said insufflation units are not suitable for operations of the 
kind mentioned hereinabove. 
SUMMARY OF THE INVENTION 
To this end, the present invention consists in an insufflation unit for use 
in endoscopic operations and in particular in human medicine, in which a 
gas which is introducible into a body cavity such as the uterus from a gas 
supply device via an instrument channel in the endoscope is monitored for 
pressure and flow rate and can be fed through a filter-equipped extractor 
circuit to filter out smoke and/or vapor characterised in that, on its way 
to the instrument channel, the gas flows through a flowmeter, a shut-off 
valve and a filter, in that the extractor circuit comprises a pump whose 
suction end is connected between the filter and shut-off valve and which 
is connected to a further instrument channel via a sterile filter, and in 
that the monitoring is performed by analyser electronics which obtain 
their control data from a pressure-measuring transducer connected to the 
suction end of the pump and from the said flowmeter and which control the 
shut-off valve and the pump by comparing the actual value for pressure 
with a preset desired value. 
The advantages achievable by means of the present invention lie in 
particular in the fact that, as well as being able to provide the required 
distension of the body cavity and hold the pressure constant in the bubble 
of gas so produced, the unit can also detect faults in the extractor 
circuit and react to them so that pressures which put the patient at risk 
cannot arise. What is more, units constructed according to the invention 
are also capable of preventing an insufflation if the gas throughput of 
the unit connected up for an operation is unsuitable, i.e. if a unit whose 
possible flow-rates are rather high is connected up.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawing, the block circuit diagram includes a gas control 
circuit which, via a flowmeter 2, a shut-off valve 3, a filter 4 and a 
connecting nozzle 6, connects an appropriate gas supply unit 1 to an 
instrument channel, connected to the connecting nozzle, in an endoscope 5. 
The block circuit diagram further includes an extractor circuit having a 
pump 7 driven by a motor 8 whose suction end 9 is connected to the outlet 
of the shut-off valve 3 and to the filter 4 and which is coupled up via a 
sterile filter 11 to an instrument channel 10 in the endoscope 5, being so 
coupled via the outer shell of the light guide of a laser unit 12, which 
outer shell surrounds the light guide at a distance. The pressure at the 
suction end 9 of the pump 7 is logged by a pressure-measuring transducer 
13 which, like the flowmeter 2, transmits its measurement data to analyser 
electronics 14 which compare the measurements with the value preset from a 
setting device 15, the outputs of the analyser electronics 14 being 
connected to the shut-off valve 3 and the motor 8 of the pump 7. 
The flowmeter 2 monitors flow to a limiting value and controls the shut-off 
valve 3 via the analyser electronics 14. For this purpose a desired/actual 
comparsion is carried out in the analyser electronics 14 and the shut-off 
valve 3 is closed if the permitted flow-rate is exceeded. To distend a 
body cavity a flow of gas takes place through the shut-off valve 3. With 
the pump still off, this gas passes through filter 4 and into body cavity 
16, such as a uterus. If a leak occurs in the gas circuit as the process 
is getting under way then, due to the low output capacity of the unit, the 
pressure does not rise to the preset level and the pump cannot be switched 
on. When the pressure preselected with the setting device 15 is reached, 
shut-off valve 3 is actuated and hence the flow of gas from the gas supply 
unit 1 is stopped. If use is then made of the laser unit 12, pump 7 can be 
switched on to extract the smoke produced. The pump cannot, though, be 
switched on if the preselected pressure has not been reached. 
In this way the smoke is sucked out of the body cavity 16 with the gas and 
filtered out in filter 4 and the cleaned gas is then pumped back into body 
cavity 16 via the sterile filter 11 which is fitted to prevent the 
transmission of bacteria. The desired value preset for pressure should be 
between 40 mbar and 200 mbar. If the pressure drops below the preselected 
level by approximately 20 mbar, the circulation of the gas stops until the 
gas supply unit 1 has restored the pressure to the preset level. The 
pressure is measured by the pressure-measuring transducer 13 at the 
suction end 9 of pump 7, because at this point downstream of filter 4 and 
the large flow cross-section in the endoscope 5, given the filter 
throughout aimed at of 500 to 1000 ml/min, there is no substantial 
difference from the pressure in the body cavity. This ensures that there 
is a closed gas-circuit because if there are any losses of gas in the 
circuit, the change from the pre-selected level is sensed by the 
pressure-measuring transducer 13. If pressure were measured on the 
delivery side of pump 7, the ducts, which are generally small in 
cross-section (light guide outer shell) would cause an incorrect pressure 
reading. Leaks in the connecting lines or the endoscope 5 cause a drop in 
pressure in the extraction circuit which is detected by the analyser 
electronics 14 and causes the pump 7 to be switched off. Blockage of a 
rigid line or linking of a flexible one causes the pressure to drop below 
the set level and is detected as a fault in the circuit. If there is no 
gas supply, the intake of air is ruled out because the pump is then off. 
The flowmeter 2, analyser electronics 14 and shut-off valve 3 may also be 
so designed that if a CO.sub.2 supply unit with a higher flow-rate is 
going to be used, the flow-rate can be held down to the maximum rate 
permissible for the application. If endoscope 5 has enough connections, 
there is no need for the outer shell of the light guide to be brought into 
play to feed the gas into the gas circuit. The circuit can then be set up 
through other connections and the light guide can be inserted into a 
separate instrument channel through a suitable adapter. 
Whilst a particular embodiment of the invention has been described it 
should be appreciated that variations and modifications may be made 
without departing from the scope of the invention.