Breath gas analysis is commonly performed to provide information related to a patient's condition. An example of a gas analysis often performed is capnography using an analyzer called a capnograph. Capnography is the monitoring of the time dependent respiratory carbon dioxide (CO2) concentration, which may be used to directly monitor the inhaled and exhaled concentration of CO2, and indirectly monitor the CO2 concentration in a patient's blood. Capnography may provide information about CO2 production, pulmonary (lung) perfusion, alveolar ventilation (alveoli are hollow cavities in the lungs in which gas exchange is being performed) and respiratory patterns. Capnography may also provide information related to a patient's condition during anaesthesia, for example by monitoring the concentration of CO2 from anaesthesia breathing circuit and ventilator. More information regarding capnography may be found in http://www.capnography.coin/ and http://www.nda.ox.ac.uk/wfsa/html/u11/u1107_01.htm, which are herein incorporated by reference in its entirety.
In breath analysis systems, for example capnography, breath gas can be sampled either by a mainstream or a sidestream analyzer. In mainstream analyzers the sample chamber is positioned within the patient's gas stream near the patient's end of the breathing system. This arrangement is normally heavier and more cumbersome.
In sidestream analyzers gas is drawn from the breathing system by a tube. The tube, which may be connected to an adaptor near the patient's end of the breathing system, delivers the gas to a sampling place (such as a sampling chamber). There are several elements that are generally common to sidestream breath analysis systems (such as capnographs) including, a monitor that continuously samples and monitors the CO2 in a patients breath, airway tube(s) and sampling line(s) which may be flexible tube(s) having narrower diameter(s) than the airway tube(s), and are adapted used to connect between the patient airway tube(s) and the distant analyzer, such as the capnograph monitor. Along this tube, the patient's breath is continuously sampled.
It is usually preferable that the sampling line is clear of liquids in the fluid sample at all times, in order to permit continuous, non-interfered monitoring. Such liquids are common in patient sampling systems, and have several origins, for example:                condensed out liquids from the highly humidified air provided to and exhaled from the patient. These liquids typically accumulate both in the patient airway and in the sampling line tubing;        secretions from the patient, typically found in the patient airway; and        medications or saline solution provided to the patient during lavage, suction and nebulization procedures.        
Condensed out liquids generally refer to water that condenses out from the humidity (the water vapor in a air or in other gas) in the sampling tubes. Condensed out liquids is a major problem commonly hindering breath analyses, particularly sidestream capnography. The internal humidity levels in the tubes are high especially in proximity to the breath collection area since the exhaled and inhaled breath is humid and relatively warm. This is also the case in intubated patients who are generally artificially ventilated with gas (for example, air) having up to 100% humidity at a temperature normally above ambient temperature (for example, about 34° C.), depending on the airway humidification system and patient needs. The humidity (water vapors) often condenses on the tube particularly as the tube is extended farther from the breath collection area due to the temperature decreases.
Several methods have been developed in order to keep the sampling line free of liquids such as those mentioned above, particularly moisture. Some methods are designed to prevent liquids from entering the sampling line (for example, as described in U.S. Pat. No. 5,857,461) and some are designed to remove such liquids if they entered the sampling line or were created in it.
Several solutions have been developed in order to reduce the liquid quantity in the sampling line. Though these solutions have helped in reducing the quantity of low viscosity liquids which enter the sampling line, they have not eliminated the possibility of thick secretions clogging the sampling tubing and its input ports.
Secretions, coughed up by the patient are often thrown at a high speed towards the sampling input ports which are normally positioned at the center of the airway for optimal sampling. Therefore, these sampling ports are often blocked, thereby requiring a user or medical staff to open the patient airway, a condition that one would like to prevent.
There is thus a need to develop methods and apparatuses for reducing the quantity of liquids which reach the sampling line, preferably by preventing liquids from reaching it.