Patent Publication Number: US-2022233793-A1

Title: Gas heater for surgical gas delivery system with gas sealed insufflation and recirculation

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The subject application is a continuation-in-part of U.S. application Ser. No. 17/155,478 filed Jan. 22, 2021, and a continuation-in-part of U.S. application Ser. No. 17/155,572 filed Jan. 22, 2021, the disclosures of which are both herein incorporated by reference in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The subject invention is directed to minimally invasive surgery, and more particularly, to a gas heater for a surgical gas delivery system used for gas sealed insufflation and recirculation during an endoscopic or laparoscopic surgical procedure. 
     2. Description of Related Art 
     Laparoscopic or “minimally invasive” surgical techniques are becoming commonplace in the performance of procedures such as cholecystectomies, appendectomies, hernia repair and nephrectomies. Benefits of such procedures include reduced trauma to the patient, reduced opportunity for infection, and decreased recovery time. Such procedures within the abdominal (peritoneal) cavity are typically performed through a device known as a trocar or cannula, which facilitates the introduction of laparoscopic instruments into the abdominal cavity of a patient. 
     Additionally, such procedures commonly involve filling or “insufflating” the abdominal cavity with a pressurized fluid, such as carbon dioxide, to create an operating space, which is referred to as a pneumoperitoneum. The insufflation can be carried out by a surgical access device, such as a trocar, equipped to deliver insufflation fluid, or by a separate insufflation device, such as an insufflation (veress) needle. Introduction of surgical instruments into the pneumoperitoneum without a substantial loss of insufflation gas is desirable, in order to maintain the pneumoperitoneum. 
     During typical laparoscopic procedures, a surgeon makes three to four small incisions, usually no larger than about twelve millimeters each, which are typically made with the surgical access devices themselves, often using a separate inserter or obturator placed therein. Following insertion, the obturator is removed, and the trocar allows access for instruments to be inserted into the abdominal cavity. Typical trocars provide a pathway to insufflate the abdominal cavity, so that the surgeon has an open interior space in which to work. 
     The trocar must also provide a way to maintain the pressure within the cavity by sealing between the trocar and the surgical instrument being used, while still allowing at least a minimum amount of freedom of movement for the surgical instruments. Such instruments can include, for example, scissors, grasping instruments, and occluding instruments, cauterizing units, cameras, light sources and other surgical instruments. Sealing elements or mechanisms are typically provided on trocars to prevent the escape of insufflation gas from the abdominal cavity. These sealing mechanisms often comprise a duckbill-type valve made of a relatively pliable material, to seal around an outer surface of surgical instruments passing through the trocar. 
     SurgiQuest, Inc., a wholly owned subsidiary of ConMed Corporation has developed unique gas sealed surgical access devices that permit ready access to an insufflated surgical cavity without the need for conventional mechanical valve seals, as described, for example, in U.S. Pat. Nos. 7,854,724 and 8,795,223. These devices are constructed from several nested components including an inner tubular body portion and a coaxial outer tubular body portion. The inner tubular body portion defines a central lumen for introducing conventional laparoscopic or endoscopic surgical instruments to the surgical cavity of a patient and the outer tubular body portion defines an annular lumen surrounding the inner tubular body portion for delivering insufflation gas to the surgical cavity of the patient and for facilitating periodic sensing of abdominal pressure. 
     SurgiQuest has also developed multimodal surgical gas delivery systems for use with the unique gas sealed access devices described above. These gas delivery systems, which are disclosed for example in U.S. Pat. Nos. 9,199,047 and 9,375,539 have a first mode of operation for providing gas sealed access to a body cavity, a second mode of operation for performing smoke evacuation from the body cavity, and a third mode of operation for providing insufflation gas to the body cavity. 
     Intraoperative hypothermia can occur in laparoscopic surgical procedures, resulting in postoperative complications and prolonged recovery time. Active warming methods used to prevent intraoperative hypothermia include forced air warming systems, warmed ventilator circuits and warmed intravenous and irrigation fluids. The use of warmed surgical gas to establish pneumoperitoneum during laparoscopy has been associated with reduced incidence of intraoperative hypothermia. 
     Indeed, the SurgiQuest multimodal gas delivery system described above employs a heating mechanism in the form of a thick-walled brass fitting with an RF resistor that transfers heat to surgical gas as it enters the system from a gas source. However, the heat transfer volume of that fitting is relatively small and the transit time through the fitting to facilitate heat transfer to the gas flow is relatively short. Thus, an improved gas heater without these limitations would be beneficial. 
     SUMMARY OF THE DISCLOSURE 
     The subject invention is directed to a new and useful gas heater for a multimodal surgical gas delivery system used for gas sealed insufflation and recirculation during an endoscopic or laparoscopic surgical procedure. The gas heater includes an elongated tubular body defining an interior flow passage having an inlet port for receiving insufflation gas from a gas source and an outlet port for delivering heated insufflation gas to an insufflation manifold. The tubular body may be formed from a material that facilitates UVC sterilization of the gas flowing therethrough, such as, for example, UVC transparent quartz glass. 
     A dielectric support is positioned within the interior flow passage of the tubular body, and a resistive element is operatively associated with the dielectric support for transferring heat to insufflation gas flowing through the tubular body from the inlet port to the outlet port. In one embodiment of the subject invention, the dielectric support is an elongated support beam that has a ribbed exterior surface and the resistive element is wrapped around the ribbed exterior surface of the support beam. In another embodiment of the subject invention, the dielectric support is an elongated support tube and the resistive element is partially wrapped around an exterior surface of the support tube and partially woven transversely through an interior bore of the support tube. 
     The dielectric support is preferably formed from a ceramic material and the resistive element is preferably formed from a nickel based alloy. The gas heater further includes a first sensing port for accommodating a first heat sensor adjacent the inlet port to measure an inlet gas temperature and a second sensing port for accommodating a second heat sensor adjacent the outlet port to measure an outlet gas temperature. The gas heater also includes electrical couplings for connecting the resistive element to an electrical energy source. 
     The subject invention is also directed to a surgical gas delivery system that includes a source of insufflation gas, a pressure regulator for receiving insufflation gas from the source, an insufflation manifold for receiving pressure regulated insufflation gas from the pressure regulator for delivery to one or more surgical access ports communicating with the gas delivery system, and a gas heater as described above for heating the insufflation gas received by the insufflation manifold. The gas delivery system further includes a gaseous sealing manifold for communicating with a gas sealed access port and wherein the outlet port of the gas heater communicates with the gaseous sealing manifold in parallel with the insufflation manifold. 
     These and other features of the gas heater and the gas delivery system of the subject invention will become more readily apparent to those having ordinary skill in the art to which the subject invention appertains from the detailed description of the preferred embodiments taken in conjunction with the following brief description of the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those skilled in the art will readily understand how to make and use the gas heater and gas delivery system of the subject invention without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to the figures wherein: 
         FIG. 1  is a schematic diagram of the multi-modal gas delivery system of the subject invention, which includes a gaseous sealing manifold for communicating with a gas sealed access port and an insufflation manifold for communicating with the gas sealed access port and with a valve sealed access port, wherein the gas delivery system includes a gas heater for transferring heat to surgical gas entering the system from a gas source; 
         FIG. 2  is a perspective view of the gas heater of the subject invention; 
         FIG. 3  is a top plan view of the gas heater shown in  FIG. 2 ; 
         FIG. 4  depicts the dielectric support beam and resistive element of the gas heater shown in  FIG. 2 ; 
         FIG. 5  is a perspective view of another embodiment of the gas heater of the subject invention; 
         FIG. 6  is a side elevational view of the gas heater shown in  FIG. 5 ; 
         FIG. 7  is a cross-sectional view taken along line  7 - 7  of  FIG. 6 ; 
         FIG. 8  is a cross-sectional view taken along line  8 - 8  of  FIG. 6 ; 
         FIG. 9  is an end view of the gas heater shown in  FIG. 5 ; 
         FIG. 10  is a cross-sectional view taken along line  10 - 10  of  FIG. 9 ; 
         FIG. 11  is a partial perspective view of the dielectric support tube of the gas heater shown in  FIG. 5 , wherein the resistive element is located internally and oriented substantially transverse to the direction of net gas flow through the gas heater; and 
         FIG. 12  is an end view of the section of the dielectric support tube shown in  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings wherein like reference numerals identify similar structural elements and features of the subject invention, there is illustrated in  FIG. 1  a new and useful multi-modal surgical gas delivery system  10  that is adapted and configured for gas sealed insufflation, recirculation and smoke evacuation during an endoscopic or laparoscopic surgical procedure. The multi-modal surgical gas delivery system  10  of the subject invention includes a gaseous sealing manifold  110  for communicating with a gas sealed access port  20  and an insufflation manifold  210  for communicating with the gas sealed access port  20  and with a valve sealed access port  30 . 
     The gas sealed access port  20  is of the type disclosed in commonly assigned U.S. Pat. No. 8,795,223, which is incorporated herein by reference. The gas sealed access port  20  is adapted and configured to provide gas sealed instrument access to a body cavity, while maintaining a stable pressure within the body cavity (e.g., a stable pneumoperitoneum in the peritoneal or abdominal cavity). In contrast, the valve sealed access port  30  is a conventional or standard trocar, for providing access to a body cavity through a mechanical valve seal, such as, for example, a duckbill seal, septum seal or the like. Depending upon the requirements of a particular surgical procedure, the multi-modal gas delivery system  10  can be utilized with either the gas sealed access port  20 , the valve sealed access port  30  or with both access ports  20 ,  30  at the same time. 
     The gas delivery system  10  further includes a compressor or positive pressure pump  40  for recirculating surgical gas through the gas sealed access port  20  by way of the gaseous sealing manifold  110 . The compressor  40  is preferably driven by a brushless DC (direct-current) motor, which can be advantageously controlled to adjust gas pressure and flow rates within the gas delivery system  10 , as disclosed for example in commonly assigned U.S. Pat. No. 10,702,306, which is incorporated herein by reference. Alternatively, the compressor  40  can be driven by an AC motor, but a DC motor will be relatively smaller and lighter, and therefore more advantageous from a manufacturing standpoint. 
     An intercooler and/or condenser  50  is operatively associated with the compressor  40  for cooling or otherwise conditioning gas recirculating through the gaseous sealing manifold  110 . A UVC irradiator  52  is operatively associated with the intercooler or condenser  50  for sterilizing gas recirculating through the internal flow passages  54  formed therein by way of the compressor  40 . In addition, the UVC irradiator  52  is intended to sterilize the interior surfaces of the gas conduits or flow passages  54  through which the gas flows within the intercooler/condenser  50 . 
     The UVC irradiator preferably includes at least one LED light source or a florescent light source that is adapted and configured to generate UVC radiation at a wavelength of about between 240-350 nm, and preferably about 265 nm. This ultraviolet light at such a wavelength can sterilize viral, bacterial and microbial bodies within the gas conduits of the system, and can reduce coronavirus including SARS-COV-2. 
     Preferably, compressor  40 , intercooler/condenser  50 , gaseous sealing manifold  110  and insufflation manifold  210  are all enclosed within a common housing, which includes a graphical user interface and control electronics, as disclosed for example in commonly assigned U.S. Pat. No. 9,199,047, which is incorporated herein by reference. 
     The gas delivery system  10  further includes a surgical gas source  60  that communicates with the gaseous sealing manifold  110  and the insufflation manifold  210 . The gas source  60  can be a local pressure vessel or a remote supply tank associated with a hospital or healthcare facility. Preferably, gas from the surgical gas source  60  flows through a high pressure regulator  65  and a gas heater  70  before it is delivered to the gaseous sealing manifold  110  and the insufflation manifold  210 . Preferably, the high pressure regulator  65  and the gas heater  70  are also enclosed with the compressor  40 , intercooler  50 , gaseous sealing manifold  110  and insufflation manifold  210  in the common housing. Two embodiments of the gas heater  70  will be described in greater detail below with reference to  FIGS. 2 through 12 . 
     The gas delivery system  10  further includes a first outlet line valve (OLV1)  212  that is operatively associated with the insufflation manifold  210  for controlling a flow of insufflation gas to the valve sealed access port  30  and a second outlet line valve (OLV2)  214  that is operatively associated with the insufflation manifold  210  for controlling a flow of insufflation gas to the gas sealed access port  20 . 
     In accordance with a preferred embodiment of the subject invention, the first and second outlet line valves  212 ,  214  of insufflation manifold  210  are proportional valves that are configured to dynamically alter or otherwise control the outflow of insufflation gas to the access ports  20 ,  30  to match volume fluctuations that may arise in a patient&#39;s body cavity as they occur. The first and second proportional outlet line valves  212 ,  214  provide the gas delivery system  10  with fine control of insufflation gas flow rate to achieve stable flow rates at lower pressure, reduce pressure oscillation and eliminate pneumatic hammer. 
     Because the first and second proportional outlet line valves  212 ,  214  are proximal to the patient where flow friction losses are relatively low, the gas delivery system  10  is able to measure peritoneal pressures accurately. Moreover, the use of proportional outlet line valves for this purpose is uniquely possible here, because there is constant gas recirculation throughout the gas delivery system  10 , either by way of closed loop smoke evacuation or by way of the gas sealed access port  20 . 
     Proportional valves allow for infinitely variable gas flow adjustment between a minimum flow state and a maximum flow state. Given that some volume changes in a patient&#39;s body cavity, such as breathing, are expected and consistent, by employing proportional outlet line valves, the insufflation manifold  210  is able to dynamically alter the gas flow to the body cavity to inverse the expected volume changes, resulting in a neutral effect on the pressure inside the cavity. 
     An additional benefit of using proportional valves for controlling the outflow of insufflation gas from manifold  210  is a reduction in response time, as compared to that of a solenoid valve. A solenoid valve operates by applying energy to coils, which produces an electromagnetic force that moves a piston. However, the energizing of the coils takes some amount of time, introducing a delay between a commanded action and the physical movement of the piston. In contrast, proportional valves, as employed in the gas delivery system  10  of the subject invention, do not have an energization delay in general, and so they have an improved response time as compared to solenoid valves. 
     The insufflation manifold  210  further includes a first patient pressure sensor (PWS1)  222  downstream from the first outlet line valve  212  and a second patient pressure sensor (PWS1)  224  downstream from the second outlet line valve  214 . These two patient pressure sensors are used to measure abdominal pressure to control outlet line valves  212 ,  214 , respectively. Two other pressure sensors are located upstream from the outlet line valves  212 ,  214 , and are labeled as DPS1 and DPS2. These two pressure sensors are situated within a venturi to measure a pressure differential that is used to infer a total gas flow rate from the insufflation manifold  210  to the patient&#39;s body cavity. 
     A primary proportional valve (PRV)  216  is also operatively associated with insufflation manifold  210  and it is located upstream from the first and second outlet line valves  212 ,  214  to control the flow of insufflation gas to the first and second outlet line valves  212 ,  214 . Proportional valve  216  functions to maintain an intermediate pressure within the insufflation manifold  210  (as the central node in the LPU) at a constant pressure between 1 and 80 mmHg, dependent on the system operating mode. The opening of PRV  216  can be indirectly initiated by any of the following actions: patient respiration, gas leakage downstream of PRV  216 , or the opening of the safety valve LSV  227  or ventilation valve VEV  228 , i.e. any event that causes an intermediate pressure to drop. In the system. LSV  227  and VEV  228  are described in more detail below. 
     The gaseous sealing manifold  110  also includes a high pressure gas fill valve (GFV)  112  that is operatively associated with an outlet side of the compressor  40 . GFV  112  is adapted and configured to control gas delivered into the gaseous sealing manifold  110  from the source of surgical gas  60 . Preferably, the gas fill valve  112  is a proportional valve that is able to dynamically control surgical gas delivered into the gaseous sealing manifold  110 . 
     The gaseous sealing manifold  110  also includes a smoke evacuation valve (SEV)  114  that is operatively associated with an outlet side of the compressor  40  for dynamically controlling gas flow between the gaseous sealing manifold  110  and the insufflation manifold  210  under certain operating conditions, such as, for example, when the gas delivery device  10  is operating in a smoke evacuation mode. Preferably, the smoke evacuation valve  114  is a proportional valve. 
     A bypass valve (SPV)  116  is positioned between an outlet side of the compressor  40  and an inlet side of the compressor  40  for controlling gas flow within the gaseous sealing manifold  110  under certain operating conditions. Preferably, the bypass valve  116  is a proportional valve, which is variably opened to establish and control the gaseous seal generated within gas sealed access port  20 . Moreover, bypass valve  116  controls gas flow rate to the gaseous seal using feedback from pressure sensors  122 ,  124 , described in further detail below. 
     The gaseous sealing manifold  110  also includes an air ventilation valve (AVV)  118 , which is operatively associated with an inlet side of the compressor  40  for controlling the entrainment of atmospheric air into the system  10  under certain operating conditions. For example, AVV  118  will permit the introduction of atmospheric air into the gaseous sealing circuit to increase the air mass (i.e., the standard volume) within the circuit. The thermodynamics of clinical use conditions can cause a loss of standard volume within the gas circuit. The ventilation valve  118  permits the gas delivery system  10  to make up for this lost volume, in order to ensure that pump pressure and flow rates are sufficient to maintain the gaseous seal within the gas sealed access port  20 . The ventilation valve  118  can also be opened to reduce the vacuum side pressure in the gas seal circuit. 
     An overpressure relief valve (ORV)  120  is operatively associated with an outlet side of the compressor  40  for controlling a release of gas from the system  10  to atmosphere under certain operating conditions. Preferably, the overpressure relief valve  120  is a proportional valve that is opened to reduce the positively pressurized side of the gas seal circuit, especially in the event of an emergency, such as a loss of power to the gas delivery system  10 . The normally open configuration of relief valve  120  reduces the risk of over-pressurization of the patient cavity upon loss of power to that valve. 
     A first pressure sensor (RLS)  122  is operatively associated with an inlet side of the compressor  40  and a second pressure sensor (PLS)  124  is operatively associated with an outlet side of the compressor  40 . These pressure sensors  122 ,  124  are situated to have unobstructed and minimally restricted commutation with the patient&#39;s abdominal cavity in order to continuously and accurately measure cavity pressure. The signals from these two pressure sensors  122 ,  124  are employed by a controller of the gas delivery system  10  to modulate the opening of the two outlet line valves  212  and  214 , to control the patient cavity pressure. 
     In addition, the gaseous sealing manifold  110  includes a gas quality sensor  126  that is operatively associated with an outlet side of the compressor  40 . The gas quality sensor monitors the level of oxygen in the recirculation circuit, which corresponds to a concentration of CO 2  in the body cavity of a patient, as disclosed in U.S. Pat. No. 9,199,047. 
     A first blocking valve (BV1)  132  is operatively associated with an outlet flow path of the gaseous sealing manifold  110  and a second blocking valve (BV2)  134  is operatively associated with an inlet flow path to the gaseous sealing manifold  110 . The blocking valves  132 ,  134  are employed during a self-test prior to a surgical procedure, as disclosed in U.S. Pat. No. 9,199,047. It is envisioned that the first and second blocking valves  132 ,  134  could be are mechanically actuated or pneumatically actuated. 
     A first filter element  142  is positioned downstream from the first blocking valve  132  for filtering pressurized gas flowing from the compressor  40  to the gas sealed access port  20 , and a second filter element  144  is positioned upstream from the second first blocking valve  134  for filtering gas returning to the compressor  40  from the gas sealed access port  20 . Preferably, the filter elements  142 ,  144  are housed within a common filter cartridge, as disclosed for example in U.S. Pat. No. 9,199,047. 
     The first and second blocking valves  132 ,  134  communicate with a blocking valve pilot (BVP)  226  that is included within with the insufflation manifold  210 . Preferably, the blocking valve pilot  226  is a solenoid valve. It is envisioned that BVP  226  could be fed from the compressor outlet as shown or from a gas source such of surgical gas or air. The insufflation manifold  110  further includes a pressure sensor (PMS)  225  located downstream from the primary proportional valve  216  and upstream from the outlet line valves  212 ,  214 . The two outlet line valves are opened to introduce insufflation gas to the patient&#39;s body cavity by way of the access ports  23 ,  30 . This introduction of gas has the effect of increasing pressure within the body cavity. Additionally, the outlet line valves  212 ,  214  can be opened in conjunction with air ventilation valve  228  to release gas from the body cavity, having the effect of desufflation and reduction of cavity pressure. 
     The insufflation manifold  210  further includes a low pressure safety valve (LSV)  227  downstream from the primary proportional valve  216  and upstream from the first and second outlet line valves  212 ,  214  for controlling a release of gas from the system  10  to atmosphere under certain operating conditions. LSV  227  is a purely mechanical valve that functions to limit the maximum intermediate pressure within the manifold  210  or LPU (Low Pressure Unit) in the event of a power interruption, a pressure controller malfunction or if a valve located upstream from the LSV sticks in an open position. 
     In addition, a ventilation exhaust valve (VEV)  228  is positioned downstream from the primary proportional valve  216  and upstream from the outlet line valves  212 ,  214  for controlling a release of gas from the system  10  to atmosphere under certain operating conditions. The ventilation exhaust valve  228  is a preferably a proportional valve that is opened to desufflate or otherwise reduce patient cavity pressure. Additionally, VEV  228  can be opened to reduce intermediate pressure within the LPU. 
     A filter element  242  is positioned downstream from the first outlet line valve  212  for filtering insufflation gas flowing from the insufflation manifold  210  to the valve sealed access port  30 . Another filter element  244  is positioned downstream from the second outlet line valve  224  for filtering insulation gas flowing from the insufflation manifold  210  to the gas sealed access port  20 . Preferably, filter element  244  is housed with filter elements  142  and  144  in a common filter cartridge, while filter element  242  is separately located. Referring now to  FIGS. 2 and 3 , there is illustrated the gas heater  70  of the subject invention, which includes an elongated tubular body  72  defining an interior flow passage  74  having an inlet port  76  for receiving insufflation gas from the gas source  60  and an outlet port  78  for delivering heated insufflation gas to the gaseous sealing manifold  110  and the insufflation manifold  210 , as shown schematically in  FIG. 1 . The tubular body  72  is formed from a UVC transparent quartz glass so as to permit an external UVC source (not shown) to sterilize the insufflation gas passing through the heater  70 . The inlet port  76  and outlet port  78  extend perpendicular to the longitudinal axis of the tubular body  72 . 
     A ribbed dielectric support beam  80  extends coaxially through the interior flow passage  74  of the tubular body  72 , and a resistive element  82  is wrapped around or otherwise associated with the ribbed support beam  80 , as shown in  FIG. 4 , for transferring heat to insufflation gas flowing through the tubular body  72  from the inlet port  76  to the outlet port  78 . The elongated tubular body  72  provides a greater amount of heat transfer volume and longer transit time to facilitate heat transfer from the resistive element  82  to the gas flow, as compared to the prior art resistive heater described hereinabove. 
     The gas flow rate through the tubular body  72  of heater  70  is about 50 slpm but it can range between 0 and 100 slpm. The maximum heat power transfer into the gas flowing through the tubular body  72  of heater  70  is about 190 Watts, but it could range between 25 and 1000 Watts depending on the dimensional scale of the heater assembly. 
     In accordance with a preferred embodiment of the subject invention, the dielectric support beam  80  is formed from at least in part from a ceramic material. Alternatively, the support beam  80  can be formed from a ceramic-thermoset polymer composite or the like. The resistive element is  82  is preferably formed from a nickel based alloy, such as, for example Nichrome or the like. Electrical couplings or conductors  88  are associated with the support beam  80  for connecting the resistive element  82  to an electrical energy source, as shown in  FIG. 4 . 
     While the resistive element  82  is illustrated, by way of example, as a resistive wire, it is envisioned that the resistive element  82  could take the form of foil, laminates, printed inks, and/or wire mesh. In any case, the total end-to-end resistance of the resistive element  82  is preferably about 3 ohms, but it could range between 0.1 ohm and 100 ohms. The resistance per unit length of the resistive element  82  is preferably about 1 ohm per foot, but it could range between 1 milli-ohm per foot and 1 kilo-ohm per foot. It is further envisioned that the resistive element  82  could be comprised of multiple resistive elements that are connected in series, in parallel, or in combinations thereof. 
     Referring back to  FIGS. 2 and 3 , the tubular body  72  of the gas heater  70  includes a first sensing port  84  adjacent the inlet port  76  for accommodating a first heat sensor (not shown) to measure an inlet gas temperature and a second sensing port  86  adjacent the outlet port  78  for accommodating a second heat sensor (not shown) to measure an outlet gas temperature. The first sensing port  76  and the second sensing port  78  are aligned with the longitudinal axis of the tubular body  72 . 
     Referring now to  FIGS. 5 through 10 , there is illustrated another embodiment of the gas heater of the subject invention, which is designated generally by reference numeral  170 . Gas heater  170  includes an elongated tubular body  172  supported between two end caps  190  and  192 . The tubular body  172  of gas heater  170  is preferably formed from UVC transparent quartz glass and it defines an internal flow passage  174  (see  FIG. 7 ). The two end caps  190  and  192  are joined or otherwise fastened together by four elongated spacer struts  194   a - 194   d.    
     An inlet port  176  in the form of a right-angled connective fitting is operatively associated with end cap  190  and an outlet port  178  in the form of an oppositely directed right-angled connective fitting is operatively associated with end cap  192 . As best seen in  FIGS. 7 and 10 , the inlet port  176  communicates with an inlet flow passage  175  formed in end cap  190 , which communicates with the internal flow passage  174  of tubular body  172  through a spacer ring  177 . Similarly, the outlet port  178  communicates with an outlet flow passage  195  formed in end cap  192 , which communicates with the internal flow passage  174  of tubular body  172  through a spacer ring  197 . 
     With continuing reference to  FIGS. 7 and 10 , an O-ring  202  is seated in end cap  190  for sealingly engaging the outer surface of the tubular body  172  disposed therein, and another O-ring  204  is seated in end cap  192  for sealingly engaging the outer surface of the tubular body  172  disposed therein. A dielectric support tube  180  extends coaxially through the interior flow passage  174  of tubular body  172 . The support tube  180  is formed from a ceramic material, such as for example, a ceramic-thermoset polymer composite or the like. 
     An inlet end of support tube  180  is retained within end cap  190  by a bushing  206  and an O-ring  203  seated on bushing  206 . An outlet end of support tube  180  is retained within end cap  192  by a bushing  208  and an O-ring  205  seated on bushing  208 . Spacer rings  177  and  197 , as well as O-rings  203  and  205  act as thermal insulators to limit heat transfer between the support tube  180  and the end caps  190  and  192  of gas heater  170 . 
     A resistive element  182  is operatively associated with the support tube  180 . The resistive element is  182  is preferably formed from a nickel based alloy, such as, for example Nichrome or the like. As best seen in  FIGS. 8, 11 and 12 , the resistive element  182  is located both on the exterior surface of the support tube  180  and within the interior bore  185  of the support tube  180  spaced away from interior wall thereof. 
     More specifically, the resistive element  182  is wrapped partially around the exterior surface of the support tube  180  and woven through the interior bore  185  of the support tube  180 . In this orientation, the resistive element  182  is substantially transverse to the direction of net gas flow through the tubular body  172  of the gas heater  170 . This facilitates heat transfer between the resistive element  182  and the gas flowing through the tubular body  172  by converting laminar flow into turbulent flow. 
     A first sensing probe  184  is associated with end cap  190 , located adjacent the inlet port  176 , for measuring an inlet gas temperature. A second sensing probe  186  is associated with end cap  192 , located adjacent the outlet port  178 , for measuring an outlet gas temperature. The first and second sensing probes  184 ,  186  extend perpendicular to the longitudinal axis of the tubular body  172 , and intersect the bore  185  of tubular support beam  180 , as best seen in  FIG. 10 . A first electrical coupling  188  is associated with end cap  190  and a second electrical coupling  198  is associated with end cap  192 . Electrical coupling  188  and  198  are adapted and configured to provide a connection between the resistive element  182  and an electrical power source, by way of appropriate conductive wires (not shown). 
     While the gas delivery system and gas heater of the subject disclosure has been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.