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PubMed1997

Helium and oxygen treatment of severe air-diving-induced neurologic decompression sickness.

BACKGROUND: The use of helium and oxygen recompression treatment of neurologic decompression sickness (DCS) has several theoretical advantages over the traditionally used air and oxygen recompression tables that have been confirmed by findings from recent animal experiments. OBJECTIVES: To evaluate the outcome of patients with neurologic DCS who had been treated with a helium-oxygen protocol and to compare it with that of a retrospective control group that was treated with air-oxygen tables. DESIGN: The study and control groups included 16 and 17 diving casualties, respectively. The severity of neurologic DCS was estimated according to a 9-point scale weighting motor, sensory, and sphincter control functions. The study group was treated with a helium-oxygen decompression protocol, and the control group was treated with the US Navy air-oxygen Table 6 or 6A. Persistent residual dysfunction was treated in both groups with daily hyperbaric oxygen sessions, at 2.5 absolute atmospheres for 90 minutes, until no further clinical improvement was noted. SETTING: The Israel Naval Medical Institute (Israel's national hyperbaric referral center), Haifa. RESULTS: Significant clinical score increments were found for both the helium-oxygen- and air-oxygen-treated groups: 2.8 +/- 2.4 (mean +/- SD) and 7.4 +/- 1.1 at presentation vs 7.6 +/- 2.1 and 8.1 +/- 1.5 at discharge, respectively (P < .001 and P = .005, respectively). Although the score at presentation was significantly lower for the helium-oxygen-treated group (P < .001), no difference was found between the groups' average outcome scores. While most of the improvement in the patients in the study group could be attributed to the helium-oxygen treatment and not to the supplemental hyperbaric oxygen, in the control group, no significant difference could be demonstrated between the scores at presentation and at completion of the air-oxygen recompression table. In 5 patients who were treated with the use of the air-oxygen tables, deterioration was observed after recompression. No deterioration or neurologic DCS relapse occurred in the helium-oxygen-treated group. CONCLUSION: The results suggest an advantage of helium-oxygen recompression therapy over air-oxygen tables in the treatment of neurologic DCS.

Decompression Sickness↗
PubMed2002

Helium vs carbon dioxide gas insufflation with or without saline lavage during laparoscopy.

BACKGROUND: Helium is an inert gas that, if used for insufflation during laparoscopy, may be followed by less postoperative pain than carbon dioxide (CO2) insufflation, due to a more limited effect on intraabdominal pH and metabolism. Saline lavage has also recently been shown to reduce postoperative pain following laparoscopic surgery. To evaluate these possibilities and to better define the clinical safety of helium insufflation, we undertook a prospective randomized trial comparing CO2 and helium insufflation with or without saline lavage in patients undergoing elective laparoscopic upper abdominal surgery. METHODS: From January to November 2000, 173 patients undergoing elective laparoscopic cholecystectomy or fundoplication were randomized to undergo laparoscopy with either CO2 or helium insufflation. Within each group, patients were further randomized to undergo peritoneal lavage with 2 L of 0.9% saline at the end of the surgical procedure. This yielded the following four patient groups; CO2 (group 1, n = 47), CO2 + saline lavage (group 2, n = 43), helium (group 3, n = 43) and helium + saline lavage (group 4, n = 40). Patients were blinded to their randomization, and post-operative assessment was also performed by a blinded investigator, who applied a standardized scoring system to assess postoperative pain. RESULTS: The study groups were well matched for age, sex, weight, American Society of Anesthesiologists (ASA) status, duration of surgery, and volume of gas utilized, and 81% of patients were discharged within 48 h. There were no differences in the incidence of postoperative complications among the study groups, and postoperative pain scores were not significantly different when all four groups were compared. When helium (groups 3 and 4) was compared with CO2 (groups 1 and 2), no differences in pain score were seen. When no lavage (groups 1 and 3) was compared with lavage (groups 2 and 4), less pain was found in the group undergoing saline peritoneal lavage (mean 4-h pain score, 5.9 vs 5.2; 24-h pain score, 4.8 vs 4.1; p > 0.05). CONCLUSIONS: The use of helium insufflation for laparoscopic surgery, while not associated with any significant adverse sequelae, was not associated with less postoperative pain in this trial. The use of saline peritoneal lavage was associated with less pain in the early postoperative period.

Abdominal Pain↗
PubMed2000

Influence of nitrous oxide anesthesia on venous gas embolism with carbon dioxide and helium during pneumoperitoneum.

BACKGROUND: Gas embolism is a potential hazard during laparoscopic procedures. The aim of this study was to evaluate the effects of nitrous oxide (N(2)O) inhalation in the case of gas embolism with carbon dioxide (CO(2)) and helium during pneumoperitoneum. METHODS: For this study, 20 anesthetized pigs were ventilated with N(2)O (67% inspired) in O(2) (n = 10) or with halothane (0.7-1.5 inspired) in O(2) (n = 10). In each group, CO(2) (n = 5) or helium (n = 5) pneumoperitoneum was established and gas embolism induced at different rates (CO(2) at 0.5, 1, or 2 ml/kg/min; helium at 0.025, 0. 05, or 0.1 ml/kg/min) through the left femoral vein a maximum of 10 min while all hemodynamic parameters were continuously monitored. RESULTS: In the CO(2) group without N(2)O, all the animals tolerated rates of 0.5 and 1 ml/kg/min over the 10 min, whereas only 3 of 4 animals in the CO(2) group with N(2)O tolerated a rate of 0.5 ml/kg/min, and 2 of 4 animals a rate of 1 ml/kg/min. In the helium group without N(2)O, all the animals tolerated gas embolism at all rates, whereas in the helium group with N(2)O, 4 of 5 animals needed to be resuscitated at a rate of 0.1 ml/kg/min and one death occurred. CONCLUSIONS: Inhalation of N(2)O worsens the negative cardiovascular effects of venous CO(2) or helium gas emboli and increases the risk of emboli-induced death when CO(2) or helium are used to establish pneumoperitoneum. The volume of venous venous helium gas emboli causing such effects is substantially smaller than that for venous CO(2) gas emboli.

Anesthesia, Inhalation↗
PubMed1988

Skin blood flow from gas transport: helium xenon and laser Doppler compared.

A study was designed to compare three independent measures of cutaneous blood flow in normal healthy volunteers: xenon-133 washout, helium flux, and laser velocimetry. All measurements were confined to the volar aspect of the forearm. In a large group of subjects we found that helium flux through intact skin changes nonlinearly with the controlled local skin temperature whereas helium flux through stripped skin, which is directly proportional to skin blood flow, changes linearly with cutaneous temperature over the range 33 degrees to 42 degrees. In a second group of six volunteers we compared helium flux through stripped skin to xenon-133 washout (intact skin) at a skin temperature of 33 degrees, and we found an essentially linear relationship between helium flux and xenon measured blood flow. In a third group of subjects we compared helium flux blood flow (stripped skin) to laser doppler velocimetric (LDV) measurements (intact skin) at adjacent skin sites and found a nonlinear increase in the LDV skin blood flow compared to that determined by helium over the same temperature range. A possible explanation for the nonlinear increases of helium flux through intact skin and of LDV output with increasing local skin temperature is that they reflect more than a change in blood flow. They may also reflect physical changes in the stratum corneum, which alters its diffusional resistance to gas flux and its optical characteristics.

Blood Flow Velocity↗
PubMed1976

R.b.e. and o.e.r. of extended-Bragg-peak helium ions: survival and development of rat embryos.

Rats were exposed under aerobic or hypoxic conditions to 200-1200 rads of 60Co gamma-rays or extended-Bragg-peak helium ions on the eighth day of gestation. Uterine contents were examined on the twentieth day of gestation. At the 50 per cent embryonic survival level, helium ion r.b.e. was 1(.0) (aerobic) and 1(.2) (hypoxic). Maximum attainable gamma-ray and helium-ion o.e.r.s. were 2(.2) and 1(.7) respectively, indicating an oxygen-effect gain (o.e.g.) of 1(.2). At the 10 per cent survival level helium ion r.b.e. was 1(.1) (aerobic) and 1(.4) (hypoxic). Gamma-ray and helium-ion 0.e.r.s. were 2(.0) and 1(.5) respectively, indicating a helium ion o.e.g. of 1(.3). These data demonstrate that the small fraction of high-LET radiation present in this helium ion beam has a neglible effect on the aerobic r.b.e., but lowers the effective o.e.r. of the beam approximately 25 per cent relative to that of gamma-rays. Helium ions were significantly more effective than gamma-rays in killing embryos under hypoxic conditions, in producing congenital abnormalities under aerobic conditions, and in stunting foetal growth under both conditions.

Animals↗
PubMed1985

Helium retards endotracheal tube fires from carbon dioxide lasers.

Polyvinyl chloride (PVC) endotracheal tube segments were exposed to a 5.0-W CO2 laser beam in the presence of different fractions of oxygen and either helium or nitrogen. Time from onset of exposure until ignition was recorded, and mean time to ignition (MTI) was calculated after 10 exposures with the same gas mixture. A second series was done with 40% oxygen in either nitrogen or helium and a laser intensity of 7.5, 10.0, or 12.5 W; a third with 40% oxygen, 60% helium, and 2% halothane and a 10.0-W laser beam; and a fourth with 40% oxygen and 60% helium and a 10.0-W laser beam directed at the radioopaque barium sulfate stripe on the tube. With 5.0-W and 20% oxygen in either nitrogen or helium, segments did not ignite. With concentrations of oxygen greater than 20% in nitrogen, segments ignited sooner than with comparable concentrations in helium: MTIHe = 55.6 s and MTIN2 = 27.6 s in 40% oxygen (P less than 0.05). Sixty per cent helium remained protective at laser intensities up to 10.0 W (MTIHe = 42.6 s vs. MTIN2 = 14.3 s) (P less than 0.05). However, at 12.5 W, MTIHe = 11.5 s and MTIN2 = 11.3 s. Two per cent halothane in 40% oxygen and 60% helium reduced MTIHe to 25.3 s compared with 42.3 s without halothane. With the laser directed at the barium stripe, MTIHe was 7.2 s and MTIN2 1.1 s.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMed2001

Use of helium-oxygen mixtures to relieve upper airway obstruction in a pediatric population.

OBJECTIVES: Helium as a component of inspired gas decreases turbulent flow and airway resistance. Helium-oxygen mixtures have been used since the 1930s in the management of patients with upper airway obstruction. The objective of this study was to evaluate the efficacy of helium-oxygen mixtures in relieving upper airway obstruction in a pediatric population. STUDY DESIGN: Retrospective chart review of 42 pediatric patients who received helium-oxygen mixtures for upper airway obstruction within a 3-year period. METHODS: The study protocol included 42 pediatric patients, aged 1 week to 14 years, who were admitted to the Children's Hospital of Philadelphia from June 1997 to December 2000 and who received a total of 44 treatments of helium-oxygen therapy for upper airway obstruction. Response to treatment was determined by reduction in work of breathing noted on the chart. RESULTS: Thirty-two of 44 helium-oxygen treatments resulted in a positive response (73%). There were no significant differences in demographic characteristics between responders and nonresponders, except all of the premature infants were responders and 6 of the 9 patients with syndromes were nonresponders. CONCLUSIONS: Helium-oxygen therapy is a useful adjunct therapy for upper airway obstruction. Controlled clinical trials are necessary to better define the appropriate settings for use of helium-oxygen.

Adolescent↗
PubMed2005

Countercurrent compartmental models describe hind limb skeletal muscle helium kinetics at resting and low blood flows in sheep.

AIMS: This study evaluated the relative importance of perfusion and diffusion mechanisms in compartmental models of blood : tissue helium exchange in a predominantly skeletal muscle tissue bed in the sheep hind limb. Helium has different physiochemical properties from previously studied gases and is a common diluent gas in underwater diving where decompression schedules are based on theoretical models of inert gas kinetics. METHODS: Helium kinetics across skeletal muscle were determined during and after 20 min of helium inhalation, at separate resting and low steady-states of femoral vein blood flow in six sheep under isoflurane anaesthesia. Helium concentrations in arterial and femoral vein blood were determined using gas chromatographic analysis and femoral vein blood flow was monitored continuously. Parameters and model selection criteria of various perfusion-limited or perfusion-diffusion compartmental models of skeletal muscle were estimated by simultaneous fitting of the models to the femoral vein helium concentrations for both blood flow states. RESULTS: A model comprising two parallel perfusion-limited compartment models fitted the data well but required a 51-fold difference in relative compartment perfusion that did not seem physiologically plausible. Models that allowed a countercurrent diffusion exchange of helium between arterial and venous vessels outside of the tissue compartments provided better overall fit of the data and credible parameter estimates. CONCLUSIONS: These results suggest a role of arterial-venous diffusion in blood : tissue helium equilibration in skeletal muscle.

Administration, Inhalation↗
PubMed1985

The physiological effects of hydrostatic pressure are not equivalent to those of helium pressure on Rana pipiens.

The effects of helium pressure and hydrostatic pressure on Rana pipiens were compared. Both agents caused paralysis at pressures greater than 135 atmospheres (1 atm = 101.325 kPa), but the median pressure for hydrostatic-pressure-induced paralysis was 35 atm less than that for helium pressure. When the ability of both pressurizing agents to reverse urethane-induced anaesthesia was compared, it was found that hydrostatic pressure raised the median dose for anaesthesia 2.2-fold more per atmosphere than did helium pressure. Animals that were lightly anaesthetized by urethane at 110 atm hydrostatic pressure became more deeply anaesthetized when helium was admitted isobarically into the pressure chamber. This difference in depth of anaesthesia between hydrostatic pressure and helium pressure is consistent with helium possessing an inherent anaesthetic effect. The abilities of other gases to pressure-reverse urethane anaesthesia were also determined. The degree of attenuation of the full pressure reversal effect observed with hydrostatic pressure was proportional to the lipid solubility of the gases, increasing in the order helium, neon, hydrogen, nitrogen and argon. Our data on the difference between hydrostatic and helium pressure are consistent with the critical volume hypothesis.

Anesthesia↗
PubMedDate not supplied

Comparison of helium leak test and vacuum leak test using canned foods: collaborative study.

Two can leak tests were compared by 7 collaborators. In the helium leak test, pressurized helium is applied to the outside of the container, and a headspace gas sample from the can is then analyzed for the presence of helium. The vacuum test is described in the Bacteriological Analytical Manual. Ninety No. 303 cans of creamed-style corn, green beans, carrots, fruit cocktail, and whole-kernel corn were shipped in 3 groups. Two groups of 30 cans had 10 dented flat cans, 5 flat controls (nondented), 10 dented swollen cans, and 5 swollen control cans (nondented). The third group had 10 dented swollen cans and 5 swollen control cans. Of 600 cans analyzed, 37 (6.2%) were deleted from the analysis because results were not available for both tests. One laboratory was constrained by scheduling to analyze 15 of 45 swollen cans. The helium leak test found 12 (13%) positives of 92 nondented swollen cans. One pressurization test yielded 7 of those 12 positives. Of the 400 dented cans sent as possible leakers, the helium test found 267 positives, and the vacuum test found 181. Five of the 7 analysts had significantly (alpha = 0.05) higher percent positive helium results. One analyst found more leakers by the vacuum leak test. Both tests found fewer positives in the swollen dented cans than in the flat dented cans. After exposure to pressurized helium, all cans with greater than 8 psi headspace pressure were positive helium leakers. The method was adopted official first action.

Atmospheric Pressure↗
PubMed1982

The compressibility and the capacitance coefficient of helium-oxygen atmospheres.

The capacitance coefficient beta of an ideal gas mixture depends only on its temperature T, and its value is derived from the ideal gas law (i.e., beta = 1/RT, R being the ideal gas constant). But real gases behave as ideal gases only at low pressures, and this would not be the case in deep diving. High pressures of helium-oxygen are used in human and animal experimental dives (up to 7 or 12 MPa or more, respectively). At such pressures deviations from the ideal gas law cannot be neglected in hyperbaric atmospheres with respect to current accuracy of measuring instruments. As shown both theoretically and experimentally by this study, the non-ideal nature of helium-oxygen has a significant effect on the capacitance coefficient of hyperbaric atmospheres. The theoretical study is based on interaction energy in either homogeneous (He-He and O2-O2) or heterogeneous (He-O2) molecular pairs, and on the virial equation of state for gas mixtures. The experimental study is based on weight determination of samples of known volume of binary helium-oxygen mixtures, which are prepared in well-controlled pressure and temperature conditions. Our experimental results are in good agreement with theoretical predictions. 1) The helium compressibility factor ZHe increases linearly with pressure [ZHe = 1 + 0.0045 P (in MPa) at 30 degrees C]; and 2) in same temperature and pressure conditions (T = 303 K and P = 0.1 to 15 MPa), the same value for Z is valid for a helium-oxygen binary mixture and for pure helium. As derived from the equation of state of real gases, the capacitance coefficient is inversely related to Z (beta = 1/ZRT); therefore, for helium-oxygen mixtures, this coefficient would decrease with increasing pressure. A table is given for theoretical values of helium-oxygen capacitance coefficient, at pressures ranging from 0.1 to 15.0 MPa and at temperatures ranging from 25 degrees C to 37 degrees C.

Atmospheric Pressure↗
PubMed2005

Helium solubility in olivine and implications for high 3He/4He in ocean island basalts.

High 3He/4He ratios found in ocean island basalts are the main evidence for the existence of an undegassed mantle reservoir. However, models of helium isotope evolution depend critically on the chemical behaviour of helium during mantle melting. It is generally assumed that helium is strongly enriched in mantle melts relative to uranium and thorium, yet estimates of helium partitioning in mantle minerals have produced conflicting results. Here we present experimental measurements of helium solubility in olivine at atmospheric pressure. Natural and synthetic olivines were equilibrated with a 50% helium atmosphere and analysed by crushing in vacuo followed by melting, and yield a minimum olivine-melt partition coefficient of 0.0025 +/- 0.0005 (s.d.) and a maximum of 0.0060 +/- 0.0007 (s.d.). The results indicate that helium might be more compatible than uranium and thorium during mantle melting and that high 3He/4He ratios can be preserved in depleted residues of melting. A depleted source for high 3He/4He ocean island basalts would resolve the apparent discrepancy in the relative helium concentrations of ocean island and mid-ocean-ridge basalts.

Journal Article↗
PubMed1992

Effect of helium and oxygen on airflow in a narrowed airway.

A mixture of 80% helium and 20% oxygen has physical properties that increase airflow and decrease resistance in the airway when used as a portion of inspired gas. This study was designed to demonstrate and quantify the effects of a helium-oxygen mixture in a normal airway and when airway resistance is increased. Thirty healthy volunteers were studied breathing room air and the helium-oxygen mixture through a normal airway and an airway that included a resistor. Pulmonary function tests, directed by a registered respiratory therapist, were performed on all subjects using a computerized spirometer. The functional vital capacity, one-second forced expiratory volume, half-second forced expiratory volume, and peak inspiratory flow rate were analyzed. There was a statistically significant increase in 1-second forced expiratory volume using a helium-oxygen mixture in a normal airway. All pulmonary function test scores statistically improved when volunteers inspired helium and oxygen through the restricted airway, demonstrating that helium and oxygen can increase airflow in the presence of an increased airway resistance. This substantiates a role for helium and oxygen in treating conditions associated with decreased airway size and increased airway resistance.

Adult↗
PubMed1994

Helium pneumoperitoneum for laparoscopic cholecystectomy: ventilatory and blood gas changes.

Laparoscopic cholecystectomy with carbon dioxide pneumoperitoneum may result in hypercarbia and acidosis in patients with cardiorespiratory disease. The aim of the present study was to assess helium as an alternative to carbon dioxide for creating the pneumoperitoneum. Ventilation requirements and carbon dioxide levels were assessed at the beginning and end of laparoscopic cholecystectomy using helium (n = 30) and carbon dioxide (n = 30) pneumoperitoneum. Insufflation with helium did not result in an increase in ventilation requirement although, like carbon dioxide pneumoperitoneum, it was associated with a mean rise in peak airway pressure (of 7 cmH2O; P < 0.001). There was also a 3.2-kPa increase in the alveolar-arterial oxygen gradient with helium (P = 0.006). Carbon dioxide pneumoperitoneum was associated with a significant rise in arterial carbon dioxide levels, despite increasing ventilation. Four patients with helium pneumoperitoneum had surgical emphysema for 5 days. Helium may be a suitable alternative to carbon dioxide for creating pneumoperitoneum in patients with severe cardiorespiratory disease. However, because of its low water solubility helium has a lower safety margin than carbon dioxide in the rare event of gas embolism.

Adult↗
PubMed1985

Reduced lethality from ethanol or ethanol plus pentobarbital in mice exposed to 1 or 12 atmospheres absolute helium-oxygen.

The present experiments investigated the effects of 1 and 12 atmospheres absolute (ATA) helium-oxygen on potentially lethal doses of ethanol given alone or in combination with pentobarbital. Drug-naive, male C57BL/6J mice were injected IP with 5.4-6.5 g/kg ethanol, 4.5-6.9 g/kg ethanol plus 20 mg/kg pentobarbital, or 50-110 mg/kg pentobarbital plus 2.5 g/kg ethanol. Following injection, the mice were placed into chambers and exposed to environments of 1 ATA air, 1 ATA helium-oxygen, or 12 ATA helium-oxygen. Exposure to 1 or 12 ATA helium-oxygen significantly reduced the lethal effect (percent mortality at given doses and LD50) of ethanol given alone or with 20 mg/kg pentobarbital when compared to animals exposed to 1 ATA air. The pattern and degree of reduction in lethality for the 1 and 12 ATA helium-oxygen treatments were similar, suggesting that the antagonism resulted from increased helium or decreased nitrogen and not from increased atmospheric pressure. Exposure to these environments did not reduce lethality in mice given 2.5 g/kg ethanol in combination with relatively high doses (50-110 mg/kg) of pentobarbital. These findings suggest that helium-oxygen breathing mixtures may be useful in the treatment of some overdose patients.

Animals↗
PubMedDate not supplied

Helium-oxygen therapy in the emergency department.

Helium is an inert gas with unique physical properties that allow it to be used for various respiratory emergencies. Because of its low specific gravity and low viscosity, the passage of helium through the respiratory tract is smoother, more laminar, and less turbulent than either air or oxygen. These properties have prompted the use of helium and oxygen in patients with airway obstructions due to tumor, foreign body, edema, or bronchoconstriction. Helium-oxygen has been used to facilitate bronchoscopy through small diameter endotracheal tubes and to increase the effectiveness of high-frequency jet ventilation. Helium has been successful in the treatment of spinal cord decompression sickness seen in divers. Helium-oxygen mixtures are commercially available and may be useful in the emergency department to treat patients with airway obstruction. This article reviews literature concerning the use of helium-oxygen gas mixtures in the emergency department. Additional research conducted in the future may further define the use of this unique gas mixture in the emergency department.

Airway Obstruction↗
PubMed2005

Soft or hard ionization of molecules in helium nanodroplets? An electron impact investigation of alcohols and ethers.

Electron impact (70 eV) mass spectra of a series of C1-C6 alcohols encased in large superfluid liquid helium nanodroplets (approximately 60,000 helium atoms) have been recorded. The presence of helium alters the fragmentation patterns when compared with the gas phase, with some ion product channels being more strongly affected than others, most notably cleavage of the C(alpha)-H bond in the parent ion to form the corresponding oxonium ion. Parent ion intensities are also enhanced by the helium, but only for the two cyclic alcohols studied, cyclopentanol and cyclohexanol, is this effect large enough to transform the parent ion from a minor product (in the gas phase) into the most abundant ion in the helium droplet experiments. To demonstrate that these findings are not unique to alcohols, we have also investigated several ethers. The results obtained for both alcohols and ethers are difficult to explain solely by rapid cooling of the excited parent ions by the surrounding superfluid helium, although this undoubtedly takes place. A second factor also seems to be involved, a cage effect which favors hydrogen atom loss over other fragmentation channels. The set of molecules explored in this work suggest that electron impact ionization of doped helium nanodroplets does not provide a sufficiently large softening effect to be useful in analytical mass spectrometry.

Alcohols↗
PubMed1999

In vitro inhibition of tumour growth in a helium-rich environment: implications for laparoscopic surgery.

BACKGROUND: The recent results of several experimental studies have suggested that tumour implantation after laparoscopic surgery for intra-abdominal malignancy may be partly related to the chemical composition of the insufflation gas used during surgery. These studies have demonstrated that the use of helium as a laparoscopic insufflation agent for cancer surgery results in less tumour implantation and growth at port sites. To further investigate these findings, the present study was performed to compare the growth of cultured tumour cells after exposure to simulated laparoscopic environments, rich in helium, carbon dioxide (CO2), or air. METHODS: A rat mammary adenocarcinoma cell suspension was exposed to a simulated laparoscopic environment for 40 min in one of the following groups: (i) control (atmospheric air, equivalent to a 'gasless' laparoscopic environment); (ii) a CO2-rich environment; and (iii) a helium-rich environment. Cells were then cultured for 18 h and optical density readings were used to assess the number of viable tumour cells at the end of this period. The experiment was performed twice using an identical protocol to ensure consistency in the results. In a further study, pH was continuously measured using an antimony probe during a 40 min insufflation period and for 10 min after insufflation. RESULTS: Cell growth was significantly lower after incubation in the helium-rich environment compared to both the CO2 and control groups (P < 0.001). There was a significant decrease in pH in the CO2 group which was not observed during exposure to either air or helium. CONCLUSIONS: The inhibition of tumour growth in a helium-rich environment demonstrated by this study, and the reduced incidence of port-site metastases seen in other experimental studies, suggests that the clinical use of helium as an insufflation gas may have important advantages over CO2.

Adenocarcinoma↗