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Objective:To determine the optimal concentration of inhaled oxygen in pediatric patients undergoing laparoscopic choledochal cyst resection under general anesthesia.Methods:Seventy-five pediatric patients of both sexes, aged 1-3 yr, of American Society of Anesthesiologists Physical Status classification Ⅱ or Ⅲ, with body mass index of 15-18 kg/m 2, with expected operation time≥3 h, scheduled for elective laparoscopic choledochal cyst resection with general anesthesia, were divided into 3 groups ( n=25 each) using a random number table method: C 40 group (FiO 2=40%), C 30 group (FiO 2=30%) and C 21 group (FiO 2=21%). Blood samples were collected from the radial artery for blood gas analysis after operation for determination of oxygenation index (OI), respiratory index (RI), alveolar-arterial oxygen partial pressure difference (PA-aO 2) and arterial-alveolar oxygen partial pressure ratio (PaO 2/PAO 2). The occurrence of high risk events of hypoxia (SpO 2<94%), extubation time, and occurrence of pneumonia and atelectasis at day 7 after operation were recorded. Results:Compared with C 21 group, PaO 2, PAO 2, PA-aO 2 and RI were significantly increased, PaO 2/PAO 2 was decreased, and the incidence of high risk events of hypoxia was decreased in C 30 and C 40 groups, and the incidence of atelectasis in C 30 group and pneumonia and atelectasis in C 40 group was increased at day 7 after operation ( P<0.05). Compared with C 30 group, PaO 2, PAO 2, PA-aO 2 and RI were significantly increased, and PaO 2/PAO 2 was decreased in C 40 group ( P<0.05). Conclusions:The optimal concentration of inhaled oxygen recommended is 21%-30% in the pediatric patients undergoing laparoscopic choledochal cyst resection under general anesthesia.
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In order to effectively prevent the damage to the human body caused by abnormal oxygen concentration in the medical hyperbaric oxygen chamber, a ZigBee-based medical hyperbaric oxygen chamber oxygen concentration automatic control system is designed. The data acquisition module uses the microprocessor STM32F103C8T6 to receive the oxygen concentration data of each acquisition point, and the ZigBee of the data processing module transmits the processing results to the MSP430G2553 single-chip microcomputer at the receiving end of the slave. The MSP430G2553 single-chip microcomputer uses a self-organizing TS fuzzy neural network (SOTSFNN) and adds activation. The intensity concept realizes automatic control of the oxygen concentration in the hyperbaric oxygen chamber, and controls the buzzer to give an alarm when the oxygen concentration is lower than 19 mg/L and higher than 23 mg/L, and displays the current real-time oxygen concentration through LCD12864. The experimental results show that as the communication distance increases, the packet loss rate of the system is always lower than 5%, and the signal strength under the same communication distance is better; the system can effectively control the oxygen concentration value within the set range, and the oxygen concentration. The control accuracy is high and the stability is good.
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Humanos , Oxigenoterapia Hiperbárica , Microcomputadores , OxigênioRESUMO
Abstract (1) Background: Oxygen supply is an important parameter to be considered in submerged cultures. This study evaluated the influence of different conditions for dissolved oxygen (DO) concentration on laccases activities and growth of Pleurotus sajor-caju PS-2001 in submerged process in stirred-tank bioreactor. (2) Methods: Initially, three different conditions were tested: uncontrolled DO and minimum levels of 30% and 80% of saturation, with the pH controlled between 4.5 and 7.0. (3) Results: Best results were observed at 30% DO (26 U mL-1 of laccases at 96 h), whereas higher mycelial biomass was observed at 30% and 80% DO (above 4.5 g L-1). Four different conditions of DO (uncontrolled, 10%, 30% and 50% of saturation) were tested at pH 6.5, with higher laccases activity (80 U mL-1 at 66 h) and lower mycelial growth (1.36 g L-1 at 90 h) being achieved with DO of 30%. In this test, the highest values for volumetric productivity and specific yield factor were determined. Under the different pH conditions tested, the production of laccases is favoured at DO concentration of 30% of saturation, while superior DO levels favours fungal growth. (4) Conclusion: The results indicate that dissolved oxygen concentration is a critical factor for the culture of P. sajor-caju PS-2001 and has important effects not only on laccases production but also on fungal growth.
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Oxigênio Dissolvido , Biomassa , Reatores Biológicos , Pleurotus/crescimento & desenvolvimento , Pleurotus/enzimologia , Lacase/biossínteseRESUMO
Objective@#To verify the accuracy of oxygen concentration (FiO2) of modified oxygen treatment with Venturi and humidity system.@*Methods@#Patients just after ventilator weaning and before the removal of tracheal intubation/tracheotomy tube, who admitted to the intensive care unit (ICU) of Henan Provincial People's Hospital from May 1st to December 15th in 2017, were enrolled. All patients were given a modified oxygen treatment with Venturi and humidity system, and the oxygen flow rate (Flow) of the Venturi device and the oretical value of FiO2 were adjusted according to the patient's condition. Patients were divided into five groups based on doctor's orders: Flow 3 L/min FiO2 0.24, Flow 3 L/min FiO2 0.26, Flow 6 L/min FiO2 0.28, Flow 6 L/min FiO2 0.30, Flow 9 L/min FiO2 0.35. The value of FiO2 at the inhalation end of patients of each group was measured by TSI airflow analyzer, and the consistency between the measured value of FiO2 at the inhalation end and the FiO2 marked value of Venturi was compared and analyzed.@*Results@#When the FiO2 theoretical value of Venturi were adjusted to 0.24, 0.26, 0.28, 0.30, and 0.35, the measured values of FiO2 at the inhalation end of patients were 0.38±0.05, 0.38±0.05, 0.40±0.04, 0.41±0.04, and 0.77±0.11, respectively, which were all significantly higher than the theoretical value of FiO2 (all P < 0.01). The difference between the measured value of FiO2 at the inhalation side and the FiO2 value of the Venturi annotated and the difference rate were both "V"-shaped, both of which decreased with the increase in theoretical value of FiO2 to a Flow of 9 L/min and a theoretical value of FiO2 0.35, the accuracy was the worst, with the FiO2 difference of 0.42±0.11, and the FiO2 difference rate of (121.6±36.5)%.@*Conclusion@#There is a difference between the measured value and the theoretical value of FiO2 at the inhalation end of the modified Venturi oxygen therapy humidification system, which needs to be paid attention to during clinical oxygen therapy.
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Objective To Observe and evaluate the effect of hyperbaric oxygen therapy for patients with tracheotomy using ventilator lengthening tube. Methods 75 patients with tracheotomy in our hospital from January 2017 to January 2018 were divided into the study group (n = 38 cases) and the control group (n = 37 cases) according to the random number method. The control group used conventional oxygen inhalation while the study group used the ventilator tube after prolonged special oxygen hyperbaric oxygen pipe three (built-in ventilation pipe check valve) and bellows connecting an oxygen supply device, compared two groups of patients with oxygen inhalation methods suction phlegm oxygen concentration times and cabin, every time when treating. Results The rate of oxygen inhalation in the study group was 97. 37％ (37/38) higher than that of the control group (81. 08％ (30/37)), and the difference was statistically significant (P＜0. 05). The number of sputum sucking in the study group was (1. 02 ± 0. 36) times less than that of the control group (2. 32 ± 0. 53), and the difference was statistically significant (P＜0. 05). The total time of hospitalization in the study group was (16. 4 ± 2. 4) d, and the total time of hospitalization in the control group was (21. 7 ± 3. 2) d, the difference was statistically significant(WTBX〗P＜0. 05). The score of GCS in the study group was higher than that of the control group, and the difference was statistically significant (P＜0. 01). Conclusion The ventilator extension tube for hyperbaric oxygen therapy in patients with tracheotomy improves the oxygen concentration, ensures the curative effect, reduces the oxygen concentration in the cabin and reduces security risks; the operation method is safe, simple and practical and convenient for clinical application.
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Objective To measure the catalytic effect of ammonium salt solution on hydrogen production , and analyze the relationships between hydrogen concentration and oxygen concentration , oxidation-reduction potential , and pH in solution . Methods Magnesium and water reacted at different concentrations of NH4Cl, (NH4)2SO4, NH4HCO3,(NH4)2CO3, NaHCO3 and Na2SO3 in 40℃water bath for 0, 2, 4, 6, 8 and 10 hours, and above-mentioned four indicators of ammonium salt solution were measured after these reactions .Results The hydrogen concentration in the solution increased with the reaction time and the concentration of the ammonium salt solution .Oxygen concentration and oxidation-reduction potential decreased .The hydrogen concentration in the solution was significantly negatively correlated with the oxygen concentration (r=-0.984).pH increased with the hydrogen concentration in the ammonium salt solution .Conclusion The ammonium salt solution has a good catalytic effect on magnesium and water reaction .NH4Cl has the strongest catalytic effect under the same reaction conditions,followed by (NH4)2SO4, NH4HCO3 and (NH4)2CO3.Thus, this study can provide detailed data on hydrogen production in different solutions .
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Objective To measure the maximum dissolved oxygen concentration of the lithotripter to avoid visible air bubbles during lithotripsy.Methods The present situation of degassing of lithotripter and clinical requirements for water were introduced.Under the following conditions of 7.5 L water capacity,35 L/h water flow,ambient temperature 28 ℃,17 kV,60 shocks per minute,the lithotripter discharged 10 000 shocks continuously without a visible air bubble in the circulating water,then the dissolved oxygens in the water were measured by using AZ8403 dissolved oxygen meter.The maximum value of dissolved oxygen in the water was determined therefore without a visible air bubble.Results The visible tiny air bubble emerged during lithotripsy if the dissolved oxygen in the water was above 3.37 mg/L and ambient temperature was about 28 ℃;the bubble could be avoided if the dissolved oxygen was under 3.34 mg/L and ambient temperature was about 28 ℃.Conclusion The circulating water with dissolved oxygen concentration less [han 3 mig/L and about 28 ℃ ambient temnperature are recommended for the electromagnetic extracorporea] shock wave lithotripter during lithotripsy.
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Objective To analyze the relationship between the measurement error of oxygen concentration and service time of oxygen cell of the ventilator. Methods The present situation of the ventilator was analyzed. Some cases of alarms for oxygen concentration failures were taken in statistical analysis on 3-a quality control detection results of the ventilators in some hospital. Results There was an approximately linear correlation between the measurement error of oxygen concentration and service time of oxygen cell, and the measurement error of oxygen concentration was increased significantly 430 days after the oxygen cell enabled. Conclusion The measurement error of oxygen concentration quality control could be used as a reference for performance evaluation and replacement of oxygen cell.
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Objective To determine the effects of oxygen at varied concentrations on in vitro maturation (IVM)of oocytes,and subsequent fertilization,early-stage development of embryos by collecting the human imma-ture oocytes from assisted reproduction treatment. Methods Immature oocytes were randomly allocated to be cul-tured with oxygen at a lower or higher concentration. Intracytoplasmic sperm injection of mature oocytes after IVM , the rates of maturation,fertilization,embryo cleavage and high quality embryo were investigated. Results The GV oocytes cultured with oxygen at the lower concentration yielded higher maturation and fertilization rates than those at the higher concentration(P<0.05). There were no significant differences in the rates of embryo cleavage and high quality embryo between two groups(P > 0.05). For MI oocytes,the maturation rate of oocytes cultured with oxygen at the lower concentration was higher as compared to that at the higher concertration (P < 0.05). There were no significant differences in the rates of fertilization ,embryo cleavage and high quality embryo between the two groups(P > 0.05). Conclusions Oxygen at a lower concentration is beneficial to IVM of human imma-ture oocytes and it also improves the fertilization of GV oocytes after IVM. Oxygen at a lower concentration has no beneficial effect on the embryo cleavage rate and high quality embryo rate.
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Objective To determine the effects of oxygen at varied concentrations on in vitro maturation (IVM)of oocytes,and subsequent fertilization,early-stage development of embryos by collecting the human imma-ture oocytes from assisted reproduction treatment. Methods Immature oocytes were randomly allocated to be cul-tured with oxygen at a lower or higher concentration. Intracytoplasmic sperm injection of mature oocytes after IVM , the rates of maturation,fertilization,embryo cleavage and high quality embryo were investigated. Results The GV oocytes cultured with oxygen at the lower concentration yielded higher maturation and fertilization rates than those at the higher concentration(P<0.05). There were no significant differences in the rates of embryo cleavage and high quality embryo between two groups(P > 0.05). For MI oocytes,the maturation rate of oocytes cultured with oxygen at the lower concentration was higher as compared to that at the higher concertration (P < 0.05). There were no significant differences in the rates of fertilization ,embryo cleavage and high quality embryo between the two groups(P > 0.05). Conclusions Oxygen at a lower concentration is beneficial to IVM of human imma-ture oocytes and it also improves the fertilization of GV oocytes after IVM. Oxygen at a lower concentration has no beneficial effect on the embryo cleavage rate and high quality embryo rate.
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Objective To verify the efficiency and stability of hydrogen-rich water preparation with hydrogen-rich rods. Methods ①Seven firenew hydrogen-rich rods were separately placed in seven plastic bottles, each filled with distilled water and soaked for 6 h, before the hydrogen concentration of the water was measured.This process was repeated 10 times.②After the hydrogen-rich rods with the strongest and weakest hydrogen product capacity were removed, the remaining 5 hydrogen-rich rods were placed separately into 5 plastic bottles filled with distilled water,put in a water bath pot at 20,40 and 60℃, respectively, and kept for 2, 4, 6, 8 and 10 h, respectively.Then, the hydrogen concentration, oxidation-reduction potential(ORP),and dissolved oxygen concentration(DO) were measured at various time points.③In order to determine the hydrogen emission rate from the hydrogen-rich water, the hydrogen-rich rods were constantly kept in some samples and the others were removed.All the sample bottle caps were kept open during the experimental process, and the hydrogen concentration was measured at such time points as 0, 10 and 30 min, 1, 2, 5, 12, 24, 30, 48 and 72 h, respectively.Results ①The hydrogen-rich rods used in this study could well meet the requirements.②When the environment temperature was kept constant, the hydrogen concentration of the water was increased with the soaking time of the hydrogen-rich rods, and the ORP of the water was reduced.However, the DO of the water was decreased with the rise of the environment temperature.③When the hydrogen-rich water was kept in opened plastic bottles with a 25 mm oral diameter, the hydrogen concentration of the samples with the hydrogen-rich rods reserved was almost about 0.50 ppm until 72 h, and that of the others was reduced to almost 0 ppm.Conclusion Our results demonstrate that the hydrogen-rich rods test is a simple and effective method for preparing hydrogen-rich water, which will be an valuable and useful method for using hydrogen-rich water in health promotion and prevention of chronic diseases.
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Objective To investigate the effect of various concentration of inhaled oxygen during exercise on reactive oxygen species (ROS) production in chronic obstructive pulmonary disease (COPD) rats and the possible mechanism. Methods Eighty COPD Wistar rats were divided into low oxygen (LO, n=20), normal oxygen (NO, n=20) and inhaled oxygen (IO, n=20) exercising groups, which ran on tread-mill in the conditions of 13.6%, 21%, 25%oxygen, respectively, and non-exercising normal oxygen group (C, n=20), which stood on still treadmill in the condition of 21%oxygen. Their apoptosis percentage of neutrophils and ROS content were measured with flow cytometry, glutathione (GSH) in lung with immunohistochemistry and cytochrome C oxidase IV (COXIV) in skeletal muscle with Western blotting, as one and four weeks of exercising. Results For one week of exercise, the ROS was more in LO and NO groups than in C group (P0.05). For four weeks of exercise, the ROS was more in LO group but less in NO and IO groups than in C group (P<0.05);while the expression of GSH and COXIV increased in NO and IO groups compared with those in C group (P<0.05). Conclusion A long term exercise in non-hypoxic state may inhibit ROS production for COPD patients, by promoting neutrophils apoptosis and antioxidant expression.
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Objective Little is known about the role of low oxygen concentration in the formation of the capsule of Cryptococ -cus neoformans .This study was to investigate the effect of hypoxic condition on the capsule size of Cryptococcus neoformans . Methods We cultured 39 Cryptococcus neoformans strains in liquid Sabouraud medium and then incubated them at the normoxic (21%) and hypoxic concentration (1%), respectively.After 72 hours of incubation, we observed the capsules formed at different ox-ygen conditions under the Olympus microscope and the measured their sizes using the Axiovision software . Results Of the total number of Cryptococcus neoformans strains , 30 showed larger capsules in the normoxic than in the hypoxic condition , 17 with statisti-cally significant differences in their diameters (P<0.05), while the other 9 strains exhibited just the opposite results , 4 with statisti-cally significant differences in their diameters ( P<0.05). Conclusion Hypoxia might inhibit the growth of the Cryptococcus neoformans capsule.However, further studies are needed on its correlation with the serum or gene types of the Cryptococcus neofor-mans strain.
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Background:Mesenchymal stem cells derived from bone marrow and adipose tissue are being applied to tissue engineering and cell therapy. The use of stem cells of various clinical applications is highly expected and the production of good quality stem cells is very critical for basic studies. In the bone marrowmesenchymal stem cells from an unique niche in which the oxygen tension is low. Hypoxia may have a role in maintaining stem cell fate, self renewal and multi-potency. We investigated whether low oxygen culture would be beneficial for mesenchymal stem cell. Results:BMCs from 8-10 week aged, 6 mice were subjected to hypoxic conditioning by culture for 7 days in 20%, 3%, 1% oxygen. For culture 1x106 cell/ml were seeded in media with L-glutamine in each dish. During the culturing, cell colonies were checked once in three days. After cell culture, we stained cells by CD90 then counted CD90 positive cells by fluorescence microscope. More colonies and mesenchymal cells were observed at 3%, 1% oxygen and also colonies were bigger in hypoxic condition. Statistical significances were identified mesenchymal cells (p<0.05) in hypoxic condition. Conclusions:Our data suggests low physiological oxygen culture could improve the differentiation of mesenchymal cells. Long term culture will be necessary to confirm whether low physiological oxygen levels also improve genomic stability.
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BACKGROUNDThe use of stem cells for various clinical applications is highly expected and the production of good quality stem cells is very critical for basic studies. In the bone marrow, hematopoietic and mesenchymal stem cells form a unique niche in which the oxygen tension is low. Hypoxia may have a role in maintaining stem cell fate, self renewal and multi-potency. We investigated whether low oxygen culture would be beneficial for hematopoietic stem cell stemness.METHODSBone marrow cells from 8-10 week aged mice were subjected to hypoxic conditioning by culture for 7days in 20%, 3% and 1% oxygen. For culture,1x105 cell/ml were seeded in colony forming assay in each dish. During the culturing, cell colonies were checked once every three days. Compared to normoxic cells, hypoxic cells weremorphologicallyundifferentiated and counted by Olympus IX71 microscope.RESULTSMore colonies were observed at 3% and 1% oxygen. Statistical significances were identified with granulocytes and macrophage colony (p<0.05) in hypoxic condition.CONCLUSIONSOur data suggests low physiological oxygen culture could improve the stemness of macrophage and granulocytes colony. Long term culture will be necessary to confirm whether low physiological oxygen levels also improve genomic stability.
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Objective To investigate the effect of low oxygen tension (7.5% O2) on human embryo development in vitro and outcome of women undergoing IVF-ET. Methods The data of 280 routine IVF cycles with fresh embryo transfer on day3 conducted in the 2nd People's Hospital of Yunnan Province from February 2012 to August 2013 were retrospectively analyzed. Two groups, 7.5%O2 low oxygen tension (n=120) and 20%O2 high oxygen tension (n=160),were setup for early embryo (D1-D3) development in vitro. Results Good quality embryo on day 3 in low oxygen tension group showed morphologically appearance of blastomere mutually clinging to each other,a characteristic of slight compaction. Higher rate of good quality embryo (66.22%V. 47.54%) and of clinical pregnancy (53.33%v. 39.22%) were found in the low oxygen tension group. There were no significantly differences in rates of fertilization,cleavage and embryo utilization respectively between the two groups ( all>0. 05) . Conclusion High quality early stage human embryos can be developed in vitro in low oxygen tension, and may improve clinic outcome of IVF.
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Objective To evaluate the effects of fraction of inspired oxygen (FiO2) and positive end-expiratory pressure (PEEP) on the gradient between arterial and end-tidal carbon dioxide (D(a-ET)CO2).Methods Sixty ASA Ⅰ or Ⅱ patients (body mass index ＜ 30 kg/m2),aged 25-50 yr,weighing 45-75 kg,scheduled for elective gynecological laparoscopic surgery,were randomized into A,B and C groups (n =20 each).The patients were mechanically ventilated with pure oxygen in group A,and with air and O2 (FiO2 =50％) in groups B (PEEP =0) and C (PEEP =5 cm H2O).PETCO2 was monitored during mechanically ventilation.Blood samples were obtained from the radial artery immediately after tracheal intubation (T1) and at 1 h of pneumoperitoneum (T2) for blood gas analysis.D(a-ET) CO2 and Qs/Qt were calculated.Results D(a-ET) CO2 and Qs/Qt were significantly lower at T2 in groups B and C than in group A (P ＜ 0.05).Compared with group B,D(a-ET)CO2 was significantly decreased at T2 (P ＜ 0.05),and no significant change was found in Qs/Qt in group C (P ＞ 0.05).Conclusion Decreased FiO2 and PEEP of 5 cm H2O can decrease D(a-ET)CO2 and increase the accuracy of PErCO2 for reflection of PaCO2,which is due to reduced intrapulmonary shunt.
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BACKGROUND: Preoxygenation with tidal volume breathing for 3 min is a standard technique using 100% oxygen for prevention of hypoxia during the induction of general anesthesia. The measurement of end tidal oxygen concentration is useful in preoxygenation monitoring. The aim of the study was to determine the effects of preoxygenation in pediatric patients during 3 min with tidal volume breathing. METHODS: Sixty patients who were scheduled for general surgery were divided into 0-6 yr old children (Group I, n = 20), 7-15 yr old children (Group II, n = 20) and adults (Group III, n = 20). Patients with an inflatable mask connected to an anesthesia machine breathed 100% oxygen spontaneously for 3 min with tidal volume in all three groups. End tidal oxygen concentration, end tidal carbon dioxide concentration and respiratory rate were measured simultaneously for 3 min. RESULTS: Group I and II showed significantly higher end tidal oxygen concentrations than Group III from 10 sec to 160 sec with 3 min tidal volume breathing (P < 0.05). The mean time required for end tidal oxygen concentration of 90% was 85.5 +/- 18.5 sec for Group I, 101.5 +/- 21.5 sec for Group II and 148.0 +/- 24.0 sec for Group III. Therefore, Group I and II showed a significantly shorter time than Group III (P < 0.05). CONCLUSIONS: Pediatric patients showed a significantly shorter time to obtain the required preoxygenation.
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Adulto , Criança , Humanos , Anestesia , Anestesia Geral , Hipóxia , Dióxido de Carbono , Máscaras , Oxigênio , Respiração , Taxa Respiratória , Volume de Ventilação PulmonarRESUMO
BACKGROUND: Preoxygenation is a standard anesthetic technique using 100% oxygen for the prevention of hypoxia during the induction of anesthesia. Measuring end-tidal oxygen is the most useful indicator for determining the end-point of preoxygenation. We studied the effects of preoxygenation between pregnant and non-pregnant patients during 5 min of tidal volume breathing. METHODS: Non-pregnant women who were scheduled for general surgery (Group I, n = 25) and pregnant women who were scheduled for elective cesarean section (Group II, n = 20) were explained the technique of preoxygenation, which was conducted with 100% oxygen during 5 min of tidal volume breathing. End-tidal oxygen concentration was measured at 10 sec intervals for 5 min, simultaneously. RESULTS: Group II showed significantly higher end-tidal oxygen concentration than Group I from 30 sec to 170 sec during preoxygenation (P or =90% was 110.0 +/- 31.7 sec for Group II and 152.8 +/- 34.5 sec for Group I. Therefore, Group II showed a significantly shorter time than Group I (P < 0.05). CONCLUSIONS: We concluded that the time for complete preoxygenation was shorter in pregnant patients compared to non-pregnant patients.
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Feminino , Humanos , Gravidez , Anestesia , Hipóxia , Cesárea , Oxigênio , Gestantes , Respiração , Volume de Ventilação PulmonarRESUMO
BACKGROUND: Preoxygenation with tidal volume breathing for 3 min is commonly used technique. An end tidal expiratory oxygen concentration greater than 90% is considerd to be adequate for preoxygenation. The aim of this study was to check the effects of preoxygenation on elderly patients through the comparison with young patients during the 3 min tidal volume breathing technique. METHODS: Sixty patients from ASA class I or II who were scheduled for elective orthopedic general surgery were divided into an elderly (>65 yr) group and a control (25-65 yr) group. Patients were instructed in the technique of preoxygenation. Preoxygenation was accomplished with an appropriately sized face mask connected to an anesthesia machine with 100% oxygen during 3 min with patients in both groups. Expired O2, CO2 concentration and oxygen saturation were recorded simultaneously for 3 min. RESULTS: The elderly group showed significantly lower end tidal oxygen concentration than the control group from 50 sec to the end of study (180 sec) with the 3 min tidal volume breathing technique (P < 0.05). In 180 sec, the control group had over 90% (91.5%) end tidal oxygen concentration, but in the elderly group end tidal oxygen concentration could not reach 90% (86.2%). In oxygen saturation, the elderly group showed a significantly lower level until 40 sec from the start of study, and then two groups showed a similar levels of oxygen saturation until the end of study. CONCLUSIONS: End tidal oxygen concentration did not reach 90% in 180 sec in the elderly group during preoxygenation with the 3 min tidal volume breathing technique.