No abstract available.
Oxygen* ; Partial Pressure*

In this study, the oxygen permeabilities and diffusion rates of several soft contact lenses were measured and compared. The hydrophilic contact lenses used in this experiment were composed of four different types, 27, 32, 48 and 70 per cent of water content, respectively. Oxygen permeability rates were determined by using oxygen diffusion apparatus ctlmposed of two chamber diffusion system under a partial pressure gradient of approximately 5:1. Serial samples of 1ml were removed from the each chamber at 30 minutes interval and the Po2 in the samples was measured on a blood gas analyser. The oxygen flow rates of four different soft contact lenses varied from 99.8 micro l/cm2/hr to 292.1 micro l/cm2/hr, depending upon their water contents. The permeability characteristics was affected by the state of hydration of lens and the comparison of the oxygen flow rates showed that even the least permeable soft contact lens in this study was able to meet the corneal oxygen requirement.
Contact Lenses, Hydrophilic* ; Diffusion ; Oxygen ; Partial Pressure ; Permeability* ; Water

BACKGROUND: Arterial blood gas analysis are highly susceptible to preanalytic error due to improper method of obtaining or handling the blood sample before analysis. The error in measurement of blood gas analysis are loss of CO2 by exposure to atmospheric air, effect of anticoagulant itself, temperature difference between the experimental subject and the measuring electrode and metabolic change which occur between blood sampling and measurement. METHOD: To study the effect of the delay in estimation of blood gas and drawn blood on values of blood gas partial pressure and pH. Blood sample were divided into 2 groups according to the method of storage, group I stored at 24~25degrees C(room temperature) under anaerobic condition. ;group II stored at 0~4degrees C(refrigerator) under anaerobic condition. The samples were analyzed by time interval through 180 minutes in each group. RESULTS: The result were as follows: 1) PaO2 decreased significantly after 10 mins in group I, whereas it decreased significantly after 20 mins in group II. 2) PaO2 increased significantly after 20 mins in group I, whereas it increased significantly after 120 mins in group II. 3) pH decreased significantly after 60 mins in group I, whereas it decreased significantly after 120 mins in group II. 4) No significant changes of bicarbonate and SaO2 were noted in each group CONCLUSION: From above results, it would be advisable to analyze the sample in a short period of time or to store in a refrigerator when the measuring will be delayed. So we highly recommend that blood gas analysis should be performed as soon as possible after sampling, especially within 10 minutes.
Blood Gas Analysis ; Electrodes ; Hydrogen-Ion Concentration ; Partial Pressure

OBJECTIVE: To evaluate the safety of preoxygenation with high-flow nasal oxygenation in elderly patients during induction of general anesthesia with endotracheal intubation. METHODS: Fifty-six elderly patients without difficult airway were randomized equally into high-flow nasal oxygen group (HF group) and conventional mask oxygen group (M group). Preoxygenation was performed for 5 min before induction of general anesthesia and endotracheal intubation. Oxygenation was maintained during laryngoscopy in HF group, and ventilation lasted until laryngoscopy in M group. For all the patients, the general data, cross-sectional area (CSA) of the gastric antrum measured by ultrasonography, arterial partial pressure of oxygen (PaO₂), arterial partial pressure of carbon dioxide (PaCO₂) and arterial oxygen saturation (cSO₂) were recorded before preoxygenation (T1), at 5 min of preoxygenation (T2) and immediately after intubation (T3). The safety time of asphyxia, intubation time, times of mask ventilation and postoperative complications were compared between the two groups. RESULTS: The general data were comparable between the two groups. After 5 min of preoxygenation, PaO₂ and cSO₂ were significantly increased in both groups, and PaO₂ was significantly higher in HF group than in M group (F=118.108 vs 9.511, P < 0.05). Both PaO₂ and cSO₂ decreased after intubation, but PaO₂ decreased more slowly in HF group and still remained higher than that at T1; cSO₂ decreased significantly in M group to a lower level than that at T1. Compared with those in M group, the patients in HF group showed a significantly longer safety time of asphyxia (t=5.305, P < 0.05) with fewer times of mask ventilation (χ²= 6.720, P < 0.05). PaCO₂ increased after intubation in both groups but was comparable between the two groups (F=3.138, P > 0.05). CONCLUSION High-flow nasal oxygen is safe, simple and effective for pre-oxygenation, which, as compared with the conventional oxygen mask, improves arterial oxygen partial pressure and prolongs the safety time of asphyxia to ensure the safety of airway management during induction of general anesthesia in elderly patients with endotracheal intubation.
Aged ; Anesthesia, General ; Asphyxia ; Humans ; Intubation, Intratracheal ; Oxygen ; Partial Pressure

BACKGROUND: Lowe and Ernst's square root of time model employs direct injection of liquid agent into breathing circuit for low flow anesthesia. Intermittent injections of the agent by Lowe's method change rapidly arterial partial pressure of the agent and fail to maintain hemodynamic stability to surgical stimuli. We designed to investigate the possibility and safety of low flow anesthesia with continuous infusion of liquid enflurane into breathing circuit. METHODS: Twenty patients, ASA physical status I or II, undergoing gastrectomy under inhalational general anesthesia were randomly divided into two groups. Anesthesia was maintained with a fresh gas flow of O2 500 ml/min and continuous infusion of liquid enflurane. An identical semiclosed Dr ger circle anesthesia system was used to all patients. Liquid enflurane calculated by the Lowe's method (group I) or simplified by patient's weight (group II) was continuously infused directly into inspiratory limb of breathing circuit using syringe pump. Inspiratory and expiratory concentrations of enflurane, enflurane consumptions, hemodynamic parameters, carboxyheomoglobin were checked intraoperatively. Hepatic and renal functions were evaluted postoperatively. RESULTS: Liquid enfurane was initially infused at a rate in ml/hr of 16.1 0.8 weight in kg in group I and 1.0 weight in kg in group II. After 5 minutes the infusion rate was reduced to 20% of this value and then well adjusted to maintain blood pressure within 20% of the reference preoperative value. Enflurane consumptions and recovery time were similar between the two groups. There were no clinical significant changes in arterial blood gas, carboxyheomoglobin, and hepatic and renal functions. CONCLUSIONS: These data show that low flow anesthesia with continuous infusion of liquid enflurane into breathing circuit is safe and effective, and that the infusion method simplified by patient's weight may easily be applied to clinical practice for low flow anesthesia.
Anesthesia* ; Anesthesia, General ; Blood Pressure ; Enflurane* ; Extremities ; Gastrectomy ; Hemodynamics ; Humans ; Partial Pressure ; Respiration* ; Syringes

The post operative hypoxemia may delay the recovery from surgical damage, exacerbate organ dysfunction and contribute the mortality. The old patients are increased in the medical situation nowadays, the incidence of perioperative complications are also increased including post anesthetic hypoxemia. Herein we analysed the post operative hypoxemia in transference of the operated patient to the recovery room using pulse oximeter. During the period of 9 months from Mar. 1988, 32 patients with over 60 years old and ASA class 2 or 3 were included in this study. Hypoxemia was defined as less than 90% SaO2, (arterial oxygen partial pressure (PaO2 = 58 mmHg)). SaO2of the patient who breathed the room air for 5 min. after extubation (group 3) and just arrived at PAR (group 4) was significantly lower than preoperative SaO2(p<0.05). Hypoxemia occured in 18.8% of the patients in group 3 and 25% in group 4. During the short term period as transfering the operated patients to the recovery room the incidence of hypoxemia increased by 6.2%. There was no significance in change of pulse rate or systolic blood pressure statistically. Because surprising high incidence of hypoxemia in geriatric patients, the monitoring of the SaO2 and oxygen supply are mandatory in the high risk patients during postoperative transfer to the PAR.
Anoxia ; Blood Pressure ; Heart Rate ; Humans ; Incidence ; Middle Aged ; Mortality ; Oxygen* ; Partial Pressure ; Recovery Room

BACKGROUND: The Trendelenburg positon and pneumoperitoneum for gynecological laparoscopic surgery can affect cerebral oxygenation through the change of cerebral blood flow. The aim of this study was to evaluate the effect of pneumoperitoneum in a 20degrees Trendelenburg position on regional cerebral oxygen saturation (rSO2). METHODS: Thirty-three female patients of American Society of Anesthesiologists I and II physical status who were undergoing gynecological laparoscopic surgery were enrolled. The rSO2 was monitored with near-infrared spectroscopy (INVOS 5100, Somanetics, Troy, USA). The rSO2, the rate of change in the rSO2, the mean arterial pressure (MAP), heart rate (HR), arterial partial pressure of CO2 (PaCO2) and O2 (PaO2) and end-tidal CO2 (ETCO2) were measured at the following times: immediately before the pneumoperitoneum and when placing the patient in the Trendelenburg position (T0), 5, 10, 15 and 20 min after pneumoperitoneum and position change (T1, T2, T3 and T4). RESULTS: Both the right and the left rSO2 increased significantly during pneumoperitoneum in a Trendelenburg position compared with the value at T0 (from T1 to T4) (P < 0.01). The MAP and PaCO2 also increased significantly (P < 0.01). CONCLUSIONS: During the gynecologiccal laproscopioc surgery, cerebral oxygenation, as assessed by rSO2, increased even though the Trendelenburg position and pneumoperitoneum could increase MAP, intracranial pressure and PaCO2, which is considered to be maintained by cerebral autoregulation.
Arterial Pressure ; Female ; Head-Down Tilt ; Heart Rate ; Homeostasis ; Humans ; Intracranial Pressure ; Laparoscopy ; Oxygen ; Partial Pressure ; Pneumoperitoneum ; Spectroscopy, Near-Infrared

Blood gas analysis are highly susceptible to preanalytic error due to improper method of obtaining or handling the sample before analysis. To study the effect of air bubbles and time delay in estimation of blood gas, the samples were divided 3 groups, according to the method of stroage and the existence of air bubble, group 1, stored at 25+/-2C(room temperature) under anaerobic condition; group 2, stored at 0-4 degrees C(refrigerator) under anaerobic condition, group 3, stored at 0-4 degrees C under aerobic condition(10% air in blood). The samples were analyzed by time interval through 180 minutes in each group. The results were as follows: 1) Oxygen partial pressure decreased significantly after 20 minutes in group 2, whereas decreased significantly after 10 minutes in group 1 & group 3. 2) Carbon dioxide partial pressure increased significantly after 120 minutes in gorup 2 and 60 minutes in group 3, whereas decreased after 10 minutes in group l. 3) Blood pH decreased significantly after 60 minutes in all three Rroups. 4) Arterial oxygen saturation decreased significantly after 30 minutes in Rroup 1, 60 minutes in group 2 and 10 minutes in group 3. 5) Bicarbonate changes were not significant in all three groups clinically. From the above results, it is assumed that arterial blood samples should be analyzed whithin 10 minutes or cooled immediately.
Blood Gas Analysis ; Carbon Dioxide ; Hydrogen-Ion Concentration ; Oxygen ; Partial Pressure

In vivo ethane production in rats was used as an index of oxygen toxicity. The rats were allocated to four exposure conditions; hyperbaric oxygenation (HBO=5 ATA, 100% O2), normobaric oxygenation (NBO=1 ATA, 100% O2), hyperbaric aeration (HBA=5 ATA, 21% O2) and normobaric aeration (NBA=1 ATA, 21% O2). After 120 minutes of exposure, the rats exposed to high concentration and/or high pressure oxygen exhaled significantly larger amounts of ethane than those exposed to NBA, and the differences in ethane production between any two groups were statistically significant (p<0.01). This finding supports the hypothesis that hypothesis that hyperoxia increase oxygen free-radicals and the radicals produce ethane as a result of lipid peroxidation. It is notable that the ethane exhalation level of the HBA group was significantly higher than that of the NBO group. This difference could not be accounted for by the alveolar oxygen partial pressure difference between the two groups.
Animals ; Ethane* ; Exhalation* ; Hyperbaric Oxygenation ; Hyperoxia* ; Lipid Peroxidation* ; Oxygen ; Partial Pressure ; Rats

BACKGROUND: During cesarean section under regional anesthesia, it is current practice to provide the parturient with a source of supplemental oxygen. We compared the effect of high flow oxygen by mask with that of low flow oxygen by nasal prongs. METHODS: Fifty eight parturients presenting for elective cesarean section under combined spinal-epidural anesthesia were randomly assigned to one of the three groups to be given either oxygen 4 L/min by mask, oxygen 8 L/min by mask or oxygen 2 L/min by nasal prongs. Umbilical arterial and venous blood samples were taken and analysed immediately after delivery. RESULTS: There were no significant differences in the umbilical arterial or venous pH, partial pressure of oxygen and partial pressure of carbon dioxide among the three groups. In neonatal outcome, there were no differences in Apgar scores. CONCLUSIONS: It Makes No Differences Whether The Parturients Received Supplemental Oxygen By Nasal Prongs Or Simple Face Mask During Cesarean Section Under Combined Spinal-epidural Anesthesia.
Anesthesia ; Anesthesia, Conduction ; Carbon Dioxide ; Cesarean Section ; Female ; Hydrogen-Ion Concentration ; Masks ; Oxygen ; Partial Pressure ; Pregnancy