About

Eric Christopher Chen is an Assistant Professor in the Department of Mathematics at Illinois College of Liberal Arts & Sciences. His research areas include Analysis, Geometry, and Topology. He has contributed to the field through publications on topics such as degree theory for 4-dimensional asymptotically conical gradient expanding solitons, the Yamabe flow on asymptotically Euclidean and flat manifolds, and the Neumann problem on domains in S 3 bounded by the Clifford torus. His work involves advanced mathematical analysis and geometric flows, and he is actively engaged in research that advances understanding in these areas.

Research topics

• Medicine
• Family medicine
• Nursing
• Anesthesia
• Demography

Selected publications

• Effects of Diazepam on Sleep, Temperature, 5-Hydroxyindoleacetic and Homovanillic Acids in Cisternal Cerebrospinal Fluid of Cats

  Pharmacology · 2008-05-29 · 51 citations

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  The effects of diazepam (DZ) (0.3--1.5 mg/kg, i.p.) on sleep, cisternal cerebrospinal fluid (CSF) concentrations of 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA), and rectal temperature of cats were examined. The results showed that administration of DZ produced a significant increase (p = 0.02) in slow-wave sleep (SWS) with a peak occurring at a dose of 0.9 mg/kg. Further increase in doses of DZ decreased SWS. DZ administration produced no change in paradoxical sleep, rectal temperature, 5-HIAA or HVA CSF levels. Lack of correlation between various doses of DZ, and 5-HIAA or HVA concentrations in the presence of an increased percentage of SWS suggests a possible mode of DZ action mediated through a mechanism independent of monoamines. Usually monoamines are associated with normal sleep.

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• Organic Mercury Levels among the Yanomama of the Brazilian Amazon Basin

  AMBIO · 2003-01-01

  articleSenior authorCorresponding

  The Catrimani River basin in northern Brazil is the home of the Yanomama and has been the site of renegade gold mining since 1980. Gold-mining operations release inorganic mercury (Hg) into the environment where it is organified and biomagnified in aquatic ecosystems. Ingestion of mercury-contaminated fish poses a potential hazard to fish-eating populations such as the Yanomama. We surveyed Hg levels in Yanomama villagers living near mined and unmined rivers in 1994 and 1995, and analyzed Hg levels in piranha caught by villagers. In 1994, 90 Yanomama Indians from 5 villages and in 1995, 62 Yanomama Indians from 3 villages participated in the studies. Four villages surveyed in 1994 were located directly on the Catrimani River, approximately 140–160 km downstream from past gold-mining activities. The other village surveyed in 1994 was situated on the unmined Ajaraní River. In 1995, 2 of the Catrimani River villages were revisited, and a third Yanomama village, on the unmined Pacu River, was surveyed. Blood organic mercury levels among all villagers surveyed ranged from 0 to 62.6 µg L–1 (mean levels in each village between 21.2 µg L–1 and 43.1 µg L–1). Mercury levels in piranha from the mined Catrimani River ranged from 235 to 1084 parts per billion (ppb). Nine of 13 piranhas, measuring 30 cm or longer had total mercury levels which exceeded mercury consumption limits (500 ppb) set by both the World Health Organization and the Brazilian Ministry of Health. Unexpectedly, high mercury levels were also observed in fish and villagers along the unmined Ajaraní and Pacu Rivers suggesting that indirect sources may contribute to environmental mercury contamination in the Amazon basin.

  PublisherDOI

• Organic Mercury Levels among the Yanomama of the Brazilian Amazon Basin

  AMBIO · 2003-11-01 · 26 citations

  articleSenior authorCorresponding

  The Catrimani River basin in northern Brazil is the home of the Yanomama and has been the site of renegade gold mining since 1980. Gold-mining operations release inorganic mercury (Hg) into the environment where it is organified and biomagnified in aquatic ecosystems. Ingestion of mercury-contaminated fish poses a potential hazard to fish-eating populations such as the Yanomama. We surveyed Hg levels in Yanomama villagers living near mined and unmined rivers in 1994 and 1995, and analyzed Hg levels in piranha caught by villagers. In 1994, 90 Yanomama Indians from 5 villages and in 1995, 62 Yanomama Indians from 3 villages participated in the studies. Four villages surveyed in 1994 were located directly on the Catrimani River, approximately 140-160 km downstream from past gold-mining activities. The other village surveyed in 1994 was situated on the unmined Ajaraní River. In 1995, 2 of the Catrimani River villages were revisited, and a third Yanomama village, on the unmined Pacu River, was surveyed. Blood organic mercury levels among all villagers surveyed ranged from 0 to 62.6 microg L(-1) (mean levels in each village between 21.2 microg L(-1) and 43.1 microg L(-1)). Mercury levels in piranha from the mined Catrimani River ranged from 235 to 1084 parts per billion (ppb). Nine of 13 piranhas, measuring 30 cm or longer had total mercury levels which exceeded mercury consumption limits (500 ppb) set by both the World Health Organization and the Brazilian Ministry of Health. Unexpectedly, high mercury levels were also observed in fish and villagers along the unmined Ajaraní and Pacu Rivers suggesting that indirect sources may contribute to environmental mercury contamination in the Amazon basin.

  PublisherDOI

• Assessment of the Diet Quality of Middle-aged and Older Adult Korean Americans Living in Chicago

  Journal of the American Dietetic Association · 2002-04-01 · 14 citations

  article
  PublisherDOI

• Smoking Among Chinese Americans: Behavior, Knowledge, and Beliefs

  American Journal of Public Health · 2002-06-01 · 88 citations

  article

  Objectives. This report describes and examines factors significantly associated with smoking among Chinese Americans, using multiple logistic regression methods. Methods. We conducted a population-based survey (n = 644, age = 40-69 years) in Chicago's Chinatown using a Chinese questionnaire based on the National Health Interview Survey (NHIS). Results. Smoking prevalence was 34% for males and 2% for females. Some 93% of current smokers had smoked regularly for 10 or more years. Low education (odds ratio [OR] = 2.41; 95% confidence interval [CI] = 1.31, 4.46), use of a non-Western physician or clinic for health care (OR = 2.64; 95% CI = 1.46, 4.80), and no knowledge of early cancer warning signs and symptoms (OR = 2.52; 95% CI = 1.35, 4.70) were significantly associated with smoking among men. Conclusions. The male prevalence of smoking is higher than those reported in California, the NHIS, and the Behavioral Risk Factor Surveillance System (BRFSS); exceeds the rate for African Americans aged 18 years and older; is comparable with the rate for African American males aged 45 to 64 years; and is far above the Healthy People 2010 target goal of less than 12%. Multisite surveys and smoking cessation campaigns in Chinese are needed.

  PublisherDOI

• Nutritional status of Korean Americans: implications for cancer risk.

  PubMed · 2001-05-31 · 26 citations

  article

  PURPOSE/OBJECTIVES: To examine nutrient intake of Korean Americans, especially those foods and supplements implicated in cancer. DESIGN: Cross-sectional survey and descriptive analysis. SETTING: Chicago, IL. SAMPLE: 103 Korean Americans who were between 40 and 69 years of age. METHODS: An Instrument, culturally and linguistically adapted from the Health Habits and History Questionnaire, was administered to assess nutrient intake from food and vitamin and mineral supplements. Bilingual interviewers collected data at respondents' homes. FINDINGS: Relative to their diet in Korea, more than one-third of the respondents reported an increase in the consumption of beef, dairy products, coffee, soda, and bread, as well as a decrease in the intake of fish and rice and other grains. Compared to the general U.S. population included in the National Health Interview Survey (NHIS), Korean Americans had a greater intake of carbohydrates and vitamins A and C and lower intake of total fat, cholesterol, and saturated fat. Moreover, the percentages of calories were higher from carbohydrates and lower from fat, sweets, and alcohol for Korean Americans than those reported by NHIS respondents. Gender, education, and marital status were significantly associated with nutrient intake. The use of daily vitamin and calcium supplements was similar between respondents and those from NHIS. CONCLUSIONS: At their stage of cultural adaptation, the incorporation of a larger quantity of Western food items did not make for a less healthy dietary pattern among respondents. Data showed that Korean Americans continued to consume diets more consistent with Korean than with American food patterns, in as much as greater than 60% of their calories came from carbohydrates and about 16% of calories from fat. As a group, respondents met the recommended dietary guidelines for most nutrients, except for dietary fiber and calcium. IMPLICATIONS FOR NURSING PRACTICE: Variation in dietary intake by age, culture, gender, and years in the United States is well accepted. Effective cancer prevention and initiatives for dietary reform call for the incorporation of available research findings and considerable attention to data gaps regarding Korean Americans and other Asian Americans and Pacific Islander populations. Culturally competent, community-based programs should include the reinforcement of positive traditional dietary habits, encourage the adaptation of healthy Western food items, as well as assist minority populations in developing strategies that will effectively correct likely deficiencies in diet.

  Publisher

• Colorectal Cancer Screening Among Chinese Americans

  Journal of Psychosocial Oncology · 2001-12-03 · 19 citations

  article

  Abstract This study examined knowledge and practices regarding screening for colorectal cancer among 312 male and 332 female Chinese Americans in Chicago's Chinatown. A Chinese translation and cultural adaptation of the Cancer Control Supplement Questionnaire from the National Health Interview Survey was used to interview the respondents, who ranged in age from 40 to 69 years. Approximately 85% of the respondents had never been screened with the fecal occult blood test (FOBT), compared with 70% of the general population-far below the 50% target set by the Healthy People 2000 program. The majority of respondents had never heard of the digital rectal examination (DRE), and approximately 20% of respondents had never had one. Fewer than half the respondents knew about the FOBT and thus had never had one, and only a third were able to identify at least one warning sign of cancer. Multiple logistic regression analyses identified educational level and knowledge of the warning signs as the significant factors influencing knowledge about DRE and FOBT. Education alone was associated with use of DRE, and age alone was associated with use of FOBT. The majority of respondents lacked a regular source of health care; thus, other sources of health information (e.g., newspapers, magazines, television, community centers) need to be supported and strengthened.

  PublisherDOI

• Breast and Cervical Cancer Screening among Chinese American Women

  Cancer Practice · 2001-03-01 · 111 citations

  article

  PURPOSE: The purpose of this study was to describe breast and cervical cancer screening knowledge and practices of a representative sample of Chinese American women and to examine the factors associated with screening practices. DESCRIPTION OF STUDY: A random sample of 332 Chinese American women, 40 to 69 years of age, from the Chinatown area of Chicago, Illinois, were interviewed face to face, using both Chinese Mandarin (or Putunghua) and Cantonese versions of the National Health Interview Survey (NHIS) Cancer Control Supplement Questionnaire. Knowledge and use of mammogram, clinical breast examination (CBE), breast self-examination (BSE), and Pap smear test were assessed. RESULTS: The results showed a low level of knowledge of cancer screening tests and low use rates. Multiple logistics regression analysis showed that women with spoken English fluency were more likely to have knowledge and use of CBE, BSE, Pap test, and mammograms. Women with better than an elementary education were more likely to have knowledge and use of CBE, BSE, and Pap test. The source of medical care was statistically significant for having had a mammogram. Knowledge of cancer warning signs and symptoms was significant for knowledge of mammogram and BSE and for the use of BSE. CLINICAL IMPLICATIONS: Multiple strategies are needed. These might include the following: 1) integration of research with population-based care by physicians and scientists; 2) coordinated public health education on cancer screening and postscreening support in Chinese languages; and 3) replication of the NHIS survey methodology and adaptive application of these instruments across several states and regions, combined with the assessment of screening performance in Chinese American populations.

  PublisherDOI

• Smoking Behavior, Knowledge, and Beliefs Among Korean Americans

  Cancer Practice · 2000-09-01 · 51 citations

  article

  PURPOSE: The purpose of the study was to examine smoking behavior, knowledge, and beliefs among Korean Americans. DESCRIPTION OF STUDY: One hundred four Korean American men and 159 women, 40 to 69 years old, living in Chicago, Illinois, served as study respondents. The National Health Interview Survey (NHIS) Cancer Control Supplement Questionnaire was used to collect data. The NHIS was translated into Korean with minor modifications to develop a culturally appropriate instrument. RESULTS: This study suggests that smoking is almost exclusively a male behavior (38.5%) and that Korean American men smoke mostly cigarettes. Almost 90% of women have never smoked, whereas 23% of men reported never smoking. Respondents with a non-Christian background or no religious affiliation were 16.5 times more likely to be current smokers. Respondents who had lived in the United States less than 10 years were 12.5 times more likely to be current smokers. More than 90% of men, regardless of smoking status, were able to identify an association between smoking and major chronic diseases. CLINICAL IMPLICATIONS: The prevalence of smoking among these Korean American men places them at considerable risk for smoking-related disease. Healthcare providers must be better informed about smoking behavior in this group, and specific attention to recently migrated men and those reporting religions other than Christianity is recommended. Health-protecting strategies for women and children who fall victim to secondhand smoke, or who may be targeted by tobacco advertising, are also an important step in disease prevention for this population.

  PublisherDOI

• A Comparison of Two Ventilator Systems Using an Infant Lung Model

  Anesthesiology · 2000-07-01 · 2 citations

  articleOpen access

  STANDARD adult circle systems (with adult ventilator bellows and carbon dioxide absorber) equipped with pediatric circuit hoses, rather than semiclosed partial rebreathing systems or specially designed pediatric circle systems (with small ventilator bellows and carbon dioxide canister), often are used to ventilate infants and children during administration of anesthesia. 1–3If adult circle ventilator systems are used, it is important to understand the possible limitations and to make necessary modifications of adult techniques for use with infants. One limitation of this equipment for infant ventilation is the difficulty in determining how to set the tidal volume (TV) if using a time-cycled, volume-limited mode of ventilation to ensure that the patient receives the desired TV. The large compression volume of the circle system relative to the infant’s lung volume, 4leaks around uncuffed endotracheal tubes, effects of fresh gas flow (FGF) on delivered TV, and the mechanical difficulty of setting a small TV using an adult bellows assembly contribute to a discrepancy between set and delivered TVs.Recently, the Food and Drug Administration approved the use of a circle anesthesia system equipped with an electronic piston ventilator. This system is designed to accurately deliver small TVs by providing easy-to-use ventilator modes and controls, automatic system compliance compensation, and eliminating the interaction between FGF and TV. As a result, time-cycled, volume-limited ventilation of infants with a piston-driven ventilator may be more “user-friendly” and reliable compared with ventilation with most bellows-equipped ventilators. The purpose of our study was to compare the performance of the Drager Narkomed GS ventilator system (North American Drager, Telford, PA), equipped with a traditional ascending bellows ventilator, with the new Drager Narkomed 6000 ventilator system, which uses a circle anesthesia circuit, in ventilating an infant test lung model.A Drager Narkomed GS circle anesthesia system, equipped with a standard adult bellows and carbon dioxide absorber, and a Drager Narkomed 6000, which incorporates a Divan piston-driven ventilator (Dragerwork, AG, Lubeck, Germany), were compared regarding delivery of minute ventilation (V̇E) to an infant test lung. Both ventilator systems were equipped with a disposable pediatric circle circuit (Pediatric King; King Systems Corporation, Noblesville, IN). The test lung model used in this study has been described previously. 5–8V̇Ewas measured using a test lung (Bio-Tek Ventilator Tester; Bio-Tek Instruments, Winooski, VT). The Bio-Tek test lung includes two wire wool–filled metal canisters that simulate lungs that have either normal compliance (0.003 l/cm H2O) or low compliance (0.001 l/cm H2O), as defined by the American National Standards Institute. 9The test lung determines delivered V̇Eby measuring peak inspiratory pressure (PIP) and multiplying by the calculated lung compliance to determine the TV. V̇Eis calculated by multiplying the TV by the respiratory rate (RR). The accuracy of the test lung for V̇Eis ± 4% for TVs of 5–300 ml in the infant mode. The test lung was connected to the ventilator systems by a 3.5-mm endotracheal tube (Mallinckrodt Medical, St. Louis, MO) cut distally (removing the Murphy eye to prevent system leakage), with a 15-mm connector on each end (fig. 1). The test lung was set for ambient barometric pressure, temperature, and humidity before all testing. At the recommendation of the test lung manufacturer, the least restrictive adapter (parabolic restrictor Rp20) connected the endotracheal tube to the test lung. The study was divided into three parts (fig. 1). During all three parts of the study, an inspiratory-to-expiratory ratio of 1:2 was maintained. No significant leaks in either of the ventilator systems were detected before testing. For each condition tested, V̇Ewas measured three times. The average of these three V̇Emeasurements was used for subsequent data analysis. The V̇Edelivered by the ventilator systems to the test lung were compared during time-cycled, pressure-limited and time-cycled, volume-limited ventilation. To simulate a variety of pediatric conditions, V̇Ewas measured with both ventilator systems using a variety of RRs (20, 30, 40, and 50 breaths/min) and with the test lung set in both normal- and low-compliance infant modes. During time-cycled, pressure-limited trials the PIP was adjusted to 20, 30, 40, and 50 cm H2O. Using the GS ventilator system, the desired PIP was achieved by adjusting the drive gas flow to the bellows to medium, adjusting the bellows upward to the maximal setting, and adjusting the inspiratory pressure limit (“pop-off valve”) to the target PIP. With the 6000 ventilator system, the desired PIP was achieved by direct entry of the desired PIP value into the operation control panel. During time-cycled, volume-limited trials, TVs of 30, 40, 50, 100, 200, and 300 ml were set. With the GS ventilator system this was achieved by visual adjustment of the bellows combined with adjustment of the drive gas flow to the bellows from its initial medium setting upward or downward (if needed) until the desired TV was indicated by the machine’s spirometer. In the 6000 ventilator system, TV was adjusted by direct entry of the desired value into the operation control panel. An FGF of 3 l O2/min was used during all part A testing.Minute ventilation was measured before and after an acute decrease in test lung compliance during time-cycled, volume-limited ventilation. V̇Ewas measured starting with an RR of 20 breaths/min and a TV of 50, 100, or 200 ml, with the test lung set to mimic normal-compliance infant lungs (0.003 l/cm H2O). Then, without changing any ventilator settings, V̇Ewas measured after the test lung compliance was decreased to 0.001 l/cm H2O. An FGF of 3 l O2/min was used during all part B tests. PIP limits of 80 cm H2O for the 6000 ventilator system and maximum for the GS ventilator system were set before all testing.The test lung was set in the normal-compliance infant mode (0.003 l/cm H2O) for all testing. To test the effect of an increasing FGF, baseline V̇Emeasurements were made starting at an FGF of 1 l O2/min and a set TV of 50, 100, or 200 ml, with an RR of 20 breaths/min. Without changing ventilator settings, V̇Ewas measured after incremental increases of FGF to 3, 6, and 10 l/min. To test the effect of decreasing FGF, we reversed the procedure, obtaining baseline V̇Emeasurements starting with an FGF of 10 l O2/min, an RR of 20 breaths/min, and a set TV of 50, 100, or 200 ml. Without changing ventilator settings, the FGF was adjusted incrementally downward to 6, 3, and 1 l/min, and V̇Ewas again measured.The multiple regression technique was used to analyze the data for part A: The dependent variable was V̇E; independent variables were the ventilator systems used (GS, 6000), lung compliance, RR, and PIP (pressure-limited data) or TV (volume-limited data). For parts B and C, the repeated-measures analysis-of-variance technique was used to analyze the data. The dependent variable was V̇E; independent variables were the ventilator systems, TV, and lung compliance (part B) or FGF (part C).During time-cycled, pressure-limited ventilation both the GS and the 6000 ventilator systems generated nearly identical V̇Eover the entire range of PIPs studied in both the compliant and noncompliant infant lung models (P = 0.77 and P = 0.33, respectively;fig. 2). During time-cycled, volume-limited trials, the 6000 ventilator system could be set at all TVs; we were not able to set the GS ventilator system to achieve some higher TVs (especially at high RRs in the low-compliance lung model) or any TV less then 50 ml. Thus, no comparison data points were obtained for those TVs. Only TVs of 50, 100, and 200 ml were compared between the two ventilator systems. In the normal-compliance lung model, the 6000 ventilator system delivered slightly higher V̇Ethan the GS ventilator system, but this difference was not statistically significant (P = 0.18). In the low-compliance lung model, the 6000 ventilator system delivered greater V̇Ethan the GS ventilator system (an average increase in V̇Eof 18%;P = 0.024;fig. 3). As lung compliance was decreased from normal to low, both ventilator systems delivered less V̇E(41–58% less) to the test lung at all TVs studied during time-cycled, volume-limited ventilation (P < 0.001) (fig. 4). The 6000 ventilator system was better able to compensate for decreased lung compliance than the GS ventilator system (P < 0.001). The GS ventilator system delivered progressively more V̇Eto the test lung as FGF was increased from 1 to 10 l/min at all TVs studied (P < 0.001 for FGF, P < 0.001 forTV). The GS ventilator system delivered progressively less V̇Eto the test lung as FGF was decreased from 10 to 1 l/min at all TVs studied (P < 0.001 for FGF, P < 0.001 for TV) (fig. 5A). The 6000 ventilator system maintained nearly identical V̇Eas FGF was increased from 1 to 10 l/min at all three TVs studied (P = 0.14 for FGF, P < 0.001 for TV) or as FGF was decreased from 10 to 1 l/min at all three TVs studied (P = 0.07 for FGF, P < 0.001 for TV) (fig. 5B). We observed nearly identical performance of the GS and 6000 ventilator systems during time-cycled, pressure-limited ventilation over a wide range of RRs and PIPs and two test lung compliances. During time-cycled, volume-limited ventilation trials, at TVs that could be obtained in both systems being tested, the 6000 ventilator system delivered slightly greater V̇Ethan the GS ventilator system (an average increase of 18% as measured by the Bio-Tek test lung). This difference between systems may reflect in part how the TV was set on the GS ventilator as well as differences between the spirometers of the two systems. Smaller TVs (50 or 100 ml) were extremely difficult to set accurately with the GS ventilator system, requiring visual setting of the bellows (with 50-ml TV, the bellows was fully “seated” at the bottom of the bellows assembly) followed by adjustment of the driving gas flow to the bellows. TVs below 50 ml were not obtainable at all with the GS ventilator system (the machine’s digital spirometer display of TV does not register such low TVs). Substantial decreases in V̇Ewere observed with both ventilator systems as compliance decreased, at all TVs studied. The 6000 ventilator system was marginally better able to maintain V̇Ewith decreasing lung compliance. Changing FGF during time-cycled, volume-limited ventilation does not effect V̇Ewith the 6000 ventilator system but does influence V̇Ewith the GS system.Based on our in vitro findings, what can we conclude about possible advantages or disadvantages of a piston-driven ventilator system compared with a traditional bellows ventilator system during infant ventilation? Pediatric anesthesiologists often use the ventilator of an adult circle system in the time-cycled, pressure-limited ventilation mode during infant anesthesia because of their familiarity with this type of ventilation and the mechanical ease of setting a target PIP limit with most ventilators. Our study indicates that during time-cycled, pressure-limited ventilation, it does not make a meaningful difference if one uses either a bellows-equipped ventilator or a piston-driven ventilator; the systems deliver equivalent volumes to the infant test lung over a wide range of RRs and PIPs. The near equivalence of the V̇Eproduced by the GS and 6000 ventilator systems during time-cycled, pressure-limited ventilation reinforces observations made in prior publications using this same lung model. 5–8During time-cycled, pressure-limited ventilation, V̇Eis dependent on lung compliance, PIP achieved, and RR, regardless of the compliance of the circuit used, the precise method of achieving a given PIP with the circle system, and the ventilator system used to achieve a given PIP (Mapleson system, circle system, or free-standing ventilator). 5–8One potential disadvantage of time-cycled, pressure-limited ventilation is that if for whatever reason there were a sudden change in lung compliance or resistance in the system, such as a surgeon leaning on the chest of an infant or a kinked endotracheal tube, there would be no change in the PIP, and there would be a decrease in delivered ventilation. Other means of monitoring respirations, however, such as auscultation of breath sounds and measured expired carbon dioxide (including the configuration of the wave form), likely would diagnose such problems. In the above scenario, with time-cycled, volume-limited ventilation there would be a sudden rise in peak inflation pressure as well as changes in breath sounds and the carbon dioxide waveform, but TV might be maintained better. Our study did not assess these clinically relevant means of assessing ventilation but rather just examined the performance of each ventilator system under extreme changes in lung compliance.The GS and 6000 ventilator systems do not perform equally during time-cycled, volume-limited ventilation. The GS ventilator system cannot be used easily as a true volume-limited ventilator. Determination of an appropriate set TV based on patient weight is cumbersome. Badgwell et al. 4have described the nonlinear relationship between patient weight and set TV required for time-cycled, volume-limited ventilation in infants using adult ventilator systems (150–200 ml/kg in a 1-kg infant vs. 25 ml/kg in infants more than 10 kg). Once calculated, the smaller TVs required for infants may be mechanically difficult to set because of the lack of precision of the adult bellows assembly. The lowest TV easily set during our study trials was 200 ml, which is the first mark on the bellows assembly. Thus, those who choose to use adult circle systems for infant ventilation often adjust the volume limit of the bellows slowly upward until the desired chest expansion or target PIP is achieved. An initial PIP of approximately 20 cm H2O usually is chosen, and further adjustment of the TV upward or downward is based on chest expansion, end tidal carbon dioxide concentration, and oxygen saturation. This type of time-cycled, volume-limited ventilation might be more accurately described as time-cycled, volume-limited, pressure-guided ventilation.The 6000 ventilator system, in contrast to the GS system, is easily set for all TVs during time-cycled, volume-limited ventilation, including TVs less than 50 ml. The ability to set accurate infant TVs, along with the consistency in V̇Ewith changing FGF, would appear to be an advantage of the 6000 ventilator system for use with infants. Peters et al. 10reported successful time-cycled, volume-limited ventilation of 20 infants between 2 and 6 kg with TVs of 10 ml/kg at RRs between 25 and 40 breaths/min, using a piston-driven ventilator system. Such low TVs are not easily obtainable using the GS ventilator system. It is possible to set the GS ventilator to very low TVs by setting the bellows at the very lowest limit and then adjusting the drive gas flow to the bellows so that the desired TV is achieved; however, these low TV settings are below the technical limits of the GS spirometer and would necessitate assessment of efficacy purely on a clinical basis. Also, with any change in FGF, set TV would need to be readjusted (i.e. , if FGF were increased, set TV would need to be decreased to maintain constant V̇E; if FGF were decreased, set TV would need to be increased to maintain constant V̇E). The consistency in V̇Eover a wide range of FGFs we observed using the 6000 ventilator system is similar to results reported by Schirmer et al. 11in a test lung study using a piston-driven ventilator: TVs ranging from 20–200 ml were delivered reliably during time-cycled, volume-limited ventilation over a range of FGFs (1–6 l/min). When using the 6000 ventilator system, once an appropriate set TV has been achieved, FGF can be adjusted over a wide range without risk of inadequate ventilation (with a decrease in FGF) or overventilation or barotrauma (with an increase in FGF).Another design difference between the GS and 6000 ventilator systems as used for time-cycled, volume-limited ventilation is the response to a changing lung compliance. Our results show that the 6000 ventilator system has some ability to compensate for compliance changes; the GS ventilator system does not. Because the compensation for a decrease in lung compliance by the 6000 ventilator system is incomplete, the clinical advantage of this compliance feature needs further evaluation; a set TV may require significant upward adjustment to maintain V̇Eas lung compliance decreases, regardless of the ventilator system used. The conclusion we have reached based on our in vitro study is consistent with results reported by Schirmer et al. 11using a piston-equipped ventilator in an animal model. In that study, using newborn piglets, decreased lung compliance was induced by creation of a tension pneumothorax. Although the piston-equipped ventilator had an improved ability to maintain constant ventilation after induction of the pneumothorax, it was not able to maintain normal ventilation in several piglets. 12The actual lung compliance of the piglets may have been different from the compliance settings we studied, so that direct comparison of results is not possible. Further studies would be required to examine the clinical importance of the compensation provided by the 6000 ventilator because the acute changes in compliance that we studied may have been more extreme than those that would be observed in most clinical settings.Our study indicates that the piston-equipped Drager Narkomed 6000 ventilator system performs in a manner similar to the traditional ascending bellows-equipped Drager Narkomed GS ventilator system during time-cycled, pressure-limited ventilation. During time-cycled, volume-limited ventilation, however, the 6000 ventilator system can be set easily to achieve small TVs, but the GS ventilator system cannot. More importantly, the 6000 ventilator system allows maintenance of a constant TV during a wide range of FGFs, without further adjustment. Regardless of the ventilator system used, or the type of ventilation that is chosen (time-cycled, pressure limited vs. time-cycled, volume-limited), significant adjustment of ventilator parameters is required to maintain ventilation if lung compliance changes.It is important to emphasize that this study evaluated only the ability of each ventilator system to deliver V̇Eto a test lung; our study did not address other potential issues related to clinical use of these ventilator systems. Further studies are warranted to evaluate the clinical role of the 6000 ventilator system during infant anesthesia compared with other available systems.

  PublisherOA PDFDOI

Frequent coauthors

• Shu‐Pi C. Chen

  77 shared

• Virginia M. Ohlson

  University of Illinois Chicago

  61 shared

• Violet H. Barkauskas

  60 shared

• G. W. Stevenson

  36 shared

• Michael Tobin

  District of Columbia Water and Sewer Authority

  35 shared

• Steven C. Hall

  University of California, San Francisco

  35 shared

• Babette Horn

  35 shared

• Charles J. Coté

  35 shared