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Posted August 2, 2001; 10:28 a.m.
Laura Spinney, a graduate student in the Department of Ecology and Evolutionary Biology, has received a research grant from Sigma Xi, an honor society of scientists and engineers.
The $350 will support Spinney's study entitled "Timing of Breeding in the Cocos Finch." She will try to determine why the Cocos finch, a species of Darwin's finch found exclusively on Cocos Island north of the Galapagos, breeds during dry seasons. Other species of Darwin's finch typically breed during rainy seasons. Michaela Hau, assistant professor of ecology and evolutionary biology, will supervise Spinney's research.
The support is provided through Sigma Xi's Grants-in-Aid of Research Program, which provides small awards to young researchers. Receiving a grant from this prestigious program often is one of the early steps in an accomplished career in science, according to the society.
Contact: Marilyn Marks (609) 258-3601


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Topic Title
- Nitrous Oxide for the Management of Labor Pain
- Research Review Aug. 23, 2012
Related Products for this Topic
- Research Protocol May 11, 2011
- Disposition of Comments Report Dec. 10, 2012
Original Nomination
Executive Summary – Aug. 23, 2012
Nitrous Oxide for the Management of Labor Pain
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Table of Contents
- Background
- Objectives
- Key Questions
- Analytic Framework
- Methods
- Results
- Discussion
- Conclusions
- References
- Full Report
- For More Copies
More than 4 million births occur in the United States each year; in 2008, there were 4,247,694 births.1 The most commonly used labor pain management method in the United States is epidural analgesia (hereafter epidural).2 Use of inhaled nitrous oxide is a common option for labor pain management in several countries outside the United States, including the United Kingdom, Finland, Sweden, Canada, Australia, and New Zealand. Only five centers in the United States are known to currently provide nitrous oxide as an option for labor pain management: the Birth Center at the University of California San Francisco Medical Center; the University of Washington Hospital in Seattle; St. Joseph Regional Medical Center in Lewiston, ID; Okanogan Douglas Hospital in Brewster, WA; and Vanderbilt University Medical Center in Nashville, TN (which began offering nitrous oxide in June 2011 after this review was under way). A significant barrier to use in the United States is limited availability of equipment to blend and deliver a mixture of nitrous oxide and oxygen for self-administration by laboring women.
Nitrous oxide, sometimes called "laughing gas" because it can produce euphoria, is an inhalational anesthetic and analgesic gas. Nitrous oxide has been used in dental care since the mid-1800s3 and is commonly used for this indication today. Use of nitrous oxide during labor began in the late 1800s, and equipment for self-administration was introduced by Minnitt in England in 1934.4
The mechanism of action of nitrous oxide is thought to be an increased release of endorphin, dopamine, and other natural pain relievers in the brain, which modulate pain stimuli via descending spinal cord nerve pathways. Nitrous oxide does not completely relieve the pain of labor but creates "diminished pain, or a continued awareness of pain without feeling bothered by it."5 Nitrous oxide also has an antianxiety effect, which may be helpful if laboring women are restless and doubt their ability to cope, emotions that are not uncommon, especially during transition (see Figure A for an overview of the stages of labor).
Figure A. Stages of labor
The most common concentration of nitrous oxide administration for labor pain management in the biomedical literature and in current clinical practice is 50 percent nitrous oxide in oxygen, which can be mixed from two separate gas sources with a blender device (e.g., Nitronox®) or premixed in a single cylinder (e.g., Entonox®). Nitrous oxide is usually self-administered via a facemask or mouthpiece on an intermittent basis, beginning about 30 to 60 seconds before each contraction.6
A variety of pain management methods were described in studies in this review (Table A). Epidural analgesia is the most commonly used method in the United States and may block pain entirely. Although epidurals are more effective for pain relief than other pain management methods, epidurals are associated with increased risk of assisted (vacuum or forceps) vaginal birth, use of oxytocin, maternal hypotension, motor blockade, urinary retention, maternal fever, and cesarean for maternal distress.7 Women who have epidurals must have additional monitoring and may need confinement to bed, which limits mobility and options for positioning, and placement of a Foley catheter.
Although nitrous oxide would not be expected to be as effective for analgesia as an epidural because of the differences in their mechanism of action, nitrous oxide has other benefits, including its lower cost and less invasive nature. Nitrous oxide has a rapid onset and end of action. Thus women who do not like nitrous oxide or find it inadequate for pain management can easily discontinue its use and switch to another method, unlike epidurals and systemic opioids, which diminish gradually over a much longer period. Mobility and options for positioning are not limited and nitrous oxide does not require additional monitoring and potential anesthesia-related interventions (e.g., bladder catheterization). Women self-administer nitrous oxide, which allows them to control the amount they need.8 Nitrous oxide may not be an ideal method for women who want maximum pain relief, but it could be preferable to other pharmacologic pain management methods for women who want increased mobility with less intervention and monitoring. Nitrous oxide might also be useful when a woman wants to delay use of epidural anesthesia until later in labor, when epidural anesthesia is not immediately available (e.g., in hospitals that do not have in-house anesthesia staff and must call in an anesthesia provider), when a woman arrives at the hospital too far along in labor to allow for an epidural to be placed and take effect, and when a woman finds epidural analgesia ineffective or inadequate.
One concern with nitrous oxide use is the potential for the gas to escape into the room and potentially affect health care workers as well as other individuals present with laboring women. For this reason, multiple organizations are responsible for regulating the use of nitrous oxide, and factors other than clinical outcomes are important to decisionmaking about its use (Appendix F). Room ventilation systems and scavenging systems that remove waste gases are used to reduce exposure to caregivers and others present for labor. Equipment capable of scavenging provides constant negative pressure so that the woman's exhalations, which contain nitrous oxide, are captured and removed from the room and facility.6
Finding the appropriate measure of effectiveness on which to assess nitrous oxide with other pain management methods is challenging. Nitrous oxide is not intended to provide the extent of pain relief expected with epidural. Therefore, rather than a direct comparison of effectiveness, the more important questions are whether women are satisfied with the use of nitrous oxide for labor pain management and if it is safe for the woman and her fetus/newborn.
|Timing and Frequency of Administration
|Nitrous oxide
|Other inhalational anesthetic gases (desflurane, sevoflurane, isoflurane, enflurane, methoxyflurane, trichloroethylene, cyclopropane)
|Opioids (for example, pethidine/meperidine)
|Paracervical block
|Pudendal block
|Transcutaneous electrical nerve stimulation (TENS)
|Sterile water injections
Scope of this Report
Most women in the United States use some type of medication for labor pain management. However, the option of using nitrous oxide to relieve labor pain is limited by its lack of availability. Use of nitrous oxide during labor is common in other countries, increasing interest in this method in the United States, in part because it is less expensive and invasive than widely used regional anesthesia. This review attempts to assess the effectiveness of nitrous oxide in managing labor pain and to identify potential factors that may influence its availability and use within the United States. Our Key Questions have been structured with this goal in mind. The primary questions include the comparative effectiveness of nitrous oxide for the management of labor pain, the influence of nitrous oxide on women's satisfaction with their birth experience, the health system factors influencing its use within the United States, and any adverse effects associated with this intervention. With the rate of cesarean birth continuing to rise—32.3 percent of all U.S. births reported in 20081—it is also important to address whether the use of nitrous oxide during labor influences the route of birth in women initially intending a vaginal birth.
We focused this review on pregnant women in first and second stages of labor, other attendees and health care providers present during labor, and the fetus/neonate.
We examined the use of nitrous oxide for the management of labor pain.
We compared nitrous oxide with the following pain management methods: no analgesic/anesthetic intervention, other inhalational anesthetic gases, epidural, opioids, paracervical block, pudendal block, transcutaneous electrical nerve stimulation (TENS), sterile water injections, hydrotherapy, and psychoprophylaxis (see Table A).
Our primary outcomes included pain management, satisfaction with pain management, satisfaction with birth experience, effect of nitrous oxide on the route of birth, adverse effects associated with the use of nitrous oxide for the management of labor pain, and health system factors associated with the use of nitrous oxide for the management of labor pain.
Intermediate outcomes include associated labor outcomes, while long-term outcomes include associated birth outcomes. We did not place a restriction of the duration of followup.
We considered all birth settings, including hospital, birth center, and home.
Key Questions
- What is the effectiveness of nitrous oxide when compared with other methods for the management of labor pain among women intending a vaginal birth?
- What is the comparative effectiveness of nitrous oxide on women's satisfaction with their birth experience and pain management?
- What is the comparative effectiveness of nitrous oxide on the route of birth?
- What is the nature and frequency of adverse effects associated with the use of nitrous oxide for the management of labor pain, including but not limited to:
- Maternal adverse effects, such as nausea and vomiting, dreams, dizziness, unconsciousness, and postpartum complications.
- Fetal/neonatal adverse effects, such as low Apgar scores and abnormal fetal cord blood gases.
- Childhood adverse effects, such as drug dependency and developmental complications.
- Adverse effects on health care providers and other individuals present for labor.
- What are the health system factors influencing the use of nitrous oxide for the management of labor pain, including but not limited to provider preferences, availability, setting, and resource utilization?
Analytic Framework
We developed the analytic framework (Figure B) based on clinical expertise and refined it with input from our key informants and Technical Expert Panel (TEP) members. The figure represents the population of interest, women intending a vaginal birth, and the factors and decision points that influence the use of nitrous oxide for the management of labor pain. The initial preference for pain management methods, which is often determined prior to the onset of labor, can be shaped by past birth experience, cultural or familial influence, and knowledge of various pain management options. Women acquire knowledge about pain management options from a variety of sources including health care providers, childbirth educators, patient education books and other materials, popular media, friends, and family. Once labor begins, health system factors such as availability, setting, and provider preference may affect the utilization of the desired pain management methods (Key Question [KQ] 5). The first two decision points reflect the initial preference for and actual implementation of pain management methods. A third decision point occurs after the onset of labor but prior to birth, at which point the woman in labor may opt to modify the pain management method. We sought to examine how the administration of nitrous oxide at various mixes, routes, and intervals affects outcomes that occur during labor, after birth, and in the long term (KQs 1–3). Adverse effects of treatment are examined in KQ4. Portions of the framework that are unexplored in the scientific literature are highlighted in the discussion of future research needs.
Figure B. Analytic framework for nitrous oxide for the management of labor pain
Input From Stakeholders
The topic was nominated in a public process. With key informant input, we drafted initial KQs, which were reviewed by the Agency for Healthcare Research and Quality (AHRQ) and posted to a public Web site for public comment. Using public input, we drafted final KQs, which were reviewed by AHRQ. We convened a technical expert panel to provide input during the project on issues such as setting inclusion/exclusion criteria and refining the analytic framework
Literature Search
Our search included the MEDLINE®, Embase, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases. Reviews conducted by the Cochrane Collaboration are indexed in the MEDLINE database and were also included in the search. We also hand-searched references of included articles to identify additional studies. Controlled vocabulary terms served as the foundation of our search, complemented by additional keyword phrases to represent the myriad ways in which nitrous oxide is referred to in the clinical literature. We also employed indexing terms within each database to exclude ineligible publication types and articles in languages other than English.
Inclusion and Exclusion Criteria
We excluded studies that:
- Were not original research
- Did not include 20 or more pregnant women in labor
- Did not address adverse effects or occupational exposure during labor
- Did not report information pertinent to any KQ
- Were not published in English
Article Selection Process
We examined abstracts of articles to determine whether studies met our criteria. Two reviewers separately evaluated the abstracts for inclusion or exclusion. If one reviewer concluded the article could be eligible for the review based on the abstract, we retained it. Full publications were then dually reviewed for final inclusion, with disagreements resolved via adjudication by an independent third reviewer. Reasons and process for exclusions are described in the full report.
Data Extraction
All team members shared the task of entering information into evidence tables. After initial data extraction, another member checked table entries for accuracy, completeness, and consistency. Abstractors reconciled inconsistencies.
Quality Assessment
The quality of individual studies was assessed using existing, widely accepted tools for each type of study. For randomized controlled trials (RCTs), the Cochrane Risk of Bias tool was employed. Fundamental domains include: adequate sequence generation, allocation concealment, blinding, incomplete outcome data addressed, and free of selective reporting bias. For nonrandomized and observational studies, the Newcastle-Ottawa Quality Assessment Scale was utilized. The scale assesses three broad perspectives: (1) the selection of the study groups; (2) the comparability of the groups; and (3) the ascertainment of either the exposure or outcome of interest for case-control or cohort studies, respectively. Both tools are presented in the full report. Additionally, the thresholds for converting the Cochrane Risk of Bias tool and Newcastle-Ottawa Quality Assessment Scale results to the AHRQ standard of "good," "fair," and "poor" quality designations are presented in the full report.
Evidence Synthesis
Text that summarizes the research evidence is organized by KQ. Within each KQ, evidence is organized by aspects of the question, such as the compared intervention and outcomes. In the full report, we include evidence tables for individual studies and summary tables of common outcomes and provide extended analysis.
Grading Strength of Evidence
We evaluated the overall strength of the evidence for the primary outcomes. We graded available evidence for each key outcome for each of the following domains:
- risk of bias (low, medium, or high),
- consistency of findings (inconsistency not present, inconsistency present, or unknown or not applicable),
- directness (direct comparison of influence on outcomes in RCT, or indirect information from observational research), and
- precision (precise or imprecise based on outcomes rates, size of the individual studies and the total number of women in the studies for the category of intervention).
We combined the grades of each domain to develop the strength of evidence for each key outcome. Possible grades for each domain were: low, moderate, or high risk of bias; consistent or inconsistent; direct or indirect; and precise or imprecise. We considered additional domains, including publication bias and large effect size, on a per-KQ basis.
We graded the body of literature for effectiveness of nitrous oxide, women's satisfaction with their birth experience and pain management, effect of nitrous oxide on route of birth, and adverse effects associated with nitrous oxide. The possible grades were:
High: High confidence that the evidence reflects the true effect. Further research is unlikely to change estimates.
Moderate: Moderate confidence that the evidence reflects the true effect. Further research may change our confidence in the estimate of effect and may change the estimate.
Low: Low confidence that the evidence reflects the true effect. Further research is likely to change confidence in the estimate of effect and is also likely to change the estimate.
Insufficient: Evidence is either unavailable or does not permit a conclusion.
When no studies were available for an outcome or comparison of interest, we assessed the evidence as insufficient. Two reviewers independently graded the body of evidence; disagreements were resolved through discussion or a third reviewer adjudication.
Literature Search Yield
We identified 1,428 nonduplicate titles or abstracts. Fifty-eight publications were included in the review (Figure C), representing 59 distinct study populations: 13 RCTs, 7 crossover RCTs, 4 nonrandomized clinical trials, 14 prospective cohorts, 1 retrospective cohort, 3 case series, 4 case-control studies, 11 cross-sectional studies, and 2 trend studies. The most common reasons for exclusion were irrelevance to the topic and ineligible study size. Twenty-one articles pertain to KQ1, 9 articles to KQ2, 6 articles to KQ3, 49 articles to KQ4, and 0 articles to KQ5.
Figure C. Disposition of articles identified by the search strategy
KQ = Key Question
*The number of articles addressing Key Questions and those excluded exceed the total number of articles in each category because some articles fit multiple exclusion categories or addressed more than one Key Question.
KQ1. Effectiveness of Nitrous Oxide for Labor Pain Management
Twenty-one studies addressed the effect of nitrous oxide on pain or pain relief.9-29 Four studies were of fair quality,19,22-23,25 and 17 were of poor quality.9-18,20-21,24,26-29 There was considerable variation in the concentration of nitrous oxide and frequency (continuous vs. intermittent) administered, additional pain management methods used, and methods and persons (i.e., women, obstetricians, midwives, and anesthesia providers) assessing pain and pain relief. The substantial variation in timing of assessment may have affected the reported outcomes because women's opinions about pain relief change with time lapsed after birth.10-11,14
The majority of the effectiveness studies (12 of 21) had as comparators other inhalational anesthetic gases that are not used to manage labor pain in the United States. Only one study compared nitrous oxide with placebo and found no significant difference in pain scores. As expected, epidurals provide more effective pain relief than nitrous oxide. The evidence is insufficient to determine the effectiveness of nitrous oxide for the management of labor pain compared with other, nonepidural labor pain management methods because the studies are predominately of poor quality, use heterogenous outcome measures, and have inconsistent findings.
KQ2. Effect of Nitrous Oxide on Women's Satisfaction
Nine studies addressed women's satisfaction with their birth experience or pain management.16-17,20-21,24,27,30-32 One study was of good quality,31 one of fair quality,32 and seven of poor quality.16-17,20-21,24,27,30 Measures of satisfaction were not uniform, making it difficult to synthesize studies. The strength of the evidence is low for equivalence or superiority of nitrous oxide compared with other pain management methods for women's satisfaction with their birth experience and pain management.
KQ3. Effect of Nitrous Oxide on the Route of Birth
Six studies compared the route of birth in women who used nitrous oxide with that in women who used other pain management methods.10,14,17,24,27,31 Two of these included only women who had vaginal births,10, 17 and five were of poor quality.10,14,17,24,27 The evidence is insufficient to determine the effect of nitrous oxide on the route of birth because the studies are predominately of poor quality and have inconsistent findings.
KQ4. Adverse Effects of Nitrous Oxide for Labor Pain Management
Forty-nine studies addressed the maternal, fetal, neonatal, and occupational harms related to nitrous oxide use during labor.9-14,17-21,24,26,29,31,33-65 Two were of good quality,31,54 7 of fair quality,19,33,45,47,57,59,66 and 40 of poor quality.9-14,17-18,20-21,24,26,29,34-44,46,48-53,55-56,58,60-65 Although these 49 studies report data from more than 27,000 women, only 6 were conducted in the United States (n = 2,445 women).
One-third (16 of 49) of studies reporting harms were conducted prior to 1980, when nitrous oxide was often used in combination with sedatives, tranquilizers, and other inhaled anesthetics in labor, a practice that has largely been abandoned. Studies reporting harms associated with sedative analgesic regimens may not translate effectively to contemporary labor analgesia practice. For example, in older studies, amnesia in labor was considered to be a positive outcome.
Most maternal harms reported in the literature were unpleasant side effects that affect tolerability (e.g., nausea, vomiting, dizziness, and drowsiness). Some maternal harms (e.g., nausea and oxygen desaturation) are common in all laboring women regardless of the type of analgesia used. Study sizes were inadequate to assess for unusual or rare harms that might be more serious.
Nitrous oxide is transmitted via the placenta and is rapidly eliminated by the neonate following birth once breathing begins. Apgar scores in newborns whose mothers used nitrous oxide did not differ significantly from those of newborns whose mothers used other labor pain management methods or no analgesia. Followup of newborns was short, most frequently lasting only to birth or discharge of the neonate from the hospital.
Few data are available to draw conclusions regarding potential occupational harms as a result of exposure to nitrous oxide. Evidence about occupational levels of nitrous oxide is limited, and some studies were conducted prior to the use of room ventilation systems or scavenging systems. The implementation of these systems in clinical practice has reduced occupational exposure, which should mitigate potential risks.
KQ5. Effects of Provider and Health System Factors
No studies addressed KQ5.
Summary Strength of Evidence and Findings
Overall, the strength of evidence to answer the KQs was insufficient for effectiveness for the management of labor pain (KQ1), route of birth (KQ3), and health system factors (KQ5); low for satisfaction with birth experience and pain management (KQ2); and moderate for harms (KQ4) (Table B). Deficiencies in the strength of evidence most often related to a preponderance of study designs with high risk of bias; inconsistent findings across studies and inconsistencies among outcomes that would be expected to show corresponding benefit; use of intermediate outcomes; and small studies with poor precision.
|Total Studies (Total Participants)
|Domains Pertaining to Strength of Evidence
|Strength of Evidence
|Risk of Bias
|Note: Domains pertaining to SOE are taken from the AHRQ Methods Guide and are explained in the Methods section.
KQ = Key Question; RCT = randomized controlled trial
|Effectiveness of nitrous oxide vs. other, nonepidural labor pain management methods for the management of labor pain (KQ1)
|25 (15,991)
|Insufficient; includes 6 RCTs; 5 studies of fair quality and 20 studies of poor quality total
|Equivalence or superiority of nitrous oxide vs. other labor pain management methods for women's satisfaction with their birth experience (KQ2)
|2 (1,303)
|Low; includes no RCTs; 1 study of fair quality and 1 study of poor quality total
|Equivalence or superiority of nitrous oxide vs. other labor pain management methods for women's satisfaction with their pain management (KQ2)
|8 (2,825)
|Low; includes 2 RCTs; 1 study of good quality and 7 studies of poor quality total
|Effect of nitrous oxide for the management of labor pain on route of birth (KQ3)
|6 (33,031)
|Insufficient; includes 2 RCTs; 1 study of good quality and 5 studies of poor quality total
|Adverse effects associated with nitrous oxide for the management of labor pain are primarily unpleasant side effects that affect tolerability (KQ4)
|48 (27,530)
|Moderate; includes18 RCTS; 2 studies of good quality, 6 studies of fair quality, and 40 studies of poor quality total
Applicability describes the extent to which study populations and characteristics in the literature reviewed apply to the larger population. In this report, the study populations were healthy women in labor who should be similar to the target population. Most studies used a 50/50 mix of nitrous and oxygen, often premixed in the form of Entonox®. The 50/50 mix is available, although Entonox is not used in the United States and has not been reviewed by the U.S. Food and Drug Administration. In addition, mechanical equipment for administration of nitrous oxide in labor and delivery has very limited availability in the United States at the time of this writing. The comparators include standard pain management methods, such as epidural, narcotics, and nonpharmacologic methods such as TENS. However, some comparators are not commonly used and/or available for laboring women, such as other inhalational anesthetic gases.
For KQ1, the most frequent outcome was an assessment of pain, generally during labor but sometimes in the immediate postpartum period and/or weeks to months after birth. Those assessing outcomes included participants, obstetricians, midwives, and anesthesia providers. These studies are unable to demonstrate whether nitrous provided adequate pain relief for women who knowingly accept less effective pain relief in exchange for increased mobility, less intervention and monitoring, and avoidance of potential complications associated with epidurals. Generally speaking, therefore, pain relief is likely to be an inadequate measure of effectiveness for nitrous oxide in the absence of other outcomes such as women's satisfaction. Satisfaction with pain management and the birth experience were assessed in KQ2. Satisfaction is a more relevant measure of effectiveness than assessment of pain because nitrous oxide is not intended to provide complete pain relief. The outcomes for KQ3 were vaginal birth, assisted vaginal birth, and cesarean. For KQ4, the most frequent outcomes were assessments of nausea, vomiting, dizziness, drowsiness, hypoxia, oxygen saturation, Apgar scores, and cord blood gases.
Only 6 of 58 studies were conducted in the United States. The options for labor pain management in the United States are somewhat dissimilar to those in other countries because nitrous oxide for laboring women is widely available outside of the United States, whereas in this country its availability is extremely limited. All of the studies were conducted in hospitals; thus, the effectiveness, women's satisfaction, route of birth, and harms associated with nitrous oxide in birth centers and the home setting have not been reported.
The literature addressing nitrous oxide for the management of labor pain has few studies of good or fair quality. Synthesis of effectiveness and satisfaction studies was challenging because of heterogenous interventions, comparators, and outcome measures. Satisfaction may be a more relevant measure of effectiveness than assessment of pain because nitrous oxide is not intended to provide complete pain relief. The strength of evidence for the effect of nitrous oxide on route of birth was insufficient. Most maternal harms reported in the literature were unpleasant side effects that affect tolerability (e.g., nausea, vomiting, dizziness, and drowsiness), and Apgar scores did not differ significantly across labor pain management methods. Data for occupational harms were limited. Research assessing nitrous oxide is needed across all of the KQs examined: effectiveness, women's satisfaction, route of birth, harms, and health system factors affecting use.
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- Ross JA, Tunstall ME, Campbell DM, et al. The use of 0.25% isoflurane premixed in 50% nitrous oxide and oxygen for pain relief in labour. Anaesthesia. 1999 Dec;54(12):1166-72.
- Arfeen Z, Armstrong PJ and Whitfield A. The effects of Entonox and epidural analgesia on arterial oxygen saturation of women in labour. Anaesthesia. 1994 Jan;49(1):32-4.
- Landon MJ, Creagh-Barry P, McArthur S, et al. Influence of vitamin B12 status on the inactivation of methionine synthase by nitrous oxide. Br J Anaesth. 1992 Jul;69(1):81-6.
- Reed PN, Colquhoun AD, and Hanning CD. Maternal oxygenation during normal labour. Br J Anaesth. 1989 Mar;62(3):316-8.
- Arthurs GJ and Rosen M. Self-administered intermittent nitrous oxide analgesia for labour. Enhancement of effect with continuous nasal inhalation of 50 per cent nitrous oxide (Entonox). Anaesthesia. 1979 Apr;34(4):301-9.
- Rosen M, Latto P, and Asscher AW. Kidney function after methoxyflurane analgesia during labour. Br Med J. 1972 Jan 8;1(5792):81-3.
- Phillips TJ and Macdonald RR. Comparative effect of pethidine, trichloroethylene, and Entonox on fetal and neonatal acid-base and PO2. Br Med J. 1971 Sep 4;3(5774):558-60.
- Clinical trials of different concentrations of oxygen and nitrous oxide for obstetric analgesia. Report to the Medical Research Council of the Committee on Nitrous Oxide and Oxygen Analgesia in Midwifery. Br Med J. 1970 Mar 21;1(5698):709-13.
- Stirk P, Staines J, and Brown DW. Maternal diamorphine administration during labour: the effect on neonate admissions to NNU. J Neonatal Nurs. 2002;8(2):56-7.
- Constantine G, Luesley DM, O'Connor A, et al. The use of Entonox in conjunction with a rebreathing humidifier. J Obstet Gynaecol. 1989;10(1):23-25.
- Murphy JF, Dauncey M, and Rees GAD. Obstetric analgesia, anaesthesia and the Apgar score. Anaesthesia. 1984;39(8):760-763.
- Arora S, Tunstall M, and Ross J. Self-administered mixture of Entonox and isoflurane in labour. Int J Obstet Anesth. 1992 Sep;1(4):199-202.
- McAneny T and Doughty A. Self-administered nitrous-oxide/oxygen analgesia in obstetrics. Anaesthesia. 1963 1963;18(4):488-497.
- Mills GH, Singh D, Longan M, et al. Nitrous oxide exposure on the labour ward. Int J Obstet Anesth. 1996 Jul;5(3):160-4.
- Bodin L, Axelsson G and Ahlborg G, Jr. The association of shift work and nitrous oxide exposure in pregnancy with birth weight and gestational age. Epidemiology. 1999 Jul;10(4):429-36.
- Ahlborg G, Jr., Axelsson G and Bodin L. Shift work, nitrous oxide exposure and subfertility among Swedish midwives. Int J Epidemiol. 1996 Aug;25(4):783-90.
- Axelsson G, Ahlborg G, Jr. and Bodin L. Shift work, nitrous oxide exposure, and spontaneous abortion among Swedish midwives. Occup Environ Med. 1996 Jun;53(6):374-8.
- Einarsson S, Stenqvist O, Bengtsson A, et al. Gas kinetics during nitrous oxide analgesia for labour. Anaesthesia. 1996 May;51(5):449-52.
- Nyberg K, Allebeck P, Eklund G, et al. Socio-economic versus obstetric risk factors for drug addiction in offspring. Br J Addict. 1992 Dec;87(12):1669-76.
- Westling F, Milsom I, Zetterstrom H, et al. Effects of nitrous oxide/oxygen inhalation on the maternal circulation during vaginal delivery. Acta Anaesthesiol Scand. 1992 Feb;36(2):175-81.
- Zack M, Adami HO and Ericson A. Maternal and perinatal risk factors for childhood leukemia. Cancer Res. 1991 Jul 15;51(14):3696-701.
- Jacobson B, Nyberg K, Gronbladh L, et al. Opiate addiction in adult offspring through possible imprinting after obstetric treatment. Br Med J. 1990 Nov 10;301(6760):1067-70.
- Jacobson B, Nyberg K, Eklund G, et al. Obstetric pain medication and eventual adult amphetamine addiction in offspring. Acta Obstet Gynecol Scand. 1988;67(8):677-82.
- Westberg H, Egelrud L, Ohlson CG, et al. Exposure to nitrous oxide in delivery suites at six Swedish hospitals. Int Arch Occup Environ Health. 2008;81(7):829-836.
- Marx GF, Joshi CW, and Orkin LR. Placental transmission of nitrous oxide. Anesthesiology. 1970 May;32(5):429-32.
- Paech MJ. The King Edward Memorial Hospital 1,000 mother survey of methods of pain relief in labour. Anaesth Intensive Care. 1991 Aug;19(3):393-9.
- Zelcer J, Owers H, and Paull JD. A controlled oximetric evaluation of inhalational, opioid and epidural analgesia in labour. Anaesth Intensive Care. 1989 Nov;17(4):418-21.
- Deckardt R, Fembacher PM, Schneider KT, et al. Maternal arterial oxygen saturation during labor and delivery: pain-dependent alterations and effects on the newborn. Obstet Gynecol. 1987 Jul;70(1):21-5.
- Talebi H, Nourozi A, Jamilian M, et al. Entonox for labor pain: a randomized placebo controlled trial. Pak J Biol Sci. 2009 Sep 1;12(17):1217-21.
- Harrison RF and Cullen R. A comparative study of the behaviour of the neonate following various forms of maternal intrapartum analgesia and anaesthesia. Ir J Med Sci. 1986;155(1):12-18.
- Beppu K. Transmission of the anesthetic agents through the placenta in painless delivery and their effects on newborn infants. Keio J Med. 1968 Jun;17(2):81-107.
- Soyannwo OA. Self-administered Entonox (50% nitrous oxide in oxygen) in labour: report of the experience in Ibadan. Afr J Med Med Sci. 1985 Mar-Jun;14(1-2):95-8.
- Newton C, Fitz-Henry J, and Bogod D. The occupational exposure of midwives to nitrous oxide - a comparison between two labour suites. Int J Obstet Anesth. 1999 Jan;8(1):7-10.
Full Report
This executive summary is part of the following document: Likis FE, Andrews JA, Collins MR, Lewis, RM, Seroogy JJ, Starr SA, Walden RR, McPheeters ML. Nitrous Oxide for the Management of Labor Pain. Comparative Effectiveness Review No. 67. (Prepared by the Vanderbilt Evidence-based Practice Center under Contract No. 290-2007-10065-I.) AHRQ Publication No. 12-EHC071-EF. Rockville, MD: Agency for Healthcare Research and Quality. August 2012. www.effectivehealthcare.ahrq.gov/reports/final.cfm.
For More Copies
For more copies of Nitrous Oxide for the Management of Labor Pain: Comparative Effectiveness Review Executive Summary No. 67(AHRQ Pub. No. 12-EHC071-1), please call the AHRQ Publications Clearinghouse at 1–800–358–9295 or email firstname.lastname@example.com.

subset: commoncrawl


text:
David Shipley
Photo: © Elena Seibert
About the Author
David Shipley is the deputy editorial page editor and Op-Ed page editor of The New York Times. Previously, he was a senior presidential speechwriter in the Clinton administration. He lives in New York.
David Shipley and Will Schwalbe are available for select readings and lectures. To inquire about a possible appearance, please contact the Penguin Random House Speakers Bureau (www.prhspeakers.com).


text:
And you're aware the SERES training was intended for preparing our troops for what might happen to them if they fell into enemy hands, and those enemies refused to follow the Geneva Convention? It's very clear that the methods outlined in SERES are considered to be violations of the Convention.
You're also aware that being waterboarded by your own team in a controlled environment is a wee bit different from being waterboarded by the enemy, right?


text:
I've been getting into Common Lisp heavily lately. Working with Emacs Lisp has always been a great change of pace from daily work in C or Java. Things like map, with-*, and the delightful development environment are great, but the biggest reason is that it's a completely different mindset. Lisp doesn't make you bother with declarations, recompile cycles, or loading a separate debugger.
Common Lisp may not have the extremely portable library called Emacs, but it's a lot faster, and has features which make
My play project is a DVD database. Not like the pathetic ones you see on slashdot, which index the movies and may, if you're lucky, link to Amazon. No, I want a database that fully describes my DVD collection. It'll start with the release (the thing you buy at the store), progress down through the case (Monty Python's flying circus has a box with a bunch of keep cases), through the disc (or as I prefer to call it, the shiny thing), describe the main feature, the extras, the audio tracks available for each, etc. The initial use case is to be able to decide if I want to buy a new edition of something, knowing as much as possible about what I have. Right after that is to let my family know what I have so they don't duplicate them during the holidays.
It's just great to experiment and futz around interactively. For example, here's my proof-of-concept Amazon search:
(setf result (xmls:parse (net.aserve.client:do-http-request "http://xml.amazon.com/onca/xml3" :query `(("t" . ,*associate-id*) ("dev-t" . ,*developer-token*) ; ("AsinSearch" . "0439139597") ("KeywordSearch" . "Harry Potter") ("mode" . "books") ("type" . "lite") ("f" . "xml")))))
(assoc "Asin" (cdr (assoc "Details" (cddr result) :test #'equal)) :test #'equal)
This uses xmls to parse the XML and Portable AllegroServe to talk http. CL may not have the huge quantity of libraries that other languages have, but I'm still happy how easy it was to get together!


text:
Web Stories
Lecture scheduled on faith and American founding, May 1
Posted April 25, 2002; 05:46 p.m.
Michael Novak will discuss his new book, "On Two Wings: Humble Faith and Common Sense at the American Founding," at 4:30 p.m. Wednesday, May 1, in 104 Computer Science Building.
Novak is the George Frederick Jewett Scholar in Religion, Philosophy and Public Policy at the American Enterprise Institute, where he also is director of social and political studies. His research interests include religion, business, culture, politics, ethnicity and sports.
Novak is the author, co-author and editor of several books, including "On Cultivating Liberty: Reflections on Moral Ecology" (1999) and "The Hemisphere of Liberty: A Philosophy of the Americas" (1990). He is the former U.S. ambassador to the United Nations Human Rights Commission in Geneva (1981-82) and former adviser on ethnic affairs to the White House (1974-80).
The lecture is sponsored by the James Madison Program in American Ideals and Institutions through its Alpheus Mason Lectures in Political Thought and Constitutional Governance . This year's lecture series is made possible by the support of John Hansel, class of 1946.
Contact: Marilyn Marks (609) 258-3601


text:
Family: Anatidae, Ducks and Geese view all from this family
Description ADULT MALE Has mainly black underparts and white upperparts, except for black cap, lime green nape and pinkish flush on breast. In eclipse plumage, male is mainly a mixture of brown and black, although some white feathering is always visible on back. Bill is yellow, smaller, and broader-based in Atlantic ssp. dresseri than "Hudson Bay" ssp. sedentaria or Arctic ssp. borealis. Note: ssp. v-nigrum from Pacific has orange bill but occurs outside range of this book. ADULT FEMALE Brown with darker barring, plumage affording superb camouflage when bird is nesting. Bill is dark gray. JUVENILE Similar to adult female, but typically shows a pale stripe above eye.
Dimensions Length: 23-27" (58-69 cm)
Habitat Mainly coastal, nesting close to seashore and usually feeding in inshore waters. Favors estuaries and rocky shores, diving for invertebrates, particularly mussels and other mollusks. Some birds are resident while northern populations move south in winter.
Observation Tips Easy to see on northeast rocky shores.
Range Eastern Canada, Alaska, Southeast, Mid-Atlantic, Western Canada, New England
Voice Male utters a characteristic, and rather endearing, cooing ah-Whooo. While doing so, head is thrown back in a distinctive manner.
Discussion Bulky sea duck that dives frequently and for long periods. Distinctive even in silhouetteólarge, wedge-shaped bill follows slope of forehead. Highly gregarious for most of year. In summer, several females may band together, accompanied by "creche" of youngsters. In flight, male looks black and white, while female can look uniformly dark in poor light. Except during summer molt, sexes have strikingly dissimilar plumages. Three of the four North American subspecies occur in the region covered by this book.


text:
Day 2 in Vegas
Trip Start Jun 07, 2010
126Trip End Dec 18, 2010
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We then made our way to a gun store to fire some guns, I shot a G36 semi automatic and a Dirty Harry Smith & Wesson Model 29 revolver with .44 Magnum cartridge, what a gun to fire, the most powerful handgun in the world, and would blow your head clean off, you've got to ask yourself one question: Do I feel lucky? Well, do ya, punk?
Louise shot a semi automatic and a hand gun, she did very well with the powerful guns, hit the target every time.
We then went to las Vegas south side sign for some photos and went to some more hotels, watched to Bellagio fountains 3 more times as Louise is mad for them then made our way back to our hotel.


text:
Offline Data Entry - repost 2
This project was awarded to SidRasibti for $500 USD.Get free quotes for a project like this
Project Budget$250 - $750 USD
Total Bids4
Project Description
Dear Friends,
This is easy offline data entry work.
I have 250 pages i want someone to rewrite them, i will Provide you .JPEG (Image Files), Which You have to Convert In MS-word File by typing only if you use any software you will not be paid.
Skills required:
1- have knowledge in micro soft word.
2- reliable and skillful worker
3- typing speed at least 30 - 50 WPM
You are not allowed to use any software for converting image file to MS-Word. If found i will terminate you. Because when you use software's it changes the Ms-Word file codes which is not visible to me.
Mistake = 0.2 cent
Finally i want this work to be finished within 7 days max.,
Fresher & New freelancer Candidate can also bid on this project.
Thanks and happy bidding.
Awarded to:
Skills Required
Looking to make some money?
- Set your budget and the timeframe
- Outline your proposal
- Get paid for your work
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- Forbes
- The New York Times
- Time
- Wall Street Journal
- Times Online


text:
Canton, Illinois
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Highland Park's newly restored Rosewood Beach is opening on June 6, and the good news is tha...
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What's not allowed into Soldier Field during a Bears game?
Planning a trip to Chicago and want to see a Bears game while I'm there. What items are you ...


text:
USAID supports the restoration of Gorongosa National Park, by promoting a peaceful interaction between communities and animals. Thanks to USAID, the park's communities can now learn about conservation and farming, while accessing better health facilities.
Mozambican farmers are learning techniques that will improve crop productivity.
A new mother gazes at her healthy baby boy shortly after delivery at a "model maternity" ward. The USAID Model Maternities Initiative works on maternal and neonatal health, family planning and prevention of mother-to-child transmission of HIV/AIDS.
USAID protects the habitat of Lake Niassa, the most biodiverse freshwater lake on earth.
Mozambique has improved its customs policies to help exports cross borders more easily
USAID works with community groups to improve information about health and nutrition
About Mozambique
Following a long civil war, Mozambique has made the transition to peace, stability and sustained economic growth, providing an essential link between landlocked neighbors and the global marketplace.
Its ties to South Africa's industrial heartland underscore the fact that the country's economic, political and social progress is vital to the interests of the region. However, the high prevalence of HIV/AIDS, malaria and other diseases, as well as high infant mortality, have resulted in the distressingly low life expectancy of just 50 years.
USAID's programs in democracy, economic growth, health and education address these challenges and opportunities.
Related Links
Last updated: April 13, 2017


text:
Small Gains
Wind and solar power are ramping up quickly, but the world's demand for electricity is growing much faster.
Water Power
Decisions about future energy sources will need to factor in water consumption as well as greenhouse-gas emissions.
Follow the Flow
The trail of U.S. energy--what we use, and how we waste it
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- 1
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text:
In 1994, TAPS received its designation from the IRS as a charitable corporation, and has since maintained its good standing. TAPS' Federal Tax Identification number is 92-0152268.
For a list of our business credentials and regulatory compliance certificates, please view the documents in PDF format below.
TAPS is registered in all 50 states and in the District of Columbia. To view TAPS' state registration certificate, please check on-line with the appropriate jurisdiction's Attorney General's office, Secretary of State, Department of Consumer Protection, or other agency which oversees charities and charitable solicitations. Or contact TAPS directly.
Workplace Giving Programs note: TAPS solicits for various workplace giving campaigns including the Combined Federal Campaign (CFC) and the United Way.
The Tragedy Assistance Program for Survivors (TAPS) is a not-for-profit organization and is not part of, or endorsed by, the Department of Defense.
Financial documents for FY2012 and FY2011 are available upon request
TAPS is proud to be recognized as a four star charity by Charity Navigator. TAPS received a rating of Exceptional, meaning we exceed industry standards and outperform most charities in our Cause.
Tragedy Assistance Program for Survivors, Inc., Tax ID# 92-01522683033 Wilson Blvd. Suite 630, Arlington, VA 22201
202-588-8277 (Headquarters) 571-385-2524 (Fax) - © 2015 Copyright All Rights Reserved


text:
Words Found and Argued
Some time ago, I wrote this:
"The low barrier of entry to accessing and interpreting economic data has created unrealistic expectations of its accuracy and relevance."
I don't know if that was me writing down my own thoughts or someone else's, but I agree.
Incidentally, regarding the dust-up caused by the WSJ's style guide change allowing data to be used as a singular noun, I'd like to note that while I'm okay with the WSJ's change, I find their explanation to be lacking a simple point: it's not simply that usage has evolved away from the plural, it's that data has evolved from being a plural to being a mass noun. Given the fundamental changes brought about by the volume of data (Did you see what I did there? Volume? Mass noun.) we now produce, I'd argue that this is a case where the change in grammar perfectly mirrors the change in the concept it describes.