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Biomedical subjects

N Johnson

Publications and source records attributed to N Johnson.

At least 199 records · Page 11Linked to original sources
PubMed1993

The effect on fetal arteriolar oxygen saturation resulting from giving oxygen to the mother measured by pulse oximetry.

OBJECTIVE: To determine if pulse oximetry could detect any changes in fetal arteriolar oxygen saturation resulting from maternal administration of oxygen. DESIGN: A prospective study comparing study comparing the fetal pulse oximetry reading before and after giving 27% and 100% oxygen to the mother. The data were collected using an experimental pulse oximeter and a sensor specifically adapted to cope with the problems of fetal pulse oximetry. SETTING: Labour ward, St. Jame's University Hospital, Leeds University, UK. SUBJECTS: Twelve fetuses presenting by the vertex in normal uncomplicated labour. MAIN OUTCOME MEASURES: The change in fetal arteriolar oxygen saturation recorded by the pulse oximeter in response to oxygen administration to the mother. RESULTS: Twenty-seven percent oxygen increased the average fetal arteriolar oxygen saturation by 7.5%, the effect being reversed when the oxygen was withdrawn. One hundred percent oxygen increased fetal arteriolar oxygen saturation by 11% and when the oxygen was withdrawn oxygen saturation dropped by 10%. One hundred percent inspired maternal oxygen was more effective than 27%. The gradient of the fetal oxygen regression slope is steeper with 100% oxygen than 27% and it is steeper when oxygen is given compared to when it is withdrawn. This suggests that the fetus responds to the new placental oxygen gradient by accepting oxygen more rapidly than it gives it up. Using a quadratic regression model, it took 9 min for fetal oxygen saturation to reach its maximum value after giving the mother oxygen. CONCLUSION: This study confirms that a pulse oximeter is able to measure an increase in fetal arteriolar oxygen saturation when oxygen is administered to the mother.

Arterioles↗
PubMed1993

Relative contributions of cardiopulmonary and sinoaortic baroreflexes in causing sympathetic activation in the human skeletal muscle circulation during orthostatic stress.

The aim of this study was to reexamine the hypothesis that cardiopulmonary baroreflexes are more important than sinoaortic baroreflexes in causing vasoconstriction in the skeletal muscle circulation during orthostatic stress. We recorded muscle sympathetic nerve activity (MSNA) with microelectrodes in the peroneal nerve (and forearm blood flow with venous occlusion plethysmography) in normal subjects (innervated ventricles) and in heart transplant recipients (denervated ventricles) during graded lower body negative pressure (LBNP) performed alone and in combination with intravenous infusion of phenylephrine, which was titrated to eliminate the orthostatically induced fall in blood pressure and thus the unloading of both carotid and aortic baroreceptors. The principal new findings are as follows: (1) The increases in both MSNA and forearm vascular resistance during multiple levels of LBNP were not attenuated by heart transplantation, which causes ventricular but not sinoaortic deafferentation. (2) In heart transplant recipients, a small increase in MSNA during mild LBNP was dependent on a decrease in arterial pressure, but in normal subjects, a similar increase in MSNA occurred in the absence of any detectable decrease in the aortic pressure stimulus to the sinoaortic baroreceptors. (3) In normal subjects, the large increase in MSNA during a high level of LBNP was dependent on a decrease in arterial pressure and could be dissociated from the decrease in central venous pressure. Taken together, the findings strongly suggest that sinoaortic baroreflexes are much more important and ventricular baroreflexes are much less important than previously thought in causing reflex sympathetic activation and vasoconstriction in the human skeletal muscle circulation during orthostatic stress.

Female↗
PubMed1993

Fetal monitoring by pulse oximetry and CTG.

To see if a pulse oximeter can monitor the fetus during labour we recruited 100 Caucasian women in normal uncomplicated labour. Our primary objective was to compare the predictive value of fetal pulse oximetry and cardiotocography using neonatal condition and cord blood acidaemia or hypoxaemia at birth as outcome variables. The fetuses were monitored continuously with a pulse oximeter specifically adapted for fetal use. Five babies had an operative delivery because of an abnormal CTG. Two of these were born in good condition (Apgar score 9 at 1 minute in both cases). The other three babies were delivered in poor condition (Apgar scores of 6 & 9, 5 & 10 and 5 & 10 at 1 and 5 minutes respectively). The oxygen saturation reading only dropped significantly in babies born in poor condition and in one case the drop preempted the CTG changes. These data suggest that pulse oximetry can be adapted to monitor the fetus and has the potential to provide useful information during labour.

Apgar Score↗
PubMed1993

Views from Capitol Hill--11 congressional leaders paint varying reform scenarios. Interview by Marybeth Burke.

The following exclusive interviews with top congressional health care leaders were conducted by Washington-based reporter Marybeth Burke. In the interviews, Burke found that congressional health care leaders are optimistic yet cautious that comprehensive health care reform legislation will pass in 1993 under President Clinton. Some members of Congress believe that the election of a president committed to action on the issue drastically improves the outlook for reform. Others say that long-term controversy over reform will not resolve itself overnight. Lawmakers expect the issue to heat up quickly as soon as Clinton hands Congress a legislative reform package, but they are reluctant to predict quick enactment.

Competitive Medical Plans↗
PubMed1993

Feasibility of developing and selecting criteria for the assessment of clinical performance.

This study was undertaken to assess the feasibility of one method of initiating the setting of standards in United Kingdom general practice by the development and selection of criteria for clinical care. Three clinical topics were chosen. An 'academic phase' was used to develop precise criteria, which formed the basis of a draft questionnaire for each of the three topics. A 'consultation phase' followed in which the three questionnaires were sent to a randomly selected sample of general practitioners throughout the UK. Although 53% of the 62 general practitioners invited were willing to be involved in the academic phase only 13% were able to attend a meeting. Of the 262 general practitioners sent one of the questionnaires 63% responded. Using a strict definition of consensus one quarter of the criteria were identified by the respondents to the questionnaire as important or not important; using a less strict definition a further one quarter to one half of the criteria were identified. The study demonstrates that it is possible to develop and select criteria in this way. If this approach were to be developed for performance review, criteria would need to be selected, appropriate target levels of performance set, and suitable methods for their application identified.

Clinical Competence↗
PubMed1993

General practice careers: changing experience of men and women vocational trainees between 1974 and 1989.

The aim of this study was to consider the careers pursued by men and women general practitioner trainees following the completion of their training, and to assess changes since 1974. It was based on a postal questionnaire survey involving 995 doctors who had completed general practice vocational training in the Oxford region between 1974 and 1989. A total of 796 doctors replied to the questionnaire (498 men and 298 women, overall response rate 80%). The vast majority of ex-trainees were working in general practice at the time of the survey (men 87%, women 71%). Women were less likely to have become principals than men (75% versus 97%). Most women (71% of those completing training before 1988) reported at least one period of non-employment. While the duration of maternity leave dropped only slightly during the 15 years studied, the length of voluntary and involuntary unemployment experienced by women fell markedly. Men experienced little unemployment with no change in length of unemployment over time. Considerably fewer women than men (6% versus 13%) had become involved in teaching or training. The degree of difficulty in choosing and following a general practice career remained constant over time for women. In contrast there was a significant increase in the difficulties experienced by men. The proportion of men and women completing training in 1984-89 who found following a general practice career 'difficult or very difficult' was similar (10% of men, 13% of women). The possibility of improving these experiences, particularly by encouraging flexibility in the early years after completion of training, is discussed.

Adult↗
PubMed1992

Should we use prostaglandins, tents or progesterone antagonists for cervical ripening before first trimester abortion?

Sixty-four women requesting first trimester termination of pregnancy were recruited into a comparative cohort study comparing the cervical ripening properties of a mechanical dilator (Lamicel; n = 17), prostaglandin, antiprogesterone and placebo control (n = 15), gemeprost; n = 17) and mifepristone; n = 15). Compared to the placebo group, all 3 active agents dilated the cervix (p < 0.02) and they significantly reduced the force required to dilate it to 8 mm Hegar (p < 0.001). Although Lamicel insertion resulted in the largest pre-operative cervical dilatation all agents are effective. Therefore the cervical priming agent of choice should be the most convenient to use and the one with least side-effects. The oral antiprogesterone, Mifepristone, is the easiest to administer and has less side effects.

Abortion, Induced↗
PubMed1992

Human immunodeficiency virus infection among inner-city adolescent parturients undergoing routine voluntary screening, July 1987 to March 1991.

OBJECTIVE: The objective of our study was to describe the human immunodeficiency virus epidemic among pregnant adolescents undergoing follow-up in a large inner-city hospital. STUDY DESIGN: We conducted a case-control study comparing demographic and risk behaviors of seropositive and seronegative adolescents (aged 13 to 20) identified from a population undergoing routine voluntary antibody screening at Grady Memorial Hospital in Atlanta, Georgia, between July 1987 and March 1991. RESULTS: Of 10,794 pregnant adolescents screened, 51 (4.7/1000) were infected with human immunodeficiency virus. More than one fourth of case patients were < or = 17 years old. Significantly more case patients than controls reported a history of crack cocaine use (10 [19.6%] vs 23 [8.2%] p < 0.05). A majority (58.8%) of case patients reported no risk factors for infection, and the remainder (41.2%) were presumably infected by heterosexual contact. Thirty-nine controls (13.8%) had self-identified risk factors for infection. CONCLUSIONS: Pregnant adolescents in our center are at risk for human immunodeficiency virus infection and should be targeted for human immunodeficiency virus education and risk reduction counseling.

Adolescent↗
PubMed1992

Using decision analysis to calculate the optimum treatment for microinvasive cervical cancer.

Decision theory was used to calculate the optimum treatment of microscopic squamous cervical cancer using probabilities obtained from an exhaustive literature review and a range of plausible value estimates. This showed that if there is no vascular involvement, survival is maximised by conservative treatment if tumour invasion is less than 3 mm while treatment by radical surgery results in maximal survival rates if the tumour invasion is over 3 mm. Radical surgery also maximises survival for smaller lesions where lymph channel involvement is present, especially if a surgical mortality at the lower end of the reported range is assumed. Refinement of our analysis to include an assessment of patient values showed that these conclusions are still valid regardless of the patient's relative preference for death from surgery or death from cancer. However, the wish to preserve fertility sharply reduces the overall net benefit of surgery. Conservative treatment becomes the preferred option for all microinvasive lesions even for patients who are prepared to trade-off a small (e.g. 2%) risk of death in order to retain their fertility.

Adult↗
PubMed1992

Is transcutaneous electrical nerve stimulation of any value during cervical laser treatment?

OBJECTIVE: To assess the value of transcutaneous electrical nerve stimulation (TENS) during cervical laser therapy. DESIGN: Randomized three arm controlled clinical trial comparing (i) TENS, (ii) local anaesthetic and (iii) TENS plus local anaesthetic (direct infiltration of 2% lignocaine and 0.03 iu/ml octopressin). SETTING: Colposcopy Unit adapted to run randomized trials. SUBJECTS: 100 women with CIN and no previous experience of cervical surgery. MAIN OUTCOME MEASURE: Visual linear analogue pain scores. RESULTS: The median pain score associated with TENS was greater than the score associated with local anaesthesia (23% compared with 17%; P = 0.1). Combining TENS with local anaesthesia did not further reduce pain scores. CONCLUSION: Although there was considerable consumer satisfaction with TENS it provided no additional pain relieving effect in addition to direct infiltration of lignocaine and it is inferior to lignocaine alone. We are unable to advocate the use of TENS for laser treatment of the cervix.

Adult↗
PubMed1992

Do fetal pulse oximetry readings at delivery correlate with cord blood oxygenation and acidaemia?

OBJECTIVE: To assess the accuracy of a pulse oximeter in the fetus. DESIGN: A prospective descriptive study, comparing oxygenation and acidaemia of cord blood with oxygen saturation in the arteries of the fetal scalp measured by a pulse oximeter just before delivery. The data were collected using an experimental pulse oximeter and a sensor specifically adapted to cope with the problems of fetal pulse oximetry. SETTING: The labour ward in a teaching hospital. SUBJECTS: Thirty seven Caucasian fetuses presenting by the vertex in normal uncomplicated labour. MAIN OUTCOME MEASURE: Fetal pulse oximetry reading shortly before birth, umbilical cord oxygenation and pH, and Apgar scores. RESULTS: Data of sufficient quality were obtained from 28 fetuses. There was a highly significant correlation between pulse oximetry reading and umbilical vein oxygen saturation r = 0.59, P = < 0.001). There was also a significant correlation between the pulse oximeter reading and cord blood pH (vein: r = 0.57, P = 0.002, artery: r = 0.63, P = 0.001). Apgar scores were not related to the oximetry results. CONCLUSION: Pulse oximetry readings reflect fetal oxygenation at birth.

Apgar Score↗
PubMed1991

The effect of squatting on pelvic dimensions.

Lateral X-ray pelvimetry was performed on 63 women in the sitting and squatting positions on the 5th or 6th post-natal day to assess whether squatting has any effect on pelvic dimensions. Four assessors measured the inlet and outlet pelvic dimensions from 25 cases with good radiographic views in order to minimise observer bias. There was no statistically significant change in pelvic dimensions with squatting. Some possible explanations are discussed.

Female↗
PubMed1991

Use of computerised general practice data for population surveillance: comparative study of influenza data.

OBJECTIVE: To assess the potential for using routine computerised general practice data for surveillance of illness. DESIGN: Comparison of the incidence of influenza during the 1989 epidemic derived from a computerised database with that derived from the Royal College of General Practitioners's weekly returns service--a well established predominantly manual surveillance system. SETTING: 433 general practices throughout the United Kingdom that used a commercial computer system linked to a central databank. MAIN OUTCOME MEASURE: Incidence of influenza. RESULTS: The slope of the influenza epidemic curve was essentially the same whether derived from the routine computerised data or royal college's weekly returns service data, and the computerised data were geographically consistent. Throughout the study period, however, the computer derived incidence was between one third and one quarter of that derived from the royal college's system (which is served by practitioners trained in surveillance methods). The peak weekly rates were 164 cases per 100,000 for the computerised system and 583 cases per 100,000 for the royal college's surveillance system. CONCLUSIONS: The apparent underreporting in the routine computerised data probably reflects lack of motivation and experience in disease surveillance and haphazard computer entry (particularly of consultations that took place outside of the surgery and consultations that did not result in a prescription), along with overestimation of the population under surveillance. Nevertheless, routine computerised surveillance allows rapid data collection from a large number of practices over a wide geographical area and would greatly augment existing methods.

Computer Systems↗
PubMed1991

Excretion of mutagens following chemotherapy.

The mutagenic activity of urine was evaluated in children receiving single and multiple agent chemotherapy to determine the duration of carcinogenic risk to health care personnel and family contacts. Urine samples from 21 children were evaluated before and daily for 5 days after chemotherapy administration. Mutagenic activity, a sensitive though not specific indicator of carcinogenic risk, was assayed using mutant strains of Salmonella typhimurium (the "Ames test"). Validity of the assay was confirmed by demonstrating mutagenic activity in urine samples from 17 adult cigarette smokers but not from 21 adult nonsmokers (24/24 versus 0/37, p less than 0.001). None of the 21 children tested demonstrated mutagenic activity before chemotherapy administration. Following single agent dactinomycin, cyclophosphamide, daunorubicin, doxorubicin, methotrexate, or vincristine, mutagenic activity was demonstrated for 2 days (5/5 at 1 and 2 days and 0/5 at 3 days). Following multiple agent chemotherapy using two or three of the latter drugs on a single day, mutagenic activity was demonstrated for 4 or 5 days (16/16 at 1, 2, 3, and 4 days, and 4/16 at 5 days). Based on these observations with urine, and presumably other body fluids, precautions are recommended for 2 days following single agent and at least 5 days following multiple agent chemotherapy.

Adult↗
PubMed1991

Fetal monitoring with pulse oximetry.

Continuous fetal monitoring was achieved with a fetal scalp pulse oximetry sensor in 86 labours. The average recorded fetal oxygen saturation in early labour (cervical dilatation less than 5 cm) was 68% (SD 13%). At the end of labour (cervical dilatation greater than or equal to 9 cm) the recorded mean oxygen saturation was 58% (SD 17%). The largest range of readings during a single labour was 81%-11% but this drop was associated with cord compression. The average SD during 1 h of normal labour was 10%. A second group of 40 fetuses was monitored during induction of labour before and after elective amniotomy. Oxygen saturation did not appear to change after amniotomy (mean change -0.4%, SD 1.2%) and there was no difference between mean antenatal or early intrapartum readings. We excluded the amniochorionic membranes as a possible source of data corruption by measuring their in vitro absorption spectra and confirming that they do not preferentially absorb light of either 660 or 940 nm wavelength. Non-invasive pulse oximetry can be used to monitor the fetus before and during labour.

Amnion↗