Improved survival following ward-based non-invasive pressure support for severe hypoxia in a cohort of frail patients with COVID-19: retrospective analysis from a UK teaching hospital

Since the outbreak of COVID-19 in China in December 2019, a pandemic has rapidly developed on a scale that has overwhelmed health services in a number of countries. COVID-19 has the potential to lead to severe hypoxia; this is usually the cause of death if it occurs. In a substantial number of patients, adequate arterial oxygenation cannot be achieved with supplementary oxygen therapy alone. To date, there has been no clear guideline endorsement of ward-based non-invasive pressure support (NIPS) for severely hypoxic patients who are deemed unlikely to benefit from invasive ventilation. We established a ward-based NIPS service for COVID-19 PCR-positive patients, with severe hypoxia, and in whom escalation to critical care for invasive ventilation was not deemed appropriate. A retrospective analysis of survival in these patients was undertaken. Twenty-eight patients were included. Ward-based NIPS for severe hypoxia was associated with a 50% survival in this cohort. This compares favourably with Intensive Care National Audit and Research Centre survival data following invasive ventilation in a less frail, less comorbid and younger population. These results suggest that ward-based NIPS should be considered as a treatment option in an integrated escalation strategy in all units managing respiratory failure secondary to COVID-19.

Continuous positive airway pressure effect on visual acuity in patients with type 2 diabetes and obstructive sleep apnoea: a multicentre randomised controlled trial

We sought to establish whether continuous positive airway pressure (CPAP) for obstructive sleep apnoea (OSA) in people with type 2 diabetes and diabetic macular oedema (DMO) improved visual acuity.We randomly assigned 131 eligible patients aged 30-85 years from 23 UK centres with significant DMO causing visual impairment (LogMAR letters identified ≥39 and ≤78, score 0.92-0.14) plus severe OSA on screening to either usual ophthalmology care (n=67) or usual ophthalmology care plus CPAP (n=64) for 12 months.Mean age of participants was 64 years, 73% male, mean body mass index 35.0 kg·m- 2 Mean 4% oxygen desaturation index was 36 events·h-1 There was no significant difference in the visual acuity at 12 months between the CPAP group and the control group (mean LogMAR 0.33 (95% CI 0.29-0.37) versus 0.31 (95% CI 0.27-0.35); p=0.39), and no significant correlation between change in LogMAR and average CPAP use. The median±sd (range) daily CPAP use was 3.33±2.25 (0-7.93) h at 3 months, 3.19±2.54 (0-8.07) h at 6 months and 3.21±2.70 (0-7.98) h at 12 months.CPAP therapy for OSA did not improve visual acuity in people with type 2 diabetes and DMO compared with usual care alone over 12 months.

Obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is increasing in prevalence due to rising obesity. While OSA is a disorder primarily of the upper airway during sleep, its pathophysiological impact on other body systems is increasingly recognised. There has been interest in the prevalence of OSA in different ophthalmic conditions and possible causation has been postulated. As OSA is common, it can be expected that people with co-existent OSA will be found in any ophthalmic disease population studied. To determine with confidence the significance of finding patients with OSA in a particular cohort requires a well matched control group, ideally matched for age, obesity, gender and co-morbidities. Only if one can say with certainty that the prevalence of OSA is higher in a group with a particular co-existent ophthalmic disease can we begin to speculate about possible mechanisms for the overlap in these conditions. Possible mechanisms for how OSA might affect the eye are discussed in this review. The current literature is reviewed with respect to diabetic retinopathy, glaucoma, floppy eyelid syndrome, non-arteritic ischaemic optic neuropathy, keratoconus and AMD. Associations with OSA have been found, but robust prospective studies using multi-channel sleep studies to diagnose OSA are lacking. Gaps remain in the evidence and in our knowledge. It is hoped that this review will highlight the need for ophthalmologists to consider OSA in their patients. It also makes recommendations for future research, especially to consider whether therapies for OSA can also be effective for ophthalmic disorders.

Sleepiness and Sleep-related Breathing Disorders in Myotonic Dystrophy and Responses to Treatment: A Prospective Cohort Study

OBJECTIVE

We conducted prospective assessments in people with myotonic dystrophy type 1 (DM1) with daytime sleepiness, provided targeted therapies and assessed response.

METHODS

Patients had overnight sleep assessments. Treatment with continuous positive airway pressure (CPAP) for OSA, non-invasive ventilation (NIV) for respiratory failure, modafinil for excessive daytime sleepiness were commenced.

RESULTS

120 people were studied: mean age 46.9 years (SD 13.2, range 18-74), body mass index 27.9 kg/m2 (7.2, 16-53), Epworth Sleepiness Score (ESS) 13.1 (4.7, 2-24). Twenty one people (18% of group) had OSA: mean age 49.6, BMI 31.1, ESS 14.3, ODI 22, pO2 11.3, pCO2 5.4. All were offered CPAP; seven continued with benefit but 14 had intolerance or no benefit. Thirty-three people (27%) had respiratory failure and abnormal sleep study: mean age 51.5, BMI 31.3, ESS 13.9, ODI 22.9, pO2 8.7, pCO2 6.8. All were offered NIV; 12 continued with benefit but 18 had intolerance or no benefit, 1 died and 2 declined commencement. Thirty-six people (30%) had predominantly sleepiness: mean age 44.8, BMI 24.6, ESS 14.1, ODI 9.2, pO2 11.7, pCO2 5.4. All were offered modafinil; 12 continued this with benefit but 10 had intolerance or no benefit, one was unkeen to start, 11 did not attend further clinic and two had other sleep disorders. Comparing means of treatment responders to non-responders showed no significant difference in any variable, except ESS: 15.9 vs.11.9 respectively, p < 0.0001.

CONCLUSIONS

Causes of sleepiness are variable in DM1, but include obstructive sleep apnoea, respiratory failure and sleepiness with a normal sleep study; 29% of this studied cohort benefited from targeted sleep therapies.

A 4-week wait 'fast-track' sleep service is effective at establishing vocational drivers on continuous positive airway pressure

We sought to establish whether an expedited or 'fast-track' NHS service to diagnose obstructive sleep apnoea (OSA) and establish vocational drivers on continuous positive airway pressure (CPAP) within 4 weeks of referral was possible. This model is recommended by the OSA Partnership Group. In total, 55 vocational drivers were referred to two sleep services. Assessment showed 73% had moderate or severe OSA on sleep study. Of those commenced on CPAP, review was a mean of 15 days after initiation (range 3-62 days). Median time from referral (or first clinic visit) to review on CPAP was 32 days, showing a 'fast-track' pathway is deliverable.

Is obstructive sleep apnea a risk factor for diabetes?

Obstructive sleep apnea (OSA) and type 2 diabetes are both closely related to obesity and their prevalence is increasing due to the rising average body weight in Western countries. The findings of epidemiological studies have implicated that OSA increases the risk for cardiovascular disease, and metabolic disturbances, such as insulin resistance, may link OSA to vascular morbidity. A number of observational clinical studies have evaluated the relationship between OSA and insulin resistance, suggesting an independent association. However, the confounding effect of obesity complicates the establishment of a causal relationship between OSA and insulin resistance. Potential mechanisms that may underpin this relationship were evaluated in animal and human experimental studies and include intermittent hypoxia, arousals from sleep with concomitant sympathetic activation and sleep fragmentation. Currently only three randomized controlled trials investigating the effects of OSA on insulin resistance have been published. In these trials OSA patients were randomly assigned to treatment with continuous positive airway pressure (CPAP) or subtherapeutic CPAP and treatment effects on various measures of insulin resistance were examined. In two of these trials there was no effect of CPAP on glucose metabolism and in one trial a small beneficial effect of CPAP was observed. Further carefully conducted clinical studies and randomized controlled interventional CPAP trials are needed to determine the extent to which OSA is a risk factor for diabetes and its effect on glucose metabolism.

The prevalence of retinopathy in men with Type 2 diabetes and obstructive sleep apnoea

AIMS

To clarify the relationship between obstructive sleep apnoea (OSA) and diabetic retinopathy.

RESEARCH DESIGN AND METHODS

A cohort of 240 men from primary and secondary care previously participated in a study on the prevalence of OSA in Type 2 diabetes and provided anthropometric information, details of their diabetes, had glycated haemoglobin (HbA1c) measured and overnight oximetry performed. They were re-contacted for permission to review their routine screening clinical retinal photographs, which were then scored by a trained grader, providing detailed retinopathy, maculopathy and photocoagulation scores.

RESULTS

One hundred and eighteen men both consented and had retinal photographs available to review. Of these, 24% had OSA, with mean+/-sd 4% oxygen saturation (SaO2) dips/h of 20.9+/-16.6 vs. 2.8+/-2.1 in the non-OSA group. As expected, the OSA group had a significantly higher mean body mass index of 31.9+/-5.2 vs. 28.5+/-5.1 kg/m2 and neck size 44.5+/-3.6 vs. 41.9+/-2.5 cm, but the two groups did not differ significantly in age, diabetes duration, diabetes treatment, HbA1c, smoking history or proportion with known hypertension. Retinopathy and maculopathy scores were significantly worse in the OSA group (P<0.0001). Multiple regression analysis showed only OSA (R2=0.19, P<0.0001) and HbA1c (R2=0.04, P=0.03) to be significant independent predictors of retinopathy. OSA was the only independent significant predictor of the total microaneurysm score (R2=0.21, P=0.004), a detailed retinopathy subclassification. OSA was the only independent significant predictor of maculopathy (R2=0.3, P<0.001).

CONCLUSION

In men with Type 2 diabetes, there is a strong association between retinopathy and OSA, independent of conventional retinopathy risk factors.

Effect of CPAP on insulin resistance and HbA1c in men with obstructive sleep apnoea and type 2 diabetes

BACKGROUND

The effects of continuous positive airway pressure (CPAP) for obstructive sleep apnoea (OSA) on insulin resistance are not clear. Trials have found conflicting results and no appropriate control groups have been used.

METHODS

Forty-two men with known type 2 diabetes and newly diagnosed OSA (>10 dips/h in oxygen saturation of >4%) were randomised to receive therapeutic (n = 20) or placebo CPAP (n = 22) for 3 months. Baseline tests were performed and repeated after 3 months. The study was double blind.

RESULTS

Results are expressed as mean (SD). CPAP improved the Epworth sleepiness score significantly more in the therapeutic group than in the placebo group (-6.6 (4.5) vs -2.6 (4.9), p = 0.01). The maintenance of wakefulness test improved significantly in the therapeutic group but not in the placebo group (+10.6 (13.9) vs -4.7 (11.8) min, p = 0.001). Glycaemic control and insulin resistance did not significantly change in either the therapeutic or placebo groups: HbA1c (-0.02 (1.5) vs +0.1 (0.7), p = 0.7, 95% CI -0.6% to +0.9%), euglycaemic clamp (M/I: +1.7 (14.1) vs -5.7 (14.8), p = 0.2, 95% CI -1.8 to +0.3 l/kg/min(1000)), HOMA-%S (-1.5 (2.3) vs -1.1 (1.8), p = 0.2, 95% CI -0.3% to +0.08%) and adiponectin (-1.1 (1.2) vs -1.1 (1.3), p = 0.2, 95% CI -0.7 to +0.6 microg/ml). Body mass index, bioimpedance and anthropometric measurements were unchanged. Hours of CPAP use per night were 3.6 (2.8) in the treatment group and 3.3 (3.0) in the placebo group (p = 0.8). There was no correlation between CPAP use and the measures of glycaemic control or insulin resistance.

CONCLUSION

Therapeutic CPAP does not significantly improve measures of glycaemic control or insulin resistance in men with type 2 diabetes and OSA.

Prevalence of obstructive sleep apnoea in men with type 2 diabetes

BACKGROUND

A study was undertaken to establish the prevalence of obstructive sleep apnoea (OSA) in men with type 2 diabetes.

METHODS

Men with type 2 diabetes from local hospital and selected primary care practitioner databases received questionnaires about snoring, apnoeas, and daytime sleepiness based on the Berlin questionnaire. Selected respondents had overnight oximetry to establish whether they had OSA. Comparisons of oximetry were made with those from a previous general population study. HbA1c results were collected.

RESULTS

1682 men were sent questionnaires, 56% of whom replied. 57% scored as "high" and 39% as "low" risk for OSA; 4% were already known to have OSA. Oximetry was performed in 240 respondents from both risk groups: 31% of the "high" and 13% of the "low" risk group had significant OSA (more than 10 >4% Sao(2) dips/hour or Sao(2) tracing consistent with OSA). These results were verified by detailed sleep studies. Extrapolation of the oximetry data to the questionnaire respondent population suggests that 23% had OSA. Comparison of the oximetry results with men from a previous general population study (using only more than 10 >4% Sao(2) dips/hour to define OSA) showed the prevalence of OSA is significantly higher in this diabetes population (17% v 6%, p<0.001). Multiple linear regression revealed BMI and diabetes as significant independent predictors of OSA. Following correction for BMI (which explained 13% of the variance in OSA), diabetes explained a further 8% of the variance (p<0.001). There was a low correlation between OSA severity and HbA1c in the subgroup recruited from the hospital database (r = 0.2, p = 0.006) which remained significant after allowing for obesity (p = 0.03).

CONCLUSIONS

OSA is highly prevalent in men with type 2 diabetes; most are undiagnosed. Diabetes itself may be a significant independent contributor to the risk of OSA.

Needle-track metastases and prophylactic radiotherapy for mesothelioma

BACKGROUND

Mesothelioma invades the tracts made by chest instrumentation. Prophylactic radiotherapy is effective at preventing malignant seeding at these sites.

METHODS

We assessed the use and effectiveness of radiotherapy at our centre in 39 of the 40 patients identified with mesothelioma between January 2000 and September 2003.

RESULTS

Thirty-seven (95%) patients received radiotherapy to their chest instrumentation site between 6 and 42 days (median 26 days) following the diagnosis of mesothelioma. The radiotherapy field size varied, from 4 cm square to 14 x 10.5 cm. The radiotherapy was given as 21 Gy in 3 fractions over 1 week. In 3 patients (8%), there was already tumour invasion of the skin at the time of radiotherapy. In 2 other patients (5%), there was tumour recurrence following radiotherapy; in both this was at the edge of the previous radiotherapy fields. Further treatment was administered to an adjacent field in both. One patient with an indwelling pleural catheter developed tumour growth at the catheter insertion site. This was treated successfully with radiotherapy, with no catheter damage.

CONCLUSIONS

Prompt radiotherapy referral and radiotherapy field selection is important to maximise the effect of radiotherapy given to prevent chest wall tumour growth. There was no tumour growth in areas that were treated with radiotherapy. Further chest interventions outside the radiotherapy field should be followed with further radiotherapy.

Management of Malignant Pleural Mesothelioma

Malignant mesothelioma is increasing in incidence globally and has no known cure. Its unique clinical feature of local infiltration along tissue planes makes it a difficult neoplasm to manage. There have been few randomized controlled trials regarding treatment options, although these have increased in recent years, and results are eagerly awaited. This article summarizes important advances in the management of mesothelioma, especially diagnostic and therapeutic aspects.

Comparison of three ways to determine and deliver pressure during nasal CPAP therapy for obstructive sleep apnoea

BACKGROUND

The simplest method of initiating and maintaining therapeutic continuous positive airways pressure (CPAP) therapy for obstructive sleep apnoea (OSA) has not been established.

METHODS

Ninety eight subjects with OSA requiring CPAP treatment (more than 10 dips in oxygen desaturation of >4% per hour of sleep study and Epworth Sleepiness Score (ESS) >9) were randomised prospectively to three different methods of CPAP delivery for 6 months: (1) autotitration pressure throughout; (2) autotitration pressure for 1 week followed by fixed pressure (95th centile) thereafter; and (3) fixed pressure determined by algorithm (based on neck size and dip rate). Patients and investigators were blind to group allocation. One week after initiation the patients were routinely reviewed by sleep nurses. Study assessments took place before starting CPAP treatment and 1 and 6 months after to assess ESS, maintenance of wakefulness test, 24 hour blood pressure, general health (SF-36), and sleep apnoea related quality of life. CPAP internal monitoring data were also collected.

RESULTS

There were no significant differences in any of the outcome measures or CPAP monitoring data between the three groups. The 95th centile CPAP pressures delivered in the 6 month and 1 week autotitration groups were higher than in the algorithm group, but the median pressures were lowest in the 6 month autotitration group.

CONCLUSIONS

The method of determining CPAP pressure for treatment of moderate to severe OSA makes no significant difference to clinical outcome measures. The autotitration CPAP machine used has no advantage in this setting over simpler methods of pressure determination.

Pleurodesis for malignant pleural effusions: current controversies and variations in practices

PURPOSE OF REVIEW

Malignant pleural effusions are common, and pleurodesis remains the best method to control re-accumulation of the pleural fluid. There are few randomized controlled trials studying the optimal management of malignant pleural effusions. A recent international survey of pleurodesis practice has highlighted variations in how pleurodesis is performed worldwide. Future research should target these areas of variation to determine the best practice protocols.

RECENT FINDINGS

The selection of pleurodesing agents remains controversial. Talc is more effective, but is associated with more adverse effects. Talc pleurodesis is followed by systemic and pulmonary inflammation. This is probably related to systemic embolization of talc following its intrapleural administration, though there are other potential causes that may also play a role.

SUMMARY

The practice of pleurodesis varies considerably among individual pulmonologists and among different countries, in most technical aspects. This review serves to highlight some of these variations in practice, as well as reviewing the current literature on pleurodesis practice.

Determination of spinosad and its metabolites in food and environmental matrices. 3. Immunoassay methods

Spinosad is an insect control agent that is derived from a naturally occurring soil bacterium and is effective on several classes of insects, especially Lepidopteran larvae. Spinosad is registered in many countries for use on a variety of crops, including cotton, corn, soybeans, fruits, and vegetables. Residue methods utilizing a magnetic particle-based immunoassay (IA) test kit have been developed and validated for determining spinosad in environmental and food matrices. These methods involve an extraction of the residues from the matrices with appropriate solvents. For some matrices, the sample extracts can be diluted and measured directly by IA without any cleanup. For other matrices, sample extracts are purified using liquid-liquid partitioning and/or solid phase extraction prior to measurement by IA. The methods determine the total residue of spinosad, which includes the active ingredients (spinosyns A and D) and several minor metabolites, including spinosyn B, spinosyn K, and N-demethylspinosyn D. The methods have validated limits of quantitation of 0.0001 microgram/mL in water, 0.05 microgram/g in sediment, and 0.010 microgram/g in crops, crop processed commodities, and animal tissues. This paper briefly summarizes the residue methodology and method validation data for spinosad in 34 food, feed, and environmental matrices.

Determination of spinosad and its metabolites in food and environmental matrices. 1. High-performance liquid chromatography with ultraviolet detection

Spinosad is an insect control agent that is derived from a naturally occurring soil bacterium and is effective on several classes of insects, especially Lepidoptera larvae. Spinosad is registered in many countries for use on a variety of crops, including cotton, corn, soybeans, fruits, and vegetables. Residue methods utilizing high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection have been described for determining spinosad and its metabolites in environmental and food matrices. These residue methods typically involve an extraction with organic solvents, followed by purification using liquid-liquid partitioning and/or solid phase extraction prior to measurement by HPLC-UV. The residue methods determine the active ingredients (spinosyns A and D) and up to three minor metabolites (spinosyn B, spinosyn K, and N-demethylspinosyn D). The methods have validated limits of quantitation ranging from 0.010 to 0.040 microgram/g. This paper briefly reviews the residue methodology for spinosad and metabolites in food and environmental matrices and provides a summary of method validation results for 61 different sample types, including newly published results for 37 additional crop matrices and processed commodities.

Determination of ethalfluralin in canola seed, meal, and refined oil by capillary gas chromatography with mass selective detection

Ethalfluralin is a herbicide that is effective for weed control on a wide variety of crops, including canola. A method is described for the determination of ethalfluralin residues in canola seed, meal, and refined oil. Residues are extracted from canola sample matrixes with acetonitrile. An aliquot of the extract is diluted with water and purified by C(18) solid-phase extraction prior to analysis by capillary gas chromatography with mass selective detection. For all three sample matrixes, the method has a validated limit of quantitation of 0.02 microg/g and a limit of detection of 0.006 microg/g. Recoveries averaged 96 +/- 7% for canola seed, 87 +/- 6% for canola meal, and 89 +/- 5% for refined oil. In a magnitude-of-residue study, canola seed from field plots that had been treated with ethalfluralin at one to three times the maximum label rate for weed control were found to contain no detectable residue of the herbicide.

Residues of spinosad in meat, milk, and eggs

Spinosad is an insect control agent that is derived from a naturally occurring soil bacterium and has a high level of activity against insects that infest a variety of crops. Dairy and poultry feeding studies were conducted to determine the magnitude of spinosad residues in animal products that would result from the consumption of typical feed commodities containing residues of spinosad. Dairy cows were dosed for 28 days with spinosad at rates equivalent to 0, 1, 3, and 10 microg/g in the diet. Chicken hens were dosed for 42 days with spinosad at rates equivalent to 0, 0.1, 0.3, 1, and 5 microg/g in the diet. Milk, eggs, and tissue samples were analyzed by high-performance liquid chromatography and/or immunoassay methods. Spinosad residues occurred in all of the sample types but were lowest in eggs, skim milk, and lean meat and were highest in the fat.

Determination of spinosad and its metabolites in citrus crops and orange processed commodities by HPLC with UV detection

Spinosad is an insect control agent that is derived from a naturally occurring organism and is effective on a wide variety of crops, including citrus crops. A method is described for the determination of spinosad and its metabolites in citrus crops and orange processed commodities. The method determines residues of the active ingredients (spinosyns A and D) and three minor metabolites (spinosyn B, spinosyn K, and N-demethylspinosyn D). For dried orange pulp and orange oil, the method has a limit of quantitation (LOQ) of 0.02 microg/g and a limit of detection (LOD) of 0.006 microg/g. For all other sample matrices (whole fruit, edible fruit, juice, and peel), the method has an LOQ of 0.01 microg/g and an LOD of 0.003 microg/g. The analytes are extracted from the various sample types using appropriate solvents, and the extracts are purified by liquid-liquid partitioning and/or solid-phase extraction. All five analytes are determined simultaneously in the purified extracts by reversed-phase high-performance liquid chromatography with ultraviolet detection at 250 nm.

Effects of diaspirin crosslinked hemoglobin infusion in treadmill-exercised swine

The hemodynamic and metabolic effects of diaspirin crosslinked hemoglobin (DCLHb) were investigated using graded treadmill exercise in swine (n = 5/group). Swine received DCLHb (10% solution, 5 ml/kg) or oncotically-matched human serum albumin (HSA, 5ml/kg). Baseline metabolic and hemodynamic data were similar. In both groups exercise increased hemodynamic parameters. Exercise increased heart rate (HR) from 139 +/- 12 to 293 +/- 28 bpm with DCLHb and from 136 +/- 13 to 314 +/- 13 bpm with HSA. Exercise increased cardiac output (CO) from 5.7 +/- 0.75 to 15.6 +/- 2.01/min in the DCLHb group and from 5.3 +/- 0.48 to 15.7 +/- 0.881/min in the HSA group. However, CO returned to baseline faster with DCLHb upon stopping exercise. The DCLHb-treated group demonstrated a significantly higher oxygen extraction during exercise (12.04 +/- 0.38 vs 9.48 +/- 0.99 ml O2/100 ml blood) and a lower oxygen delivery throughout recovery (74.6 +/- 6.6 vs 102.2 +/- 7.21 O2/min), indicating enhanced oxygen delivery during exercise in the treatment group. DCLHb infusion did not impair metabolic or hemodynamic functions. These data indicate that DCLHb may increase oxygen delivery to working tissue more efficiently than HSA during treadmill exercise in swine.

Nitric oxide modulation of retinal, choroidal, and anterior uveal blood flow in newborn piglets

The purpose of the present study was to investigate the role of nitric oxide (NO) in modulating the resting vascular tone of the choroidal and anterior uveal circulations and the autoregulatory gain of the retina. Blood flow (ml/min/100 gm dry weight) to tissues was determined in 23 anesthetized piglets (3-4 kg) using radiolabelled microspheres. Ocular Perfusion Pressure (OPP) was defined as mean arterial pressure minus intraocular pressure (IOP) which was manipulated hydrostatically by cannulation of the anterior eye chamber. The OPP was decreased during intravenous infusion (30 mg/kg/hr) of either the NO-synthase inhibitor L-NAME or the inactive enantiomer D-NAME. Blood flows were determined at OPP of 60, 50, 40, 30, and 20 mmHg following initial ocular blood flow measurements. Mean initial choroidal and anterior uveal blood flows with L-NAME showed a 47+/-12% and a 43+/-6% reduction (p <.001), respectively. Mean choroidal blood flows were significantly reduced (p<.01) in the L-NAME treated animals at an OPP of 60 and 50 when compared to D-NAME. Uveal blood flows were linearly correlated with OPP in the L-NAME and D-NAME treated groups. Uveal blood flow was greater following exogenous administration of L-arginine (180 mg/kg). Mean initial retinal blood flow did not differ significantly in either group. Retinal blood flow with L-NAME was reduced at OPP of 60 mmHg and below compared to D-NAME (p<.05). The degree of compensation in the autoregulatory gain of the retinal vasculature was reduced in the presence of L-NAME at an OPP of 50 mmHg and below compared to D-NAME. These data support the hypothesis that NO may be a primary mediator in maintaining resting vascular tone to the choroid and anterior uvea in vivo and that NO blockade reduces the degree of compensation in the autoregulatory gain of the retinal vasculature within a specific range of ocular perfusion pressures.

Attitudes of African American adults toward treatment in cases of rape

The attitudes of 155 African American adults toward the need for treatment in cases of rape were assessed. The relationship of these attitudes to sex, age, income, educational level, knowledge of the effects of rape, the influence of rape circumstances on attitudes, and expectations regarding interactions with treatment facilities and agencies were assessed. The results indicated that the ability to recognize rape in a variety of situations, perception of victim responsibility for the rape, and a knowledge of the short term reactions associated with rape had the greatest impact on respondents' attitudes toward seeking treatment. Participants generally endorsed the need for counselling following a rape and expressed positive attitudes regarding treatment outcomes.

Gas chromatographic determination of residue levels of the herbicides trifluralin, benefin, ethalfluralin, and isopropalin in soil with confirmation by mass selective detection

A method is presented for the simultaneous or individual determination of the dinitroaniline herbicides trifluralin, benefin, ethalfluralin, and isopropalin in soil. The herbicides are extracted with acetonitrile-water (99 + 1), and the extracts are purified with small, disposable Florisil cartridges prior to analysis by gas chromatography using an electron capture detector or a mass selective detector. When electron capture detection is used as the primary detection system, confirmation with selective detection can be obtained using gas chromatography-mass spectrometry with a mass selective detector and a capillary column operated in the split mode. The limit of detection is 0.01 ppm, and recoveries averaged 95-112% for the 4 herbicides in several different soil types fortified at levels of 0.01-0.33 ppm.

Residue level determination of the aquatic herbicide fluridone and a potential photoproduct (N-methylformamide) in water

Methods are presented for the determination of the aquatic herbicide fluridone and N-methylformamide (NMF), a potential photoproduct of fluridone which has thus far been observed only in a laboratory aqueous photolysis study. Water samples are passed through a Sep-Pak C18 cartridge to extract fluridone while NMF passes unretained through the cartridge with the water. Fluridone is eluted from the cartridge with methanol, which is then concentrated for analysis by liquid chromatography with UV detection at 313 nm. The water eluate containing NMF is concentrated for analysis by rotary vacuum evaporation at 40-46 degrees C. Methanol is added to help evaporate the water, and glycerol is added as a keeper solvent to retain NMF during the evaporation. The residual NMF is dissolved in methanol for analysis by gas chromatography with a Hall electrolytic conductivity detector operated in the nitrogen mode. The assay limits of detection are 1 and 2 ppb for fluridone and NMF, respectively. Recoveries averaged 98% for fluridone at 1-400 ppb and 87% for NMF at 2-50 ppb.

Liquid chromatographic determination of fluridone aquatic herbicide and its metabolite in fish and crayfish

A residue method is described for determination of the aquatic herbicide fluridone (1-methyl-3-phenyl-5-[3-(trifluoromethyl)phenyl]-4(1H)-pyridinone) and its metabolite (1-methyl-3-(4-hydroxyphenyl)-5-[3-(trifluoromethyl) phenyl]-4(1H)-pyridinone) in fish and crayfish tissues. Both compounds are extracted from tissues with methanol, and the extracts are subjected to acidic hydrolysis to release conjugated forms of fluridone and the metabolite. Sample extracts are purified by liquid-liquid partitioning and Florisil Sep-Pak column chromatography. Both compounds are separated and measured by reverse phase liquid chromatography with UV detection at 313 nm. In the absence of interfering peaks, the method has a detection limit of approximately 0.04 ppm of either compound. Overall, recoveries averaged 96% for fluridone and 78% for the metabolite for all tissue types combined.

Automated extraction technique for determination of experimental insecticide nifluridide and its cyclized product in water by high pressure liquid chromatography

A method is described for the simultaneous determination of the experimental insecticide nifluridide (N-(2-amino-3-nitro-5-(trifluoromethyl)phenyl)-2,2,3,3-tetrafluoropropanamide) and its cyclized product, EL-919 (7-nitro-2-(1,1,2,2-tetrafluoroethyl)-5-(trifluoromethyl)benzimidazole), in water. Both compounds are extracted by passage of up to 500 mL water through two Sep-Pak C18 cartridges joined in series. The extraction is automated by using vacuum. The compounds are eluted from the cartridges with acetonitrile. Both compounds are then separated and measured by high pressure liquid chromatography with UV detection at 235 nm. Recoveries were 91.2-97.1% nifluridide and 82.7-98.0% EL-919 for deionized water samples fortified with 0.001-0.1 ppm nifluridide and 0.005-0.1 ppm EL-919. Analysis of water samples (pH 8) from bluegill and rainbow trout toxicity studies with nifluridide resulted in a half-life determination of 10 h at 13 degrees C and 2.5 h at 20 degrees C with nearly quantitative conversion to EL-919 within 96 h.

Gas chromatographic determination of fluridone aquatic herbicide and its major metabolite in fish

A gas-liquid chromatographic (GLC) method is described for determining residues of the aquatic herbicide fluridone (1-methyl-3-phenyl-5-[3-(trifluoromethyl)phenyl]-4(1H)-pyridinone) and its major metabolite (1-methyl-3-(4-hydroxyphenyl)-5-[3-(trifluoromethyl)phenyl]-4(1H)-pyridinone) in fish. Both compounds are extracted from fish tissue with methanol, and the extracts are subjected to acidic hydrolysis to release conjugated forms of fluridone and the metabolite. After purification by liquid-liquid partitioning, sample extracts are reacted with methyl iodide to methylate the metabolite, and then both fluridone and the metabolite are brominated with phosphorus tribromide. After purification by Florisil column chromatography, the derivatives are separated and measured by electron capture GLC. The method is capable of determining approximately 0.01 ppm of both compounds in fish, and recoveries have averaged 84 +/- 14.7% for fluridone and 83 +/- 13.4% for the metabolite.