Serial changes in spirometry during an ascent to 5,300 m in the Nepalese Himalayas

The aims of the present study were to determine the changes in forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1) and peak expiratory flow (PEF), during an ascent to 5,300 m in the Nepalese Himalayas, and to correlate the changes with arterial oxygen saturation measured by pulse oximetry (SpO2) and symptoms of acute mountain sickness (AMS). Forty-six subjects were studied twice daily during an ascent from 2,800 m (mean barometric pressure 550.6 mmHg) to 5,300 m (mean barometric pressure 404.3 mmHg) during a period of between 10 and 16 days. Measurements of FVC, FEV1, PEF, SpO2, and AMS were recorded. AMS was assessed using a standardized scoring system. FVC fell with altitude, by a mean of 4% from sea level values [95% confidence intervals (CI) 0.9% to 7.4%] at 2,800 m, and 8.6% (95% CI 5.8 to 11.4%) at 5,300 m. FEV1 did not change with increasing altitude. PEF increased with altitude by a mean of 8.9% (95% CI 2.7 to 15.1%) at 2,800 m, and 16% (95% CI 9 to 23%) at 5,300 m. These changes were not significantly related to SpO2 or AMS scores. These results confirm a progressive fall in FVC and increase in PEF with increasing hypobaric hypoxia while FEV1 remains unchanged. The increase in PEF is less than would be predicted from the change in gas density. The fall in FVC may be due to reduced inspiratory force producing a reduction in total lung capacity; subclinical pulmonary edema; an increase in pulmonary blood volume, or changes in airway closure. The absence of a correlation between the spirometric changes and SpO2 or AMS may simply reflect that these measurements of pulmonary function are not sufficiently sensitive indicators of altitude-related disease. Further studies are required to clarify the effects of hypobaric hypoxia on lung volumes and flows in an attempt to obtain a unifying explanation for these changes.

The short-term repeatability of histamine bronchial testing in young males. The SUS study

We have measured bronchial responsiveness (BR) to histamine on two occasions between 5 and 24 h apart, to determine if conventional and new indices of BR are repeatable. A random sample of 29 healthy male subjects with a mean age of 19 (SD 3.44) years from a larger study repeated a Yan method test of BR, recording both partial and maximal expiratory flow volume (PEFV and MEFV) curves. From the MEFV curves log-dose slopes (LDS) for forced expiratory volume in 1 sec (FEV1), forced expiratory flow between 25% and 75% of forced vital capacity (FVC) (FEF(25-75%)), mean expiratory flow at 30% and 40% of FVC (MEF30, MEF40), and the first moment of the spirogram (alpha1) truncated at 75% and 90% of FVC were calculated, as well as the provocative dose that induces a 20% fall in FEV1 (PD20FEV1). From the PEFV curves LDS for alpha(1)75% and alpha(1)90%, and MEF30 and MEF40 were derived. Apart from MEF30 and alpha(1)90% the second test was significantly lower (P<0.05) than the first when measuring the repeatability of spirometric indices, whereas the LDS of the indices showed no significant change. The repeatability expressed as intra-class correlation coefficient (ICC) was highest for LDS FEV1 (0.87), second highest for LDS MEF40 (0.67) and LDS MEF30 (0.65). The LDS for moment indices were much less repeatable and the lowest ICC was found in all LDS indices derived from PEFV curves. Within-subject variance was not influenced by atopic status, smoking habits or recordable PD20FEV1. As tests for bronchial hyper-responsiveness (BHR) the LDS of FEV1, MEF40 and MEF30 seem to be acceptable for use in population studies.

Anticoagulants or antiplatelet therapy for non-rheumatic atrial fibrillation and flutter

BACKGROUND

Atrial fibrillation (AF) carries a high risk of stroke and other thromboembolic events. Appropriate use of drugs to prevent thromboembolism in patients with AF involves comparing the patient's risk of stroke to the risk of hemorrhage from medication use.

OBJECTIVES

To quantify risk of stroke, major hemorrhage and death from using medications that have been rigorously evaluated for prevention of thromboembolism in AF.

SEARCH STRATEGY

Articles were identified through the Cochrane Collaboration's CENTRAL database and MEDLINE until December 1999.

SELECTION CRITERIA

Included Randomized controlled trials of drugs to prevent thromboembolism in adults with non-postoperative AF. Excluded RCTS of patients with rheumatic valvular disease.

DATA COLLECTION AND ANALYSIS

Data were abstracted by two reviewers. Odds ratios from all qualitatively similar studies were combined, with weighting by study size, to yield aggregate odds ratios for stroke, major hemorrhage, and death for each drug.

MAIN RESULTS

Fourteen articles were included in this review. Warfarin was more efficacious than placebo for primary stroke prevention [aggregate odds ratio (OR) of stroke=0.30 [95% Confidence Interval (C.I.) 0.19,0.48]], with moderate evidence of more major bleeding [ OR= 1.90 [95% C.I. 0.89,4.04].]. Aspirin was inconclusively more efficacious than placebo for stroke prevention [OR=0.68 [95% C.I. 0.29,1.57]], with inconclusive evidence regarding more major bleeds [OR=0.81[95% C.I. 0.37,1.78]]. For primary prevention, assuming a baseline risk of 45 strokes per 1000 patient-years, warfarin could prevent 30 strokes at the expense of only 6 additional major bleeds. Aspirin could prevent 17 strokes, without increasing major hemorrhage. In direct comparison, there was moderate evidence for fewer strokes among patients on warfarin than on aspirin [aggregate OR=0.64[95% C.I. 0.43,0.96]], with only suggestive evidence for more major hemorrhage [OR =1.58 [95% C.I. 0.76,3.27]]. However, in younger patients, with a mean age of 65 years, the absolute reduction in stroke rate with warfarin compared to aspirin was low (5.5 per 1000 person-years) compared to an older group (15 per 1000 person-years). Low-dose warfarin or low-dose warfarin with aspirin was less efficacious for stroke prevention than adjusted-dose warfarin.

REVIEWER'S CONCLUSIONS

The evidence strongly supports warfarin in AF for patients at average or greater risk of stroke, although clearly there is a risk of hemorrhage. Although not definitively supported by the evidence, aspirin may prove to be useful for stroke prevention in sub-groups with a low risk of stroke, with less risk of hemorrhage than with warfarin. Further studies are needed of low- molecular weight heparin and aspirin in lower risk patients.

Methodologic challenges in developing and implementing measures of quality for child health care

OBJECTIVE

To review the major building blocks in measurement of quality for child health care, with recommendations for future research.

METHODS

We describe a framework of building blocks for quality measurement and discuss how an investigator's choices for each component are constrained by the special features of child health care.

RESULTS

Methodologic challenges for children's health care include developmental change and dependency on others, fragmentary care and inadequate health care data, unusual care settings, potential for long-term consequences, proxy reporting of outcomes and patient experience, small sample sizes, and lack of evidence that links processes and outcomes of care and of methods for risk adjustment. We cite examples of child-specific measures of quality that illustrate solutions to these challenges.

CONCLUSIONS

Children are different from adults, and measures of health care quality for children must differ from those for adults. We suggest future research on measures of quality directed toward overcoming the methodologic problems specific to child health care.

Ethanol-mediated CYP1A1/2 induction in rat skeletal muscle tissue

The causes of non-trauma-mediated rhabdomyolysis are not well understood. It has been speculated that ethanol-associated rhabdomyolysis may be attributed to ethanol induction of skeletal muscle cytochrome P450(s), causing drugs such as acetaminophen or cocaine to be metabolized to myotoxic compounds. To examine this possibility, the hypothesis that feeding ethanol induces cytochrome P450 in skeletal muscle was tested. To this end, rats were fed an ethanol-containing diet and skeletal muscle tissue was assessed for induction of CYP2E1 and CYP1A1/2 by immunohistochemical procedures; liver was examined as a positive control tissue. Enzymatic assays and Western blot analyses were also performed on these tissues. In one feeding system, ethanol-containing diets induced CYP1A1/2 in soleus, plantaris, and diaphragm muscles, with immunohistochemical staining predominantly localized to capillaries surrounding myofibers. Antibodies to CYP2E1 did not react with skeletal muscle tissue from animals receiving a control or ethanol-containing diet. However, neither skeletal muscle CYP1A1/2 nor CYP2E1 was induced when ethanol diets were administered by a different feeding system. Ethanol consumption can induce some cytochrome P450 isoforms in skeletal muscle tissue; however, the mechanism of CYP induction is apparently complex and appears to involve factors in addition to ethanol, per se.

Novel S-nitrosothiols do not engender vascular tolerance and remain effective in glyceryltrinitrate-tolerant rat femoral arteries

Organic nitrates, such as glyceryltrinitrate, are nitric oxide (NO) donor drugs that engender tolerance with long-term use. Here, we tested the hypothesis that our novel S-nitrosothiols, N-(S-nitroso-N-acetylpenicillamine)-2-amino-2-deoxy-1,3,4,6, tetra-O-acetyl-beta-D-glucopyranose (RIG200) and S-nitroso-N-valeryl-D-penicillamine (D-SNVP), do not induce vascular tolerance ex vivo. Femoral arteries from adult male Wistar rats were preconstricted with phenylephrine and perfused with the NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME). Perfusion pressure was measured during 20 h treatment with supramaximal concentrations of NO donor (10 microM). Perfusion with glyceryltrinitrate caused a vasodilatation, which recovered over 2-20 h. In contrast, the S-nitrosothiols caused vasodilatations that were maintained throughout the 20 h perfusion period. Responses to S-nitrosothiols were partially reversed by the NO scavenger ferrohaemoglobin and fully reversed by the soluble guanylate cyclase inhibitor [1H-[1,2,4] oxadiazole [4,3-a]quinoxaline-1-one (ODQ). Glyceryltrinitrate-tolerant vessels were fully responsive to bolus injections of S-nitrosothiols. Resistance to tolerance is an attractive property of our novel compounds, particularly in view of their sustained activity in arteries with damaged endothelium.

Efficacy of agents for pharmacologic conversion of atrial fibrillation and subsequent maintenance of sinus rhythm: a meta-analysis of clinical trials

CONTEXT

Physicians have little evidentiary guidance for pharmacologic agent selection for atrial fibrillation (AF).

OBJECTIVE

To assess antiarrhythmic agent efficacy for AF conversion and subsequent maintenance of sinus rhythm (MSR).

DATA SOURCE

We searched the clinical trial database of the Cochrane Collaboration and MEDLINE encompassing literature from 1948 to May 1998.

STUDY SELECTION

We selected 36 (28%) articles eligible as randomized trials of nonpostoperative AF conversion or MSR in adults.

DATA EXTRACTION

Study quality; rates of conversion, MSR, and adverse events were extracted.

DATA SYNTHESIS

Compared with control treatment (placebo, verapamil, diltiazem, or digoxin), the odds ratio (OR) for conversion was greatest for ibutilide/dofetilide (OR=29.1; 95% confidence interval [CI], 9.8-86.1) and flecainide (OR=24.7; 95% CI, 9.0-68.3). Less strong but conclusive evidence existed for propafenone (OR=4.6; 95% CI, 2.6-8.2). Quinidine (OR=2.9; 95% CI, 1.2-7.0) had moderate evidence of efficacy for conversion. Disopyramide (OR=7.0; 95% CI, 0.3-153.0) and amiodarone (OR=5.7; 95% CI, 1.0-33.4) had suggestive evidence of efficacy. Sotalol (OR=0.4; 95% CI, 0.0-3.0) had suggestive evidence of negative efficacy. For MSR, strong evidence of efficacy existed for quinidine (OR=4.1; 95% CI, 2.5-6.7), disopyramide (OR=3.4; CI, 1.6-7.1), flecainide (OR=3.1; 95% CI, 1.5-6.2), propafenone (OR=3.7; 95% CI, 2.4-5.7), and sotalol (OR=7.1; 95% CI, 3.8-13.4). The only amiodarone data, from comparison with disopyramide, provided moderate evidence of efficacy for MSR. No trial evaluated procainamide. Direct agent comparisons and adverse event data were limited.

CONCLUSIONS

Although multiple antiarrhythmic agents had strong evidence of efficacy compared with control treatment for MSR, ibutilide/dofetilide and flecainide had particularly strong evidence of efficacy compared with control treatment for AF conversion. There is sparse and inconclusive evidence on direct agent comparisons and adverse event rates. Obtaining information regarding these relative efficacies should be a research priority.

Influence of beta-naphthoflavone on 7,12-dimethylbenz(a)anthracene metabolism, DNA adduction, and tumorigenicity in rainbow trout

Metabolism, DNA adduction, and tumor induction by 7, 12-dimethylbenz(a)anthracene (DMBA) were examined in cultured trout liver cells and in vivo in trout. Modulating CYP1A1 activity indicated this enzyme plays a significant role in metabolizing DMBA to water-soluble compounds in isolated trout liver cells. The major DMBA metabolites identified in trout liver cells were 10-, 11-, 8,9-, and 5,6-DMBA dihydrodiols, and DMBA, 2- or 3- or 4-phenol; 7-OH-methyl-12-methyl-benz(a)anthracene and 12-OH-methyl-7-methyl-benz(a)anthracene were minor metabolites. A very small amount of DMBA-3,4-dihydrodiol was detected, and polar metabolites, which did not migrate with any DMBA metabolite standards, were observed. Incubating trout hepatocytes with DMBA-3, 4-dihydrodiol produced three prominent, nonpolar adducts indistinguishable from those in mouse embryo cells. However, DMBA-DNA adducts, formed in trout in vivo or in trout liver cells exposed to DMBA, were predominantly more polar than those formed in mouse embryo fibroblasts, and levels of DMBA-DNA adducts formed in trout liver cells were not significantly altered by modulating CYP1A1 activity. No significant repair of DMBA-DNA adducts was detected in cultured trout liver cells over a 48-h period, supporting previous studies indicating that fish are less efficient than mammals in repairing polyaromatic hydrocarbon DNA adducts. Compared to animals receiving DMBA alone, beta-naphthoflavone pretreatment in vivo did not affect hepatic CYP1A1, DMBA-DNA adducts, nor hepatic tumor response; but did significantly reduce tumor response in two other target organs. These results collectively indicate that DMBA bioactivation to DNA-binding metabolites in trout liver cells and mouse embryo cells predominantly involve different metabolic pathways to form the DNA-binding intermediates.

Novel S-nitrosothiols do not engender vascular tolerance and remain effective in glyceryl trinitrate-tolerant rat femoral arteries

Organic nitrates, such as glyceryl trinitrate, are nitric oxide (NO) donor drugs that engender tolerance with long-term use. Here, we tested the hypothesis that our novel S-nitrosothiols, N-(S-nitroso-N-acetylpenicillamine)-2-amino-2-deoxy-1,3,4,6, tetra-O-acetyl-beta-D-glucopyranose (RIG200) and S-nitroso-N-valeryl-D-penicillamine (D-SNVP), do not induce vascular tolerance ex vivo. Femoral arteries from adult male Wistar rats were preconstricted with phenylephrine and perfused with the NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME). Perfusion pressure was measured during 20-h treatment with supramaximal concentrations of NO donor (10 microM). Perfusion with glyceryltrinitrate caused a vasodilatation, which recovered over 2-20 h. In contrast, the S-nitrosothiols caused vasodilatations that were maintained throughout the 20-h perfusion period. Responses to S-nitrosothiols were partially reversed by the NO scavenger ferrohaemoglobin and fully reversed by the soluble guanylate cyclase inhibitor [1H-[1,2,4] oxadiazole [4,3-a]quinoxaline-1-one (ODQ). Glyceryltrinitrate-tolerant vessels were fully responsive to bolus injections of S-nitrosothiols. Resistance to tolerance is an attractive property of our novel compounds, particularly in view of their sustained activity in arteries with damaged endothelium.

Parental preferences for primary and specialty care collaboration in the management of teenagers with congenital heart disease

OBJECTIVES

We examined parental preferences for locus of service delivery for their teenager's congenital heart disease (CHD) and the influence of disease severity, sociodemographic factors, and insurance on these preferences.

METHODS

A consecutive sample of parents of teenagers followed in a pediatric cardiology clinic completed a mailed questionnaire. Disease severity was classified as low (</=1 cardiovascular procedure), moderate (>1 cardiovascular procedure), and high (cyanosis or single ventricle physiology).

RESULTS

Eighty-six of 148 parents responded (58%): 40, low severity; 36, moderate severity; and 10, high severity of illness. Parents preferred using primary care providers (PCPs) as a point of first contact for all 11 of 11 general health concerns and 5 of 7 potential cardiovascular-related concerns: chest pain (52%), syncope (73%), seeming seriously ill (79%), sports physical examination (79%), and endocarditis prophylactic antibiotics (94%). Increasing disease severity was significantly associated with preferring cardiologists for 6 of 7 cardiovascular-related concerns. Overall, 58% of parents viewed their care as a PCP-cardiologist comanagement model versus a cardiologist-dominated model. Lower family income (odds ratio [OR]: 1.5; confidence interval [CI]: 1.0-2.2) and severity of illness (OR: 2.1; CI: 1.0-4.4) were associated with a comanagement model of health care versus a cardiologist-dominated model.

CONCLUSIONS

This study suggests that the majority of parents of teenagers with CHD prefer to use their teenager's PCP for all routine health care needs and many cardiovascular health needs. Severity of illness and family income are positively associated with greater preference for cardiologist care.

Peak flowmeter resistance decreases peak expiratory flow in subjects with COPD

Previous studies have shown that the added resistance of a mini-Wright peak expiratory flow (PEF) meter reduced PEF by approximately 8% in normal subjects because of gas compression reducing thoracic gas volume at PEF and thus driving elastic recoil pressure. We undertook a body plethysmographic study in 15 patients with chronic obstructive pulmonary disease (COPD), age 65.9 +/- 6.3 yr (mean +/- SD, range 53-75 yr), to examine whether their recorded PEF was also limited by the added resistance of a PEF meter. The PEF meter increased alveolar pressure at PEF (Ppeak) from 3.7 +/- 1.4 to 4.7 +/- 1.5 kPa (P = 0.01), and PEF was reduced from 3.6 +/- 1.3 l/s to 3.2 +/- 0.9 l/s (P = 0.01). The influence of flow limitation on PEF and Ppeak was evaluated by a simple four-parameter model based on the wave-speed concept. We conclude that added external resistance in patients with COPD reduced PEF by the same mechanisms as in healthy subjects. Furthermore, the much lower Ppeak in COPD patients is a consequence of more severe flow limitation than in healthy subjects and not of deficient muscle strength.

S and Z alpha1-antitrypsin alleles are risk factors for bronchial hyperresponsiveness in young farmers: an example of gene/environment interaction

Several studies have found an association between the rare Pi-alleles and asthma or bronchial hyperresponsiveness (BHR). This study deals with the effect of Pi-type on BHR among 2,308 young Danish people living in rural areas with a mean +/- SD age of 19.7+/-2.4 yrs. Interviews, pulmonary function testing, bronchial histamine provocation and skin-prick tests were performed. Serum alpha1-antitrypsin levels were determined and phenotyping was performed by means of isoelectric focusing and the subjects categorized into four groups: 1) MM and MX; 2) MS; 3) MZ; and 4) rare, i.e. SZ, SS and ZZ. Among the farmers, a significant positive trend for sensitization towards house dust mites was found, ranging from 12% in the MM group to 22% in the rare Pi-group. A positive test for trend was found within the Pi-groups in a one-sided test for doctor-diagnosed asthma with a peak prevalence of 40% for these symptoms among smokers in the rare Pi-group. On multiple logistic regression analysis, an increased odds ratio (OR) for BHR was found among farming school attendants with the rare Pi-alleles. The OR (95% confidence interval) was 1.71 (0.84-3.49) for MS, 1.93 (1.10-3.39) for MZ and 4.34 (1.19-15.8) for the rare Pi-group. Such a relationship was not found among the conscripts. These results show that a gene/environment interaction may exist between the farming occupation and the rare Pi-alleles, leading to a higher proportion of bronchial hyperresponsiveness related to the rare Pi-alleles in farming school attendants, in contrast to what is found among other young people living in rural areas.

Peak expiratory flow profiles delivered by pump systems. Limitations due to wave action

Pump systems are currently used to test the performance of both spirometers and peak expiratory flow (PEF) meters, but for certain flow profiles the input signal (i.e., requested profile) and the output profile can differ. We developed a mathematical model of wave action within a pump and compared the recorded flow profiles with both the input profiles and the output predicted by the model. Three American Thoracic Society (ATS) flow profiles and four artificial flow-versus-time profiles were delivered by a pump, first to a pneumotachograph (PT) on its own, then to the PT with a 32-cm upstream extension tube (which would favor wave action), and lastly with the PT in series with and immediately downstream to a mini-Wright peak flow meter. With the PT on its own, recorded flow for the seven profiles was 2.4 +/- 1.9% (mean +/- SD) higher than the pump's input flow, and similarly was 2.3 +/- 2.3% higher than the pump's output flow as predicted by the model. With the extension tube in place, the recorded flow was 6.6 +/- 6.4% higher than the input flow (range: 0.1 to 18.4%), but was only 1.2 +/- 2.5% higher than the output flow predicted by the model (range: -0.8 to 5.2%). With the mini-Wright meter in series, the flow recorded by the PT was on average 6.1 +/- 9.1% below the input flow (range: -23.8 to 2. 5%), but was only 0.6 +/- 3.3% above the pump's output flow predicted by the model (range: -5.5 to 3.9%). The mini-Wright meter's reading (corrected for its nonlinearity) was on average 1.3 +/- 3.6% below the model's predicted output flow (range: -9.0 to 1. 5%). The mini-Wright meter would be deemed outside ATS limits for accuracy for three of the seven profiles when compared with the pump's input PEF, but this would be true for only one profile when compared with the pump's output PEF as predicted by the model. Our study shows that the output flow from pump systems can differ from the input waveform depending on the operating configuration. This effect can be predicted with reasonable accuracy using a model based on nonsteady flow analysis that takes account of pressure wave reflections within pump systems.

The evidence regarding the drugs used for ventricular rate control

OBJECTIVE

Our goal was to determine what drugs are most efficacious for controlling the ventricular rate in patients with atrial fibrillation.

SEARCH STRATEGY

We conducted a systematic review of the literature published before May 1998, beginning with searches of The Cochrane Collaboration's CENTRAL database and MEDLINE.

SELECTION CRITERIA

We included English-language articles describing randomized controlled trials of drugs used for heart rate control in adults with atrial fibrillation.

DATA COLLECTION/ANALYSIS

Abstracts of trials were reviewed independently by 2 members of the study team. We reviewed English-language abstracts of non-English-language publications to assess qualitative consistency with our results.

MAIN RESULTS

Forty-five articles evaluating 17 drugs met our criteria for review. In the 5 trials of verapamil and 5 of diltiazem, heart rate was reduced significantly (P <.05), both at rest and with exercise, compared with placebo, with equivalent or improved exercise tolerance in 6 of 7 comparisons. In 7 of 12 comparisons of a beta-blocker with placebo, the beta-blocker was efficacious for control of resting heart rate, with evidence that the effect is drug specific, as nadolol and atenolol proved to be most efficacious. All 9 comparisons demonstrated good heart rate control with beta-blockers during exercise, although exercise tolerance was compromised in 3 of 9 comparisons. In 7 of 8 trials, digoxin administered alone slowed the resting heart rate more than placebo, but it did not significantly slow the rate during exercise in 4 studies. The trials evaluating other drugs yielded insufficient evidence to support their use, but those drugs may yet be promising.

CONCLUSIONS

The calcium-channel blockers verapamil or diltiazem, or select beta-blockers are efficacious for heart rate control at rest and during exercise for patients with atrial fibrillation without a clinically important decrease in exercise tolerance. Digoxin is useful when rate control during exercise is less a concern.

Impact of correcting peak flow for nonlinear errors on air pollutant effect estimates from a panel study

Air pollutant effects are commonly investigated using panel studies employing daily measurement of changes in peak expiratory flow (PEF). Variable orifice PEF meters are inaccurate with a nonlinear relationship to actual PEF. The impact on a panel study of correcting these errors was examined. Twice-daily PEF readings were taken by 147 9-yr old children for 8 weeks and corrected using an equation derived from the response of 32 Vitalograph meters to a servomechanism-controlled pump. Pollutant effect estimates for corrected and uncorrected readings were derived using a regression approach incorporating appropriate confounders. Correction impacted little on mean PEF values (333.1-334.2 L x min(-1)), but did alter effect sizes. Nonsignificant nitrogen dioxide estimates for the entire panel decreased by up to 73%, but, for symptomatic/atopic children, a significant 5-day mean result was lost (decrease in effect size from -2.53 to -0.90% per 10 parts per billion (ppb)) and lag 0 became significant (decrease from -0.51 to -1.22% per 10 ppb). Mass concentration estimates of particles with a 50% cut-off aerodynamic diameter of 2.5 microm moved in both directions (-0.22 changed to 0.11% per 10 microg x m(-1) lag 3 and -0.29 to -0.73% per 10 microg x m(-3) for the 5-day mean). Correction of nonlinearity of peak expiratory flow meters influenced the overall outcome of this panel study, and the changes in effect estimates would be sufficient to alter the interpretation of some studies. For adults, a greater change in effect estimates may follow the larger correction required for their usual peak expiratory flow range.

The shape of the maximum expiratory flow-volume curve reflects exposure in farming

The objective of the study was to examine the effect of farming exposure, respiratory symptoms and smoking on the shape of the MEFV-curve in 1,691 male farming students and 407 male controls and to relate the slope ratio with FEV(1) and FEV(1) /FVC. Each subject underwent a medical interview and the slope ratios from the MEFV-curve at 75 (SR75), 50 (SR50) and 25 (SR25) %FVC together with FEV1 and FVC were recorded. Histamine bronchial reactivity (Yan method) was measured and skin prick test with inhalant allergens was performed. In smokers, SR75 increased with increasing exposure to: general farming, swine and dairy cattle (p< or =0.020). SR50 increased with increasing exposure to farming (p=0.015). In non-smokers, SR25 increased with increasing exposure to swine and dairy cattle (p=0. 021) and increased SR25 was associated with sensitisation to house dust mite (p=0.017). Data revealed an interaction between smoking and exposure to farming. FEV(1) and FEV(1)/FVC was not associated with farming exposure or production animals. FEV1 and FEV(1)/FVC (p< or =0.003) were lower among subjects wi bronchial hyperresponsiveness and asthma (FEV(1) and asthma only in smokers). SR75 (p=0.037) and SR50 (p=0.024) were increased in subjects with asthma and SR75 was increased in subjects with bronchial hyperresponsiveness, but only in smokers (p=0.002). In conclusion, exposure to farming seems to influence the shape of the MEFV-curve and there are indications of interaction between exposure to organic dust and smoking. These changes are seen only in the slope ratios and not in FEV(1) and FEV(1)/FVC. However, FEV(1) and FEV(1)/FVC are superior to slope ratios in differentiating healthy subjects from those with respiratory symptoms.

Prevention of thromboembolism in atrial fibrillation. A meta-analysis of trials of anticoagulants and antiplatelet drugs

OBJECTIVE

Appropriate use of drugs to prevent thromboembolism in patients with atrial fibrillation (AF) involves comparing the patient's risk of stroke and risk of hemorrhage. This review summarizes the evidence regarding the efficacy of these medications.

METHODS

We conducted a meta-analysis of randomized controlled trials of drugs used to prevent thromboembolism in adults with nonpostoperative AF. Articles were identified through the Cochrane Collaboration's CENTRAL database and MEDLINE until May 1998.

MAIN RESULTS

Eleven articles met criteria for inclusion in this review. Warfarin was more efficacious than placebo for primary stroke prevention (aggregate odds ratio [OR] of stroke = 0.30, 95% confidence interval [CI] 0.19, 0.48), with moderate evidence of more major bleeding (OR 1.90; 95% CI 0.89, 4.04). Aspirin was inconclusively more efficacious than placebo for stroke prevention (OR 0.56, 95% CI 0.19, 1.65), with inconclusive evidence regarding more major bleeds (OR 0.81, 95% CI 0.37, 1.77). For primary prevention, assuming a baseline risk of 45 strokes per 1,000 patient-years, warfarin could prevent 30 strokes at the expense of only 6 additional major bleeds. Aspirin could prevent 17 strokes, without increasing major hemorrhage. In direct comparison, there was evidence suggesting fewer strokes among patients on warfarin than among patients on aspirin (aggregate OR 0.64, 95% CI 0.43, 0.96), with only suggestive evidence for more major hemorrhage (OR 1.60, 95% CI 0.77,3.35). However, in younger patients, with a mean age of 65 years, the absolute reduction in stroke rate with warfarin compared with aspirin was low (5.5 per 1,000 person-years) compared with an older group (15 per 1,000 person-years).

CONCLUSION

In general, the evidence strongly supports warfarin for patients with AF at average or greater risk of stroke. Aspirin may prove to be useful in subgroups with a low risk of stroke, although this is not definitively supported by the evidence.

Endogenous prostaglandin formation in the field-stimulated guinea-pig vas deferens: comparison of the inhibitory effects of indomethacin and NS-398

Prostaglandin (PG) E2 inhibited both phases of contraction produced by electrical field stimulation of the guinea-pig vas deferens. PGF2alpha and PGD2 were without effect on this preparation. Carbacyclin (a PGI2) analogue inhibited the first phase of contraction at higher concentrations, whereas U46619 (a thromboxane mimetic) potentiated both phases of contraction. As exogenous arachidonic acid inhibits both phases of contraction of the electrically field-stimulated guinea-pig vas deferens, it is likely that the arachidonic acid is converted to PGE2 in the vas deferens. Indomethacin, a non-specific inhibitor of prostaglandin H synthase (PGHS), attenuated the inhibitory actions of exogenous arachidonic acid when examined on the first phase of contraction. NS-398, a relatively specific inhibitor of PGHS-2, also prevented the inhibitory action of exogenous arachidonic acid. However, NS-398 was much less effective than indomethacin in this respect even though NS-398 and indomethacin inhibit PGHS-2 with similar potencies. Consequently, the findings suggest that exogenous arachidonic acid is converted to PGE2 in the guinea-pig vas deferens by the actions of PGHS-1 and, to a lesser extent, by PGHS-2.

Food service in long day care centres--an opportunity for public health intervention

OBJECTIVE

To determine the characteristics of long day care centre operations, food service management practices, and nutrition resources use and needs.

METHOD

In October 1996, all 330 long day care centres in Western Australia were surveyed by telephone to gather information to help develop strategies for food service improvement.

RESULTS

The response rate was 85%. An accreditation committee directed operations in 76% of centres. Most centres employed a cook with limited or no cooking training. Coordinators identified training needs for cooks that are specific to the National Childcare Accreditation Council's Quality Improvement and Accreditation System (QIAS) guidelines: food hygiene; nutritional and food requirements of children; menu planning; and multicultural cooking.

CONCLUSIONS

National standards for the quantification of foods to meet children's nutritional requirements in long day care would allow for consistency in educating child care workers, training cooks, and establishing and assessing government regulations and the QIAS guidelines. Nine recommendations for strategies to improve food service in long day care are presented.

IMPLICATIONS

There are two main messages for public health practitioners working to improve the quality of food served to children in long day care: the strong influence of the QIAS guidelines, and the need for specific nutrition recommendations.

Antibody-mediated red blood cell agglutination resulting in spontaneous echocardiographic contrast

Spontaneous echocardiographic contrast is well reported in states of low flow and low shear stress, and the primary blood component involved has been reported as red blood cells via rouleaux formation. This report describes the occurrence of spontaneous echocardiographic contrast from a unique mechanism of IgM-mediated red blood cell agglutination and describes the clinical sequelae.

Effective management of spinal pain in one hundred seventy-seven patients evaluated for manipulation under anesthesia

OBJECTIVE

To demonstrate that manipulation under anesthesia (MUA), a conservative treatment modality, is both safe and efficacious in the treatment of both acute and chronic spinal pain disorders in appropriately selected patients. MUA can be safely used to treat pain arising from the cranial, cervical, thoracic, and lumbar spine, as well as the sacroiliac and pelvic region.

SETTING

An ambulatory surgical center.

SUBJECTS

The treatment group consisted of 177 patients between ages 17 and 65 years. Evaluation followed a treatment algorithm created by the authors as a multidisciplinary approach to patient selection, evaluation, treatment, and timing of specialized referral, in consideration of previously published algorithms. Prior forms of treatment, both conservative and surgical in nature, had failed in these patients.

INTERVENTION

Patients underwent three sequential manipulations under intravenous sedation, followed by 4 to 6 weeks of skilled spinal manipulation and therapeutic modalities.

OUTCOME MEASURES

Data regarding changes in Visual Analog Scale (VAS), range of motion, medication needs, and return to work status were used to document progress. All patients had follow-up for 6 months.

RESULTS

On average, VAS ratings improved by 62.2% in those patients with cervical pain problems. On average, VAS ratings improved by 60.1% in those patients with lumbar pain problems. There was a near-complete reversal in patients out of work before MUA (68.6%) and those returning to unrestricted activities at 6 months after MUA (64.1%). There was a 58.4% reduction in the percentage of patients requiring prescription pain medication from the pre-MUA period to 6 months after MUA. Additionally, 24.0% of the treatment group required no medication at 6 months after MUA.

CONCLUSION

A multidisciplinary approach to evaluation and treatment, including MUA, offers patient benefits above and beyond what can be obtained through the individual providers working alone.

Risk factors in microbial keratitis leading to penetrating keratoplasty

OBJECTIVE

To determine the characteristics of infectious corneal ulcers at the time of presentation to the cornea specialist associated with a favorable response to medical therapy versus a poor outcome manifested by the need for penetrating keratoplasty for therapy or visual rehabilitation.

DESIGN

Retrospective, case-control study.

PARTICIPANTS

A total of 162 patient records were reviewed, including the study group of 30 patients and the control group of 132 patients.

INTERVENTION

A retrospective review of all cases of microbial keratitis presenting to the Cornea Service between January 1, 1989 and December 31, 1995 was conducted. The cases were divided into two groups. The study group consisted of patients with microbial keratitis who failed medical therapy and required penetrating keratoplasty. The control group included patients with infectious ulcers who responded to medical therapy alone.

MAIN OUTCOME MEASURES

The influence of demographics, medical and ocular history, delay in presentation to the primary ophthalmologist or the corneal specialist, topical medications, and contact lens usage were compared. Visual acuity and ulcer characteristics were recorded. The statistical significance was evaluated by the chi-square test for independence and multiple logistic regression.

RESULTS

Older age (P=0.001), delay in referral to the corneal specialist (P<0.03), and treatment with topical steroids prior to presentation (P<0.0001) were statistically significant factors associated with the need for penetrating keratoplasty. Steroid use and the delay in referral were correlated. A past history of ocular surgery (P=0.01), poor visual acuity at presentation (P<0.001), and ulcer characteristics, including central location (P<0.0001), large size (P<0.0001), presence of perforation or descemetocele (P<0.0001), limbal involvement (P<0.0001), and hypopyon (P=0.05), were all associated with the need for penetrating keratoplasty.

CONCLUSIONS

Older age, delay in referral to the corneal specialist, topical steroid treatment, past ocular surgery, poor vision at presentation, large size, and central location of the ulcer are risk factors for poor outcome of microbial keratitis, as indicated by the need for penetrating keratoplasty.

Acetaminophen-induced proliferation of breast cancer cells involves estrogen receptors

Previous studies have shown that acetaminophen, a common analgesic/antipyretic, induces proliferation of cultured breast cancer cells containing both estrogen and progesterone receptors (ER+/PR+). The main objective of this study was to evaluate the involvement of ERs in this effect. First, the effects of therapeutic acetaminophen concentrations were compared in breast cancer cells with high ERs and in T47Dco cells with lower ERs, to determine if acetaminophen-induced proliferation depends on ER levels. Second, the effects of two antiestrogens (ICI 182,780 and 4'-hydroxytamoxifen) on acetaminophen-induced proliferation were determined in three human breast cancer cell lines: two ER+/PR+ (MCF7, T47D) and one ER-/PR- (MDA-MB-231). Third, ER binding assays were performed in MCF7 cells to determine if acetaminophen competed with estradiol for binding to ERs. Proliferation endpoints monitored included percent cells in the DNA synthesis phase of the cell cycle, 3H-thymidine incorporation into DNA, and cell number. Acetaminophen did not induce DNA synthesis in T47Dco cells, but did in cells with higher ER levels, suggesting high ER levels are necessary for acetaminophen to induce proliferation. Antiestrogens inhibited acetaminophen-induced proliferation in ER+/PR+ cells while no effects were observed in ER-/PR- cells, further supporting ER involvement. However, acetaminophen did not compete with estradiol for binding to ERs in ER+/PR+ cells. Collectively, these data suggest that acetaminophen induces breast cancer cell proliferation via ERs without binding to ERs like estradiol. The second purpose of this study was to determine if acetaminophen is estrogenic/antiestrogenic in vivo (uterotrophic assays). Acetaminophen has no antiestrogenic/estrogenic activity in mice or rats uteri.

Acetaminophen alters estrogenic responses in vitro: inhibition of estrogen-dependent vitellogenin production in trout liver cells

The purpose of this study was to determine if acetaminophen altered estrogen-dependent vitellogenin production in isolated trout liver cells. Estrogen-induced vitellogenesis was studied in liver cells isolated from male trout and cultured in defined medium; vitellogenin secreted into culture medium was quantitated using immunological procedures. Vitellogenin production was absolutely dependent on the addition of estradiol (10(-6) M) to liver cells from male trout. Acetaminophen produced a dose-dependent inhibition of vitellogenin production; approximately 50% inhibition was achieved with 0.05 mM acetaminophen, while 0.3 mM acetaminophen inhibited secreted vitellogenin to undetectable levels. In contrast, these concentrations of acetaminophen (< or = 1 mM) did not significantly alter the production of secreted albumin, determined immunologically, or cause detectable toxicity. Higher doses of acetaminophen were toxic, but did not induce DNA fragmentation in the trout liver cells. Acetaminophen reduction of estradiol-induced vitellogenin production was accompanied by a dose-dependent decrease in vitellogenin mRNA, indicating acetaminophen inhibited a step prior to, or during, formation of vitellogenin mRNA. Estrogen receptor-binding assays demonstrated that acetaminophen did not reduce binding of [3H]-estradiol to trout liver estrogen receptor. In addition, catabolism of estradiol to water-soluble metabolites was not significantly altered by acetaminophen. These studies indicate that non-toxic concentrations of acetaminophen specifically inhibit estrogen-dependent vitellogenin synthesis and suggest that this commonly used drug may alter estrogen-regulated processes.

Positional isomers of acetaminophen differentially induce proliferation of cultured breast cancer cells

This study demonstrates that acetaminophen (p-acetamidophenol) stimulates proliferation of estrogen-responsive cultured breast cancer cells and assesses if the proliferative activity of p-acetamidophenol is influenced by the -OH moiety position on the benzene ring. The effects of p-, m-, and o-acetamidophenol on cell number and on percentage cells in S phase of the cell cycle were determined for two estrogen receptor positive, human breast cancer cell lines, T47D and MCF7. Therapeutic concentrations of p-acetamidophenol (0.1 mM) significantly increased breast cancer cell proliferation. The relative order of potency of isomers in stimulating proliferation in both cell types was p- > m- > o-acetamidophenol, indicating the -OH position on the benzene ring influences the proliferation output in cultured breast cancer cells.

Lung status in young Danish rurals: the effect of farming exposure on asthma-like symptoms and lung function

The aim of this study was to assess the prevalence of asthma (self-reported) and relate this to lung function and factors associated with asthma in young farmers. Two hundred and ten female and 1,691 male farming students together with 407 males controls were studied. Each subject underwent a medical interview; forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) were recorded using a dry wedge spirometer. Histamine bronchial reactivity was measured using the Yan method. Skin prick testing was performed using inhalant allergens. Nonsmokers had lower prevalence of asthma (5.4-10.8%) than smokers (11.3-21.0%) (p<0.05). Females reported symptoms of asthma nearly twice as often as males. Sex, smoking and a family history of asthma/allergy were significantly associated with asthma. Controls had higher standardized FEV1 and FVC residuals than male students, both nonsmokers (0.21 and 0.24) versus (-0.06 and -0.05) and smokers (0.29 and 0.33) versus (-0.11 and 0.13) (p<0.032). Bronchial hyperresponsiveness, asthma, siblings with allergy and working with cattle (controls only) were significantly associated with reduced lung function. In conclusion, the prevalence of asthma was significantly related to smoking, female sex, family history of asthma and allergy. Whilst bronchial hyperresponsiveness was associated with reduced lung function and lung function was slightly reduced in the male farming students, there was no association found between occupational farming exposure and either lung symptoms or lung function.

Acetaminophen alters estrogenic responses in vitro: stimulation of DNA synthesis in estrogen-responsive human breast cancer cells

A limited number of studies have investigated the estrogenic potential of acetaminophen but none has reported its effects on breast cells. Many compounds that alter estrogen-mediated processes in various tissues contain p-phenolic moieties. Acetaminophen is a commonly used analgesic/antipyretic that also contains a p-phenol. This study tested the hypothesis that therapeutic concentrations of acetaminophen alter estrogen-responsive human breast cancer cell DNA synthesis. To this end, a modified E-screen assay was developed to determine the response to acetaminophen of two dichotomous types of human breast cancer cell lines: estrogen-responsive (MCF7, T47D, ZR-75-1) and estrogen-nonresponsive (MDA-MB-231, HS578T). Cells were placed in estradiol-free medium and then exposed to 3 nM estradiol or 0.03-1 mM acetaminophen. The proliferative response was assessed by determining [3H]thymidine incorporation into DNA and by determining the percentage of cells in the DNA synthesis (S) phase of the cell cycle. Concentrations of acetaminophen commonly attained in human plasma with therapeutic doses of this drug (approximately 0.1 mM) were found as effective as estradiol in stimulating DNA synthesis in estrogen-responsive breast cancer cells. Higher acetaminophen concentrations (1 mM) stimulated estrogen-responsive cells to a lesser extent. The combination of estradiol and acetaminophen did not stimulate DNA synthesis in estrogen-responsive cells more than either agent alone. Neither acetaminophen nor estradiol stimulated DNA synthesis in estrogen-nonresponsive human breast cancer cells. These novel findings demonstrate that therapeutic acetaminophen concentrations specifically stimulate estrogen-responsive breast cancer cell DNA synthesis, suggesting that this drug may exert estrogenic effects.

Chronic obstructive pulmonary disease and '150 years of blowing'

Spirometry is now an established and important aspect of investigation of many lung diseases. This article considers the history of spirometry, how we come to use the current indices of dynamic lung function, and the role of spirometry in the management of patients with chronic obstructive pulmonary disease.

The rise and dwell time for peak expiratory flow in patients with and without airflow limitation

The response of peak expiratory flow (PEF) meters may be affected by the magnitude of PEF, the time taken to get to PEF, and the duration that the peak is sustained. We undertook a retrospective study to define the 10 to 90% rise time (RT) and dwell time for flow above 90% (DT90) and 95% (DT95) of PEF. Blows were analyzed that had been recorded using a pneumotachograph from 912 patients older than 17 yr of age (556 men) who routinely attended a lung function laboratory. For each subject, that blow with the largest PEF was used to derive the PEF, FEV1, FVC, RT, DT90, and DT95. The values for RT, DT90, and DT95 were negatively skewed with the median values for men of 58, 29, and 19 ms, respectively, being significantly shorter than those for the women of 67, 49, and 31 ms. From the 912 subjects, there were 277 (153 men) who had all their spirometric indices within the normal range, and 305 (220 men) had both PEF and FEV1 more than 1. 645 SD below predicted, indicating airflow limitation. For subjects with airflow limitation the median RT was significantly smaller than in the normal subjects (men: 46 versus 72 ms, women: 50 versus 72 ms), and the same was found for DT90 (men: 22 versus 40 ms, women: 27 versus 56 ms) and DT95 (men: 15 versus 26 ms, women: 18 versus 34 ms). We conclude that the dwell times for PEF are shorter in men, and the rise and dwell times are shorter in patients with airflow limitation. Profiles used to test PEF meters should encompass the range of rise and dwell times found in subjects most likely to be using PEF meters, that is, those with airflow limitation.

The use of a neural network to detect upper airway obstruction caused by goiter

Goiter is a common condition and can cause upper airway obstruction (UAO), which may be difficult to detect. We have studied maximal expiratory and inspiratory flow volume loops using a neural network to see if this offers a better way to identify patients with UAO. The flow-volume loops from 155 patients with goiter were assessed by a human expert and sorted into those with and without UAO. The reliability of this assessment was judged by using two observers who repeated the sorting 8 wk apart. A set of 46 patients with loops suggesting UAO and a set of 51 patients with normal flow loops were taken from these 155, and the loops from a further 50 subjects with airflow limitation caused by chronic obstructive pulmonary disease were used for training and testing the neural network. Novel and standard indices were derived from the loops and used by the neural network. The kappa score for agreement between each of the observers and the original classification were 0.5 and 0.46, respectively, with the agreement between the observers at each reading of 0.58 and 0.68. The neural network found that a combination of four novel scores for flatness of the expiratory loop, the moment ratio, and the FEV1/PEF ratio was best at identifying UAO with a kappa score of 0.81, a sensitivity of 88%, specificity of 94% and an accuracy of 92%. We conclude that a neural network using only six indices taken from the expiratory limb of a flow-volume loop was better than human experts at identifying flow loops with UAO.

Gas compression in lungs decreases peak expiratory flow depending on resistance of peak flowmeter

It has recently been shown (O. F. Pedersen T. R. Rasmussen, O. Omland, T. Sigsgaard, P. H. Quanjer. and M. R. Miller. Eur. Respir. J. 9: 828-833, 1996) that the added resistance of a mini-Wright peak flowmeter decreases peak expiratory flow (PEF) by approximately 8% compared with PEF measured by a pneumotachograph. To explore the reason for this, 10 healthy men (mean age 43 yr, range 33-58 yr) were examined in a body plethysmograph with facilities to measure mouth flow vs. expired volume as well as the change in thoracic gas volume (Vb) and alveolar pressure (PA). The subjects performed forced vital capacity maneuvers through orifices of different sizes and also a mini-Wright peak flowmeter. PEF with the meter and other added resistances were achieved when flow reached the perimeter of the flow-Vb curves. The mini-Wright PEF meter decreased PEF from 11.4 +/- 1.5 to 10.3 +/- 1.4 (SD) l/s (P < 0.001), PA increased from 6.7 +/- 1.9 to 9.3 +/- 2.7 kPa (P < 0.001), an increase equal to the pressure drop across the meter, and caused Vb at PEF to decrease by 0.24 +/- 0.09 liter (P < 0.001). We conclude that PEF obtained with an added resistance like a mini-Wright PEF meter is a wave-speed-determined maximal flow, but the added resistance causes gas compression because of increased PA at PEF. Therefore, Vb at PEF and, accordingly, PEF decrease.

Western Australian Health Department recommendations for fruit and vegetable consumption--how much is enough?

In 1989 the Nutrition Program of the Health Department of Western Australia determined a minimum recommended daily intake of fruit and vegetables for use in promotion of increased fruit and vegetable consumption. Considerations in the development of this recommendation included: a review of existing recommendations; the protective effects of fruit and vegetables; specification of fruit and vegetables separately or together; classification of fruit and vegetables; definition of a serve; and practical considerations for the implementation of the recommendation. This paper outlines the development of the recommendation to eat at least two average-sized (120-150 g) pieces of fruit and five average-sized (60-90 g) serves of vegetables daily.

Hypoxia, hypocapnia and spirometry at altitude

1. Both hypoxia and hypocapnia can cause broncho-constriction in humans, and this could have a bearing on performance at high altitude or contribute to altitude sickness. We studied the relationship between spirometry, arterial oxygen saturation and end-tidal carbon dioxide (ETCO2) concentration in a group of healthy lowland adults during a stay at high altitude, and then evaluated the response to supplementary oxygen and administration of a beta 2 agonist. 2. We collected spirometric data from 51 members of the 1994 British Mount Everest Medical Expedition at sea level (barometric pressure 101.2-101.6 kPa) and at Mount Everest Base Camp in Nepal (altitude 5300 m, barometric pressure 53-54.7 kPa) using a pocket turbine spirometer. A total of 205 spirometric measurements were made on the 51 subjects during the first 6 days after arrival at Base Camp. Further measurements were made before and after inhalation of oxygen (n = 47) or a beta 2 agonist (n = 39). ETCO2 tensions were measured on the same day as spirometric measurements in 30 of these subjects. 3. In the first 6 days after arrival at 5300 m, lower oxygen saturations were associated with lower forced expiratory volume in 1 s (FEV1; P < 0.02) and forced vital capacity (FVC; P < 0.01), but not with peak expiratory flow (PEF). Administration of supplementary oxygen for 5 min increased oxygen saturation from a mean of 81%-94%, but there was no significant change in FEV1 or FVC, whilst PEF fell by 2.3% [P < 0.001; 95% confidence intervals (CI) -4 to -0.7%]. After salbutamol administration, there was no significant change in PEF, FEV1 or FVC in 35 non-asthmatic subjects. Mean ETCO2 at Everest Base Camp was 26 mmHg, and a low ETCO2 was weakly associated with a larger drop in FVC at altitude compared with sea level (r = 0.38, P < 0.05). There was no correlation between either ETCO2 or oxygen saturation and changes in FEV1 or PEF compared with sea-level values. 4. In this study, in normal subjects who were acclimatized to hypobaric hypoxia at an altitude of 5300 m, we found no evidence of hypoxic broncho-constriction. Individuals did not have lower PEF when they were more hypoxic, and neither PEF nor FEV1 were increased by either supplementary oxygen or salbutamol. FVC fell at altitude, and there was a greater fall in FVC for subjects with lower oxygen saturations and probably lower ETCO2.

Effect of adult-onset deafness on the human central auditory system

Degenerative change in the central auditory system was assessed in seven subjects with profound bilateral adult-onset deafness. The degree of transneuronal atrophy was determined by measuring cell size at three levels of the brain stem auditory pathway (anteroventral cochlear nucleus, medial superior olivary nucleus, and inferior colliculus). Within subjects, the relative degree of cell shrinkage was similar across all levels of the central pathway. Across subjects, the best neuronal preservation was seen in a case of viral labyrinthitis with 1 year of bilateral dearness and a near-normal population of cochlear ganglion cells. Reduction in cell size was greatest in cases of bacterial labyrinthitis or Scheibe degeneration with reduced populations of ganglion cells and longer periods of deafness. At the level of the cochlear nucleus, there was no consistent difference in cell size between the side stimulated by a functioning prosthetic device and the nonstimulated side.

A five-generation family with late-onset progressive hereditary hearing impairment due to cochleosaccular degeneration

Cochleosaccular dysplasia or degeneration (Scheibe degeneration) is considered the most common cause of profound congenital hearing impairment, and accounts for approximately 70% of cases 2 with hereditary deafness. A five-generation family with hereditary hearing impairment associated with cochleosaccular degeneration has recently been identified. The diagnosis of classical Scheibe degeneration was based on histopathological findings in the temporal bones of the proband, a 61-year-old profoundly deaf male. Auditory structures in the brainstem of the proband were also studied. Twenty-two members of the family were contacted for surveys and blood samples. Of these, 6 males and 2 females have hearing impairment. Complete audiological evaluation was done on 12 family members, and prior audiologic records of the proband and affected family members were available for study. Affected family members suffer a mild bilateral high-frequency hearing loss during childhood and adolescence, and progress to moderate-to-profound deafness in the second and third decades of life. The family is suitable for linkage analysis and does not map to previously reported loci harboring autosomal dominant, nonsyndromic hereditary hearing impairment genes. The genetic study of this family will be helpful in identifying the genes which, when mutated, result in Scheibe degeneration.

Spirometry with a Fleisch pneumotachograph: upstream heat exchanger replaces heating requirement

The exact temperature of the head of an unheated Fleisch pneumotachograph (PT) during recording is not known, and variation in its temperature may lead to errors in measuring spirometric indexes. We measured PT head temperature during blows from five normal subjects, recorded by using a PT with and without an upstream heat exchanger to condition the air to the ambient temperature that was set in a climate chamber. Group mean (+/- SD) temperature of a thermocouple (TC) placed inside the PT head was 11.8 +/- 1.9 degrees C with 7 degrees C ambient, 25.4 +/- 1.3 degrees C at 23 degrees C, and was 37.2 +/- 0.3 degrees C at 37 degrees C. The between-subject range of temperature for this TC was 7.5 degrees at 7 degrees C, 5.5 degrees at 23 degrees C, and 1.1 degrees at 37 degrees C. The mean within-subject within-blow variation of temperature for this TC was 10.0 degrees and 3.3 degrees C for ambient of 7 degrees and 23 degrees C, respectively. At the usual ambient temperature in a laboratory, these differences in temperature lead to a 3.6% between-subject bias in recording, and the within-subject differences lead to 2.6% underreading of peak expiratory flow and a 0.5% overreading later in the blow, which makes ATPS-to-BTPS correction erroneous or difficult to perform. With the use of an upstream heat exchanger, the group mean temperature was 8.7 +/- 0.4 degrees, 23.2 +/- 0.2 degrees, and 37.1 +/- 0.2 degrees C at the three ambient temperatures, respectively, and the within-subject within-blow variation was reduced to < 1 degrees C. A heat exchanger placed upstream of the PT satisfactorily conditioned expired air to the ambient temperature and removed the error.

The Peak Flow Working Group: test of portable peak flow meters by explosive decompression

In 1991, 50 new Vitalograph peak flow meters and 27 previously used mini-Wright peak flow meters were tested at three peak flows by use of a calibrator applying explosive decompression. The mini-Wright peak flow meters were also compared with eight new meters. For both makes of meter there was an excellent within-meter and between-meter variation. The accuracy, however, was poor, with a maximal overestimation of true flows of 50 and 70 L.min-1 in the interval from 200 to 400 L.min-1 for the Vitalograph and mini-Wright meters, respectively. The deviation is explained by the physical characteristics of the variable orifice peak flow meters. They have been supplied with equidistant scales, which give non-linear readings.

Preoperative risk factors for surface disease after penetrating keratoplasty

We sought to identify the types of, prevalence of, and predisposing factors for the development of surface keratopathy after penetrating keratoplasty. We reviewed the records of 120 corneal grafts performed over a 15-month period. Twenty patients were excluded from the study. Fifty-three men and 47 women composed the group studied. All transplants were performed by the same surgeon. Retrospective data from patients' records were gathered preoperatively and from postoperative visits at 1 week and at 1, 2, 3, and 4 months. Data included preoperative medical and demographic data, operative time, postoperative medication regimens, assessment of the presence and degree, if present, of punctate epithelial keratopathy (PEK), hurricane keratopathy, macroepithelial defects, microcystic edema, bullous edema, and filamentary keratitis. In addition, information on the donor material was recorded. Surface disease and normal groups were compared to identify risk factors for the occurrence of surface abnormalities. Thirty-three of the patients demonstrated persistent surface abnormalities. Coarse PEK was the most common surface abnormality in the sample studied and was most prominent in the first week after surgery. Postoperative surface keratopathy was not statistically associated with preoperative diagnosis, donor age, death-to-preservation time, preservation-to-surgery time, or donor epithelial status. However, corneal recipients in the group with surface keratopathy were significantly older (mean, 68.7 years) than patients in the group with no surface abnormalities (mean, 52.6 years; Mann-Whitney U test, p < 0.001). Although many factors may contribute to the normal integrity of the corneal surface after keratoplasty, recipient age is of key importance in the development of surface disease.

A cost-effectiveness analysis of typhoid fever vaccines in US military personnel

Typhoid fever has been a problem for military personnel throughout history. A cost-effectiveness analysis of typhoid fever vaccines from the perspective of the US military was performed. Currently 3 vaccine preparations are available in the US: an oral live Type 21A whole cell vaccine; a single-dose parenteral, cell subunit vaccine; and a 2-dose parenteral heat-phenol killed, whole cell vaccine. This analysis assumed all vaccinees were US military personnel. Two pharmacoeconomic models were developed, one for personnel who have not yet been deployed, and the other for personnel who are deployed to an area endemic for typhoid fever. Drug acquisition, administration, adverse effect and lost work costs, as well as the costs associated with typhoid fever, were included in this analysis. Unique military issues, typhoid fever attack rates, vaccine efficacy, and compliance with each vaccine's dosage regimen were included in this analysis. A sensitivity analysis was performed to test the robustness of the models. Typhoid fever immunisation is not cost-effective for US military personnel unless they are considered imminently deployable or are deployed. The most cost-effective vaccine for US military personnel is the single-dose, cell subunit parenteral vaccine.

Pulmonary microsomal metabolism of benzo[a]pyrene following exposure of rats to silica

Because some evidence suggests that there may be an increased incidence of lung cancer in silicosis and because previous studies have shown that exposure of rats to silica alters the pulmonary cytochrome P-450 system, we studied the effects of exposing rats to silica on the lung microsomal metabolism of benzo[a]pyrene (BaP). Rats were exposed to silica by intratracheal administration, lung microsomes were obtained 2 wk later from untreated and silica-treated animals, and the amounts of microsomal tissue and metabolites formed during the in vitro microsomal metabolism of BaP were measured. When the formation of BaP metabolites in equal amounts of lung microsomal tissue from the 2 treatment groups is compared, 3-OH BaP, BaP 4,5-diol, and BaP 9,10-diol are reduced by 45-70%, but the formation of BaP 7,8-diol or the BaP-quinones is not significantly altered following exposure to silica. In fact, the ratio of the BaP diols and BaP quinones, potentially toxic metabolites, to the relatively nontoxic 3-OH BaP produced by equal amounts of lung microsomal tissue is increased more than threefold following exposure of rats to silica. Since exposure of rats to silica leads to increased levels of lung microsomal protein, the amounts of BaP metabolites that could be produced by all microsomal tissue in the lungs were calculated. In silica-treated animals, the calculated total lung production of 3-OH BaP, BaP 4,5-diol, and BaP 9,10-diol tends to be increased by 1.2- to 2.0-fold, but BaP 7,8-diol and the BaP quinones are increased by 3.5-fold. These results demonstrate that exposure of rats to silica may alter the capacity of the lungs to metabolize benzo[a]pyrene, and the greatest effect seems to be enhanced accumulation of BaP 7,8-diol and the BaP quinones.

Peak expiratory flow and the resistance of the mini-wright peak flow meter

The purpose of this study was to examine whether the resistance of the peak flow meter influences its recordings. One hundred and twelve subjects, (healthy nonsmokers and smokers and subjects with lung diseases) performed three or more peak expiratory flow (PEF) manoeuvres through a Fleisch pneumotachograph with and without a mini-Wright peak flow meter added in random order as a resistance in series. The results were as follows. In comparison with a pneumotachograph alone, peak flow measured with an added mini-Wright meter had a smaller within-test variation, defined as the difference between the highest and second highest values of PEF in a series of blows. The mean (SE) variation was 14 (1.3) L.min-1 and 19 (1.5) L.min-1 with and without meter added, respectively. In comparison with the pneumotachograph alone, the addition of the mini-Wright meter caused PEF to be underread, especially at high flows. The difference (PEF with meter minus PEF without meter) = -0.064 (average PEF) -8 L.min-1; R2 = 0.13. The mean difference was -7.8 (1.1) %, and increased numerically for a given PEF, when maximal expiratory flow when 75% forced vital capacity remains to be exhaled (MEF75%FVC) decreased. The reproducibility criteria for repeated measurements of peak flow are more appropriately set at 30 L.min-1 than the commonly used 20 L.min-1, because a within-test variation of less than 30 L.min-1 was achieved in 76% of the subjects without PEF meter inserted and in 88% with meter inserted, with no difference between healthy untrained subjects and patients. The resistance of the peak expiratory flow meter causes less variation in recordings but reduces peak expiratory flow, especially at high values and when the peak is large as compared with the rest of the maximal expiratory flow-volume curve.

Potential effects of correction of inaccuracies of the mini-Wright peak expiratory flow meter on the use of an asthma self-management plan

BACKGROUND

Patient self-management plans for asthma use peak expiratory flow (PEF) meter readings for decisions on adjusting asthma treatment. PEF meters have been shown to be inaccurate and the effect of this inaccuracy on such treatment plans has been determined.

METHODS

PEF measurements were made by 127 severe asthmatic patients at least twice a day for at least two weeks using a mini-Wright meter. The daily variation from "best" PEF and the within day PEF variability were calculated before and after correction for the meter's known inaccuracy. The effect of this data correction on the number of days when trigger points were reached for changing asthma therapy was then determined.

RESULTS

Continuous PEF readings were available from 114 subjects with a median of 157.5 days of data per subject (range 15-489 days). Correction of the PEF data led to the number of days of satisfactory asthma control being reduced in 72% of subjects with just one subject showing an increase in satisfactory control. Data correction reduced the percentage of total days of satisfactory control from 46% to 36% of days, and increased the days requiring more inhaled steroids from 33% to 36%. The days on which a course of oral corticosteroids was required increased from 16% to 23%.

CONCLUSIONS

The accuracy of PEF meters significantly influences the interpretation of currently used asthma self-management plans. Managing asthma with the corrected PEF data would have increased the amount of treatment received by these patients since the severity of the asthma was underestimated by the raw data.