Corrigendum: Limitations in activities of daily living in old age in Germany and the EU - Results from the European Health Interview Survey (EHIS) 2

[This corrects the article on p. 48-56 in vol. 4.].

Glycaemic status and depressive symptoms among adults in Germany: results from the German Health Interview and Examination Survey for Adults (DEGS1)

AIMS

To examine the association between glycaemic status and depressive symptoms in a nationwide sample of the adult population in Germany.

METHODS

We conducted a cross-sectional analysis of data from 6385 participants aged 18-79 years in the nationwide German Health Interview and Examination Survey for Adults 2008-2011 (DEGS1). Glycaemic status was classified as follows: diagnosed diabetes (self-reported diagnosis or receiving antidiabetes medication); undiagnosed diabetes (HbA_1c ≥48 mmol/mol [≥6.5%]); prediabetes (HbA_1c 39-47 mmol/mol [5.7-6.4%]); or normoglycaemia (HbA_1c <39 mmol/mol [<5.7%]). Current depressive symptoms were measured using the Patient Health Questionnaire depression scale (PHQ-9) and defined as elevated depressive symptoms (PHQ-9 score ≥10 points; dichotomous variable) and severity of depressive symptoms (PHQ-9 score, range 0-27 points; continuous variable). Associations of glycaemic status and HbA_1c with both depressive symptoms variables were analysed using multivariable logistic (elevated depressive symptoms) and linear (severity of depressive symptoms) regression models.

RESULTS

Compared with normoglycaemia, diagnosed diabetes, but not prediabetes or undiagnosed diabetes, was associated with elevated depressive symptoms (odds ratio 1.55, 95% CI 1.00-2.41) and severity of depressive symptoms (β coefficient 0.71, 95% CI 0.23-1.19) in models adjusting for sociodemographics and health behaviours. Associations were similar among people with diagnosed diabetes taking and not taking antidiabetes medication. Among people without diagnosed diabetes, no associations between HbA_1c and depressive symptoms were found.

CONCLUSIONS

Diagnosed diabetes, but not prediabetes, undiagnosed diabetes or HbA_1c , was associated with depressive symptoms among adults in Germany. Studies examining psychosocial and biological mechanisms that may potentially explain relationships between diagnosed diabetes and depressive symptoms are needed.

Changes in physical functioning among men and women aged 50-79 years in Germany: an analysis of National Health Interview and Examination Surveys, 1997-1999 and 2008-2011

Background

This study examines changes in physical functioning among adults aged 50-79 years in Germany based on data from two German National Health Interview and Examination Surveys conducted in 1997–1999 (GNHIES98) and 2008–2011 (DEGS1).

Methods

Using cross-sectional data from the two surveys (GNHIES98, n = 2884 and DEGS1, n = 3732), we examined changes in self-reported physical functioning scores (Short Form-36 physical functioning subscale (SF-36 PF)) by sex and age groups (50–64 and 65–79 years). Covariables included educational level, living alone, nine chronic diseases, polypharmacy (≥5 prescribed medicines), body mass index, sports activity, smoking and alcohol consumption. Multimorbidity was defined as ≥2 chronic diseases. Multivariable models were fitted to examine consistency of changes in physical functioning among certain subgroups and to assess changes in mean SF-36 PF scores, adjusting for changes in covariables between surveys.

Results

Mean physical functioning increased among adults aged 50–79 years between surveys in unadjusted analyses, but this change was not as marked among men aged 65–79 years who experienced rising obesity (20.6 to 31.5%, p = 0.004) and diabetes (13.0 to 20.0%, p = 0.014). Prevalence of multimorbidity and polypharmacy use increased among men and women aged 65–79 years. In sex and age specific multivariable analyses, changes in physical functioning over time were consistent across subgroups. Gains in physical functioning were explained by improved education, lower body mass index and improved health-related behaviours (smoking, alcohol consumption, sports activity) in women, but less so among men.

Conclusions

Physical functioning improved in Germany among adults aged 50–79 years. Improvements in the population 65–79 years were less evident among men than women, despite increases in multimorbidity prevalence among both sexes. Changes in health behaviours over time differed between sexes and help explain variations in physical functioning. Targeted health behaviour interventions are indicated from this study.

Electronic supplementary material

The online version of this article (doi:10.1186/s12877-016-0377-0) contains supplementary material, which is available to authorized users.

In vitro evaluation of nutrients that selectively confer a competitive advantage to lactobacilli

An assay was developed that tested the ability of Lactobacillus acidophilus to outcompete a challenge of Escherichia coli in a mixed culture containing different test nutrients. Using this assay, addition of fructo-oligosaccharide to the media allowed L. acidophilus to outcompete a challenge of E. coli, whereas in a mixed culture without the prebiotic the trend was reversed. Growth curves generated for E. coli in a single culture showed that fructo-oligosaccharide did not affect growth, indicating that the carbohydrate was not toxic to E. coli. This indicates that fructo-oligosaccharides may increase the ability of beneficial microbes to outcompete a pathogenic challenge. These results were confirmed using a skin simulant model that incorporates growth of the organisms at an air-surface interface to mimic the vulvar environment. It is possible to use a co-culture assay as an in vitro screening tool to define nutrients that confer a competitive advantage to beneficial flora specific to the female urogenital tract.

Social characteristics of psychological distress in disadvantaged areas of Berlin

PURPOSE

Living in disadvantaged urban areas is associated with poor mental health. The purpose of this study was to assess which social characteristics were associated with psychological distress within a disadvantaged, multi-ethnic neighbourhood of Berlin.

METHODS

The study was conducted in an area of Berlin with the highest rates of unemployment and highest density of migrants. A total of 143 participants aged 18-57 years were included from a random sample. The social characteristics educational level, employment status, marital status, living alone, per-capita income and background of migration were collected. Psychological distress was assessed using the General Health Questionnaire GHQ-28; scores ≥ 5 indicated psychological distress corresponding to psychiatric caseness.

RESULTS

Psychological distress was found in 40.6% (n = 58) of the sample. Psychological distress was associated with younger age (OR = 0.95, 95% CI = 0.92-0.98, p = .004), female gender (OR = 3.51, 95% CI = 1.55-7.92, p = .003) and living alone (OR = 3.88, 95% CI = 1.58-9.52, p = .003), but not with background of migration, low educational level or with unemployment.

CONCLUSIONS

Young age and female gender may predispose for psychological distress in disadvantaged areas. Living alone could be a social indicator of poor mental health within disadvantaged urban areas. The directionality of the association is unclear.

BACKGROUND

of migration, low income and educational level do not seem to be associated with poor mental health within those areas.

[Physical and cognitive capabilities among persons aged 65-79 years in Germany: results of the German Health Interview and Examination Survey for Adults (DEGS1)]

In older age, physical and cognitive capabilities play an important role for independent living. For this reason, the German Health Interview and Examination Survey for Adults (DEGS1) included the Timed Up and Go test (TUG) and a chair-rise test, balance tests, a measurement of hand grip strength and the Digit Symbol Substitution Test (DSST) in order to representatively describe physical and cognitive performance of older people in Germany. Among 1,853 persons 65-79 years of age who came to the study centre more than 90 % participated in the performance tests. The average time needed to complete the TUG and chair-rise tests were 10.7 and 11.8 s, respectively. On average, participants reached 3.9 of a maximum of 5 points in the balance tests (FICSIT4 protocol). Mean maximum grip strength was 32.3 kg. The mean number of correctly assigned symbols in the DSST was 43.8. In all functional capacity areas tested, performance declined with increasing age. There were differences by sex in the chair-rise test, hand grip strength and DSST. The objective measurement of physical and cognitive capabilities in DEGS1 contributes to describe the health status of older people with implications for health promotion and prevention. An English full-text version of this article is available at SpringerLink as supplemental.

[Prevalence of dyslipidemia among adults in Germany: results of the German Health Interview and Examination Survey for Adults (DEGS 1)]

Interview and laboratory data from the first wave of the German health interview and examination survey for adults (DEGS1) from 2008 to 2011 were used to provide current estimates of the prevalence of dyslipidemia which are representative of the population in Germany 18 to 79 years of age. A total of 56.6 % of men and 60.5 % of women 18 to 79 years have elevated serum total cholesterol concentrations in excess of the currently recommended threshold of 190 mg/dL; 17.9 % of men and 20.3 % of women have highly elevated total cholesterol concentrations ≥ 240 mg/dL. A total of 19.3 % of men and 3.6 % of women have high density lipoprotein cholesterol concentrations below 40 mg/dL. The overall prevalence of dyslipidemia (total cholesterol ≥ 190 mg/dL or medical diagnosis of dyslipidemia) is 64.5 % for men and 65.7 % for women. Of these, more than half of both men and women have previously undiagnosed dyslipidemia. Among persons with known dyslipidemia, 30.8% take lipid-lowering medication. Dyslipidemia is widely prevalent among adults in Germany. More in-depth analyses will examine time trends in the prevalence of dyslipidemia in Germany and in an international comparison. An English full-text version of this article is available at SpringerLink as supplemental.

[Primary and secondary prevention of stroke]

Despite considerable advances in acute stroke therapy, stroke prevention remains the most promising approach for reducing the burden of stroke. A healthy lifestyle and the treatment of cardiometabolic risk factors are the cornerstones of both primary and secondary stroke prevention. Due to a proportionately higher risk of bleeding complications, platelet inhibitors are not recommended for primary stroke prevention. Platelet inhibitors are effective in the secondary prevention of stroke with acetyl salicylic acid (ASS) and clopidogrel showing the most consistent data. New oral anticoagulants are slightly more effective than coumarin and significantly reduce the risk of intracranial hemorrhage. They offer the opportunity to bring more patients with atrial fibrillation at risk for stroke into anticoagulation particularly those on ASS therapy. Surgery for patients with asymptomatic carotid artery stenosis should be viewed critically with respect to an only marginal benefit and improvement in medical therapies. Carotid endarterectomy remains the gold standard for patients with symptomatic carotid stenosis because of an increased procedural stroke risk with carotid stenting. Patients with symptomatic intracranial stenosis or cryptogenic stroke and a patent foramen ovale should receive only medical treatment.

Sociodemographic differences in return to work after stroke: the South London Stroke Register (SLSR)

BACKGROUND

Loss of employment contributes significantly to the burden of stroke on individuals and society. There is limited information on factors influencing return to work after stroke.

OBJECTIVES

To investigate the frequency and determinants of return to paid work after stroke in a multi-ethnic urban population.

METHODS

Patterns of return to work were examined among people with first ever stroke registered in the population based South London Stroke Register. Employment status and functional outcome (Barthel Index (BI), Frenchay Activity Index (FAI)) were assessed 1 year after stroke. Associations between baseline characteristics and return to paid work were analysed by multivariable logistic regression analysis.

RESULTS

Among 2874 patients with first ever strokes in 1995-2004, 400 (15%) were working before the stroke. At 1 year, 94 (35%) of 266 survivors had returned to paid work. Black ethnicity (OR 0.41; 95% CI 0.19 to 0.88), female sex (0.43; 0.21 to 0.91), older age (p<0.001), diabetes (0.25; 0.08 to 0.79) and dependence (BI < or = 19) in the acute phase (0.24; 0.11 to 0.49) were independently associated with lower odds of return to work in multivariable analysis. Better functional outcome at 1 year was associated with return to paid work (p<0.001) but 53% of 161 independent (BI > 19) and 39% of 96 very active (FAI > 30/45) individuals had not resumed work.

CONCLUSIONS

There were important sociodemographic differences in return to work after stroke that were independent of clinical and service use variables included in the analysis. A large proportion of patients did not resume work despite excellent functional outcome.

Oral transmucosal fentanyl citrate in the management of breakthrough pain in cancer: an open, multicentre, dose-titration and long-term use study

Sixty-six patients with cancer-related pain entered an open multicentre study to examine the safety and efficacy of oral transmucosal fentanyl citrate (OTFC) in the treatment of breakthrough pain. Patients were eligible for the study if they were stabilized on a long-acting opioid but were experiencing up to four episodes of breakthrough pain a day and achieving at least partial relief from breakthrough pain using conventional medication (normal release oral morphine in the majority of patients). The efficacy of the conventional medication was documented in a run-in phase and patients then changed to OTFC. All patients were treated initially with a 200 mcg unit of OTFC and the dose was increased if necessary to a level that produced relief of breakthrough pain without troublesome adverse effects. Fifty-eight patients completed the run-in phase using their usual medication and entered the dose titration phase with OTFC and 57 patients received at least one dose of OTFC. Forty-two patients (72%) found a successful dose of OTFC. The primary outcome measures were the Summed Pain Intensity Differences (SPID) and Total Pain Relief (TOTPAR) scores at 60 min. There was a significant difference in both measures in favour of OTFC compared with conventional medication in these patients. Twenty-eight of the 42 patients (67%) preferred OTFC to their usual medication. The most common adverse effects attributed to OTFC were nausea, stomatitis, vomiting and dizziness but there were no unpredicted or severe problems. Thirty-seven patients continued into the long-term study and 12 of these completed six months treatment. Most drop-outs in this phase were associated with progression of the underlying disease. No patient stopped using OTFC because of dissatisfaction with the drug. OTFC appears to be a safe and effective treatment for breakthrough pain in cancer patients and may have advantages over currently available opioid formulations.

Long-term safety of oral transmucosal fentanyl citrate for breakthrough cancer pain

This open-label study evaluated the long-term safety and tolerability of oral transmucosal fentanyl citrate (OTFC) in ambulatory cancer patients with breakthrough pain undergoing cancer care at 32 university- or community-based practices. Patients had participated in a previous short-term titration trial of OTFC, were experiencing at least one episode per day of breakthrough pain, and had achieved relief of their breakthrough pain with an opioid. Patients received OTFC units at a starting dosage strength determined in the short-term trial (200-1600 microg). Outcome measures included number of successfully treated breakthrough pains, global satisfaction rating (0 = poor through 4 = excellent), and side effects. In total, 41,766 units of OTFC were used to treat 38,595 episodes of breakthrough pain in 155 patients. Number of treatment days ranged from 1 to 423 (mean, 91 days). Patients averaged 2.9 breakthrough pain episodes per day. About 92% of episodes were successfully treated with OTFC and there was no trend toward decreased effectiveness over time. Most patients (61%) did not require dose escalation during treatment. Global satisfaction ratings were consistently above 3, indicating very good to excellent relief. Common adverse events associated with OTFC were somnolence (9%), constipation (8%), nausea (8%), dizziness (8%), and vomiting (5%). Six patients (4%) discontinued therapy due to an OTFC-related adverse event. There were no reports of abuse and no concerns about the safety of the drug raised by patients or families. OTFC was used safely and effectively during long-term treatment of breakthrough pain in cancer patients at home.

A molecular link between stem cell regulation and floral patterning in Arabidopsis

The homeotic gene AGAMOUS (AG) has dual roles in specifying organ fate and limiting stem cell proliferation in Arabidopsis flowers. We show that the floral identity protein LEAFY (LFY), a transcription factor expressed throughout the flower, cooperates with the homeodomain protein WUSCHEL (WUS) to activate AG in the center of flowers. WUS was previously identified because of its role in maintaining stem cell populations in both shoot and floral meristems. The unsuspected additional role of WUS in regulating floral homeotic gene expression supports the hypothesis that floral patterning uses a general meristem patterning system that was present before flowers evolved. We also show that AG represses WUS at later stages of floral development, thus creating a negative feedback loop that is required for the determinate growth of floral meristems.

Breakthrough cancer pain: a randomized trial comparing oral transmucosal fentanyl citrate (OTFC) and morphine sulfate immediate release (MSIR)

Oral transmucosal fentanyl citrate (OTFC); Actiq) is a drug delivery formulation used for management of breakthrough cancer pain. Previous studies with open-label comparisons indicated OTFC was more effective than patients' usual opioid for breakthrough pain. The objective of this study was to compare OTFC and morphine sulfate immediate release (MSIR) for management of breakthrough pain in patients receiving a fixed scheduled opioid regimen. This double-blind, double-dummy, randomized, multiple crossover study was conducted at 19 US university- and community-based hospitals and clinics and comprised 134 adult ambulatory cancer patients. Patients were receiving a fixed scheduled opioid regimen equivalent to 60-1000 mg/day oral morphine or 50-300 microg/h transdermal fentanyl, were using a 'successful' MSIR dose (15-60 mg) as defined by entry criteria, and were experiencing 1-4 episodes of breakthrough pain per day. In open-label fashion, OTFC was titrated such that a single unit (200-1600 microg) provided adequate pain relief with acceptable side effects. Successfully titrated patients entered the double-blind phase of the study and received ten prenumbered sets of randomized capsules and oral transmucosal units. Five sets were the successful OTFC dose paired with placebo capsules, and five sets were placebo OTFC paired with capsules containing the successful MSIR dose. Patients took one set of study medication for each episode of target breakthrough pain. Pain intensity (PI), pain relief (PR) and global performance of medication (GP) scores were recorded. Pain intensity differences (PID) were calculated and 15-min PID was the primary efficacy variable. Adverse events were recorded. Sixty-nine percent of patients (93/134) found a successful dose of OTFC. OTFC yielded outcomes (PI, PID, and PR) at all time points that were significantly better than MSIR. GP also favored OTFC and more patients opted to continue with OTFC than MSIR following the study. Somnolence, nausea, constipation, and dizziness were the most common drug-associated side effects. In conclusion, OTFC was more effective than MSIR in treating breakthrough cancer pain.

Interaction between electron transport at the plasma membrane and nitrate uptake by maize (Zea mays L.) roots

In the present study nitrate uptake by maize (Zea mays L.) roots was investigated in the presence or absence of ferricyanide (hexacyanoferrate III) or dicumarol. Nitrate uptake caused an alkalization of the medium. Nitrate uptake of intact maize seedlings was inhibited by ferricyanide while the effect of dicumarol was not very pronounced. Nitrite was not detected in the incubation medium, neither with dicumarol-treated nor with control plants after application of 100 microM nitrate to the incubation solution. In a second set of experiments interactions between nitrate and ferricyanide were investigated in vivo and in vitro. Nitrate (1 or 3 mM) did neither influence ferricyanide reductase activity of intact maize roots nor NADH-ferricyanide oxidoreductase activity of isolated plasma membranes. Nitrate reductase activity of plasma-membrane-enriched fractions was slightly stimulated by 25 microM dicumarol but was not altered by 100 microM dicumarol, while NADH-ferricyanide oxidoreductase activity was inhibited in the presence of dicumarol. These data suggest that plasma-membrane-bound standard-ferricyanide reductase and nitrate reductase activities of maize roots may be different. A possible regulation of nitrate uptake by plasmalemma redox activity, as proposed by other groups, is discussed.

The relative potency of oral transmucosal fentanyl citrate compared with intravenous morphine in the treatment of moderate to severe postoperative pain

Pharmacokinetic studies have shown that oral transmucosal absorption of fentanyl is relatively rapid compared with gastrointestinal absorption, and it results in increased bioavailability. We designed this study to establish the relative potency of oral transmucosal fentanyl citrate (OTFC) compared with i.v. morphine in 133 postoperative patients. The morning after surgery, patients randomly received one dose of either OTFC (200 or 800 microg) and a placebo i.v. injection or i.v. morphine (2 or 10 mg) and an oral transmucosal placebo unit. Pain intensity, pain relief, time to meaningful pain relief, and time to remedication were recorded. Median time to onset of relief was approximately 5 min for all groups. Over the first hour, little difference among treatment groups was seen for pain intensity and pain relief. By 2 h after study drug administration, 800 microg of OTFC and 10 mg of i.v. morphine generally produced similar analgesia, which was better than the smaller doses. Duration of analgesia with the larger doses (800 microg of OTFC and 10 mg of morphine) was similar and longer that produced by the smaller doses. The larger doses of OTFC and morphine produced better and more sustained analgesia than 200 microg of OTFC or 2 mg of morphine.

IMPLICATIONS

The relative potency of oral transmucosal fentanyl citrate (OTFC) to i.v. morphine was 8-14:1. In this postoperative setting, OTFC produced rapid pain relief similar to that produced by i.v. morphine. The larger doses of OTFC (800 microg) and morphine (10 mg) produced better and more sustained analgesia than 200 microg of OTFC or 2 mg of morphine.

Activation of a floral homeotic gene in Arabidopsis

The patterned expression of floral homeotic genes in Arabidopsis depends on the earlier action of meristem-identity genes such as LEAFY, which encodes a transcription factor that determines whether a meristem will generate flowers instead of leaves and shoots. The LEAFY protein, which is expressed throughout the flower, participates in the activation of homeotic genes, which are expressed in specific regions of the flower. Analysis of a LEAFY-responsive enhancer in the homeotic gene AGAMOUS indicates that direct interaction of LEAFY with this enhancer is required for its activity in plants. Thus, LEAFY is a direct upstream regulator of floral homeotic genes.

Oral transmucosal fentanyl citrate (OTFC) for the treatment of breakthrough pain in cancer patients: a controlled dose titration study

Oral transmucosal fentanyl citrate (OTFC) is a novel opioid formulation in which the potent synthetic mu-agonist fentanyl is embedded in a sweetened matrix that is dissolved in the mouth. It is undergoing investigation as a treatment for cancer-related breakthrough pain, a prevalent phenomenon defined as a transitory flare of moderate to severe pain that interrupts otherwise controlled persistent pain. There have been no controlled trials of other treatments for this condition. To evaluate the safety and efficacy of ascending doses of OTFC, a novel controlled dose titration methodology was developed that applied blinding and randomization procedures to the evaluation of recurrent pains in the home environment. The study was a multicenter, randomized, double-blind dose titration study in ambulatory cancer patients. The sample comprised adult patients receiving a scheduled oral opioid regimen equivalent to 60-1000 mg oral morphine per day, who were experiencing at least one episode per day of breakthrough pain and had achieved at least partial relief of this pain by use of an oral opioid rescue dose. After collection of 2 days of baseline data concerning the efficacy of the usual rescue drug, patients were randomly treated with either 200 or 400 microg OTFC unit doses in double-blind fashion. Up to two breakthrough pains each day could be treated with up to four OTFC unit doses per pain. OTFC in unit doses containing 200, 400, 600, 800, 1200 or 1600 microg of fentanyl citrate were available for the study. The unit dose was titrated upward in steps until the patient had 2 consecutive days on which breakthrough pain could be treated with the single unit dose, titration was ineffective at a 1600 microg unit dose, or 20 days elapsed. To maintain the double-blind, orders to titrate up were ignored one-third of the time according to a pre-defined randomization schedule accessible only to an unblinded study pharmacist. Main outcome measures included, numeric or categorical measures of pain intensity, pain relief, and global assessment of drug performance. Dose response relationships were found suggesting that the methodology was sensitive to opioid effects. Seventy-four percent of patients were successfully titrated. There was no relationship between the total daily dose of the fixed schedule opioid regimen and the dose of OTFC required to manage the breakthrough pain. Although the study was not designed to provide a definitive comparison between OTFC and the usual rescue drug, exploratory analyses found that OTFC provided significantly greater analgesic effect at 15, 30 and 60 min, and a more rapid onset of effect, than the usual rescue drug. Adverse effects of the OTFC were typically opioid-related, specifically somnolence, nausea and dizziness. Very few adverse events were severe or serious. This study demonstrated the feasibility of controlled trial methodology in studies of breakthrough pain. OTFC appears to be a safe and effective therapy for breakthrough pain, and dose titration can usually identify a unit dose capable of providing adequate analgesia. If the lack of a relationship between the effective OTFC dose and fixed schedule opioid regimen is confirmed, dose titration may be needed in the clinical use of this formulation. Further investigation of OTFC as a specific treatment for breakthrough pain is warranted.

A genetic framework for floral patterning

The initial steps of flower development involve two classes of consecutively acting regulatory genes. Meristem-identity genes, which act early to control the initiation of flowers, are expressed throughout the incipient floral primordium. Homeotic genes, which act later to specify the identity of individual floral organs, are expressed in distinct domains within the flower. The link between the two classes of genes has remained unknown so far. Here we show that the meristem-identity gene LEAFY has a role in controlling homeotic genes that is separable from its role in specifying floral fate. On the basis of our observation that LEAFY activates different homeotic genes through distinct mechanisms, we propose a genetic framework for the control of floral patterning.

Dose-titration, multicenter study of oral transmucosal fentanyl citrate for the treatment of breakthrough pain in cancer patients using transdermal fentanyl for persistent pain

PURPOSE

Supplemental, "as-needed," administration of an opioid is a common approach to the problem of breakthrough pain in cancer patients. Oral transmucosal fentanyl citrate (OTFC) is undergoing investigation as a new treatment for breakthrough pain. The primary purpose of the study was to demonstrate that a single-unit dose of OTFC can safely and effectively treat breakthrough pain. A secondary goal was to determine appropriate dosing guidelines.

PATIENTS AND METHODS

This was a multicenter, randomized, double-blind, dose-titration study in 62 adult cancer patients using transdermal fentanyl for persistent pain. Consenting patients provided 2 days of baseline data to evaluate the performance of their usual breakthrough pain medication. Patients then randomly received 200 microg or 400 microg OTFC in double-blind fashion. (Patients were always assigned, rather than randomized, to 200 microg if 400 microg represented > 20% of around-the-clock medication.) Pain intensity (PI), pain relief (PR), and global satisfaction scores were recorded. OTFC was then titrated until the patient received adequate PR for each episode using one OTFC unit. Orders to titrate up were ignored one third of the time to improve the blind. Two days of baseline data were compared with 2 days of OTFC data after titration identified an effective dose of OTFC.

RESULTS

Most patients (76%) found a safe and effective dose of OTFC. There was no meaningful relationship between the around-the-clock opioid regimen and the effective dose of OTFC. In open-label comparisons, OTFC produced a faster onset of relief and a greater degree of PR than patients' usual breakthrough medication. Somnolence, nausea, and dizziness were the most common side effects associated with OTFC.

CONCLUSION

Most patients find a single OTFC dosage that adequately treats breakthrough pain. The optimal dose is found by titration and is not predicted by around-the-clock dose of opioids.

Characterization of breakthrough pain by hospice patients and their caregivers

This study sought to characterize the nature of breakthrough pain experienced by 22 hospice patients and to assess the perceptions of their respective caregivers. Questionnaires were administered by trained hospice nurses to determine key elements of episodic pains in this home-based terminally ill population. Eighty-six percent of the patients surveyed experienced breakthrough pain, with an average of 2.9 episodes per 24-hr period and a mean pain intensity of 7 on a ten-point scale, compared with average baseline pain scores of 3.6 (daytime) and 2.6 (nighttime). Breakthrough pain episodes lasted 52 min on average, with a range of 1-240 min. The range of time to relief of breakthrough pains was 5-60 min, with a mean of 30 min. Caregivers' perceptions of the pain intensities, duration, amount of relief, and time to relief were much more likely to be inaccurate, and were usually underestimates. This study suggests that breakthrough pain is common in the hospice setting and that there is poor concordance between patients' self-reports and their caregivers' perceptions of these pains. It is concluded that the pharmacodynamics of currently available oral analgesics are not well-suited for breakthrough pain and that better communication between patients and caregivers may lead to more optimal pain management.

Dose proportionality and pharmacokinetics of oral transmucosal fentanyl citrate

BACKGROUND

The pharmacokinetics of a single dose (15 microg/kg) of oral transmucosal fentanyl citrate (OTFC) have been characterized. A range of doses may eventually be used in clinical practice. The goal of this study was to determine if the pharmacokinetics of OTFC are dose proportional for doses ranging from 200 to 1,600 microg.

METHODS

Twelve healthy male volunteers were studied on four different occasions, receiving 200, 400, 800, and 1,600 microg OTFC in a double-blind, randomized protocol. Venous blood samples were collected at selected times during and after dosing for a 24-h period and assayed for fentanyl using a radioimmunoassay. Maximum concentration, time to maximum concentration, area under the curve, and elimination half-life were determined for each dose administered. In addition, respiratory rate, need for verbal prompting to breathe, and supplemental oxygen requirements were noted.

RESULTS

Mean fentanyl concentration time curves were similarly shaped with increasing doses. Both peak concentrations and area under the curve increased linearly with an increase in dose, whereas time to reach peak serum concentrations did not vary significantly between doses. Except for the 200-microg dose, the apparent elimination half-life remained relatively constant (358-386 min). The incidence of low respiratory rate, supplemental oxygen requirement, and number of breathing prompts significantly increased with increasing doses.

CONCLUSIONS

Oral transmucosal fentanyl citrate exhibits dose-proportional pharmacokinetics over the dose range of 200-1,600 microg.

Magnetohydrodynamic Aggregation of Cholesterol and Polystyrene Latex Suspensions

The aggregation state of flowing (0.49 m s-1 linear velocity) colloidal dispersions of polystyrene latex microspheres (certified particle diameter of 156 &plusmn; 6 nm; measured diameter, 156 &plusmn; 3 nm at pH 5.3 in 50 mM NaCl) in NaCl solution and cholesterol (measured diameter, 533 &plusmn; 9 nm at pH 5.3), stabilized in NaCl solution by sodium taurodeoxycholate, was studied using photon correlation spectroscopy. For cholesterol suspensions having electrolyte concentrations close to the critical coagulation concentration (50 mM NaCl), pronounced aggregation was observed after 15 to 30 min of recirculation in the presence of an orthogonally applied magnetic field (2.0, 1.0 and 0.15 T). In all experiments with cholesterol, aggregation was followed by a period of deaggregation, after which aggregation again occurred. Comparable effects were not observed when cholesterol suspensions were recirculated in the absence of the magnetic field or when the suspensions were exposed to an equivalent magnetic field in the absence of flow. For cholesterol suspensions, the increase in particle size was most pronounced at 0.15 and 1.0 T rather than at 2.0 T. Aggregation effects were also observed when suspensions of polystyrene latex in 200 mM NaCl were made to flow through a 1.0-T field. In both systems, the magnetic aggregation does not appear to involve direct interaction between the field and the solid phase, but is interpreted in terms of orthokinetic effects involving magnetohydrodynamic changes in the flow profile resulting from the presence of the transverse field.

Design and performance of a new continuous-flow sample-introduction system for flame infrared-emission spectrometry: Applications in process analysis, flow injection analysis, and ion-exchange high-performance liquid chromatography

A new sample introduction system for the analysis of continuously flowing liquid streams by flame infrared-emission (FIRE) spectrometry has been developed. The system uses a specially designed purge cell to strip dissolved CO(2) from solution into a hydrogen gas stream that serves as the fuel for a hydrogen/air flame. Vibrationally excited CO(2) molecules present in the flame are monitored with a simple infrared filter (4.4 mum) photometer. The new system can be used to introduce analytes as a continuous liquid stream (process analysis mode) or on a discrete basis by sample injection (flow injection analysis mode). The key to the success of the method is the new purge-cell design. The small internal volume of the cell minimizes problems associated with purge-cell clean-out and produces sharp, reproducible signals. Spent analytical solution is continuously drained from the cell, making cell disconnection and cleaning between samples unnecessary. Under the conditions employed in this study, samples could be analyzed at a maximum rate of approximately 60/h. The new sample introduction system was successfully tested in both a process analysis- and a flow injection analysis mode for the determination of total inorganic carbon in Waco tap water. For the first time, flame infrared-emission spectrometry was successfully extended to non-volatile organic compounds by using chemical pretreatment with peroxydisulfate in the presence of silver ion to convert the analytes into dissolved carbon dioxide, prior to purging and detection by the FIRE radiometer. A test of the peroxydisulfate/Ag(+) reaction using six organic acids and five sugars indicated that all 11 compounds were oxidized to nearly the same extent. Finally, the new sample introduction system was used in conjunction with a simple filter FIRE radiometer as a detection system in ion-exchange high-performance liquid chromatography. Ion-exchange chromatograms are shown for two aqueous mixtures, one containing six organic acids and the second containing six mono-, di-, and trisaccharides.

Two-dimensional multiple entrance-slit vidicon spectrometer for simultaneous multielement analysis

A new type of wavelength dispersion system for use with a multichannel detector has been developed for simultaneous multielement analysis. The system employs a monochromator with fixed grating position, and incident angle varied by horizontal displacement of the entrance slits. The overlapping spectral windows which result can be arranged to produce a composite spectrum having minimal interference from emissions by other sample constituents. Entrance slits may also be displaced vertically to create a two-dimensional system in which spectra are stacked one above the other and scanned by use of a multi-raster scanning pattern. A number of optical and performance characteristics of the system are evaluated in both the one- and two-dimensional modes, and the system is applied to the determination of Ca, Na and K in blood serum and to the determination of the exchangeable cations Ca, Na, Li and K in clay. The advantages of this system for simultaneous multielement analysis are discussed.

Ventilatory effects of single, high-dose triazolam in awake human subjects

The respiratory-depressant effect of the benzodiazepine-derived hypnotic triazolam was investigated with a single oral dose at two and three times the usual dosage in 62 awake normal subjects. A randomized, double-blind protocol compared the following groups: (1) placebo, (2) triazolam, 1.0 mg, (3) triazolam, 1.5 mg, and (4) morphine, 0.15 mg/kg. Differences between predrug and postdrug administration were compared. Minute ventilation (Ve), end-tidal PCO2, and the ventilatory response to CO2 (Ve/PCO2) were preserved with both 1.0 mg and 1.5 mg triazolam compared with placebo. Triazolam caused an increase in breathing frequency (+21% to 50%; p less than 0.05) as a result of a shortening of inspiratory time. Triazolam was associated with a higher Ve corrected for CO2 production and Ve/PCO2 compared with morphine. We concluded that a single dose of triazolam at two and three times the usual level does not cause respiratory depression in awake, normal subjects but does alter respiratory cycle timing causing an increase in breathing frequency.

Carotid body hypercapnia does not elicit ventilatory acclimatization in goats

The carotid body (CB) perfusion model utilizes surgical vascular ligations to allow isolated blood supply to a single in situ CB in awake goats. The contralateral CB was excised. By use of an extracorporeal pump-oxygenator system the blood gas composition perfusing the CB can be controlled independently from that of the systemic arterial system including the brain. Using this model we compared the responses of systemically normoxic goats to CB hypercapnia and CB hypoxia. In 6 goats CB stimulation with hypercapnic-normoxic blood (mean PcbCO2 = 78 Torr, mean PcbO2 congruent to 100 Torr) produced acute hyperventilation (mean decrease in PaCO2 of 5.2 Torr, P less than 0.05) which remained constant over the 4-h perfusion period. Lack of a progressively increasing hyperventilation indicates that ventilatory acclimatization did not occur with hypercapnic CB perfusion. Hypoxic-normocapnic CB stimulation (mean PcbO2 = 40 Torr, mean PcbCO2 = 39 Torr) produced an acute mean decrease in PaCO2 of 5.5 Torr (P less than 0.05) in 6 additional goats. In contrast to CB hypercapnia, the acute hyperventilation induced by CB hypoxia was followed by a progressive time-dependent additional mean decrease in PaCO2 of 5.6 Torr (P less than 0.05) over a 4-h period (ventilatory acclimatization). These data are compatible with the concept of separate receptor mechanisms for hypercapnia and hypoxia in the CB and suggest that the early phase of ventilatory acclimatization to hypoxia in goats may result from a time-dependent increase in CB afferent output.

Ventilatory acclimatization to hypoxia is not dependent on cerebral hypocapnic alkalosis

We previously demonstrated that, in awake goats, 6 h of hypoxic carotid body perfusion during systemic normoxia produced time-dependent hyperventilation that is typical of ventilatory acclimatization to hypoxia (VAH). The hypocapnic alkalosis that occurred could have produced VAH by inducing cerebral vasoconstriction and brain lactic acidosis even though systemic arterial normoxia was maintained. In the present study we tested the hypothesis that hypocapnic alkalosis is a necessary component of VAH. Goats were prepared so that one carotid body could be perfused, from an extracorporeal circuit, with blood in which gas tensions could be controlled independently from the blood perfusing the systemic arterial system, including the brain. Using this preparation we carried out 4 h of hypoxic carotid body perfusion while maintaining systemic arterial (and brain) normoxia in awake goats. Expired minute ventilation (VE) was measured while CO2 was added to inspired air to maintain normocapnia. Carotid body PCO2 and PO2 were maintained near 40 Torr during the 4-h carotid body perfusion. Control mean VE was 8.65 +/- 0.48 l/min (mean +/- SE). With acute carotid body hypoxia (30 min) VE increased to 21.73 +/- 2.02 l/min (P less than 0.05); over the ensuing 3.5 h of carotid body hypoxia, VE progressively increased to 39.14 +/- 4.14 l/min (P less than 0.05). These data indicate that neither cerebral hypoxia nor hypocapnic alkalosis are required to produce VAH. After termination of the 4-h carotid body stimulation, hyperventilation was not maintained in these studies, i.e., there was no deacclimatization. This suggests that acclimatization and deacclimatization are produced by different mechanisms.

Transmural coronary vasodilator reserve and flow distribution in unanesthetized calves sojourning at 3500 m

Regional myocardial blood flow (MBF; 15-micron-diam radionuclide-labeled microspheres) was studied in six unanesthetized calves sojourning at 3500 m (PB = 500 mm Hg) for 53 +/- 2 days. These high-altitude (HA)-exposed calves were studied during chronic hypoxemia (PaO2 = 48 +/- 1 mm Hg), maximal coronary vasodilation, and during acute normoxemia (PaO2 = 91 +/- 1 mm Hg). Nine calves born and raised at sea level (SL) were also studied at matched PaO2 during chronic normoxemia, maximal coronary vasodilation, and acute hypoxemia to serve as control. Marked pulmonary hypertension and right ventricular (RV) hypertrophy were present in HA calves. Left ventricular (LV) MBF of HA calves during chronic hypoxemia (1.05 +/- 0.11 ml X min-1 X g-1) was similar to that of normoxemic SL calves (1.11 +/- 0.06 ml X min-1 X g-1) but MBF in their hypertrophied RV (1.65 +/- 0.21 ml X min-1 X g-1) exceeded that in normoxemic SL calves (0.47 +/- 0.06 ml X min-1 X g-1). More interesting was the finding that RV and LV MBF of HA calves did not change between chronic hypoxemia and acute normoxemia. By contrast, acute hypoxemia of a similar degree caused a dramatic increase in RV as well as LV MBF of SL calves. Minimal LV coronary vascular resistance was similar in the two groups of calves. This meant that functional cross-sectional area of LV coronary vascular bed was not altered in response to sojourn at HA. Minimal RV coronary vascular resistance of HA calves was also not different from that of SL calves. This means that functional cross-sectional area of the RV coronary vascular bed in HA calves increased proportionately with the increase in their RV mass.

Ventilatory acclimatization to hypoxia is not dependent on arterial hypoxemia

Goats were prepared so that one carotid body (CB) could be perfused with blood in which the gas tensions could be controlled independently from the blood perfusing the systemic arterial system, including the brain. Since one CB is functionally adequate, the nonperfused CB was excised. To determine whether systemic arterial hypoxemia is necessary for ventilatory acclimatization to hypoxia (VAH), the CB was perfused with hypoxic normocapnic blood for 6 h [means +/- SE: partial pressure of carotid body O2 (PcbO2), 40.6 +/- 0.3 Torr; partial pressure of carotid body CO2 (PcbCO2), 38.8 +/- 0.2 Torr] while the awake goat breathed room air to maintain systemic arterial normoxia. In control periods before and after CB hypoxia the CB was perfused with hyperoxic normocapnic blood. Changes in arterial PCO2 (PaCO2) were used as an index of changes in ventilation. Acute hypoxia (0.5 h of hypoxic perfusion) resulted in hyperventilation sufficient to reduce average PaCO2 by 6.7 Torr from control (P less than 0.05). Over the subsequent 5.5 h of hypoxic perfusion, average PaCO2 decreased further, reaching 4.8 Torr below that observed acutely (P less than 0.05). Acute CB hyperoxic perfusion (20 min) following 6 h of hypoxia resulted in only partial restoration of PaCO2 toward control values; PaCO2 remained 7.9 Torr below control (P less than 0.05). The progressive hyperventilation that occurred during and after 6 h of CB hypoxia with concomitant systemic normoxia is similar to that occurring with total body hypoxia. We conclude that systemic (and probably brain) hypoxia is not a necessary requisite for VAH.

Interaction between cold and altitude exposure on pulmonary circulation of cattle

Hereford calves were exposed in a temperature-controlled hypobaric chamber to environmental temperatures of -2 to 1 degree C (cold) at altitudes of 1,524 m (resident altitude) and 3,048 m 1) to characterize the effects of cold exposure on the pulmonary circulation; 2) to examine the role of cold-induced hypoventilation on the pulmonary circulation; and 3) to examine the interaction between cold and hypoxia on the pulmonary circulation. Cold exposure produced a significant increase in pulmonary arterial pressure (Ppa), pulmonary arterial wedge pressure (Ppaw), and pulmonary vascular resistance (PVR) at both 1,524 and 3,048 m without affecting cardiac output. Concomitantly, cold exposure caused reductions in minute ventilation, respiratory rate, end-tidal O2 tension (PETO2), and arterial O2 tension (PaO2). Tidal volume, end-tidal CO2 tension, and arterial CO2 tension increased. Neither arterial pH nor O2 consumption changed during cold exposure. These results indicated that both pulmonary arterial and venous vasoconstriction were responsible for the pulmonary hypertension associated with cold exposure. Acute exposure to 3,048 m during cold exposure produced increases in Ppa and PVR that were similar to those elicited by cold exposure at 1,524. It was concluded that altitude exposure neither attenuated nor potentiated the effect of cold exposure on the pulmonary circulation; rather, altitude and cold exposure interacted additively. O2 administered during cold exposure to restore PETO2 and PaO2 to control values partially restored Ppa and PVR to control values. This suggested that a portion of the pulmonary hypertension associated with cold exposure was due to hypoxic pulmonary vasoconstriction elicited by the cold-induced alveolar hypoventilation.

O2 transport in ponies during treadmill exercise

We assessed cardiovascular variables and blood O2 contents in order to characterize O2 transport in ponies during treadmill exercise. In normal ponies at 1.8, 3, and 6 mph, respectively, cardiac output (Qc) increased from 12 l/min at rest to maximum levels of 19.7, 28.7, and 39.9 l/min between 30 and 60 s. Qc then decreased to steady-state levels of 18.2, 24.6, and 32.7 l/min by 4 min. Heart rate (HR) showed a similar biphasic response in the 1st min of exercise. Systolic and diastolic arterial blood pressure (BP) decreased at the onset of exercise by 20-25 Torr (P less than 0.05) and then increased to a steady-state by 60 s. Mean right ventricular pressures (MRVBP) increased from approximately 9.7 Torr at rest to 15.9 (1.8 mph), 15.2 (3 mph), and 23.6 Torr (6 mph) by 1 min and then decreased throughout the remainder of the 8 min of exercise (P less than 0.05). At 3 and 6 mph, respectively, arterial O2 content (CaO2) increased from 11.6 vol% at rest to 12.7 and 15.0 vol% by 45 s and 13.1 and 16.6 vol% by 7 min. At 7 min of 9.3 mph exercise, it increased to 20.34 vol%. Hemoglobin (Hb) at 3 mph increased from 9.6 g/100 ml at rest to 10.5 g/100 ml by 45 s and 11.7 g/100 ml by 7 min. At 6 mph, Hb increased to 12 g/100 ml at 45 s and 13.0 g/100 ml by 7 min of exercise. These data demonstrate that the rapid, work load-dependent increase in CaO2 represents an important mechanism to increase O2 transport in exercising ponies.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiodynamic variables and ventilation during treadmill exercise in ponies

We assessed the relationship of ventilation (VE) to cardiodynamic variables and CO2 transport in seven normal ponies during treadmill exercise. At 1.8, 3, and 6 mph, respectively, VE increased from 15 l/min at rest to 43, 51, and 86 l/min by 1 min and 48, 68, and 125 l/min by 8 min. In three ponies at the same work loads, cardiac output (Qc) increased from approximately 12 l/min at rest to 19.7, 28.1, and 40.3 l/min between 30-60 s (P less than 0.05) and then decreased by about 20% to a steady state by 3-4 min. Heart rate (HR) shows a similar biphasic response during exercise. Mean right ventricular pressure (MRVBP) increased from 9.9 to 15.9 Torr at 1.8 mph, 15.2 Torr at 3 mph, and 23.5 Torr at 6 mph by 1 min (P less than 0.05) and then decreased to 11.8, 12.2, and 15.8 Torr by 8 min of the three respective work intensities. At all work loads, VE increased proportionately faster than these cardiovascular variables in the 1st min. For example, at 6 mph VE increased 470%, whereas Qc and HR increased only 230%. Thereafter, VE generally continued to increase at 3 and 6 mph, whereas MRVBP, Qc, and HR decreased. Therefore, the basic assumption of a cardiodynamic hyperpnea that VE and Qc are equivalently coupled at the exercise onset is rejected for this species. Mixed venous CO2 content (C-vCO2) at 3 and 6 mph, respectively, decreased slightly from 61.6 and 62.3 vol% at rest to 59.6 and 61.9 vol% by 45 s and then increased to 63.3 and 63.5 vol% by 7 min.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of unilateral carotid body excision on ventilatory control in goats

The purpose of this study was to determine whether or not unilateral carotid body excision (UCBE) alters normal respiratory control in awake and otherwise intact goats. We measured resting VE and blood gas tensions and pH and ventilatory responses (VR) to NaCN, dopamine and Doxapram in awake goats before and after UCBE. Resting ventilation, blood gas tensions and pH, and the VR to the above stimuli were not altered by UCBE. During exposure to hypoxia in a hypobaric chamber (PB = 450 torr), PaCO2 decreased in UCBE goats over the first hour, indicating acute hypoxic hyperventilation. During the subsequent 8 h, PaCO2 decreased an additional 5-6 torr, suggesting ventilatory acclimatization to chronic hypoxia (VACH). The response was similar to that observed in intact goats. Acute normoxia following 6 and 8 hr did not completely alleviate the hypocapnia of prolonged hypoxia, further suggesting VACH. We conclude that sufficient redundancy exists in the inputs from the paired carotid body chemoreceptors so that normal ventilatory responsiveness to acute and chronic stimuli is present in goats possessing only a single carotid body.

Hyperventilation in ponies at the onset of and during steady-state exercise

We studied blood gases in ponies to assess the relationship of alveolar ventilation (VA) to pulmonary CO2 delivery during moderate treadmill exercise. In normal ponies for 1.8, 3, or 6 mph, respectively, partial pressure of CO2 in arterial blood (PaCO2) decreased maximally by 3.1, 4.4, and 5.7 Torr at 30-90 s of exercise and remained below rest by 1.4, 2.3, and 4.5 Torr during steady-state (4-8 min) exercise (P less than 0.01). Partial pressure of O2 in arterial blood (PaO2) and arterial pH, (pHa) also reflected hyperventilation. Mixed venus CO2 partial pressure (PVCO2) decreased 2.3 and 2.9 Torr by 30 s for 3 and 6 mph, respectively (P less than 0.05). In work transitions either from 1.8 to 6 mph or from 6 mph to 1.8 mph, respectively, PaCO2 either decreased 3.8 Torr or increased 3.3 Torr by 45 s of the second work load (P less than 0.01). During exercise in acute (2-4 wk) carotid body denervated (CBD) ponies at 1.8, 3, or 6 mph, respectively, PaCO2 decreased maximally below rest by 9.0, 7.6, and 13.2 Torr at 30-45 s of exercise and remained below rest by 1.3, 2.3, and 7.8 Torr during steady-state (4-8 min) exercise (P less than 0.1). In the chronic (1-2 yr) CBD ponies, the hypocapnia was generally greater than normal but less than in the acute CBD ponies. We conclude that in the pony 1) VA is not tightly matched to pulmonary CO2 delivery during exercise, particularly during transitional states, 2) the exercise hyperpnea is not mediated by PaCO2 or PVCO2, and 3) during transitional states in the normal pony, the carotid bodies attenuate VA drive thereby reducing arterial hypocapnia.

Hyperpnea of exercise at various PIO2 in normal and carotid body-denervated ponies

We studied the effect of changes in inspired [O2] on partial pressure of CO2 in arterial blood (PaCO2) during treadmill exercise (3 mph, 3% grade) in normal, acute (+2-4 wk), and chronic (+1-2 yr) carotid body-denervated (CBD) ponies. In all studies, PaCO2 decreased (P less than 0.01) from rest during exercise, reaching a nadir usually between 15 and 30 s of exercise. During normoxia [partial pressure of O2 in arterial blood (PaO2) approximately 95 Torr], the PaCO2 nadir was 2.3 +/- 0.6 Torr below resting level in normal ponies, but the nadir was greater (P less than -0.01) in acute (delta = 6.4 +/- 0.8 Torr) and chronic (delta = -4.7 +/- 1.1 Torr) CBD ponies. Hyperoxia (PaO2 approximately 180 Torr) accentuated (P less than 0.01) the hypocapnia only in the normal ponies (delta = -6.3 +/- 1.0 Torr). In contrast, hypoxia (PaO2 48 Torr) attenuated (P less than 0.01) the exercise-induced hypocapnia by 3-5 Torr in all ponies. Usually PaCO2 gradually increased after 30 s of exercise, reaching a stable level 1-3 Torr below rest by about 2 min (P less than 0.05). Tidal volume (VT) increased from rest during the first 15 s of exercise only when there was a large decrease in PaCO2. Recovery of PaCO2 after 30 s of exercise was associated with a decrease in VT toward rest. We concluded the following. 1) The accentuated hypocapnia caused by eliminating (CBD) or reducing (hyperoxia) carotid chemoreceptor activity suggests that the chemoreceptors normally dampen alveolar ventilation (VA) at the onset of exercise. 2) Attenuation of the hypocapnia at the onset of exercise by hypoxia in CBD ponies suggests that a direct CNS effect of hypoxia dampens VA. 3) Mechanisms tending to minimize the hypocapnia during exercise appear to adjust VA by modulating VT.

Regional myocardial blood flow and coronary vascular reserve in unanesthetized young calves exposed to a simulated altitude of 3500 m for 8--10 weeks

We determined regional myocardial blood flow (15-micrometer tracer microspheres) and hemodynamics in nine normal calves, seven calves with right ventricular (RV) hypertrophy induced by pulmonary artery banding (PAB) at sea level, and five calves exposed to simulated high altitude (HA) of 3,500 m (PB = 500 mm Hg) for 8--10 weeks. Progression of RV hypertrophy was very rapid in HA calves. RV weight:body weight ratio of 2.74 +/- 0.20 g/kg at 8--10 weeks of sojourn at HA significantly exceeded that in PAB calves (1.98 +/- 0.11 g/kg) 20 weeks post-banding. All calves were studied unanesthetized at sea level before (control) and during maximal coronary vasodilation (iv adenosine; 4 microM/kg per min). Normal and HA calves were also studied during acute hypoxemia (PaO2: 42 +/- 1 mm Hg) induced by administration of 12--13% O2 + N2 in the inhaled gas. RV myocardial blood flow was significantly increased only in PAB calves, whereas in HA calves it was similar to that in normal calves. Left ventricular (LV) mass and blood flow were identical in three groups of calves. Polycythemia did not occur in HA calves. Minimal coronary vascular resistance per unit weight of the hypertrophied RV was identical to that in the normal RV myocardium. This suggested that, despite very fast progression of RV hypertrophy in HA calves, functional cross-sectional area of the RV coronary vascular bed kept pace with the increase in cardiac mass. Minimal coronary vascular resistance per unit weight of the left ventricular myocardium was also identical in three groups of calves. This suggested that chronic hypoxemia by itself did not cause an increase in the functional cross-sectional area of the LV coronary vascular bed. Acute hypoxemia resulted in a significant increase in myocardial blood flow in all calves, but in HA calves, RV endo:epi perfusion ratio decreased below 1.00. Transmural RV myocardial blood flow and RV systolic pressure in HA calves during acute hypoxemia significantly exceeded that in normal calves.