Respiratory muscles and dyspnea

This article reviews the classical basis on which dyspnea is identified and quantified. The sensation or sensations of discomfort experienced during breathing are then viewed using a background of sensory physiology. Exploiting psychophysical techniques, the origin of the sensation of discomfort is viewed within the constraints of the presently-known sensory structures. The contribution of these sensory structures to the quality and quantity of discomfort is suggested, indicating the central role played by the respiratory muscles.     

Expression of the rat amylin (IAPP/DAP) gene

We have used the polymerase chain reaction with mixed sequence primers to generate a probe for rat amylin and have used this to detect expression in various rat tissues. Amylin mRNA is found in greatest concentrations in the pancreas where a single mRNA species can be detected giving a hybridisation signal intensity approximately 10% that of insulin mRNA. When the beta cell population was depleted with streptozotocin, both amylin and insulin mRNAs were reduced to a similar extent. Consistent with its supposed role in the control of carbohydrate metabolism, amylin mRNA was also found in the stomach. Unlike the related peptide, CGRP, amylin mRNA is not present in the thyroid and is not widely distributed in the central nervous system. The only nervous tissue in which it could be detected was the dorsal root ganglion. Surprisingly, amylin mRNA was also found in the lung though only at very low levels.     

Dose- and time-dependent changes in plasma catecholamines in response to endotoxin in conscious rats

Time- and dose-dependent changes in plasma catecholamines, heart rate, and blood pressure were studied in response to sublethal doses of intravenous (i.v.) bacterial endotoxin in conscious male rats. Hypotension occurred with high endotoxin (1,000 micrograms/kg), whereas hypertension occurred in the low-dose group (10 micrograms/kg). All groups had significant tachycardia, which was dose and time dependent, but heart rate was unchanged for the first 2 hr in the low-dose groups (100 and 10 micrograms/kg). Plasma levels of norepinephrine (NE) and epinephrine (E) increased with both dose and time and there was significant interaction of dose and time effects. NE levels increased maximally at 0.5 hr following the highest dose of endotoxin and remained elevated during the protocol. Plasma E levels were maximal at 0.5 hr in the high-dose group, but then declined while remaining significantly higher than the 10 and 100 micrograms/kg endotoxin-treated groups for the duration of the protocol. Peak E levels in the 100 and 10 micrograms/kg group occurred at 3.0 hr and then decreased at the 6.0 hr time. Significant increases in plasma catecholamines and heart rate with endotoxin in the absence of significant hypotension present the possibility that factors other than blood pressure may be mediating efferent sympathetic outflow in endotoxicosis.     

Effects of a clinically detectable PDA on pulmonary mechanics measures in VLBW infants with RDS.

We examined the effect of a clinically detectable patent ductus arteriosus (PDA) and its successful treatment with indomethacin on serial measures of pulmonary mechanics in 10 very-low-birthweight (VLBW) intubated infants with respiratory distress syndrome (RDS). Pulmonary mechanics were measured by the passive expiratory flow technique. Total respiratory system compliance (Crs) gradually improved as RDS resolved. However, a significant decrease in mean Crs was associated with the development of a clinically detectable PDA, ranging from 1.51 +/- 0.21 to 0.90 +/- 0.08 mL/cmH2O/m (P less than 0.05). We also noted an increase in mean Crs, from 0.90 +/- 0.08 to 1.49 +/- 0.21 mL/cmH2O/m (P less than 0.05), after successful treatment of a PDA with indomethacin. Total respiratory system resistance (Rrs) did not change. We conclude that a clinically significant PDA is associated with a decreased Crs and that successful treatment of a PDA with indomethacin is associated with an improvement in lung compliance. These findings imply that the development of a clinically detectable PDA and its subsequent treatment complicates the interpretation of pulmonary mechanics data in VLBW infants with RDS.     

Initial treatment with fixed-dose combination rosiglitazone/glimepiride in patients with previously untreated type 2 diabetes

Aim: This study assessed the efficacy and safety of two different dosing regimens of fixed‐dose combination (FDC) rosiglitazone (RSG) plus glimepiride (GLIM) compared with RSG or GLIM monotherapy in drug‐naive subjects with type 2 diabetes mellitus (T2DM). Methods: Drug‐naive subjects (n = 901) were enrolled into this 28‐week, double‐blind, parallel‐group study if their glycosylated haemoglobin A_1c (HbA_1c) was >7.5% but ≤12%. Subjects were randomized to receive either GLIM [4 mg once daily (OD) maximal], RSG (8 mg OD maximal) or RSG/GLIM FDC regimen A (4 mg/4 mg OD maximal) or RSG/GLIM FDC regimen B (8 mg/4 mg OD maximal). Patients were assessed for efficacy and safety every 4 weeks for the first 12 weeks of the study, and at weeks 20 and 28. The primary efficacy endpoint was change in HbA_1c from baseline. Key secondary endpoints included the proportion of patients achieving recommended HbA_1c and fasting plasma glucose (FPG) targets; change from baseline in FPG, insulin, C‐reactive protein (CRP), adiponectin, free fatty acids and lipids; and percentage change in homeostasis model assessment‐estimated insulin sensitivity and β‐cell function. Safety evaluations included adverse‐event (AE) monitoring and clinical laboratory evaluations. Results: At week 28, both RSG/GLIM FDC regimens significantly reduced HbA_1c (mean ± s.d.: ?2.4 ± 1.4% FDC regimen A; ?2.5 ± 1.4% FDC regimen B) to a greater extent than RSG (?1.8 ± 1.5%) or GLIM (?1.7 ± 1.4%) monotherapy (model‐adjusted mean treatment difference, p < 0.0001 vs. both RSG and GLIM). Significantly more subjects achieved HbA_1c target levels of ≤6.5 and <7% with either RSG/GLIM FDC regimen compared with RSG or GLIM alone (model‐adjusted odds ratio, p < 0.0001 for both comparisons). Similarly, a significantly greater reduction in FPG levels was observed in subjects treated with the RSG/GLIM FDC [mean ± s.d. (mg/dl): ?69.5 ± 57.5 FDC regimen A; ?79.9 ± 56.8 FDC regimen B) compared with RSG (?56.6 ± 58.1) or GLIM (?42.2 ± 66.1) monotherapy (model‐adjusted mean treatment difference, p < 0.0001 for both comparisons). Improvement in CRP was also observed in subjects who were treated with a RSG/GLIM FDC or RSG monotherapy compared with GLIM monotherapy. RSG/GLIM FDC was generally well tolerated, with no new safety or tolerability issues identified from its monotherapy components, and a similar AE profile was observed across FDC regimens. The most commonly reported AE was hypoglycaemia, and the incidence of confirmed symptomatic hypoglycaemia (3.6–5.5%) was comparable among subjects treated with an RSG/GLIM FDC and GLIM monotherapy. Conclusions: Compared with RSG or GLIM monotherapy, the RSG/GLIM FDC improved glycaemic control with no significant increased risk of hypoglycaemia. RSG/GLIM FDC provides an effective and well‐tolerated treatment option for drug‐naive individuals with T2DM.     

Intestinal helminth infestation is associated with increased bronchial responsiveness in children

Non-atopic asthma is the predominant phenotype in non-affluent parts of Latin America. We recently reported that infestation with Ascaris lumbricoides increased the risk of non-atopic asthma in less affluent areas of Brazil but the mechanism is unclear. The present study was conducted to determine whether helminth infestation is associated with heightened bronchial responsiveness (BHR), a common finding in asthma. A random sample of 50 asthmatic and 50 non-asthmatic controls (mean age 10.1 years) were selected from a larger cohort (n = 1,011) without knowledge of their helminth infestation status. Three stool samples were collected from each child on different days and each sample was analyzed by the Kato-Katz method for quantitative determination of helminth eggs. Bronchial provocation tests were performed with inhaled 4.5% hypertonic saline using the ISAAC Phase II standardized protocol. There was no difference between the prevalence of positive BHR in the asthmatics (20.4%) compared with the controls (14.6%) (P = 1.0). Helminth infestation was detected in 24.0% of children, with A. lumbricoides being the most common. Children with high load infestation (>or=100 eggs/g) were five times more likely to have BHR than children with low load or no infestation. Despite the small sample size the results of the present study suggest that the link between high load helminth infestation and non-atopic asthma may be mediated via heightened bronchial responsiveness, possibly due to an inflammatory response to the pulmonary phase of the helminth life cycle.     

Effects of noradrenaline and isoproterenol on cardiopulmonary function in a canine model of acute pulmonary hypertension

The authors investigated acute cardiopulmonary effects of noradrenaline and isoproterenol infusion in a canine model of increased pulmonary vascular resistance (PVR) and decreased cardiac output (CO). In six anesthetized, ventilated dogs, autologous blood clots were injected over approximately two hours to increase right ventricular (RV) afterload and decrease CO. After CO had decreased 40 percent dogs were treated with noradrenaline or isoproterenol in alternate sequence. Both drugs increased stroke volume but only isoproterenol affected CO. Flow increased from 1.3 to 3.0 L X min-1 (p less than .01) with isoproterenol infusion. Corresponding to the increase in CO, RV filling pressure and PVR decreased, from 9 to 5 mm Hg, and from 36 to 16 mm Hg X L-1 X min (p less than .01) respectively. When a moderate decrease in CO complicates an acute increase in PVR, isoproterenol may be an excellent drug to treat the decrease in flow.     

The effect of an educational program upon hospital antibiotic use

The effect of an educational program on the use of antibiotics was studied in a university-affiliated Veterans Administration Hospital. Following an initial survey of antibiotic usage, educational presentations of the collected data were made to the hospital staff which included specific prescribing errors and alternative recommendations. Then, another survey was conducted. Measurable changes following the educational presentations were limited to decreasing costs of unjustified antibiotic use. An effect was noted in decreasing unjustified use of antibiotics in prophylactic situations, but this remained the most common misuse. Thus, an educational program directed at specific prescribing errors produced little noticeable effect on the use of antibiotics in a university-affiliated hospital. The study indicates that more direct measures, such as control of use of particular antibiotics, may be required to produce a meaningful change in prescribing practices.