Breathhold cine MRI of left ventricular function in patients with obstructive sleep apnea: work-in-progress.

Obstructive sleep apnea (OSA) is a sleep-related breathing disorder that can cause left ventricular (LV) dysfunction. In patients with OSA, the LV dysfunction is usually evaluated by echocardiography. The purpose of this study was to evaluate whether the use of breathhold cine MRI for the study of LV dysfunction would be feasible and well tolerated by patients with OSA. Six volunteers and five patients underwent a breathhold cine MRI study of the LV using a 1.5 Tesla MR imager. Cine MRI was performed using a breathhold k-space segmented TurboFLASH technique during end-expiration. Systolic thickening of the LV septal wall was 49% +/- 16% in normals vs. 25% +/- 10.5% in patients (p < 0.05). Systolic thickening of the LV free wall was 42% +/- 12% in normals vs. 22% +/- 9% in patients (p < 0.05). There was a significant difference in end-diastolic wall thickness between the two groups. All patients tolerated the procedure well. The total duration of each study was relatively short (less than 11 min). Breathhold MRI techniques can be used to study LV dysfunction in patients with respiratory disability such as OSA.

Characteristics of nasal airflow and the effect of a nasal dilator in normal human subjects.

Nasal resistance contributes to negative airway pressure during breathing. We sought to define normal patterns of nasal flow and the effects of mechanical dilatation and splinting of the nares on flow during forced inspiration and expiration. Maximal inspiratory and expiratory flow volume loops (FVL) were determined in 17 normal subjects. Oral FVL were obtained with nares clamped and nasal FVL through a mask with and without dilatation of nares using a plastic splint (Nozovent). Oral FVL were normal in all. Two patterns of nasal FVL were observed: one indicating 'variable' extrathoracic obstruction, the other indicating 'fixed' extrathoracic obstruction. Maximal inspiratory flow at 50% of vital capacity (FiF50) was improved by the Nozovent only in those with a 'variable' pattern (FIF50 (L/sec): 1.54 +/- 0.3 to 2.86 +/- 0.5; P < 0.05, versus 1.92 +/- 0.3 to 2.21 +/- 0.3: P = 0.5). In subjects with a fixed pattern, failure of dilatation of the nares to increase flow suggests that the site of inspiratory flow limitation is within the bony nostril.

Failure of physician documentation of sleep complaints in hospitalized patients.

Sleep disorders are acknowledged to be common but remain underrecognized by the medical community, often attributed to the failure to question patients about their sleep quality. We examined the prevalence of sleep complaints (insomnia or excessive daytime sleepiness) in a group of general medical patients by administering a questionnaire to hospitalized patients in a Veterans Affairs tertiary care medical center. A total of 222 consecutive adults (215 men, 60 +/- 14 years; body mass index, 24.8 +/- 5.6) completed the questionnaire. Of these, 105 patients (47%) had either insomnia, excessive daytime somnolence, or both; 63 (28%) had excessive daytime somnolence, which was severe in 27 (12%). Of 75 patients (34%) who had insomnia, a third were taking hypnotic medication. Forty patients (18%) had snoring, which was associated with excessive daytime somnolence in 36, whereas 46 patients (21%) had either restless legs or a combination of leg jerks and leg kicking or twitching during sleep, associated with a sleep complaint (insomnia in 32). The medical records were subsequently reviewed to assess the admitting physicians' recognition of these symptoms. No record included mention of any patient symptom related to sleep. We conclude that symptoms related to sleep, some of which may be clinically important, are common, and that none of these complaints appear to be recognized by the physicians of record.

Pulmonary edema as a result of chronic upper airway obstruction.

This is the first case of an adult who developed recurrent pulmonary edema as a result of unrecognized chronic upper airway obstruction due to polyarticular juvenile rheumatoid arthritis. The case highlights the importance of considering upper airway involvement in the differential diagnosis of sedentary patients with arthritic joint disease and breathing difficulties.

Demarcation of potentially mineral-deficient areas in central and northern Namibia by means of natural classification systems.

Mineral deficiencies that lead to production losses often occur concurrently with climatic and management changes. To diagnose these deficiencies in time to prevent production losses, long-term monitoring of mineral status is advisable. Different classification systems were examined to determine whether areas of possible mineral deficiencies could be identified, so that those which were promising could then be selected for further monitoring purposes. The classification systems addressed differences in soil, vegetation and geology, and were used to define the cattle-ranching areas in the central and northern districts of Namibia. Copper (Cu), Iron (Fe), zinc (Zn), manganese (Mn) and cobalt (Co) concentrations were determined in cattle livers collected at abattoirs. Pooled faecal grab samples and milk samples were collected by farmers, and used to determine phosphorus (P) and calcium (Ca), and iodine (I) status, respectively. Areas of low P concentrations could be identified by all classification systems. The lowest P concentrations were recorded in samples from the Kalahari-sand area, whereas faecal samples collected from cattle on farms in the more arid areas, where the harder soils are mostly found, rarely showed low P concentrations. In the north of the country, low iodine levels were found in milk samples collected from cows grazing on farms in the northern Kalahari broad-leaved woodland. Areas supporting animals with marginal Cu status, could be effectively identified by the detailed soil-classification system of irrigation potential. Copper concentrations were lowest in areas of arid soils, but no indication of Co, Fe, Zn, or Mn deficiencies were found. For most minerals, the geological classification was the best single indicator of areas of lower concentrations. Significant monthly variation for all minerals could also be detected within the classification system. It is concluded that specific classification systems can be useful as indicators of areas with lower mineral concentrations or possible deficiencies.

The usefulness of faecal phosphorus and nitrogen in interpreting differences in live-mass gain and the response to P supplementation in grazing cattle in arid regions.

The average daily gains of heifers and oxen on commercial and experimental farms in Namibia were used to indicate production differences in several areas and at different rates of phosphorus and protein supplementation. Faecal concentrations of phosphorus and nitrogen were used to indicate concentrations of these nutrients in grazing. Areas with high concentrations of nitrogen in faeces proved to support high levels of average daily gain. Animals responded positively to phosphorus supplementation only when faecal nitrogen concentrations were above 12 g/kg DM. Nitrogen concentrations in faeces were directly related to average daily gain of heifers, but protein supplementation did not have a significantly positive effect on average daily gain.

Plant compositional constituents affecting between-plant and animal species prediction of forage intake.

The purpose of the study was to identify plant compositional constituents that influence forage intake. Emphasis was put on the ratio in vitro digestibility of organic matter (IVDOM):NDF because preliminary work with cattle and a limited number of forages showed the ratio to account for more variation in intake than either IVDOM or NDF alone. The compositional constituents were tested in intake prediction models using local and published data (n = 302) on grass pastures, silages, hays, straws, legumes, grass-legume mixtures, and shrubs ingested by both browsing and grass-eating ruminants (goats, red deer, impala, blesbok, sheep, cattle, and blue wildebeest). In the local experiments, esophageally fistulated and fecal bag-harnessed animals were used to collect representative grazed forage samples from pastures and to determine OM excreted, respectively. Forage intake was calculated as OM excreted divided by (1-IVDOM). Intake of silages, hays, and straws was measured indoors in digestibility trials. Intakes among species were compared after scaling for size by BW raised to the power of .9. Major contributors to the variation in forage intake were ash, hemicellulose, IVDOM:NDF, ADL, and the interaction between DM content and, respectively, ash, N, and ADL. High tannin/phenol concentrations proved limiting to intake. The ratio of IVDOM:NDF accounted for 67% of the variation in forage intake if data for which the other constituents had an effect were omitted, and the equation, OMI, g.kg BW-.9.d-1 = 70-97e-.975(IVDOM:NDF), predicted intake across all forages and ruminant species with a Sy.x of 5.3 g.kg BW-.9.d-1 (CV = 15%). The ratio of IVDOM:NDF should be valuable as a relatively inexpensive and rapid method to screen forages and cultivars.

Characteristics and efficiency of fast-growing feedlot steers fed different dietary energy concentrations.

Most prediction equations of feedlot performance cover average daily gains (ADG) below 1.5 kg/d. The question is whether these equations would be accurate for higher ADG. Medium-to-large-framed weanling and yearling steer calves were fed individually using a transponder-electronic gate system in three feedlot trials and fed in groups in two trials. Average daily gain ranged from .9 to 2.1 kg. Steers were implanted, fed to the same degree of finish, and slaughtered to obtain dressing percentage and cold carcass weight. Initial carcass weights were estimated from initial slaughter groups. Dietary ME concentration (i.e., 10.5, 11.5, 12.0, and 12.5 MJ ME/kg of DM, where 1 Mcal = 4.184 MJ), initial weight, dry matter intake (DMI), and days fed could explain 57% of the variation in ADG. The partial contribution of DMI to the total variation was only 5.2%, confirming the low correlation between DMI and ADG in feedlot trials. The correlation between metabolizable energy intake (MEI) and MEI/ADG also was low, but 80% of the variation in MEI/ADG was accounted for by the variation in ADG. Intake patterns, regardless of dietary energy concentration, indicate that ADG increased with DMI only when ADG was below 1.5 kg/d. Therefore, current prediction equations apparently overpredict ME requirements for fast-growing feedlot steers. Optimal performance occurred at a ME concentration of 12.0 MJ/kg of DM rather than 12.5 MJ/kg of DM. Dressing percentage and carcass gain increased as dietary energy concentration and ADG increased, and current prediction equations should predict that of fast-growing feedlot steers equally well.

Retention time of digesta in the rumen: its repeatability and relationship with wool production of Merino rams.

The purpose of this experiment was to determine whether differences in retention time (RT) of digesta in the rumen are associated with individual differences in wool growth rate between Merino rams. Fifty-eight rams were offered a pelleted diet at ad libitum and restricted levels. Digesta RT in the rumen was estimated from fecal excretion plots using 51Cr-mordanted feed as a marker. Wool growth rate during feeding for ad libitum intake was linearly correlated to DMI (r = .37; P < .01) and RT (r = -.32; P < .01). Multiple logistic regression analysis, used to overcome multicollinearity, showed that RT per se exerted a greater effect (P < .07) than DMI (P < .34) on wool growth rate at ad libitum feed intake. When data were blocked by wool growth rate keeping mean BW constant over all groups, high wool producers had shorter (P < .01) RT than low wool producers. Using the probability values of the multiple logistic regression analysis (CATMOD), the probability of obtaining a low wool growth rate with long RT was estimated to be .73, whereas that of obtaining a low wool growth rate with short RT approximated zero, in the ad libitum period. During the restricted feeding period, the probability of obtaining a low wool growth rate with long RT was estimated to be .46, whereas that of obtaining a low wool growth rate with short RT was estimated to be .17. Repeatability, the upper limit of heritability, was .45 (P < .01) and .6 (P < .01), using regression correlation and Spearman rank correlation coefficients, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Feedlot growth performance of steers on salinomycin, monensin and a daily rotation between the two.

The effects of salinomycin (20 mg kg-1 feed), monensin (33 mg kg-1 feed) and a daily rotation of these ionophores, on average daily gain (ADG), average daily feed intake (ADFI) and feed conversion efficiency (FCE) were investigated in 60 steers (273 kg) over an 84-day feedlot period. Individual feed intakes and weight gains were recorded. The data were fitted to linear regressions with individual animals as replicates, from which ADGs, ADFIs and FCEs were calculated. Means of parameters of the control, salinomycin, monensin and rotation treatments were respectively ADG (kg): 1.56, 1.74, 1.58 and 1.66; FCE (kg DM/kg): 5.83, 5.43, 5.53 and 5.38; ADFI (kg): 9.10, 9.43, 8.83 and 8.90; final weight (kg): 402, 419, 407 and 413. Salinomycin showed the greatest improvement in gain, whereas monensin did not affect gain and tended to decrease feed intake. The rotation programme did not result in added benefits above those that could be obtained with a single ionophore (salinomycin), although feed efficiency tended to increase.

Effect of protein source on ruminal fermentation and passage of amino acids to the small intestine of lactating cows.

Four lactating Holstein cows, fitted with T-type cannulas in the proximal duodenum, were used in a 4 x 4 Latin square design to determine the effect of protein supplement on production, ruminal digestion, and profile and the quantity of AA available for absorption. Supplemental protein sources were blood meal, corn gluten meal, blood meal plus corn gluten meal, and sunflower meal, which constituted 8, 10.5, 9.3, and 13% of dietary DM, respectively. The DMI and milk production were not influenced by treatment. Ruminal NH3 concentration increased with the sunflower meal diet, and molar percentage of propionate decreased with the blood meal diet. Duodenal flow of NAN was unaffected by protein source, but dietary N flow decreased, and bacterial N flow increased, when cows were fed the sunflower meal diet. Bacterial N flows were 46.0, 45.3, 46.4, and 65.8% of NAN for the respective diets. The AA profiles of isolated ruminal bacteria differed among dietary treatments but were not correlated with the respective supplementary protein sources. The essential AA profiles of duodenal digesta and duodenal flow of individual AA closely reflected AA differences in protein sources, suggesting that the composition of RUP profoundly affected the composition of protein entering the intestine when supplemental protein provided 35% of total CP intake.

Amino acid profile and intestinal digestibility in dairy cows of rumen-undegradable protein from various feedstuffs.

Three lactating cows fitted with rumen cannulas and three cows fitted with proximal duodenal cannulas were used to determine the effect of in situ rumen degradation on the AA profile of rumen-undegraded protein of 12 feedstuffs. Intestinal digestibility of rumen-undegraded protein was determined using the mobile bag technique. The absorbable AA profile of rumen-undegraded protein for each feedstuff was compared with profiles of the original feedstuff and the rumen-exposed undegraded protein. Branched-chain AA in particular seemed to be rather resistant to degradation in the rumen, as was Phe. Lysine concentrations decreased in the undegraded protein fraction in 9 of 12 feedstuffs; the degradation of Met depended on the feedstuff. The absorbable AA profiles of undegraded protein, in general, closely reflected the AA profiles of the rumen-exposed residues, which suggests that rumen degradation had a greater influence than postruminal digestion on the postruminal provision of specific absorbable AA. Intestinal digestibility of undegraded protein varied from 37.8% for Eragrostis curvula hay to 98% for soybean meal; the constant digestibility factor used by most protein systems should be reconsidered.

Effect of synchronization of energy and nitrogen supply on ruminal characteristics and microbial growth.

The effect of energy and N synchronization in the rumen on microbial growth was investigated. The same daily amount of readily available energy and N sources (19 g of ruminally degradable N/kg of fermentable OM) was supplied intraruminally to sheep, according to different patterns, namely both energy and N as 12-hourly pulse-doses (fast synchronized supply), energy as 12-hourly pulse-doses and N as a continuous infusion (unsynchronized supply), energy as a continuous infusion and N as 12-hourly pulse doses (unsynchronized supply), and both energy and N as continuous infusions (slow synchronized supply). The study was done near maintenance (Exp. 1) and at a higher level of nutrition (Exp. 2). The degree of energy and N synchronization affected neither microbial flow nor efficiency of growth (P > .2 for energy x N interaction). Continuous infusion of energy resulted in a 17% (P < .05) and 14% (P = .18) higher efficiency of microbial growth than did pulse dosing in Exp. 1 and 2, respectively. This coincided with lower (P < .01) ruminal pH and higher (P < .05) ruminal lactic acid concentration for energy pulse-dose treatments. The results suggest that merely improving the degree of synchronization between energy and N release rates in the rumen does not increase microbial yield. Dietary manipulation, rather, should be aimed at first obtaining the most even ruminal energy supply pattern, and then at providing the appropriate amount of ruminally available N. Thereafter some further advantage may be gained in also ensuring a more even N supply pattern, particularly avoiding too rapid a ruminal N release.

Extreme hypercapnia in a fully alert patient.

A patient is described with decompensated chronic obstructive lung disease (COLD) and extreme hypercapnia. Despite an arterial CO2 level of 160 mm Hg, the patient remained awake and alert. This indicates that CO2 narcosis is not an invariable finding in severe hypercapnia.