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PubMed1994

Cerebral metabolic effects of sequential periods of hypothermic circulatory arrest.

During repair of congenital heart defects, extended periods of hypothermic circulatory arrest (CA) have been shown to cause short-term cerebral metabolic and flow abnormalities as well as long-term neuropsychologic dysfunction. Occasionally, a second period of CA is required during the same operative setting to revise a complicated repair. However, the metabolic effects of two consecutive periods of CA on the brain are unclear. In this study, we compared the recovery of cerebral metabolism after 60 minutes of CA with that after two sequential 30-minute periods of CA separated by a brief period of rewarming (30'SEQ). Fifteen neonatal piglets (2 to 3 kg) were placed on cardiopulmonary bypass at 100 mL.kg-1 x min-1 and cooled to 18 degrees C. Each animal then underwent either 60 minutes of uninterrupted cardiopulmonary bypass at 18 degrees C, 60 minutes of CA, or two 30-minute periods of CA separated by a brief period of rewarming. After these experimental periods, animals were rewarmed to 37 degrees C and weaned from cardiopulmonary bypass. Data were obtained before cardiopulmonary bypass and after cardiopulmonary bypass at 37 degrees C and included measurements of cerebral blood flow by xenon 133 clearance, arterial and sagittal sinus blood gases, and cerebral metabolism (mL O2.100 g-1 x min-1). Our results demonstrated that acute recovery of cerebral metabolism was significantly impaired after 60 minutes of CA and that recovery of cerebral metabolism after two sequential 30-minute periods of CA was significantly better than after 60 minutes of continuous CA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1980

A simple and reliable method for calcium balance using combined period and continuous fecal markers.

Calcium balances were determined in 13 patients during 2--4 3-day periods following both period marking (with carmine) and continuous marking (with polyethylene glycol or chromium). The reliability coefficient for the uncorrected fecal calcium (obtained from period marking) from one period to another was 0.82, whereas it was 0.97 for corrected fecal calcium (determined from recovery of continuous marker in 3-day fecal pools). Thus, the addition of continuous marking yielded a significantly more reliable measure of fecal calcium than obtainable by the use of period marking alone (p < 0.05); the error variance for corrected fecal calcium from one period to another was 3%, whereas it was 18% for uncorrected fecal calcium. It is concluded that a reliable measure of fecal calcium, and hence calcium balance, could be obtained by combined use of continuous and period markers, involving fecal collection over only one 3-day study period (marked by period marker), and correction of fecal calcium for the completeness of fecal collection (determined from continuous fecal marker).

Adult↗
PubMed1991

Patterns of oxygenation during periodic breathing in preterm infants.

The characteristics of the arterial oxygen saturation (SaO2) signal during episodes of hypoxaemia (SaO2 less than or equal to 80% for greater than or equal to 4 s) associated with periodic and non-periodic apnoeic pauses were studied in 16 preterm infants with cyanotic episodes (patients). and 15 asymptomatic preterm infants (controls), matched on birthweight and gestational age. The patients showed a significantly higher percentage of apnoeic pauses followed by a hypoxaemic episode (25 vs. 6%, P less than 0.01), and a two-fold increase in the slope of the desaturation curve (8.4 vs. 4.3% per s, P less than 0.005) in periodic compared with non-periodic breathing. All other characteristic of oxygenation (baseline SaO2 before episodes of hypoxaemia, delay between onset of apnoeic pause and onset of desaturation, lowest SaO2 during episodes of hypoxaemia) were similar for periodic and non-periodic breathing patterns. Similar, but not significant, differences between isolated and periodic apnoeic pauses were also present in the controls. An analysis of episodes of bradycardia (less than or equal to 100 beats per minute (bpm] showed that out of 121 episodes in the patients 118 were accompanied by a fall in SaO2 to less than or equal to 80%, and in the remaining three SaO2 fell to 82%, 85% and 86%, respectively. Thus all episodes of bradycardia (less than or equal to 100 bpm) were associated with a fall in SaO2 detected by beat-to-beat pulse oximetry. Examination of hypoxaemic episodes and their relationship with bradycardia and with apnoeic pauses, periodic and non-periodic, may help the further understanding of the control of arterial oxygenation in preterm infants with cyanotic episodes.

Apnea↗
PubMed2006

Primary intracerebral hemorrhage during asleep period.

BACKGROUND: The onset of intracerebral hemorrhage (ICH) has a circadian variation, with a lower risk during the asleep period. It is unclear, however, whether ICH during the asleep period differs from that during the awake period in pathophysiologic nature. The purpose of this study is to elucidate the incidences and clinical features of ICH during the asleep period. METHODS: We studied 129 consecutive patients with primary ICH and classified them into two groups according to the circumstance of their stroke onset, either during the awake period (awake ICH group) or the asleep period (asleep ICH group). Demographic and clinical characteristics were then compared between the two groups. RESULTS: Of the patients, 19 (14.7%) had ICH during the asleep period. The mortality rate at 1 month after the stroke was significantly higher in the asleep ICH group than in the awake ICH group (21.1% v 4.9%, P = .0325). The hemorrhage volume in the asleep ICH group was also significantly larger than that in the awake ICH group (mean volume, 32.6 mL v 16.7 mL, P = .0122). CONCLUSIONS: Our findings indicate that ICH during the asleep period may be more detrimental compared with ICH during the awake period, causing larger hematoma and higher mortality rates.

Aged↗
PubMed2006

Maternal deprivation in the early versus late postnatal period differentially affects growth and stress-induced corticosterone responses in adolescent rats.

Periodic maternal deprivation (MD) in the early postnatal period leads to permanently altered responsibility of the hypothalamus-pituitary-adrenocortical (HPA) axis to various types of stress. However, no reports appear to have described the effect of periodic MD under different conditions on growth of the developing rat and responsibility of the HPA axis to immobilization stress in adolescent rats. Furthermore, although body weight changes are known to affect stress responsibility, their relationship under periodic MD is not clear. The present study therefore used 4 different types of periodic MD: for 12 h/day from postnatal day (P)1 to P6 (12E group); for 3 h/day from P1 to P6 (3E group); for 12 h/day from P16 to P21 (12L group); and for 3 h/day from P16 to P21 (3L group). Mean body weights were less in the 3E and 12E groups than in the control group until at least 9 weeks old, although body weight gain in the 3L and 12L groups was only transiently affected. Stress-induced corticosterone levels in the 3E and 12E groups did not return to basal levels until at least 330 min after the termination of stress, while temporal variations of stress-induced corticosterone levels did not differ significantly between the 3L, 12L and control groups. Periodic MD in the first postnatal week affected growth of developing rats and responsibility of the HPA axis to immobilization stress in adolescent rats, and the extent of this modification was larger with MD for 12 h/day than with MD for 3 h/day. Conversely, periodic MD from P16 to P21 had little effect. Periodic MD in the postnatal period induces long-term effects on growth and stress responsibility of the HPA axis. Furthermore, a critical age of the pup at the time of MD exists as well as a critical length of MD for inducing these effects.

Aging↗
PubMed2004

Assessment of the photochemistry of OH and NO3 on Jeju Island during the Asian-dust-storm period in the spring of 2001.

In this study, we examined the influence of the long-range transport of dust particles and air pollutants on the photochemistry of OH and NO3 on Jeju Island, Korea (33.17 degrees N, 126.10 degrees E) during the Asian-dust-storm (ADS) period of April 2001. Three ADS events were observed during the periods of April 10-12, 13-14, and 25-26. Average concentration levels of daytime OH and nighttime NO3 on Jeju Island during the ADS period were estimated to be about 1x10(6) and 2x10(8) moleculescm(-3) ( approximately 9 pptv), respectively. OH levels during the ADS period were lower than those during the non-Asian-dust-storm (NADS) period by a factor of 1.5. This was likely to result from higher CO levels and the significant loading of dust particles, reducing the photolysis frequencies of ozone. Decreases in NO3 levels during the ADS period was likely to be determined mainly by the enhancement of the N2O5 heterogeneous reaction on dust aerosol surfaces. Averaged over 24 h, the reaction between HO2 and NO was the most important source of OH during the study period, followed by ozone photolysis, which contributed more than 95% of the total source. The reactions with CO, NO2, and non-methane hydrocarbons (NMHCs) during the study period were major sinks for OH. The reaction of N2O5 on aerosol surfaces was a more important sink for nighttime NO3 during the ADS due to the significant loading of dust particles. The reaction of NO3 with NMHCs and the gas-phase reaction of N2O5 with water vapor were both significant loss mechanisms during the study period, especially during the NADS. However, dry deposition of these oxidized nitrogen species and a heterogeneous reaction of NO3 were of no importance.

Air Pollutants↗
PubMed2004

Dry deposition (downward, upward) concentration study of particulates and heavy metals during daytime, nighttime period at the traffic sampling site of Sha-Lu, Taiwan.

Downward, upward dry deposition fluxes and total suspended particulate of particulate heavy metals (Fe, Pb, Zn, Cu, Mg and Mn) were measured in daytime and nighttime period in Sha-Lu, a small city in the central Taiwan during summer period of 2003. The results showed that the total suspended particulate concentrations of particulate mass in the daytime period (averaged 996.2 g/m3) were higher than in nighttime period (averaged 560.7 g/m3). And the downward dry deposition fluxes (averaged 54.07 g/m2s) were about two times as that of upward dry deposition fluxes (averaged 26.48 g/m2s) in the daytime period. Furthermore, the average downward dry deposition fluxes (averaged 26.22 g/m2s) were also about two times as that of upward dry deposition fluxes (averaged 12.11 g/m2s) in the nighttime period. In addition, the average downward dry deposition fluxes are greater than the upward dry deposition fluxes for all the heavy metals in either daytime or nighttime period. The proposed reasons are that the wind speed and concentration difference for daytime and nighttime period lead to these results at the traffic sampling site of central Taiwan. In addition, the deposition velocity for mass, heavy metals (Fe, Pb, Zn, Cu, Mg and Mn) during daytime and nighttime period were also calculated. The average daytime dry deposition velocity for downward particulate mass, upward particulate mass, Fe, Pb, Zn, Cu, Mg and Mn were 5.56, 2.66, 1.71, 0.18, 1.06, 0.24, 0.47 and 0.11 (cm/s), respectively. And the average nighttime dry deposition velocity for downward particulate mass, upward particulate mass, Fe, Pb, Zn, Cu, Mg and Mn were 4.70, 2.11, 1.66, 0.18, 0.86, 0.23, 0.32 and 0.07 (cm/s), respectively at traffic sampling site of central Taiwan.

Air Pollutants↗
PubMed2004

Clinical correlates of periodic breathing in neonatal polysomnography.

OBJECTIVE: Periodic breathing is a respiratory pattern typical of preterm infants, but its clinical significance has not been clarified yet. The present study was designed to investigate whether the presence of periodic breathing is specifically associated to low post-conceptional ages, preterm birth, or common clinical disorders related to preterm birth. METHODS: The study included 271 consecutive infants submitted to neonatal polysomnography, of whom 138 were born before 37 complete gestational weeks (preterm) and 133 were full-term. The main outcome measure was periodic breathing. A multivariate analysis was performed to test the specific impact of preterm birth, respiratory distress syndrome and hypoxic-ischemic encephalopathy on the occurrence of periodic breathing, with adjustment for potential confounding factors such as the post-conceptional age by the time of the polysomnography. RESULTS: Periodic breathing was twice more frequent in infants born before term (83/138 [60%]) than in full-term babies (41/133 [31%], chi2 = 22.3, P < 0.0001). The presence of periodic breathing was not significantly associated to either hypoxic-ischemic encephalopathy or respiratory distress syndrome. After a multivariate analysis, only preterm birth remained in the regression model as a specific risk factor for periodic breathing (adjusted odds ratio=5.62, P < 0.0001). CONCLUSIONS: Periodic breathing is a respiratory pattern independently associated with preterm birth, and this association cannot be imputed to the coexistence of either respiratory distress syndrome or hypoxic-ischemic encephalopathy among preterm infants. SIGNIFICANCE: The finding of periodic breathing in neonatal polysomnography correlates with preterm birth but not with its associated clinical disorders.

Apgar Score↗
PubMed2005

Cardiovascular variability during periodic leg movements: a spectral analysis approach.

OBJECTIVE: Changes in cardiovascular measures have been advocated as sensitive markers of phasic events arising from sleep. The current study was aimed to analyse the effects of periodic leg movements (PLMS) on heart rate variability (HRV) during NREM sleep in patients having restless legs syndrome and periodic leg movements during sleep. METHODS: The absolute and normalized high- and low-frequency peaks from spectral analysis (FFT) of R-R intervals, the HRV changes using wavelet transform, the geometric and time domain HRV were measured in 14 patients with restless legs syndrome and PLMS. The analysis was done comparing one hundred, 10 min periods with PLMS (PLMS+) and 60 periods without PLMS (PLMS-) in stage 2 of NREM sleep. In 8 patients analysis was also done in slow wave sleep (SWS). RESULTS: Occurrence of PLMS induced changes in geometrical indices of HRV, with a rise of the triangular index and the triangular interpolation of R-R intervals in PLMS+ periods (P < 0.0001). Small changes in time domain indices were found during PLMS+ periods, while the SD of the R-R intervals (SDNN), reflecting global HRV, was significantly higher (P = 0.001). While the low frequency (LF) power significantly increased in PLMS+ periods (P < 0.0001), high frequency (HF) power showed a weak and not significant reduction. The rise in sympathetic activity as detected by frequency domain HRV analysis was related to density and interval of PLMS. Comparison between sleep stages of NREM sleep demonstrated lower values of HRV measures when PLMS+ periods occur in SWS. CONCLUSIONS: Overall, PLMS occurrence was associated with a shift to increased sympathetic activity without significant changes in cardiac parasympathetic activity. The frequency domain analysis of HRV appears to be an easy tool to estimate the autonomic changes related to PLMS and PLMS- arousals and to differentiate their occurrence during stage 2 and deep sleep. SIGNIFICANCE: Spectral HRV measures may offer a simple approach to estimate the degree of autonomic changes occurring in relation to periodic leg movements in restless legs patients.

Adult↗
PubMed2006

Effect of latency period after premature rupture of membranes on 2 years infant mortality (DOMINOS study).

OBJECTIVE: To assess the impact of a short latency period after preterm premature rupture of the membranes (PPROM) on infant mortality. STUDY DESIGN: A prospective cohort study of women with PPROM between 24(0/7) and 33(6/7) weeks' in singleton gestation was performed in all maternity wards of the Rhône-Alpes Region. Neonatal and infant outcomes were compared according to the latency period (<48 h and > or =48 h). The primary outcome was the mortality rate and the secondary outcome was a composite variable of significant neurological disorders at 2 years of age. Outcomes was stratified according to gestational age at rupture. Univariate and multiple logistic regression analyses were used with SAS statistical software. RESULTS: Out of 471 women recruited in the study at a mean gestational age of 30.5+/-0.2 weeks, 170 (37%) presented with a <48-h latency period, and 301 (63%), a > or =48-h latency period. While prior to 30 weeks' gestation, the mortality rate was higher in neonates with a short latency period (16.3% versus 7.3%, p < 0.01) with pulmonary disease being the major cause of death, a short latency period was associated with a lower mortality rate after 30 weeks' gestation (0% versus 3.7%, p=0.02). After adjusting for confounding factors, a <48-h latency period remained an independent factor associated with infant mortality prior to 30 week's gestation (odds ratio 3.8, 95% confidence interval 1.3-11.7). Significant neurological disorders were not modified by the length of the latency period. CONCLUSION: For PPROM that occur before 30 weeks' gestation, a short latency period was associated with a higher infant mortality rate. Inversely, it was associated with a lower mortality rate after 30 weeks'. There is an urgent need for a thorough evaluation of expectant management of PPROM after 30 weeks' gestation.

Adult↗
PubMed2004

Periodicities of 10-11bp as indicators of the supercoiled state of genomic DNA.

DNA sequences contain information about the bendability and native conformation of DNA. For example, a repetition of certain dinucleotides at distances of 10-11bp supports wrapping around nucleosomes and supercoiled structures of bacterial DNA. We analyzed 86 eubacterial genomes, 16 archaea, and six genomes of higher eukaryotes. First, we discuss whether or not the observed periodicities represent indeed bendability signals. This claim is confirmed since: (1) dinucleotide signals are of comparable size to mononucleotide signals, (2) the signals are present in non-coding DNA as well, and (3) repeat masking has only a minor effect on 10-11bp periodicities. Moreover, the periodicities persist up to 150bp, comparable to the nucleosome size. We show that doublet peaks in Caenorhabditis elegans and some prokaryotes can be traced back to long-ranging modulations. In mammalian genomes, we find consistently spectral peaks as observed earlier in human chromosomes 20, 21 and 22. It has been shown in previous studies that archaea have periods of 10bp, whereas eubacteria exhibit 11bp periodicities. These differences reflect different supercoiled states of microbial DNA. Is the period of 10bp an archaeal or a thermophilic feature? This question is addressed by relating periodicities to optimal growth temperatures. It turns out that the archaea Methanopyrus kandleri (t(opt)=80 degrees C) and a Halobacterium strain (t(opt)=42 degrees C) both have longer periods of about 11bp. Eubacterial genomes have consistently periods around 11bp indicative of negative supercoiling.

Animals↗
PubMed1998

Mechanical modulation of stretch-induced premature ventricular beats: induction of mechanoelectric adaptation period.

OBJECTIVE: Mechanoelectric Feedback, a mechanical intervention inducing an electrical change, is gaining credence as a cause of cardiac arrhythmia in the clinical situation. However, the precise mechanism is unknown. To elucidate this we investigated mechanical and chemical modulation of stretch-induced premature ventricular beats. METHODS: We positioned a balloon in the left ventricle of an isolated heart (New Zealand White rabbit), perfused by the Langendorff technique. Balloon inflation regularly produces premature ventricular beats. Monophasic action potentials, ECG's and pressure recordings monitored changes, during mechanical intervention. The hearts were subjected to (i) variations in the degree of preload and duration of inflation, and (ii) cytoskeletal disrupters, colchicine and cytochalasin-B. RESULTS: Mechanical dilation of the left ventricle can not only induce premature ventricular beats, but also induce a period during which premature beats cannot be re-induced on a subsequent inflation, i.e. a mechanoelectric adaptation period. The trigger for the mechanoelectric adaptation period seems to occur immediately on balloon inflation and required up to 60 s to recover. This period started with an undershoot in the diastolic component of the monophasic action potential as well as in the peak systolic pressure, with return to control levels within the period. Deflation produced an overshoot (rather than undershoot) in the monophasic action potential duration, but this also returned to control levels within the period. Changes in preload, duration of inflation and disruption of the cytoskeleton failed to modulate the mechanically induced premature beats, or the mechanoelectric adaptation period. CONCLUSIONS: Transient ventricular stretch produces arrhythmia, followed by an antiarrhythmic adaptive period. Possible mechanisms are related to a mechanical influence on stretch-activated channels, changes in ionic concentration or diffusion, or second messenger systems, which influence membrane potential. The arrhythmic adaptation does not appear to be related to the mechanical properties of the cytoskeleton. Final elucidation of the mechanism of the mechanoelectric adaptation period demonstrated, may prove important in determining the mechanism of stretch-induced premature ventricular beats and consequently arrhythmia management.

Action Potentials↗
PubMed2001

NADH oxidase activity (NOX) and enlargement of HeLa cells oscillate with two different temperature-compensated period lengths of 22 and 24 minutes corresponding to different NOX forms.

NOX proteins are cell surface-associated and growth-related hydroquinone (NADH) oxidases with protein disulfide-thiol interchange activity. A defining characteristic of NOX proteins is that the two enzymatic activities alternate to generate a regular period length of about 24 min. HeLa cells exhibit at least two forms of NOX. One is tumor-associated (tNOX) and is inhibited by putative quinone site inhibitors (e.g., capsaicin or the antitumor sulfonylurea, LY181984). Another is constitutive (CNOX) and refractory to inhibition. The periodic alternation of activities and drug sensitivity of the NADH oxidase activity observed with intact HeLa cells was retained in isolated plasma membranes and with the solubilized and partially purified enzyme. At least two activities were present. One had a period length of 24 min and the other had a period length of 22 min. The lengths of both the 22 and the 24 min periods were temperature compensated (approximately the same when measured at 17, 27 or 37 degrees C) whereas the rate of NADH oxidation approximately doubled with each 10 degrees C rise in temperature. The rate of increase in cell area of HeLa cells when measured by video-enhanced light microscopy also exhibited a complex period of oscillations reflective of both 22 and 24 min period lengths. The findings demonstrate the presence of a novel oscillating NOX activity at the surface of cancer cells with a period length of 22 min in addition to the constitutive NOX of non-cancer cells and tissues with a period length of 24 min.

Activity Cycles↗
PubMed2000

Simulated effects on dairy cattle health of extending the voluntary waiting period with recombinant bovine somatotropin.

We simulated the effect of extending the voluntary wait period by 100 days on disorder-frequency measures that were based on cow-years (from lactations completed during the 4-year simulation horizon), metric tons of milk yield, and lactational incidence risks. A dynamic stochastic discrete-event simulation model that focuses on clinical and subclinical intramammary infections (IMI), plus clinical metabolic (left-displaced abomasum, ketosis, milk fever) and reproductive (cystic ovarian disease, dystocia, retained placenta, twinning, uterine infection) disorders in dairy herds was used. Although the voluntary wait period was increased by 100 days (50 vs. 150), the predicted difference in simulated days to conception was only 89 days for the extended voluntary wait-period group (which we attributed to higher fertility later in lactation). Herds that had a voluntary wait period of 150 days (compared to the control herds' voluntary wait period of 50 days) were predicted to have significantly lower rates of metabolic and reproductive disorders and clinical mastitis on both cow-year and milk-yield bases. Simulated control herds, on average, produced 8539 kg of milk in an average lactation of 325 days and simulated herds with a 150-day voluntary wait period 10893 kg of milk in an average lactation of 409 days. There was a significantly lower predicted rate and risk of culling for reproductive failure in the extended voluntary wait period group. The predicted lactational incidence risks for subclinical IMI were 18% higher for the extended voluntary wait period group - but extending the voluntary wait period by 100 days was predicted not to increase the risk of any of the other 10 disorders.

Algorithms↗
PubMedDate not supplied

[Consumption of antibiotics and their possible relationship with bacterial resistance in the "Costa de Ponent" health region: analysis of evolution through the initial and end periods of the last decade].

OBJECTIVE: To analyse antibiotic consumption (ABC) and its trend in primary care in an area with a high rate of bacterial resistance during the periods 1993-96 and 2000-02. DESIGN: Comparative, retrospective analysis. SETTING: Costa de Ponent Health Region. Population in 1993-96 period was 1,158,098 inhabitants; in 2000-02 period, 1,188,007 inhabitants. PARTICIPANTS: Those patients in the Area who took AB during the periods under study. MEASUREMENTS: Data obtained from the appropriate records of the Catalan Health Service. Measurement of ABC was the Defined Daily Dose (DDD)/1000 inhabitants/day (DID) [criteria of the WHO Collaborating Centre for Drugs Statistics Methodology]. Trends were quantified as percentage increase or drop, comparing the 1993-96 and 2000-02 periods. The U Mann-Whitney test was used. RESULTS: Overall consumption was high, with a light fall from 17.049 DID during the first period to 15.826 DID in the second (-7.1%). Amoxycillin increased from 4.878 DID (57.6%) to 6.19 DID (67.6%) (+26.8%), but amoxycillin-clavulanic did not rise. The percentages of macrolides, quinolones, cephalosporins, sulphonamides, and tetracyclines were higher in the first period. The variations in the consumption of clarithromycin, azithromycin, cefuroxime, cefixime, and ciprofloxacin between the two periods was the most notable point. CONCLUSIONS: Although overall ABC was high and in accord with the high rate of bacterial resistance in our area, a satisfactory evolutionary trend was found. The fall in consumption in the second period was not significant, but an appropriate modification in its profile was noted: domination of aminopenicillins and drop in macrolides, cephalosporins and fluorquinolones.

Anti-Bacterial Agents↗
PubMed1997

Efficiency optimization of the selection period in therapeutic trials.

To determine eligibility for a (randomized) clinical trial, measuring the inclusion and exclusion criteria can be extended over a period of time. During this period, known as the selection period, a patient is repeatedly examined at certain time intervals. This study describes an approach for optimizing the efficiency of the selection period. Efficiency is defined as the costs of randomizing one patient. The objective is to construct prediction models based on data obtained early in the selection period to predict subsequent exclusions. A prediction model increases the efficiency if after its application the costs per randomization are lower. The approach is illustrated using data from the selection period of the Rotterdam Cardiovascular Risk Intervention (ROCARI) trial which was composed of five consecutive patient visits. At each visit, data to determine eligibility was obtained. We found that logistic regression models based on data of the first and second visit could predict exclusions during the third visit. Application of the prediction models suggested that in this particular trial the costs per randomization would decrease by $52. As the initial costs per randomization were $1444, there would be a 3.6% (52/1444) savings in recruitment costs under the prediction models, accounting for a savings of more than $450,000. We conclude that the use of data obtained early in a selection period can predict subsequent exclusions, and therefore could increase the efficiency of such a period. The approach could be applied to data obtained in a pilot study as well as data obtained in the beginning of a prolonged intake period.

Cost Savings↗
PubMed2001

Hospital admissions and death rates from asthma in Kuwait during pre- and post-Gulf War periods.

BACKGROUND: The aim of the present study is to compare hospital admissions and death rates from asthma between pre (1987 to 1989)- and post (1992 to 1994)-Gulf War periods. METHODS: Data on annual hospital admissions by nationality and age, per International Statistical Classification of Diseases 493, were collected from the Health Statistics Department, Ministry of Health, Kuwait, and were analyzed with population data from the Annual Statistical Reports, Ministry of Planning, Kuwait. RESULTS: A total of 12,113 patients with asthma were admitted to various hospitals in Kuwait during the pre-Gulf War period compared with 9,771 patients during the post-Gulf War period. The average annual admissions rates per 100,000, people were 205 and 217, respectively, for the pre- and postwar periods. Total number of admissions showed an increase among Kuwaiti nationals during the study period. There were 95 deaths during the prewar period compared with 72 deaths during the postwar period. The mean annual death rates per 100,000 people were 1.60 and 1.59 respectively, for the pre- and post-Gulf War periods. CONCLUSIONS: This study did not show any statistically significant differences in either hospital admissions for or death rates attributable to asthma in the pre- and post-Gulf War periods in Kuwait. However, the number of hospital admissions in young adult Kuwaiti nationals increased. This study suggests hospital admissions and deaths from asthma did not increase after the invasion of Kuwait.

Adolescent↗
PubMed2003

Sleep disordered breathing may not be an independent risk factor for diabetes, but diabetes may contribute to the occurrence of periodic breathing in sleep.

OBJECTIVE(S): (a) To determine if self-reported diabetes mellitus is independently associated with sleep-disordered breathing (SDB); (b) to determine if diabetes mellitus is specifically associated with central sleep apnea including periodic breathing (Cheyne-Stokes breathing pattern) during sleep. STUDY POPULATION: The study population reflected participants in the on-going Sleep Heart Health Study (SHHS). Analyses were conducted utilizing data obtained from 4872 SHHS participants without prevalent cardiovascular disease (CVD) and 1002 participants with self-reported CVD, defined as hospitalization for non-fatal coronary heart disease, congestive heart failure, myocardial infarction, coronary artery bypass graft, and stroke. METHODS: SHHS methodologies have been previously reported and include performance of overnight, in-home polysomnography (PSG), which recorded variables reflecting sleep architecture and breathing, permitting identification of obstructive and central apneas, hypopneas, periodic breathing and oxyhemoglobin saturation (SpO(2)). Anthropomorphic metrics as well as systemic blood pressure measurements were obtained at the time of PSG. Other health data were available from questionnaires and the data sets of the parent cohorts from whom SHHS participants were recruited. The investigators assessed and compared breathing parameters, sleep architecture and CVD variables in diabetic and non-diabetic participants. The relationships between diabetes and the various study parameters, independent of potential confounders, were examined by multivariable modeling. Linear regression modeling was employed to examine the relationship between continuously distributed variables such as respiratory disturbance index log (RDI). The relationships between diabetes and dichotomous outcome variables such as central apnea index (CAI), obstructive apnea index (OAI), periodic breathing and the percentage of time spent at various levels below SpO(2) 90% were examined by the logistic regression model. Age, gender, race, BMI and neck circumference were forced into all multivariable analyses since these factors are associated with both diabetes mellitus and SDB. RESULTS: The investigators reported that the prevalence of CVD risk factors including increased BMI, waist circumference, neck circumference, triglycerides, reduced HDL cholesterol and hypertension was greater in diabetic than non-diabetic participants. Native Americans represented a disproportionately high percentage of the diabetic population. Unadjusted data obtained from participants without prevalent CVD indicated that the mean RDI was higher in the diabetic participants. Moreover, there was a greater percentage of diabetic participants in the higher RDI categories (e.g. 23.8% of the 470 diabetics and 15.6% of the 4402 non-diabetics had RDI>15, P<0.001). Similarly, the unadjusted data indicated that a significantly greater proportion of the diabetic participants spent >5% and >10% of sleep time below SpO(2) 90%, compared with the non-diabetic participants. The unadjusted data from participants without prevalent CVD indicated that the diabetic and non-diabetic participants did not differ with regard to distribution by category of OAI severity (e.g. > or =2 events/h, > or =3 events/h, or > or =4 events/h). On the other hand, although the prevalence of central apneas was low, a significantly greater proportion of diabetic participants were in the CAI categories (> or =2 events/h and > or =3 events/h) than non-diabetic subjects. There was no difference between diabetic and non-diabetic individuals with regard to CAI prevalence in the > or =4 events/h category. Of note, a greater percentage of diabetic patients exhibited periodic breathing (3.8% vs. 1.8%, diabetic and non-diabetic participants, respectively, P=0.002). Repeating the above analyses with inclusion of the participants with prevalent CVD did not change these relationships, and in fact, the differences between diabetic and non-diabetic participants with respect to central events and periodic breathing became more evident (the data forre evident (the data for this were not provided in the paper). Linear regression analyses demonstrated that BMI, age and male gender were independently related to increased RDI among participants without prevalent CVD. Furthermore, after adjusting for age, gender, race, BMI and neck circumference, there was no difference in geometric mean RDI between the diabetic and non-diabetic participants. The adjusted odds of having RDI> or =15 and the adjusted odds for spending> or =5% or > or =10% of sleep time with SpO(2) <90% did not differ between the diabetic and non-diabetic individuals. The investigators also examined sleep architecture in the study cohort. There were no differences between the diabetic and non-diabetic groups with regard to the adjusted proportion of time spent in non-REM sleep stages, although the mean percent time spent in REM sleep was 1.1% less in the diabetic individuals. The findings were the same with or without inclusion of participants with known CVD. Even after adjustment for potential confounders, in a sample without or with prevalent CVD, diabetic participants had increased adjusted odds for periodic breathing odds ratio (1.8, 95% confidence interval (CI) with a range of 1.02--3.15 in diabetic participants without prevalent CVD vs. 1.74, 95% CI with a range of 1.16--2.62 in diabetic participants with prevalent CVD). There was a suggestion of increased odds for CAI in diabetic subjects when analyzing populations with and without prevalent CVD. CONCLUSION: The authors concluded that diabetes mellitus is associated with sleep apnea but that this association is largely explained by risk factors in common for both disorders, most notably obesity. After adjusting for confounding factors there was no difference between diabetic and non-diabetic participants with regard to obstructive events. However, even after adjusting for potential confounders, there was a greater prevalence of periodic breathing in diabetic subjects. Although not reaching statistical significance, there was a suggestion of an increased prevalence of central events in the diabetic population, particularly when the sample included participants with known CVD. The investigators believed it unlikely that the findings were attributable to underlying congestive heart failure in as much as the diabetic subjects without prevalent CVD exhibited increased prevalence of periodic breathing and possibly increased central events. The authors proposed that diabetes mellitus might be a cause of SDB, mediated through autonomic neuropathy that may alter ventilatory control mechanisms. In this context, the authors commented that autonomic neuropathy may cause perturbations in ventilatory control by altering chemoreceptor gain or altering cardiovascular function (although the authors discounted underlying congestive heart failure as an explanation for the higher prevalence of periodic breathing in diabetic participants). To reinforce their conclusions, the authors cited the literature indicating increased prevalence of sleep apnea in diabetic patients with autonomic dysfunction, as well as the association between Shy--Drager syndrome, in which autonomic insufficiency is a constitutive element, and central sleep apnea.

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