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Biomedical subjects

K P Strohl

Publications and source records attributed to K P Strohl.

At least 19 recordsLinked to original sources
PubMed2004

The effects of an intervention to teach medical students about obstructive sleep apnea.

BACKGROUND AND PURPOSE: To assess the effects of teaching clinically relevant core concepts about obstructive sleep apnea (OSA) to third-year core clerkship students in internal medicine. PATIENTS AND METHODS: The curriculum included a lecture and case-based discussions about OSA at one clerkship site consisting of six groups of core clerkship students in the graduating Classes of 2000 and 2001 at Case Western Reserve University School of Medicine. Students who received exposure to a lecture followed by case-based discussions (n=130) were compared to students at clerkship sites who did not (n=129). Outcomes were measured using a station on the required end-of-rotation Objective Structured Clinical Examination (OSCE), consisting of 13 items and 36 points. RESULTS: When compared to groups of students who did not have a scheduled lecture and case-based discussions, those who did scored significantly higher (P</=0.016) on a station measuring these competencies. Groups were compared in terms of performance on subscores of the OSCE and scores overall; no significant differences were found. CONCLUSIONS: Our preliminary findings suggest that teaching third-year medical students information on OSA using a lecture- and case-based discussion makes a difference to a clerkship OSCE station assessing these competencies.

Clinical Clerkship↗
PubMed2001

Childhood narcolepsy in North China.

STUDY OBJECTIVES: The purpose is to report the results of an effort to diagnose children with narcolepsy in a pediatric referral clinic. DESIGN: Between September 1998 and December 1999, a program was implemented to emphasize recognition of childhood narcolepsy. Patients underwent brain computed tomography (CT) scan and magnetic resonance imaging (MRI) testing. All children received a MSLT test following a routine night's sleep, and serological HLA typing for HLA DR2. Three who reported occasional snoring also underwent nocturnal PSG prior to the MSLT. SETTING: N/A. PATIENTS OR PARTICIPANTS: N/A. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: 29 (21 male, 8 female) children were identified with sleepiness and cataplexy. There was no evidence for brain functional or structural disease or for drug use. Sleep paralysis was elicited in 41%; hypnagogic hallucinations, in 59%. Psychosocial problems including emotional irritability and social isolation were present in 93% of the patients. Mean sleep latency on MSLT was 2.0+/-1.3 minutes; sleep-onset rapid eye movement (SOREM) occurred during 2/5 naps in 28 of 29 patients and 3/5 in 26/29 patients. The average number and latency of SOREM episodes were 4.2+/-0.9 episodes and 4.0+/-1.7 minutes, respectively. In those with snoring, a nocturnal PSG did not disclose sleep apneas/hypopneas. All patients but one were HLA DR2 positive. The estimated clinic incidence was 0.04%. CONCLUSIONS: A program for recognition in a referral neurology clinic combined with an availability of the MSLT and HLA testing resulted in the new identification in North China of a number of children with narcolepsy syndromes.

Adolescent↗
PubMed2001

REM sleep and catecholamine excretion: a study in elite athletes.

We investigated the potential influence of catecholamines on sleep architecture in endurance-trained athletes. The hypothesis was that endogenous levels of aminergic neurotransmitters influence sleep architecture. Thirteen well-trained male street cyclists (all members of the German national amateur team, mean age 23.9 years, mean body mass index 21.9 kg/m2) completed the protocol. Each subject was studied during training after a race competition (C) and later in a recovery/rest period (R) with no training and no competition. Polysomnography (PSG) was performed for one night (C) and for a second night some weeks later (R). Urinary levels of catecholamines collected during the preceding day and over the night of PSG were used as an index of excretion rate of circulating adrenergic agonists. Nighttime and daytime excretion of epinephrine and norepinephrine was significantly elevated after exercise (C vs R; P<0.01). Rapid-eye-movement sleep (REM) onset latency was significantly increased (P=0.03) and REM was significantly decreased in the first half of the night in the training compared to the resting condition (C vs R, P=0.05). REM latency was correlated with increased epinephrine excretion on the day of exercise (C, r=0.63, P=0.02). The temporal appearance of REM during the night appears to be affected in part by the intense exercise associated with race competition, and urinary catecholamines are markers that are correlated with this alteration in REM appearance.

Adult↗
PubMed2001

Incorporating inheritance into models for understanding ventilatory behavior.

Ventilation and its components (frequency and tidal volume) appear to be determined to a significant extent by inheritance. Gene manipulation, gene identification, and functional genomics now offer powerful tools to identify the strength and mode of inheritance for ventilatory behavior under steady-state and non-steady-state conditions, in health and in disease. Conscious integration of genetic principles into existing explanatory models may increase the likelihood of detecting traits that correlate with protein systems responsible for the structures and the functional components of respiration.

Humans↗
PubMed2001

Medical student competence in eliciting a history for "chronic fatigue".

PURPOSE: We report an observational study of medical students' abilities in taking a complex history for which sleep disorders is one of several possible conditions. METHODS: Students are observed taking a focused history from a simulated patient whose chief complaint is "I am tired. I cannot get anything done." Nine groups of students (n = 360) completing the internal medicine core-clerkship were evaluated by one of three examiners. Students received full, partial, or no credit for each item on a uniform behavioral checklist, which included prompts for common medical and psychiatric disorders associated with chronic fatigue. RESULTS: Observed means were lowest for items pertaining to sleep behaviors and head trauma. Fewer than half of the students inquired about whether or not the person had difficulty falling asleep at night, family history of sleep apnea, and frequency and length of naps. In contrast, the majority of students inquired about heart disease, metabolic disorders, the use of illicit drugs, alcohol consumption, and the taking of medications. Examiners accounted for a significant source of variance in scores; yet the station discriminated among top and bottom students as measured by the Objective Structured Clinical Examination (OSCE) overall. No statistically significant differences were observed on the basis of clerkship site, primary care versus traditional-track students, time of year, or gender. CONCLUSION: A majority of students do not adequately cover issues relevant to sleep in contrast to other associated disorders when taking a focused history for chronic fatigue.

Fatigue Syndrome, Chronic↗
PubMed2001

Ventilatory behavior and metabolism in two strains of obese rats.

This study examined differences in metabolism and ventilatory responsiveness in the Zucker (Z) and Koletsky (K) rat which each carry a different recessive mutation of the leptin receptor gene. The Null hypothesis was that the obese (homozygous) rats from the strains would not differ among the variables assessed. Male and female rats of obese and lean phenotypes were studied, with 5-6 animals in each group. Animals of the same age were assessed for ventilation and metabolism by whole-body plethysmography and the open circuit method. During quiet wakefulness, each animal was exposed to 5 min presentations of: room air; 10% O(2)/bal N(2); 100% O(2); room air, and 7% O(2)/93% O(2). Differences in metabolism, independent of phenotype included: K Z females and Z>K for males; CO(2) production in obese K K often for every challenge (P<0.001). A higher f and VE in Z compared with K rats was present in both genders, and persisted with each challenge. In conclusion, obese rats from these two strains do not breathe the same, even when age, weight, body mass index, and diet are alike. We conclude that that factors other than fat accumulation contribute to the expression of respiratory control and ventilation in obesity in the rat.

Analysis of Variance↗
PubMed2001

Ventilatory behavior after hypoxia in C57BL/6J and A/J mice.

Given the environmental forcing by extremes in hypoxia-reoxygenation, there might be no genetic effect on posthypoxic short-term potentiation of ventilation. Minute ventilation (VE), respiratory frequency (f), tidal volume (VT), and the airway resistance during chemical loading were assessed in unanesthetized unrestrained C57BL/6J (B6) and A/J mice using whole body plethysmography. Static pressure-volume curves were also performed. In 12 males for each strain, after 5 min of 8% O2 exposure, B6 mice had a prominent decrease in VE on reoxygenation with either air (-11%) or 100% O2 (-20%), due to the decline of f. In contrast, A/J animals had no ventilatory undershoot or f decline. After 5 min of 3% CO2-10% O2 exposure, B6 exhibited significant decrease in VE (-28.4 vs. -38.7%, air vs. 100% O2) and f (-13.8 vs. -22.3%, air vs. 100% O2) during reoxygenation with both air and 100% O2; however, A/J mice showed significant increase in VE (+116%) and f (+62.2%) during air reoxygenation and significant increase in VE (+68.2%) during 100% O2 reoxygenation. There were no strain differences in dynamic airway resistance during gas challenges or in steady-state total respiratory compliance measured postmortem. Strain differences in ventilatory responses to reoxygenation indicate that genetic mechanisms strongly influence posthypoxic ventilatory behavior.

Airway Resistance↗
PubMed2001

Treatment effects on carbon dioxide retention in patients with obstructive sleep apnea-hypopnea syndrome.

OBJECTIVES: This study was designed to examine respiratory control in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS), with or without CO(2) retention. METHODS: We recruited 10 body mass index-matched, apnea-hypopnea index-matched, age-matched, and lung function-matched OSAHS patients, according to their awake PaCO(2). Five patients were hypercapnic (PaCO(2), > or = 45 mm Hg), and five patients were eucapnic. Hypoxic responses (the ratio of the change in minute ventilation [DeltaV(E)] to the change in arterial oxygen saturation [DeltaSaO(2)] and the ratio of the change in mouth occlusion pressure over the first 100 ms of inspiration against an occluded airway [DeltaP(0.1)] to DeltaSaO(2)) and hypercapnic responses (DeltaV(E)/DeltaPCO(2) ratio and DeltaP(0.1)/DeltaPCO(2) ratio) were tested during wakefulness before treatment in all 10 patients, and before and during treatment (at 2, 4, and 6 weeks) with pressure support in the hypercapnic group. RESULTS: Hypercapnic patients had lower mean (+/- SD) DeltaV(E)/DeltaSaO(2) ratio than eucapnic patients (-0.17 +/- 0.04 vs -0.34 +/- 0.04 L /min/%SaO(2), respectively), lower mean DeltaP(0.1)/DeltaSaO(2) ratio (-0.04 +/- 0.02 vs -0.14 +/- 0.03 cm H(2)O/%SaO(2), respectively), and lower DeltaP(0.1)/DeltaPCO(2) ratio (0.23 +/- 0.1 vs 0.49 +/- 0.1 cm H(2)O/mm Hg, respectively) [p < 0.05]. After receiving noninvasive ventilation treatment, the hypercapnic and hypoxic responses of the hypercapnic patients increased. At 4 to 6 weeks, values for both responses had increased to within the normal range and PaCO(2) had fallen to < 45 mm Hg, while weight was unchanged. CONCLUSIONS: Depressed chemoresponsiveness plays a role that is independent of obesity in the development of CO(2) retention in some OSAHS patients, and it may be a response to sleep-disordered breathing.

Adult↗
PubMed2000

When, where and how to test for sleep apnea.

This presentation focused on issues relevant to the decision to perform testing for sleep disordered breathing. Polysomnographic signals can be captured equally well in both the center and in the home, by attended as well as unattended monitoring. Attention now is on clinical decisions that best match patient presentation to improved clinical outcome. Standardization interpretation can be achieved, provided sufficient experience, training, and continued surveillance of equipment function. The sleep center must evolve to manage patient with more diverse presentations and be a resource for knowledge in sleep and chronobiology to a broad range of medical issues and systems.

Arousal↗
PubMed2000

Alterations in respiratory behavior, brain neurochemistry and receptor density induced by pharmacologic suppression of sleep in the neonatal period.

UNLABELLED: The present study examined if drug suppression of active sleep (AS) in the neonate affected the development and expression of respiratory behavior. Secondly, we assessed brain neurochemistry and receptor density in specific supra-medullary brain regions to identify coincident biochemical alterations. Sprague-Dawley newborn rat pups were randomized and divided among six rat mothers (n=10/mother/group), each mother housed separately. Two untreated control (UC) groups received either no interventions or were fed milk vehicle twice daily and were handled similarly to the drug intervention animals. Pharmacological disruption of sleep was achieved by administration (2 groups of each) of either clonidine (CLO) 100 microm/kg, or scopolamine (SCO) 800 microm/kg, given orally twice daily for the first 7 days of life. On postnatal (P) days P10 and P19 of life, pups were assessed for metabolism, minute ventilation (VE), tidal volume (Vt) and frequency (f). On P21 (14 days after the end of drug exposure), pups from each condition were sacrificed and punch biopsies of the frontal cortex, hypothalamus, and hippocampus were examined for hydroxytryptophan (5-HT), and norepinepherine (NE) by HPLC. An equal number of pups were sacrificed and brains examined for muscarinic acetylcholine (mAch), alpha2-adrenergic and I1-imidazoline receptor density. RESULTS: Both CLO and SCO exposed animals had a lower V(t) and respiratory quotient than UC animals (p<0.01). CLO animals exhibited a higher f (p<0.01) and both CLO and SCO exhibited a lower V(t) (p<0.05) than the UC groups; VE was reduced in the SCO groups, compared with CLO and UC groups (p<0.01). Pattern of breathing in response to brief hypoxia exposure was altered for CLO and SCO. The normal decline in VE during sleep was not observed in CLO rats. Both drug exposures resulted in a comparable reduction in hypothalamic NE and 5-HT levels (p<0.05), while in the frontal cortex, and the hippocampus variable changes in NE and 5-HT, occurred. In CLO and SCO rats mAch receptors were increased in cortex, and reduced in hypothalamus; I1-imidazoline receptors were increased in hypothalamus and decreased in hippocampus (p<0.05 for each). In contrast, alpha2-adrenergic receptors were increased in cortex for both CLO and SCO, decreased in hypothalamus for CLO, and decreased in hippocampus for SCO (p<0.05 for each). CONCLUSIONS: these data show that drug-induced neonatal sleep suppression will alter ventilatory pattern, metabolism, and site-specific concentrations of adrenergic neurotransmitters and in receptor density, perhaps as a result of suppression of neonatal AS.

Adrenergic alpha-Agonists↗
PubMed2000

Inheritance of ventilatory behavior in rodent models.

Studies in mice and rats support the hypothesis that ventilation and its components (frequency and tidal volume) are determined to a significant extent by genetic mechanisms. The question can no longer be 'is there a genetic effect?' but rather 'how strong is the genetic component?' and 'what genes are involved?' The computational analyses of selectively bred animals now offer powerful tools to begin to dissect the genetic factors that track with ventilatory traits. Control of the conditions in the colony and in the laboratory are keys to reducing the environmental 'noise' and increasing the likelihood of detecting gene loci that correlate quantitatively with phenotype values before and during the response to chemosensory challenges. Knowing the chromosomal location of genes for ventilation will then permit the identification of proteins systems responsible for the structural and functional components for respiration.

Animals↗
PubMed2000

Vasculogenic impotence and cavernosal oxygen tension.

AIMS OF THIS STUDY: To determine the associations, if any, of cavernosal oxygen tension with vasculogenic impotence. MATERIALS AND METHODS: We evaluated penile cavernosal blood gas levels in men with suspected vasculogenic impotence during penile duplex ultrasonography and/or dynamic infusion cavernosometry and cavernosography (DICC). Patients with suspected impotence were evaluated from 1992-1996. Patient ages ranged from 24-75 y (mean 48 y). Eighteen men had arteriogenic impotence diagnosed by abnormal penile duplex ultrasound after injection of a vasoactive agent, and 23 men had venous leakage diagnosed by DICC. RESULTS: Eighteen men with arteriogenic impotence had the following mean blood gas values: pH = 7.38+/-0.01, PCO2 = 45.50+/-0.94, PO2 = 65.17+/-2.16. Twenty-three men with venogenic (venous leak) impotence had the following mean cavernosal blood gas values: pH = 7.41+/-0.01, PCO2 = 42.26+/-0.83, PO2 = 74.17+/-2.51. The differences in PO2 were significant (P<0.05). A subgroup of men with severe venous leakage had PO2 values that were similar to the low arterial PO2 values. CONCLUSION: The low PO2 in patients with arteriogenic impotence, and the subset of men with severe venous leak impotence, support a global concept of low cavernosal PO2 as a mechanism for both arteriogenic and venogenic impotence.

Adult↗
PubMed1999

Using the Berlin Questionnaire to identify patients at risk for the sleep apnea syndrome.

BACKGROUND: Although sleep apnea is common, it often goes undiagnosed in primary care encounters. OBJECTIVE: To test the Berlin Questionnaire as a means of identifying patients with sleep apnea. DESIGN: Survey followed by portable, unattended sleep studies in a subset of patients. SETTING: Five primary care sites in Cleveland, Ohio. PATIENTS: 744 adults (of 1008 surveyed [74%]), of whom 100 underwent sleep studies. MEASUREMENTS: Survey items addressed the presence and frequency of snoring behavior, waketime sleepiness or fatigue, and history of obesity or hypertension. Patients with persistent and frequent symptoms in any two of these three domains were considered to be at high risk for sleep apnea. Portable sleep monitoring was conducted to measure the number of respiratory events per hour in bed (respiratory disturbance index [RDI]). RESULTS: Questions about symptoms demonstrated internal consistency (Cronbach correlations, 0.86 to 0.92). Of the 744 respondents, 279 (37.5%) were in a high-risk group that was defined a priori. For the 100 patients who underwent sleep studies, risk grouping was useful in prediction of the RDI. For example, being in the high-risk group predicted an RDI greater than 5 with a sensitivity of 0.86, a specificity of 0.77, a positive predictive value of 0.89, and a likelihood ratio of 3.79. CONCLUSION: The Berlin Questionnaire provides a means of identifying patients who are likely to have sleep apnea.

Female↗