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Biomedical subjects

D Hess

Publications and source records attributed to D Hess.

At least 145 records · Page 8Linked to original sources
PubMed1993

Resistance to flow through the valves of mouth-to-mask ventilation devices.

UNLABELLED: We conducted this study to determine the inspiratory and expiratory flow resistance of the valves of eight commercially available mouth-to-mask ventilation devices. METHODS & MATERIALS: We evaluated the valves of Intertech, Laerdal, Life Design Systems (LDS), Res-Q, Respironics, Rondex, Vital Signs, and White. The devices were supplied by the manufacturers and included the valve and any filter or extension tube supplied with the valve. Expiratory resistance was evaluated by directing air through the valve in the direction of flow when the patient exhales. Inspiratory resistance was evaluated by directing air through the valve in the direction of flow when a breath is delivered to the patient. Flow was controlled by a Timeter 0-75 flowmeter and measured using a calibrated Timeter RT-200. Flows of 10, 20, 30, 40, 50, 60, 70, 80, and 90 L/min were used. 'Back' pressure due to the resistance of the valves was measured using a calibrated Timeter RT-200. Resistance was calculated by dividing back pressure by flow. Five measurements were made at each flow setting for each valve. RESULTS: We observed significant differences in back pressures and resistances between the flows evaluated (p < 0.001 for both inspiratory and expiratory flows), and between the commercially available devices (p < 0.001 for both inspiratory and expiratory flows). At a flow of 50 L/min, the inspiratory back pressures produced by the devices were [mean (SD) in cm H2O] Intertech 5.2 (0.06), Laerdal 4.6 (0.09), LDS 4.7 (0.03), Res-Q 3.1 (0.04), Respironics 3.3 (0.04), Rondex 1.1 (0.02), Vital Signs 4.0 (0.06), and White 4.3 (0.10). At this same flow, the expiratory back pressures were Intertech 4.8 (0.30), Laerdal 9.1 (0.10), LDS 3.3 (0.02), Res-Q 3.7 (0.35), Respironics 0.5 (0.01), Rondex 1.4 (0.01), Vital Signs 3.6 (0.05), and White 13.7 (0.48). CONCLUSIONS: In some cases, the resistance through these devices might be considered excessive; however, most of the devices meet the International Standards Organization (ISO) standard (back pressure < 5 cm H2O at 50 L/min).

Data Collection↗
PubMed1993

[Pseudoaneurysms of the femoral artery--noninvasive diagnosis and compression therapy].

In 8 patients with pseudoaneurysms of the femoral artery, diagnosis and possible nonsurgical treatment is presented: After primary clinical diagnosis and color-Doppler or angiographic confirmation, aneurysms of less than 5 cm in diameter are treated by manual or color Doppler-supported compression. Within 9 to 36 min the lumen is occluded, remaining closed even in controls up to 12 months.

Aneurysm, False↗
PubMed1993

[The mobile tooth--the theoretical bases and practical implications of a frequent clinical problem].

In the past, especially in the 1970s, tooth mobility has been largely studied by various research groups. Since then, scientific interest in this domain has progressively decreased. However, from a clinical point of view tooth mobility has remained an important concern. This paper aims to review and update basic theoretical notions of tooth mobility after evaluation of recent studies. Finally, clinical implications are discussed.

Biomechanical Phenomena↗
PubMed1992

The use of transcranial ultrasonography to predict stroke in sickle cell disease.

BACKGROUND: Stroke, especially cerebral infarction, is a major cause of morbidity and mortality in children with sickle cell disease. Primary prevention of stroke by transfusion therapy may be feasible if there is a way to identify the patients at greatest risk. Transcranial Doppler ultrasonography can measure flow velocity in the large intracranial arteries. The narrowing of these arteries, which leads to cerebral infarction, is characterized by an increased velocity of flow. METHODS: Using transcranial Doppler ultrasonography, we prospectively measured the velocity of cerebral blood flow in children and young adults being followed because of sickle cell disease. The results were classified as either normal or abnormal on the basis of the highest velocity of flow in the middle cerebral artery. Abnormal velocity was defined as a flow greater than or equal to 170 cm per second, a definition determined by post hoc analysis to maximize the predictive success of the test. The end point was a clinically apparent first cerebral infarction. RESULTS: Two hundred eighty-three transcranial ultrasound examinations were performed in 190 patients with sickle cell disease (age at entry, 3 to 18 years). After an average follow-up of 29 months, cerebral infarction was diagnosed in seven patients. In 23 patients the results of the ultrasound examinations were abnormal, and in 167 patients they were normal. The clinical and hematologic characteristics of the two groups were similar, but six of the seven strokes occurred among the 23 patients with abnormal ultrasound results (P less than 0.00001 by Fisher's exact test). In this group, the relative risk of stroke was 44 (95 percent confidence interval, 5.5 to 346). CONCLUSIONS: Transcranial ultrasonography can identify the children with sickle cell disease who are at highest risk for cerebral infarction. Periodic ultrasound examinations and the selective use of transfusion therapy could make the primary prevention of stroke an achievable goal.

Adolescent↗
PubMed1992

Variability of blood gases, pulse oximeter saturation, and end-tidal carbon dioxide pressure in stable, mechanically ventilated trauma patients.

We evaluated the short-term variability of PaO2, PaCO2, pulse oximeter saturation (SpO2), and end-tidal PCO2 (PETCO2) in mechanically ventilated trauma patients. All patients were stable and undisturbed during the evaluation periods. Blood gases were obtained from an arterial catheter 4 times at 20-minute intervals. SpO2 and PETCO2 were recorded when the blood gases were obtained. Fifty evaluations were made in 26 patients; 24 patients were evaluated twice, with greater than or equal to 24 hours between evaluation periods. Variability was expressed as coefficient of variation (%CV) for each evaluation period. The median %CVs were 3.6% for PaO2 (95th percentile = 9.8%), 0.5% for SpO2 (95th percentile = 1.4%), 2.8% for PaCO2 (95th percentile = 7.4%), and 2.4% for PETCO2 (95th percentile = 7.1%). The overall correlation between PaCO2 and PETCO2 was r = 0.80, and the mean difference between PaCO2 and PETCO2 was 0.9 +/- 3.6 mm Hg. The variability of PETCO2 was similar to the variability of PaCO2. However, the variability of PaO2 was considerably greater than that of SpO2, which was probably related to the shape of the oxyhemoglobin dissociation curve and the relatively high saturations of the patients in this study. Variability of blood gases, SpO2, and PETCO2 should be considered when these values are clinically interpreted.

Adult↗
PubMed1992

High-yield recovery of electroblotted proteins and cleavage fragments from a cationic polyvinylidene fluoride-based membrane.

In this report we describe the use of a novel, experimental, polyvinylidene fluoride-based membrane with a cationic surface for the isolation by electroblotting of small amounts of proteins separated by gel electrophoresis for further characterization by protein fragmentation for internal sequence analysis. The membrane is characterized by a surface that mediates primarily ionic protein/membrane interactions and that allows the recovery of adsorbed proteins at high yields under relatively mild conditions. In electroblotting experiments, the novel membrane has a binding capacity that is at least equivalent to that of standard polyvinylidene fluoride membranes and is compatible with both chemical and enzymatic fragmentation of blotted proteins in situ. Intact electroblotted proteins, or fragments thereof, were eluted at high yields. Further structural analysis is demonstrated using reverse-phase high-performance liquid chromatography or gel electrophoresis to separate cleavage fragments for either pulsed-liquid- or solid-phase automated sequence analysis.

Cations↗
PubMed1992

Comparison of different treatment modalities in experimental pancreatitis in rats.

Lipolytic enzymes may play a role in the pathogenesis of acute pancreatitis. Therefore, the effects of a lipase inhibitor, THL (tetrahydrolipstatin), a protease inhibitor, FUT (nafamostat mesilate), and albumin under different conditions in rats were investigated. (a) Isolated pancreatic acini were incubated with pancreatic homogenates and triglycerides or lecithin with or without albumin and the degree of cellular destruction quantitated. (b) Taurocholate was injected into the pancreatic duct of isolated pancreas and the organ continuously perfused with either FUT, THL, or albumin. Organ damage was evaluated by measurement of pancreatic enzymes in the portal effluence. (c) Necrotizing pancreatitis was induced in vivo via retrograde taurocholate injection. FUT, THL, or albumin was applied either intravenously or injected into the pancreatic parenchyma. (a) Albumin prevented the cellular damage caused by both fatty acids and lysolecithin. (b) THL was ineffective, FUT lowered the release of pancreatic enzymes into the portal effluence, and albumin was most effective. (c) Albumin prevented the development of panlobular necrosis and lowered the degree of extrapancreatic fat necrosis. Albumin, via its ability to bind detergents, may have therapeutic implications.

Albumins↗
PubMed1992

An evaluation of the esophageal detector device using a cadaver model.

The study was conducted to evaluate the usefulness of an esophageal detector device (EDD) to correctly differentiate between esophageal and tracheal intubation. The study was conducted in the emergency department using 10 recently decreased cadavers (nine males, one female, age range 50-72 years). An 8-mm internal diameter endotracheal tube was placed orally into the trachea, and a second 8-mm ID tube was placed orally into the esophagus. Both tubes extended the same distance from the mouth, and the cuffs were not inflated. After placement of the tubes, the EDD was used by advanced life support providers (physicians, nurses, paramedics, and respiratory therapists) to determine if each tube was in the trachea or the esophagus. The persons who assessed the tube placement were not present when the tubes were placed into the cadavers. Multiple evaluators were allowed for each cadaver, but each evaluator only participated one time for each cadaver. The bulb of the EDD was squeezed by the evaluator, who then attached it to the endotracheal tube and rated the bulb inflation as immediate inflation, delayed inflation, or no inflation. Prior to participation in the study, evaluators were instructed in the use of the EDD. There were a total of 45 trials performed on the cadavers (median, four evaluations/cadaver, range, one-eight). For the tracheal tube, the EDD inflated immediately in all cases; it was thus 100% correct in identification of tracheal intubation. For the esophageal tube, the EDD did not inflate in 44 cases, and in one case it filled with vomitus; it thus correctly identified esophageal intubation in all cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

An evaluation of the resistance to flow through the patient valves of twelve adult manual resuscitators.

UNLABELLED: What is the inspiratory and expiratory resistance to flow through the patient valves of adult manual resuscitators? MATERIALS & METHODS: We evaluated the resistance to flow through the patient valves of 12 adult resuscitators (Ambu, Code Blue, DMR, Hope 4, Hospitak, Hudson, Intertech, Laerdal, Mercury, Respironics, SPUR, Vitalograph). Expiratory resistance was evaluated by directing a flow of oxygen through the valve in the direction that the patient expires. Inspiratory resistance was evaluated by directing oxygen through the valve in the direction of flow when the bag is squeezed. Flow was controlled by a Timeter 0-75 flowmeter, and measured using a calibrated Timeter RT-200. Flows of 10, 20, 30, 40, 50, 60, 70, 80, and 90 L/min were used. Resistive back pressure of the resuscitator valves was measured using a calibrated Timeter RT-200. Resistance was calculated by dividing back pressure by flow. Five measurements were made at each flow setting for each resuscitator. RESULTS: Significant differences in back pressures and resistances existed between the resuscitators for both expiratory and inspiratory flows (p less than 0.001 in each case). Significant interaction effects also existed between resuscitator brands and flows (p less than 0.001 in each case). At an expiratory flow of 50 L/min, all resuscitators except the Hospitak and Vitalograph produced a back pressure less than 5 cm H2O (the International Standards Organization standard). At an inspiratory flow of 50 L/min, all resuscitators but the Hospitak, Mercury, and Vitalograph produced a back pressure less than 5 cm H2O. CONCLUSIONS: Significant differences existed in the back pressures produced due to the flow resistance through the patient valves of these resuscitators, and these might be considered excessive in some cases. Because this was a bench study, further work is needed to determine the clinical importance of these findings.

Airway Resistance↗
PubMed1992

The volume of gas emitted from five metered dose inhalers at three levels of fullness.

UNLABELLED: We conducted this study to determine the volume of gas emitted from five commonly used metered dose inhalers (MDIs). MATERIALS & METHODS: We used the following MDIs: Alupent (Boehringer Ingelheim), Atrovent (Boehringer Ingelheim), Beclovent (Allen & Hanburys), Intal (Fisons), and Ventolin (Allen & Hanburys). The test system consisted of plastic bag, MDI adapter, 4-way stopcock, and 60-mL calibrated syringe. This system was glued together, and absence of leaks was confirmed by underwater testing. Each evaluation consisted of 10 puffs from the MDI into the bag, after which the volume in the bag was determined using the syringe, and the volume/puff was calculated by dividing by 10. Each MDI was evaluated at 3 levels of fullness: nearly full, partially empty, and nearly empty. Five measurements were made with each MDI brand, using a new MDI for each set of measurements. RESULTS: Although there was a significant difference in the volumes emitted between MDI (p less than 0.001) and the levels of fullness (p = 0.001), the volume of gas emitted from these MDIs was small (approximately 15-20 mL). A significant interaction existed between MDI brand and level of fullness (p = 0.001). CONCLUSIONS: Based on prior studies of propellant toxicity coupled with our findings on the volumes of gas emitted from MDIs, we conclude that the volumes of gas emitted are too small to be clinically important in the care of adult patients. The volume of gas emitted from an MDI is only potentially important if MDIs are used with very small tidal volumes in a closed system (eg. infants).

Chlorofluorocarbons, Methane↗
PubMed1992

Monitoring during resuscitation.

Use of many different types of monitors during resuscitation has been described in the literature. These monitors differ in their usefulness, technical feasibility, initial costs, and long-term costs (Table 4). There have been many published reports of CPR success rates in the hospital and in the pre-hospital setting. In spite of considerable advances in technology over the past 30 years, survival from CPR has changed little over that time. Although numerous types of monitoring during resuscitation are possible, and sometimes useful, the impact of expensive technology on ultimate outcome (survival) must be critically evaluated.

Cardiopulmonary Resuscitation↗
PubMed1992

[The basic ideas for evaluating diagnostic tests in medicine and periodontics].

In the medical literature, and in particular in the field of periodontology, one could observe since several years an increasing interest in diagnostic tests. However, these are often difficult to comprehend. Indeed, understanding the value of these tests implies mastering the meaning of certain basic notions such as sensitivity, specificity and predictive value. The aim of this paper is to present these essential theoretical notions in a simple way and to illustrate them using clinical examples. Finally, several applications of these tests in the field of periodontology will be discussed.

Diagnostic Tests, Routine↗
PubMed1992

[The form of retention and resistance of dental preparations. A review of the literature and the clinical implications].

Generally, the principles of tooth preparation are well established in the majority of textbooks dealing with fixed prosthodontics. However, one specific related aspect, retention and resistance form, still features some elements that might be less known to the clinician. The purpose of the present literature review is to contribute to the classification and current understanding of the terms of retention and resistance. Finally, the resulting clinical implications, focusing primarily on cast full veneer and porcelain-fused-to-metal crowns, will be discussed.

Bite Force↗
PubMed1991

Identification of the disulphide bonds in human platelet glycocalicin.

The glycoprotein Ib/IX complex on platelets is responsible for the first stage of haemostasis as an essential component in the primary adhesion of platelets to damaged vessel walls. Glycocalicin is the extracellular part of platelet glycoprotein Ib alpha and contains the von Willebrand factor and thrombin binding sites. Disulphide bonds are implicated in the von Willebrand binding site and studies with peptides point towards a region of glycocalicin with four cysteines as containing the binding sites for both von Willebrand factor and thrombin. The position and linkage of these two disulphide bonds are now determined to be 209-248 and 211-264 and the relevance of this double-loop structure for glycoprotein Ib/IX function is discussed.

Amino Acid Sequence↗
PubMed1991

Primary structure of a new actin-binding protein from human seminal plasma.

Secretory actin-binding protein (SABP), a glycoprotein from human seminal plasma, was isolated according to Akiyama and Kimura [Akiyama, K. & Kimura, H. (1990) Biochim. Biophys. Acta 1040, 206-210]. The complete amino acid sequence of SABP was determined with the aid of fragments generated by trypsin, Staphylococcus aureus V8 protease and pepsin. The single polypeptide chain of SABP contains 118 amino acids with a calculated Mr of 13,506 and pyroglutamic acid as the N-terminal residue. A single N-glycosidic carbohydrate moiety is located at Asn77. The carbohydrate composition shows an unusually high amount of fucose. The arrangement of the two disulfide bonds is Cys37-Cys63 and Cys61-Cys95. Sequence comparison revealed a high degree of similarity with a 14-kDa submandibular gland protein from mouse (45% identity and 64% similarity). SABP is identical with a prolactin-inducible protein and a protein termed gross cystic disease fluid protein 15 (sequences translated from cDNA clones), both from human breast tissues. Although SABP was also detected in saliva, in extracts of the submandibular gland and seminal vesicles, little is known of its function.

Actins↗
PubMed1991

Identification of the disulfide bonds of human complement C1s.

C1s, one of the three subcomponents of C1, the first component of the complement system, is a complex serine protease. To determine the disulfide-bonding pattern, fragments of C1s were generated by cleavage with pepsin, thermolysin, or subtilisin. Disulfide bonds have been identified by several methods, for example, direct observation of the phenylthiohydantoin derivative of cystine during Edman degradation of isolated peptides and placement in the known cDNA sequence. All of the 26 half-cystines are linked in disulfide bonds occurring at positions 50-68, 120-132, 128-141, 143-156, 160-187, 219-236, 279-326, 306-339, 344-388, 371-406, 410-534, 580-603, and 613-644. All of the disulfide bonds of the earlier described substructures of C1s, the EGF-homologous part, the two SCR units, and the two domains typical for C1s and C1r are localized within these domains.

Amino Acid Sequence↗
PubMed1991

An evaluation of pulse oximetry in prehospital care.

STUDY OBJECTIVES: We performed this study to evaluate the accuracy of pulse oximetry oxygen saturation (SpO2) against direct measurements of arterial oxygen saturation (SaO2) in the field. DESIGN: Prospective, cross-sectional, paired measurements of SpO2 against SaO2. SETTING: This evaluation was done in the prehospital setting. INTERVENTIONS: A pulse oximeter with digital probe was used to measure SpO2 in 30 patients. Arterial blood gases were drawn in the field while the pulse oximeter was in use, and oxygen saturation (HbO2) was measured by CO-oximetry. MAIN RESULTS: There was no significant difference between SpO2 (94.6 +/- 5.4%) and HbO2 (94.9 +/- 5.1%) (P = .495, beta less than .2). There was a strong correlation between SpO2 and HbO2 (r = .898). The bias between SpO2 and HbO2 was -0.3, with a precision of 2.4. When SpO2 was 88% or more, HbO2 was 90% or more in every case. Mean carboxyhemoglobin was 1.3 +/- 0.9%, and mean methemoglobin was 0.9 +/- 0.3%. There was no significant difference between the pulse oximeter heart rate and the ECG heart rate (P = .223, beta less than .2). CONCLUSION: We conclude that pulse oximetry is sufficiently accurate to be useful in the field when SpO2 is more than 88%. It is potentially useful in patients with clinical signs of acute hypoxemia and in patients receiving interventions that may produce acute hypoxemia. Further work is needed to evaluate the accuracy of pulse oximetry in the settings of elevated carboxyhemoglobin, methemoglobin, and very low saturations.

Aged↗