Esophageal and transpulmonary pressures in acute respiratory failure

OBJECTIVE: Pressure inflating the lung during mechanical ventilation is the difference between pressure applied at the airway opening (Pao) and pleural pressure (Ppl). Depending on the chest wall's contribution to respiratory mechanics, a given positive end-expiratory and/or end-inspiratory plateau pressure may be appropriate for one patient but inadequate or potentially injurious for another. Thus, failure to account for chest wall mechanics may affect results in clinical trials of mechanical ventilation strategies in acute respiratory distress syndrome. By measuring esophageal pressure (Pes), we sought to characterize influence of the chest wall on Ppl and transpulmonary pressure (PL) in patients with acute respiratory failure. DESIGN: Prospective observational study. SETTING: Medical and surgical intensive care units at Beth Israel Deaconess Medical Center. PATIENTS: Seventy patients with acute respiratory failure. INTERVENTIONS: Placement of esophageal balloon-catheters. MEASUREMENTS AND MAIN RESULTS: Airway, esophageal, and gastric pressures recorded at end-exhalation and end-inflation Pes averaged 17.5 +/- 5.7 cm H2O at end-expiration and 21.2 +/- 7.7 cm H2O at end-inflation and were not significantly correlated with body mass index or chest wall elastance. Estimated PL was 1.5 +/- 6.3 cm H2O at end-expiration, 21.4 +/- 9.3 cm H2O at end-inflation, and 18.4 +/- 10.2 cm H2O (n = 40) during an end-inspiratory hold (plateau). Although PL at end-expiration was significantly correlated with positive end-expiratory pressure (p < .0001), only 24% of the variance in PL was explained by Pao (R = .243), and 52% was due to variation in Pes. CONCLUSIONS: In patients in acute respiratory failure, elevated esophageal pressures suggest that chest wall mechanical properties often contribute substantially and unpredictably to total respiratory impedance, and therefore Pao may not adequately predict PL or lung distention. Systematic use of esophageal manometry has the potential to improve ventilator management in acute respiratory failure by providing more direct assessment of lung distending pressure.     

Caring perspectives in nursing education: liberation, transformation and meaning

The author's personal journey through many years of nursing education as both a student and faculty member lead to a theoretical exploration of a caring pedagogy between students and teachers The author places this exploration in a historical context and examines education, feminist and nursing literature to evolve common themes in describing caring pedagogy within nursing Finally, the author suggests a model that forms the foundation for nursing curricula based on caring values     

Fructosamine: structure, analysis, and clinical usefulness

Glucose molecules are joined to protein molecules to form stable ketoamines, or fructosamines, through glycation, a nonenzymatic mechanism involving a labile Schiff base intermediate and the Amadori rearrangement. The amount of fructosamine in serum is increased in diabetes mellitus owing to the abnormally high concentration of sugar in blood. The concentration of fructosamine in serum thus reflects the degree of glycemic control attained by the diabetic patient and is useful in monitoring the effectiveness of therapy in diabetes over a period of several weeks, in a manner analogous to the determination of glycated hemoglobin. Of the analytical approaches used to measure fructosamine, affinity chromatography with m-aminophenylboronic acid and the nitroblue tetrazolium reduction method appear to be the most practical means for clinical chemists to assay fructosamine quickly, economically, and accurately. Fructosamine values can readily distinguish normal individuals and diabetic patients in good glycemic control from diabetics in poor control. Unlike glycated hemoglobin, which reflects the average blood sugar concentration over the past six to eight weeks, fructosamine reflects the average blood sugar concentration over the past two to three weeks. Thus a clinical advantage is that fructosamine responds more quickly to changes in therapy, thereby allowing for improved glycemic control. Used in conjunction with determinations of blood sugar and (or) of glycated hemoglobin, or by itself, the fructosamine assay can provide clinically useful information for the detection and control of diabetes.     

Automated ambulatory blood pressure monitoring: clinical utility in the family practice setting

Although the percentage of patients who are treated for hypertension has increased, the percentage of those who demonstrate control of blood pressure has declined. As a result of this trend, clinicians may increasingly rely on ambulatory blood pressure monitoring to improve the diagnosis and treatment of hypertension. Studies confirm that ambulatory blood pressure monitoring devices more accurately reflect a patient's blood pressure and correlate more closely with end-organ complications than blood pressure levels measured in the physician's office. Discriminate use of this technology in specific clinical circumstances assists in identifying patients at risk for hypertension and may result in improved outcomes in this subset of patients. Ambulatory blood pressure monitoring may be particularly helpful in clinical situations such as borderline hypertension, white-coat hypertension, apparent drug resistance, hypotensive symptoms from medications or autonomic dysfunction, episodic hypertension, and evaluation of antihypertensive efficacy.     

Salicylate measurement: clinical usefulness and methodology

The salicylates are the most commonly used analgesic, antipyretic, and anti-inflammatory drugs. They are available in hundreds of preparations, many of which are over-the-counter medications. The easy access to large quantities of the drug and the widespread perception that the drug is harmless have contributed to salicylate intoxication becoming a serious and common problem, particularly among the pediatric and geriatric populations. Salicylate is still the major drug for the treatment of rheumatic diseases. The use of salicylate in high doses for the management of these patients requires close monitoring of serum salicylate levels because of the large interindividual variation in dose-serum level relationships and the narrowness of the therapeutic range. Thus, both for the management of patients intoxicated with salicylate and patients who are on high-dose salicylate therapy, the measurement of serum salicylate levels is an important clinical laboratory service. Recent research on the inhibitory effect of aspirin on platelet aggregation has led to the prophylactic use of aspirin in low doses as an antithrombotic drug. This new therapeutic use of aspirin can be aided by monitoring low serum levels of salicylate and perhaps aspirin itself. This article reviews the current state of the knowledge of the pharmacokinetics and clinical toxicology of salicylate, the clinical usefulness of salicylate measurement by the clinical laboratory, and recent development in the analytical technology for salicylate analysis.     

The assessment of transpulmonary pressure in mechanically ventilated ARDS patients

Purpose

The optimal method for estimating transpulmonary pressure (i.e. the fraction of the airway pressure transmitted to the lung) has not yet been established.

Methods

In this study on 44 patients with acute respiratory distress syndrome (ARDS), we computed the end-inspiratory transpulmonary pressure as the change in airway and esophageal pressure from end-inspiration to atmospheric pressure (i.e. release derived) and as the product of the end-inspiratory airway pressure and the ratio of lung to respiratory system elastance (i.e. elastance derived). The end-expiratory transpulmonary pressure was estimated as the product of positive end-expiratory pressure (PEEP) minus the direct measurement of esophageal pressure and by the release method.

Results

The mean elastance- and release-derived transpulmonary pressure were 14.4 ± 3.7 and 14.4 ± 3.8 cmH₂O at 5 cmH₂O of PEEP and 21.8 ± 5.1 and 21.8 ± 4.9 cmH₂O at 15 cmH₂O of PEEP, respectively (P = 0.32, P = 0.98, respectively), indicating that these parameters were significantly related (r ² = 0.98, P < 0.001 at 5 cmH₂O of PEEP; r ² = 0.93, P < 0.001 at 15 cmH₂O of PEEP). The percentage error was 5.6 and 12.0 %, respectively. The mean directly measured and release-derived transpulmonary pressure were ?8.0 ± 3.8 and 3.9 ± 0.9 cmH₂O at 5 cmH₂O of PEEP and ?1.2 ± 3.2 and 10.6 ± 2.2 cmH₂O at 15 cmH₂O of PEEP, respectively, indicating that these parameters were not related (r ² = 0.07, P = 0.08 at 5 cmH₂O of PEEP; r ² = 0.10, P = 0.53 at 15 cmH₂O of PEEP).

Conclusions

Based on our observations, elastance-derived transpulmonary pressure can be considered to be an adequate surrogate of the release-derived transpulmonary pressure, while the release-derived and directly measured end-expiratory transpulmonary pressure are not related.     

Thrombopoietin: Biology,clinical applications,role in the donor setting

Thrombopoietin (c-Mpl ligand) is the hematopoietic growth factor that is responsible for regulating the production of platelets from bone marrow megakaryocytes. This ∼90 kd protein has recently been isolated and is comprised of an erythropoietin domain that is ∼50% homologous to erythropoietin and a carbohydrate domain that is highly glycosylated and appears to stabilize the protein in the circulation. Thrombopoietin is produced in the liver and blood levels are determined by the mass of circulating platelets. However, there is no platelet “sensor.” Rather platelets contain high affinity thrombopoietin receptors that bind and remove thrombopoietin from the circulation and thereby directly determine circulating levels. In vitro thrombopoietin stimulates both early and late megakaryocyte precursors as well as some erythroid and multipotential progenitor cells. When administered to normal animals, it stimulates platelet production up to six-fold without affecting other lineages. However, when given to animals following chemotherapy or irradiation, it stimulates erythroid and myeloid as well as platelet recovery. Several different recombinant thrombopoietin proteins are now entering clinical trials in humans and all preliminary reports confirm a potent thrombopoietic stimulus and apparent lack of toxicity. Thrombopoietin shows great promise in preventing the thrombocytopenia associated with chemotheraphy, bone marrow transplantation, and other acute or chronic thrombocytopenic disorders. In transfusion medicine, thrombopoietin may help mobilize peripheral blood progenitor cells, stimulate donors for plateletpheresis, and enhance platelet survival and function during storage. Many studies are currently underway in all these areas and should soon establish the role of thrombopoietin in clinical medicine. © 1996 Wiley-Liss, Inc.     

Research into patients' perspectives: relevance and usefulness of phenomenological sociology

BACKGROUND: The dominant epistemology underpinning much inquiry in the field of patient evaluation of health care is positivist, with categorization and quantification being high priorities, despite the highly personal and dynamic nature of people's responses to their health care experiences. The mis-match between underpinning theoretical assumptions and the nature of the subject under investigation has led to ineffectiveness in much current inquiry into patients' perspectives. More needs to be learnt about patients' processes of evaluation prior to any summary assessment of the quality of their care. AIMS: This paper documents the search for a close fit between a study's research questions and a theoretical perspective with which to underpin the research. It describes the benefits of identifying a specifically relevant perspective, in this case phenomenological sociology, and discusses the potential of that particular perspective to underpin research within health care. METHODS: Research questions relating to patients' processes of evaluation were established. The possible contribution of a range of interpretative methodologies was considered. While all were relevant to some degree, phenomenological sociology was identified as having considerable specific potential to illuminate the patient's process of evaluation. FINDINGS: The particular strengths of phenomenological sociology relevant to the investigation of patients' processes of reflection are in highlighting the importance of subjectivity; its insistence on a clear link from theoretical development right back to the raw data; its wealth of evocative ideas and concepts that support the investigation of the development of interpretation; and the relatively accessible language and style of its texts. CONCLUSION: Time spent evaluating the potential contribution of different theoretical perspectives to a study is worthwhile, as a good choice can not only support but also enhance the quality of the research. Phenomenological sociology has much potential to underpin research into patient evaluation of health care and in nursing research more widely.     

Medication safety challenges in the palliative care setting: Nurses' perspectives

AimTo explore medication safety issues faced by general and palliative care community nurses working in rural and remote palliative care domiciliary settings.MethodAn online survey for nurses working in rural communities was conducted across the South East region of rural Victoria, Australia. Nurses from 18 community based health care organisations across the region were invited to participate in an anonymous survey addressing medication safety issues in the palliative care settings. Qualitative data obtained from the open-ended survey questions were analysed inductively.ResultsA total of 29 nurses completed the survey (response rate 28% from potential respondents). Most of the nurses were working in a rural practice providing a mixed model of community palliative care and community nursing. Medication safety issues raised by the nurses included; errors associated with dose administration aids, frequency of medications reviews undertaken by clinical pharmacists of clients’ medications, high occurrence of medications error reporting, lack of awareness of medications initiated by nurses and cytotoxic medications handling.ConclusionTargeted interventions addressing the identified issues raised by community general and palliative care nurses have the potential to improve medication safety in the domiciliary palliative care setting.