PubMed · 8222705
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P Dulin, C Williams. 1993. Neuromuscular blocking agents.. https://doi.org/10.1097/00003246-199311000-00041
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Health care increasingly emphasises the team approach in which doctors, nurses, and other health workers adapt and develop new skills. Before changes of this kind are widely accepted, however, there must be clarity about the training, status, authority, working relationships, career structure, and remuneration of those who undertake responsibilities well beyond their traditional roles.
Critically ill patients frequently exhibit indirect signs of tissue hypoxia such as metabolic acidosis or elevated blood lactate levels. According to the concept of supply dependence of oxygen uptake (VO2), improvement of tissue oxygenation and secondary reduced mortality rates may be achieved in critically ill patients by an increase in systemic oxygen transport (DO2). However, a critical review of available clinical data and studies suggests that a positive correlation between calculated VO2 and oxygen delivery does not necessarily imply "pathological" oxygen-supply dependence. Possible pitfalls in the interpretation of data are mathematical coupling of data, alterations of oxygen demand, and calorigenic effects of catecholamines. Due to cellular dysfunction in specific tissues, increases in blood lactate concentration in patients with severe sepsis are not proof of tissue hypoxia. Retrospective analyses of data from survivors of critical illnesses form the basis of the therapeutic concept of maximising DO2 to supranormal values. Volume expansion, erythrocytes, catecholamines, and vasoactive agents were used to reach this aim. The results of two studies suggest that beginning the optimisation of DO2 preoperatively may be beneficial in high-risk surgical patients. There is evidence, however, that therapeutic interventions designed to achieve supranormal values of cardiac output, DO2, or VO2 in a heterogeneous population of critically ill patients do not result in reduced morbidity or mortality.
OBJECTIVE: To assess the efficacy and reliability of neonatal high-frequency ventilators. DESIGN: Bench evaluation of neonatal high-frequency ventilators. SETTING: Physiology department and university hospital neonatal intensive care unit. INTERVENTIONS: HFV-Babylog 8000 (Dräger Medical), OHF 1 (Dufour), and SensorMedics 3100A (Sensor-Medics) ventilators were connected to a neonatal test-lung. Tidal volume, peak-to-peak pressure amplitude, and mean airway pressure were measured for several ventilator settings, endotracheal tube sizes, and lung compliances. MEASUREMENTS AND RESULTS: Increasing peak-to-peak pressure resulted in a linear increase in tidal volume delivery in the 0-30% range of maximum amplitude. No significant increase in tidal volume was observed with the HFV-Babylog 8000 when pressure amplitude was above 50%. The maximum tidal volume delivered was substantially smaller with the HFV-Babylog 8000 than with the OHF 1 or SensorMedics 3100A. Tidal volume increased with endotracheal tube size with all three ventilators. Increasing test-lung compliance resulted in lower tidal volumes only with OHF 1. Decreasing mean airway pressure was responsible for a decrease in tidal volume delivery with HFV-Baby-log 8000. CONCLUSION: We found that under our test conditions two of the three ventilators delivered adequate tidal volumes at the usual frequency of 15 Hz, regardless of the size of the endotracheal tube and of the mechanical properties of the respiratory system. When lung compliance increased or mean airway pressure decreased, both of which are common events during the recovery phase of hyaline membrane disease, we found that the intrinsic properties of two of the ventilators tested were responsible for a decrease in tidal volume. This decrease may account for some cases of heretofore unexplained hypercapnia.