Machine Assistance Research Articles

Regulation of Inspiratory Neuromuscular Output during Synchronized Intermittent Mechanical Ventilation

In synchronized intermittent mandatory ventilation, it is generally accepted that the work of the inspiratory muscles is decreased by the ventilator so that their activity can be modulated by the frequency of assisted breaths. We examined the validity of this concept, which recently has been questioned. We studied five patients receiving synchronized intermittent mandatory ventilation because of an acute exacerbation of chronic obstructive pulmonary disease. The level of machine assistance, defined as the percentage of total ventilation delivered by the ventilator, was varied from a high (> 60%) to a medium (20-50%) and to the lowest tolerated value (0% in four patients). Esophageal pressure, air flow, and the electromyograms of the diaphragm and sternocleidomastoid muscles were recorded. At each level of machine assistance, distinguishing assisted from spontaneous breaths, the duration of electrical activation, the integrated electromyograms, and the work of breathing were computed. The durations of electrical activation and the integrated electromyograms of the diaphragm and sternocleidomastoid were similar in successive spontaneous and assisted breaths. At > 60% of machine assistance, the cumulative values per minute of the integrated electromyograms of the diaphragm and sternocleidomastoid and the work of breathing were reduced only by 38, 32, and 44%, respectively, compared with the lowest tolerated level of machine assistance. The durations of electrical activation did not change with increasing level of machine assistance. The degree of inspiratory muscle rest achieved by synchronized intermittent mandatory ventilation is not proportional to the level of machine assistance; furthermore, the inspiratory motor output is not regulated breath by breath but rather is constant for a given level of machine assistance.

Practical IT project management in the 1990s

Techniques and technology are converging to provide machine assistance for planning and measuring, estimating, replanning and assessing alternatives, for all types of project. This study examines current developments in methodologies, from strategic planning through to maintenance, and the role of knowledge-based systems in making ‘experience’ available to the project manager. Quality control and quality assurance is achievable in this way, and effecting an end-of-phase updating of the databases is encouraged as positive feedback to the project management process itself. Despite the advent of machine assistance, it is emphasized that management is above all else a human responsibility.

External Work Output and Force Generation during Synchronized Intermittent Mechanical Ventilation: Effect of Machine Assistance on Breathing Effort

We measured the mechanical work performed by 12 acutely ill patients during synchronized intermittent mandatory ventilation to determine the influence of volume-cycled machine assistance on inspiratory timing, respiratory muscle force development, and external work output. The frequency and tidal volume of spontaneous breaths increased at lower levels of mechanical ventilation, but inspiratory time fraction did not vary across the spectrum of machine support. As machine support was withdrawn, inspiratory work and pressure-time product increased progressively for both spontaneous and assisted breathing cycles. On a per cycle basis, work output was greater for assisted than for spontaneous breaths at all levels of comparison. Although the mean pressure developed by the patient during assisted cycles averaged approximately equal to 20% less than during adjacent unassisted cycles, contraction time averaged approximately equal to 20% longer, so that the pressure-time products were nearly equivalent for both types of cycle. Two indices of force reserve indicated that our patients taxed their maximal ventilatory capability at all but the highest levels of support. We conclude that under the conditions of this study the ventilatory pump continued to be active at all levels of machine assistance. Although work per liter related linearly to the proportion of minute ventilation borne by the patient, force generation differed little for spontaneous and machine-aided breaths at any specified level of support. Whether judged on the basis of mean developed pressure (work per liter of ventilation) or pressure-time product, little effort adaptation to volume-cycled machine assistance appears to occur on a breath-by-breath basis.

The synthesis of loop predicates

Current methods for mechanical program verification require a complete predicate specification on each loop. Because this is tedious and error prone, producing a program with complete, correct predicates is reasonably difficult and would be facilitated by machine assistance. This paper discusses techniques for mechanically synthesizing loop predicates. Two classes of techniques are considered: (1) heuristic methods which derive loop predicates from boundary conditions and/or partially specified inductive assertions: (2) extraction methods which use input predicates and appropriate weak interpretations to obtain certain classes of loop predicates by an evaluation on the weak interpretation.

Computing Machine Aids to a Development Project

A system o integrated computer programs which provide useful machine assistance to the development of a digital system will be described. The individual programs are capable of such separate engineering tasks as verifying design data, optimally locating electronic logic packages on a chassis, routing interconnecting wires and preparing documents like wiring diagrams and wire running lists. The engineer using the system need not be a computer programmer, because the machine aids programs are called into operation with a simple mnemonic language keyed to the engineer's traditional tasks. This aspect of the work, as well as the accomplishment of the individual engineering tasks, is emphasized in this paper.

The next twenty years in information retrieval; some goals and predictions

AbstractSome of the history of retrieval machine development during the past 20 years is sketched as background. At present, there still are no completely satisfactory machines for retrieval from large collections. Solution of the language problem in retrieval is currently somewhat ahead of machine development.Future developments are sketched. Work is already underway on the use of machines for the assignment of descriptors to the text, which is a crude kind of mechanical translation. Retrieval machines will soon be called upon to assist the customer in using a retrieval system by helping him to formulate his search requests. This assistance amounts to education of the customer. The notion of education by machine is extended to machine assistance in helping the customer to read the documents uncovered. It is shown how this process, when combined with work on mechanical translation, will lead to machines which can provide essays on any given subject upon request. Machines will become archival devices to store facts, not texts. Human‐to‐machine and machine‐to‐human communication will become very important. Information machines can be expected to become as numerous as computers now are.