Slow Inflation Research Articles

The effects of the pneumatic antishock garment on intracranial pressure in man: a prospective study of 12 patients with severe head injury.

Changes in intracranial pressure, mean arterial blood pressure, and cerebral perfusion pressure in response to sequential inflation of the pneumatic antishock garment were monitored in 12 patients with severe head injury and initial intracranial pressure less than 20 mm Hg. The small incremental increases in intracranial pressure that occurred with inflation of the pneumatic antishock garment were compensated for by improved hemodynamic stability and elevated mean arterial blood pressure which produced a simultaneous rise in cerebral perfusion pressure. The treatment of hypotension in traumatized patients with head injuries is paramount and sequential slow inflation of the pneumatic antishock garment can be used in such patients without apparent ill effect to the brain when the initial intracranial pressure is 20 mm Hg or below. Further study is needed to determine the safety of the device in head injured patients with elevated intracranial pressures.

Effect of Isoproterenol Inhalation on Airway Resistance in Chronic Bronchopulmonary Dysplasia

The effects of isoproterenol inhalation on pulmonary mechanics in ten infants with bronchopulmonary dysplasia (BPD), aged 41 +/- 1 (SE) weeks postconception, with gestational age at birth 30 +/- 1 weeks, and birth weight 1,590 +/- 200 g were studied. The infants had: (1) hyaline membrane disease requiring mechanical ventilation in the first five days of life, (2) mechanical ventilation and/or FIo2 greater than 30% for at least 30 days, and (3) stage III or IV radiographic changes. Thoracic gas volume, airway resistance, and specific airway conductance were measured in an infant body pressure plethysmograph during quiet breathing. Dynamic pulmonary compliance was measured using an esophageal balloon. These infants with BPD had greater airway resistance, lower specific airway conductance, and lower dynamic pulmonary compliance than 16 normal control infants (age 40 +/- 1 weeks postconception). In the infants with BPD, measurements were obtained before and 1/2, 1, 2, and 6 hours after the administration of isoproterenol aerosol 0.1% inhalation or saline aerosol placebo, five breaths by slow inflation of the lungs with an anesthesia bag. Within 30 minutes after isoproterenol inhalation, airway resistance decreased 28% +/- 5% and specific airway conductance increased 53% +/- 15%. Thoracic gas volume and dynamic pulmonary compliance did not change. There were no changes following administration of the placebo. Isoproterenol inhalation is associated with rapid short-term improvement in airway resistance and specific airway conductance in infants with BPD.

Distribution and discharge properties of airway receptors in the opossum, Didelphis marsupialis.

The distribution and discharge characteristics of airway mechanoreceptors were evaluated using vagal recording in the pentobarbital-anesthetized, artificially ventilated, open-chest adult opossum (Didelphis marsupialis), a marsupial mammal. Of the 114 receptors studied, 20 (18%) were rapidly adapting. Of the slowly adapting receptors (SARs) evaluated, 21 (22%) were in the trachea and 72 (77%) were located more peripherally; the latter group was designated as bronchial SARs. Fifteen (21%) of the bronchial SARs were found in the contralateral lung. Sixty-five percent of tracheal SARs were active at 0 cmH2O transpulmonary pressure (Ptp), whereas 85% were recruited at less than or equal to 2.5 cmH2O Ptp, which corresponds to the functional residual capacity (FRC). Only 53% of bronchial SARs were active at FRC. Tracheal and bronchial SARs with firing thresholds up to 3 cmH2O Ptp showed similar rates of discharge during static lung inflations as Ptp was increased to 20 cmH2O. Static discharge rates of bronchial receptors with firing thresholds greater than 3 cmH2O were lower than for the other groups. After rapid inflation of the lungs (0.3 s) to 10 cmH2O Ptp, SARs showed an adaptation index (percent decrease in firing rate from initial levels) of 26.5%; slow inflation (1.2 s) yielded a significantly lower adaptation index (17.4%). The discharge of both tracheal and bronchial SARs was inhibited during CO2 inhalation. Specific comparisons of airway receptors in the opossum with those of other mammals yield several quantitative and qualitative differences.

Eruption forecast for Krafla Caldera

Since December 1975, Krafla, a volcano in northern Iceland, has been the site of repeated earthquakes, fissuring, and occasional eruptions (see cover figure). Intense monitoring of activity at Krafla has led to the recognition of a repetitive pattern of months‐long inflation in the caldera area, followed by sudden deflation. The systematic tilting, fissuring, and eruptions are interpreted [Björnsson et al., 1977, 1979] as being due to the periodic filling of a central magma chamber under Krafla until a critical stress is reached, at which point magma is injected into rift zones extending as far as 60 km from the central volcano. As soon as a deflation episode and associated eruption cease, a new cycle resumes, with slow inflation as magma rises from a mantle source into the magma chamber.

Mechanical properties of contracted canine bronchial segments in vitro

Airways of 2-5 mm in diameter were dissected from fresh dog lungs and mounted in a tissue bath so that they could be inflated and deflated with air. Length was held constant, and pressure and volume were monitored on an X-Y recorder. Pressure-volume curves were obtained for each airway at several difference degrees of constriction, by varying the concentration of acetylcholine (ACh) in the bath. Properties of the tissue were analyzed cy cycling airways at different speeds and by inflating them to various pressures. Circumferential length-tension curves were calculated from the inflation limbs of pressure-volume curves obtained by slow cycling (90 s for a complete cycle between -10 and 40 cmH2O). Administration of a series of increasing concentrations of ACh resulted in length-tension curves that were displaced to shorter lengths but not greatly altered in slope. These results suggest that slow inflation of the bronchus stretched only passive elements in series with a contractile element which shortened to the length determined by the concentration of ACh present.

Chapter III. The World Economy

We said last February that 1980 would be a year of slow growth, rapid inflation and massive balance of payments deficit for most of the developed world. OECD countries' industrial production, which actually showed a marginal fall, was even lower than we expected. But their aggregate GDP growth of around 1¼ per cent seems to have been almost exactly in line with our prediction, as does their current balance of payments deficit of a little over $70 billion, while the rise of 13 per cent in their consumer prices was slightly greater than we forecast. The rise in the average price of oil ('of the order of at least 60 per cent' in our forecasts, 68 per cent in actuality) played a major part in these developments.

Trade protectionism and agriculture

The proliferation in recent years of non-tariff restrictions on trade in agricultural commodities gives cause for concern. Not a few of these restrictions serve short term political ends and are not in the best or widest interests of the industry. Freer trade can solve many of the problems of slow growth, inflation and unemployment by moving the world economy to greater efficiency. Continued and increased protection will cost both developed and developing countries dear.

Geophysical events

The following item is a reprint of the geophysical section of the SEAN Bulletin of the Smithsonian Institution.Volcanic ActivityKrafla Caldera, Mývatn Area, Iceland (65.71°N, 16.75°W). The following is a report from Karl Grönvold.The relatively slow but steady inflation of Krafla was interrupted by a minor deflation event 3–10 December. This deflation was very slow and no volcanic tremor was observed. Inflation resumed on 10 December, and on 15 December the previous ground level had been reached.The number of earthquakes in the vicinity of the magma chambers had increased gradually in November, but during the mini‐deflation, earthquake activity decreased to background levels. When the previous ground level was exceeded in the second half of December, the number of recorded earthquakes started to increase again. The largest, of estimated magnitude 4, took place on 3 January and was widely felt in the area.

Mechanics of canine iliac artery smooth muscle in vitro.

Transmural pressure and external diameter were continuously recorded from intact segments of canine iliac artery and used to determine wall responses to maximal smooth muscle (SM) activation by norepinephrine (NE). Three different approaches were used:a) step inflations from low pressure following NE, B) slow, continuous inflation from low pressure following NE, and c) direct isometric and isobaric responses to NE. Passive pressure-diameter data were determined. The results show that active wall stress and diameter responses to NE determined using direct isometric and isobaric responses and from slow inflation responses (less than 1 mmHg/s) were not significantly different. Pressure-diameter and stress-strain curves determined using continuous (0.2 mmHg/s) and step pressure inflations after NE were not signficantly different. Pressure-diameter curves obtained at different inflation rates were not those expected from a simple viscoelastic material. The results suggest that slow inflation of iliac arteries with activated SM is a reasonable method for assessing contractile properties of SM. Furthermore, they also suggest that activation of iliac artery SM at high contractile element length (L greater than Lo) does not produce attenuated constriction responses.

Effects of hyperbaric oxygenation on cerebral vasomotor tone in acute intracranial hypertension: an experimental study

The effects of hyperbaric oxygenation with 2 atm. pressure and 100% oxygen on cerebrovascular tone were assessed by the reactivity of the cerebral vessels to CO 2 and vasomotor capacitance index (the cranial pressure divided by the mean arterial pressure) in 50 anaesthetized artificially ventilated dogs, in which intracranial pressure was raised by slow inflation of an extradural balloon. Hyperbaric oxygenation reduced the intracranial pressure only at the stage when the cerebral vessels were still responsive to CO 2, as indicated by a rise in intracranial pressure of 30–70 mmHg; under these circumstances, both the reactivity of CO 2 and the vasoconstrictor tone of cerebral vessels were improved by hyperbaric oxygenation. At this stage, rapid decrease of the intracranial pressure produced by deflation of the extradual balloon showed no rebound, and hyperbaric oxygenation rapidly restored the vasomotor tone. When CO 2 failed to influence the intracranial pressure of about 100 mmHg hyperbaric oxygenation did not aid the recovery of the reactivity of the cerebral vessels to CO 2 or the vasoconstrictor tone. In extreme intracranial hypertension (above 100 mmHg) when there was reactivity to CO 2 and the electroencephalogram was flat, rapid balloon deflation was followed by a further gradual increase of intracranial pressure and hyperbaric oxygenation did not restore the cerebrovascular tone. The effect of hyperbaric oxygenation in experimental intracranial hypertension appeared to be dependent upon the vasoconstrictor tone of the cerebral vessels, which would be indicated by a vasodilator response to CO 2.

Slow Growth and High Inflation for 1974

Slow Growth and High Inflation for 1974

Effects of a cerebral vasodilator agent (Praxilene) on cerebral hemodynamics in acute intracranial hypertension and cerebral edema

Twenty mongrel dogs were used and the effects of the vasodilator "Praxilene" (2 mg/Kg i.v.) on cerebral blood flood flow (CBF), oxygen availability (O2a) and intracranial pressure (ICP) were srudied in acute intracranial hypertension produced by slow inflation of epidural balloon and in cerebral edema produced by epidural application of dry ice for ten minutes. The local CBF was measured by the heat clearance method with double thermister or thermocouple, while measuring O2a by polarograph using open tip type of platinum electrode with the diameter of 50 to 270μ. ICP was measured by epidural microballoon method. In normal controls, CBF was increased for 9.6 minutes after the administration of Praxilene (2 mg/Kg i.v.) approximately as much' as that after 10% CO2 inhalation of 4 or 5 minutes, and the elevation of O2a was paralleled to the increase of CBF. But ICP was elevated by mean 7.2 mmHg by the administration of Praxilene, while 10% CO2 inhalation elevated ICP by mean 18.7 mmHg. Therefore, Praxilene increased CBF with less increase of ICP than 10% CO2 inhalation. In acute intracranial hypertension by epidural balloon compression, CBF and O2a were not increased so much by the administration of Praxilene as controls with normal ICP. When ICP was raised to the level higher than 30 to 50 mmHg, Praxilene induced further increase of ICP and the harmful effects on systemic circulation such as hypotension, arrhythmia and bradycardia. Under these condition CBF and O2a were no longer increased. Cerebral edema was produced in five experiments. CSF pressure was measured by cisternal puncture at 24 to 48 hours after injury. It was ranged from 8 to 11 mmHg in all cases. CBF and O2a were measured in the lesion and in the contralateral normal area. O2a electrode was located at the same point where CBF electrode was inserted. In two of five experiments, CBF and O2a were not increased within the lesion by the administration of Praxilene In other three experiments, CBF was increased slightly by it, but the effects of Praxilene to CBF and O2a were abolished when ICP was elevated to the level of 25 to 30 mmHg by hydrostatic infusion of artificial CSF into the cisterna magna. However, in these condition CBF and O2a were increased by it in the contralateral normal area. These effects would be probably due to the decrease of the vasoreactivity to the vasodilator "Praxilene" and the abnormal hemodynamics within the lesion due to the regionally increased ICP. In some cases, it was noticed that O2a was not increased in spite of increase of CBF within the lesion by the administration of Praxilene or 10% CO2 inhalation. This would demonstrate that there were some regions within the lesion where the increased CBF was non-nutritional. In conclusion, the effect of vasodilator "Praxilene" would not be expected in the patients with intracranial hypertension more than 30 to 50 mmHg, and in those with cerebral edema even if ICP is not elevated.

The effect of hyperbaric oxygen on experimentally increased intracranial pressure.

✓ The effect of breathing high partial pressures of oxygen on intracranial pressure (ICP) was assessed in 10 anesthetized, ventilated dogs in which ICP had been increased by slow inflation of extradural balloons. Cerebrovascular responsiveness was tested by the addition of carbon dioxide (CO2) to the inspired gases. Inhalation of 100% oxygen reduced ICP by 23% when delivered at normal atmospheric pressure (arterial pO2, 585 mm Hg) and by 37% when delivered at 2 atmospheres absolute (ATA) in a hyperbaric chamber (arterial pO2, 1076 mm Hg). This reduction in ICP, which was present only during oxygen administration, was not associated with any change in arterial blood pressure or pCO2. Hyperbaric oxygen (OHP) reduced ICP only at the stage when the cerebral circulation was still responsive to CO2, as manifested by a rise in ICP; at high levels of ICP, responsiveness to both CO2 and OHP was lost. When the ipsilateral pupil became dilated following balloon inflation, a reduction in size was observed during administration of OHP in 11 out of 13 instances. During the responsive phase, when OHP reduced ICP, cerebral venous PO2 which was 41.7 ± 2.3 mm Hg (S.E.M.) on air breathing was modestly increased by OHP to 58.3 ± 2.5 mm Hg; when ICP no longer responded to OHP, cerebral venous PO2 was higher, on both air breathing (52.0 ± 4.1 mm Hg) and OHP (161.4 ± 14.7 mm Hg).

Consumers hold the reins

The Government's plan to slow inflation's growth and restore order to the economy is now in effect. Your paycheck and your company's profits bear testimony to the fact that Act I in a planned slowdown of economic growth is under way. Will the plan work? It should, if only the buying public will behave like economists. This is the great imponderable in the Administration's latest dip into the new economics. Personal consumption expenditures account for 65% of the gross national product. This means consumers provide the key leverage to economic growth. Regardless of the industry involved, products end up in consumer hands one way or the other. An understanding of consumer moods and spending habits will provide valuable insight into future sales trends of industries and products. For example, C&EN's econometric model for sales of the chemical and allied products industry, based upon retail trade sales of home furnishings, appliances, automobiles, apparel, and general merchandise, ...

Reactive hyperemia in lower extremity arteriography: an evaluation.

The value of reactive hyperemia in improving visualization in aortofemoral arteriography has been previously stressed (1, 2, 3) but the method has not yet found general acceptance. We have performed angiography after tourniquet occlusion almost routinely for the last three years, and have been impressed by the simplicity and safety of the method and the improvement in quality of the arteriograms. From a group of 200 patients with arterial disease studied in this manner, we have selected 55 in whom the timing of arterial blood flow with and without reactive hyperemia could be evaluated in serial films. We have analyzed the effect of reactive hyperemia and attempted to determine the influence of various clinical factors upon the response to tourniquet occlusion. Material and Methods Arteriography was performed either by percutaneous femoral catheterization or by translumbar injection. For this study, however, only retrograde femoral arteriograms were selected. A PE 240 J-tipped catheter was inserted via a common femoral artery. With the catheter positioned at the T-12-L-1 level, a serial abdominal aortogram was obtained. The catheter was then withdrawn to above the aortic bifurcation, and additional serial runs were made, in order, of the pelvis, thighs, and legs, each time following an injection of 25–30 ml of 60 per cent methylglucamine diatrizoate (Renografin 60) or iothalamate (Conray). A Cordis injector and Schonander AOT film changer were used. Accurate timing of the films was obtained either with the help of an automatic film-counting device or by direct recording on a Sanborn multichannel recorder. Following the control study, one or more injections were made utilizing reactive hyperemia. Blood pressure cuffs were first applied above the knees. The thighs were then flexed at the hips to 60° for one minute to elevate the legs, after which the blood pressure cuffs were rapidly inflated to 100 mm Hg above systolic pressure. The legs were then lowered and the patient positioned for the injection. After seven minutes of occlusion, both tourniquets were released and the injection started as quickly as possible thereafter, usually within thirty seconds. results Results Application of tourniquets above the knees was well tolerated by nearly all patients. Only a few individuals noted significant pain, and on some occasions it was necessary to shorten the period of occlusion. When pain occurred it appeared most often to be due to venous congestion. Patients who complained of pain were often those with a history of phlebitis or venous insufficiency. At other times, pain resulted from too brief an elevation of the legs or slow inflation of the tourniquets. No patient had clinical exacerbation of his peripheral vascular disease as a result of this procedure. The effect of reactive hyperemia was almost immediately apparent.

Assisted respiration in respiratory disease

(1) Assisted ventilation may be indicated in overwhelming respiratory infections, in post-an˦sthetic carbon dioxide retention and post-operative respiratory problems, in pulmonary œdema, obstructive airway disease associated with carbon dioxide retention, and in hypoventilation syndromes. (2) Manual methods of resuscitation are inadequate and mouth-to-mouth ventilation is better. Cabinet respirators make nursing difficult. Intermittent positive pressure (I.P.P.) or positive/negative pressure ventilation through a tracheotomy tube is the method of choice. A tracheotomy alone may suffice in some patients. (3) I.P.P. should be volume regulated. Mechanically operated rather than rubber valves are an advantage. A humidifier near the tracheostome is necessary and expired rather than inspired volumes should be monitored. (4) Cardiovascular considerations suggest a rapid inflation followed by a prolonged expiratory interval at a negative airway pressure. Respiratory considerations stress a slow inflation with a higher mean airway pressure and the hazards of the negative phase. A negative phase is probably best used in patients with shock. (5) Management does not necessarily require more than clinical judgment, airway pressure and minute volume readings, blood pressures and, perhaps, expired CO 2 analysis on occasions. Arterial blood gas tensions are only necessary in complicated situations.

Monetary Analysis in Italy

(3) If, however, the public uses the released funds for financing new expenditure, such borrowing will indeed be indicative of an inflationary process. The origin of the inflationary impulse must then be attributed to the private sector of the economy. (4) Borrowing by the Treasury from the commercial banking system for the purpose of financing expenditure has, by itself, exactly the same inflationary character as borrowing from the central bank. (5) Borrowing by the Treasury from the public by issue of short-term debt for the purpose of financing expenditure can be actually, and is at least potentially, of an inflationary character. Such borrowing can fundamentally be justified only if serving to counteract the undesirable deflationary effects of spontaneous hoarding in the private sector of the economy. Mr. Chairman, I am very grateful to you that you have taken the initiative for this panel discussion and that you have been so kind as to ask me to tell this illustrious gathering something about the methods the Nederlandsche Bank has been using to unravel the mystery of inflationary and deflationary developments. I do not claim that this method gives any final answer to the problem. I do believe, however, that it can be instrumental in attaining a better understanding of the strictly monetary aspects of the inflationary and deflationary process. Thus it may, perhaps, be helpful to both central banks and treasuries in better adapting their policies to fighting that curse of slow but persistent inflation that seems to be upon our present day world and to the lifting of which all our efforts should be dedicated.

Effect of mean circulatory filling pressure and other peripheral circulatory factors on cardiac output.

I P ONE studies curves which depict the relationship of cardiac output to mean right atria1 pressure (one of the forms of Starling’s curves), it is obvious that, within the normal range of function of the heart, cardiac output can change tremendously while the right atria1 pressure changes only slightly. This fact led to the early belief that it is not the function of the heart itself which controls cardiac output but instead that cardiac output is controlled by the various factors in the peripheral circulatory system which regulate the return of blood to the heart. Though it is not entirely true that cardiac output is independent of the function of the heart (I), nevertheless, it is hoped to emphasize in the present paper the special importance of the peripheral circulatory factors which affect venous return. In order to do this, a mathematical circuit analysis of the closed circuit circulatory system has been made. This circuit analysis has been specifically simplified so that the factors derived would be amenable to experimental test. Two of the factors which have proved to be of importance, as shown both by this circuit analysis and by experimental data, are a) ‘capacitance’ and b) ‘mean circulatory filling pressure.’ As used in these studies the term capacitance means dV/dP or, in other words, the change in volume of a particular part of the circulatory system with each unit change in pressure. This term has been used in the present paper because there is at present no term in common usage in hydrodynamics which means dV/dP. This is different from the term ‘distensibility’ which is commonly used to mean dV/dP + V. The term mean circulatory filling pressure (MCFP) has been defined previously (2), and it means ,__-

Exsufflation with negative pressure (E.W.N.P.); elimination of radiopaque material and foreign bodies from bronchi of anesthetized dogs.

THE ELIMINATION of radiopaque material from the tracheobronchial tree of anesthetized dogs was reported in a previous paper. 1 This was accomplished by two devices which produced high-volume expiratory-flow rates simulating the natural cough.* Studies of bronchial dynamics by serial bronchography revealed a twofold dilatation of the medium-sized bronchi in animals subjected to an inflationary pressure of + 40 mm. Hg. The restoration to normal of the blood gas values found in obstructive dyspnea, reported by Cherniack, Gordon, and Drimmer, 5 may be explained in part by the marked dilatation of the bronchi. The development of a more effective technique, whereby there is slow inflation of the lungs, followed by an explosive expiration, resulted in a total pressure-drop of approximately 100 mm. Hg, with expiratory-flow rates that surpassed those attainable by the most vigorous cough of normal human subjects. 6 A positive pressure blower served to inflate the lungs to a