Deflation Rate Research Articles

Long term results of inflatable mammary implants

In this retrospective study, the long term results of 167 inflatable mammary implants in 77 patients who underwent either breast reconstruction or augmentation between 1972 and 1990 were evaluated. All inflatable implants were manufactured by Heyer-Schulte/Mentor company, and were equipped with a posterior leaf valve (style 1800). The mean follow-up was 9 years (SD = 4.3). Complete deflation was found in 23.9% of the implants (22.2% deflation rate from 1972 to 1984 and 25.5% from 1985 to 1992). The incidence of this complication was significantly higher in patients who underwent previous open (p = 0.012) or closed (p = 0.038) capsulotomy. Severe contracture of the implant fibrous capsule (BAC 3 and 4) was found in 37.6% of the patients. Its incidence increased significantly when the postoperative blood loss (assessed by the volume of blood collected by suction drainage) exceeded 250 cc (p = 0.025). Neither the site of the implant (submuscular/subglandular) nor the indication for surgery (reconstruction/ augmentation) influenced the rate of severe capsular contracture significantly in this retrospective study.

Demand-flow airway pressure release ventilation as a partial ventilatory support mode

To evaluate airway pressure release ventilation as a partial ventilatory support mode by comparing a demand-flow airway pressure release ventilation system with synchronized intermittent mandatory ventilation and pressure support ventilation. Prospective, nonrandomized, cross-over trial. Medical intensive care unit in a university medical center. Sixteen consecutive patients without chronic obstructive pulmonary disease with mechanical ventilatory support of 25% to 75% of total minute ventilation on synchronized intermittent mandatory ventilation, or 25% to 75% of maximal pressure support level on pressure support ventilation. Each mode of mechanical ventilation was supplied to patients with comparable levels of partial support for 30 mins. Among three different modes, demand-flow airway pressure release ventilation achieved the lowest peak airway pressure (airway pressure release ventilation 9.1 +/- 2.6 cm H2O; pressure support ventilation 18.4 +/- 4.6 cm H2O; synchronized intermittent mandatory ventilation 34.8 +/- 7.7 cm H2O; p < .001). Hemodynamic status and oxygenation status were similar among these three modes. Five (31%) of the 16 patients felt that demand-flow airway pressure release ventilation was a less comfortable mode than synchronized intermittent mandatory ventilation or pressure support ventilation. This finding had no clear correlation with their duration of airway pressure release, preset machine deflation rate, or inspiratory/expiratory ratio of machine breath. Gross asynchrony of effort and ventilator cycling was noticed in two (13%) patients while they were receiving demand-flow airway pressure release ventilation. We conclude that for patients who do not have chronic obstructive pulmonary disease, demand-flow airway pressure release ventilation can provide effective partial ventilatory support with lower peak airway pressure when compared with pressure support ventilation and synchronized intermittent mandatory ventilation. However, this airway pressure release ventilation system may be less comfortable than the other two modes, and asynchrony may occur in some patients.

Relationships between deflation and near surface wind velocity in a coastal dune blowout

AbstractDetailed field measurements were made of the degree of surface level change in a blowout, situated in the coastal dune area of Meijendel, The Netherlands. A formula was established to express the erosivity of the wind for the corresponding 34 measurement intervals, over a period of about 3 years. Having established, for 12 wind sectors, the relationship between wind velocity at the nearest standard weather station and at five locations in the blowout, correlations were derived between the deflation rate in the blowout and the wind erosivity using standard hourly wind data.The winter season, although the most windy, is by far the least effective season: the threshold shear wind velocity is disproportionally increased because the moisture content of the surface sand is high. The soil moisture conditions are described as a function of the daily precipitation and evaporation rate. The two most relevant upper and lower threshold shear wind velocities are determined empirically. During the summer season, deflation rate is even higher than indicated by the net surface level change because deflation is partly compensated by deposition of sand transported by rainwash from the blowout margin.With regard to spatial variation in the deflation rate within the blowout, it appears that locations with relatively high velocities coincide with higher deflation rates. However, the spatial variation is commonly less than is expected from the horizontal wind velocity distribution. In view of this the role of wind direction, blowout morphology and algal coverage of the soil in the deflation rate is discussed.

Influence of short-term blood pressure variability on blood pressure determinations.

To evaluate the effect of blood pressure variability on Riva Rocci Korotkoff blood pressure determinations, we studied the intra-arterial pressure during Riva Rocci Korotkoff determinations in 25 patients. In 50 measurements with a cuff deflation rate of 2.5 mm Hg/sec, the systolic intra-arterial pressure at Korotkoff phase 1 was 2.1 (95% confidence interval 1.2-3.0) mm Hg higher than the average systolic intra-arterial pressure in the 20 seconds surrounding this moment (p less than 0.01). This elevation was shown to increase with increasing blood pressure variability, as expressed by the standard deviation of the systolic blood pressure. The elevation caused by the proposed mechanism was amplified when a slow cuff deflation rate of 1.5 mm Hg/sec was used. No significant difference was noted in the diastolic intra-arterial pressure at Korotkoff phase 5, when a normal deflation rate of 2.5 mm Hg/sec was used. A slow cuff deflation rate caused a small elevation in diastolic pressure at the moment of Korotkoff phase 5. We conclude that even normally occurring blood pressure variability might lead to a consistent elevation of systolic Riva Rocci Korotkoff blood pressure measurements. This effect is reinforced by an increasing blood pressure variability and by a slower cuff deflation rate.

The Optimum Quantity of Money in a Stochastic Economy: A Comment

In a 1989 paper, B. Taub showed, contrary to T. Bewley's conjecture, that when income is subject to an aggregate shock, inflation may be the optimal policy. This paper shows that the inflation result is due to an algebraic mistake in the calculation of the first-order condition. When income is subject to an aggregate shock, deflation is always the optimal policy if the driving process has an AR(1) representation. Moreover, for a stationary AR(1) process, the rate of deflation exceeds the rate of time preference, as Bewley conjectured. Copyright 1992 by Economics Department of the University of Pennsylvania and the Osaka University Institute of Social and Economic Research Association.

Basin dewatering near salt domes and formation of brine plumes

A previous study noted the occurrence of a subsurface brine plume with more than 160 g/L sodium chloride perched above Welsh salt dome in southwestern Louisiana. Plumes of saline groundwaters have been reported above other Gulf Coast salt domes as well. The U.S. Geological Survey code SUTRA was used to model the formation of brine plumes around a generic salt dome by basin dewatering along the flanks of the dome, and also to study the gravitational instability of a brine plume initially perched above a dome, in the absence of an externally impressed driving force for upwelling. The simulations take into account the effect of salt concentration gradients on brine density. The first set of simulations showed that a brine plume initially perched above a salt dome sank rapidly in the absence of an overpressured section. Where observed, perched brine plumes above salt domes must therefore be either (1) young (&lt; 2 Ma), if formed by basin dewatering and vertical fluid expulsion along the flanks of salt domes, or (2) formed by a continuous mechanism. The second set of simulations modeled the dewatering of a thick initially overpressured sedimentary section extending from a depth of 3 km to a depth of 10 km. The deflation rate of the overpressured section profoundly depended on whether or not a permeable conduit along the flank of the dome existed, which could collect water expelled radially inward to the flank of the dome from the overpressured sediments, and focus it upward along the flank of the dome. In most simulations the volume of compaction water was limited to only 10% of the total volume of overpressured sediment around the dome, and there was an ample amount of compaction water for a perched brine plume to form. In fact, when a perched brine plume formed, it formed very quickly (in &lt; 0.01 m.y.), after a negligible degree of deflation of the overpressured section. It is conceivable that if cycles of conduit sealing and seal rupturing occurred, perched brine plumes could be formed several times during deflation. Conditions necessary for the formation of a perched brine plume are as follows: (1) waters must be focused laterally toward the dome, within in the overpressured section, (2) there must be a conduit of sediment with relatively high vertical permeability along the flank of the dome, and (3) sediments above the dome must be more permeable than sediments along the flank of the dome. For some simulations the average linear velocity of upward flow along the flanks of the dome was 3 m/yr, possibly of large enough magnitude to cause a thermal anomaly. If perched brine plumes form by basin dewatering, the thermal buoyancy effects associated with such a thermal anomaly may make the plumes rise to depths shallower than indicated in the simulations here. The inability of the code SUTRA to simultaneously model heat and solute transport did not permit an evaluation of this.

Intragastric Balloons in Comparison With Standard Therapy for Obesity—A Randomized, Double-Blind Trial

Intragastric balloons are new but commonly used devices for the treatment of obesity; however, their safety and efficacy have not been established. We report our results of a small, double-blind, randomized trial in which the effectiveness of intragastric balloons was compared with that of conventional medical therapy for obesity. Twenty-two patients, who were 21 to 77% over ideal body weight, were studied. Eleven underwent insertion of an intragastric balloon, and 11 underwent sham procedures. One patient with a gastric balloon withdrew from the study after 3 days. Weight loss at 2 to 3 months in the conventional therapy group averaged 2.8 kg; in the balloon-treated group, the mean weight loss was 5.8 kg (P greater than 0.15). Of the 10 balloons, 8 spontaneously deflated, and 1 was passed in the stools. We noted gastric erosions in five patients and multiple gastric ulcers in one. We conclude that the intragastric balloon was not clearly effective in inducing weight loss, had a high rate of spontaneous deflation, and was damaging to the gastric mucosa. Controlled trials should be done before similar weight-reduction devices are used in routine clinical practice.

The effect of cuff pressure deflation rate on accuracy in indirect measurement of blood pressure with the auscultatory method.

The importance of cuff deflation rate in the auscultatory method of measuring blood pressure was investigated using a computer-based model. To determine the relationship between the cuff deflation rate and the measurement error, two cuff deflation protocols were used, one based on heart rate (mm Hg per heartbeat), the other on a constant rate (mm Hg per second). The different deflation protocols and rates were tested using a constant blood pressure of 120/80 mm Hg and heart rates ranging from 40 to 120 beats/min. It was confirmed that a cuff deflation rate that is time based will introduce larger errors at low heart rates. Using heart rate as a basis for cuff deflation rate yields a constant error that is independent of heart rate. The currently used standard of 3 mm Hg/s could result in a maximum error of 2.5 mm Hg in both systolic and diastolic pressures at a heart rate of 72 beats/min. The maximum systolic and diastolic errors increase to more than 4 mm Hg at 40 beats/min. A deflation rate of 2 mm Hg/beat, however, yields a maximum error of 2 mm Hg for both systolic and diastolic pressures, independent of heart rate. A cuff deflation rate based on heart rate is recommended to help minimize changes in measurement error when measuring blood pressure if a wide range of heart rates will be encountered.

Clinical experience with Heyer-Schulte inflatable implants in breast augmentation.

Following breast augmentation, 100 patients with inflatable saline implants were followed for a period of 6 months to 8 1/2 years. Capsular contracture rate, Baker II or greater, was 3.4 percent. This low rate of capsular contracture is attributed to early manipulation of the implant. The deflation rate was also 3.4 percent. The Heyer-Schulte (Mentor) inflatable implant offers an acceptable low rate of leakage to justify its continued use. It also offers an advantage in correction of asymmetries and yields softer breasts. The replacement of an occasional deflated implant does not appear to pose more than a minor nuisance nor to materially compromise the possibility of an excellent long-term result.

Effects of hypercapnia on inspiratory and expiratory muscle activity during expiration

Persistence of inspiratory muscle activity during the early phase of expiratory airflow slows the rate of lung deflation, whereas heightened expiratory muscle activity produces the opposite effect. To examine the influence of increased chemoreceptor drive and the role of vagal afferent activity on these processes, the effects of progressive hypercapnia were evaluated in 12 anesthetized tracheotomized dogs before and after vagotomy. Postinspiratory activity of inspiratory muscles (PIIA) and the activity of expiratory muscles were studied. During resting breathing, the duration of PIIA correlated with the duration of inspiration but not with expiration. Parasternal intercostal PIIA was directly related to that of the diaphragm. Based on their PIIA, dogs could be divided into two groups: one with prolonged PIIA (mean 0.57 s) and the other with brief PIIA (mean 0.16 s). Hypercapnia caused progressive shortening of the PIIA in the dogs with prolonged PIIA during resting breathing. The electrical activity of the external oblique and internal intercostal muscles increased gradually during CO2 rebreathing in all dogs both pre- and postvagotomy. After vagotomy, abdominal activity continued to increase with hypercapnia but was less at all levels of PCO2. The internal intercostal response to hypercapnia was not affected by vagotomy. The combination of shorter PIIA and augmented expiratory activity with hypercapnia might, in addition to changes in lung recoil pressure and airway resistance, hasten exhalation.

Reflex control of expiratory duration in newborn infants.

We investigated the effect on expiratory duration (TE) of application of graded resistive and elastic loads and total airway occlusions to single expirations in 9 full-term healthy infants studied on the 2nd or 3rd day of life. The infants breathed through a face mask and pneumotachograph, and flow, volume, airway pressure, and diaphragm electromyogram (EMG) were recorded. Loads were applied to the expiratory outlet of a two-way respiratory valve using a manifold system. Application of all loads resulted in expired volumes (VE) decreased from control (P less than 0.05), and changes were progressive with increasing loads. As VE became smaller, end-expiratory volume (EEV) became greater. TE, measured either from the pattern of airflow or airway pressure, or from diaphragm EMG activity, progressively increased with increasing loads and was greatest with total occlusions (P less than 0.05, compared with control). Resistive loading resulted in a greater accumulated VE history than elastic loading to the same EEV. For equivalent changes in EEV, TE was more prolonged with resistive than with elastic loading. Expiratory loading did not change the inspiratory duration determined from the diaphragm EMG activity of the breath immediately following each loaded expiration. These findings in infants are consistent with an integrative neural mechanism that modulates TE in response to the accumulated VE history, including both EEV and rate of lung deflation.

Leakage of Breast Prostheses-Reply

<i>In Reply</i>.—We were most interested to read Professor Cohen's comments. We were unable to trace any references in the literature to previous failures of this particular prosthesis, although deflation has been reported in other similar prostheses. We have now used the Varifil prosthesis in a total of 30 patients with a mean follow-up time of 30 months and a minimum follow-up time of 18 months. During this extended period there have been no further instances of either deflation or capsule formation. Thus, the significant complication rate of deflation (13%) must be judged in association with a low rate of capsule formation (13%). The judgment concerning the softer texture of the inflatable prosthesis is a clinical observation that we made when these patients were compared with patients who had silicone gel prostheses. This probably reflects the increased proportion of patients with a Baker grade I result. We would stress that

Ventilatory phase duration in the chicken: role of mechanical and CO2 feedback.

Awake upright White Leghorn roosters (Gallus domesticus) were unidirectionally ventilated. Electromyographic activity from inspiratory and expiratory muscles was recorded to demarcate inspiration and expiration. During inspiration, the rate of inflation of the air sac system was varied while the CO2 concentration of the gas passing through the lungs was maintained constant. Inspiratory duration was inversely related to the rate of inflation, producing an inspiratory volume-time threshold (VT) curve with a negative slope. When the CO2 concentration was increased in the lungs, the inspiratory VT curve shifted to the right with a concurrent increase in slope. If the rate of deflation was varied during expiration, it was found that expiratory duration was inversely related to the rate of deflation, producing an expiratory VT curve with a positive slope. Increasing the CO2 concentration shifted the curve to the left with an increased slope. These results indicate that inspiratory and expiratory phase durations are a function of both mechanical and chemical feedback.

THE OSCILLOTONOMETER IN THEORY AND PRACTICE

The accuracy of the Scala Alternans Altera oscillotonometer was investigated by comparison with direct intra-arterial pressures. It was found that the traditional criteria for detecting systolic and diastolic pressures were in error. A slow deflation rate was essential for the accurate measurement of systolic pressure, the maximum amplitude of needle oscillation correlated closely with mean pressure, and the determination of diastolic pressure was so inaccurate as to be clinically useless. The response of the oscillotonometer was also found to be dependent upon the individual combination of oscillotonometer and patient.

Geophysical events

Krafla Caldera, Mývatn Area, Iceland (65.71°N, 16.75°W). The following is a report from Karl Gronvold and Páll Einarsson.The gradual inflation after the minor December event (see SEAN Bulletin, 4 (12)) was reversed about 1 February when very slow deflation began and the earthquake activity associated with inflation stopped. As measured at the Krafla power house, the initial deflation rate of about 0.5 microradians/day increased on 7 February to about 1.3 microradians/day. In the evening of 10 February, a dense microearthquake swarm began near the S rim of the Krafla caldera and started to propagate southward. At about the same time the deflation rate increased at Krafla, reaching a maximum of 7 microradians/day on 12 February. The rate of deflation decreased gradually thereafter; on 17 February it stopped, and on 21 February inflation started again. The deflation of 40 microradians is somewhat larger than the December deflation but still only about ⅙ of the last major deflation‐rifting event in May 1979 (see SEAN Bulletin, 4 (5)).

Eolian sand deflation —A cause for gravel barrier islands in arctic Alaska?

Barrier islands in arctic Alaska are composed of sandy gravel, whereas lower-latitude barrier islands are composed of predominantly sandy material. This pronounced grain-size difference needs explanation. Because wind-winnowing of island surfaces is effective during most of the yearly cycle, while sediment supply by waves is effective for about 2 mo at most, eolian sand deflation might be a mechanism to explain the coarse sediments of arctic barrier islands. In late winter, plumes of windblown sand are found on the fast ice downwind of barrier islands. More than 300 t (tonnes) of sand were removed by wind action from one small island near Prudhoe Bay in one winter; this loss suggests a deflation rate of 2 mm for that period.

SEAN Report

After the January 6–21 deflation event at Krafla (Iceland) described in April 1978 EOS (p. 197), inflation resumed at the previous rate of 6–7 mm/d and continued through about June 10. Inflation then slowed and became irregular, as had happened shortly before most previous deflation events. Slow deflation began during the afternoon of July 10. About 3 hours later the deflation rate increased markedly, and harmonic tremor began, achieving its maximum amplitude in about 3 more hours. Earthquake activity increased, and epicenters migrated northward from the caldera, reaching an uninhabited area 10–30 km north of the caldera the next day. No eruption occurred, and no new steam fields were formed, although emission from a 1976 steam field increased substantially. The deflation rate decreased gradually July 12–13, and then inflation resumed late July 13. Deflation events at Krafla are caused by the intrusion of magma from a reservoir beneath the caldera into a fault system that extends to the north and south.

SEAN Report

The following geophysical and meteoritic events were reported by the Scientific Event Alert Network (SEAN), Smithsonian Institution, NHB Stop 129, Washington, D.C. 20560.A major deflation event at Krafla Caldera (Iceland) began January 6.The next morning, deflation rate increased, and harmonic tremor began. Earthquakes with maximum magnitude of 4.8 migrated to 30 km north of the caldera January 7 and to 10 km farther north by January 9, indicating magma injection into Krafla's northern fissure zone. Deflation and seismicity continued until January 22. Uplift then resumed but has been interrupted several times, coinciding with periods of harmonic tremor. Earthquakes, many with magnitudes greater than 4, were continuing in early February from the fissure zone. Tilt equivalent to about 110 cm of caldera subsidence was recorded during the deflation event, and up to 2 m of rifting may have occurred 25–50 km north of Krafla. However, no marked change in geothermal activity was observed, and no visible eruption occurred.

Influence of lung parenchyma on dynamic bronchial collapsibility of excised dog lungs.

The main bronchi of excised dog lobes were obstructed 5-6 cm from their origin with beads, so that they did not communicate with the peripheral air spaces. With the lobe held at constant transpulmonary pressure, bronchial pressure-volume curves were recorded during both static and dynamic bronchial deflations. This was done both before and after dissecting the obstructed bronchus free of parenchymal attachments. The parenchymal contribution on dynamic deflation was much larger than the airway contribution: dynamic bronchial compliances in intact bronchi were 58 +- 8% and 65 +- 8% of the static at dynamic rates of bronchial deflation of 14 and 8 ml/s, respectively, whereas in dissected bronchi they were 72 +- 9% and 78 +- 9%. These relationships were not influenced by changes of transpulmonary pressure applied to the lobar parenchyma. The parenchymal effect on dynamic bronchial compliance was analyzed in terms of parenchymal interdependence and bronchial stress adaptation. We concluded that the presence of lung parenchymal attachments significantly reduced dynamic bronchial collapsibility as compared to static collapsibility.

A New Type Sphygmomanometer Valve

AN IMPORTANT prerequisite for early detection of arterial hypertension is reliable measurement of the resting blood pressure. General precautions necessary for proper registration of blood pressure relate to the patient, the examiner, and the instrument.1One caveat is the importance of a relatively uniform rate of cuff deflation. The optimal rate of deflation has not been determined but seems to be somewhere between 2 and 5 mm Hg/sec.1-3 Personal experience as well as observation of others indicates that most conventional sphygmomanometer valves are sticky, and the desired rate and uniformity of deflation are practically impossible to attain. The purpose of this report is to describe a new sphygmomanometer valve that permits a predetermined rate of cuff deflation. The Valve The valve is shown in Fig 1. Operation is simple, depending on depression and release rather than rotation, as in the conventional valve. Depression of the push button opens