Two-way Valve Research Articles

Salmeterol provides prolonged protection against exercise-induced bronchoconstriction in a majority of subjects with mild, stable asthma

In patients with asthma, exercise-induced symptoms are well recognized and frequently limiting. Currently available β 2-receptor agonists have a short duration of action and breakthrough symptoms may occur. We studied the efficacy of the recently developed long acting inhaled β 2-agonist salmeterol with respect to protection against exercise-induced bronchoconstriction. Twelve patients with mild to moderate, stable asthma were recruited (age range 21–33 years). They each underwent treadmill exercise tests, with target heart rate of approximately 90% of predicted maximu, 1, 6 and 12 h after a single dose of salmeterol 50 μg, salbutamol 200 μg and placebo. Patients breathed through a two-way valve, inspiring dry air from a compressed air cylinder via a Douglas bag to maintain constant humidity. The primary efficacy variable analysed was the maximum percentage fall in FEV 1 and FVC from pre-exercise readings within the first 30 min post-exercise. At 1 h post-dose there was significant protection in terms of fall in mean ± sem FEV 1 in response to exercise challenge after either salmeterol (0·83 ± 6·2%) or salbutamol (3·8 ± 5·5%) as compared with placebo (27·1 ± 7·3%). At 6 h post-dose, fall in FEV 1 on salmeterol was 11·3 ± 3·8% as compared with salbutamol, 28·0 ± 5·7% and placebo, 32·0 ± 7·0%. At 12 h post-dosing there was still significant protection in terms of fall in FEV 1 in the salmeterol treated group, 12·8 ± 4·9%, as compared with salbutamol, 28·7 ± 4·9% and placebo, 25·4 ± 7·3%. Similar results were found with respect to changes in FVC in these patients. We conclude that salmeterol is effective in protecting against exercise-induced bronchoconstriction in the majority of subjects with mild, stable asthma and that this effect lasts for at least 12 h.

The Influence of Semi-Empirical Control Valve Model Parameter Accuracy on Simulated Hydraulic System Responses

A parameter sensitivity analysis method is applied to an investigation of the importance of the identification accuracy of the parameter values describing the steady-state and dynamic behavior of three commonly used fluid power circuit components, i.e., single-stage pressure relief, reducing, and two-way flow control valves. The component models are verified; these semi-empirical models take into account the most important continuous and discontinuous nonlinearities.

Measurement of alveolar gas mixing in mechanically ventilated patients.

To evaluate a computer-based, real-time, multibreath nitrogen washout technique in mechanically ventilated patients, incorporating an in-line flow measurement device to measure functional residual capacity and two indices of gas mixing, ventilatory efficiency, and alveolar mixing efficiency. ICU, Charing Cross Hospital, London. Within-patient reproducibility of a multibreath nitrogen washout technique. Seven intubated patients requiring mechanical ventilation. One patient completed two sets of readings. Patients were connected to a pneumatically driven ventilator fitted with a switching device to be operated either by an appropriate oxygen-nitrogen mixture or equivalently blended oxygen-argon mixture. An inspiratory-expiratory, two-way valve was attached to the delivery port of the ventilator, with a pneumotachograph for flow measurement and a gas sampling probe for gas concentration measurement in line with the patient's endotracheal tube. The analog signals were digitized and handled by a microcomputer. No significant differences were found for any index, with coefficients of variation of 1.5%, 2.9%, and 2.1% for functional residual capacity, ventilatory efficiency, and alveolar mixing efficiency, respectively. This method gives excellent reproducibility for biological measurements in a clinical setting and shows that these measurements can readily be made on mechanically ventilated patients.

Flexible Semi-Empirical Models for Hydraulic Flow Control Valves

Low-order nonlinear models for proportional two-way and simple three-way flow control valves are developed and subjected to experimental verification. The models are postulated in the semi-empirical manner, trying to overcome the most typical problems in modelling fluid power valves, e.g., the influence of constructional differences and the difficulty of identifying the parameter values.

High Pressure Percutaneous Transtracheal Ventilation

Percutaneous transtracheal ventilation using a large gauge intravenous-type catheter can be used successfully in the setting of complete upper airway obstruction in animals. In this study, using a large animal model, satisfactory oxygenation and ventilation was achieved by inversely varying the catheter size and the inspiration to expiration ratio (I:E). Specifically, 30 to 63 kg ruminants with an obstructed upper airway were resuscitated for 30 minutes from a hypoxic, hypercarbic, and acidotic state using 12- and 14-gauge catheters connected to a 50 psi oxygen source via a two-way valve with an I:E of 1:4 and 1:9 seconds, respectively. Shorter expiratory time or increased inspiratory time with these intravenous catheters resulted in significant hemodynamic compromise, barotrauma, inadequate carbon dioxide elimination, acidemia, and frequent death.

An improved method for recording blood pressure in the tethered monkey

Existing tethering systems intended for continuous recording of blood pressure incur two major problems: 1) vertical movements of the animal in the cage produce a significant error in measured pressure introduced by the change in distance between the pressure transducer and the highest point of the infusion system and 2) the necessity for repeated zero adjustment of the pressure transducer requires sedation of the animal and disconnection of the catheter. Continuous infusion and a one-way valve in the infusion line in proximity to the pressure transducer will eliminate the error of measurement related to vertical movement of the animal. A remotely controlled, two-way solenoid valve can close the catheter line and open the pressure transducer to atmospheric pressure, thereby permitting repeated zero adjustment without sedation of the animal and disconnection of the catheter. Eliminating the need to disconnect the catheter will significantly reduce the risk of adventitious infection.

High pressure percutaneous transtracheal ventilation: The use of large gauge intravenous-type catheters in the totally obstructed airway

Percutaneous transtracheal ventilation using a large gauge intravenoustype catheter can be used successfully in the setting of complete upper airway obstruction in animals. In this study, using a large animal model, satisfactory oxygenation and ventilation was achieved by inversely varying the catheter size and the inspiration to expiration ratio (I:E). Specifically, 30 to 63 kg ruminants with an obstructed upper airway were resuscitated for 30 minutes from a hypoxic, hypercarbic, and acidotic state using 12- and 14-gauge catheters connected to a 50 psl oxygen source via a two-way valve with an I:E of 1:4 and 1:9 seconds, respectively. Shorter expiratory time or increased inspiratory time with these intravenous catheters resulted in significant hemodynamic compromise, barotrauma, inadequate carbon dioxide elimination, acidemia, and frequent death.

Two-way valve mucus extractor prevents operator infection

Two-way valve mucus extractor prevents operator infection

Vascular access in gynecologic cancer using the Groshong right atrial catheter

From December 1986 through July 1987, forty-one Groshong catheters were inserted in 38 patients with invasive gynecologic cancer for a cumulative total of 4170 days of patient use. (mean catheter indwelling time: 93 days; range: 3–300 days). A supraclavicular approach was used to cannulate the brachiocephalic vein in 31 patients. In 6 patients, the subclavian vein was cannulated via an infraclavicular approach, while 4 patients had the catheters placed via external jugular venous cutdown. Thirty-seven catheters were inserted at the bedside without fluoroscopy using the Seldinger technique and a peel-away catheter introducer sheath. A chest x-ray was used to confirm the right atrial position of the catheter. Major complications included two pneumothoraces, and three catheter-related cases of sepsis. A unique feature of the Groshong catheter is a pressure-sensitive two-way valve at the intravascular end, minimizing the potential for air embolism and back-bleeding. This eliminates the need for a heparin flush or external clamping, but permits blood sampling. Catheter insertion and maintenance procedures at bedside are simple, time saving, and cost effective. With the increasing use of continuous chemotherapy infusion protocols, use of vesicant drugs, hyperalimentation, and the need for outpatient therapy, we recommend early placement of the Groshong catheter in the oncology patient.

VALVISTOR BASED MODERN SERVO PACKAGE

Cartridge valve technology offers solutions in the situations where high integration level of hydraulic components are needed, like in the case of linear servo-packages. Valvistor, which is often regarded as a hydraulic transistor, is one of the most modern two-way cartridge valve designs both from the standpoint of the package integration level and the static and dynamic characteristics. In this paper, mathematical and experimental studies are made concerning the application of Valvistor in control of a differential cylinder. In addition, an example of an advanced construction of intelligent actuator is shown both from the standpoint of component packaging and control.

Control of inspiratory duration in premature infants.

We used single-breath mechanical loads and airway occlusions in premature infants to determine whether maturation influences the reflex control of inspiratory duration. We measured flow, volume, airway pressure, and surface diaphragmatic electromyogram (EMG) in 10 healthy preterm infants [33 +/- 1 (SD) wk gestation], 2-7 days of age. Three resistive and two elastic loads and occlusions were applied to the inspiratory outlet of a two-way respiratory valve. Application of all loads resulted in inspired volumes significantly decreased from control (P less than 0.001), and these decreases were progressive with increasing loads. Inspiratory duration (TI) was prolonged from control by all loads and occlusions when measured from the diaphragmatic EMG (neural TI) and by all but the smaller elastic load when measured from the flow tracing (mechanical TI). Similar decreases in inspired volume at the end of neural TI produced by application of both elastic and resistive loads resulted in comparable prolongation of neural TI. In contrast, for comparable volume decrements, resistive loading prolonged mechanical TI more than elastic loading (P less than 0.001). Mechanical and neural TI values of the breath after the loaded breath were unchanged from control values. Comparison of the neural volume-timing relationship in premature infants with our data in full-term infants suggests that the strength of the timing response to similar relative decrements in inspired volume is comparable. We conclude that reflex control of neural TI in premature infants depends on the magnitude of inspired volume and is independent of the volume trajectory.(ABSTRACT TRUNCATED AT 250 WORDS)

Programmable pneumatic generator for manipulation of intrathoracic pressure.

The determination that blood can move during cardiopulmonary resuscitation because of imposed changes in intrathoracic pressure has led to the construction and testing of mechanical devices for increasing intrathoracic pressure fluctuations over those obtained by manual means. These mechanical systems have required high-pressure ventilation simultaneous with compression of the chest to augment blood flow. Their usefulness has been limited, however, because of the requirement for endotracheal intubation and complex devices. Similar systems have also been used to generate intrathoracic pressure changes timed to the cardiac cycle to aid the failing, but beating, heart. A system was developed that can produce high intrathoracic pressure without simultaneous ventilation by using a vest that is placed around the thorax. The vest contains a bladder that is rapidly inflated and deflated by the programmable pneumatic generator. Air flows into and out of the bladder by the proper sequencing of large-bore three-way and two-way solenoid valves that are connected in series. A microcomputer-based controller is used to sequence the valves. The programmable pneumatic generator inflates the bladder more rapidly and to higher pressures than previous systems. The programmable pneumatic generator has been used in studies of cardiopulmonary resuscitation (heart arrested) and circulatory assistance (heart beating, but function depressed).

Expiratory volume clamping: a new method to assess respiratory mechanics in sedated infants.

During breathing under sedation via a two-way valve, airflow (V), volume (delta V), and airway pressure (P) were recorded in eight normal (N) infants, seven with reversible obstructive airway disease (ROAD), and seven with chronic lung disease (CLD). Intermittently, expiratory volume clamping (EVC) was applied, involving selective occlusion of the expiratory valve for three to five breaths. The latter produced cumulative increases in delta V that, due to progressive recruitment of the Hering-Breuer reflex, were accompanied by increasing expiratory plateaus in P (i.e., apneas). The resultant passive inflation delta V-P relationships were closely approximated by the expression: delta V = aP2 + bP + c, wherein a represented the pressure-related changes in chord compliance (Crs), b the Crs at P = 0, and c the difference between the dynamic end-expiratory and relaxation volumes of the respiratory system. Relative to N, the ROAD and CLD infants had significantly reduced weight-specific values of a/kg, their b/kg values were increased, whereas the c/kg measurements did not significantly vary. Moreover, for each subject we determined the net Crs/kg obtaining at P = 20 cmH2O (i.e., Crs20/kg), an estimate of the net deflation compliance; the passive respiratory time constant (tau rs) based on the slope of the expired delta V/V relationship; and the respiratory system conductance (Grs/kg). Relative to N, the mean Crs20/kg was significantly reduced only in the infants with CLD and, due to increases in tau rs, both patient groups depicted significantly diminished values of Grs/kg, suggesting the presence of airways obstruction.(ABSTRACT TRUNCATED AT 250 WORDS)

A gradient valve for HPLC

A novel concept of a low-pressure single gradient mixing pump is described. The solvents are mixed via a two-way switching valve of special design. Due to a mechanical transmission between the pump piston and the gradient valve rotor, the precise partitioning of the both liquids is achieved regardless of a nonlinear piston refill period. The use of this concept has no limitations for specially constructed pumps equipped with stepping motors and with position encoders for piston displacement. For isocratic elution with mixed solvents it is possible to set manually any binary composition without the need of any additional accessory.

97 Influence of carbohydrate on leucin oxidation in newborn infants measured with the 13C-leucin breath test

The 13C-leucin (L) breath test (LBT) measures leucin oxidation (LO) in vivo and can be used to investigate the metabolic role of branched chain amino acids in newborn infants: To study the influence of metabolic conditions on in vivo LO, especially its dependence on concomitant carbohydrate (C) intake, twelve LBT were performed in 5 infants at an age of 4 to 21 days, whose birth-weights ranged from 1050 to 2800 g at gestational ages of 31 to 37 weeks. 3 infants were fed orally on a standard formula diet (180 ml/kg/day), a pair of twins was tested twice while receiving a standardized mixed oral and parenteral nutrition, the only difference between tests I and II being the C content of the infusion (2.7 vs 7.3 mg/kg/min). After a bolus injection of 1 to 5 mg/kg L, breath samples for a 5 hr period were collected at 15 to 30 min intervals into plastic bags by means of a mask with a two-way valve. The 13CO2/12CO2, ratio of expired air, analyzed by ratio-MS, increased significantly with a peak at 20 - 30 min (Δδ from 5.6 to 18.9 ‰), and the 5 hr LO was found to vary very little in repeated tests under steady nutritional conditions(LO = 21.7 - 22.5 %). In the twins, the lower C infusion rates were correlated with higher LO (23.9 vs 18.6 %).Conclusions: L-oxidation in newborns can reliable be measured by a LBT. The balance between LO and protein synthesis is influenced by nutritional factors like C-availability.

On-line computer estimation of carbon dioxide response curves.

Anesthesiologists are concerned with the effect of various anesthetics on a patient's central nervous ventilatory control. The most widely accepted method of determining the effect of a drug is to compare carbon dioxide response curves (delta VE/delta PETCO2, where VE = minute ventilation [in L/min] and PETCO2 = end-tidal carbon dioxide [in mm Hg]) measured before and after administration of the drug. Additional information concerning neuromechanical control can be obtained by also including a measure of the airway occlusion pressure (generally measured 100 ms after occlusion, i.e., P100). To facilitate these measurements we have developed a portable, computer-controlled data acquisition system. It includes an Apple II+ computer and measures VE, PETCO2, and P100. Each subject rebreathes exhaled carbon dioxide through a two-way breathing valve attached to a 9-liter reservoir, which is initially filled with 5% carbon dioxide and balance oxygen. Exhaled carbon dioxide concentrations are measured with an infrared medical gas analyzer on samples taken through a catheter connected at the mouthpiece. The exhaled flow is measured with a pneumotachograph in conjunction with a differential pressure transducer, and P100 is determined with a Validyne MP45 pressure transducer.

Reflex control of inspiratory duration in newborn infants.

We applied graded resistive and elastic loads and total airway occlusions to single inspirations in six full-term healthy infants on days 2-3 of life to investigate the effect on neural and mechanical inspiratory duration (TI). 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 inspiratory outlet of a two-way respiratory valve using a manifold system. Application of all loads resulted in inspired volumes decreased from control (P less than 0.001), and changes were progressive with increasing loads. TI measured from the pattern of the diaphragm EMG (TIEMG) was prolonged from control by application of all elastic and resistive loads and by total airway occlusions, resulting in a single curvilinear relationship between inspired volume and TIEMG that was independent of inspired volume trajectory. In contrast, when TI was measured from the pattern of airflow, the effect of loading on the mechanical time constant of the respiratory system resulted in different inspired volume-TI relationships for elastic and resistive loads. Mechanical and neural inspired volume and duration of the following unloaded inspiration were unchanged from control values. These findings indicate that neural inspiratory timing in infants depends on magnitude of phasic volume change during inspiration. They are consistent with the hypothesis that termination of inspiration is accomplished by an "off-switch" mechanism and that inspired volume determines the level of vagally mediated inspiratory inhibition to trigger this mechanism.

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.

Ｂｌｏｍ‐Ｓｉｎｇｅｒ Ｖｏｉｃｅ ＰｒｏｓｔｈｅｓｉｓおよびＴｒａｃｈｅｏｓｔｏｍａ Ｖａｌｖｅの使用経験

In 1980 Singer and Blom introduced a one-way silicone valve which allows for sufficient air flow from the trachea to the oral cavity. Eventually they described two-way respiratory valve with the voice prosthesis by which voice can be produced without occlusion of the stoma by a finger. After their introductory report, many authors reported a clinical application of these two devices.We have started clinical application of these two devices since 1983. The present paper describes our experience with the Blom-Singer voice prosthesis and the tracheostoma valve, together with our surgical technique for tracheoesophageal puncture. Nine patients were included in this study. The main problems for the voice prosthesis are irritation of the skin and displacement of the tracheoesophageal shunt. The limitation of the application for the tracheostoma valve was caused by irritation of the skin and the excessive secretion of the trachea.There is no major complication with the tracheoesophageal puncture. The results of this method are satisfactory to sure extent, and we need more cases in order to evaluate this method exactly.

A new gas sampling device for gas chromatography

This paper describes a new sampler for taking gaseous samples for gas chromatographic analysis. The device provides samples of precise and selectable volume and can be used in place of conventional sampling valves. It has an advantage over conventional samplers in that it has no moving parts in the sample path. It can be constructed in any material that can be made in the form of pipes, this includes silica, glass, gold etc., so that it is suitable for labile compounds. The only moving part in the system is a two-way valve remote from the sampler and in the carrier gas supply. The design is such that the sample size is not sensitive to the temperature of the sampler, consequently the sampler can be used in high and variable temperature situations such as inside furnaces and reaction vessels. The sample size is selected remotely through a timer. This permits easy change of sample size and calibration of the gas chromatograph. The principles of operation and the mathematical theory are developed to show the theoretical limits within which precise repeatable samples can be taken. Experimental results are presented to show good agreement with the theory and to illustrate that the precision of sampling under a variety of conditions is as good or better than modern gas sample valves.