Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “High-Frequency Ventilation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed1992

High frequency oscillation.

The current state of high frequency oscillation (HFO) in Japan is reviewed. The discussion is focused on the following: (i) the repeated application of short duration SI (sustained inflation) is effective in recruiting lung volume and increasing PaO2; (ii) HFO can prevent the formation of granulocytes related to lung injury; and (iii) HFO does not increase the risk of severe complications such as air leaks, bronchopulmonary dysplasia or intraventricular hemorrhage.

Animals↗
PubMed1992

Effect of mean airway pressure on bronchial mucosal blood flow in rabbits with oleic acid-induced injury.

The effects of mean airway pressure (MAP) on bronchial mucosal blood flow at the carina in nine anesthetized adult rabbits undergoing high frequency ventilation were studied. The animals were given oleic acid to diminish lung compliance and to exclude the influences of increasing MAP on systemic venous return. Mucosal blood flow decreased significantly when MAP exceeded 14 cmH2O. Mucosal blood velocity tended to decrease as higher levels of MAP were applied. Mucosal blood volume decreased significantly when MAP exceeded 20 cmH2O. Hemodynamics, arterial blood gas values and pH were not changed significantly. Our data demonstrate that bronchial mucosal blood flow decreases at high levels of MAP even if cardiac output remains constant. Hence this decrease of bronchial mucosal blood flow may be due to the transmission of pressure to submucosal bronchial capillaries.

Animals↗
PubMed1992

Effects of high-frequency pressure waves applied to upper airway on respiration in central apnea.

We examined the effects of high-frequency (30-Hz) low-pressure oscillations on respiration in nine patients with central sleep apnea. All patients were studied during sleep and wore a nasal mask through which the oscillations were applied. All tests were performed during periods of repetitive central apneas. Respiratory efforts were monitored from the airflow and calibrated Respitrace signals. After several cycles of apnea were monitored, the oscillatory pressures were applied for brief periods (less than 5 s) at the midpoint of the central apneas. All trials in which arousal occurred were discarded, leaving a total of 106 trials in the nine patients. High-frequency oscillation of the upper airway stimulated respiratory effort(s) in 68% of all trials (72 of 106). Apnea length was significantly shortened in four of the nine patients. In one patient with a tracheostomy, the stimulus applied to his isolated upper airway evoked respiratory efforts during central apnea in 13 of 15 trials. We conclude that high-frequency oscillatory pressures applied to the upper airway can stimulate respiratory efforts during central apnea. This response may be mediated by upper airway receptors involved in nonrespiratory airway defense reflexes and may have implications in the treatment of patients with central sleep apnea.

Adult↗
PubMed1992

[High frequency "bubble" oscillation ventilation in the neonatal period].

The authors tested their own high frequency, oscillation, "bubble" ventilator on a model of neonatal lungs in vitro and in vivo. They used the effect of oscillations which develop when through fluid (in vivo water) a mixture of air is bubbled and which can be, if the expiration tube is sufficiently rigid, transmitted back into the lungs. If the CPAP circuit is suitably arranged, it can ensure an adequate exchange of blood gases. The authors found marked changes in the amplitude of pressure oscillations as well as of the frequency in relation to the shape of the ending beneath the fluid surface (greatest when a funnel with a 30 mm diameter and 90 degree angle in relation to a normal line projected on the water surface is used). They found that the compliance (C) has no substantial effect on the amplitude nor on the frequency of oscillations. The mentioned bubble system approached as to its efficiency the commercial oscillation ventilator Stephen 3000 SFH and was used in the therapy of respiratory failure in three neonates with body weights of 1250-2700 g. The authors conclude that high frequency oscillation "bubble" ventilation is a cheap, safe and highly effective therapy which can be used in any department providing care of neonates even during transport.

High-Frequency Ventilation↗
PubMed1976

Renal function in experimental chronic hydronephrosis. V. Net acid excretion capacity in relation to renal pelvic volume after maximal loading with NH4Cl.

In 12 mongrel dogs intravenous loading with ammonium chloride (4 mmol NH4+/kg body weight) was performed before and 2-9 weeks after unilateral hydronephrosis had been produced by ligation of the ureter over an indwelling catheter. In an attempt to satisfy the demand for adequate, constant, alveolar ventilation a special respirator of the high-frequency positive-pressure ventilation (HFPPV) type was used. The acid-base status of the blood was determined before and after the loading and the acidification capacity of each kidney was assessed by measuring the amount of titratable acid and ammonium ions excreted in the urine. In the hydronephrotic kidney the excretion of both titratable acid and ammonium ions was statistically significantly reduced, both compared with the initial values in session I and compared with the healthy kidney in session II. After additional loading with ammonium chloride in session II, however, both kidneys increased their excretions to approximately similar extents. When the excretion was calculated per ml glomerular filtrate, no statistically significant changes were found between sessions I and II, either for the intact or the hydronephrotic kidney. The renal pelvic volume on the hydronephrotic side was measured and related to the reduction of the capacity of the kidney to excrete titratable acid and ammonium ions. No statistically significant correlation was obtained.

Acid-Base Equilibrium↗
PubMed1979

New parachute cuff and positive end-expiratory pressure to minimize tracheal injury and prevent aspiration.

A new parachute cuff has been tested in combination with a positive end-expiratory pressure (PEEP) on mongrel dogs. During positive-pressure ventilation the intracuff and intratracheal pressures showed synchronous, identical pressure variations, and therefore theoretically with this type of cuff the pressure against the tracheal wall would be minimal. The cuff provided a seal against gas leakage from the lungs throughout the entire test period, i.e., for up to 7 h. To avoid aspiration of mouth contents during the passive exhalation phase, different amounts of PEEP were tested. A PEEP of 4.0--8.0 cm H2O always produced a seal against a column of fluid in the mouth exerting a hydrostatic pressure of 5.4--8.8 cm H2O against the cuff. This seal was maintained during the whole test period. No difference in sealing capacity was found when the cuff was used with a normal respiratory frequency (20/min) and with high-frequency positive-pressure ventilation (60/min). When the PEEP is eliminated, e.g., when the respirator is disconnected for suction of the endotracheal tube, the sealing effect will be abolished. As the cuff extends up into the larynx there will be no pooling of fluid above the cuff. The risk of aspiration can therefore be diminished by suction of oral cavity before disconnecting the respirator. With the use of the pneumatic valve principle together with high-frequency positive-pressure ventilation, an open respirator system can produce a continuous PEEP, thereby preventing aspiration even during suctioning of the tracheal tube.

Animals↗
PubMed1992

Laryngospasm during transtracheal high frequency jet ventilation.

A 74-year-old woman developed severe cardiovascular depression during percutaneous transtracheal high frequency jet ventilation for laser surgery of the epiglottis. This was found to be caused by acute airway obstruction secondary to severe laryngospasm. We recommend profound neuromuscular blockade during percutaneous transtracheal jet ventilation, in order to prevent this complication.

Aged↗
PubMed1992

[Transtracheal jet ventilation in the operating room].

For the last 40 years transtracheal ventilation has been suggested as a means of bypassing the glottis in emergency in patients unable to be intubated or ventilated by mask. A catheter has been designed to be easily inserted into the crico-thyroid membrane. The outer part of the device, with its dual attachment system, can be connected to conventional resuscitation equipment by its 15 mm male end or to a high-pressure oxygen source by its Luer-Lock fitting. The advantages of transtracheal ventilation are: a clear vision of the operative field, a good gas exchange, an elimination of airway trauma from intubation, a reduction of the hazard of airway fires and a decreased risk of aspiration of blood and debris. Barotrauma is the main danger. However, this method of providing oxygen and/or mechanical ventilation may be extended to the postoperative period, the exit of the insufflated gas mixture being assured at all times.

Anesthesia, Inhalation↗
PubMed1991

Removal of a laryngeal foreign body using high frequency jet ventilation.

Aspiration of a foreign body into the respiratory tract is a common and serious accident in childhood. Laryngotracheal foreign bodies, although less common than bronchial foreign bodies, are potentially more dangerous. Removal is commonly achieved using a rigid ventilating bronchoscope. We report a 16-month-old boy who had an open safety pin impacted in his larynx. This was removed through a tracheostomy, using high frequency jet ventilation to maintain gaseous exchange. We believe that this is the first case in which this method of removal has been reported.

Bronchoscopy↗
PubMed1992

Elective transtracheal jet ventilation for bronchoscopic removal of tracheal foreign body.

We have shown that transtracheal jet ventilation can be used safely and effectively when removing a foreign body from the airway. In some cases, it may be wise to choose this method of ventilation initially, thus avoiding the difficulties associated with more conventional modes of controlled ventilation. This is especially true when the potential for loss of the airway during the procedure is significant. This technique also allows the bronchoscopist the benefit of unimpeded access to the airway and adequate uninterrupted time for his operative procedure.

Bronchoscopy↗
PubMed1977

Physiologic evaluation of the HFPPV pneumatic valve principle and PEEP. An experimental study.

In experiments in dogs the ventilatory and circulatory conditions prevailing with the ventilatory pattern in high-frequency positive-pressure ventilation (HFPPV) were investigated with use of a pneumatic valve principle and a ventilator system of an "open" character. Keeping the gas input constant the importance of insufflation frequency and insufflation time and the reactions to various levels of positive end-expiratory pressure (PEEP) were investigated in terms of changes in arterial pH, Pco2 and Po2. With the volumes of delivered gas kept constant, an increasing insufflation frequency from 60 to 100 per min gave a parallel decrease in tidal volume accompanied by lower maximum intratracheal pressures and a significant decrease in alveolar ventilation. Also taking into account the possibilities of inducing a suppression of the spontaneous respiration, higher ventilatory frequencies than 60 per min do now seem to introduce any further advantages. Including the associated effects on cardiac output and venous admixture, the cardio-pulmonary and circulatory parameters studied did not show any substantial changes with PEEP levels below 7.5--10 cm H2O. Thus the level of PEEP, which often is part of the ventilatory pattern in HFPPV, does not seem to have any untoward influence on the circulation (stroke volume, cardiac output, total peripheral vascular resistance) and oxygen transport (arterial oxygen content and oxygen flux) in normovolaemic dogs.

Animals↗
PubMed1992

High-frequency flow interruption in the rescue of preterm infants with severe RDS.

High-frequency flow interruption (HFFI) was used successfully to rescue three preterm infants with severe respiratory distress syndrome (RDS) whose clinical condition continued to deteriorate while on the conventional mechanical ventilation. Had the HFFI not been used, the survival chances might have been 25 per cent for Case 1 and 2, and 45.5 per cent for Case 3. A dramatic, immediate, and sustained improvement in ventilation and oxygenation was demonstrated once the critical frequency and amplitude of HFFI were established. Bronchopulmonary dysplasia which was already evidenced in one infant before the HFFI attempt was detected in two infants. This study demonstrates that HFFI is capable of achieving adequate gas exchange and improving survival in infants with severe RDS.

Carbon Dioxide↗
PubMed1975

Step changes in end-tidal CO2: methods and implications.

A dynamic end-tidal forcing technique for producing step changes in end-tidal CO2 with end-tidal O2 held constant independent of the ventilation response or the mixed venous return is introduced for characterizing the human ventilation response to end-tidal CO2 step changes for both normoxic (PAO2 = 125 Torr) and hypoxic (PAO2 = 60 Torr) conditions. The ventilation response approaches a steady state within 5 min. In normoxia, the on-transient is faster than the off-transient, presumably reflecting the action of cerebral blood flow. The hypoxic step response is faster than the normoxic response presumably reflecting the increased contribution from the carotid body. The delay in the ventilation response after the change in end-tidal CO2 is less in hypoxia than in normoxia and reflects the action of a transport delay and that of a virtual delay. These delays are interpreted with respect to the high-frequency phase shift data for the same subject, generated using sinusoidal end-tidal forcing. The methods of others for experiments utilizing step changes in inspired CO2 are considered with respect to our methods.

Adult↗
PubMed1976

A high-frequency ultrasonic nebulizer system for radioaerosol delivery.

A prototype high-frequency ultrasonic nebulizer, coupled with a nebulization chamber, has been designed specifically to overcome the problem of inefficient and unpredictable radioaerosol delivery. The objective was to reduce mean particle size, increase aerosol concentration, and minimize dead space. Thirty-nine patients were studied, including 15 patients in significant respiratory distress. Delivery of the radioaerosol proved to be rapid, efficient, and reproducible, and excellent alveolar distribution patterns were obtained in all 39 patients. Minimal nonpathologic tracheal deposition occurred in five patients, but this did not interfere with the interpretability or diagnostic validity of the study. All other instances of airway aerosol deposition correlated with documented airway disease. The images obtained with this system are a reliable measure of ventilatory distribution and airway tubulence.

Aerosols↗
PubMed1992

Spectral analysis of sympathetic discharge, R-R interval and systolic arterial pressure in decerebrate cats.

In 19 decerebrate and artificially ventilated cats, we analyzed, with a power spectral methodology, the variability simultaneously present in R-R interval and in thoracic preganglionic sympathetic outflow. R-R interval was characterized, as already described in humans and other experimental preparations, by two rhythmic components occurring at a frequency of about 0.1 Hz (low-frequency, LF) and at one corresponding to respiratory rate (high-frequency, HF) which, in these experiments, was set at 0.32 Hz. Two similar rhythmic components were also present in the sympathetic discharge. Arterial pressure changes were produced by aorta or vena cava flow obstruction in order to produce reflex responses in sympathetic activity. Reflex sympathetic excitations induced an increase in the LF component of both R-R interval and sympathetic discharge variabilities, while the HF components were simultaneously reduced. In contrast, reflex sympathetic inhibitions were accompanied by a decrease in LF components of both variability signals, while the HF components were simultaneously increased. A significant and positive correlation was found between changes in impulse activity and the amplitude of LF component of either R-R interval or sympathetic discharge variabilities. These data support the hypothesis that the low-frequency component of R-R variability can be used as a marker of sympathetic modulation.

Animals↗