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At least 19 recordsLinked to original sources
PubMed1998

Air pressures developed beyond the apex from drying root canals with pressurized air.

Air introduced into tissues during invasive procedures can be harmful. Endodontic treatment is not frequently associated with this phenomenon, but serious results can occur if air forced into tissues impinges on critical anatomical structures and/or carries infection into deeper areas. Extracted teeth were connected to a pressure gauge during and after canal instrumentation and pressures measured. Also, a fresh porcine jaw was instrumented in the presence of a radiopaque tracer during air drying. Significant pressures were detected beyond the apex of the roots, especially with root apical diameters of file sizes larger than 20.

Air Pressure↗
PubMed1995

Oral air pressure and nasal air flow rate on levator veli palatini muscle activity in patients wearing a speech appliance.

This study was designed to determine if levator veli palatini muscle activity can be elicited by simultaneous changes in oral air pressure and nasal air flow when a speech appliance is in place. The speech appliances routinely worn by 15 subjects were each modified experimentally by drilling a hole in the vertical center of the pharyngeal bulb. The air flow rate into the nasal cavity through the opening in the bulb was altered by changing the circular area of the opening in the bulb from the occluded condition (Condition I), to circular area of 12.6 mm2 (4 mm in diameter; Condition II), and then to 38.5 mm2 (7 mm in diameter; Condition III). Electromyographic activity was measured from the levator veli palatini muscle with changes in nasal air flow rate and oral air pressure. Levator veli palatini muscle activity was correlated with changes in nasal air flow and oral air pressure. Increases in levator veli palatini muscle activity were associated with increases in nasal air flow rate compared to oral air pressure changes. The results indicated that aerodynamic variables of nasal air flow and oral air pressure might be involved in the neural control of speech production in individuals wearing a speech appliance, even if the subjects exhibit velopharyngeal incompetence without using a speech appliance. Also, the stimulating effect of bulb reduction therapy on velopharyngeal function might be achieved through the change in aerodynamic variables in association with the bulb reduction.

Adolescent↗
PubMed1997

Pressure relief characteristics in alternating pressure air cushions.

In this study a computerised system was used which continuously measured air pressure, interface pressure and pressure-time cycle characteristics of an alternating pressure air cushion (APAC), and calculated the time the interface pressure remained below three chosen thresholds of 20, 40 and 60 mm Hg. Ten healthy volunteers were used to evaluate the pressure relieving characteristics of four APACs. Results indicated significant differences between products when the threshold periods were analysed, showing some devices were not capable of relieving interface pressures below 20 mm Hg. Though deflation pressure decreased to nearer zero, interface pressure did not follow suit.

Adult↗
PubMed1984

Oronasal fistulas, intraoral air pressure, and nasal air flow during speech.

Aeromechanical data are presented for six patients with oronasal fistulas and one with a maxillary cleft. Patients were studied with the defects open and again with them closed with either acrylic dental appliances, dental wax, or denture adhesive. Only the largest openings appeared to allow sufficient loss of intraoral air pressure to weaken obstruent consonants. All but the smallest of the defects were associated with nasal air flow during syllable strings. Thus the data are compatible with a hypothesis that in the presence of small air leaks patients maintain sufficient intraoral air pressure for accurate consonant production. Presumably this is achieved by increase in respiratory effort. The relationship between fistula size and speech or speech related variables appears to be similar to that between area of the velopharyngeal opening and speech. However, the fistula is more constant in area across utterances than is the pathological velopharyngeal mechanism.

Adolescent↗
PubMed1986

Intraoral air pressure and oral air flow under different bleed and bite-block conditions.

Intraoral pressures and oral flows were measured as normal talkers produced /p lambda/ and /si/ under experimental conditions that perturbed the usual aeromechanical production characteristics of the consonants. A translabial pressure-release device was used to bleed off intraoral pressure during /p/. Bite-blocks were used to open the anterior bite artificially during /s/. For /p/, intraoral pressure decreased and translabial air leakage increased as bleed orifice area increased. For /s/, flow increased as the area of sibilant constriction increased, but differential pressure across the /s/ oral constriction did not vary systematically with changes in its area. Flow on postconsonantal vowels /lambda/ and /i/ did not vary systematically across experimental conditions. The data imply that maintenance of perturbed intraoral pressure was more effective when compensatory options included opportunity for increased respiratory drive and structural adjustments at the place of consonant articulation rather than increased respiratory drive alone.

Adult↗
PubMed2004

Finding the optimal setting of inflated air pressure for a multi-cell air cushion for wheelchair patients with spinal cord injury.

Pressure distribution patterns of the seating interface on the multi-cell air cushion (ROHO High Profile) of 36 adults with spinal cord injury (SCI) (Neurological level Th3 -L1) were measured at different air pressure levels by a pressure mat measurement system. Stress distribution relative to the inflated air pressure in the air cushion on the patients' wheelchairs was analyzed to determine the appropriate inflated air pressure of the cushion for patients. The maximum pressure points in all subjects were at the areas of the ischial tuberosities (82 to 347 mmHg). The optimal reduction in interface pressure at the ischial tuberosities was obtained just before bottoming out. The cushion air pressure at that point was between 17 and 42 mmHg, and correlated well to body weight (r = 0.495, P = 0.0021). In contrast, the maximum pressure levels did not correlate to body weight or the Body Mass Index (BMI). Pressure at the ischial area could be reduced, but not eliminated, by adjusting the air pressure. The maximum pressure levels seemed to be related to the shape of the buttocks, especially the amount of soft tissue, and exceeded the defined threshold for pressure ulcers (> 80 g/cm2).

Adolescent↗
PubMed2005

Effectiveness of an alternating pressure air mattress for the prevention of pressure ulcers.

BACKGROUND: studies of the effectiveness of alternating pressure air mattresses (APAMs) for the prevention of pressure ulcers are scarce and in conflict. OBJECTIVE: evaluating whether an APAM is more or equally effective as the standard prevention. DESIGN: randomised controlled trial. SETTING AND SUBJECTS: patients admitted to 19 surgical, internal, or geriatric wards in seven Belgian hospitals were included if they were in need of prevention of pressure ulcers. To define this need, two methods were used randomly: the Braden Scale or the presence of non-blanchable erythema (NBE). METHODS: 447 patients were randomised into either an experimental or a control group. In the experimental group, 222 patients were lying on an APAM (Alpha-X-Cell, Huntleigh Healthcare, UK). In the control group, 225 patients were lying on a visco-elastic foam mattress (Tempur, Tempur-World Inc., USA) in combination with turning every 4 hours. Both groups had identical sitting protocols. RESULTS: there was no significant difference in incidence of pressure ulcers (grade 2-4) between the experimental (15.6%) and control group (15.3%) (P = 1). There were significantly more heel pressure ulcers in the control group (P = 0.006). There was an interaction effect between the risk assessment method and preventive measures for the development of all pressure ulcers and sacral pressure ulcers. CONCLUSION: fewer patients developed heel pressure ulcers on an APAM. Patients identified as being in need of prevention based on the presence of NBE had a tendency to develop fewer pressure ulcers on an APAM. Patients identified as being in need of prevention, based on the Braden Scale, appeared to develop more sacral pressure ulcers on an APAM.

Aged↗
PubMed2003

Growth and beta-galactosidase activity in cultures of Kluyveromyces marxianus under increased air pressure.

AIMS: To investigate the effect of total air pressure raise on cell growth and intracellular beta-galactosidase activity in batch cultures of Kluyveromyces marxianus CBS 7894. METHODS AND RESULTS: A pressurized bioreactor was used for K. marxianus batch cultivation under increased air pressure from 1.2 to 6 bar. Under these conditions no inhibition of cell growth was observed. Moreover, the improvement of the oxygen transfer rate (OTR) from the gas to the culture medium by pressurization led to an enhancement of the cell growth rate obtained at atmospheric pressure without aeration. The specific beta-galactosidase productivity increased from 5.8 to 17.0 U gCD-1 h-1 using a 6-bar air pressure instead of air at atmospheric pressure. The antioxidant enzyme superoxide dismutase (SOD) was slightly induced by the air pressure raise, which indicates that the defensive mechanisms of the cells can cope with an air pressure up to 6 bar. CONCLUSIONS: These experiments showed that the increase of air pressure up to 6 bar is an alternative to other methods of preventing the oxygen limitation and can be applied in the beta-galactosidase production by K. marxianus. SIGNIFICANCE AND IMPACT OF THE STUDY: The results here reported proved that, in what biological aspects are concerned, it is possible to use the air pressure increase as an optimization parameter of beta-galactosidase production in high-density cell cultures of K. marxianus strains.

Air Pressure↗
PubMed1986

Osteoclast stimulation by positive middle-ear air pressure.

The mechanism of pathologic bone resorption associated with cholesteatoma is controversial. It is now evident that transmitted pressure is a significant factor in the activation of osteoclasts. Previous studies on the effect of pressure have been confounded by the possible foreign body effect of materials placed into the middle ear to induce the pressure. Positive air pressures were maintained in the middle ear of Mongolian gerbils via implanted Silastic catheters. Histologic evaluation of the ventral bulla wall was performed after pressure had been applied for two weeks. A significant increase in the number density, area density, and size of osteoclasts present in the pressurized bullae was noted at pressures of 4, 6, 10, and 20 mm Hg, but not at 2 mm Hg. We conclude that minute increases in pressure, in the absence of foreign objects, stimulate osteoclastic bone resorption in the middle ear of the gerbil.

Animals↗
PubMed1979

[Studies on the performance of the dental air turbine handpieces. (Part 1). Air pressure and bur length to be influenced over the rotational performance of the air bearing type handpieces (author's transl)].

Air turbine handpieces are used as the dental cutting instruments for the clinical use and many appliances. But, there are no studies on the performance of air turbine handpieces. So, this paper shows the rotational performance of air turbine handpieces which are influenced over the supplying air pressure and cutting bur length. Experimentally used air turbine handpieces is air bearing type and it's set up air pressure to be supplied is 3.5 kg/cm2. So, in this experiments, the range of air pressure is 1.8 approximately 3.5 kg/cm2, which is established five stages. And the bur length of the rotational parts is 5 approximately 9 mm with five steps. As the results, the rotational performance of air handpieces are influenced over these factors of the air pressure and the bur length. And air pressure to be supplied are influenced to be not only over the rotational speed but the load for the putting a stop to the revolutions.

Air Pressure↗
PubMedDate not supplied

Intraoral air pressure of alaryngeal speakers during a no-air insufflation maneuver.

Intraoral air pressure was recorded during the production of the consonant cognate pairs /p/-/b, /t/-/d, and /s/-/z/ by eight esophageal speakers. These consonants were combined with the vowel /a/ to form CV, VCV, and VC syllables and produced under two experimental conditions: after the insufflation of air and without air insufflation. The purpose was to determine if the voiced-voiceless pressure difference associated with the production of cognate pairs would occur in the absence of an insufflated air flow source. The results revealed that peak intraoral air pressure magnitudes were significantly greater following the insufflation of air than without it. Moreover, the voiceless consonants were generally produced with greater peak air pressures than the voiced consonants under both experimental conditions, although not all contrasts were significantly different. Finally, peak air pressure magnitudes were significantly more variable in the air insufflation condition. The finding that the esophageal speakers exhibited a pressure difference relative to voicing in the absence of an insufflated air flow source provides support to the concept that intraoral air pressure may be an important variable in regulating and controlling consonant production.

Aged↗
PubMed1996

Plant responses to reduced air pressure: advanced techniques and results.

Knowledge on air pressure impacts on plant processes and growth is essential for understanding responses to altitude and for comprehending the way of action of aerial gasses in general, and is of potential importance for life support systems in space. Our research on reduced air pressure was extended by help of a new set-up comprising two constantly ventilated chambers (283 L each), allowing pressure gradients of +/-100 kPa. They provide favourable general growth conditions while maintaining all those factors constant or at desired levels which modify the action of air pressure, e.g., water vapour pressure deficit and air mass flow over the plants. Besides plant growth parameters, transpiration and CO2 gas exchange are determined continuously. Results are presented on young tomato plants grown hydroponically, which had been treated with various combinations of air pressure (400-700-1000 hPa), CO2 concentration and wind intensity for seven days. At the lowest pressure transpiration was enhanced considerably, and the plants became sturdier. On the other hand growth was retarded to a certain extent, attributable to secondary air pressure effects. Therefore, even greater limitations of plant productivity are expected after more extended periods of low pressure treatment.

Air Movements↗
PubMed1999

Operating air pressure of disposable angles.

PURPOSE: This study was conducted to determine if air pressure of 20 pounds per square inch (psi) was sufficient to operate disposable prophylaxis angles smoothly and efficiently without stalling. METHOD: Five specimens of 15 types of disposable angles were evaluated by four dental hygienists to determine the minimum speed required for smooth operation. A fifth person operated the rheostat and increased the air pressure psi until signaled by the operators to stop once reaching a sufficient air pressure for operating the angle without stalling. Air pressure values were recorded for each test. Means and standard deviations were calculated for all raters for each angle. Data were analyzed using a two-way analysis of variance. Since there were no significant trends among raters, data for raters were combined for each angle and analyzed by a one-way analysis of variance. The Tukey-Kramer interval at a 0.05 significance level for comparisons among angles was determined. RESULTS: Study results showed that air pressure to achieve minimum speed required for smooth operation varied among the angles from 16.8 psi to 28.8 psi. The mean air pressure was 23.0 psi for angles with firm cups, 20.3 psi with soft cups, and 18.0 psi with regular cups. Some soft cup angles required air pressure greater than 20 psi while some firm cup angles required less than 20 psi. The regular flexibility of cup angles tested required less air pressure than 20 psi. CONCLUSION: The minimum air pressure psi required for smooth operation of disposable angles varied. Generally, air pressure greater than 20 psi was required to operate angles with firm cups, while less than 20 psi was required to operate angles with soft or regular cups.

Air Pressure↗
PubMed1992

Effect of ear-canal air pressure on evoked otoacoustic emissions.

The effect of ear-canal air pressure on click-evoked otoacoustic emissions was measured for pressures ranging from 200 to -200 daPa and stimulus levels ranging from 60-90 dB PeSPL. Positive and negative ear-canal pressures (relative to ambient pressure) reduced the emission amplitude by 3-6 dB. A spectral analysis of the emissions revealed that the effect of ear-canal air pressure is that of a high-pass filter with a cutoff frequency of 2600 Hz and a slope of 4 dB/oct. The spectral changes are the expected effect of an increase in stiffness of the middle ear and were independent of pressure polarity and click level. Ear-canal air pressure substantially reduced the reproducibility of the emission waveform, in many cases rendering the emission indistinguishable from background noise. The implication of these findings for hearing screening applications is that a high false alarm rate may occur in normal-hearing patients with intratympanic air pressures that are significantly different from ambient pressure.

Adult↗
PubMed2000

Assessment of alternating-pressure air mattresses using a time-based pressure threshold technique and continuous measurements of transcutaneous gases.

Alternating-pressure air mattresses (APAMs) are used increasingly for the prevention and treatment of pressure sores. Laboratory evaluation techniques have centred largely on interface pressure (IP) measurement, typically analysing discrete maximum and minimum levels, or average pressure. However, since pressure relief varies with time, a time-based analysis technique has been developed for performance assessment. IP was recorded continuously, and the duration of pressures below three thresholds (30, 20 and 10 mmHg) was calculated automatically using a computerized rig. Fifteen healthy volunteers were used to evaluate the pressure-relieving characteristics of four APAMs, including one overlay. Results indicated significant differences (P < 0.001) between products when durations below the 20 and 10 mmHg thresholds were analysed, showing that some devices were only capable of momentarily relieving pressure. Maximum contact pressures on the sacrum were significantly lower (P < 0.0001) on devices whose inflation pressure was adjusted according to subject's body mass. This technique could assist in the selection of alternating or dynamic surfaces of any description with further clinical validation.

Adult↗