Suction Of Fluid Research Articles

Thermal radiation and Hall effects on boundary layer flow past a non-isothermal stretching surface embedded in porous medium with non-uniform heat source/sink and fluid-particle suspension

Theoretical study on hydromagnetic heat transfer in dusty viscous fluid on continuously stretching non-isothermal surface, with linear variation of surface temperature or heat flux has been carried out. Effects of Hall current, Darcy porous medium, thermal radiation and non-uniform heat source/sink are taken into the account. The sheet is considered to be permeable to allow fluid suction or blowing, and stretching with a surface velocity varied according to a linear. Two cases of the temperature boundary conditions were considered at the surface namely, PST and PHF cases. The governing partial differential equations are transferred to a system of non-linear ordinary differential equations by employing suitable similarity transformations and then they are solved numerically. Effects of various pertinent parameters on flow and heat transfer for both phases is analyzed and discussed through graphs in detail. The values of skin friction and Nusselt number for different governing parameters are also tabulated. Comparison of the present results with known numerical results is presented and an excellent agreement is found.

Unsteady MHD boundary layer stagnation point flow with heat and mass transfer in nanofluid in the presence of mass fluid suction and thermal radiation

The unsteady boundary layer stagnation point flow of heat and mass transfer in a nanofluid with magnetic field and thermal radiation is theoretically investigated. The resulting governing equations are nondimensionalized and are transformed using a similarity transformation and then solved numerically by the shooting method. Comparison with the previously published work is presented and the results are found to be in good agreement. The effects of unsteadiness parameter A , solid volume fraction \( \varphi\), magnetic field M, radiation parameter R, Schmidit number Sc and suction parameter w on the fluid flow, heat and mass transfer characteristic are discussed. Dual similarity solutions for the velocity, temperature and concentration profiles are obtained for some negative values of the unsteadiness parameter. It is found that the critical values of A for which the dual solution exists depend on the values of solid volume fraction parameter in the presence of the Schmidit number. Also, the magnetic field parameter as well as the mass fluid suction widen the range of A for which the solution exists. The results also indicate that momentum, thermal and concentration boundary layer thickness for the first solution are thinner than that of the second solution.

A three-phase XFEM model for hydraulic fracturing with cohesive crack propagation

A three-phase hydro-mechanical model for hydraulic fracturing is proposed. Three phases include: porous solid, fracturing fluid and host fluid. Discontinuity is handled using extended finite element method (XFEM) while cohesive crack model is used as fracturing criterion. Flow through fracture is defined as one-dimensional laminar flow, and flow through porous medium (host reservoir) is defined as two-dimensional Darcy flow. Coupling between two fluids in each space, fracture and pore, is captured through capillary pressure–saturation relationship, while the identical fluids in fracture and pore are coupled through a so-called leak-off mass transfer term. Coupling between fluids and deformation is captured through compatibility of volumetric strain of fluids within fracture and pore, and volumetric strain of the matrix. Spatial and temporal discretisation is achieved using the standard Galerkin method and the finite difference technique, respectively. The model is verified against analytical solutions available from literature. The leaking of fracturing fluid into the medium and suction of porous fluid into the fracture around the tip, are investigated. Sensitivity analyses are carried out for cases with slow and fast injection rates. It is shown that the results by single-phase flow may underestimate the leak-off.

SUCTION INLET VORTEX INVESTIGATION AT LOW REYNOLDS NUMBERS

Under certain flow conditions, when an inlet is aspirated in close proximity to a solid boundary, a vortex will form between the surface and the inlet. The formation and ingestion of such vortices could potentially lead to inefficient fluid suction by pumps or catastrophic damages in high-speed jet engines. Previous studies established the basic relationship of such inlet vortices formation threshold and geometry and flow conditions, though they were typically considered at significantly high Reynolds numbers. It remains unclear if there is a lower limit to the Reynolds number at which this phenomenon ceases to exist. This study shows that this phenomenon exists even at low Reynolds number of Re = 160. In particular, the results are generally in agreement with the previously established relationships at much higher Reynolds numbers but certain correlations are not as significant. This suggests that formation of inlet vortices may be less sensitive to Reynolds numbers effects than previously thought.

Bio-Pick, Place, and Perfuse: A New Instrument for Three-Dimensional Tissue Engineering.

A grand challenge of tissue engineering is the fabrication of large constructs with a high density of living cells. By adapting the principles of pick-and-place machines used in the high-speed assembly of electronics, we have developed an innovative instrument, the Bio-Pick, Place, and Perfuse (Bio-P3), which picks up large complex multicellular building parts, transports them to a build area, and precisely places the parts at desired locations while perfusing the parts. These assembled parts subsequently fuse to form a larger contiguous tissue construct. Multicellular microtissues were formed by seeding cells into nonadhesive micro-molds, wherein cells self-assembled scaffold-free parts in the shape of spheroids, toroids, and honeycombs. After removal from the molds, the parts were gripped, transported (using an x, y, z controller), and released using the Bio-P3 with little to no effect on cell viability or part structure. As many as 16 toroids were stacked over a 170 μm diameter post where they fused over the course of 48 h to form a single tissue. Larger honeycomb parts were also gripped and stacked onto a build head that, like the gripper head, provided fluid suction to hold and perfuse the parts during assembly. Scaffold-free building parts help to address several of the engineering and biological challenges to large tissue biofabrication, and the Bio-P3 described in this article is a novel instrument for the controlled gripping, placing, stacking, and perfusing of living building parts for solid organ fabrication.

Radiative Heat and Mass Transfer of an MHD Free Convective Flow of Non-Newtonian Power-Law Fluids Along a Continuously Moving Stretching Sheet with Uniform Surface Heat Flux

An analysis is carried out to study the effects of MHD free convection heat and mass transfer of power-law non-Newtonian fluids along a stretching sheet with thermal radiation. This has been done under the simultaneous action of suction, thermal radiation and uniform transverse magnetic field. The stretching sheet is assumed to continuously moving with a power-law velocity and maintaining a uniform surface heat flux. The governing non–linear partial differential equations governing the flow field for heat and mass transfer problem are transformed into non–linear ordinary differential equations, using similarity transformation, and the resulting problem is solved numerically using Nachtsheim-Swigert shooting iteration technique along with sixth order Runge-Kutta integration scheme. The results from numerical computations have been presented in the from of dimensionless velocity, temperature and concentration profiles, shown graphically and discussed. A parametric study illustrating the influence of the flow field to radiation, buoyancy force, power-law fluid velocity index, Schmidt number, suction or injection parameter and uniform transverse magnetic field on the local skin friction coefficient, the local Nusselt number and the Sherwood number which are of physical and engineering interest are studied and the obtained results are shown graphically and the physical aspects of the problem are discussed. A comparison of the present study is also performed with the previously published work and found excellent agreement DOI: http://dx.doi.org/10.3329/dujs.v62i1.21958 Dhaka Univ. J. Sci. 62(1): 37-44, 2014 (January)

Vertical Mixed Jet Behavior of Orifice Nozzle

The objective of this study is to experimentally investigate the mixed jet and oxygen transfer behavior of a vertical orifice nozzle. The experimental apparatus consisted of an electric motor-pump, an orifice nozzle, a circulation water tank, an air compressor, a high speed camera unit and controlling or measuring accessories. The entrainment ratio was calculated using the measured primary fluid flow rate and suction air flow rate with primary flow pressure. The visualization image of vertically injected air and mixed jet issuing from the orifice nozzle was analyzed qualitatively. As the air compressor pressure increases, the penetration length of mixed jet decreases and the mass ratio and dissolved oxygen concentration increase.

Enhanced liquid–gas mixing due to pulsating injection

This paper considers the effects of intermittent injection of a liquid jet or spray on the initial break-up and mixing of one fluid with the surrounding ambient fluid. The aim of the analysis is to describe the physical process and indicate the mechanisms that control the mixing under different flow conditions (time-dependent injection and its frequency relative to the time scales of the flow) and fluid properties (density ratio), Schmidt number for a single phase case which is studied for comparison, or the Weber number for the two-phase cases. The computations use Large Eddy Simulation (LES) to account for turbulence, and either Volume Of Fluid (VOF) for the initial break-up or Lagrangian Particle Tracking (LPT) with droplet break-up model in the case of liquid droplets injected into the ambient gas. The results show that, depending on the physical properties of the liquid and ambient gas, the initial break-up and turbulent mixing can be enhanced substantially with intermittent injection. The numerical modeling is validated by recovering key results of experimental and analytical works. It can be observed that a main effect during the mixing is the suction of ambient fluid at the tail of the injected liquid, which depends on the fluid properties. Increased injection frequency shows to increase the mixing significantly during the initial transient phase.

Measurement of the sound intensity during suction of middle-ear fluid following myringotomy.

To determine noise intensity during middle-ear aspiration in order to evaluate whether levels can be potentially harmful. In this prospective, observational study, middle-ear effusion was aspirated following myringotomy using a suction instrument with a probe tube microphone. Sound pressure levels and duration were measured, and frequency domain analysis was performed. Forty-four ears were analysed, consisting of 20 with mucoid effusion, 11 with serous effusion and 13 with no effusion. Maximum peak sound intensity ranged from 84 to 157dB. Half of the ears (50 per cent) were exposed to greater than 140dB; of these, 82 per cent were exposed for longer than 0.2ms (range, 0.05-14ms). There was no significant difference in sound pressure level between ears with mucoid and serous effusion; however, ears with mucoid effusion required longer suction times (p<0.0030). In addition, peak intensity was greater for ears with mucoid effusion versus those with serous or no effusion (p<0.0001). Middle-ear aspiration during myringotomy caused noise levels within a potentially harmful range.

Fluid–particle interaction and generation of coherent structures over permeable beds: an experimental analysis

We study the dynamics of the oscillatory bottom boundary layer (BBL) that develops at a porous bed under the action of propagating water waves (also known as “ventilated BBL”). In particular, experimental tests of a ventilated BBL generated over a permeable bed made of regular plastic spheres are analysed. With the purpose of characterizing typical dynamics of nearshore waves evolving over dissipative seabeds, we focus on one specific forcing condition, characterized by large nonlinearities and vorticity generation, and expect that such dynamics be qualitatively similar also for other wave regimes. Particle tracking enables an accurate definition of the hydrodynamics generated over the porous medium with specific focus on Eulerian velocity and vorticity fields and on Lagrangian particle trajectories. Nearbed velocity components are strongly influenced by the bed configuration (sphere caps) and are characterized by small-scale oscillations due to the presence of coherent structures over the interstices. Counter-rotating vortex sheets are generated and evolve during the entire wave period; their thickness grows rapidly when flow injection from the bed occurs, while it remains constant under the influence of in-bed flow suction. The evolution of near-bed particles is influenced by strain or vortex-dominated regions. When the intensity of the vortices just outside the BBL is large (generally after flow inversion), the momentum associated to the rotation of the lower layer of vortices in the BBL is comparable with that of the passive tracers, hence the particles are captured and their original trajectories are modified, jumping to a different layer. On the contrary when strain regions are dominant, particles are restricted in the same vorticity layer until sweep or ejection turbulent processes are observed and anomalous particle transport occurs from lower to higher vortex layers and vice versa. The latter occurs during the entire wave cycle, becoming the dominant process, while the former occurs before flow inversion and close to the porous bed. This result reveals that nearbed small-scale phenomena are weakly influenced by the wave mean flow. A detailed description of fluid suction and injection is proposed in terms of the mean flow dynamics (at wave scale), while the actual inflow/outflow of particles at the bed is seen to depend on local, small-scale flow properties. Suction and injection are generated during positive and negative water surface elevations and either squeeze or expand the flow downward/upward. The suction/injection perturbations contribute to the triggering of sweep and ejection events. Suction is mainly concentrated very close to the bed, injection is rapidly transported above the BBL, but the highest turbulence occurs in correspondence of suction events.

A Note on the Temperature Distribution in a Porous Annulus

Unsteady temperature distribution for flow of an incompressible viscous fluid in a porous annulus has been investigated under the assumption that the rate of injection of the fluid at the inner cylinder is equal to the rate of suction of the fluid at the outer one. Viscous dissipation has been neglected while rate of heat generation in the fluid has been accounted for. An expression for the temperature distribution has been obtained using Laplace transform technique and taking the temperatures of the boundaries to be functions of time.

Air Impingement Cooling by Synthetic Jet

Modern consumer electronic trends point to a demand for thinner and more portable electronic devices. Conventional cooling systems of these portable electronic devices are challenging to miniaturize in thin profile applications that are typically on the order of several millimeters in thickness. In order to overcome some of these challenges, a synthetic jet, which is also considered as micro fluidic device, is developed. This device which operates based on Piezo electricity is called Dual Cooling Jet (DCJ). DCJ disturbs the boundary layer over a hot component and hence increases heat transfer compare to conventional blower. DCJ is typically defined as a device using a partially enclosed cavity with oscillating walls/diaphragms to create alternating suction and ejection of fluid across an interface or orifice. In this work, the results of cooling performance investigation of DCJ are shown and compared with natural convection cooling. Also, several experiments have been done to study the cooling effect of DCJ at different configuration with respect to heat source and the results are compared. At the end, the effects of heat source size is investigated which are helpful to understand how effective DCJ is when used for cooling several size chips. In addition, the results of this work show that DCJ can be combined with low profile heat sink as a promising next generation ultra thin thermal solution module.

Controlled reattachment in separated flows: a variational approach to recirculation length reduction

AbstractA variational technique is used to derive analytical expressions for the sensitivity of recirculation length to steady forcing in separated flows. Linear sensitivity analysis is applied to the two-dimensional steady flow past a circular cylinder for Reynolds numbers $40 \leq Re \leq 120$, in both the subcritical and supercritical regimes. Regions that are the most sensitive to volume forcing and wall blowing/suction are identified. Control configurations that reduce the recirculation length are designed based on the sensitivity information, in particular small cylinders used as control devices in the wake of the main cylinder, and fluid suction at the cylinder wall. Validation against full nonlinear Navier–Stokes calculations shows excellent agreement for small-amplitude control. The linear stability properties of the controlled flow are systematically investigated. At moderate Reynolds numbers, we observe that regions where control reduces the recirculation length correspond to regions where it has a stabilizing effect on the most unstable global mode associated with vortex shedding, while this property no longer holds at larger Reynolds numbers.

EFFECT OF LASER RADIATION ON ADENOSINE DEAMINASE CONCENTRATION IN PLEURAL FLUID

The aim of this study was to investigate effects of low-intense laser irradiation (intravenous, intrapleural and combined) on adenosine deaminase (ADA) concentration in the pleural fluid of patients with pleural effusion of various etiology. Materials and methods. We examined patients aged 30 to 80 years with pleural effusion ( n = 45; 25 males (55.6 %), 20 females (44.4 %); the mean age, 67.6 ± 13.9 years). The cause of the pleural effusion was pneumonia ( n = 14), trauma ( n = 2) or chronic heart failure ( n = 29). All patients were randomly divided in a control group ( n = 17) or laser treatment group ( n = 28). The control group patients received standard treatment according to etiology of the effusion. The laser group patients were treated with laser and medications. Laser was applied using "Matrix-VLOK" device (Matrix, Russia) with the wave length of 0.365 μm and output of 1.0 – 1.5 mWt. Laser therapy was administered in continuous irradiation mode; course duration was 3 to 7 sessions in dependence on a rate of the fluid accumulation in the pleural cavity, in every other day. Intravenous laser irradiation was performed for 10 min after cubital vena puncture with a needle with KIVL-01 light-guide fiber. Intrapleural laser irradiation was performed for 10 min after pleurocentesis with the needle and light-guide fiber following pleural fluid suction and instillation of a wide-spectrum antibiotic solution. The pleural fluid was centrifuged during 10 min in 1,500 g and then was freezed in –20 °С until the examination. Studied parameters were measured before and after the treatment. Results. The laser group patients demonstrated a significant decrease in ADA concentration compared to baseline (25.30 ± 1.56 and 18.70±1.94МЕ × l–1 before and after treatment, respectively). The laser therapy in addition to the standard treatment was also related to clinical improvement. In controls the standard medication therapy did not lead to any change in ADA concentration (25.70 ± 1.63 and 22.80 ± 1.98 МЕ × l–1 before and after treatment, respectively). Conclusion. The results showed that in patients with pleural effusion the laser therapy in addition to the standard treatment was related to decrease in ADA concentration, slower fluid accumulation in the pleural cavity and shorter treatment duration. Time to the second pleural puncture was longer, the need in drug therapy was diminished and the treatment efficacy was higher in the laser treatment group. These effects led to improving quality of life and was thought to make the laser therapy rational in patients with pleural effusion of various etiology.

Early beak development in Argonauta Nodosa and Octopus Vulgaris (Cephalopoda: Incirrata) paralarvae suggests adaptation to different feeding mechanisms

Morphological and morphometric development of the beak of Argonauta nodosa (oceanic species) and Octopus vulgaris (neritic species) paralarvae were analyzed in order to verify whether or not they are determined by distinct life strategies and habitats. Measurements were taken from the upper jaw (UJ) and lower jaw (LJ), compared by the t test to identify-specific differences, and correlated with mantle length (ML) by multiple linear regression to determine overall and relative influences on growth. The jaws of both species were fragile, lightly colored, presented dentition and a slit (division) in the LJ rostrum, and showed considerable variation in general aspect. The hood and lateral walls (UJ) and crest and wings (LJ) showed the highest correlation with paralarval size (ML), and were more developed in A. nodosa than in O. vulgaris of similar size. The rostrum of O. vulgaris seems to be less functional than that of A. nodosa. The presence of beak characteristics from ancestral cephalopod species in the jaws of early paralarvae, namely teeth and a slit in the LJ rostrum, and also the inability of small-sized A. nodosa paralarvae to close the jaws and bite off a piece of prey, seem to be related to the performance of external pre-digestion and suction of body fluids of prey, a specialized feeding mode.

Pore-water extraction from the unsaturated and saturated zones

A simple, inexpensive method for extracting pore water from unsaturated soils, which uses a combination of immiscible fluid displacement, suction, and mechanical compression, is described. This method uses a squeezing chamber to contain the unsaturated sediments in aluminum core tubing to prevent exposure of the sediments and pore water to atmospheric O2 and subsequent oxidation reactions. Geochemical artifacts resulting from high-compression squeezing are prevented by maintaining the pressure applied during the squeezing at a minimum. Comparison of squeezed profiles with field measured profiles of pH, Eh (oxidation–reduction potential), alkalinity, and metal speciation indicates good agreement between these parameters using this method. Depending on the water content of the sediments, a range of water volumes (several millilitres to excess of 100 mL) can be extracted from a single core section 7.6 cm in diameter by 20 cm long. Pore water was produced immediately from sediments at near-saturated conditions, whereas several hours were required to obtain pore water from sediment with low moisture contents. Pore water was extracted from unsaturated sediments with as little as 6% volumetric moisture content. The squeezing technique provided water samples from both unsaturated and saturated sediments ranging from silt- to sand-sized particles. The method was applied successfully to collect pore waters from unsaturated sediments in neutral and acidic mine tailings; processed sands from oil sand operations, septic beds, agriculturally impacted sediments; and saturated soils from peat bogs, from wetlands, and at groundwater–surface interfaces.

Intrathecal interferon-induced seizure

A recent multicenter study (60 patients) shows the efficacy of intralesional therapy with interferon (IFN)-alpha in the treatment of predominantly cystic craniopharyngiomas; tumour size decreased more than 50 % in 78.3 % of patients. The mean follow-up durationwas 44months (range 4–84months). After the treatment, 13 % of patients developed new endocrinological deficits, while other patients developed transient fever, headache or palpebral edema; seizures have not been described [2]. A 48-year-old woman with a cystic craniopharyngioma underwent stereotactic positioning of an intracystic catheter with Rickham reservoir in September 2012. Cyst drainage was performed; the patient suffered from a sudden, sharp, pain at the level of the temple omolateral to the reservoir at the end of the suction of the cyst fluid. No other side-effects occurred. After few days the patient started a protocol of intracystic interferon-alpha injection. Through the Rickham, doses of 3,000 IU of IFN-alpha were administered three times a week, for 4 weeks, following the protocol of Cavalheiro et al. [2]. Beginning from the second week of treatment, the patient did not tolerate the therapy, suffering from nausea, headache, and rare episodes of vomiting; symptoms were partially controlled through medication. A CT scan without contrast injection performed during the treatment excluded complications and showed the shrinkage of the cystic component. After the last administration of interferon, she suffered from a generalized tonico-clonic seizure (GTCS). After the discontinuation of interferon, the patient recovered well and did not present further seizure episode. The last CT scan control (Fig. 1) the complete disappearance of the cyst. According to the study of Cavalheiro, leakage from a craniopharyngioma’s cyst is not considered a contraindication for intralesional IFN-alpha injection, because its lack of neurotoxicity. Cyst shrinkage and the possibility of communication between the cyst and liquoral spaces were considered in our case. The treatment was carried on as suggested by other literature reports [2] with the aim of continuing the antiblastic effects on cyst walls. A previous report [3] describes a patient with a brain– blood barrier (BBB) rupture, due to a previous cranial surgery for a left parietal meningioma. Two weeks after the beginning of subcutaneous IFN-alpha therapy for chronic hepatitis, he suffered from a GTCS, which did not recur after IFN-alpha discontinuation. On this clinical observation a laboratory study on rats was performed; this study concluded that cortical exposure to IFN can generate an epileptic cortex. Our brief report shows that IFN-alpha intrathecal therapy can be associated to a GTCS; other literature reports show that subcutaneous IFN-alpha therapy [1, 4] can be associated with seizure. For this reason, performing a CT scan with iodate contrast into the Rickham, before IFN injection, has to be considered, in order to perform a safer intralesional IFN therapy. Of course, further clinical studies are required in order to confirm our observation. M. Rizzi (*) :G. Messina :M. Castiglione :V. Nazzi : A. Franzini Department of Neurosurgery, IRCCS Istituto Neurologico Carlo Besta, Milan, Italy e-mail: michele.rizzi@live.it

Mechanisms and critical properties in drying shrinkage of soils: experimental and numerical parametric studies

Mechanisms of free-shrinkage strains of desiccating deformable initially saturated soils are studied. The role of the surface evaporation rate, surface tension and viscosity of pore fluid, and soil compressibility and permeability is investigated in experimental and numerical parametric studies. Two different geomaterials with three different pore fluids are tested and numerically simulated using a macroscale Biot theory model and a mesoscale vessel model. Evolution of shrinkage strain and fluid content is reported and evaluated. The total amount of shrinkage and shrinkage limit are found to correlate with both solid fraction compressibility and surface tension of the fluid fraction. Most of the strain occurs in the saturated stage of drying concomitant with a build-up of fluid suction. The macroscopic Biot model yields good results in the saturated stage of drying. However, the air-entry criteria are all formulated at meso- or microscale. Hence, a mesoscale deformable pore vessel model is adopted, with pore fluid suction limited by a fluid tensile stress threshold identified with fluid cavitation. Beyond cavitation, air entry occurs. Subsequently, partially fluid-filled pore vessels are considered with fluid evaporation across a migrating fluid–gas interface within the vessel. A mesoscale model parametric study confirms that the total drying shrinkage strain and the shrinkage limit depend on the solids' compressibility, as well as on the fluid surface tension.

Experimental investigation on ejecting low-temperature cooling superconducting magnets

With the development of the high-temperature superconducting (HTS) materials and refrigeration technologies, using ejecting refrigeration to cool the superconducting materials becomes the direction of HTS applications. In this paper, an experimental study has been carried out on the basis of the theory of analyzing the ejecting low-temperature cooling superconducting magnet. The relationship between area ratios and refrigeration performance at different system pressures was derived. In addition, the working fluid flow and suction chamber pressure of the ejector with different area ratios at various inlet pressures have been examined to obtain the performance of ejectors under different working conditions. The result shows that the temperature of liquid nitrogen can be reduced to 70K by controlling the inlet water pressure when the pressurized water at 20°C is used to eject the saturated liquid nitrogen, which can provide the stable operational conditions for the HTS magnets cooling.

Cough Reflex Under Intravenous Sedation During Dental Implant Surgery Is More Frequent During Procedures in the Maxillary Anterior Region

The present study was performed to evaluate the incidence of cough episodes and the association between cough episodes and patient-related and site-specific parameters during implant surgery when performed under intravenous sedation. One hundred forty-seven patients scheduled for dental implant surgeries under intravenous sedation were enrolled in this study. Heart rate, blood pressure, percutaneous oxygen saturation, and bispectral index were monitored. Sedation was induced intravenously by a bolus administration of midazolam and maintained by a continuous administration of propofol. Sedation level was adjusted to achieve scores of 3 to 4 on the Ramsay Sedation Scale. Surgical procedures were divided into 11 stages. Implant sites were labeled as right maxillary molar, maxillary anterior, left maxillary molar, right mandibular molar, mandibular anterior, and left mandibular molar sites. When coughing occurred, heart rate, blood pressure, percutaneous oxygen saturation, bispectral index, procedure being performed, and surgical site being stimulated were recorded. One hundred seventy-two cough episodes were observed in 97 patients (66%). Cough episodes occurred during all stages of surgery but were substantially more frequent during preparation of the implant site. The incidence of cough episodes was significantly higher at the maxillary anterior site and lowest at the right mandibular molar areas. These findings suggest that difficulties in swallowing and in the suction of intraoral fluids have variable effects at different surgical sites. Careful suction of intraoral water and an appropriate sedation level are required, especially in procedures in the maxillary anterior region.