Pulsed Delivery Research Articles

Single-mode solarization-free hollow-core fiber for ultraviolet pulse delivery.

In this paper, we report anti-resonant silica hollow-core fibers (AR-HCFs) for solarization-free ultraviolet (UV) pulse transmission. The new fibers reported have lower attenuation than any previous HCFs for this spectral range. We report a single fiber that guides over a part of the UV-C and the whole of the UV-A spectral regions in adjacent transmission bands. A second AR-HCF is used for delivery of 17 nanosecond laser pulses at 266 nm at 30 kHz repetition rate. The fiber maintained a constant transmission, free of silica fluorescence and solarization-induced fiber degradation while delivering 0.46 μJ pulses for a period of over one hour. By direct comparison, we demonstrate that the single-mode AR-HCF significantly outperforms commercially-available high-OH and solarization-resistant silica multimode fibers for pulsed light delivery in this spectral range.

Pulmonary Delivery of Therapeutic and Diagnostic Gases.

The 21st Congress for the International Society for Aerosols in Medicine included, for the first time, a session on Pulmonary Delivery of Therapeutic and Diagnostic Gases. The rationale for such a session within ISAM is that the pulmonary delivery of gaseous drugs in many cases targets the same therapeutic areas as aerosol drug delivery, and is in many scientific and technical aspects similar to aerosol drug delivery. This article serves as a report on the recent ISAM congress session providing a synopsis of each of the presentations. The topics covered are the conception, testing, and development of the use of nitric oxide to treat pulmonary hypertension; the use of realistic adult nasal replicas to evaluate the performance of pulsed oxygen delivery devices; an overview of several diagnostic gas modalities; and the use of inhaled oxygen as a proton magnetic resonance imaging (MRI) contrast agent for imaging temporal changes in the distribution of specific ventilation during recovery from bronchoconstriction. Themes common to these diverse applications of inhaled gases in medicine are discussed, along with future perspectives on development of therapeutic and diagnostic gases.

Formulation of Modified Release Pellets of Montelukast Sodium

The present study was carried out with an aim of preparing modified release pellets of the antiasthma drug montelukast sodium. The patients suffering from chronic asthma many a times suffer from exacerbations during the early morning hours i.e. around 4am to 6 am. Thus the need to take an immediate release medication arises during early morning hours which is not quiet feasible for the patients. The delivery of the drug at this time can be made possible by the use of modified release formulation of montelukast sodium which when taken at the bed time would release the drug as a pulsed delivery without the need of the patient to wake up. The montelukast sodium pellets prepared by extrusion-spheronization were coated with release retarding polymer ethyl cellulose using the Wurster method. The ethyl cellulose coating helped in lag time increase due to prolonged water uptake time. The increase in the coating level increased the lag time sufficiently that might release the drug during the early morning hours. Thus a modified release pellets dosage form to prevent the early morning asthma attacks and exacerbations was developed successfully.

Residents' journal review

Residents' journal review

The effect of low-level laser therapy on orthodontically induced root resorption: a pilot double blind randomized controlled trial.

The effect of low-level laser therapy (LLLT) on accelerating orthodontic tooth movement has been extensively studied; however, there is limited knowledge on the use of LLLT on orthodontic root resorption. To investigate the effect of LLLT on orthodontically induced inflammatory root resorption (OIIRR) and to compare the difference between pulsed and continuous LLLT on OIIRR. Double-blind, single-centre 3-arm parallel split-mouth randomized controlled trial. Twenty adolescent patients who required bilateral maxillary first premolar (MFP) orthodontic extractions were recruited from the Sydney Dental Hospital between October 2014 and December 2014. All MFPs were tipped buccally for 28 days to induce OIIRR. The experimental premolars (n = 20) received LLLT and the control premolars (n = 20) received placebo-laser on days 0, 1, 2, 3, 7, 14, and 21. Ten experimental premolars received LLLT via continuous delivery and 10 received pulsed delivery. AlGaAs diode laser of 808 nm wavelength, 0.18 W power, 1.6 J per point, and duration of 9s for continuous mode and 4.5 s for pulsed mode. The difference in root resorption crater volume between LLLT and placebo-laser and continuous or pulsed laser delivery after 28 days. Randomization was computer-generated, with allocation concealment by opaque sequentially numbered sealed envelopes. The participants and operator were blinded. Eighty-eight patients were screened and 20 patients were randomized. Forty premolars were analysed. LLLT resulted in 23 per cent less root resorption compared to the placebo (P = 0.026). Pulsed laser delivery resulted in 5 per cent less root resorption than continuous; however, this was not statistically significant (P = 0.823). No harm was observed. Teeth treated with LLLT had less total root resorption than placebo-laser. Furthermore, there was minimal difference between pulsed or continuous delivery of LLLT. Clinical Trials Registry (ACTRN12616000829415). The protocol was not published before trial commencement.

Pulsed inhaled nitric oxide improves arterial oxygenation in colic horses undergoing abdominal surgery

ObjectiveTo evaluate the effect of pulsed inhaled nitric oxide (INO) on arterial oxygenation in horses during abdominal surgery. Study designProspective, randomized, clinical trial. AnimalsThirty horses that underwent abdominal surgery at the University Animal Hospital in Uppsala, Sweden. MethodsAnaesthesia was induced according to a standard protocol – romifidine, butorphanol, diazepam and ketamine and maintained with isoflurane in oxygen. Fifteen horses were administered pulsed INO and 15 served as controls. After baseline data collection, pulsed INO delivery commenced. Arterial and venous blood were collected and analysed. Cardiorespiratory parameters were measured, and oxygen content and F-shunt were calculated. ResultsArterial oxygen tension (PaO2) and arterial oxygen saturation (SaO2) increased from 10.9±5.7 kPa (82±43 mmHg) and 93±6% to 17.3±6.9 kPa (134±52 mmHg) (p<0.0001) and 98±2% (p<0.0001), respectively, in horses administered pulsed INO. In the control group, PaO2 and SaO2 decreased from 13.9±9.1 kPa (104±68 mmHg) and 93±7% to 12.1±8.6 kPa (91±65 mmHg) (p=0.0413) and 91±8% (p=0.0256), respectively. At the end of anaesthesia, the oxygen content was significantly higher in horses administered pulsed INO compared to controls (p=0.0126). The calculated F-shunt decreased from 39±10% to 27±6% (p<0.0001) in horses administered pulsed INO, and remained unchanged in controls, 40±12% to 44±12%. Blood lactate concentration decreased (–17±21%) in horses administered pulsed INO (p=0.0119), whereas no difference was measured in controls (2±31%). Conclusions and clinical relevanceThe present study showed that it is possible to effectively reduce the F-shunt and improve arterial oxygenation in horses during abdominal surgery by continuous delivery of pulsed INO.

DC voltage fields generated by RF plasmas and their influence on film growth morphology through static attraction to metal wetting layers: Beyond ion bombardment effects

It is shown that attractive electrostatic interactions between regions of positive charge in RF plasmas and the negative charge of metal wetting layers, present during compound semiconductor film growth, can have a greater influence than substrate temperature on film morphology. Using GaN and InN film growth as examples, the DC field component of a remote RF plasma is demonstrated to electrostatically affect metal wetting layers to the point of actually determining the mode of film growth. Examples of enhanced self-seeded nanopillar growth are provided in the case where the substrate is directly exposed to the DC field generated by the plasma. In another case, we show that electrostatic shielding of the DC field from the substrate can result in the growth of Ga-face GaN layers from gallium metal wetting layers at 490 °C with root-mean-square roughness values as low as 0.6 nm. This study has been carried out using a migration enhanced deposition technique with pulsed delivery of the metal precursor allowing the identification of metal wetting layers versus metal droplets as a function of the quantity of metal source delivered per cycle. It is also shown that electrostatic interactions with the plasma can affect metal rich growth limits, causing metal droplet formation for lower metal flux than would otherwise occur. Accordingly, film growth rates can be increased when shielding the substrate from the positive charge region of the plasma. For the example shown here, growth rates were more than doubled using a shielding grid.

Influence of growth temperature on carrier localization in InGaN/GaN MQWs with strongly redshifted emission band

To shift the emission band to long wavelength side, InGaN/GaN multiple quantum wells were grown by metalorganic chemical vapor deposition (MOCVD) using pulsed delivery of the metalorganic precursors at fixed parameters of the pulses but variable growth temperatures and by introducing short-period superlattices (SPSL) as buffer layers. By decreasing the growth temperatures for both SPSL and quantum wells down to 800°C, a considerable shift of the photoluminescence (PL) band peak down to ~2eV is achieved at reasonably acceptable decrease in PL intensity at low carrier density. However, increase in the carrier density resulted in considerable blue shift of the band, and the efficiency droop onset occurred at rather low carrier densities. The comparison of the data on PL and differential optical transmittance, which were supported by structural analysis, revealed that the large red shift in the PL band position is predominantly caused by an increasing tail of localized states. Meanwhile, the efficiency droop effect in the samples under study is caused predominantly by the enhancement of nonradiative carrier recombination.

Onset of leptin resistance shows temporal differences related to dose or pulsed treatment

Leptin administration results in leptin resistance presenting a significant barrier to therapeutic use of leptin. Consequently, we examined two hypotheses. The first examined the relationship between leptin dose and development of physiological and biochemical signs of leptin resistance. We hypothesized lower doses of leptin would produce proportional reductions in body weight without the adverse leptin-induced leptin resistance. The second compared pulsed central leptin infusion to continuous leptin infusion. We hypothesized that pulsed infusion at specific times of the day would evoke favorable body weight reductions while tempering the development of leptin-induced leptin resistance. The first experiment examined leptin responsiveness, including food intake, body weight and hypothalamic STAT3 phosphorylation to increasing doses of viral gene delivery of leptin. Varying the dose proved inconsequential with respect to long-term therapy and demonstrated proportional development of leptin resistance. The second experiment examined leptin responsiveness to pulsed central leptin infusion, comparing pulsed versus constant infusion of 3μg/day leptin or a 2h morning versus a 2h evening pulsed leptin infusion. Pulsed delivery of the supramaximal dose of 3μg/day was not different than constant delivery. Morning pulsed infusion of the submaximal dose of 0.25μg reduces food intake only over subsequent immediate meal period and was associated with body weight reductions, but results in cellular leptin resistance. Evening pulsed infusion did not decrease food intake but reduces body weight and maintains full leptin signaling. The positive benefit for pulsed delivery remains speculative, yet potentially may provide an alternative mode of leptin therapy.

The I/O transform of a chemical sensor

A number of sensing technologies, using a variety of transduction principles, have been proposed for non-invasive chemical sensing. A fundamental problem common to all these sensing technologies is determining what features of the transducer's signal constitute a chemical fingerprint that allows for precise analyte recognition. Of particular importance is the need to extract features that are robust with respect to the sensor's age or stimulus intensity. Here, using pulsed stimulus delivery, we show that a sensor's operation can be modeled as a linear input-output (I/O) transform. The I/O transform is unique for each analyte and can be used to precisely predict a temperature-programmed chemiresistor's response to the analyte given the recent stimulus history (i.e. state of an analyte delivery valve being open or closed). We show that the analyte specific I/O transforms are to a certain degree stimulus intensity invariant and can remain consistent even when the sensor has undergone considerable aging. Significantly, the I/O transforms for a given analyte are highly conserved across sensors of equal manufacture, thereby allowing training data obtained from one sensor to be used for recognition of the same set of chemical species with another sensor. Hence, this proposed approach facilitates decoupling of the signal processing algorithms from the chemical transducer, a key advance necessary for achieving long-term, non-invasive chemical sensing.

Pulsed iceberg delivery driven by Sturtian ice sheet dynamics: An example from Death Valley, California

AbstractThe Kingston Peak Formation is a Cryogenian sedimentary succession that crops out in the Death Valley area, California, USA. It is widely accepted to record pre‐glacial conditions (KP1), followed by two glaciations of pan‐global extent, the older Sturtian (KP2 to KP3) and younger Marinoan glaciation (KP4). In the type area (the Kingston Range), detailed facies analysis of the Sturtian succession reveals that a basal diamictite unit and an upper boulder conglomerate were deposited by proglacial subaqueous sediment gravity flows. An olistostrome unit punctuating the succession is interpreted to result from tectonically induced downslope mobilization during isostatic rebound, triggered by significant ice‐meltback. Focussing on strata onlapping the olistostrome, this article provides insight into the processes of glacial re‐advance following an intra‐Sturtian glacial minimum. The first 50 m of strata above the olistostrome are thinly bedded turbidites that are devoid of lonestones. A trend towards thicker graded beds upsection, in concert with the gradual appearance and then abundance of lonestones, testifies to the influence of ice rafting and to the resumption of a direct ice sheet influence upon sedimentation. Stratigraphic organization into thickening and coarsening upward bedsets over a multi‐metre scale reveals a subaqueous gravity flow‐dominated succession composed of a spectrum of high to low density turbidites, with thick graded boulder‐conglomerates at intervals. The finer‐grained facies assemblage is heterolithic: current ripple cross‐laminated sandstones intercalated with shales that bear delicate granule to pebble‐sized dropstones in abundance. Intervals of dropstone‐bearing and dropstone‐free strata are attributable to dynamic oscillation of the ice margin in the hinterland. Integrating palaeocurrent data with observations from neighbouring outcrop belts allows a detailed palaeogeographic map of the eastern Death Valley area to be compiled for the first time.

A pulsed mode electrolytic drug delivery device

This paper reports the design of a proof-of-concept drug delivery device that is actuated using the bubbles formed during electrolysis. The device uses a platinum (Pt) coated nickel (Ni) metal foam and a solid drug in reservoir (SDR) approach to improve the device’s performance. This electrochemically-driven pump has many features that are unlike conventional drug delivery devices: it is capable of pumping periodically and being refilled automatically; it features drug release control; and it enables targeted delivery. Pt-coated metal foam is used as a catalytic reforming element, which reduces the period of each delivery cycle. Two methods were used for fabricating the Pt-coated metal: sputtering and electroplating. Of these two methods, the sputtered Pt-coated metal foam has a higher pumping rate; it also has a comparable recombination rate when compared to the electroplated Pt-coated metal foam. The only drawback of this catalytic reformer is that it consumes nickel scaffold. Considering long-term applications, the electroplated Pt metal foam was selected for drug delivery, where a controlled drug release rate of 2.2 μg ± 0.3 μg per actuation pulse was achieved using 4 mW of power.

Efficacy of a portable oxygen concentrator with pulsed delivery for treatment of hypoxemia during equine field anesthesia

ObjectiveHypoxemia is common during equine field anesthesia. Our hypothesis was that oxygen therapy from a portable oxygen concentrator would increase PaO2 during field anesthesia compared with the breathing of ambient air. Study designProspective clinical study. AnimalsFifteen yearling (250 – 400 kg) horses during field castration. MethodsHorses were maintained in dorsal recumbency during anesthesia with an intravenous infusion of 2000 mg ketamine and 500 mg xylazine in 1 L of 5% guaifenesin. Arterial samples for blood gas analysis were collected immediately post-induction (PI), and at 15 and 30 minutes PI. The control group (n = 6) breathed ambient air. The treatment group (n = 9) were administered pulsed-flow oxygen (192 mL per bolus) by nasal insufflation during inspiration for 15 minutes PI, then breathed ambient air. The study was performed at 1300 m above sea level. One-way and two-way repeated-measures anova with post-hoc Bonferroni tests were used for within and between-group comparisons, respectively. Significance was set at p ≤ 0.05. ResultsMean ± SD PaO2 in controls at 0, 15 and 30 minutes PI were 46 ± 7 mmHg (6.1 ± 0.9 kPa), 42 ± 9 mmHg (5.6 ± 1.1 kPa), and 48 ± 7 mmHg (6.4 ± 0.1 kPa), respectively (p = 0.4). In treatment animals, oxygen administration significantly increased PaO2 at 15 minutes PI to 60 ± 13 mmHg (8.0 ± 1.7 kPa), compared with baseline values of 46 ± 8 mmHg (6.1 ± 1 kPa) (p = 0.007), and 30 minute PI values of 48 ± 7 mmHg (6.5 ± 0.9 kPa) (p = 0.003). ConclusionsThese data show that a pulsed-flow delivery of oxygen can increase PaO2 in dorsally recumbent horses during field anesthesia with ketamine-xylazine-guaifenesin. Clinical relevanceThe portable oxygen concentrator may help combat hypoxemia during field anesthesia in horses.

The Effects of Pulsed Radiation Therapy on Tumor Oxygenation in 2 Murine Models of Head and Neck Squamous Cell Carcinoma

To evaluate the efficacy of low-dose pulsed radiation therapy (PRT) in 2 head and neck squamous cell carcinoma (HNSCC) xenografts and to investigate the mechanism of action of PRT compared with standard radiation therapy (SRT). Subcutaneous radiosensitive UT-SCC-14 and radioresistant UT-SCC-15 xenografts were established in athymic NIH III HO female mice. Tumors were irradiated with 2 Gy/day by continuous standard delivery (SRT: 2 Gy) or discontinuous low-dose pulsed delivery (PRT: 0.2 Gy × 10 with 3-min pulse interval) to total doses of 20 Gy (UT14) or 40 Gy (UT15) using a clinical 5-day on/2-day off schedule. Treatment response was assessed by changes in tumor volume, (18)F-fluorodeoxyglucose (FDG) (tumor metabolism), and (18)F-fluoromisonidazole (FMISO) (hypoxia) positron emission tomography (PET) imaging before, at midpoint, and after treatment. Tumor hypoxia using pimonidazole staining and vascular density (CD34 staining) were assessed by quantitative histopathology. UT15 and UT14 tumors responded similarly in terms of growth delay to either SRT or PRT. When compared with UT14 tumors, UT15 tumors demonstrated significantly lower uptake of FDG at all time points after irradiation. UT14 tumors demonstrated higher levels of tumor hypoxia after SRT when compared with PRT as measured by (18)F-FMISO PET. By contrast, no differences were seen in (18)F-FMISO PET imaging between SRT and PRT for UT15 tumors. Histologic analysis of pimonidazole staining mimicked the (18)F-FMISO PET imaging data, showing an increase in hypoxia in SRT-treated UT14 tumors but not PRT-treated tumors. Differences in (18)F-FMISO uptake for UT14 tumors after radiation therapy between PRT and SRT were measurable despite the similar tumor growth delay responses. In UT15 tumors, both SRT and PRT were equally effective at reducing tumor hypoxia to a significant level as measured by (18)F-FMISO and pimonidazole.

ChemInform Abstract: Multifunctional Tin Dioxide Materials: Advances in Preparation Strategies, Microstructure, and Performance

AbstractReview: 56 refs.

Current concepts and future developments of corneal cross-linking.

The introduction of corneal cross-linking (CXL) has changed the landscape of treatment and management of keratoconus and ectasia after refractive surgery. Previously, treatment options provided only temporary visual rehabilitation without limiting disease progression. Keratoconus and ectasia resulted in significant vision-related reduction in quality of life and a substantial lifetime economic burden, with up to 20% of keratoconus cases resulting in eventual corneal transplantation [1]. CXL was introduced as the first therapeutic option for keratoconus aimed at stiffening the cornea in order to treat the underlying stromal instability. From the time that the first reports of the clinical application of cross-linking in the cornea were published in 2003 [2], CXL has rapidly been adopted as a standard therapy for treatment of progressive keratoconus in much of the world [3–5]. The potential for early intervention with corneal cross-linking before visual function has been compromised has resulted in a shift in the way we think about corneal biomechanics and has reawakened interest in the early diagnosis of ectasia. In this issue, J. Steinberg et al. report two new parameters to detect biomechanical changes in the keratoconic cornea after CXL using in vivo corneal visualization Scheimpflug technology. Research in the area of corneal biomechanics has the potential to enable earlier diagnosis of patients in need of CXL and better analysis of the effects of the procedure. While many questions remain unanswered, the understanding of the photochemical mechanisms that result in the formation of cross-links in the cornea has grown exponentially in the last decade. Improved scientific understanding of the mechanisms of CXL has driven clinical research aimed at optimizing CXL for better efficiency and efficacy [6]. In this issue, A. C. da Paz et al. present a critical review of known and as yet undetermined effects of CXL on corneal structure, biomechanics, and functional aspects. J. Antoun et al. examine patient characteristics that contribute to cross-linking failure to stabilize keratometry and examine the effect of repeat treatments on eyes that have continued to progress after primary CXL. The remaining contributions to the special issue explore modifications to the conventional protocol that incorporate new technology, such as transepithelial riboflavin formulations designed to improve patient comfort (S. Taneri et al.) and higher irradiance and pulsed UVA delivery aimed at improving procedure speed and photon efficiency (C. Mazzotta et al.). CXL combination procedures targeted at maximizing visual outcomes through the addition of simultaneous intracorneal ring implantation (P. Studeny et al.) or subsequent phakic toric implantable collamer lens insertion (R. Antonios et al.) are also discussed. Together, the papers in this special issue describe the next generation of corneal cross-linking. The contributors explore the potential to maximize CXL efficacy, provide equivalent or greater treatment effect in shorter total treatment times, reduce patient discomfort and speed visual recovery, and offer both stabilization and functional visual improvement through CXL combination procedures. Suphi Taneri Elias Jarade John A. Kanellopoulos David Muller

Trans-ungual delivery of itraconazole hydrochloride by iontophoresis

Itraconazole (ITR) is a potent antifungal drug. However, poor aqueous solubility limits its permeation ability across the human nail plate. Therefore, in this project, ITR was converted to hydrochloride salt (ITR-HCl) to improve its solubility and to render it amenable to iontophoresis. ITR-HCl was characterized by spectroscopic methods and antifungal efficacy was evaluated in comparison to the base. In vitro and ex vivo transport studies (passive and iontophoresis) were carried out across the porcine hoof membrane and excised human cadaver toe using two different protocols; continuous delivery of drug for 24 h and pulsed delivery of drug for 3 days (8 h/day). The antifungal efficacy of ITR-HCL was comparable to ITR. Iontophoresis was found to be more effective than passive mode of delivery of ITR-HCL. In both iontophoresis as well as passive mode of delivery, the pulsed protocol resulted in more ungual and trans-ungual delivery of drug than continuous protocol. ITR-HCL could be delivered into and across the nail plate by iontophoresis. Human cadaver toe appears to be a good model to investigate the ungual delivery of drugs.

Respiratory motion management using audio-visual biofeedback for respiratory-gated radiotherapy of synchrotron-based pulsed heavy-ion beam delivery.

To efficiently deliver respiratory-gated radiation during synchrotron-based pulsed heavy-ion radiotherapy, a novel respiratory guidance method combining a personalized audio-visual biofeedback (BFB) system, breath hold (BH), and synchrotron-based gating was designed to help patients synchronize their respiratory patterns with synchrotron pulses and to overcome typical limitations such as low efficiency, residual motion, and discomfort. In-house software was developed to acquire body surface marker positions and display BFB, gating signals, and real-time beam profiles on a LED screen. Patients were prompted to perform short BHs or short deep breath holds (SDBH) with the aid of BFB following a personalized standard BH/SDBH (stBH/stSDBH) guiding curve or their own representative BH/SDBH (reBH/reSDBH) guiding curve. A practical simulation was performed for a group of 15 volunteers to evaluate the feasibility and effectiveness of this method. Effective dose rates (EDRs), mean absolute errors between the guiding curves and the measured curves, and mean absolute deviations of the measured curves were obtained within 10%-50% duty cycles (DCs) that were synchronized with the synchrotron's flat-top phase. All maneuvers for an individual volunteer took approximately half an hour, and no one experienced discomfort during the maneuvers. Using the respiratory guidance methods, the magnitude of residual motion was almost ten times less than during nongated irradiation, and increases in the average effective dose rate by factors of 2.39-4.65, 2.39-4.59, 1.73-3.50, and 1.73-3.55 for the stBH, reBH, stSDBH, and reSDBH guiding maneuvers, respectively, were observed in contrast with conventional free breathing-based gated irradiation, depending on the respiratory-gated duty cycle settings. The proposed respiratory guidance method with personalized BFB was confirmed to be feasible in a group of volunteers. Increased effective dose rate and improved overall treatment precision were observed compared to conventional free breathing-based, respiratory-gated irradiation. Because breathing guidance curves could be established based on the respective average respiratory period and amplitude for each patient, it may be easier for patients to cooperate using this technique.

Electrogram-gated radiofrequency ablations with duty cycle power delivery negate effects of ablation catheter motion.

Cardiac and respiratory movements cause catheter instability. Lateral catheter sliding over target endocardial surface can lead to poor tissue contact and unpredictable lesion formation. We describe a novel method of overcoming the effects of lateral catheter sliding movements using an electrogram-gated pulsed power ablation. All ablations were performed on a thermochromic gel myocardial phantom. Ablation settings were randomized to conventional (nongated) 30 W versus electrogram-gated at 20% duty cycle (30 W average power) at 0-, 3-, 6-, and 9-mm lateral sliding distances. Forty-eight radiofrequency ablations were performed. Deeper lesions were created in electrogram-gated versus conventional ablations at 3 mm (4.36±0.08 versus 4.05±0.17 mm; P=0.009), 6 mm (4.39±0.10 versus 3.44±0.15 mm; P<0.001), and 9 mm (4.41±0.06 versus 2.94±0.16 mm; P<<0.001) sliding distances. Electrogram-gated ablations created consistent lesions at a quicker rate of growth in depth when compared with conventional ablations (P<0.001). (1) Lesion depth decreases and length increases in conventional ablations with greater degrees of lateral catheter movements; (2) electrogram-gated pulsed radiofrequency delivery negated the effects from lateral catheter movement by creating consistently deeper lesions irrespective of the degree of catheter movement; and (3) target lesion depths were reached significantly faster in electrogram-gated than in conventional ablations.

LOW FLOW OXYGEN THERAPY FROM A PORTABLE OXYGEN CONCENTRATOR OR AN OXYGEN CYLINDER EFFECTIVELY TREATS HYPOXEMIA IN ANESTHETIZED WHITE-TAILED DEER (ODOCOILEUS VIRGINIANUS)

For treatment of hypoxemia, delivery of the minimum effective oxygen flow rate is advantageous during field anesthesia because it prolongs the life of the oxygen cylinder. Portable oxygen concentrators as the oxygen source require less logistical considerations than cylinders and are a safer alternative during helicopter field work because they are nonexplosive devices. The objective of this study was to evaluate low oxygen flow rates by continuous or pulsed intranasal delivery for treatment of hypoxemia in anesthetized white-tailed deer (Odocoileus virginianus). Nine captive adult female deer (body mass 56-72 kg) were physically restrained in a drop-floor chute and hand injected intramuscularly with medetomidine (0.1-0.14 mg/kg) and ketamine (2.5-4.3 mg/kg). Intranasal oxygen was delivered from an oxygen cylinder at continuous flow rates of 1 and 2 L/min or from a battery driven oxygen concentrator (EverGo Portable Oxygen Concentrator, Respironics) with pulse-dose delivery (maximum capacity of 1.05 L/min). The pulse-dose setting (pulse volume 12-70 ml) was adjusted according to the respiratory rate. Arterial blood gases were analyzed before, during, and after O2 supplementation. A 10-min washout period was allowed between treatment groups. All three treatments adequately treated hypoxemia. The partial pressure of arterial oxygenation increased significantly from baseline values of 55 +/- 10 to 115 +/- 31 mm Hg during supplementation from the oxygen concentrator, to 138 +/- 21 mm Hg during supplementation from the oxygen cylinder at 1 L/min, and to 201 +/- 42 mm Hg at 2 L/min. In conclusion, low flow rates of intranasal oxygen supplemented continuously from an oxygen cylinder or by pulsed delivery from a portable oxygen concentrator effectively treated hypoxemia in anesthetized white-tailed deer.