A wear simulation study of nanostructured CVD diamond-on-diamond articulation involving concave/convex mating surfaces

Using microwave-plasma Chemical Vapor Deposition (CVD), a 3-micron thick nanostructured-diamond (NSD) layer was deposited onto polished, convex and concave components that were machined from Ti-6Al-4V alloy. These components had the same radius of curvature, 25.4mm. Wear testing of the surfaces was performed by rotating articulation of the diamond-deposited surfaces (diamond-on-diamond) with a load of 225N for a total of 5 million cycles in bovine serum resulting in polishing of the diamond surface and formation of very shallow, linear wear grooves of less than 50nm depth. The two diamond surfaces remained adhered to the components and polished each other to an average surface roughness that was reduced by as much as a factor of 80 for the most polished region located at the center of the condyle. Imaging of the surfaces showed that the initial wearing-in phase of diamond was only beginning at the end of the 5 million cycles. Atomic force microscopy, scanning electron microscopy, Raman spectroscopy, and surface profilometry were used to characterize the surfaces and verify that the diamond remained intact and uniform over the surface, thereby protecting the underlying metal. These wear simulation results show that diamond deposition on Ti alloy has potential application for joint replacement devices with improved longevity over existing devices made of cobalt chrome and ultra-high molecular weight polyethylene (UHMWPE).

Global climate evolution during the last deglaciation

Deciphering the evolution of global climate from the end of the Last Glacial Maximum approximately 19 ka to the early Holocene 11 ka presents an outstanding opportunity for understanding the transient response of Earth's climate system to external and internal forcings. During this interval of global warming, the decay of ice sheets caused global mean sea level to rise by approximately 80 m; terrestrial and marine ecosystems experienced large disturbances and range shifts; perturbations to the carbon cycle resulted in a net release of the greenhouse gases CO(2) and CH(4) to the atmosphere; and changes in atmosphere and ocean circulation affected the global distribution and fluxes of water and heat. Here we summarize a major effort by the paleoclimate research community to characterize these changes through the development of well-dated, high-resolution records of the deep and intermediate ocean as well as surface climate. Our synthesis indicates that the superposition of two modes explains much of the variability in regional and global climate during the last deglaciation, with a strong association between the first mode and variations in greenhouse gases, and between the second mode and variations in the Atlantic meridional overturning circulation.

Education in airway management

In airway management, poor judgment, education and training are leading causes of patient morbidity and mortality. The traditional model of medical education, which relies on experiential learning in the clinical environment, is inconsistent and often inadequate. Curriculum change is underway in many medical organisations in an effort to correct these problems, and airway management is likely to be explicitly addressed as a clinical fundamental within any new anaesthetic curriculum. Competency-based medical education with regular assessment of clinical ability is likely to be introduced for all anaesthetists engaged in airway management. Essential clinical competencies need to be defined and improvements in training techniques can be expected based on medical education research. Practitioners need to understand their equipment and diversify their airway skills to cope with a variety of clinical presentations. Expertise stems from deliberate practice and a desire constantly to improve performance with a career-long commitment to education.

Failure to ventilate with supraglottic airways after drowning

We report the failure of an i-gel and an Ambu AuraOnce supraglottic airway to ventilate a drowning victim. Failure was attributed to changes in lung physiology following submersion and inhalation of water that may have required ventilation pressures up to 40 cmH2O to treat the victim's hypoxaemia. The ease of use and rapid insertion of supraglottic airways without interrupting cardiac compression has prompted recommendations for their use during resuscitation. The relatively low leak pressures attainable from many supraglottic airways, however may cause inadequate lung ventilation and entrainment of air into the stomach when these devices are used in drowning victims.

Dermatofibrosarcoma protuberans arising in a decorative tattoo

Dermatofibrosarcoma protuberans (DFSP) is an uncommon, locally aggressive cutaneous tumour of intermediate grade malignancy. A number of reports have linked local trauma of varying aetiology with the later development of DFSP. In addition, a variety of skin disorders and, in rare cases, cutaneous tumours, have been described in association with decorative tattoos. This is often associated with delayed diagnosis. We report the first case of DFSP arising in a tattoo and discuss the available evidence for a causative link between DFSP and local trauma of this nature.

An audit of laryngoscopes and application of a new ISO standard

OBJECTIVE

The International Organization for Standardization (ISO) recently published an International Standard (ISO 7376:2009) which specifies illuminance levels and tests for illumination from hook-on type laryngoscopes used for intubation. A clinical study examining luminance for laryngoscopy found that 100 cd·m(-2) was the minimum level acceptable for laryngoscopy. The purpose of this study was to measure the quality of light from laryngoscopes available for use by anesthetists in an anesthetic department and compare them to the ISO illuminance standard and published minimum acceptable luminance limits.

METHODS

A measuring device was constructed to support each laryngoscope in a standardized manner. For 190 reusable laryngoscopes, illuminance was measured with a lux meter at the base of this device. Eighteen clinically available laryngoscopes were then examined in detail, as a snapshot study, with multiple light recordings according to the ISO Standard. We also measured the luminance provided by each laryngoscope.

RESULTS

Only two of the 18 laryngoscopes met the minimum illuminance level of 500 lux after 10 min. Nine laryngoscopes provided a luminance <100 cd·m(-2), which is the reported minimum required luminance for laryngoscopy. None of the 18 laryngoscopes tested complied with the ISO standard for laryngoscope light distribution.

CONCLUSIONS

Laryngoscope light should be regularly audited. Results from these audits can be used to retire or repair substandard laryngoscopes to maintain acceptable standards of laryngoscope light. Audit results produce tangible evidence that is useful when applying for capital expenditure. Light measurements are not easy to make. There needs to be a convenient device to reliably measure laryngoscope illumination.

Equipment to manage a difficult airway during anaesthesia

Airway complications are a leading cause of morbidity and mortality in anaesthesia. Effective management of a difficult airway requires the timely availability of suitable airway equipment. The Australian and New Zealand College of Anaesthetists has recently developed guidelines for the minimum set of equipment needed for the effective management of an unexpected difficult airway (TG4 [2010] www.anzca.edu.au/resources/professionaldocuments). TG4 [2010] is based on expert consensus, underpinned by wide consultation and an extensive review of the available evidence, which is summarised in a Background Paper (TG4 BP [2010] www.anzca.edu.au/ resources/professional-documents). TG4 [2010] will be reviewed at the end of one year and thereafter every five years or more frequently if necessary. The current paper is reproduced directly from the Background Paper (TG4 BP [2010]).

A prospective randomized trial comparing supraglottic airways for flexible bronchoscopy in children

OBJECTIVE

A prospective randomized, controlled trial was conducted comparing supraglottic airways (SGA) for flexible bronchoscopy in 100 children.

BACKGROUND

Pediatric flexible bronchoscopy is commonly performed using a SGA as both a ventilation device and a conduit for flexible bronchoscopy. We observed that some disposable SGAs were associated with increased resistance to bronchoscope manipulation compared to the LMA Classic (cLMA).

METHODS

We compared the cLMA to the Ambu Aura Once, Portex Soft Seal, Boss Systems disposable silicone laryngeal mask, and LMA Unique. We recorded the subjective resistance of the bronchoscope manipulation within the SGA by linear analog score and measured the time to insert the bronchoscope from the proximal end of the SGA to the right upper lobe. We also scored the view of the larynx through the bronchoscope and measured SGA cuff pressures.

RESULTS

Resistance to bronchoscope manipulation during pediatric flexible bronchoscopy was higher using polyvinyl chloride (PVC) disposable SGAs (Ambu, Unique, and Portex) than the silicone re-usable cLMA (P < 0.0001). The Unique and Ambu laryngeal masks were clinically inferior to the cLMA at all levels of the airway (P < 0.0001). The Portex Soft Seal was not different above the larynx but was significantly statistically inferior at (P < 0.04) and below the larynx (P < 0.006) and inferior overall (P < 0.007). Boss Systems single-use laryngeal mask was as effective as the cLMA.

CONCLUSION

In this trial, PVC single-use laryngeal masks were inferior to the silicone cLMA and Boss Systems laryngeal masks for flexible bronchoscopy in children.

Constraints on the formation of sedimentary dolomite

The experimental replacement of calcite and aragonite by dolomite under a variety of conditions indicates that dolomitization can take place in marine and lacustrine environments under two conditions: (i) low dissolved sulfate concentrations and (ii) insubstantial contemporaneous silica diagenesis. Common sites for dolomite formation are areas where the dissolved sulfate concentration is reduced by microbial sulfate reduction, through the mixing of seawater with large amounts of fresh water, or where low-sulfate alkaline lacustrine environments prevail. Even under these conditions, dolomite formation may be inhibited by the concurrent transformation of opal-A (amorphous silica) to opal-CT (disordered cristobalite and tridymite), whereas the subsequent transformation of opal-CT to quartz favors the formation of dolomite.

How did the Macintosh laryngoscope become so popular?

The Macintosh laryngoscope has been described as 'the most numerously and widely made durable item in the history of anesthesia' (Sir Anthony Jephcott, February 6, 1983). This laryngoscope was originally designed to facilitate intubation in unparalyzed patients and became universally adopted by the anesthetic community. In spite of enormous subsequent changes in anesthetic practice, the Macintosh laryngoscope continues to dominate 50 years after its key indication has become obsolete. This study explores the development and success of this ubiquitous instrument.

Experimental adaptation of the Enk oxygen flow modulator for potential pediatric use

AIM

A bench study of the Enk oxygen flow modulator (Enk OFM) was conducted to test its performance and potential use in pediatric patients using the Advanced Paediatric Life Support (APLS) guidelines (Advanced Paediatric Life Support, 2005: 224).

BACKGROUND

The Enk OFM is a preassembled emergency transtracheal ventilation device.

METHODS

The Enk OFM was connected to two sources of oxygen: first, to a Precision Medical flowmeter and second, to an Aestiva anesthetic machine axillary flowmeter. Testing was performed on standard cannulae of 20, 18, and 16 gauge caliber and also a 7.5 cm 15G Emergency Transtracheal Airway Catheter (Cook Medical). Serial hole occlusion of the Enk OFM was applied and the resulting flow rates were measured by a RespiCal Timeter.

RESULTS

Oxygen flow was best controlled by occluding all holes of the Enk OFM and incrementally increasing oxygen flow by the flowmeter with an initial setting of 1 l min(-1) year(-1) of age. Contrary to the original description of this device (Anesth Analg 1998; 86: 203S), sequential occlusion of the five side holes does not lead to a significant exponential increase in gas flow. Incomplete occlusion of the Enk OFM provided insufficient and unpredictable flow.

CONCLUSIONS

The Enk OFM should be fully occluded for inspiration with flow rates set at 1 l min(-1) year(-1) of age and adjusted to effect. These flow rates are consistent with the APLS recommendations. Flows above 15 l min(-1) are potentially dangerous and the Enk OFM fails to perform as an on-off device. Flowmeter settings of <1 l min(-1) risk no flow. Cannulae of at least 18G should be used for optimal flow.

Functional gracilis flap in thenar reconstruction

Restoration of lost opposition in the context of significant thenar soft tissue defects represents a tremendous reconstructive challenge. Free functioning muscle transfer has been described in this context and has the advantage of providing both a functioning muscle unit as well as soft tissue coverage in a single reconstructive procedure. It adds to the injured limb, and by sparing donor tendons avoids the need for re-education of motor function. We describe the use of a free innervated gracilis muscle flap for functional thenar reconstruction in two unique cases following extensive traumatic loss of thenar skin and musculature. Crucially, in each case, the recurrent motor branch of the median nerve had been destroyed at its point of insertion into the thenar muscle remnants.

AIM

To date, the main reported disadvantages of free functioning muscle transfer in thenar reconstruction include difficult flap dissections, donor site morbidity, inadequate strength and excursion of the transplanted muscle and excessively bulky flaps. Our aim was, as far as possible, to address these issues.

SURGICAL PROCEDURE

Each thenar defect was measured and a corresponding segment of gracilis muscle, measured in situ, was raised on the proximal neurovascular pedicle. End-side microvascular anastomosis was performed between the medial circumflex femoral artery and the radial artery. The venae comitantes of the pedicle were anastomosed end-end with those of the radial artery and also with the cephalic vein. Epineural anastomosis was performed between the motor branch of the obturator nerve and the recurrent motor branch of the median nerve. Each flap was covered with a split thickness skin graft.

RESULTS

Both flaps survived without any complication. Both patients regained excellent voluntary thumb opposition, sufficient to allow return to full-time employment, and had restoration of sufficient thenar bulk. This was achieved with minimal donor site morbidity.

CONCLUSIONS

Restoration of lost opposition, in the context of significant thenar soft tissue defects, can be achieved using a free functional gracilis flap. This produces clinically excellent functional results and can be carried out as a single stage reconstructive procedure. This is a novel application of a tremendously versatile donor muscle in functioning free muscle transfer.

Airway management during an EXIT procedure for a fetus with dysgnathia complex

Nonsyndromal dysgnathia is a rare disorder with a probable genetic basis characterized by a hypoplastic or absent mandible (agnathia), microstomia, microglossia, and ear anomalies secondary to a defect in the ventral portion of the first branchial arch caused by defective neural crest migration or proliferation. Dysgnathic newborn infants often suffer fatal respiratory failure from airway obstruction. Nineteen children with isolated dysgnathia complex are described in the literature--six were stillborn, eight died shortly after birth, and only five survived infancy. All survivors required tracheostomy to maintain an airway. It is difficult to intubate the trachea of these children and early airway management planning is important. We report a neonate who presented with a prenatal ultrasound diagnosis of severe micrognathia, polyhydramnios and a family history of severe micrognathia. Airway management was achieved with fiberoptic intubation through a laryngeal mask airway (LMA) during an ex utero intrapartum treatment procedure. Fiberoptic intubation was hampered by copious amounts of amniotic fluid. This child and her sibling are the first two siblings with isolated dysgnathia complex to have survived infancy and provide further support for a genetic basis to this condition.

Early warming of tropical South America at the last glacial-interglacial transition

Glaciation in the humid tropical Andes is a sensitive indicator of mean annual temperature. Here, we present sedimentological data from lakes beyond the glacial limit in the tropical Andes indicating that deglaciation from the Last Glacial Maximum led substantial warming at high northern latitudes. Deglaciation from glacial maximum positions at Lake Titicaca, Peru/Bolivia (16 degrees S), and Lake Junin, Peru (11 degrees S), occurred 22,000 to 19,500 calendar years before the present, several thousand years before the Bølling-Allerød warming of the Northern Hemisphere and deglaciation of the Sierra Nevada, United States (36.5 degrees to 38 degrees N). The tropical Andes deglaciated while climatic conditions remained regionally wet, which reflects the dominant control of mean annual temperature on tropical glaciation.

Low-temperature growth of nanostructured diamond films

Nanostructured diamond films are grown on a titanium alloy substrate using a two-step deposition process. The first step is performed at elevated temperature (820 degrees C) for 30 min using a H2/CH4/N2 gas mixture to grow a thin (approximately 600 nm) nanostructured diamond layer and to improve film adhesion. The remainder of the deposition involves growth at low temperature (< 600 degrees C) in a H2/CH4/O2 gas mixture. The continuation of the smooth nanostructured diamond film growth during low-temperature deposition is confirmed by in situ laser reflectance interferometry, atomic force microscopy, micro-Raman spectroscopy, and surface profilometry. Similar experiments performed without the initial nanostructured diamond layer resulted in poorly adhered films with a more crystalline appearance and a higher surface roughness. This low-temperature deposition of nanostructured diamond films on metals offers advantages in cases where high residual thermal stress leads to delamination at high temperatures.