The effect of high-flow nasal oxygen flow rate on gas exchange in apnoeic patients: a randomised controlled trial.

High-flow nasal oxygen can be administered at induction of anaesthesia for the purposes of pre-oxygenation and apnoeic oxygenation. This intervention is claimed to enhance carbon dioxide elimination during apnoea, but the extent to which this occurs remains poorly quantified. The optimal nasal oxygen flow rate for gas exchange is also unknown. In this study, 114 patients received pre-oxygenation with high-flow nasal oxygen at 50 l.min-1. At the onset of apnoea, patients were allocated randomly to receive one of three nasal oxygen flow rates: 0 l.min-1; 70 l.min-1; or 120 l.min-1. After 4 minutes of apnoea, all oxygen delivery was ceased, tracheal intubation was performed, and oxygen delivery was recommenced when SpO2 was 92%. Mean (SD) PaCO2 rise during the first minute of apnoea was 1.39 (0.39) kPa, 1.41 (0.29) kPa, and 1.26 (0.38) kPa in the 0 l.min-1, 70 l.min-1 and 120 l.min-1 groups, respectively; p = 0.16. During the second, third and fourth minutes of apnoea, mean (SD) rates of rise in PaCO2 were 0.34 (0.08) kPa.min-1, 0.36 (0.06) kPa.min-1 and 0.37 (0.07) kPa.min-1 in the 0 l.min-1, 70 l.min-1 and 120 l.min-1 groups, respectively; p = 0.17. After 4 minutes of apnoea, median (IQR [range]) arterial oxygen partial pressures in the 0 l.min-1, 70 l.min-1 and 120 l.min-1 groups were 24.5 (18.6-31.4 [12.3-48.3]) kPa; 36.6 (28.1-43.8 [9.8-56.9]) kPa; and 37.6 (26.5-45.4 [11.0-56.6]) kPa, respectively; p < 0.001. Median (IQR [range]) times to desaturate to 92% after the onset of apnoea in the 0 l.min-1, 70 l.min-1 and 120 l.min-1 groups, were 412 (347-509 [190-796]) s; 533 (467-641 [192-958]) s; and 531 (462-681 [326-1007]) s, respectively; p < 0.001. In conclusion, the rate of carbon dioxide accumulation in arterial blood did not differ significantly between apnoeic patients who received high-flow nasal oxygen and those who did not.

Pre-oxygenation with facemask oxygen vs high-flow nasal oxygen vs high-flow nasal oxygen plus mouthpiece: a randomised controlled trial.

High-flow nasal oxygen used before and during apnoea prolongs time to desaturation at induction of anaesthesia. It is unclear how much oxygenation before apnoea prolongs this time. We randomly allocated 84 participants to 3 minutes of pre-oxygenation by one of three methods: 15 l.min-1 by facemask; 50 l.min-1 by high-flow nasal cannulae only; or 50 l.min-1 by high-flow nasal cannulae plus 15 l.min-1 by mouthpiece. We then anaesthetised and intubated the trachea of 79 participants and waited for oxygen saturation to fall to 92%. Median (IQR [range]) times to desaturate to 92% after pre-oxygenation with facemask oxygen, high-flow nasal oxygen only and high-flow nasal oxygen with mouthpiece, were: 309 (208-417 [107-544]) s; 344 (250-393 [194-585]) s; and 386 (328-498 [182-852]) s, respectively, p = 0.014. Time to desaturation after facemask pre-oxygenation was shorter than after combined nasal and mouthpiece pre-oxygenation, p = 0.006. We could not statistically distinguish high-flow nasal oxygen without mouthpiece from the other two groups for this outcome. Median (IQR [range]) arterial oxygen partial pressure after 3 minutes of pre-oxygenation by facemask, nasal cannulae and nasal cannulae plus mouthpiece, was: 49 (36-61 [24-66]) kPa; 57 (48-62 [30-69]) kPa; and 61 (55-64 [36-72]) kPa, respectively, p = 0.003. Oxygen partial pressure after 3 minutes of pre-oxygenation with nasal and mouthpiece combination was greater than after facemask pre-oxygenation, p = 0.002, and after high-flow nasal oxygen alone, p = 0.016. We did not reject the null hypothesis for the pairwise comparison of facemask pre-oxygenation and high-flow nasal pre-oxygenation, p = 0.14.

Increasing stomatal conductance in response to rising atmospheric CO2.

Background and Aims: Studies have indicated that plant stomatal conductance (gs) decreases in response to elevated atmospheric CO2, a phenomenon of significance for the global hydrological cycle. However, gs increases across certain CO2 ranges have been predicted by optimization models. The aim of this work was to demonstrate that under certain environmental conditions, gs can increase in response to elevated CO2. Methods: Using (1) an extensive, up-to-date synthesis of gs responses in free air CO2 enrichment (FACE)experiments, (2) in situ measurements across four biomes showing dynamic gs responses to a CO2 rise of ~50 ppm (characterizing the change in this greenhouse gas over the past three decades) and (3) a photosynthesis-stomatal conductance model, it is demonstrated that gs can in some cases increase in response to increasing atmospheric CO2. Key Results: Field observations are corroborated by an extensive synthesis of gs responses in FACE experiments showing that 11.8 % of gs responses under experimentally elevated CO2 are positive. They are further supported by a strong data-model fit (r2 = 0.607) using a stomatal optimization model applied to the field gs dataset. A parameter space identified in the Farquhar-Ball-Berry photosynthesis-stomatal conductance model confirms field observations of increasing gs under elevated CO2 in hot dry conditions. Contrary to the general assumption, positive gs responses to elevated CO2, although relatively rare, are a feature of woody taxa adapted to warm, low-humidity conditions, and this response is also demonstrated in global simulations using the Community Land Model (CLM4). Conclusions: The results contradict the over-simplistic notion that global vegetation always responds with decreasing gs to elevated CO2, a finding that has important implications for predicting future vegetation feedbacks on the hydrological cycle at the regional level.

Corrigendum: Palaeo leaf economics reveal a shift in ecosystem function associated with the end-Triassic mass extinction event.

This corrects the article DOI: 10.1038/nplants.2017.104.

Palaeo leaf economics reveal a shift in ecosystem function associated with the end-Triassic mass extinction event.

Climate change is likely to have altered the ecological functioning of past ecosystems, and is likely to alter functioning in the future; however, the magnitude and direction of such changes are difficult to predict. Here we use a deep-time case study to evaluate the impact of a well-constrained CO2-induced global warming event on the ecological functioning of dominant plant communities. We use leaf mass per area (LMA), a widely used trait in modern plant ecology, to infer the palaeoecological strategy of fossil plant taxa. We show that palaeo-LMA can be inferred from fossil leaf cuticles based on a tight relationship between LMA and cuticle thickness observed among extant gymnosperms. Application of this new palaeo-LMA proxy to fossil gymnosperms from East Greenland reveals significant shifts in the dominant ecological strategies of vegetation found across the Triassic-Jurassic transition. Late Triassic forests, dominated by low-LMA taxa with inferred high transpiration rates and short leaf lifespans, were replaced in the Early Jurassic by forests dominated by high-LMA taxa that were likely to have slower metabolic rates. We suggest that extreme CO2-induced global warming selected for taxa with high LMA associated with a stress-tolerant strategy and that adaptive plasticity in leaf functional traits such as LMA contributed to post-warming ecological success.

Differences in the photosynthetic plasticity of ferns and Ginkgo grown in experimentally controlled low [O2]:[CO2] atmospheres may explain their contrasting ecological fate across the Triassic-Jurassic mass extinction boundary.

Background and Aims: Fluctuations in [CO 2 ] have been widely studied as a potential driver of plant evolution; however, the role of a fluctuating [O 2 ]:[CO 2 ] ratio is often overlooked. The present study aimed to investigate the inherent physiological plasticity of early diverging, extant species following acclimation to an atmosphere similar to that across the Triassic-Jurassic mass extinction interval (TJB, approx. 200 Mya), a time of major ecological change. Methods: Mature plants from two angiosperm ( Drimys winteri and Chloranthus oldhamii ), two monilophyte ( Osmunda claytoniana and Cyathea australis ) and one gymnosperm ( Ginkgo biloba ) species were grown for 2 months in replicated walk-in Conviron BDW40 chambers running at TJB treatment conditions of 16 % [O 2 ]-1900 ppm [CO 2 ] and ambient conditions of 21 % [O 2 ]-400 ppm [CO 2 ], and their physiological plasticity was assessed using gas exchange and chlorophyll fluorescence methods. Key Results: TJB acclimation caused significant reductions in the maximum rate of carboxylation ( V Cmax ) and the maximum electron flow supporting ribulose-1,5-bisphosphate regeneration ( J max ) in all species, yet this downregulation had little effect on their light-saturated photosynthetic rate ( A sat ). Ginkgo was found to photorespire heavily under ambient conditions, while growth in low [O 2 ]:[CO 2 ] resulted in increased heat dissipation per reaction centre ( DI o / RC ), severe photodamage, as revealed by the species' decreased maximum efficiency of primary photochemistry ( F v / F m ) and decreased in situ photosynthetic electron flow ( Jsitu ). Conclusions: It is argued that the observed photodamage reflects the inability of Ginkgo to divert excess photosynthetic electron flow to sinks other than the downregulated C 3 and the diminished C 2 cycles under low [O 2 ]:[CO 2 ]. This finding, coupled with the remarkable physiological plasticity of the ferns, provides insights into the underlying mechanism of Ginkgoales' near extinction and ferns' proliferation as atmospheric [CO 2 ] increased to maximum levels across the TJB.

Should money follow the patient: Financial implication for being the National Centre for the Treatment and Management of Pelvic and Acetabular Fractures in Ireland.

BACKGROUND: Pelvic and acetabular fractures are complex injuries requiring specialist treatment. Our institution is the National Centre for Treatment and Management of these injuries. AIM: To audit all referrals to our institution over a 6-month period and calculate the cost incurred by being the national referral centre. METHODS: Retrospective review of database, and subsequent allocation of Casemix points to assess total cost of treatment for each patient referred to our institution. RESULTS: 103 patients referred with pelvic or acetabular fracture for operative management. The furthest referral distance was 181miles. Over-all, the length of stay was 15.4 days. The average inclusive cost for a referral to our unit for operative management was €16,302. CONCLUSION: Pelvic and acetabular fractures are complex injuries that require specialist referral unit management. However for these units to remain sustainable money needs to "follow the patient".

Pelvic and acetabular fractures.

Patients that sustain pelvic and/or acetabular trauma in Ireland and require surgical intervention are treated at the Adelaide and Meath National Children's Hospital (AMNCH). For this study an audit was conducted of all pelvic and acetabular fractures referred to the AMNCH over a 12 month period from July 2010 to June 2011. This study was conducted with the purpose of recording the different fracture patterns, methods of injury and surgical procedures performed over this time frame. The results demonstrate that 109 patients were referred to the AMNCH with the majority of these fractures being sustained as the result of an RTA (43) or a fall from a height (45). Seventy one patients suffered an acetabular fracture while 43 patients suffered a fracture of their pelvic ring with some patients suffering both. There were 129 surgical procedures performed with 25 patients having more than one surgical procedure.

Determination of the utility of the Intubation Difficulty Scale for use with indirect laryngoscopes.

The purpose of this study was to determine whether the Intubation Difficulty Scale is meaningful when used with indirect laryngoscopes. Data were analysed from previously published clinical trials from our group that compared the indirect laryngoscopes with the Macintosh laryngoscope. For each laryngoscope type, the Intubation Difficulty Scale score obtained for each tracheal intubation was correlated with data for duration of the intubation attempt and with the user rated difficulty of the intubation attempt. The strengths of the correlations between these indices were then compared for tracheas intubated with the Macintosh vs the indirect laryngoscopes. The Intubation Difficulty Scale performed well when compared with data for duration and user rated difficulty of the intubation attempts for the both direct and indirect laryngoscopy. However, the correlation between the Intubation Difficulty Scale score and both user rated difficulty (p = 0.001) and the duration of tracheal intubation (p = 0.003) were significantly stronger for the Macintosh laryngoscope compared with the indirect laryngoscopes. In contrast, the correlation between user rated difficulty scores and the data for duration of tracheal intubation was not different between the device types. The Intubation Difficulty Scale performs less well with indirect laryngoscopes than with the Macintosh laryngoscope. These findings suggest the need for caution with the use of this score with indirect laryngoscopes.

Comparison of the C-MAC®, Airtraq®, and Macintosh laryngoscopes in patients undergoing tracheal intubation with cervical spine immobilization.

BACKGROUND: We aimed at comparing the performance of the C-MAC®, Airtraq®, and Macintosh laryngoscopes when performing tracheal intubation in patients undergoing neck immobilization using manual inline axial cervical spine stabilization. METHODS: Ninety consenting patients presenting for surgery requiring tracheal intubation were randomly assigned to undergo intubation using a C-MAC® (n=30), Airtraq® (n=29), or Macintosh (n=31) laryngoscope. All patients were intubated by one anaesthetist experienced in the use of each laryngoscope. RESULTS: The Airtraq® laryngoscope performed best in these patients, reducing the Intubation Difficulty Scale score, improving the Cormack and Lehane glottic view, and reducing the need for optimization manoeuvres, compared with both the Macintosh and the C-MAC®. The C-MAC® and Macintosh laryngoscopes performed similarly. There were no differences in success rates or haemodynamic profiles post-intubation between any of the devices tested. CONCLUSIONS: The Airtraq® laryngoscope performed better than the C-MAC® and Macintosh laryngoscopes in patients undergoing cervical immobilization.

Self-reported complication rates following primary total hip arthroplasty in Ireland: fact or fiction.

BACKGROUND: There are little data available on complication rates following primary total hip arthroplasty (THA) surgery in Ireland. AIMS: To determine self-reported complication rates and national data for primary THA. METHODS: A postal questionnaire surveyed Irish orthopaedic association consultant members. Additional data were obtained from the economic and social research institute (ESRI). RESULTS: We achieved an 83% response rate. 5,424 THAs were self-reported. Mean dislocation rates were 1%, but higher using a posterior surgical approach (p < 0.05). Mean deep infection rates were 0.4%. 29% were MRSA. No reduction was reported from additional barrier prophylaxes. Mean venous thrombo-embolism (VTE) rates were 3.5%. No reduction was reported from commencing prophylaxis preoperatively or extending treatment duration. National rates for dislocation, deep infection and VTE were 25.7, 0.87, and <0.1%, respectively. CONCLUSIONS: The creation of a National Hip Register is strongly recommended. A register would improve surgical practices and patient outcomes, and provide significant healthcare savings.

Irish (Republic) versus British (North West) orthopaedic trainees: what are the differences?

British Trainees have gradually had their working week curtained over the last 8 years. The Republic of Ireland Trainees have not been subjected to the European Working Time Directive prior to 2009 and have therefore worked on average, more hours than their British counterparts. We wanted to see if the differing schemes had an impact on recruiting and training orthopaedic surgeons. We surveyed Republic of Ireland orthopaedic specialist registrars (SpRs) and North West (NW) British SpRs/specialist trainees (ST3 and above) to see if there were any discernable differences in working patterns and subsequent training exposure. A standard proforma was given to Irish Trainees and to NW SpRs/STs at their National or regional teaching (January/February 2009). 62% of Irish and 47% of British NW Trainees responded. Irish trainees were more likely to have obtained a post-graduate degree (p = 0.03). The Irish worked more hours per week (p < 0.001) doing more trauma operative lists (p = 0.003) and more total cases per 6 months than the NW British (p = 0.003). This study suggests that more hours worked, equals more operative exposure, without detriment to the academic side of training. Obviously it is not possible to say whether fewer operations make for a poorer surgeon, but the evidence suggests that it may be true.

Determination of the optimal stylet strategy for the C-MAC videolaryngoscope.

The C-MAC videolaryngoscope is a novel intubation device that incorporates a camera system at the end of its blade, thereby facilitating obtaining a view of the glottis without alignment of the oral, pharyngeal and tracheal axes. It retains the traditional Macintosh blade shape and can be used as a direct or indirect laryngoscope. We wished to determine the optimal stylet strategy for use with the C-MAC. Ten anaesthetists were allowed up to three attempts to intubate the trachea in one easy and three progressively more difficult laryngoscopy scenarios in a SimMan manikin with four tracheal tube stylet strategies: no stylet; stylet; directional stylet (Parker Flex-It); and hockey-stick stylet. The use of a stylet conferred no advantage in the easy laryngoscopy scenario. In the difficult scenarios, the directional and hockey-stick stylets performed best. In the most difficult scenario, the median (IQR [range]) duration of the successful intubation attempt was lowest with the hockey-stick stylet; 18 s (15-22 [12-43]) s, highest with the unstyletted tracheal tube; 60 s (60-60 [60, 60]) s and styletted tracheal tube 60 s (29-60 [18-60]) s, and intermediate with the directional stylet 21 s (15-60 [8-60]) s. The use of a stylet alone does not confer benefit in the setting of easy laryngoscopy. However, in more difficult laryngoscopy scenarios, the C-MAC videolaryngoscope performs best when used with a stylet that angulates the distal tracheal tube. The hockey-stick stylet configuration performed best in the scenarios tested.

Comparison of the C-MAC videolaryngoscope with the Macintosh, Glidescope, and Airtraq laryngoscopes in easy and difficult laryngoscopy scenarios in manikins.

The C-MAC comprises a Macintosh blade connected to a video unit. The familiarity of the Macintosh blade, and the ability to use the C-MAC as a direct or indirect laryngoscope, may be advantageous. We wished to compare the C-MAC with Macintosh, Glidescope and Airtraq laryngoscopes in easy and simulated difficult laryngoscopy. Thirty-one experienced anaesthetists performed tracheal intubation in an easy and difficult laryngoscopy scenario. The duration of intubation attempts, success rates, number of intubation attempts and of optimisation manoeuvres, the severity of dental compression, and difficulty of device use were recorded. In easy laryngoscopy, the duration of tracheal intubation attempts were similar with the C-MAC, Macintosh and Airtraq laryngoscopes; the Glidescope performed less well. The C-MAC and Airtraq provided the best glottic views, but the C-MAC was rated as the easiest device to use. In difficult laryngo-scopy the C-MAC demonstrated the shortest tracheal intubation times. The Airtraq provided the best glottic view, with the Macintosh providing the worst view. The C-MAC was the easiest device to use.

Limits for combustion in low O2 redefine paleoatmospheric predictions for the Mesozoic.

Several studies have attempted to determine the lower limit of atmospheric oxygen under which combustion can occur; however, none have been conducted within a fully controlled and realistic atmospheric environment. We performed experimental burns (using pine wood, moss, matches, paper, and a candle) at 20 degrees C in O2 concentrations ranging from 9 to 21% and at ambient and high CO2 (2000 parts per million) in a controlled environment room, which was equipped with a thermal imaging system and full atmospheric, temperature, and humidity control. Our data reveal that the lower O2 limit for combustion should be increased from 12 to 15%. These results, coupled with a record of Mesozoic paleowildfires, are incompatible with the prediction of prolonged intervals of low atmospheric O2 levels (10 to 12%) in the Mesozoic.

Rapid prototyping in the assessment, classification and preoperative planning of acetabular fractures.

AIM: To evaluate the use of rapid prototyping in the assessment, classification and preoperative planning of acetabular fractures. INTRODUCTION: The complex three-dimensional anatomy of the pelvis and acetabulum make assessment, classification and treatment of fractures of these structures notoriously difficult. Conventional imaging only provides two-dimensional images of these fractures. While interpretation of traditional imaging techniques becomes better with experience, novel techniques may assist in the understanding of these complex injuries. METHODS: Twenty patients with acetabular fractures were studied. Life size three-dimensional models were manufactured from standardised CT scans, using the rapid prototyping process, selective laser sintering. Each model was presented to the operating surgeon prior to surgery. The surgeons found that the models greatly assisted in their understanding of the personality of the fracture. Three consultant orthopaedic surgeons and three senior trainees were asked to classify each fracture using conventional radiographs (AP pelvis, Judet views and CT scans) and then using the model. The kappa statistic was used to evaluate inter- and intraobserver agreement. RESULTS: Interobserver agreement was not absolute using either conventional radiographs or the models. For the consultants the kappa statistic using conventional radiographs was 0.61 while the kappa value using the model was 0.76 (p<0.05). For the trainees the kappa value was 0.42, using conventional radiographs and 0.71 using the model (p<0.01). CONCLUSION: Full sized models of acetabular fractures greatly assisted surgeons understand the personality of complex fractures prior to surgery and have been shown in this study to significantly reduced the degree of interobserver variability in fracture classification. This effect is particularly evident for less experienced surgeons. This technique is available and relatively inexpensive. The use of these models should prove invaluable as a tool to aid clinical practice.

Assessment of the "nearly normal" cervical spine radiograph: C2-C3 pseudosubluxation in an adult with whiplash injury.

C2-C3 pseudosubluxation is a well recognized normal anatomical variant in children and this physiological spondylolisthesis often makes the interpretation of paediatric cervical spine radiographs difficult. In direct contrast, this finding is rare in adults and has not been reported as a diagnostic difficulty following neck injury. We report a case of C2-C3 pseudosubluxation occurring in a 27 year old woman presenting with neck pain 1 week after a road traffic accident. Although there are effective radiological guidelines for cervical spine radiograph evaluation in children, there is no evidence that these can be applied to the adult cervical spine. Flexion and extension cervical spine views have limitations. In such cases, magnetic resonance imaging is required to definitively exclude pathological injury.