Physiological dead space and alveolar ventilation in ventilated infants.

BACKGROUND: Dead space is the volume not taking part in gas exchange and, if increased, could affect alveolar ventilation if there is too low a delivered volume. We determined if there were differences in dead space and alveolar ventilation in ventilated infants with pulmonary disease or no respiratory morbidity. METHODS: A prospective study of mechanically ventilated infants was undertaken. Expiratory tidal volume and carbon dioxide levels were measured. Volumetric capnograms were constructed to calculate the dead space using the modified Bohr-Enghoff equation. Alveolar ventilation (VA) was also calculated. RESULTS: Eighty-one infants with a median (range) gestational age of 28.7 (22.4-41.9) weeks were recruited. The dead space [median (IQR)] was higher in 35 infants with respiratory distress syndrome (RDS) [5.7 (5.1-7.0) ml/kg] and in 26 infants with bronchopulmonary dysplasia (BPD) [6.4 (5.1-7.5) ml/kg] than in 20 term controls with no respiratory disease [3.5 (2.8-4.2) ml/kg, p < 0.001]. Minute ventilation was higher in both infants with RDS or BPD compared to the controls. VA in infants with RDS or BPD was similar to that of the controls [p = 0.54]. CONCLUSION: Prematurely born infants with pulmonary disease have a higher dead space than term controls, which may influence the optimum level during volume-targeted ventilation. IMPACT: Measurement of the dead space was feasible in ventilated newborn infants. The physiological dead space was a significant proportion of the delivered volume in ventilated infants. The dead space (per kilogram) was higher in ventilated infants with respiratory distress syndrome or evolving bronchopulmonary dysplasia compared to term controls without respiratory disease. The dead space volume should be considered when calculating the most appropriate volume during volume-targeted ventilation.

Age and the distribution of major injury across a national trauma system.

BACKGROUND: Trauma places a significant burden on healthcare services, and its management impacts greatly on the injured patient. The demographic of major trauma is changing as the population ages, increasingly unveiling gaps in processes of managing older patients. Key to improving patient care is the ability to characterise current patient distribution. OBJECTIVES: There is no contemporary evidence available to characterise how age impacts on trauma patient distribution at a national level. Through an analysis of the Trauma Audit Research Network (TARN) database, we describe the nature of Major Trauma in England since the configuration of regional trauma networks, with focus on injury distribution, ultimate treating institution and any transfer in-between. METHODS: The TARN database was analysed for all patients presenting from April 2012 to the end of October 2017 in NHS England. RESULTS: About 307,307 patients were included, of which 63.8% presented directly to a non-specialist hospital (trauma unit (TU)). Fall from standing height in older patients, presenting and largely remaining in TUs, dominates the English trauma caseload. Contrary to perception, major trauma patients currently are being cared for in both specialist (major trauma centres (MTCs)) and non-specialist (TU) hospitals. Paediatric trauma accounts for <5% of trauma cases and is focussed on paediatric MTCs. CONCLUSIONS: Within adult major trauma patients in England, mechanism of injury is dominated by low level falls, particularly in older people. These patients are predominately cared for in TUs. This work illustrates the reality of current care pathways for major trauma patients in England in the recently configured regional trauma networks.

Effect of maturity and infection on the rate of relaxation of the respiratory muscles in ventilated, newborn infants.

AIM: To assess the respiratory muscle time constant of relaxation (τ), an index of respiratory muscle function in ventilated newborns. METHODS: Sixty-two infants (42 born prematurely) with a median gestational age of 29 [interquartile range (IQR) 26-37] weeks were prospectively studied. Measurement of τ was taken during spontaneous breathing on endotracheal continuous positive airway pressure prior to extubation, and τ was calculated from the reciprocal of the slope of the airway pressure decline versus time. Infants were classified as having had systemic or respiratory infection (positive microbiology) if they had any positive bacterial blood or respiratory culture prior to measurement. RESULTS: Measurement of τ was taken at a median post-natal age of 6 (IQR 3-29) days. The median τ was higher in premature infants [17.4 (IQR 7.7-28.3) sec/cmH2 O] compared to term infants [6.8 (IQR 4.4-8.7) sec/cmH2 O, p < 0.001]. The median τ was higher in infants who had had positive microbiology [17.6 (IQR 9.9-29.1) sec/cmH2 O] compared to infants with negative microbiology [8.0 (IQR 6.3-17.9) sec/cmH2 O, p = 0.034]. τ was related to gestational age (r = -0.265, p = 0.003) and weight at measurement (r = -0.269, p = 0.002). CONCLUSION: Respiratory muscle function in ventilated newborns is negatively affected by prematurity and previous systemic or respiratory infection.

Automatic oxygen control for reducing extremes of oxygen saturation: a randomised controlled trial.

OBJECTIVE: The objective of this study was to evaluate the efficacy of the automatic oxygen control (A-Fio2) in reducing the percentage of time spent in severe hypoxaemia (Spo2 <80%) in preterm infants for the time period on invasive ventilation and/or nasal continuous positive airway pressure (NCPAP) delivered by AVEA ventilator. DESIGN: A parallel arm randomised controlled trial. SETTING: A level-III neonatal intensive care unit. PATIENTS: Preterm infants (<33 weeks birth gestation) who received invasive ventilation or NCPAP in the first 72 hours of age. INTERVENTIONS: A-Fio2 vs manual (M-Fio2) oxygen control. OUTCOMES: The primary outcome of the study was percentage of time spent in severe hypoxaemia (Spo2 <80%). RESULTS: 44 infants were randomised to either A-Fio2 or M-Fio2 arm and continued in the study for the period of respiratory support (invasive ventilation and/or NCPAP). The total number of study days in A-Fio2 and M-Fio2 arm were 194 and 204 days, respectively. The percentage of time spent in Spo2 <80% was significantly lower with A-Fio2 compared with M-Fio2 (median of 0.1% (IQR: 0.07-0.7) vs 0.6% (0.2-2); p=0.03). The number of prolonged episodes (>60 s) of Spo2 <80% per day was also significantly lower in A-Fio2 (0.3 (0.0-2) vs 2 (0.6-6); p=0.02). CONCLUSION: A-Fio2 was associated with statistically significant reduction in the percentage of time spent in severe hypoxaemia when compared with M-Fio2 in preterm infants receiving respiratory support. TRIAL REGISTRATION NUMBER: NCT04223258.

Spontaneous bilateral distal ulna fracture: an unusual complication in a rheumatoid patient.

Bilateral ulna stress fractures are extremely rare. Patients with rheumatoid arthritis have osteopenic bone secondary to a variety of causes. We report a case of bilateral stress fractures of the ulna in an elderly patient with rheumatoid arthritis, and literature on this condition is reviewed. Prompt recognition and activity modification are essential to treat this rare injury. Recovery can take up to 12 weeks.

Research priorities for the management of complex fractures: a UK priority setting partnership with the James Lind Alliance.

OBJECTIVE: To determine research priorities for the management of complex fractures, which represent the shared priorities of patients, their families, carers and healthcare professionals. DESIGN/SETTING: A national (UK) research priority setting partnership. PARTICIPANTS: People who have experienced a complex fracture, their carers and relatives, and relevant healthcare professionals and clinical academics involved in treating patients with complex fractures. The scope includes open fractures, fractures to joints broken into multiple pieces, multiple concomitant fractures and fractures involving the pelvis and acetabulum. METHODS: A multiphase priority setting exercise was conducted in partnership with the James Lind Alliance over 21 months (October 2019 to June 2021). A national survey asked respondents to submit their research uncertainties which were then combined into several indicative questions. The existing evidence was searched to ensure that the questions had not already been sufficiently answered. A second national survey asked respondents to prioritise the research questions. A final shortlist of 18 questions was taken to a stakeholder workshop, where a consensus was reached on the top 10 priorities. RESULTS: A total of 532 uncertainties, submitted by 158 respondents (including 33 patients/carers) were received during the initial survey. These were refined into 58 unique indicative questions, of which all 58 were judged to be true uncertainties after review of the existing evidence. 136 people (including 56 patients/carers) responded to the interim prioritisation survey and 18 questions were taken to a final consensus workshop between patients, carers and healthcare professionals. At the final workshop, a consensus was reached for the ranking of the top 10 questions. CONCLUSIONS: The top 10 research priorities for complex fracture include questions regarding rehabilitation, complications, psychological support and return to life-roles. These shared priorities will now be used to guide funders and teams wishing to research complex fractures over the coming decade.

Volumetric capnography slopes in ventilated term and preterm infants.

OBJECTIVE: To assess whether the slopes of volumetric capnography differ in preterm compared to term-born ventilated newborn infants and whether they are related to gestational age and the duration of ventilation. APPROACH: The slopes of phase II (SII) and III (SIII) of volumetric capnographs were measured in ventilated term and preterm infants at King's College Hospital NHS Foundation Trust. The correlations of the slopes with gestational age (GA), duration of invasive ventilation and fraction of inspired oxygen (FIO2) were assessed. The slopes were normalised by multiplying the results with the expiratory tidal volume (VT) measurement. MAIN RESULTS: Fifty-six infants (44 preterm) were assessed. The preterm infants had a median (IQR) gestational age of 26 (25-29) weeks and were ventilated for 8 (3-32) days with a VT of 5.4 (4.1-6.8) ml kg-1. The term infants had a gestational age of 39 (37-40) weeks and were ventilated for 1 (1-6) day with a VT of 4.0 (3.6-5.3) ml kg-1. The SII (85.9 (76.2-98.4) mmHg) and SIII (16.5(10.0-21.9) mmHg) of the preterm infants were not significantly different compared to the SII (88.0 (74.6-110.0) mmHg) and SIII (13.5 (9.2-15.9) mmHg) of term infants (p = 0.625 and p = 0.144 respectively). SII was not significantly related to GA, duration of ventilation or FIO2. SIII was positively related to the duration of ventilation (r = 0.729, p < 0.001) and FIO2 (r = 0.704, p < 0.001). SIGNIFICANCE: The volumetric capnography phase III slope was steeper in infants with higher ventilatory requirements, hence could potentially be used as an index of disease severity in ventilated newborns.

Guideline developers in the United States were inconsistent in applying criteria for appropriate Grading of Recommendations, Assessment, Development and Evaluation use.

OBJECTIVES: We assessed whether guidelines published by organizations based in the United States comply with published criteria for the use of the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach. STUDY DESIGN AND SETTING: We performed a cross-sectional study of all clinical practice guidelines that indicated the use of the GRADE approach, were published between 2011 and 2018, and listed in the National Guidelines Clearinghouse. RESULTS: We included 67 guideline documents from 44 of 135 (32.6%) US-based organizations that indicated the use of the GRADE approach. The majority (60/67, 89.6%) of guidelines defined the certainty of evidence consistent with GRADE, but only approximately 1 in 10 (7/67, 10.4%) explicitly reported consideration of all eight criteria to assess the certainty in the evidence for rating down and up. A majority of guidelines (36/67, 53.7%) provided a summary of the evidence, described explicit consideration of all four central domains (36/67, 53.7%), and rated the strength of recommendation consistent with GRADE (36/67, 53.7%). CONCLUSION: Approximately one in three US-based organizations developing evidence-based guidelines report the use of GRADE, but adherence to published criteria is inconsistent. As uptake of the GRADE approach increases in the United States, continued efforts to train guideline methodologists and panel members are important.

GREIT: a unified approach to 2D linear EIT reconstruction of lung images.

Electrical impedance tomography (EIT) is an attractive method for clinically monitoring patients during mechanical ventilation, because it can provide a non-invasive continuous image of pulmonary impedance which indicates the distribution of ventilation. However, most clinical and physiological research in lung EIT is done using older and proprietary algorithms; this is an obstacle to interpretation of EIT images because the reconstructed images are not well characterized. To address this issue, we develop a consensus linear reconstruction algorithm for lung EIT, called GREIT (Graz consensus Reconstruction algorithm for EIT). This paper describes the unified approach to linear image reconstruction developed for GREIT. The framework for the linear reconstruction algorithm consists of (1) detailed finite element models of a representative adult and neonatal thorax, (2) consensus on the performance figures of merit for EIT image reconstruction and (3) a systematic approach to optimize a linear reconstruction matrix to desired performance measures. Consensus figures of merit, in order of importance, are (a) uniform amplitude response, (b) small and uniform position error, (c) small ringing artefacts, (d) uniform resolution, (e) limited shape deformation and (f) high resolution. Such figures of merit must be attained while maintaining small noise amplification and small sensitivity to electrode and boundary movement. This approach represents the consensus of a large and representative group of experts in EIT algorithm design and clinical applications for pulmonary monitoring. All software and data to implement and test the algorithm have been made available under an open source license which allows free research and commercial use.

Ventilation Efficiency and Respiratory Muscle Function at Different Levels of CPAP in Intubated Prematurely Born Infants.

BACKGROUND: CPAP improves respiratory function in prematurely born infants by establishing and maintaining functional residual capacity, but the level of CPAP that optimizes respiratory function has not been adequately described. We compared ventilation efficiency and respiratory muscle function at different levels of CPAP. METHODS: We studied spontaneously breathing, intubated convalescent premature infants at King's College Hospital NHS Foundation Trust and calculated the ventilation efficiency index and the respiratory muscle time constant of relaxation (τ) at the end of 3 consecutive 5-min periods at 4, 6, and 8 cm H2O of CPAP delivered in random order. RESULTS: Between February 2016 and August 2016, 38 infants with a median gestational age of 27 (interquartile range [IQR], 25-30) weeks and a median birthweight of 0.88 (IQR, 0.73-1.02) kg were studied. At a CPAP level of 6 cm H2O, the median ventilation efficiency index was higher (1.52 [IQR, 1.02-2.27]) and median τ was lower (15.6 [IQR, 10.1-21.3]) s/cm H2O] compared with the median ventilation efficiency index (0.75 [IQR, 0.56-1.03]) and median τ (23.3 [IQR, 15.4-35.2] sec/cm H2O) at CPAP of 4 cm H2O (P < .001 for both). At a CPAP level of 8 cm H2O, median ventilation efficiency index was significantly lower (1.27 [IQR, 1.04-1.91]) and median τ was not significantly different (11.2 [IQR, 8.3-18.9] s/cm H2O) compared with ventilation efficiency index and τ at CPAP of 6 cm H2O (P < .001 and P = .12, respectively). After multiple logistic regression, the level of CPAP was independently associated with the ventilation efficiency index (adjusted P < .001) and τ (adjusted P = .003). CONCLUSIONS: Increasing the level of CPAP from 4 to 6 cm H2O was associated with enhanced ventilation efficiency and respiratory muscle function in convalescent premature infants on ventilation, but there was no further benefit from increasing the pressure >6 cm H2O.

Physiological and anatomical dead space in mechanically ventilated newborn infants.

OBJECTIVES: To compare the anatomical (VD-Ana ) and alveolar dead space (VD-Alv ) in term and prematurely born infants and identify the clinical determinants of those indices. WORKING HYPOTHESIS: VD-Ana and VD-Alv will be higher in prematurely born compared to term born infants. STUDY DESIGN: Retrospective analysis of data collected at King's College Hospital NHS Foundation Trust, London, UK. PATIENT SELECTION: Fifty-six infants (11 term, 45 preterm) were studied at a median age of 8 (IQR 2-33) days. METHODOLOGY: VD-Ana was determined using Fowler's method of volumetric capnography. VD-Alv was determined by subtracting VD-Ana from the physiological dead space which was determined by the Bohr-Enghoff equation. VD-Ana and VD-Alv were related to body weight at the time of study. RESULTS: The median VD-Ana /kg was higher in prematurely born infants [3.7 (IQR: 3.0-4.5) mL/kg] compared to term infants [2.4 (IQR: 1.9-2.9) mL/kg, adjusted P = 0.001]. The median VD-Alv /kg was not higher in prematurely born infants [0.3 (IQR: 0.1-0.5)] compared to term infants [0.1 (IQR: 0.0-0.2) mL/kg] after adjusting for differences in respiratory rate and days of ventilation (P = 0.482). VD-Ana /kg was related to postmenstrual age (r = -0.388, P < 0.001), birth weight (r = -0.397, P < 0.001), and weight at measurement (r = -0.476, P < 0.001). VD-Alv /kg was related to postmenstrual age (r = -0.254, P < 0.001), birth weight (r = -0.291, P = 0.002), and weight at measurement (r = -0.281, P = 0.003) and related to days of ventilation (r = 0.194, P = 0.044). CONCLUSIONS: VD-Ana /kg and VD-Alv /kg increased with decreasing weight and gestation. VD-Alv was higher in infants that have undergone prolonged mechanical ventilation.

Refining metformin prescribing in New Zealand.

Metformin is the mainstay of treatment of type 2 diabetes. However, there has been significant concern on prescribing metformin in patients with renal impairment as a result of metformin-associated lactic acidosis (MALA). Recent studies have cast doubt on the existence of MALA purely related to metformin use. Medsafe recently initiated changes to datasheet so lower doses of metformin could be used in patients with GFR down to 15ml/min. In this paper we outline the context and implications of this change.

The PLISSIT Model: care and management of patients' psychosexual needs following radical surgery.

Patients who have undergone invasive medical procedures requiring radical body changes often experience feelings of worthlessness and particularly negative feelings about their sexuality. Their initial contact with the healthcare team is frequently a nurse who may be poorly equipped, too busy, or too embarrassed to help address the patients' sexual issues; therefore, vital information may be lost to the healthcare team. The PLISSIT Model offers nurses or case managers a concise framework for intervention to address patients' concerns at the earliest stages of their distress, and helps assure informed feedback to the healthcare team regarding the patients' sexual issues.

Ganglion cysts of the anterior cruciate ligament: a series of 15 cases.

PURPOSE: To increase awareness of the presence of ganglion cysts of the anterior cruciate ligament and to consider this diagnosis in any knee that has lost range of motion (ROM) in the absence of osteoarthritis. TYPE OF STUDY: Case series. METHODS: We present a series of 15 cases recorded over a period of 5 years illustrating the clinical presentation and additional pathology seen at arthroscopy. International Knee Documentation Committee scores were calculated at the recent follow-up to establish outcome of the surgery. RESULTS: The cysts occurred predominantly in men with the most common presenting complaint being decreased ROM and pain. Overall, results were excellent with no recurrence of symptoms at a mean 36-month follow-up, but outcome does appear to be associated with other pathology present. ROM was improved with arthroscopic excision of the cyst in all cases that were impaired. CONCLUSIONS: Although rare, ganglion cysts related to the cruciate ligaments of the knee should be considered in the differential diagnosis of a painful knee especially when associated with a decreased ROM and no evidence of osteoarthritis on radiographs. Other pathology can often be present, which may affect the overall outcome, but arthroscopic debridement of the ganglion cyst should be considered the treatment of choice in order to reliably restore active ROM. LEVEL OF EVIDENCE: Level IV, Case Series.

Reaction times to words vs symbols for both hands.

Reaction times were used to infer an interaction between different stimuli (verbal and symbolic) and the hand used to respond to such stimuli for 26 college students. Significant differences in reaction times were found dependent upon whether the stimulus was a word or a symbol and which hand was used in response to the different stimuli. There was more rapid mediation with significantly shorter latency for symbolic stimuli than for verbal stimuli for both the right and left hands. Also, latency was shorter for symbolic stimuli using the right hand than for verbal stimuli using the left hand. It may be concluded from this that efficacy of symbolic stimuli is primary in conveyance of denotative meaning. The primacy of symbolic stimuli for denoting meaning might be traced to evolutionary sources.

Pre-operative echocardiogram in hip fracture patients with cardiac murmur--an audit.

BACKGROUND: All hip fracture patients with a cardiac murmur have an echocardiogram as a part of their preoperative work-up in our unit. We performed a retrospective audit to assess the impact of obtaining a pre-operative echocardiogram on the management of hip fracture patients. METHODS: All hip fracture patients (N = 349) between 01/06/08 and 01/06/09 were included in the study. 29 patients had pre-operative echocardiogram (echo group). A computer generated randomised sample of 40 patients was generated from N, 'non-echo' group. Data was obtained from medical records and the Hospital Information Support System (HISS). The groups were compared using Student's t test. Approval was obtained locally from the clinical governance department for this project. RESULTS: Age and gender distribution were similar in both groups. Indication for echo was an acute cardiac abnormality in 4 cases. 25 patients had echo for no new cardiac problem (indication being cardiac murmur in 23 patients and extensive cardiac history in 2 cases). Cardiology opinion was sought in 5 cases. No patient required cardiac surgery or balloon angioplasty preoperatively. Patients having pre-operative echo had significant delay to surgery (average 2.7 days, range 0-6 days) compared to 'non-echo' group (average 1.1 days, range 0-3 days), (p < 0.001). There was no significant difference in length of stay (p = 0.14) and mortality at 30 days (p = 0.41) between the groups. CONCLUSION: We have developed departmental guidelines for expediting echo requests in hip fracture patients with cardiac murmur. A liaison has been established with our cardiology department to prioritise such patients on the Echocardiography waiting list, to prevent unnecessary avoidable delay. Careful patient selection for pre-operative echocardiography is important to avoid unnecessary delay to surgery.

Can regional resource shares be based only on prevalence data? An empirical investigation of the proportionality assumption.

The needs component of the current formulae for allocating resources for hospital services and prescribing in England is based on a utilisation approach. This assumes that expenditure on NHS activity in different geographical areas reflects relative needs and supply conditions, and that these can be disentangled by regression models to yield an estimate of relative need. These assumptions have been challenged on the grounds that the needs of some groups may be systematically 'unmet'. Critics have suggested an alternative based on variations in the prevalence of health conditions, called the 'epidemiological approach'. The epidemiological approach uses direct measures of morbidity to allocate health care resources. It divides the total national budget into disease programmes based on primary diagnosis, computes the proportion of total cases for each programme in each geographical area, and then allocates budgets to geographical areas proportional to their share of total cases. The main obstacle to the epidemiological approach has been seen as its very demanding data requirements. But it also faces methodological challenges. These centre on the assumption of proportionality which, at the area level to which resources will be allocated, requires that the average level of need for 'cases' within each disease programme is the same in every area. We illustrate the epidemiological approach, and test the proportionality assumption underpinning it, using data from the 2002-2004 rounds of the Health Survey for England. We find regional variation in disease severity for major diseases, which suggests that health care needs for some conditions vary by area. Further analysis suggests that the epidemiological approach might systematically underallocate resources to rural areas, areas with younger populations, and deprived areas. Since the proportionality assumption underpinning the epidemiological approach does not hold, its adoption would fail to take account of variations in severity. This casts some doubt on the utility of the approach for resource allocation at the present time.

The use of an articulating spacer in the management of infected total knee arthroplasties.

Eleven infected total knee arthroplasties underwent revision using an articulating spacer comprising a total condylar component and meniscal polyethylene insert cemented in place using antibiotic-loaded cement. Only 1 case required subsequent rerevision for infection, 2 were revised for pain, 6 remain in situ, and 2 patients have died with their spacers in situ. Average Knee Society clinical rating for the spacers left implanted is 167 at an average of 65 months. This articulating spacer appears not to require mandatory second-stage surgery, although should this prove necessary, then it is relatively straightforward to perform.