Can infant CPR performance be improved through the provision of 'real time' feedback?

Cardiac arrest (CA) is a significant health issue Worldwide. Paediatric sufferers have particu-larly poor outcomes, with high-rates of associated mortality and morbidity. Early cardiopulmonary-resuscitation (CPR), an emergency procedure which combines external chest-compressions with artificial-ventilations (rescue breaths), has been shown to improve CA outcomes. Researchers have, however, demonstrated CPR, even when delivered by highly-trained-rescuers is not currently being performed optimally. International guidelines have suggested the potential contribution of feedback systems (assistance), in improving the delivery of chest-compressions and rescue breaths to improve survival rates. Thus, the main focus of this research was to design and develop a real-time CPR-performance-feedback-system, to monitor and assist rescuers in producing high-quality infant-CPR (iCPR). This was conducted as follows: assessment of current compressions by Basic Life Support (BLS) and ‘lay’ rescuers, design and development of a real-time feedback and performance system and the study of its effects during iCPR. All performances were compared against benchmarked quality standards. During unassisted iCPR, BLS and ‘lay’ rescuer overall compression quality, that is those con-comitantly achieving all four iCPR quality targets, was 61.4% and >24.6%, respectively. Assistance delivered more breaths, 5-32%, more quickly, 30-84%, complying with recommendations. As-sisted compression count, after each ventilation, was 53% less than unassisted, complying with recommendations. There were no differences in the guideline compression duty cycle (DC), provided that compression time and peak depth were the same. Thesis summary iv Unassisted compressions failed to show compliance with quality targets. Assistance produced significant improvements in the overall quality of compressions, reduced the time for breaths and regulated the compression counts after each ventilation. However, lay rescuers require additional training with the feedback system and iCPR simulation. Overall the real-time feed-back system significantly improved iCPR performance, such that it could now be trialled to investigate possible improvements in clinical outcomes

Can real-time feedback improve the simulated infant cardiopulmonary resuscitation performance of basic life support and lay rescuers?

Background Performing high-quality chest compressions during cardiopulmonary resuscitation (CPR) requires achieving of a target depth, release force, rate and duty cycle. Objective This study evaluates whether ‘real time’ feedback could improve infant CPR performance in basic life support-trained (BLS) and lay rescuers. It also investigates whether delivering rescue breaths hinders performing high-quality chest compressions. Also, this study reports raw data from the two methods used to calculate duty cycle performance. Methodology BLS (n=28) and lay (n=38) rescuers were randomly allocated to respective ‘feedback’ or ‘no-feedback’ groups, to perform two-thumb chest compressions on an instrumented infant manikin. Chest compression performance was then investigated across three compression algorithms (compression only; five rescue breaths then compression only; five rescue breaths then 15:2 compressions). Two different routes to calculate duty cycle were also investigated, due to conflicting instruction in the literature. Results No-feedback BLS and lay groups demonstrated 60% and >25% of all chest compressions, across all three algorithms. Performing rescue breaths did not impede chest compression quality. Conclusions A feedback system has great potential to improve infant CPR performance, especially in cohorts that have an underlying understanding of the technique. The addition of rescue breaths—a potential distraction—did not negatively influence chest compression quality. Duty cycle performance depended on the calculation method, meaning there is an urgent requirement to agree a single measure

Development of a novel indentation device suitable for arthroscopic evaluation of articular cartilage

Background: The size of lesions on articular cartilage are difficult to estimate using conventional preoperative imaging techniques, which may prevent the use of conservative procedures in the restoration of joint function following osteoarthritis (OA). Arthroscopic probes have been designed to be used intraopertively which can assess the mechanical integrity of the cartilage surface. These devices may not have the sensitivity to detect early OA. Therefore, there exists the need for a low load indentation system which can determine both static and time-dependent properties of the tissue and thereby improve the likelihood of early OA detection. Such a probe also has the potential for mounting on a robotic arm for precise excision of tissue. In order to determine the early signs of OA, it is important to characterise the repeatability, variation and mechanical response of the articular cartilage surface to being indented with respect to different experimental parameters. Objective: To design, build and evaluate a bench top indentation system to assess the viscoelastic properties of articular cartilage, which has the potential to be converted to a device that could be used arthroscopically and intraopertively. In particular, it was the aim to: - investigate the difference between a spherically headed indenter and a flat headed indenter in assessing the cartilage mechanical properties in vitro; - evaluate articular cartilage's preconditioning properties by cyclic indentation testing; - and to evaluate the recovery of articular cartilage subsequent to the preconditioning. Methods: A bench top materials testing device was designed and built using a high resolution linear actuator and a spring-loaded Linear Variable Differential Transducer (LVDT). The actuator drove the tip of the LVDT, with either a flat or spherical tip, into the cartilage surface and the spring of the LVDT provided a known force and displacement. The surface deformation of the cartilage could then be determined from such a device. Healthy osteochondral plugs were harvested from the bovine tibial plateau articulating surface using an osteochondral coring tool. Plugs were mounted in plaster of paris with the cartilage surface normal to the indenter. All test procedures were identical: an actuator displacement of 5mm, a ramp speed of 5mm/second and a holding time of 30 seconds. An initial experiment was performed on a metal plug to ensure that any recorded deformation was that of the cartilage surface and not of the underlying environment. Subsequently the indentation mechanics of two indenter tips was evaluated: a spherical head indenter of diameter 4.8 mm and a flat ended indenter with a diameter of 5.1 mm. Then the cartilage preconditioning properties were evaluated using the flat-ended indenter. Each plug was tested 10 times in exactly the same place on the cartilage surface with a time interval of 20 seconds between each test. Finally, to test how long the cartilage takes to recover from its preconditioned state, each plug was indented 5 times in exactly the same place on the cartilage surface with a time interval of 20 seconds between each test and a further 6th indentation was also done in the same place on the cartilage surface but after either 1, 5, 10, 20 or 30 minutes interval. This 6th result was compared to the initial indentation. If the properties determined from the 6th indentation were the same as those of the first indentation, one could say that the sample had recovered. Results: Indenting the metal plug did not result in any measurable deformation indicating that subsequent measures are that of the cartilage surface and not of any underlying structures. When indenting with the spherical head indenter the deformation was deeper and quicker than using the flat-ended indenter due to the small contact region on the cartilage surface which means that there was higher stress on the surface compared with the flat-ended indenter. The preconditioning experiment indicated that the indentation depth decreased with each cycle of loading until approximately the 5th cycle after which the cartilage may be assumed to be preconditioned, since successive indentations exhibited similar mechanical behaviour. The time constant describing the surface deformation with time did not undergo any preconditioning which means that only the stiffness is affected by preconditioning, not permeability. Thirty minutes of recovery was sufficient for the surface to fully recover to its original state. Conclusions: A bench top device has been designed and manufactured that can assess the mechanical characteristics of articular cartilage. Furthermore, this device has demonstrated mechanical differences in the surface response between indenter geometries and the preconditioning and recovery characteristics of cartilage. Suggestions and comments have been made regarding the next phase of this research into the development an arthroscopic indentation device.Background: The size of lesions on articular cartilage are difficult to estimate using conventional preoperative imaging techniques, which may prevent the use of conservative procedures in the restoration of joint function following osteoarthritis (OA). Arthroscopic probes have been designed to be used intraopertively which can assess the mechanical integrity of the cartilage surface. These devices may not have the sensitivity to detect early OA. Therefore, there exists the need for a low load indentation system which can determine both static and time-dependent properties of the tissue and thereby improve the likelihood of early OA detection. Such a probe also has the potential for mounting on a robotic arm for precise excision of tissue. In order to determine the early signs of OA, it is important to characterise the repeatability, variation and mechanical response of the articular cartilage surface to being indented with respect to different experimental parameters. Objective: To design, build and evaluate a bench top indentation system to assess the viscoelastic properties of articular cartilage, which has the potential to be converted to a device that could be used arthroscopically and intraopertively. In particular, it was the aim to: - investigate the difference between a spherically headed indenter and a flat headed indenter in assessing the cartilage mechanical properties in vitro; - evaluate articular cartilage's preconditioning properties by cyclic indentation testing; - and to evaluate the recovery of articular cartilage subsequent to the preconditioning. Methods: A bench top materials testing device was designed and built using a high resolution linear actuator and a spring-loaded Linear Variable Differential Transducer (LVDT). The actuator drove the tip of the LVDT, with either a flat or spherical tip, into the cartilage surface and the spring of the LVDT provided a known force and displacement. The surface deformation of the cartilage could then be determined from such a device. Healthy osteochondral plugs were harvested from the bovine tibial plateau articulating surface using an osteochondral coring tool. Plugs were mounted in plaster of paris with the cartilage surface normal to the indenter. All test procedures were identical: an actuator displacement of 5mm, a ramp speed of 5mm/second and a holding time of 30 seconds. An initial experiment was performed on a metal plug to ensure that any recorded deformation was that of the cartilage surface and not of the underlying environment. Subsequently the indentation mechanics of two indenter tips was evaluated: a spherical head indenter of diameter 4.8 mm and a flat ended indenter with a diameter of 5.1 mm. Then the cartilage preconditioning properties were evaluated using the flat-ended indenter. Each plug was tested 10 times in exactly the same place on the cartilage surface with a time interval of 20 seconds between each test. Finally, to test how long the cartilage takes to recover from its preconditioned state, each plug was indented 5 times in exactly the same place on the cartilage surface with a time interval of 20 seconds between each test and a further 6th indentation was also done in the same place on the cartilage surface but after either 1, 5, 10, 20 or 30 minutes interval. This 6th result was compared to the initial indentation. If the properties determined from the 6th indentation were the same as those of the first indentation, one could say that the sample had recovered. Results: Indenting the metal plug did not result in any measurable deformation indicating that subsequent measures are that of the cartilage surface and not of any underlying structures. When indenting with the spherical head indenter the deformation was deeper and quicker than using the flat-ended indenter due to the small contact region on the cartilage surface which means that there was higher stress on the surface compared with the flat-ended indenter. The preconditioning experiment indicated that the indentation depth decreased with each cycle of loading until approximately the 5th cycle after which the cartilage may be assumed to be preconditioned, since successive indentations exhibited similar mechanical behaviour. The time constant describing the surface deformation with time did not undergo any preconditioning which means that only the stiffness is affected by preconditioning, not permeability. Thirty minutes of recovery was sufficient for the surface to fully recover to its original state. Conclusions: A bench top device has been designed and manufactured that can assess the mechanical characteristics of articular cartilage. Furthermore, this device has demonstrated mechanical differences in the surface response between indenter geometries and the preconditioning and recovery characteristics of cartilage. Suggestions and comments have been made regarding the next phase of this research into the development an arthroscopic indentation device