Evaluating the influence of ventilation and ventilation-compression synchronization on chest compression force and depth during simulated neonatal resuscitation.

OBJECTIVES: To investigate the influence of ventilation and ventilation-compression synchronization on compression force and sternal displacement during simulated neonatal cardiopulmonary resuscitation (NCPR) on an infant manikin. METHODS: Five Neonatal Resuscitation Program trained clinicians were recruited to perform simulated NCPR on an infant manikin using two-finger (TF) and two-thumb (TT) compression, with synchronous and asynchronous ventilation, as well as without ventilation. The sternal displacement and force were recorded and analyzed. RESULTS: Synchronous ventilation and compression yielded sternal displacements and forces in the range of 22.8-32.4 mm and 15.0-29.8 N, respectively, while asynchronous ventilation and compression produced depths and forces in the range of 21.2-32.4 mm and 14.0-28.8 N, respectively. CONCLUSIONS: Ventilation exerts a significant influence on sternal displacement and force during simulated NCPR, regardless of the compression method used. Ventilation-compression synchronization, however, is only significant during TF compression with lower compression forces measured during synchronous ventilation than in asynchronous ventilation. This occurs for two reasons: (i) the strong influence of ventilation forces on the lower magnitude compression forces produced during TF compression relative to TT compression and (ii) in asynchronous ventilation, compression and ventilation may occur simultaneously, with inflation and deflation providing an opposing force to the applied compression force.

Development of a real-time feedback algorithm for chest compression during CPR without assuming full chest decompression.

OBJECTIVES: To evaluate the performance of a real-time feedback algorithm for chest compression (CC) during cardiopulmonary resuscitation (CPR), which provides accurate estimation of the CC depth based on dual accelerometer signal processing, without assuming full CDC. Also, to explore the influence of incomplete chest decompression (CDC) on the CC depth estimation performance. METHODS: The performance of a real-time feedback algorithm for CC during CPR was evaluated by comparison with an offline algorithm using adult CPR manikin CC data obtained under various conditions. RESULTS: The real-time algorithm, using non-causal baselining, delivered comparable CC depth estimation accuracy to the offline algorithm on both soft and hard back support surfaces. In addition, for both algorithms incomplete CDC led to underestimation of the CC depth. CONCLUSIONS: CPR feedback systems which utilize an assumption of full CDC may be unreliable especially in long duration CPR events where rescuer fatigue can strongly influence CC quality. In addition, these systems may increase the risk of thoracic and abdominal injury during CPR since rescuers may apply excessive compression forces due to underestimation of the CC depth when incomplete CDC occurs. Hence, there is a strong need for CPR feedback systems to accurately measure CDC in order to improve their clinical effectiveness.

A scoping review of important urinary catheter induced complications.

This study presents a scoping review of the literature on the morbidity and mortality associated with several common complications of urinary catheterization. Data gathered from the open literature were analyzed graphically to gain insights into the most important urinary catheter induced complications. The results reveal that the most significant catheter complications are severe mechanical trauma (perforation, partial urethral damage and urinary leakage), symptomatic bacterial infection, and anaphylaxis, catheter toxicity and hypersensitivity. The data analysis also revealed that the complications with the highest morbidity are all closely related to the mechanical interaction of the catheter with the urethra. This suggests that there is a strong need for urinary catheter design to be improved to minimize mechanical interaction, especially mechanical damage to the urinary tract, and to enhance patient comfort. Several urinary catheter design directions have been proposed based on tribological principles. Among the key recommendations is that catheter manufacturers develop catheter coatings which are both hydrophilic and antibacterial, and which maintain their antibacterial patency for at least 90 days.

A modeling approach to the effects of force guided versus depth guided compression during cardiopulmonary resuscitation on different chests and back support surfaces.

OBJECTIVES: To validate an existing theoretical model for the mechanics of chest compression (CC) during constant peak force cardiopulmonary resuscitation (CPR) using experimental human and manikin CC data from the literature. Also, to gain insights into the clinical application of force guided CPR. METHODS: The experimental CC data from the literature were analyzed and compared to theoretical predictions from the constant peak force CPR model. The CPR model was also used to explore how CC rate and peak sternal force may influence CC performance during the clinical application of force guided CPR. RESULTS: The model predictions matched the human CC data to within an average difference of less than 1.5% at CC rates of 60 cpm and 90 cpm, and 0.6% for the manikin data at a CC rate of 90 cpm. The model predictions also showed that the net sternum-to-spine compression depth achieved during force guided CPR strongly depends on the patient's thoracic stiffness. CONCLUSIONS: Good quantitative agreement between the experimental data from the literature and the theoretical model suggests that the constant peak force CPR model developed by Boe and Babbs provides reasonable prediction of CC mechanics during CPR over a range of clinically relevant CC rates. The model predictions also suggest that the effectiveness of CC during force guided CPR is highly sensitive to the patient's thoracic stiffness and insensitive to the back support stiffness. Patients having high thoracic stiffness (≥ 100 Ncm(-1)) were found to require higher CC forces, which may exceed the force above which severe chest wall trauma and abdominal injury occurs, in order to achieve the ERC recommended CC depth range. This suggests that the choice of maximum sternal force applied by clinicians during constant peak force CPR ought to be based on a general assessment of the patient's thoracic stiffness.

The impact of backboard size and orientation on sternum-to-spine compression depth and compression stiffness in a manikin study of CPR using two mattress types.

OBJECTIVES: To explore how backboard orientation and size impact chest compressions during cardiopulmonary resuscitation (CPR). METHODS: Experiments were conducted on a full-body CPR training manikin using a custom-built simulator. Two backboards of different sizes were tested in longitudinal (head to toe) and latitudinal (side to side) directions to assess the impact of size and orientation on chest compressions during CPR. The net sternum-to-spine displacement, combined mattress and sternal displacement as well as the axial reaction force were measured during each test. RESULTS: The difference in net compression depth between the larger and smaller backboards ranged between 0.08±0.30 cm and 1.47±0.13 cm, while the difference in back support stiffness varied between 103.7±211 N/cm and 688.1±180.3 N/cm. The difference in net compression depth between the longitudinal and latitudinal backboard orientations ranged from 0.07±0.32 cm to 0.34±0.18 cm, while for the back support stiffness the difference was between 13.4±50.0 N/cm and 592.2±211.0 N/cm. CONCLUSIONS: The effect of backboard size on chest compression (CC) performance during CPR was found to be significant with the larger backboard producing deeper chest compressions and higher back support stiffness than the smaller backboard. The impact of backboard orientation was found to depend on the size of the backboard and type of mattress used. Clinicians should be aware that although a smaller backboard may be easier for rescuers to manipulate, it does not provide as effective back support or produce as deep chest compressions as a larger backboard.

Application of finite element analysis to the design of tissue leaflets for a percutaneous aortic valve.

Percutaneous Aortic Valve (PAV) replacement is an attractive alternative to open heart surgery, especially for patients considered to be poor surgical candidates. Despite this, PAV replacement still has its limitations and associated risks. Bioprosthetic heart valves still have poor long-term durability due to calcification and mechanical failure. In addition, the implantation procedure often presents novel challenges, including damage to the expandable stents and bioprosthetic leaflets. In this study, a simplified version of Fung's elastic constitutive model for skin, developed by Sun and Sacks, was implemented using finite element analysis (FEA) and applied to the modelling of bovine and kangaroo pericardium. The FEA implementation was validated by simulating biaxial tests and by comparing the results with experimental data. Concepts for different PAV geometries were developed by incorporating valve design and performance parameters, along with stent constraints. The influence of effects such as different leaflet material, material orientation and abnormal valve dilation on the valve function was investigated. The stress distribution across the valve leaflet was also examined to determine the appropriate fibre direction for the leaflet. The simulated attachment forces were compared with suture tearing tests performed on the pericardium to evaluate suture density. It is concluded that kangaroo pericardium is suitable for PAV applications, and superior to bovine pericardium, due to its lower thickness and greater extensibility.