Marcus Kelm

Manual ventilation devices in neonatal resuscitation: Tidal volume and positive pressure-provision

BACKGROUND Excessive peak inspiratory pressures (PIP) and high tidal volumes (Vt) during manual ventilation can be detrimental to the neonatal lung. We compared the influence of different manual ventilation devices and individual professional experience on the extent of applied Vt and PIP in simulated neonatal resuscitation. MATERIAL AND METHODS One hundred and twenty medical professionals were studied. An intubated mannequin (equivalent to 1.0 kg neonate) was ventilated using two different devices: a self-inflating bag and a T-piece resuscitator. Target value was a PIP of 20 cm H(2)O. Applied PIP and the resulting Vt were recorded continuously using a respiratory function monitor (CO(2)SMO(+), Novametrix, USA). RESULTS Vt and PIP provision was significantly higher in SI-bags, compared to T-piece devices: median (interquartile range) PIP 25.6 (18.2) cm H(2)O vs 19.7 (3.2) cm H(2)O (p<0.0005), and Vt 5.1(3.2) ml vs Vt 3.6 (0.8) ml (p<0.0005) respectively. The intersubject variability of Vt and PIP provision was distinctly higher in SI-bags, compared to T-piece devices. Professional experience had no significant impact on the level and the variability of Vt or PIP provided. CONCLUSION Use of T-piece devices guarantees reliable and constant Vt and PIP provision, irrespective of individual, operator dependent variables. Methods to measure and to avoid excessive tidal volumes in neonatal resuscitation need to be developed.

Reliability of two common PEEP-generating devices used in neonatal resuscitation.

BACKGROUND Approximately 15% of neonates require respiratory support at birth, the demand of which increases with decreasing gestational age. Positive end-expiratory pressure (PEEP) stabilizes the airways and improves both pulmonary functional residual capacity and compliance. Self-inflating bags, which can be used with and without a PEEP-valve, are most commonly used for neonatal resuscitation, pressure limited T-piece resuscitators are becoming increasingly popular. The aim of the study was to investigate the reliability of PEEP provision of both systems. MATERIAL AND METHODS An intubated, leak free mannequin (equivalent to 1 kg neonate, pulmonary compliance 0.2 ml*cmH (2)O (-1)) was used for testing both devices. Eleven PEEP-valves attached to a 240 ml self-inflating bag and 5 T-piece resuscitators were investigated. Provision of a PEEP of 5 cmH (2)O (gas flow of 8l/min) at manual ventilation at breaths 40/min was investigated. Data were recorded using a standard pneumotachograph. RESULTS Only 1/11 PEEP-valves provided a PEEP of 5 cmH (2)O (mean (SD) 2.95 (1.82) cmH (2)O, CV 0.62%), in 5/11 (45%) PEEP was <3 cmH (2)O, in 2 of the PEEP-valves produced a PEEP below 0.3 cmH (2)O. All T-piece resuscitators provided a PEEP >5 cmH (2)O (mean 5.59 (0.32) cmH (2)O, CV 0.06%). Significant differences in individual performance per device (p<0.05) and between systems (p=0.007) were found. CONCLUSION Self-inflating bags did not reliably provide the desired PEEP of 5 cmH (2)O, whereas T-piece resuscitators did reliably provide the set PEEP-level, with less variability. When using self-inflating bags with PEEP-valves, neonatologists should check the equipment regarding the reliability of PEEP provision.

Equipment and Operator Training Denote Manual Ventilation Performance in Neonatal Resuscitation

High peak inspiratory pressure (PIP) and tidal volume (V(T)) from manual ventilation are hazardous to the neonatal lung. We investigated the influence of operator training on the extent of applied PIP and V(T) between two manual ventilation devices. We performed a prospective, crossover study of 84 medical professionals using a neonatal mannequin. Participants were classified into four groups, according to experience in neonatal resuscitation and previous training in manual ventilation. Provision of PIP, V(T), and inspiratory time (Ti) were compared between groups and equipment used, either a self-inflating bag (SI-bag) or a T-piece resuscitator (Neopuff). Using SI-bags, operator training significantly affected provision of PIP ( P < 0.001), V(T) ( P < 0.001), and Ti ( P = 0.048). Using a T-piece device, PIP and V(T) provision was independent of operator training ( P = 0.55 and P = 0.66, respectively). Twenty-five participants (30%) had previous experience with T-piece devices; this correlated significantly with lower PIP and lower V(T) provision ( P > 0.001 for PIP and V(T)). Operator training level and device-specific experience had a significant impact on PIP and V(T) provision when using SI-bags for manual ventilation. For operators with no specific training in manual ventilation, use of T-piece devices is advised to control for excessive PIP and V(T) application.

Manual neonatal ventilation training: a respiratory function monitor helps to reduce peak inspiratory pressures and tidal volumes during resuscitation

Abstract Background: Neonatal resuscitation training is considered to be multifarious and includes manual ventilation as an essential competence for any health-care provider. Usually, ventilation is applied with self-inflating bags (SIBs). These devices have been shown to produce highly variable, operator-dependent peak inspiratory pressures (PIPs) and tidal volumes (VT). Excessive PIP and VT contribute to lung injury. We studied a simple tool to improve resuscitation skills. Objective: The objectives of this study were to train health-care providers to avoid excessive PIP and VT by visualizing these values by using a respiratory function monitor (RFM) and to study the sustainability of such a training. Material and methods: Previously untrained medical professionals were educated and trained to ventilate a neonatal preterm manikin. PIP and VT were measured with an RFM. Graphical representations of the measurements were displayed during training, but the RFM was blinded during subsequent recordings. Participants were reassessed directly after training and 1 month later. Results: In total, 37 participants were trained and assessed three times during the study. Median PIPs (range) were 32.3 (4.1–44) cm H2O before training, 17.8 (9.6–23.6) cm H2O directly after training (P<0.05), and 18.7 (7.5–41.6) cm H2O 1 month later, and the values remained low, compared with before training (P<0.05). Median VTs were 6.7 (4.2–44) mL before training, 3.5 (1.8–7.3) mL directly after training (P<0.05), and 4.1 (1.9–9.7 mL) 1 month after training (P<0.05). Conclusion: Using a SIB, untrained staff produced excessive PIP and VT. Training with a simple RFM significantly reduced the occurrence of excessive PIP and VT. The effect was sustained for at least 1 month.

Balloon Dilatation and Stenting for Aortic Coarctation A Systematic Review and Meta-Analysis

Background—There is no systematic assessment of available evidence on effectiveness and comparative effectiveness of balloon dilatation and stenting for aortic coarctation. Methods and Results—We systematically searched 4 online databases to identify and select relevant studies of balloon dilatation and stenting for aortic coarctation based on a priori criteria (PROSPERO 2014:CRD42014014418). We quantitatively synthesized results for each intervention from single-arm studies and obtained pooled estimates for relative effectiveness from pairwise and network meta-analysis of comparative studies. Our primary analysis included 15 stenting (423 participants) and 12 balloon dilatation studies (361 participants), including patients ≥10 years of age. Post-treatment blood pressure gradient reduction to ⩽20 and ⩽10 mm Hg was achieved in 89.5% (95% confidence interval, 83.7–95.3) and 66.5% (44.1–88.9%) of patients undergoing balloon dilatation, and in 99.5% (97.5–100.0%) and 93.8% (88.5–99.1%) of patients undergoing stenting, respectively. Odds of achieving ⩽20 mm Hg were lower with balloon dilatation as compared with stenting (odds ratio, 0.105 [0.010–0.886]). Thirty-day survival rates were comparable. Numerically more patients undergoing balloon dilatation experienced severe complications during admission (6.4% [2.6–10.2%]) compared with stenting (2.6% [0.5–4.7%]). This was supported by meta-analysis of head-to-head studies (odds ratio, 9.617 [2.654–34.845]) and network meta-analysis (odds ratio, 16.23, 95% credible interval: 4.27–62.77) in a secondary analysis in patients ≥1 month of age, including 57 stenting (3397 participants) and 62 balloon dilatation studies (4331 participants). Conclusions—Despite the limitations of the evidence base consisting predominantly of single-arm studies, our review indicates that stenting achieves superior immediate relief of a relevant pressure gradient compared with balloon dilatation.

Hemodynamic Evaluation of a Biological and Mechanical Aortic Valve Prosthesis Using Patient-Specific MRI-Based CFD: MRI-BASED CFD COMPARISON OF TWO AORTIC VALVE PROSTHESES

Modeling different treatment options before a procedure is performed is a promising approach for surgical decision making and patient care in heart valve disease. This study investigated the hemodynamic impact of different prostheses through patient-specific MRI-based CFD simulations. Ten time-resolved MRI data sets with and without velocity encoding were obtained to reconstruct the aorta and set hemodynamic boundary conditions for simulations. Aortic hemodynamics after virtual valve replacement with a biological and mechanical valve prosthesis were investigated. Wall shear stress (WSS), secondary flow degree (SFD), transvalvular pressure drop (TPD), turbulent kinetic energy (TKE), and normalized flow displacement (NFD) were evaluated to characterize valve-induced hemodynamics. The biological prostheses induced significantly higher WSS (medians: 9.3 vs. 8.6 Pa, P = 0.027) and SFD (means: 0.78 vs. 0.49, P = 0.002) in the ascending aorta, TPD (medians: 11.4 vs. 2.7 mm Hg, P = 0.002), TKE (means: 400 vs. 283 cm2 /s2 , P = 0.037), and NFD (means: 0.0994 vs. 0.0607, P = 0.020) than the mechanical prostheses. The differences between the prosthesis types showed great inter-patient variability, however. Given this variability, a patient-specific evaluation is warranted. In conclusion, MRI-based CFD offers an opportunity to assess the interactions between prosthesis and patient-specific boundary conditions, which may help in optimizing surgical decision making and providing additional guidance to clinicians.

Impact of patient-specific LVOT inflow profiles on aortic valve prosthesis and ascending aorta hemodynamics

Abstract Patient-specific models become increasingly important in cardiovascular research as they allow prediction of surgical procedures. While the left ventricular outflow profile is an essential boundary condition, it remains unknown before treatment takes place. To overcome this problem, hemodynamics after virtual valve replacement were calculated based on different inlet profiles at the left ventricular outflow tract: a generic plug profile and a profile derived from 4D-flow-MRI. Spatially averaged parameters within the aorta were not significantly altered using either profile. A generic profile might be sufficient for the prediction of hemodynamics, circumventing the problem of predicting change in patient-specific boundary conditions.

Model-Based Therapy Planning Allows Prediction of Haemodynamic Outcome after Aortic Valve Replacement

Optimizing treatment planning is essential for advances in patient care and outcomes. Precisely tailored therapy for each patient remains a yearned-for goal. Cardiovascular modelling has the potential to simulate and predict the functional response before the actual intervention is performed. The objective of this study was to proof the validity of model-based prediction of haemodynamic outcome after aortic valve replacement. In a prospective study design virtual (model-based) treatment of the valve and the surrounding vasculature were performed alongside the actual surgical procedure (control group). The resulting predictions of anatomic and haemodynamic outcome based on information from magnetic resonance imaging before the procedure were compared to post-operative imaging assessment of the surgical control group in ten patients. Predicted vs. post-operative peak velocities across the valve were comparable (2.97 ± 1.12 vs. 2.68 ± 0.67 m/s; p = 0.362). In wall shear stress (17.3 ± 12.3 Pa vs. 16.7 ± 16.84 Pa; p = 0.803) and secondary flow degree (0.44 ± 0.32 vs. 0.49 ± 0.23; p = 0.277) significant linear correlations (p < 0.001) were found between predicted and post-operative outcomes. Between groups blood flow patterns showed good agreement (helicity p = 0.852, vorticity p = 0.185, eccentricity p = 0.333). Model-based therapy planning is able to accurately predict post-operative haemodynamics after aortic valve replacement. These validated virtual treatment procedures open up promising opportunities for individually targeted interventions.

Beyond Pressure Gradients: The Effects of Intervention on Heart Power in Aortic Coarctation

Background In aortic coarctation, current guidelines recommend reducing pressure gradients that exceed given thresholds. From a physiological standpoint this should ideally improve the energy expenditure of the heart and thus prevent long term organ damage. Objectives The aim was to assess the effects of interventional treatment on external and internal heart power (EHP, IHP) in patients with aortic coarctation and to explore the correlation of these parameters to pressure gradients obtained from heart catheterization. Methods In a collective of 52 patients with aortic coarctation 25 patients received stenting and/or balloon angioplasty, and 20 patients underwent MRI before and after an interventional treatment procedure. EHP and IHP were computed based on catheterization and MRI measurements. Along with the power efficiency these were combined in a cardiac energy profile. Results By intervention, the catheter gradient was significantly reduced from 21.8±9.4 to 6.2±6.1mmHg (p<0.001). IHP was significantly reduced after intervention, from 8.03±5.2 to 4.37±2.13W (p < 0.001). EHP was 1.1±0.3 W before and 1.0±0.3W after intervention, p = 0.044. In patients initially presenting with IHP above 5W intervention resulted in a significant reduction in IHP from 10.99±4.74 W to 4.94±2.45W (p<0.001), and a subsequent increase in power efficiency from 14 to 26% (p = 0.005). No significant changes in IHP, EHP or power efficiency were observed in patients initially presenting with IHP < 5W. Conclusion It was demonstrated that interventional treatment of coarctation resulted in a decrease in IHP. Pressure gradients, as the most widespread clinical parameters in coarctation, did not show any correlation to changes in EHP or IHP. This raises the question of whether they should be the main focus in coarctation interventions. Only patients with high IHP of above 5W showed improvement in IHP and power efficiency after the treatment procedure. Trial Registration clinicaltrials.gov NCT02591940

MRI as a tool for non-invasive vascular profiling: a pilot study in patients with aortic coarctation

Aim: While the overall concept of aortic coarctation has changed from one of simple obstruction to one that includes significant vascular dysfunction, this has not yet been translated into the diagnostic and treatment process. To close this gap, we sought to demonstrate the usefulness of an additional non-invasive vascular profile. Method: During a pilot study in eight coarctation patients, aortic area compliance, aortic distensibility, time phase shift and blood flow (distribution) were calculated from cine-MRI and 2D-/4D-velocity-encoded MRI sequences. Results: Compared to healthy individuals, a significantly lower aortic compliance and reduced flow to the descending aorta were found in patients with coarctation. Discussion: These differences underline the potential usefulness of a combined vascular profile in coarctation patients. Conclusion: It was successfully shown that functional vascular profiling of the aorta is feasible to be acquired non-invasively in a clinical setting and can provide additional diagnostic information. These can be the key input parameters for computational fluid dynamics-modeling.