Thomas Drevhammar

Comparison of seven infant continuous positive airway pressure systems using simulated neonatal breathing.

Objective: Continuous positive airway pressure is an established treatment for respiratory distress in neonates. Continuous positive airway pressure has been applied to infants using an array of devices. The aim of this experimental study was to investigate the characteristics of seven continuous positive airway pressure systems using simulated breath profiles from newborns. Design: Experimental in vitro study. Setting: Research laboratory in Sweden. Intervention: None. Measurements and Main Results: In vitro simulation of spontaneous neonatal breathing was achieved with a mechanical lung model. Simulation included two breath profiles, three levels of continuous positive airway pressure with and without short binasal prongs and different levels of constant leak. Pressure stability and imposed work of breathing were determined. Seven continuous positive airway pressure systems were tested. There were large differences in pressure stability and imposed work of breathing between tested continuous positive airway pressure systems. Neopuff and Medijet had the highest pressure instability and imposed work of breathing. Benveniste, Hamilton Universal (Arabella), and Bubble continuous positive airway pressure showed intermediate results. AirLife and Infant Flow had the lowest pressure instability and imposed work of breathing. AirLife and Infant Flow showed the least decrease in delivered pressure when challenged with constant leak. Conclusion: The seven tested continuous positive airway pressure systems showed large variations in pressure stability and imposed work of breathing. They also showed large differences in how well they maintain continuous positive airway pressure when exposed to leak. For most systems, imposed work of breathing increased with increasing continuous positive airway pressure level. The clinical importance of the difference in pressure stability is uncertain. Our results may facilitate the design of clinical studies examining the effect of pressure stability on outcome.

Comparison of nasal continuous positive airway pressure delivered by seven ventilators using simulated neonatal breathing.

Objectives: Nasal continuous positive airway pressure (NCPAP) is an established treatment for respiratory distress in neonates. Most modern ventilators are able to provide NCPAP. There have been no large studies examining the properties of NCPAP delivered by ventilators. The aim of this study was to compare pressure stability and imposed work of breathing (iWOB) for NCPAP delivered by ventilators using simulated neonatal breathing. Design: Experimental in vitro study. Setting: Research laboratory in Sweden. Intervention: None. Measurements and Main Results: Neonatal breathing was simulated using a mechanical lung simulator. Seven ventilators were tested at different CPAP levels using two breath profiles. Pressure stability and iWOB were determined. Results from three ventilators revealed that they provided a slight pressure support. For these ventilators, iWOB could not be calculated. There were large differences in pressure stability and iWOB between the tested ventilators. For simulations using the 3.4-kg breath profile, the pressure swings around the mean pressure were more than five times greater, and iWOB more than four times higher, for the system with the highest measured values compared with the system with the lowest. Overall, the Fabian ventilator was the most pressure stable system. Evita XL and SERVO-i were found more pressure stable than Fabian in some simulations. The results for iWOB were in accordance with pressure stability for systems that allowed determination of this variable. Conclusions: Some of the tested ventilators unexpectedly provided a minor degree of pressure support. In terms of pressure stability, we have not found any advantages of ventilators as a group compared with Bubble CPAP, Neopuff, and variable flow generators that were tested in our previous study. The variation between individual systems is great within both categories. The clinical importance of these findings needs further investigation.

Initial stabilisation of preterm infants: a new resuscitation system with low imposed work of breathing for use with face mask or nasal prongs

Objective T-piece resuscitation systems are pressure unstable and have high imposed work of breathing (iWOB). Pressure stable respiratory support with low iWOB might improve outcome. We have developed a new resuscitation system that can be used with nasal prongs or face mask. The aim of the study was to describe the in vitro performance of the new system and to perform a clinical feasibility trial of initial stabilisation of preterm infants. Method A mechanical lung model was used to determine iWOB at increasing levels of continuous positive airway pressure (CPAP). The feasibility trial included 36 infants (27–34 weeks of gestation), who were randomised into three groups (T-piece, new system with face mask or new system with prongs). Collected data included problems with usage, safety, time to stable breathing, need for positive pressure ventilation and intubation. Results In the mechanical lung model, the new system reduced iWOB with 91.5% (mask) and 86.6% (medium prongs) compared with Neopuff (4 cm CPAP, p<0.001). Informed consent was obtained from 45 patients, 39 were randomised and 36 needed support. Randomisation resulted in an imbalance: The group of new system infants had lower gestational age compared with the T-piece group. Thirteen patients needed positive pressure ventilation (median 20 cm H2O). One infant was intubated. The study did not reveal problems with the equipment or safety. Conclusions Compared with T-piece systems, the new system had a marked reduction in iWOB in bench tests. The feasibility trial did not reveal problems with usability or safety.

Return of neonatal CPAP resistance - the Medijet device family examined using in-vitro flow simulations

Medijet nasal continuous positive airway pressure (CPAP) generators are a family of devices developed from the Benveniste valve. Previous studies have shown that the in vitro performance of the Medijet disposable generator was similar to the Neopuff resistor system. We hypothesised that resistance would be the main mechanism of CPAP generation in the Medijet disposable generator.

Imposed Work of Breathing for Flow Meters with In-Line versus Flow-Through Technique during Simulated Neonatal Breathing

Background The ability to determine airflow during nasal CPAP (NCPAP) treatment without adding dead space or resistance would be useful when investigating the physiologic effects of different NCPAP systems on breathing. The aim of this study was to investigate the effect on pressure stability of different flow measuring devices at the in-line and flow-through position, using simulated neonatal breathing. Methods Six different flow measure devices were evaluated by recording pressure changes and imposed work of breathing for breaths with 16 and 32 ml tidal volumes. The tests were performed initially with the devices in an in line position and with 5 and 10 L/min using flow through technique, without CPAP. The flow meters were then subsequently tested with an Infant Flow CPAP system at 3, 5 and 8 cm H2O pressure using flow through technique. The quality of the recorded signals was compared graphically. Results The resistance of the measuring devices generated pressure swings and imposed work of breathing. With bias flow, the resistance also generated CPAP pressure. Three of the devices had low resistance and generated no changes in pressure stability or CPAP pressure. The two devices intended for neonatal use had the highest measured resistance. Conclusion The importance of pressure stability and increased work of breathing during non-invasive respiratory support are insufficiently studied. Clinical trials using flow-through technique have not focused on pressure stability. Our results indicate that a flow-through technique might be a way forward in obtaining a sufficiently high signal quality without the added effects of rebreathing and increased work of breathing. The results should stimulate further research and the development of equipment for dynamic flow measurements in neonates.

Correction: Infant CPAP for low-income countries: An experimental comparison of standard bubble CPAP and the Pumani system

[This corrects the article DOI: 10.1371/journal.pone.0196683.].

Seven Ventilators Challenged With Leaks During Neonatal Nasal CPAP: An Experimental Pilot Study

BACKGROUND: Nasal CPAP is the most common respiratory support for neonates. Several factors are considered important for effective treatment, including leaks at the patient interface and the delivery of pressure-stable CPAP. Investigations of pressure stability during leaks should include both the change in the mean delivered CPAP and the pressure variation during each breath. The aim of this study was to examine the response of ventilators delivering nasal CPAP when challenged with leaks at the patient interface. METHODS: Seven ventilators providing nasal CPAP at 4 cm H2O were challenged with leaks during simulated neonatal breathing. Leak was applied for 15 consecutive breaths at a constant level (1–4 L/min). RESULTS: The 2 aspects of pressure stability were evaluated by measuring the mean delivered CPAP and the amplitude of pressure swings before, during, and after leaks. The ability to maintain the delivered CPAP and the amplitude of pressure swings varied greatly among the 7 ventilators before, during, and after leaks. Four of the ventilators tested have built-in leak compensation. CONCLUSIONS: There was no simple relationship between maintaining delivered CPAP during leaks and providing CPAP with low pressure swing amplitude. Maintaining the delivered CPAP and providing this without pressure swings are 2 separate aspects of pressure stability, and investigations concerning the clinical importance of pressure stability should address both aspects. This study also shows that compensation for leaks does not necessarily provide pressure-stable CPAP.

398 Seven Ventilators Delivering Nasal CPAP Challenged with Leakage: an Experimental Pilot Study

Introduction Nasal Continuous Positive Airway Pressure (nCPAP) is an established treatment for respiratory distress in neonates. Most modern ventilators are able to provide nCPAP. Compared to traditional nCPAP delivery systems ventilators are more complex and allow correction for leakage. There have been no large studies examining the response to leakage for nCPAP delivered by ventilators. The aim of this pilot study was to compare pressure stability for nCPAP delivered by ventilators using simulated neonatal breathing and constant leakage. Methods Neonatal breathing was simulated by using a mechanical lung simulator. Seven ventilators were tested with recommended prongs, humidifier and tubing. Tests were performed with a breath profile from a 3.4 kg infant and nCPAP of 4 cm H2O. Constant leakage at 1-2-3-4 l/min was introduced after 30 breaths. Pressure stability was measured as pressure increase and decrease from mean pressure. Leakage stability was measured as change in mean pressure. Calculations were performed for each breath. Results The pressure stability of the tested ventilators showed large variations before introducing leakage. Fabian, Evita XL and SERVO-i were the most pressure stable systems (with and without leakage). Changes in mean pressure with leakage also showed large variations. Four of the ventilators had leakage compensation. Conclusion The tested ventilators showed large variations in pressure stability and ability to maintain pressure when exposed to leakage. Ability to maintain mean pressure and provide pressure stable nCPAP are different aspects of nCPAP systems. Being able to compensate for leakage does not necessarily give more pressure stable nCPAP.