Flow‐synchronized NIPPV with double‐inspiratory loop cannula: An in vitro study

Abstract

Background: Although short binasal prongs (SBP) are the most common interface for noninvasive ventilation, the "double-inspiratory loop cannulas" (DILC) have recently been introduced into many neonatal intensive care units. DILC show advantages over SBP, including reduced nasal trauma and increased comfort. However, their higher intrinsic resistance may compromise ventilation. Our aim was to test a new, low resistance DILC interface. Methods: A test lung was programmed to simulate preterm neonates (500-2000 g BW) with moderate-to-severe respiratory distress syndrome. The artificial nose was designed to keep prongs-to-nares leaks to around 30%. Giulia ® ventilator (GINEVRI srl) was used to provide nasal continuous positive airway pressure (NCPAP) and flow synchronized nasal intermittent positive pressure ventilation (NIPPV). NCPAP was set at 4-10 cmH 2 O and synchronized-NIPPV (SNIPPV) at peak inspiratory pressure, 15-20-25 cmH 2 O; inspiratory time, 0.3-0.5 s; and positive end-expiratory pressure, 5-8 cmH 2 O. Four sizes of Sync-flow Cannula ® (GINEVRI srl) were tested. The Sync-flow Cannula ® was compared with Neotech RAM ® cannula and Ginevri SBP ®. The outcome measures were the flow/pressure relationship through the four Sync-flow Cannula ® sizes, the difference in resistance, the drop in ventilator-alveoli pressure measured by the test lung and the system response time during flow-SNIPPV. Results: The smaller DILC sizes had the lowest flow-pressure ratio. The resistance of the RAM ® cannula was significantly higher compared to the other interfaces (p < .001). With 30% leaks, there was a 4-38% ventilator-alveoli drop in pressure, depending on interface size. The system response time was excellent (~65-70 ms). Conclusions: With about 30% leaks, the Sync-flow Cannula ® interfaces result in good pressure transmission and give optimal performance for flow-SNIPPV. Clinical studies are needed to confirm the clinical relevance of these data.

Role of ventilator and nasal interface in pressure transmission during neonatal intermittent positive pressure ventilation: A bench study

“…Green et al showed that nasal mask has the lowest resistance, short bi‐nasal prongs have high resistance at high flow and small size, while RAM® cannula has the highest resistance. Several in‐vitro studies confirmed that RAM® cannula imposes a significantly higher resistance compared with other nasal interfaces 14,15,18 . In a bench study, Iyer et al documented a limited transmission of both PEEP and PIP to the lung with RAM® cannula during NIPPV.…”

“…It is also important to underline that RAM® cannula should not be used with no leaks (e.g., 100% nares occlusion and mouth sealed), as per manufacturer's instructions. Indeed, the use of RAM® cannula with no leaks obliges the infant to expire through the RAM® cannula itself, increasing the expiratory resistance and the risk of rebreathing 18 …”

“…Several in-vitro studies confirmed that RAM® cannula imposes a significantly higher resistance compared with other nasal interfaces. 14,15,18 In a bench study, Iyer et al…”

“…Indeed, the use of RAM® cannula with no leaks obliges the infant to expire through the RAM® cannula itself, increasing the expiratory resistance and the risk of rebreathing. 18 In the presence of leaks, only part of the delivered PEEP was transmitted to the lung, and the pressure drop was higher with large leaks and a higher resistance nasal interface, such as the RAM® cannula. Indeed, the difference between PEEP AW and PEEP GL is the product between the upper airways resistance (including the nasal interface) and the leak flow.…”

“…Several in-vitro studies confirmed that RAM® cannula imposes a significantly higher resistance compared with other nasal interfaces. 14,15,18 In a bench study, Iyer et al documented a limited transmission of both PEEP and PIP to the lung with RAM® cannula during NIPPV. Mukerji et al reported a substantial dampening of the set ventilator pressures at the lung level, and the lung pressures were significantly lower with RAM® cannula than with short bi-nasal prongs.…”