Alla Kushnir, MD, Judy Saslow MD, Linda Slater-Myer, MD Effect of Prolonged Inspiratory Time Using High-Frequency Jet Ventilator on Respiratory Settings Alla Kushnir, MD, Judy Saslow MD, Linda Slater-Myer, MD Department of Pediatrics, Cooper University Hospital, Camden, NJ Abstract Background: Preterm infants often develop lung disease, which may lead to hypoxemic refractory respiratory failure (HRRF). High-frequency ventilation is the standard of care for patients with respiratory failure in neonatal intensive care units (NICU). High frequency jet ventilation (HFJV) delivers small tidal volumes in a very short inspiratory time (iTime) at high rates. Pulmonary Time Constant is the time it takes to get most (63%) of a tidal volume in or out of lungs. iTime usually allows adequate time for passive exhalation, but may need to be adjusted in the setting of poor ventilation. Objective: To examine changes in respiratory settings using HFJV after increase in inspiratory time. Design/Methods: IRB approved prospective observational study of infants with HRRF (Oxygenation Index >20 or requiring >60% oxygen) who were on high frequency jet ventilator (HFJV) between 1/2011 and 8/2015 and required increase in iTime due to respiratory acidosis and difficulty in ventilation. The data was collected for 24 hours after requiring increase in iTime. Ventilator settings, oxygen saturation, and fraction of inspired oxygen were collected every 4 hours for 24 hours. Demographic information was also evaluated. Results: Total of 8 changes in iTime were recorded on 5 preterm infants from 7/2013 to 7/2015. Patients had a mean gestational age of 25.6 weeks (23-31weeks) and birth weight of 853 grams (542 -1515g) and the change in iTime was made on average on day of life 29.6 (15-42). Average Jet positive inspiratory pressure (PIP) at the time of the change was 47 (44-50). There was a 13% improvement in CO2 on the first blood gas after change in iTime and a 23% improvement after 12 hours. There was a no change in the Jet PIP used after 12 and 24 hours (47 and 48 respectively) or other ventilator settings. Pneumonia was commonly seen in these patients (75%). Conclusions: Based on this small sample, change in the iTime is a plausible and possibly helpful option in patients with severe respiratory acidosis requiring very high Jet PIP. Methods IRB approved prospective observational study of infants from 1/2011 to 1/2014. All infants developed HRRF and were switched from HFOV to HFJV. The data was collected while the patients were being switched from HFOV to HFJV and for 1 week after the switch. All infants required very high Jet positive inspiratory pressure (JPIP) due to respiratory acidosis. Ventilator settings, oxygen saturations, blood gas pH and carbon dioxide (CO2) (when available), were collected every 2 hours for 8 hours, then every 4 hours for 16 hours. Respiratory failure defined as OI of > 20 with MAP providing optimum lung expansion on HFOV. Each change in iTime was considered a separate event. Characteristics of all neonates changed to HFJV Respiratory Demographics n (%) Gender Male 4(50) Sepsis, n (%) 5 (63) Pneumonia 6 (75) BPD 4 (50) IVH Severe ROP Mean Length of Stay, days 57 Death, n (%) Change in iTime event Gestational age, weeks Birth Weight, grams iTime Initial Jet PIP Initial CO2 CO2 at 12 hours Initial pH pH at 12 hours 1   23 542 0.024 50 61 68 7.35 7.28 2 24 685 0.022 44 66 65 7.27 3 31 1515 47 49 7.40 7.29 4 72 59 7.32 7.41 5 640 112 42 7.09 7.42 6 645 46 69 NA 7.21 7 0.026 75 7.34 8 48 77 7.18 7.37 Introduction Preterm infants often develop lung disease, which may lead to hypoxemic refractory respiratory failure (HRRF). High-frequency ventilation is the standard of care for these patients in neonatal intensive care units (NICU). High frequency jet ventilation (HFJV) delivers small tidal volumes in a very short inspiratory time (iTime) at high rates. Pulmonary Time Constant is the time it takes to get most (63%) of a tidal volume in or out of lungs. Increasing iTime from the standard 0.020 will increase tidal volumes in the setting of poor ventilation, while still allowing adequate time for more complete gas release via passive exhalation. Mean Carbon Dioxide after change in HFJV Inspiratory Time and throughout 24 hours Mean Jet Positive Inspiratory Pressure after change in HFJV Inspiratory Time and throughout 24 hours Results Total of 8 changes in iTime were recorded on 5 preterm infants from 7/2013 to 7/2015. Patients had a mean gestational age of 25.6 weeks (23-31weeks) and birth weight of 853 grams (542 -1515g). Change in iTime was made on average on day of life 29.6 (15-42). Average JPIP at the time of the change was 47 (44-50). There was a 13% improvement in CO2 on the first blood gas after change in iTime and a 23% improvement after 12 hours. There was no change in the JPIP after 12 and 24 hours (47 and 48 respectively) or any other ventilator settings. Pneumonia was commonly seen in these patients (75%). Objective To examine changes in respiratory settings using HFJV after increase in inspiratory time. Conclusions Based on this small sample, changing iTime is a plausible option in patients with severe respiratory acidosis requiring high JPIP with uncertain clinical benefits References 1. Cotten M, Clark RH. The science of neonatal high-frequency ventilation. Respiratory care clinics of North America 2001;7(4):611-31. 2. Bass AL, Gentile MA, Heinz JP, Craig DM, Hamel DS, Cheifetz IM. Setting positive end-expiratory pressure during jet ventilation to replicate the mean airway pressure of oscillatory ventilation. Respiratory care 2007;52(1):50-5. 3. 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