Markus Waitz

Automated versus Manual Oxygen Control with Different Saturation Targets and Modes of Respiratory Support in Preterm Infants.

OBJECTIVE To determine the efficacy and safety of automated adjustment of the fraction of inspired oxygen (FiO2) in maintaining arterial oxygen saturation (SpO2) within a higher (91%-95%) and a lower (89%-93%) target range in preterm infants. STUDY DESIGN Eighty preterm infants (gestational age [median]: 26 weeks, age [median] 18 days) on noninvasive (n = 50) and invasive (n = 30) respiratory support with supplemental oxygen, were first randomized to one of the SpO2 target ranges and then treated with automated FiO2 (A-FiO2) and manual FiO2 (M-FiO2) oxygen control for 24 hours each, in random sequence. RESULTS The percent time within the target range was higher during A-FiO2 compared with M-FiO2 control. This effect was more pronounced in the lower SpO2 target range (62 ± 17% vs 54 ± 16%, P < .001) than in the higher SpO2 target range (62 ± 17% vs 58 ± 15%, P < .001). The percent time spent below the target or in hypoxemia (SpO2 <80%) was consistently reduced during A-FiO2, independent of the target range. The time spent above the target range or at extreme hyperoxemia (SpO2 >98%) was only reduced during A-FiO2 when targeting the lower SpO2 range (89%-93%). These outcomes did not differ between infants on noninvasive and invasive respiratory support. Manual adjustments were significantly reduced during A-FiO2 control. CONCLUSIONS A-FiO2 control improved SpO2 targeting across different SpO2 ranges and reduced hypoxemia in preterm infants on noninvasive and invasive respiratory support. TRIAL REGISTRATION ISRCTN 56626482.

Effects of Automated Adjustment of the Inspired Oxygen on Fluctuations of Arterial and Regional Cerebral Tissue Oxygenation in Preterm Infants with Frequent Desaturations

OBJECTIVE To assess the effect of automated adjustment of the inspired oxygen fraction (FiO2) on arterial oxygen saturation (SpO2) and cerebral tissue oxygen saturation (SctO2) in very low birth weight infants with frequent fluctuations in oxygenation. STUDY DESIGN Fifteen infants (median gestational age, 25 weeks [range, 23-28 weeks]; median age, 34 days [range, 19-74 days]) were assigned in random sequence to 24 hours of automated adjustment of FiO2 or manual adjustment of FiO2. Primary outcome measurements were time within the SpO2 target range and the area under the curve above and below a defined SctO2 range. RESULTS Percentage of time within the SpO2 target range increased during automated FiO2 control (76.3% ± 9.2% vs 69.1% ± 8.2% for manual; P < .01). Prolonged episodes with SpO2 <88% of >60 seconds duration (median, 115 episodes [range, 67-240] vs 54 episodes [range, 7-184]; P < .01) and of >180 seconds duration (median, 13 episodes [range, 6-39] vs 2 episodes [range, 0-5]; P < .01) decreased significantly during the automated period. Percentage of time with SpO2 >96% decreased during automated control (6.6% ± 4.4% vs 10.4% ± 3.3%; P < .02). There was no significant difference in FiO2 exposure. The area (deviation × time) below and above the defined SctO2 threshold did not differ between the 2 periods (median, 59.7%*seconds [range, 17.2%-208.3%] for manual vs 49.0%*seconds [range, 4.3%-193.7%] for automated; P = .36). CONCLUSION Automated FiO2 control in preterm infants with frequent SpO2 fluctuations significantly increased the time within the SpO2 target range and reduced the incidence of prolonged hypoxemic events compared with manual FiO2 adjustment, but did not significantly affect cerebral tissue oxygenation.

Effects of Synchronization during Noninvasive Intermittent Mandatory Ventilation in Preterm Infants with Respiratory Distress Syndrome Immediately after Extubation.

Background: Noninvasive ventilation is increasingly used in very-low-birth-weight infants (VLBWI) to reduce complications that occur with invasive ventilation. However, the physiological effects of synchronization during noninvasive nasal intermittent mandatory ventilation (IMV) have not been tested in VLBWI immediately after extubation. Objective: We aimed to study the short-term effects of synchronized nasal IMV (S-NIMV) compared to nonsynchronized nasal IMV (NIMV) on breathing effort as measured by phasic esophageal pressure (Pe) deflection, spontaneous respiratory rate (RR), gas exchange, cerebral tissue oxygen saturation (StO2) and intermittent episodes of bradycardia or hypoxemia in VLBWI recovering from respiratory distress syndrome (RDS). Methods: Fourteen VLBWI recovering from RDS were studied using a randomized cross-over design during both S-NIMV and NIMV (of 2 h each) immediately after extubation. Results: Phasic Pe deflection, spontaneous RR and transcutaneous PCO2 decreased significantly while transcutaneous PO2 and synchrony rate (defined as peak ventilator pressure delivered within the first half of spontaneous inspiration) increased significantly during S-NIMV compared to during NIMV. There was no difference in blood pressure, average arterial oxygen saturation (SpO2), cerebral StO2, fractional tissue oxygen extraction of the brain and severe bradycardia (defined as time with a heart rate <100 beats/min lasting ≥10 s) and in hypoxemic episodes (SpO2 <80%) between the two modes. Conclusion: Synchronization during nasal ventilation immediately after extubation in VLBWI recovering from RDS improved gas exchange and decreased the respiratory effort, and it could therefore be considered to provide a more efficient respiratory support and synchrony.

Effect of Different Respiratory Modes on Return of Spontaneous Circulation in a Newborn Piglet Model of Hypoxic Cardiac Arrest.

Background: There are no clear evidence-based recommendations on the use of different techniques of respiratory support and chest compressions (CC) during neonatal cardiopulmonary resuscitation (CPR). Objectives: To determine the effects of different respiratory support strategies along with CC representing clinical practice on the return of spontaneous circulation (ROSC) in hypoxic newborn piglets with cardiac arrest. We hypothesized that use of a T-piece resuscitator (TPR) providing positive end-expiratory pressure (PEEP) reduces time to ROSC as compared to a self-inflating bag (SIB) without PEEP. Furthermore, we explored the effects of a ventilator providing inflations without synchrony to CC. Methods: Thirty-three newborn piglets were exposed to hypoxia until asystole occurred and randomized into three groups and resuscitated according to ILCOR guidelines: group 1 = TPR [peak inspiratory pressure (PIP)/PEEP of 25/5 cm H2O, rate 30/min], inflations interposed between CC (3:1 ratio); group 2 = SIB (PIP of 25 cm H2O without PEEP, rate 30/min), inflations interposed between CC (3:1 ratio), and group 3 = ventilator (PIP/PEEP of 25/5 cm H2O, rate 30/min), CC were applied with a rate of 120/min without synchrony to inflations. Animals were supported for 120 min after ROSC. Primary outcome was time to ROSC. Results: All animals achieved ROSC. We found no significant difference in time to ROSC between groups [median (IQR); TPR: 150 s (150-210); SIB: 150 s (120-180); ventilator: 180 s (150-345)]. There was no difference in use of epinephrine, in blood gases or hemodynamic parameters during the 120-min observation time after ROSC. Conclusions: We found no significant effect of different respiratory support strategies during CPR on ROSC.

Reliability of Pulse Oximetry during Cardiopulmonary Resuscitation in a Piglet Model of Neonatal Cardiac Arrest

Background: Pulse oximetry is widely used in intensive care and emergency conditions to monitor arterial oxygenation and to guide oxygen therapy. Objective: To study the reliability of pulse oximetry in comparison with CO-oximetry in newborn piglets during cardiopulmonary resuscitation (CPR). Methodology: In a prospective cohort study in 30 healthy newborn piglets, cardiac arrest was induced, and thereafter each piglet received CPR for 20 min. Arterial oxygen saturation was monitored continuously by pulse oximetry (SpO2). Arterial blood was analyzed for functional oxygenation (SaO2) every 2 min. SpO2 was compared with coinciding SaO2 values and bias considered whenever the difference (SpO2 - SaO2) was beyond ±5%. Results: Bias values were decreased at the baseline measurements (mean: 2.5 ± 4.6%) with higher precision and accuracy compared with values across the experiment. Two minutes after cardiac arrest, there was a marked decrease in precision and accuracy as well as an increase in bias up to 13 ± 34%, reaching a maximum of 45.6 ± 28.3% after 10 min over a mean SaO2 range of 29-58%. Conclusion: Pulse oximetry showed increased bias and decreased accuracy and precision during CPR in a model of neonatal cardiac arrest. We recommend further studies to clarify the exact mechanisms of these false readings to improve reliability of pulse oximetry during the marked desaturation and hypoperfusion found during CPR.

Hepatitis B Postexposure Prophylaxis in Preterm and Low-Birth-Weight Infants.

Objective Recommendations for immunoprophylaxis in low-birth-weight (LBW) infants born to hepatitis B surface antigen (HBsAg)-positive mothers vary. We successfully immunized an HBsAg-exposed infant (birth weight: 400 g) and performed a literature review on the outcome of postexposure immunoprophylaxis in HBsAg-exposed preterm and LBW infants. Methods By use of PubMed we identified articles relevant to the topic. Studies were included if the intended vaccine schedule was completed and follow-up data were reported. Results Antibody response was reported in 31 LBW infants (birth weight < 2,500 g) and 49 infants with gestational age of < 38 weeks. Low anti-HBs antibody levels (< 100 IU/L) were found in 9 (29%) of the 31 LBW infants. Overall, 2 of 20 (10%) preterm infants and 2 of 17 (12%) LBW were HBsAg-positive on follow-up. In one study, none of the 26 exposed very LBW infants became infected. Conclusion Due to heterogeneity in immunization schedules, lack of information on transmission rates, and the small number of included subjects, no firm conclusions can be drawn regarding the optimal postexposure prophylaxis in LBW infants. We propose that active and passive immunization at birth should be completed by three further active doses (0–1–2–12 month schedule) until further prospective studies are available.

Different Techniques of Respiratory Support Do Not Significantly Affect Gas Exchange during Cardiopulmonary Resuscitation in a Newborn Piglet Model

Background: There are no evidence-based recommendations on the use of different techniques of respiratory support and chest compressions (CC) during neonatal cardiopulmonary resuscitation (CPR). Objectives: We studied the short-term effects of different ventilatory support strategies along with CC representing clinical practice on gas exchange [arterial oxygen saturation (SaO2), arterial partial pressure of oxygen (PaO2) and arterial partial pressure of carbon dioxide (PaCO2)], hemodynamics and cerebral oxygenation. We hypothesized that in newborn piglets with cardiac arrest, use of a T-piece resuscitator (TPR) providing positive end-expiratory pressure (PEEP) improves gas exchange as measured by SaO2 during CPR as compared to using a self-inflating bag (SIB) without PEEP. Furthermore, we explored the effects of a mechanical ventilator without synchrony to CC. Methods: Thirty newborn piglets with asystole were randomized into three groups and resuscitated for 20 min [fraction of inspired oxygen (FiO2) = 0.21 for 10 min and 1.0 thereafter]. Group 1 received ventilation using a TPR [peak inspiratory pressure (PIP)/PEEP of 20/5 cm H2O, rate 30/min] with inflations interposed between CC (3:1 ratio). Group 2 received ventilation using a SIB (PIP of 20 cm H2O without PEEP, rate 30/min) with inflations interposed between CC (3:1 ratio). Group 3 received ventilation using a mechanical ventilator (PIP/PEEP of 20/5 cm H2O, rate 30/min). CC were applied with a rate of 120/min without synchrony to inflations. Results: We found no significant differences in SaO2 between the three groups. However, there was a trend toward a higher SaO2 [TPR: 28.0% (22.3-40.0); SIB: 23.7% (13.4-52.3); ventilator: 44.1% (39.2-54.3); median (interquartile range)] and a lower PaCO2 [TPR: 95.6 mm Hg (82.1-113.6); SIB: 100.8 mm Hg (83.0-108.0); ventilator: 74.1 mm Hg (68.5-83.1); median (interquartile range)] in the mechanical ventilator group. Conclusions: We found no significant effect on gas exchange using different respiratory support strategies during CPR.

Effects of a new device for automated closed loop control of inspired oxygen concentration on fluctuations of arterial and different regional organ tissue oxygen saturations in preterm infants

Objective To assess the efficacy of a newly developed system for closed loop control of the fraction of inspired oxygen (FiO2) on variation of arterial (SpO2) and on regional tissue oxygen saturation (StO2) in preterm infants with fluctuations in SpO2. Design Randomised crossover trial comparing automated (auto) to manual FiO2 adjustment (manual) during two consecutive 24 hours periods using a Sophie infant ventilator (SPO2C). Setting Tertiary university medical centre. Patients Twelve very low birthweight infant (VLBWI) (gestational age (median; IQR): (25; 23–26 weeks); birth weight (mean±SD): (667±134 g); postnatal age (mean±SD): (31.5±14 days)). Main outcome measure Time within SpO2 target range. Results There was an increase in time within the intended SpO2 target range (88%–96%) during auto as compared with manual mode (77.8%±7.1% vs 68.5%±7.7% (mean±SD), p<0.001) and a decrease in time below the SpO2 target during the auto period (18.1%±6.4% vs 25.6%±7.6%; p<0.01). There was a dramatic reduction in events with an SpO2 <88% with >180 s duration: (2 (0–10) vs 10 (0–37) events, p<0.001) and the need for manual adjustments. The time the infants spent above the intended arterial oxygen range (4.1%±3.8% vs 5.9%±3.6%), median FiO2, mean SpO2 over time and StO2 in the brain, liver and kidney did not differ significantly between the two periods. Conclusions Closed-loop FiO2 using SPO2C significantly increased time of arterial SpO2 within the intended range in VLBWI and decreased the need for manual adjustments when compared with the routine adjustment by staff members. StO2 was not significantly affected by the mode of oxygen control.

Reliability of Pulse Oximetry during Progressive Hypoxia, Cardiopulmonary Resuscitation, and Recovery in a Piglet Model of Neonatal Hypoxic Cardiac Arrest

Background: Pulse oximetry is widely used in intensive care and emergency conditions to monitor arterial oxygenation and to guide oxygen therapy. Objective: To study the reliability of pulse oximetry in comparison with CO-oximetry in newborn piglets during progressive hypoxia, cardiac arrest, cardiopulmonary resuscitation (CPR), and after return of spontaneous circulation (ROSC). Methods: Thirty-three newborn piglets were exposed to hypoxia until asystole occurred and then resuscitated until ROSC. Arterial oxygen saturation was monitored continuously by pulse oximetry (SpO2) with one sensor applied to the wrist of the right forelimb (FL) and another to the thigh of the left hind limb (HL). Arterial functional oxygen saturation (SaO2) was measured at baseline and at predefined intervals during each phase of the experiment. SpO2 was compared with coinciding SaO2 values and bias considered whenever the difference (SpO2 - SaO2) was beyond ±5%. Results: Bias values were lower at the baseline measurements (-3.7 ± 2.3% in FL and -4.1 ± 3.4% in HL) as well as after ROSC (1.5 ± 4.2% in FL and 0.2 ± 4.6% in HL) with higher precision and accuracy than during other experiment phases. During hypoxia induction, cardiac arrest, and CPR, there was a marked decrease in precision and accuracy as well as an increase in bias up to 43 ± 26 and 56 ± 27% in FL and HL, respectively, over a range of SaO2 from 13 to 51%. Conclusion: Pulse oximetry showed increased bias and decreased accuracy and precision during marked hypoxemia in a model of neonatal hypoxic cardiac arrest.

PS-278 Automated Versus Manual Fio2 Control At Different Saturation Targets In Preterm Infants

Background Preterm infants spend only 50% of time within the target oxygen saturation (SpO2) during manual FiO2 control (M-FiO2). Automated FiO2 control (A-FiO2) improves SpO2 targeting but it is uncertain if this applies to different SpO2 target ranges and during non-invasive support (NIVS) and mechanical ventilation (MV). Objective To compare the efficacy of A-FiO2 vs M-FiO2 in keeping two different SpO2 targets during NIVS or MV. Design/methods Preterm infants on FiO2 >0.21 receiving NIVS or MV were randomised to SpO2 targets 89–93% or 91–95% and underwent M-FiO2 and A-FiO2 for 24 h each, in random sequence. Results 80 infants (GA:26 w, age:18 d) were included (NIVS = 48, MV = 32). Time within target increased and below target decreased during A-FiO2 compared with M-FiO2, especially in the lower target range. There was a reduction in time and hypoxemia episodes with SpO2 < 80% during A-FiO2. Outcomes did not differ between NIVS or MV. Conclusions Automated FiO2 control improved SpO2 targeting across different SpO2 ranges and reduced hypoxemia with less workload during both NIVS and MV. Abstract PS-278 Table 1 Target 89–93% Target 91–95% A-FiO2 M-FiO2 A-FiO2 M-FiO2 %-time in target 62 (17) 54 (16)* 62 (17) 58 (15)* %-time >target 21 (13) 25 (10)* 22 (13) 19 (8) %-time < target 17 (11) 21 (8)* 17 (10) 23 (9)* %-time SpO2 >98% 0.2 (0.0–0.8) 0.7 (0.1–1.6)* 0.7 (0.2–2.1) 1.7 (0.7–4.3) %-time SpO2 < 80% 1.2 (0.2–2.2) 2.6 (1.0–4.3)* 0.8 (0.3–2.1) 2.0 (0.9–5.0)* Episodes < 80%, >1 min/24 h 4 (1–12) 15 (5–24)* 4 (1–11) 13 (3–24)* Manual FiO2 adjustments/24h 1 (0–3) 102 (72–173)* 1 (0–3) 109 (79–156)* * p < 0.05