Helmut D. Hummler

Decreased accuracy of pulse oximetry measurements during low perfusion caused by sepsis: Is the perfusion index of any value?

ObjectiveTo evaluate the effects of deteriorating perfusion caused by sepsis on the accuracy of pulse oximetry measurements using two more recently available techniques (Nellcor N-395 and Masimo Radical) and to evaluate the perfusion index as axa0marker of impaired peripheral perfusion to indicate that accuracy of pulse oximetry readings may be affected.Design and settingInterventional cohort study in axa0university animal research facility.SubjectsThirty-seven adult anesthetized, ventilated rabbits.InterventionsPneumonia/sepsis was induced by tracheal instillation of Escherichia coli.Measurements and resultsOxygen saturation and perfusion index as axa0marker of peripheral perfusion were measured by pulse oximetry (SpO2) and recorded continuously for 8u202fh. Arterial oxygen saturation (SaO2) was measured every 30u202fmin by CO oximetry, and bias (SpO2u202f−u202fSaO2) was calculated at each time point for each device to assess time-dependent changes in bias. Bias increased significantly across time for both devices tested comparing the first with the second half of the experimental period. Bias measurements during the second half of the experimental time were beyond the ±3% error limit in 21.4% of cases with Nellcor and in 22.6% with Masimo. Axa0lower perfusion index was associated with increased bias, but sensitivity, specificity, and positive and negative predictive values of this marker for increased bias was very limited.ConclusionsWe conclude that accuracy of pulse oximetry measurements was considerably affected with both devices with progressively deteriorating hemodynamics in this animal model of severe sepsis. Perfusion index as axa0marker for increased risk of bias was not axa0useful tool.

Permissive hypercapnia in extremely low birthweight infants (PHELBI): a randomised controlled multicentre trial

BACKGROUNDnTolerating higher partial pressure of carbon dioxide (pCO2) in mechanically ventilated, extremely low birthweight infants might reduce ventilator-induced lung injury and bronchopulmonary dysplasia. We aimed to test the hypothesis that higher target ranges for pCO2 decrease the rate of bronchopulmonary dysplasia or death.nnnMETHODSnIn this randomised multicentre trial, we recruited infants from 16 tertiary care perinatal centres in Germany with birthweight between 400 g and 1000 g and gestational age 23-28 weeks plus 6 days, who needed endotracheal intubation and mechanical ventilation within 24 h of birth. Infants were randomly assigned to either a high target or control group. The high target group aimed at pCO2 values of 55-65 mm Hg on postnatal days 1-3, 60-70 mm Hg on days 4-6, and 65-75 mm Hg on days 7-14, and the control target at pCO2 40-50 mmHg on days 1-3, 45-55 mm Hg on days 4-6, and 50-60 mm Hg on days 7-14. The primary outcome was death or moderate to severe bronchopulmonary dysplasia, defined as need for mechanical pressure support or supplemental oxygen at 36 weeks postmenstrual age. Cranial ultrasonograms were assessed centrally by a masked paediatric radiologist. This trial is registered with the ISRCTN registry, number ISRCTN56143743.nnnRESULTSnBetween March 1, 2008, and July 31, 2012, we recruited 362 patients of whom three dropped out, leaving 179 patients in the high target and 180 in the control group. The trial was stopped after an interim analysis (n=359). The rate of bronchopulmonary dysplasia or death in the high target group (65/179 [36%]) did not differ significantly from the control group (54/180 [30%]; p=0·18). Mortality was 25 (14%) in the high target group and 19 (11%; p=0·32) in the control group, grade 3-4 intraventricular haemorrhage was 26 (15%) and 21 (12%; p=0·30), and the rate of severe retinopathy recorded was 20 (11%) and 26 (14%; p=0·36).nnnINTERPRETATIONnTargeting a higher pCO2 did not decrease the rate of bronchopulmonary dysplasia or death in ventilated preterm infants. The rates of mortality, intraventricular haemorrhage, and retinopathy did not differ between groups. These results suggest that higher pCO2 targets than in the slightly hypercapnic control group do not confer increased benefits such as lung protection.nnnFUNDINGnDeutsche Forschungsgemeinschaft.

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

OBJECTIVEnTo 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.nnnSTUDY DESIGNnFifteen 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.nnnRESULTSnPercentage 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).nnnCONCLUSIONnAutomated 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.

Volume-controlled intermittent mandatory ventilation in preterm infants with hypoxemic episodes.

ObjectiveTo test the hypothesis in ventilated very low birth weight infants with frequent hypoxemic episodes that volume-controlled synchronized intermittent mandatory ventilation (SIMV) vs. pressure-controlled SIMV reduces by at least 20% the time with hypoxemia (defined as SpO2<u202f80%).DesignRandomized cross-over design.SettingUniversity-based tertiary neonatal intensive care unit.Patients15 mechanically ventilated very low birth weight infants with frequent hypoxemic episodes.InterventionsThe infants were exposed in random order to volume-controlled and pressure-controlled SIMV for 4u202fh each. The target tidal volume during volume-controlled SIMV was matched to the tidal volume measured during pressure-controlled SIMV. FIO2 was adjusted using uniform criteria to maintain SpO2 within the target range (SpO2 80–92%).Measurements and resultsPrimary outcome measure was the time with an SpO2<u202f80%. Although tidal volume was maintained better during desaturations with volume-controlled SIMV, there was neither axa0significant difference in time with an SpO2<u202f80% (expressed as proportion of total experimental time; median, interquartile range)—volume-control 10.6% (9.2–13.7%) vs. pressure-control 10.8% (8.3–13.3%)—nor in FIO2 exposure. During volume-controlled SIMV the infants spent less time with an SpO2 above the target range and had fewer associated bradycardias.ConclusionVolume-controlled SIMV did not decrease the time with an SpO2<u202f80%, although tidal volume was better maintained during these episodes and bradycardias were less frequent than with pressure-controlled SIMV in this population of very low birth weight infants with frequent hypoxemic episodes.

Adaptive mechanical backup ventilation for preterm infants on respiratory assist modes - a pilot study

Background Mechanical respiratory-assist modes, such as assist/control, low-rate intermittent mandatory ventilation, continuous positive airway pressure, or proportional assist ventilation (PAV), require axa0continuous respiratory effort. Because of the frequent occurrence of periodic breathing and/or apnea, mechanical backup ventilation must be initiated during episodes of reduced or absent respiratory drive to maintain gas exchange. The common approach to this problem is axa0regular conventional mechanical ventilation, which is initiated and withdrawn in an “on/off” function.ObjectiveTo develop and evaluate axa0mechanical backup ventilation mode that is adaptive to the rapidly changing breathing pattern of preterm infants.DesignProspective randomized clinical crossover trial.SettingNeonatal intensive care unit at the University of Munich, Germany.PatientsPreterm infants undergoing PAV.InterventionsThe infants were ventilated with PAV using axa0newly developed adaptive backup support, with and without pulse-oximetry-guided operation (SpO2-sensitive backup). Each infant was ventilated with both modes of backup support on 2 consecutive days, with the sequence randomized.Measurements and resultsThe analysis on 11 preterm infants showed axa0statistically significant and clinically relevant reduction of the incidence (33%) and duration of oxygen desaturations (52%) when SpO2-sensitive adaptive backup support was used.ConclusionsSpO2-sensitive adaptive backup proved safe and effective in reducing the incidence and duration of oxygen desaturation in this short-term trial. This technology is potentially applicable to other assisted modalities of ventilation, such as noninvasive nasal ventilation.

Very Low Tidal Volume Ventilation with Associated Hypercapnia - Effects on Lung Injury in a Model for Acute Respiratory Distress Syndrome

Background Ventilation using low tidal volumes with permission of hypercapnia is recommended to protect the lung in acute respiratory distress syndrome. However, the most lung protective tidal volume in association with hypercapnia is unknown. The aim of this study was to assess the effects of different tidal volumes with associated hypercapnia on lung injury and gas exchange in a model for acute respiratory distress syndrome. Methodology/Principal Findings In this randomized controlled experiment sixty-four surfactant-depleted rabbits were exposed to 6 hours of mechanical ventilation with the following targets: Group 1: tidal volumeu200a=u200a8–10 ml/kg/PaCO2u200a=u200a40 mm Hg; Group 2: tidal volumeu200a=u200a4–5 ml/kg/PaCO2u200a=u200a80 mm Hg; Group 3: tidal volumeu200a=u200a3–4 ml/kg/PaCO2u200a=u200a120 mm Hg; Group 4: tidal volumeu200a=u200a2–3 ml/kg/PaCO2u200a=u200a160 mm Hg. Decreased wet-dry weight ratios of the lungs, lower histological lung injury scores and higher PaO2 were found in all low tidal volume/hypercapnia groups (group 2, 3, 4) as compared to the group with conventional tidal volume/normocapnia (group 1). The reduction of the tidal volume below 4–5 ml/kg did not enhance lung protection. However, oxygenation and lung protection were maintained at extremely low tidal volumes in association with very severe hypercapnia and no adverse hemodynamic effects were observed with this strategy. Conclusion Ventilation with low tidal volumes and associated hypercapnia was lung protective. A tidal volume below 4–5 ml/kg/PaCO2 80 mm Hg with concomitant more severe hypercapnic acidosis did not increase lung protection in this surfactant deficiency model. However, even at extremely low tidal volumes in association with severe hypercapnia lung protection and oxygenation were maintained.

Automated adjustments of inspired fraction of oxygen to avoid hypoxemia and hyperoxemia in neonates - a systematic review on clinical studies.

Supplemental oxygen is commonly provided during transition of neonates immediately after birth. Whereas an initial FiO2 of 0.21 is now recommended to stabilize full-term infants in the delivery room, the best FiO2 to start resuscitation of the very low birth weight infant (VLBWI) immediately after delivery is currently not known. Recent recommendations include the use of pulse oximetry to titrate the use of supplemental oxygen. As reference values for pulse oximetry during the first minutes of life have become available, automated FiO2-adjustments are feasible and may be very useful for delivery room care to limit oxygen exposure. Beyond neonatal transition, preterm infants in the neonatal intensive care unit (NICU) commonly require supplemental oxygen to avoid hypoxemia, especially VLBWI receiving respiratory support because of poor respiratory drive and/or lung disease. For respiratory care of newborn infants in the NICU automated FiO2-adjustment systems have been developed and have been studied in preterm infants for limited time frames using short-term physiological outcomes. These studies could demonstrate short-term benefits such as more stable arterial oxygen saturation. Recent clinical trials have shown that oxygen targeting may significantly affect mortality and morbidity. Therefore, randomized controlled trials are needed to study the effects of automated FiO2-adjustment on long-term outcomes to prove possible benefits on survival, the rate of retino-pathy of prematurity and on neuro-development-al outcome.

Benchmarking in neonatal intensive care: obstetrical and neonatal practices and registration policies may influence outcome data

Many regional, national or international neonatal networks, such as the Vermont Oxford Network or the EuroNeoNet, collect data on the outcome of very low birth weight infants (VLBWI) for benchmarking in order to improve quality of care. Whereas physicians use these data to assure quality of the outcomes of interest and to target interventions and new treatments, data collected on a national level may be used by political or healthcare organisations to reorganise their healthcare system. Furthermore, pregnant mothers with threatened preterm delivery may use data from individual units to decide at which perinatal centre they want treatment to be provided. Specifically, pregnant mothers and their families may want to know the chances of survival to discharge and the risk for morbidity as both outcomes may affect their life dramatically. This aspect is extremely important in the situation of threatened preterm delivery at the threshold of viability for decision making on a provision of life support.nnThe obstetrical approach at the lower limit of viability may vary widely. In a prospective study comparing 10 different regions across Europe, some key obstetric interventions such as administration of corticosteroids, antenatal transfer to a level III perinatal centre and caesarean section for fetal reasons were provided very differently for pregnant mothers and their preterm babies at the threshold of viability.1 Furthermore, the rate of births declared as stillbirths were more than 10 times …

Ancillary therapies to enhance success of non-invasive modes of respiratory support – Approaches to delivery room use of surfactant and caffeine?

During recent decades, non-invasive respiratory support has become popular for treating neonates with respiratory failure. Several prospective randomized controlled trials have been performed to compare use of continuous positive airway pressure (CPAP) as primary respiratory support in preterm infants with respiratory distress syndrome (RDS) to endotracheal intubation, mechanical ventilation and surfactant therapy. Systematic reviews of these studies suggest that routine CPAP at delivery is efficacious in decreasing bronchopulmonary dysplasia (BPD), death, or both. This led to the recommendation to consider CPAP to avoid endotracheal intubation. As surfactant therapy is known to reduce BPD and death, several ways to combine CPAP with surfactant have been described. With the increasing use of CPAP immediately after birth, the early use of caffeine to stimulate respiration has become a point of discussion. This review focuses on different modes of surfactant application during CPAP and on the early use of caffeine as ancillary therapies to enhance CPAP success.

The Cause of Acute Respiratory Failure Predicts the Outcome of Noninvasive Ventilation in Immunocompromised Children.

BACKGROUNDnNoninvasive ventilation (NIV) may be superior to conventional therapy in immunocompromised children with respiratory failure.nnnMETHODSnMortality, success rate, prognostic factors and side effects of NIV for acute respiratory failure (ARF) were investigated retrospectively in 41 in children with primary immunodeficiency, after stem cell transplantation or chemotherapy for oncologic disease.nnnRESULTSnIn 11/41 (27%) children invasive ventilation was avoided and patients were discharged from ICU. In children with NIV failure ICU-mortality was 19/30 (63%). 8/11 (72%) children with NIV success had recurrence of ARF after 27 days. Only 4/11 (36%) children with first episode NIV success and 8/30 (27%) with NIV failure survived to hospital discharge. Lower FiO2, SpO2/FiO2 and blood culture positive bacterial sepsis were predictive for NIV success, while fungal sepsis or culture negative ARF were predictive for NIV failure. We observed catecholamine treatment in 14/41 (34%), pneumothorax in 2/41 (5%), mediastinal emphysema in 3/41 (7%), a life threatening nasopharyngeal hemorrhage and need for resuscitation during intubation in 5/41 (12%) NIV-episodes.nnnCONCLUSIONSnThe prognosis of ARF in immunocompromised children remains guarded independent of initial success or failure of NIV due to a high rate of recurrent ARF. Reversible causes like bacterial sepsis had a higher NIV response rate. Relevant side effects of NIV were observed.