Biomedical subjects
Publications and source records attributed to Colin J Morley.
Resuscitation guidelines recommend administration of free-flow oxygen to newly born infants who breathe but remain cyanosed. Self-inflating resuscitation bags are described as unreliable for this purpose. We measured oxygen concentrations >or=80% delivered through a 240 mL Laerdal self-inflating resuscitation bag and from 5 mm tubing inside a cupped hand.
Heart rate (HR) dictates intervention during neonatal resuscitation. Guidelines recommend that HR be assessed by auscultation or palpation. We compared HRs determined clinically with electrocardiography (ECG) in healthy newborns in the delivery room. Clinical assessment by 23 observers randomly allocated to assess HR by one of two methods in 26 infants, was found to be inaccurate and underestimate ECG HR. The mean difference between HR assessed by auscultation and palpation ECG and HR using methodology recommended by the Neonatal Resuscitation Programme was 14 and 22 beats per minute respectively.
OBJECTIVE: Because the optimal concentration of oxygen (FiO2) required for stabilization of the newly born infant has not been established, the FiO2 is commonly adjusted according to the infant's oxygen saturation (SpO2). We aimed to determine the range of pre-ductal SpO2 in the first minutes of life in healthy newborn infants. STUDY DESIGN: We applied an oximetry sensor to the infant's right palm or wrist of term and preterm deliveries immediately after birth. Infants who received any resuscitation or supplemental oxygen were excluded. SpO2 was recorded at 60 second intervals for at least 5 minutes and until the SpO2 was >90%. RESULTS: A total of 205 deliveries were monitored; 30 infants were excluded from the study. SpO2 readings were obtained within 60 seconds of age from 92 of 175 infants (53%). The median (interquartile range) SpO2 at 1 minute was 63% (53%-68%). There was a gradual rise in SpO2 with time, with a median SpO2 at 5 minutes of 90% (79%-91%). CONCLUSION: Many newborns have an SpO2 <90% during the first 5 minutes of life. This should be considered when choosing SpO2 targets for infants treated with supplemental oxygen in the delivery room.
OBJECTIVES: To assess interobserver variability of Apgar scores assigned with video recordings of neonatal resuscitation (AS(video)) and compare the scores assigned by observers of videos to the Apgar score given by staff attending the delivery (AS(del)). STUDY DESIGN: Ten-second clips of 30 newborns taken at 5 minutes were shown to observers. Infants were 23 to 40 weeks' gestation, received varying degrees of resuscitation, and were monitored with pulse oximetry. Forty-two observers (neonatal/obstetric medical/nursing staff) scored infants' respiratory effort, muscle tone, reflex irritability, and color. The value for heart rate was assigned from the oximeter, which was masked in all clips. All 42 AS(video) and the AS(del) were represented graphically for each infant. Interobserver reliability was assessed by use of a variance components model. RESULTS: AS(video) varied widely between observers. Variability was large for all 4 elements of the score observers assigned and was seen irrespective of the infant's level of illness. AS(del) was greater than AS(video) in most cases, on average by 2.4 points. There was no evidence that the level of discrepancy was substantially different between groupings of staff. CONCLUSION: The Apgar score has poor interobserver reliability. More objective and precise measures of newborns' condition are required.
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OBJECTIVE: Postnatal corticosteroid therapy is controversial. The aim of this study was to determine the short-term effects of low-dose dexamethasone treatment among chronically ventilator-dependent neonates. METHODS: Very preterm (gestational age: <28 weeks) or extremely low birth weight (birth weight: <1000 g) infants who were ventilator dependent after the first 1 week of life were eligible and were assigned randomly to receive masked dexamethasone (0.89 mg/kg over 10 days) or saline placebo. Data on ventilator and oxygen requirements and deaths were recorded. RESULTS: Seventy infants were recruited from 11 centers, at a median age of 23 days. More infants were extubated successfully by 10 days of treatment in the dexamethasone group (60%, 21 of 35 patients) than in the control group (12%, 4 of 34 patients) (odds ratio [OR]: 11.2; 95% confidence interval [CI]: 3.2-39.0). Ventilator and oxygen requirements improved substantially, and the duration of intubation was shorter. There was little evidence for a reduction in either the mortality rate (dexamethasone group: 11%; control group: 20%; OR: 0.52; 95% CI: 0.14-1.95) or the rate of oxygen dependence at 36 weeks (dexamethasone group: 85%; control group: 91%; OR: 0.58; 95% CI: 0.13-2.66). There were no obvious effects of low-dose dexamethasone on blood glucose concentrations, blood pressure, or other complications. No infant experienced intestinal perforation. CONCLUSIONS: Low-dose dexamethasone treatment after the first 1 week of life clearly facilitates extubation and shortens the duration of intubation among ventilator-dependent, very preterm/extremely low birth weight infants, without any obvious short-term complications. Combined with recent evidence that infants at very high risk of bronchopulmonary dysplasia may benefit in the long term, our study reopens debate regarding the role of low-dose, late postnatal, corticosteroid therapy.
OBJECTIVE: Endotracheal intubation of newborn infants is a mandatory competence for many pediatric trainees. The Neonatal Resuscitation Program recommends a 20-second limit for intubation attempts. Intubation attempts by junior doctors are frequently unsuccessful, and many infants are intubated between 20 and 30 seconds without apparent adverse effect. Little is known about the proficiency of more senior medical staff, the time taken to determine endotracheal tube (ETT) position, or the effects of attempted intubation on infants' heart rate (HR) and oxygen saturation (Spo2) in the delivery room (DR). The objectives of this study were to determine (1) the success rates and duration of intubation attempts during DR resuscitation, (2) whether experience is associated with greater success rates and shorter time taken to intubate, (3) the time taken to identify ETT position after intubation, and (4) the frequency with which infants deteriorated during intubation attempts and the time at which this occurred. METHODS: We reviewed videos of DR resuscitations; identified whether intubation was attempted; and, when attempted, whether intubation was attempted by a resident, a fellow, or a consultant. We defined the duration of an intubation attempt as the time from the introduction of the laryngoscope blade to the mouth to its removal, regardless of whether an ETT was introduced. We determined the time from removal of the laryngoscope to the clinicians' decision as to whether the intubation was successful and noted the basis on which this decision was made (clinical assessment, flow signals, or exhaled carbon dioxide [ETCO2] detection). We determined success according to clinical signs in all cases and used flow signals that were obtained during ventilation via the ETT or ETCO2 when available. When neither was available, the chest radiograph on admission to the NICU was reviewed. For infants who were monitored with pulse oximetry, we determined their HR and Spo2 before the intubation attempt. We then determined whether either or both fell by > or =10% during the attempt and, if so, at what time it occurred. RESULTS: We reviewed 122 video recordings in which orotracheal intubation was attempted 60 times in 31 infants. We secondarily verified ETT position using flow signals, ETCO2, or chest radiographs after 94% of attempts in which an ETT was introduced. Thirty-seven (62%) attempts were successful. Success rates and mean (SD) time to intubate successfully by group were as follows: residents: 24%, 49 seconds (13 seconds); fellows: 78%, 32 seconds (13 seconds); and consultants: 86%, 25 seconds (17 seconds). Of the 23 unsuccessful attempts, 13 were abandoned without an attempt to pass an ETT and 10 were placed incorrectly. The time to determine ETT position in the DR was longer when clinical assessment alone was used. Infants who were monitored with oximetry deteriorated during nearly half of the intubation attempts. Deterioration seemed more likely when HR and Spo2 were low before the attempt. CONCLUSIONS: Intubation attempts often are unsuccessful, and successful attempts frequently take >30 seconds. Greater experience is associated with greater success rates and shorter duration of successful attempts. Flow signals and ETCO2 may be useful in determining ETT position more quickly than clinical assessment alone. Infants frequently deteriorate during intubation attempts. Improved monitoring of infants who are resuscitated in the DR is desirable.
RATIONALE: The importance of applying high-frequency oscillatory ventilation with a high lung volume strategy in infants is well established. Currently, a lack of reliable methods for assessing lung volume limits clinicians' ability to achieve the optimum volume range. OBJECTIVES: To map the pressure-volume relationship of the lung during high-frequency oscillatory ventilation in infants, to determine at what point ventilation is being applied clinically, and to describe the relationship between airway pressure, lung volume, and oxygenation. METHODS: In 12 infants, a partial inflation limb and the deflation limb of the pressure-volume relationship were mapped using a quasi-static lung volume optimization maneuver. This involved stepwise airway pressure increments to total lung capacity, followed by decrements until the closing pressure of the lung was identified. MEASUREMENTS AND MAIN RESULTS: Lung volume and oxygen saturation were recorded at each airway pressure. Lung volume was measured using respiratory inductive plethysmography. A distinct deflation limb could be mapped in each infant. Overall, oxygenation and lung volume were improved by applying ventilation on the deflation limb. Maximal lung volume and oxygenation occurred on the deflation limb at a mean airway pressure of 3 and 5 cm H(2)O below the airway pressure approximating total lung capacity, respectively. CONCLUSIONS: Using current ventilation strategies, all infants were being ventilated near the inflation limb. It is possible to delineate the deflation limb in infants receiving high-frequency oscillatory ventilation; in doing so, greater lung volume and oxygenation can be achieved, often at lower airway pressures.
In mature lungs, elevated positive end-expiratory pressure (PEEP) reduces pulmonary blood flow (PBF) and increases pulmonary vascular resistance (PVR). However, the effect of PEEP on PBF in preterm infants with immature lungs and a patent ductus arteriosus is unknown. Fetal sheep were catheterized at 124 days of gestation (term approximately 147 days), and a flow probe was placed around the left pulmonary artery to measure PBF. At 127 days, lambs were delivered and ventilated from birth with a tidal volume of 5 ml/kg and 4-cmH(2)O PEEP; PEEP was changed to 0, 8, and 12 cmH(2)O in random order, returning to 4 cmH(2)O between each change. Increasing PEEP from 4 to 8 cmH(2)O and from 4 to 12 cmH(2)O decreased PBF by 20.5 and 41.0%, respectively, and caused corresponding changes in PVR; reducing PEEP from 4 to 0 cmH(2)O did not affect PBF. Despite decreasing PBF, increasing PEEP from 4 to 8 cmH(2)O and 12 cmH(2)O improved oxygenation of lambs. Increasing and decreasing PEEP from 4 cmH(2)O significantly changed the contour of the PBF waveform; at a PEEP of 12 cmH(2)O, end-diastolic flow was reduced by 82.8% and retrograde flow was reestablished. Although increasing PEEP improves oxygenation, it adversely affects PBF and PVR shortly after birth, alters the PBF waveform, and reestablishes retrograde flow during diastole.
Epidemiological studies show that exposure to factors that restrict fetal growth or lead to low birthweight can alter lung development and have later adverse effects on lung function and respiratory health. The major causal factors include reduced nutrient and oxygen availability, nicotine exposure via maternal tobacco smoking and preterm birth, each of which can affect critical stages of lung development. Experimental studies show that these environmental insults can permanently alter lung structure and hence lung function, increasing the risk of respiratory illness and accelerating the rate of lung aging. Further studies are required that address the molecular and cellular mechanisms by which these factors adversely affect lung development and whether such effects can be blocked or reversed. Ultimately however, a major goal should be to prevent prenatal compromises through clinical monitoring, and in the case of smoking through education, thereby ensuring that each fetus has the best possible environment in which to develop.
Clinical assessment and end-tidal carbon dioxide (ETCO2) detectors are used to verify tracheal intubation in newborn infants. A case is presented in which an ETCO2 detector was misleading in determining endotracheal tube (ETT) position but useful in determining the efficacy of ventilation in an extremely preterm infant.
Application of the sensor to newly born infants before connection to a pulse oximeter increases the reliability and speed with which data are displayed. Data are available in most infants within 90 seconds of birth. Oximetry may be useful in guiding interventions during resuscitation.
BACKGROUND: Guidelines recommend neonatal resuscitation without controlling tidal volume or positive end-expiratory pressure (PEEP). However, these may improve gas exchange, lung volume and outcome. AIM: To investigate resuscitation of very premature lambs with a Laerdal bag without PEEP versus volume guarantee ventilation with PEEP. METHODS: Anaesthetized lambs (n=20) delivered at 125 d gestation were randomized to three groups receiving 15 min resuscitation: (1) Laerdal bag and no PEEP; (2) ventilation with a tidal volume of 5 ml/kg and 8 cm H(2)O PEEP; (3) ventilation with 10 ml/kg and 8 cm H(2)O PEEP. They were then all ventilated for 2 h with tidal volumes of 5 or 10 ml/kg, and 8 cm H(2)O PEEP. Ventilation parameters and blood gases were recorded. RESULTS: Different tidal volumes affected PaCO(2) within minutes, with 10 ml/kg causing severe hypocarbia. PEEP had little effect on PaCO(2). Oxygenation improved significantly with PEEP of 8 cm H(2)O, irrespective of tidal volume. CONCLUSION: Very premature lambs can be resuscitated effectively using volume-guarantee ventilation and PEEP. Tidal volumes affected PaCO(2) within minutes but had little effect on oxygenation. PEEP halved the oxygen requirement compared with no PEEP. Resuscitating premature babies with controlled tidal volumes and PEEP might improve their outcome.
AIM: Neonatal resuscitation is a common and important intervention. International consensus statements advise how newborns should be resuscitated and suggest equipment to be used. Use of equipment not specifically recommended in these guidelines has been advocated. We wished to determine how widely this supplementary equipment is used in a geographically defined region. METHODS: Each of the 25 tertiary perinatal centres with on-site deliveries in Australia and New Zealand was surveyed. The questionnaire asked about the use of the following items during delivery room resuscitation: pulse oximetry, exhaled carbon dioxide detection, polyethylene wrapping, oxygen blenders, laryngeal mask and oropharyngeal airways. RESULTS: Data were obtained from all centres. Pulse oximetry is used at 12 (48%) centres. Exhaled CO2 detection is used to confirm endotracheal tube placement at three (12%) of the centres. Polyethylene wrapping is used to prevent heat loss in very-low-birthweight infants at delivery at 11 (44%) centres. Oxygen blenders are used to modify the amount of oxygen delivered at nine (36%) centres. Laryngeal mask airways are infrequently used at two (8%) centres. Oropharyngeal airways are infrequently used at five (20%) centres. CONCLUSION: There is considerable variation in the equipment and techniques used to resuscitate newly born infants. Use of equipment not specifically recommended in international consensus statements is widespread. These are potentially effective tools to improve resuscitation. The evidence supporting their use is, however, limited. Urgent evaluation of their efficacy and safety is required before even more widespread use occurs.
UNLABELLED: Lindner's study of respiratory management of extremely preterm infants, while not providing a definitive answer, demonstrates that many of the smallest infants can be managed in and beyond the delivery room without intubation and without apparent increased early mortality. CONCLUSION: These novel techniques deserve further evaluation.
Positive end expiratory pressure (PEEP) is important for neonatal ventilation but is not considered in guidelines for resuscitation. Our aim was to investigate the effects of PEEP on cardiorespiratory parameters during resuscitation of very premature lambs delivered by hysterotomy at approximately 125 d gestation (term approximately 147 d). Before delivery, they were intubated and lung fluid was drained. Immediately after delivery, they were ventilated with a Dräger Babylog plus ventilator in volume guarantee mode with a tidal volume of 5 mL/kg. Lambs were randomized to receive 0, 4, 8, or 12 cm H(2)O of PEEP. They were ventilated for a 15-min resuscitation period followed by 2 h of stabilization at the same PEEP. Tidal volume, peak inspiratory pressure, PEEP, arterial pressure, oxygen saturation, and blood gases were measured regularly, and respiratory system compliance and alveolar/arterial oxygen differences were calculated. Lambs that received 12 cm H(2)O of PEEP died from pneumothoraces; all others survived without pneumothoraces. Oxygenation was significantly improved by 8 and 12 cm H(2)O of PEEP compared with 0 and 4 cm H(2)O of PEEP. Lambs with 0 PEEP did not oxygenate adequately. The compliance of the respiratory system was significantly higher at 4 and 8 cm H(2)O of PEEP than at 0 PEEP. There were no significant differences in partial pressure of carbon dioxide in arterial blood between groups. Arterial pressure was highest with 8 cm H(2)O of PEEP, and there was no cardiorespiratory compromise at any level of PEEP. Applying PEEP during resuscitation of very premature infants might be advantageous and merits further investigation.
Twenty-six infants with hypoxic-ischemic encephalopathy (HIE) were randomized to normothermia or to systemic hypothermia. The hypothermia group had less cortical gray matter signal abnormality on magnetic resonance imaging (MRI) (1/12 vs 7/14 infants in the normothermic group; P = .036), which may indicate differing regional benefit from systemic hypothermia.