Respiratory function monitoring during early resuscitation and prediction of outcomes in prematurely born infants

OBJECTIVES

Over the last decade, there has been increased use of end-tidal carbon dioxide (ETCO2) and oxygen saturation (SpO2) monitoring during resuscitation of prematurely born infants in the delivery suite. Our objectives were to test the hypotheses that low end-tidal carbon dioxide (ETCO2) levels, low oxygen saturations (SpO2) and high expiratory tidal volumes (VTE) during the early stages of resuscitation would be associated with adverse outcomes in preterm infants.

METHODS

Respiratory recordings made in the first 10 min of resuscitation in the delivery suite of 60 infants, median GA 27 (interquartile range 25-29) weeks were analysed. The results were compared of infants who did or did not die or did or did not develop intracerebral haemorrhage (ICH) or bronchopulmonary dysplasia (BPD).

RESULTS

Twenty-five infants (42%) developed an ICH and 23 (47%) BPD; 11 (18%) died. ETCO2 at approximately 5 min after birth was lower in infants who developed an ICH, this remained significant after adjusting for gestational age, coagulopathy and chorioamnionitis (p=0.03). ETCO2 levels were lower in infants who developed ICH or died compared to those that survived without ICH, which remained significant after adjustment for gestational age, Apgar score at 10 min, chorioamnionitis and coagulopathy (p=0.004). SpO2 at approximately 5 min was lower in the infants who died compared to those who survived which remained significant after adjusting for the 5-min Apgar score and chorioamnionitis (p=0.021).

CONCLUSIONS

ETCO2 and SpO2 levels during early resuscitation in the delivery suite were associated with adverse outcomes.

Ventilatory response to added dead space in infants exposed to second-hand smoke in pregnancy

Maternal cigarette smoking in pregnancy can adversely affect infant respiratory control. In utero nicotine exposure has been shown to blunt the infant ventilatory response to hypercapnia, which could increase the risk of sudden infant death syndrome. The potential impact of maternal second-hand smoke exposure, however, has not yet been determined. The aim of this study was to assess ventilatory response to added dead-space (inducing hypercapnia) in infants with second-hand smoke exposure during pregnancy, in infants whose mothers smoked and in controls (non-smoke exposed). Infants breathed through a face mask and specialised "tube-breathing" circuit, incorporating a dead space of 4.4 ml/kg body weight. The maximum minute ventilation (MMV) during added dead space breathing was determined and the time taken to achieve 63% of the MMV calculated (the time constant (TC) of the response). Infants were studied on the postnatal ward prior to discharge home. Thirty infants (ten in each group) were studied with a median gestational age of 39 [range 37-41] weeks, birthweight of 3.1 [2.2-4.0] kg, and postnatal age of 33 (21-62) h. The infants whose mothers had second-hand smoke exposure (median TC 42 s, p = 0.001), and the infants of cigarette smoking mothers (median TC 37 s, p = 0.002) had longer time constants than the controls (median TC 29 s). There was no significant difference between the TC of the infants whose mothers had second-hand smoke exposure and those whose mothers smoked (p = 0.112).    Conclusion: Second-hand smoke exposure during pregnancy was associated with a delayed newborn ventilatory response. What is Known: • Maternal cigarette smoking in pregnancy can adversely affect infant respiratory control. • The potential impact of maternal second-hand smoke exposure, however, has not yet been determined. What is New: • We have assessed the ventilatory response to added dead-space (inducing hypercapnia) in newborns with second-hand smoke exposure during pregnancy, in infants whose mothers smoked, and in controls (non-smoke exposed). • Maternal second-hand smoke exposure, as well as maternal smoking, during pregnancy was associated with a delayed newborn ventilatory response.

Tidal volume monitoring during initial resuscitation of extremely prematurely born infants

Background Airway obstruction can occur during facemask (FM) resuscitation of preterm infants at birth. Intubation bypasses any upper airway obstruction. Thus, it would be expected that the occurrence of low expiratory tidal volumes (VTes) would be less in infants resuscitated via an endotracheal tube (ETT) rather than via an FM. Our aim was to test this hypothesis. Methods Analysis was undertaken of respiratory function monitoring traces made during initial resuscitation in the delivery suite to determine the peak inflating pressure (PIP), positive end expiratory pressure (PEEP), the VTe and maximum exhaled carbon dioxide (ETCO2) levels and the number of inflations with a low VTe (less than 2.2 mL/kg). Results Eighteen infants were resuscitated via an ETT and 11 via an FM, all born at less than 29 weeks of gestation. Similar inflation pressures were used in both groups (17.2 vs. 18.8 cmH2O, P = 0.67). The proportion of infants with a low median VTe (P = 0.6) and the proportion of inflations with a low VTe were similar in the groups (P = 0.10), as was the lung compliance (P = 0.67). Infants with the lowest VTe had the stiffest lungs (P < 0.001). Conclusion Respiratory function monitoring during initial resuscitation can objectively identify infants who may require escalation of inflation pressures.

Detection of exhaled carbon dioxide following intubation during resuscitation at delivery

OBJECTIVES

End tidal carbon dioxide (ETCO₂) monitoring can facilitate identification of successful intubation. The aims of this study were to determine the time to detect ETCO₂ following intubation during resuscitation of infants born prematurely and whether it differed according to maturity at birth or the Apgar scores (as a measure of the infant's condition after birth).

DESIGN

Analysis of recordings of respiratory function monitoring.

SETTING

Two tertiary perinatal centres.

PATIENTS

Sixty-four infants, with median gestational age of 27 (range 23-34)weeks.

INTERVENTIONS

Respiratory function monitoring during resuscitation in the delivery suite.

MAIN OUTCOME MEASURES

The time following intubation for ETCO₂ levels to be initially detected and to reach 4 mm Hg and 15 mm Hg.

RESULTS

The median time for initial detection of ETCO₂ following intubation was 3.7 (range 0-44) s, which was significantly shorter than the median time for ETCO₂ to reach 4 mm Hg (5.3 (range 0-727) s) and to reach 15 mm Hg (8.1 (range 0-827) s) (both P<0.001). There were significant correlations between the time for ETCO₂ to reach 4 mm Hg (r=-0.44, P>0.001) and 15 mm Hg (r=-0.48, P<0.001) and gestational age but not with the Apgar scores.

CONCLUSIONS

The time for ETCO₂ to be detected following intubation in the delivery suite is variable emphasising the importance of using clinical indicators to assess correct endotracheal tube position in addition to ETCO₂ monitoring. Capnography is likely to detect ETCO₂ faster than colorimetric devices.

Sustained inflations during delivery suite stabilisation in prematurely-born infants - A randomised trial

BACKGROUND

Sustained inflations at initial stabilisation in the delivery suite may reduce the need for intubation and result in a shorter duration of initial ventilation, but have not been compared to routine UK practice.

AIMS

To compare the early efficacy of sustained inflation during stabilisation after delivery to UK practice.

STUDY DESIGN

A randomised trial was performed of a fifteen second sustained inflation compared to five inflations lasting 2 to 3 s, each intervention could be repeated once if no chest rise was apparent. Respiratory function monitoring was undertaken.

SUBJECTS

Infants born prior to 34 weeks of gestation.

OUTCOME MEASURES

The minute volume and maximum end-tidal carbon dioxide level in the first minute after the interventions, the time to the first spontaneous breath after the beginning of stabilisation and the duration of ventilation in the first 48 h.

RESULTS

There were no significant differences in the minute volume or maximum end tidal carbon dioxide level between the groups. Infants in the sustained inflation group made a respiratory effort sooner (median 3.5 (range 0.2-59) versus median 12.8 (range 0.4-119) s, p = 0.001). The sustained inflation group were ventilated for a shorter duration in the first 48 h (median 17 (range 0-48) versus median 32.5 (range 0-48) h, p = 0.025).

CONCLUSIONS

A sustained inflation of 15 s compared to five two to three second inflations during initial stabilisation was associated with a shorter duration of mechanical ventilation in the first 48 h after birth.

Relationship of resuscitation, respiratory function monitoring data and outcomes in preterm infants

Intraventricular haemorrhage (IVH) and bronchopulmonary dysplasia (BPD) are major complications of premature birth. We tested the hypotheses that prematurely born infants who developed an IVH or BPD would have high expiratory tidal volumes (V_TE) (V_TE > 6 ml/kg) and/or low-end tidal carbon dioxide (ETCO₂) levels (ETCO₂ levels < 4.5 kPa) as recorded by respiratory function monitoring or hyperoxia (oxygen saturation (SaO₂) > 95%) during resuscitation in the delivery suite. Seventy infants, median gestational age 27 weeks (range 23-33), were assessed; 31 developed an IVH and 43 developed BPD. Analysis was undertaken of 31,548 inflations. The duration of resuscitation did not differ significantly between the groups. Those who developed an IVH compared to those who did not had a greater number of inflations with a high V_TE and a low ETCO₂, which remained significant after correcting for differences in gestational age and birth weight between groups (p = 0.019). Differences between infants who did and did not develop BPD were not significant after correcting for differences in gestational age and birth weight. There were no significant differences in the duration of hyperoxia between the groups.Conclusions: Avoidance of high tidal volumes and hypocarbia in the delivery suite might reduce IVH development. What is known • Hypocarbia on the neonatal unit is associated with the development of intraventricular haemorrhage (IVH) and bronchopulmonary dysplasia (BPD). What is new • Infants who developed an IVH compared to those who did not had significantly more inflations with high expiratory tidal volumes and low ETCO₂s.

Sustained inflations versus UK standard inflations during initial resuscitation of prematurely born infants in the delivery room: a study protocol for a randomised controlled trial

BACKGROUND

Many infants born at less than 34 weeks of gestational age will require resuscitation in the delivery suite. Yet, different resuscitation techniques are specified in different national guidelines, likely reflecting a limited evidence base. One difference is the length of mechanical inflation initially delivered to infants either via a facemask or endotracheal tube. Some guidelines specify short inflations delivered at rates of 40-60/min, others recommend initial inflations lasting 2-3 s or sustained inflations lasting for ≥ 5 s for initial resuscitation. Research has shown that tidal volumes > 2.2 mL/kg (the anatomical dead space) are seldom generated unless the infant's respiratory effort coincides with an inflation (active inflation). When inflations lasting 1-3 s were used, the time to the first active inflation was inversely proportional to the inflation time. This trial investigates whether a sustained inflation or repeated shorter inflations is more effective in stimulating the first active inflation.

METHODS

This non-blinded, randomised controlled trial performed at a single tertiary neonatal unit is recruiting 40 infants born at < 34 weeks of gestational age. A 15-s sustained inflation is being compared to five repeated inflations of 2-3 s during the resuscitation at delivery. A respiratory function monitor is used to record airway pressure, flow, expiratory tidal volume and end tidal carbon dioxide (ETCO₂) levels. The study is performed as emergency research without prior consent and was approved by the NHS London-Riverside Research Ethics Committee. The primary outcome is the minute volume in the first minute of resuscitation with secondary outcomes of the time to the first active inflation and ETCO₂ level during the first minute of recorded resuscitation.

DISCUSSION

This is the first study to compare a sustained inflation to the current UK practice of five initial inflations of 2-3 s.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02967562 . Registered on 15 November 2016.

Inflation pressures and times during initial resuscitation in preterm infants

BACKGROUND

The optimal combination of inflation pressures and times to produce adequate expiratory tidal volumes during initial resuscitation in prematurely born infants has not been determined. The aim of this study was therefore to assess combinations of inflation pressures and times and the resulting expiratory tidal volume levels using a respiratory function monitor.

METHODS

Sixty-four infants born before 34 weeks of gestation were studied. The infants were divided according to whether the inflation pressure (peak inflation pressure minus positive end expiratory pressure) was < or ≥20 cmH₂ O during the first five inflations delivered by a face mask, and those groups were then subdivided according to whether the inflation time was < or ≥1.5 s.

RESULTS

Inflation pressure ≥20 cmH₂ O compared with lower pressure at both inflation times produced significantly higher expiratory tidal volume. Longer compared with shorter inflation times when the inflation pressure was ≥20 cmH₂ O resulted in no significant difference in expiratory tidal volume. At <20 cmH₂ O inflation pressure, longer inflation time overall resulted in higher end tidal volume, but the majority of infants had a tidal volume less than the anatomical dead space.

CONCLUSIONS

At higher inflation pressure, a longer inflation time was not necessary to increase expiratory tidal volume.

How do the two visual streams interact with each other?

The current consensus divides primate cortical visual processing into two broad networks or "streams" composed of highly interconnected areas (Milner and Goodale 2006, 2008; Goodale 2014). The ventral stream, passing from primary visual cortex (V1) through to inferior parts of the temporal lobe, is considered to mediate the transformation of the contents of the visual signal into the mental furniture that guides memory, recognition and conscious perception. In contrast the dorsal stream, passing from V1 through to various areas in the posterior parietal lobe, is generally considered to mediate the visual guidance of action, primarily in real time. The brain, however, does not work through mutually insulated subsystems, and indeed there are well-documented interconnections between the two streams. Evidence for contributions from ventral stream systems to the dorsal stream comes from human neuropsychological and neuroimaging research, and indicates a crucial role in mediating complex and flexible visuomotor skills. Complementary evidence points to a role for posterior dorsal-stream visual analysis in certain aspects of 3-D perceptual function in the ventral stream. A series of studies of a patient with visual form agnosia has been instrumental in shaping our knowledge of what each stream can achieve in isolation; but it has also helped us to tease apart the relative dependence of parietal visuomotor systems on direct bottom-up visual inputs versus inputs redirected via perceptual systems within the ventral stream.

The first breath during resuscitation of prematurely born infants

BACKGROUND

The first five initial inflation pressures and times during resuscitation of prematurely born infants are frequently lower than those recommended and rarely result in tidal volumes exceeding the anatomical dead space. Greater volumes were produced when the infant was provoked to inspire by an inflation (active inflation).

AIMS

To assess factors associated with a shorter time to the first active inflation.

STUDY DESIGN

Respiratory function monitoring was undertaken during resuscitation, peak inflation pressures (PIP), inflation times and the infant's respiratory activity were simultaneously recorded.

SUBJECTS

Infants with a gestational age<34weeks requiring resuscitation at birth.

OUTCOME MEASURES

The relationships of the PIP and inflation time of the first five inflations and first active inflation to the time to the first active inflation.

RESULTS

Recordings from 47 infants, median gestational age of 29 (23-34) weeks, were analysed. The median PIP of the first five inflations was 27 (range 9-37) cmH2O and inflation time 1.22 (range 0.32-4.08) s. The median PIP of the first active inflation was 25 (range 19-37) cmH2O and inflation time 1.35 (0.35-3.67) s. The median time to the first active inflation was 7 (range 0-50) seconds and was inversely correlated with the PIP (p=0.001) and inflation time (p=0.018) of the first five inflations and the PIP (p=0.001) and inflation time (p=0.008) of the first active inflation.

CONCLUSION

The magnitude of the inflation pressures and times of the first five inflations inversely correlate with the time to the first breath during resuscitation.

Synchronized mechanical ventilation for respiratory support in newborn infants

BACKGROUND

During synchronised mechanical ventilation, positive airway pressure and spontaneous inspiration coincide. If synchronous ventilation is provoked, adequate gas exchange should be achieved at lower peak airway pressures, potentially reducing baro/volutrauma, air leak and bronchopulmonary dysplasia. Synchronous ventilation can potentially be achieved by manipulation of rate and inspiratory time during conventional ventilation and employment of patient-triggered ventilation.

OBJECTIVES

To compare the efficacy of:(i) synchronised mechanical ventilation, delivered as high-frequency positive pressure ventilation (HFPPV) or patient-triggered ventilation (assist control ventilation (ACV) and synchronous intermittent mandatory ventilation (SIMV)), with conventional ventilation or high-frequency oscillation (HFO);(ii) different types of triggered ventilation (ACV, SIMV, pressure-regulated volume control ventilation (PRVCV), SIMV with pressure support (PS) and pressure support ventilation (PSV)).

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review group to search the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 5), MEDLINE via PubMed (1966 to June 5 2016), EMBASE (1980 to June 5 2016), and CINAHL (1982 to June 5 2016). We also searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials.

SELECTION CRITERIA

Randomised or quasi-randomised clinical trials comparing synchronised ventilation delivered as HFPPV to CMV, or ACV/SIMV to CMV or HFO in neonates. Randomised trials comparing different triggered ventilation modes (ACV, SIMV, SIMV plus PS, PRVCV and PSV) in neonates.

DATA COLLECTION AND ANALYSIS

Data were collected regarding clinical outcomes including mortality, air leaks (pneumothorax or pulmonary interstitial emphysema (PIE)), severe intraventricular haemorrhage (grades 3 and 4), bronchopulmonary dysplasia (BPD) (oxygen dependency beyond 28 days), moderate/severe BPD (oxygen/respiratory support dependency beyond 36 weeks' postmenstrual age (PMA) and duration of weaning/ventilation.Eight comparisons were made: (i) HFPPV versus CMV; (ii) ACV/SIMV versus CMV; (iii) SIMV or SIMV + PS versus HFO; iv) ACV versus SIMV; (v) SIMV plus PS versus SIMV; vi) SIMV versus PRVCV; vii) SIMV vs PSV; viii) ACV versus PSV. Data analysis was conducted using relative risk for categorical outcomes, mean difference for outcomes measured on a continuous scale.

MAIN RESULTS

Twenty-two studies are included in this review. The meta-analysis demonstrates that HFPPV compared to CMV was associated with a reduction in the risk of air leak (typical relative risk (RR) for pneumothorax was 0.69, 95% confidence interval (CI) 0.51 to 0.93). ACV/SIMV compared to CMV was associated with a shorter duration of ventilation (mean difference (MD) -38.3 hours, 95% CI -53.90 to -22.69). SIMV or SIMV + PS was associated with a greater risk of moderate/severe BPD compared to HFO (RR 1.33, 95% CI 1.07 to 1.65) and a longer duration of mechanical ventilation compared to HFO (MD 1.89 days, 95% CI 1.04 to 2.74).ACV compared to SIMV was associated with a trend to a shorter duration of weaning (MD -42.38 hours, 95% CI -94.35 to 9.60). Neither HFPPV nor triggered ventilation was associated with a significant reduction in the incidence of BPD. There was a non-significant trend towards a lower mortality rate using HFPPV versus CMV and a non-significant trend towards a higher mortality rate using triggered ventilation versus CMV. No disadvantage of HFPPV or triggered ventilation was noted regarding other outcomes.

AUTHORS' CONCLUSIONS

Compared to conventional ventilation, benefit is demonstrated for both HFPPV and triggered ventilation with regard to a reduction in air leak and a shorter duration of ventilation, respectively. In none of the trials was complex respiratory monitoring undertaken and thus it is not possible to conclude that the mechanism of producing those benefits is by provocation of synchronised ventilation. Triggered ventilation in the form of SIMV ± PS resulted in a greater risk of BPD and duration of ventilation compared to HFO. Optimisation of trigger and ventilator design with respect to respiratory diagnosis is encouraged before embarking on further trials. It is essential that newer forms of triggered ventilation are tested in randomised trials that are adequately powered to assess long-term outcomes before they are incorporated into routine clinical practice.

Synchronized mechanical ventilation for respiratory support in newborn infants

BACKGROUND

During synchronised mechanical ventilation, positive airway pressure and spontaneous inspiration coincide. If synchronous ventilation is provoked, adequate gas exchange should be achieved at lower peak airway pressures, potentially reducing baro/volutrauma, air leak and bronchopulmonary dysplasia. Synchronous ventilation can potentially be achieved by manipulation of rate and inspiratory time during conventional ventilation and employment of patient-triggered ventilation.

OBJECTIVES

To compare the efficacy of:(i) synchronised mechanical ventilation, delivered as high-frequency positive pressure ventilation (HFPPV) or patient-triggered ventilation (assist control ventilation (ACV) and synchronous intermittent mandatory ventilation (SIMV)), with conventional ventilation or high-frequency oscillation (HFO);(ii) different types of triggered ventilation (ACV, SIMV, pressure-regulated volume control ventilation (PRVCV), SIMV with pressure support (PS) and pressure support ventilation (PSV)).

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review group to search the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 5), MEDLINE via PubMed (1966 to June 5 2016), EMBASE (1980 to June 5 2016), and CINAHL (1982 to June 5 2016). We also searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials.

SELECTION CRITERIA

Randomised or quasi-randomised clinical trials comparing synchronised ventilation delivered as HFPPV to CMV, or ACV/SIMV to CMV or HFO in neonates. Randomised trials comparing different triggered ventilation modes (ACV, SIMV, SIMV plus PS, PRVCV and PSV) in neonates.

DATA COLLECTION AND ANALYSIS

Data were collected regarding clinical outcomes including mortality, air leaks (pneumothorax or pulmonary interstitial emphysema (PIE)), severe intraventricular haemorrhage (grades 3 and 4), bronchopulmonary dysplasia (BPD) (oxygen dependency beyond 28 days), moderate/severe BPD (oxygen/respiratory support dependency beyond 36 weeks' postmenstrual age (PMA) and duration of weaning/ventilation.Eight comparisons were made: (i) HFPPV versus CMV; (ii) ACV/SIMV versus CMV; (iii) SIMV or SIMV + PS versus HFO; iv) ACV versus SIMV; (v) SIMV plus PS versus SIMV; vi) SIMV versus PRVCV; vii) SIMV vs PSV; viii) ACV versus PSV. Data analysis was conducted using relative risk for categorical outcomes, mean difference for outcomes measured on a continuous scale.

MAIN RESULTS

Twenty-two studies are included in this review. The meta-analysis demonstrates that HFPPV compared to CMV was associated with a reduction in the risk of air leak (typical relative risk (RR) for pneumothorax was 0.69, 95% confidence interval (CI) 0.51 to 0.93). ACV/SIMV compared to CMV was associated with a shorter duration of ventilation (mean difference (MD) -38.3 hours, 95% CI -53.90 to -22.69). SIMV or SIMV + PS was associated with a greater risk of moderate/severe BPD compared to HFO (RR 1.33, 95% CI 1.07 to 1.65) and a longer duration of mechanical ventilation compared to HFO (MD 1.89 days, 95% CI 1.04 to 2.74).ACV compared to SIMV was associated with a trend to a shorter duration of weaning (MD -42.38 hours, 95% CI -94.35 to 9.60). Neither HFPPV nor triggered ventilation was associated with a significant reduction in the incidence of BPD. There was a non-significant trend towards a lower mortality rate using HFPPV versus CMV and a non-significant trend towards a higher mortality rate using triggered ventilation versus CMV. No disadvantage of HFPPV or triggered ventilation was noted regarding other outcomes.

AUTHORS' CONCLUSIONS

Compared to conventional ventilation, benefit is demonstrated for both HFPPV and triggered ventilation with regard to a reduction in air leak and a shorter duration of ventilation, respectively. In none of the trials was complex respiratory monitoring undertaken and thus it is not possible to conclude that the mechanism of producing those benefits is by provocation of synchronised ventilation. Triggered ventilation in the form of SIMV ± PS resulted in a greater risk of BPD and duration of ventilation compared to HFO. Optimisation of trigger and ventilator design with respect to respiratory diagnosis is encouraged before embarking on further trials. It is essential that newer forms of triggered ventilation are tested in randomised trials that are adequately powered to assess long-term outcomes before they are incorporated into routine clinical practice.

In vitro assessment of the effect of proportional assist ventilation on the work of breathing

During proportional assist ventilation, elastic and resistive unloading can be delivered to reduce the work of breathing (WOB). Our aim was to determine the effects of different levels of elastic and resistive unloading on the WOB in lung models designed to mimic certain neonatal respiratory disorders. Two dynamic lung models were used, one with a compliance of 0.4 ml/cm H2O to mimic an infant with respiratory distress syndrome and one with a resistance of 300 cm H2O/l/s to mimic an infant with bronchopulmonary dypslasia. Pressure volume curves were constructed at each unloading level. Elastic unloading in the low compliance model was highly effective in reducing the WOB measured in the lung model; the effective compliance increased from 0.4 ml/cm H2O at baseline to 4.1 ml/cm H2O at maximum possible elastic unloading (2.0 cm H2O/ml). Maximum possible resistive unloading (200 cm H2O/l/s) in the high-resistance model only reduced the effective resistance from 300 to 204 cm H2O/l/s. At maximum resistive unloading, oscillations appeared in the airway pressure waveform.

CONCLUSION

Our results suggest that elastic unloading will be helpful in respiratory conditions characterised by a low compliance, but resistive unloading as currently delivered is unlikely to be of major clinical benefit.

WHAT IS KNOWN

• During PAV, the ventilator can provide elastic and resistive unloading. What is New: • Elastic unloading was highly effective in reducing the work of breathing. • Maximum resistive unloading only partially reduced the effective resistance.

Proportional assist versus assist control ventilation in premature infants

During proportional assist ventilation (PAV), the applied pressure is servo-controlled based on continuous input from the infant's breathing. In addition, elastic and resistive unloading can be employed to compensate for the abnormalities in the infant's lung mechanics. The aim of this study was to test the hypothesis that in very prematurely born infants remaining ventilated beyond the first week, PAV compared to assist control ventilation (ACV) would be associated with superior oxygenation. A randomised crossover study was undertaken. Infants were studied for 4 hours each on PAV and ACV in random order; at the end of each 4-h period, the oxygenation index (OI) was calculated. Eight infants, median gestational age of 25 (range 24-33) weeks, were studied at a median of 19 (range 10-105) days. It had been intended to study 18 infants but as all the infants had superior oxygenation on PAV (p = 0.0039), the study was terminated after recruitment of eight infants. The median inspired oxygen concentration (p = 0.049), mean airway pressure (p = 0.012) and OI (p = 0.012) were all lower on PAV.

CONCLUSION

These results suggest that PAV compared to ACV is advantageous in improving oxygenation for prematurely born infants with evolving or established BPD.

WHAT IS KNOWN

During proportional assist ventilation (PAV), the applied pressure is servo controlled throughout each spontaneous breath. Elastic and resistive unloading can compensate for the infant's abnormalities in lung mechanics.

WHAT IS NEW

In a randomised crossover study, infants with evolving/established BPD were studied on PAV and ACV each for 4 h. The oxygenation index was significantly lower on PAV in all infants studied.

Prematurely born infants' response to resuscitation via an endotracheal tube or a face mask

BACKGROUND

Prematurely born infants may be resuscitated in the labour suite via a face mask or an endotracheal tube.

AIMS

To assess prematurely born infants' initial responses to resuscitation delivered via an endotracheal tube or a face mask, to determine if the first five inflations via an endotracheal tube produced expired tidal volumes greater than 4.4ml/kg (twice the anatomical dead space) and whether the outcome of initial resuscitation via an endotracheal tube or via a face mask differed according to the first active inflation (the infant's inspiratory effort coinciding with an inflation).

STUDY DESIGN

Prospective observational study.

SUBJECTS

Thirty-five infants (median gestational age 25, range 23-27weeks) requiring resuscitation via an endotracheal tube (n=20) or a face mask (n=15) were studied.

OUTCOME MEASURES

Inflation pressures, inflation times, expiratory tidal volumes, end tidal carbon dioxide (ETCO2) and leak were recorded.

RESULTS

Before the first active inflation, only 27% of infants receiving resuscitation via an endotracheal tube had expiratory volumes greater than 4.4ml/kg. During, both endotracheal and face mask initial resuscitations, during the first active inflation the expired tidal volumes (7.7ml/kg, 5.2ml/kg) and ETCO2 levels (4.8kPa, 3.2kPa) were significantly higher than during the inflations before the first active inflation (2.8ml/kg, 1.6ml/kg; 0.36kPa, 0.2kPa respectively) (all p<0.001).

CONCLUSIONS

Initial resuscitation via an endotracheal tube using currently recommended pressures, rarely produced adequate tidal volumes. Resuscitation via an endotracheal tube or a face mask was most effective when the infant's inspiratory effort coincided with an inflation.

Crossover study of proportional assist versus assist control ventilation

OBJECTIVE

To test the hypothesis that in very prematurely born infants remaining ventilated beyond the first week, proportional assist ventilation (PAV) compared with assist control ventilation (ACV) would be associated with reduced work of breathing, increased respiratory muscle strength and less ventilator-infant asynchrony which would be associated with improved oxygenation.

DESIGN

Randomised crossover study.

SETTING

Tertiary neonatal unit.

PATIENTS

12 infants with a median gestational age of 25 (range 24-26) weeks were studied at a median of 43 (range 8-86) days.

INTERVENTIONS

Infants were studied for 1 h each on PAV and ACV in random order.

MAIN OUTCOME MEASURES

At the end of each hour, the work of breathing (assessed by measuring the diaphragmatic pressure time product), thoracoabdominal asynchrony and respiratory muscle strength (maximal inspiratory pressure, maximal expiratory pressure (Pemax) and maximal transdiaphragmatic pressure (Pdimax)) were assessed. Blood gas analysis was performed and the oxygenation index (OI) calculated.

RESULTS

After 1 h on PAV compared with 1 h on ACV, the median OI (5.55 (range 5-11) vs 10.10 (range 7-16), p=0.002) and PTP levels were lower (217 (range 59-556) cm H2O.s/min vs 309 (range 55-544) cm H2O.s/min, p=0.005), while Pdimax (44.26 (range 21-66) cm H2O vs 37.9 (range 19-45) cm H2O, p=0.002) and Pemax (25.6 (range 6.5-42) cm H2O vs 15.9 (range 3-35) cm H2O levels p=0.010) were higher.

CONCLUSIONS

These results suggest that PAV compared with ACV may have physiological advantages for prematurely born infants who remain ventilated after the first week after birth.

Sleeping position and responses to a carbon dioxide challenge in convalescent prematurely born infants studied post-term

OBJECTIVES

To test the hypothesis that the ventilatory response to a carbon dioxide (CO2) challenge would be lower in the prone compared to the supine position in prematurely born infants studied post-term. To determine whether there were postural-related differences in respiratory drive, respiratory muscle strength, thoracoabdominal synchrony and/or lung volume.

DESIGN

Prospective cohort study.

SETTING

Tertiary neonatal unit.

PATIENTS

Eighteen infants (median gestational age 31 (range 22-32) weeks) were studied at a median of 5 (range 2-11) weeks post-term.

INTERVENTIONS

The ventilatory responses to three added carbon dioxide (CO2) levels (0% baseline, 2% and 4%) were assessed in the prone and supine positions.

MAIN OUTCOME MEASURES

The airway pressure change after the first 100 ms of an occluded inspiration (P0.1) (respiratory drive) and the maximum inspiratory pressure during crying with an occluded airway (Pimax) (respiratory muscle strength) were measured. The P0.1/Pimax ratio at each CO2 level and slope of the P0.1/Pimax response were calculated.

RESULTS

The mean P0.1 (p<0.05) and P0.1/Pimax (p<0.05) were higher and the functional residual capacity (p=0.031) lower in the supine compared to the prone position. The mean P0.1 and P0.1/Pimax increased independently of position as the percentage CO2 increased (p<0.001). There was no tendency for the differences in P0.1 and P0.1/Pimax between the prone and supine position to vary by CO2 level.

CONCLUSIONS

Convalescent, prematurely born infants studied post-term have a reduced respiratory drive, but not a lower ventilatory response to a CO2 challenge, in the prone compared to the supine position.

The nature and limits of orientation and pattern processing supporting visuomotor control in a visual form agnosic

Abstract We have previously reported that a patient (DF) with visual form agnosia shows accurate guidance of hand and finger movements with respect to the size, orientation, and shape of the objects to which her movements are directed. Despite this, she is unable to indicate any knowledge about these object properties. In the present study, we investigated the extent to which DF is able to use visual shape or pattern to guide her hand movements. In the first experiment, we found that when presented with a stimulus aperture cut in the shape of the letter T, DF was able to guide a T-shaped form into it on about half of the trials, across a range of different stimulus orientations. On the remaining trials, her responses were almost always perpendicular to the correct Orientation. Thus, the visual information guiding the rotation of DF's hand appears to be limited to a single orientation. In other words, the visuomotor transformations mediating her hand rotation appear to be unable to combine the orientations of the stem and the top of the T, although they are sensitive to the orientation of the element(s) that comprise the T. In a second experiment, we examined her ability to use different sources of visual information to guide her hand rotation. In this experiment, DF was required to guide the leading edge of a hand-held card onto a rectangular target positioned at dHerent orientations on a flat surface. Here the orientation of her hand was determined primarily by the predominant orientation of the luminance edge elements present in the stimulus, rather than by information about orientation that was conveyed by nonluminance boundaries. Little evidence was found for an ability to use contour boundaries defined by Gestalt principles of grouping (good continuation or similarity) or "nonaccidental" image properties (colinearity) to guide her movements. We have argued elsewhere that the dorsal visual pathway from occipital to parietal cortex may underlie these preserved visuomotor skills in DF. If so, the limitations in her ability to use different kinds of "pattern" information to guide her hand rotation suggest that such information may need to be transmitted from the ventral visual stream to these parietal areas to enable the full range of prehensive acts in the intact individual.

Neuromuscular blockade and lung function during resuscitation of infants with congenital diaphragmatic hernia

BACKGROUND

There is no consensus or evidence as to whether a neuromuscular blocking agent should be used during the initial resuscitation of infants with congenital diaphragmatic hernia (CDH) in the labour ward.

OBJECTIVE

To determine if administration of a neuromuscular blocking agent affected the lung function of infants with CDH during their initial resuscitation in the labour ward.

METHODS

Fifteen infants with CDH were studied (median gestational age 38 weeks, range 34-41; birth weight 2,790 g, range 1,780-3,976). Six infants had undergone feto-endotracheal occlusion (FETO). Flow, airway pressure, tidal volume and dynamic lung compliance changes were recorded using a respiratory function monitor (NM3, Respironics). Twenty inflations immediately before, immediately after and 5 min after administration of a neuromuscular blocking agent (pancuronium bromide) were analysed.

RESULTS

The median dynamic lung compliance of the 15 infants was 0.22 ml/cm H2O/kg (range 0.1-0.4) before and 0.16 ml/cm H2O/kg (range 0.1-0.3) immediately after pancuronium bromide administration (p < 0.001) and remained at a similar low level 5 min after pancuronium bromide administration. The FETO compared to the non-FETO infants had a lower median dynamic compliance both before (p < 0.0001) and 5 min after pancuronium administration (p < 0.001) and required significantly longer durations of ventilation (p = 0.004), supplementary oxygen (p = 0.003) and hospitalisation (p = 0.007).

CONCLUSIONS

Infants with CDH, particularly those who have undergone FETO, have a low lung compliance at birth, and this is further reduced by administration of a neuromuscular blocking agent.

Respiratory syncytial virus infection and chronic respiratory morbidity - is there a functional or genetic predisposition?

A systematic literature review has been undertaken. Respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) in infancy is associated with chronic respiratory morbidity. Premorbid abnormal lung function may predispose to RVS LRTI in prematurely born infants.

CONCLUSION

  Single-nucleotide polymorphisms in genes coding for IL-8, IL-19, IL-20, IL-13 mannose-binding lectin, IFNG and a RANTES polymorphism have been associated with subsequent wheeze following RSV LRTI in term-born infants.

Lung function at follow-up of infants with surgically correctable anomalies

Infants with congenital diaphragmatic hernia (CDH) or anterior wall defects (AWD) can suffer abnormal antenatal lung growth, the risk, however, may be greater for CDH infants. The objectives of this study were to test the hypothesis that following surgical correction, CDH infants would have worse lung function at follow-up than AWD infants and to determine whether fetal lung volume (FLV) results correlated with the lung function results at follow-up. Thirteen infants with CDH and 13 infants with AWD had lung function measurements at a median age of 11 (range 6-24) months; 17 of the infants had had their FLV assessed. Lung function was assessed by plethysmographic measurement of lung volume (FRCpleth) and airway resistance (Raw). In addition, functional residual capacity was assessed by a helium gas dilution technique (FRCHe); tidal breathing parameters (T(PTEF) :Te) and compliance and resistance of the respiratory system (Crs and Rrs, respectively) were also determined. FLV was assessed using three-dimensional (3D) ultrasound and virtual organ computer aided analysis. The CDH compared to the AWD infants had a higher median FRCpleth (41 ml/kg vs. 37 ml/kg, P = 0.043) and a lower median Crs (1.45 ml/cm H(2) O/kg vs. 2.78 ml/cm H(2) O/kg, P = 0.041). FRCpleth results correlated significantly with FLV results (r = 0.721, P < 0.001). In conclusion, infants with CDH had significantly different lung function at follow-up than AWD infants. Our findings suggest FLV results may predict lung function abnormalities at follow-up in infants with surgically correctable anomalies.

End tidal carbon dioxide levels during the resuscitation of prematurely born infants

BACKGROUND

Successful resuscitation of prematurely born infants is dependent on achieving adequate alveolar ventilation and vasodilation of the pulmonary vascular bed. Elevation of end-tidal carbon dioxide (ETCO(2)) levels may indicate pulmonary vasodilation.

AIMS

This research aims to study the temporal changes in ETCO(2) levels and the infant's respiratory efforts during face mask resuscitation in the labour suite, and to determine if the infant's first inspiratory effort was associated with a rise in the ETCO(2) levels, suggesting pulmonary vasodilation had occurred.

STUDY DESIGN

This study is an observational one.

SUBJECTS

The subjects of the study are forty infants with a median gestational age of 30 weeks (range 23-34).

OUTCOME MEASURES

Inflation pressures, expiratory tidal volumes and ETCO(2) levels were measured.

RESULTS

The median expiratory tidal volume of inflations prior to the onset of the infant's respiratory efforts (passive inflations) was lower than that of the inflation associated with the first inspiratory effort (active inflation) (1.8 (range 0.1-7.3) versus 6.3 ml/kg (range 1.9-18.4), p<0.001), as were the median ETCO(2) levels (0.3 (range 0.1-2.1) versus 3.4 kPa (0.4-11.5), p<0.001). The median expiratory tidal volume (4.5 ml/kg (range 0.5-18.3)) and ETCO(2) level (2.2 kPa (range 0.3-9.3)) of the two passive inflations following the first active inflation were also higher than the median expiratory tidal volume and ETCO(2) levels of the previous passive inflations (p<0.001, p<0.0001 respectively).

CONCLUSION

These results suggest that during face mask resuscitation, improved carbon dioxide elimination, likely due to pulmonary vasodilation, occurred with the onset of the infant's respiratory efforts.

Volume-targeted ventilation in infants born at or near term

OBJECTIVES

To determine the impact of different volume-targeted (VT) levels during volume-targeted ventilation (VTV) on the work of breathing (WOB) of infants born at or near term and to investigate whether a level of VT reduced the WOB below that experienced on respiratory support without VT.

DESIGN

Prospective crossover study.

PATIENTS

Sixteen infants, median gestational age of 38 (range 34-41) weeks, birth weight of 3.1 (range 1.5-4.1) kg and postnatal age of 5 (range 2-17) days were studied. The infants were receiving time-cycled, pressure-limited ventilation in a continuous mandatory or in a triggered mode.

INTERVENTIONS

The infants were studied first without VT (baseline) and then at VT levels of 4, 5 and 6 ml/kg delivered in a random order. After each VT level, the infants were returned to baseline.

MAIN OUTCOME MEASURE

The WOB was assessed by measuring the transdiaphragmatic pressure-time product (PTPdi).

RESULTS

One infant became apnoeic at VT of 6 ml/kg. At a VT level of 4 ml/kg, four infants were making such vigorous respiratory efforts that no inflations were delivered. The median PTPdi was higher at a VT level of 4 ml/kg than at 5 ml/kg (p<0.01) or 6 ml/kg (p<0.001). Only at a VT level of 6 ml/kg was the median PTPdi lower than that at baseline (p<0.01).

CONCLUSION

Low VT levels (4 ml/kg) during VTV increase the WOB in ventilated infants born at term or near term. The results suggest that a VT level of 6 ml/kg could be used to reduce the WOB.

The first five inflations during resuscitation of prematurely born infants

OBJECTIVE

To study the first five inflations during the resuscitation of prematurely born infants and whether the infant's inspiratory efforts influenced the expired tidal volume.

DESIGN

Prospective observational study.

SETTING

Two tertiary perinatal centres.

PATIENTS

Thirty infants, median gestational age 30 (23-34) weeks.

INTERVENTIONS

The first five inflations delivered via a face mask and t-piece device were examined using respiratory function monitoring.

MAIN OUTCOME MEASURES

Inflation pressures, inflation times and expiratory volumes were recorded and comparison made of inflations during which the infant made an inspiratory effort (active inflation) or did not (passive inflation).

RESULTS

Overall, the median expired tidal volume was 2.5 (0-19.8) ml/kg and was lower for passive (median 2.1 ml/kg, range 0-19.8 ml/kg) compared with active (median 5.6 ml/kg, range 1.2-12.2 ml/kg) inflations (ratio of geometric means 1.85, 95% CI 1.18 to 28%) (p=0.007). Overall, the median face mask leak was 54.5% and was lower for active (34.5%) compared with passive (60.7%) inflations (mean difference in % leak: 12.4%, 95% CI 0.9 to 24%) (p=0.0354). There was a significant positive correlation between the expiratory volumes and the inflation pressures (R2 between subjects 0.19, p=0.04) and a negative correlation between the expiratory tidal volumes and the face mask leaks (R2 between subjects=0.051, p<0.001), but there was no significant correlation between the inflation times and the expiratory tidal volumes.

CONCLUSION

The expired tidal volume, inflation pressures and times during the first five inflations during resuscitation were variable. The expired tidal volumes were significantly greater if the infant inspired during the inflation.

Inflation times during resuscitation of preterm infants

Data on the effects of a prolonged inflation time during the resuscitation of very prematurely born infants are limited; one study showed no effect, and in another, although lower bronchopulmonary dysplasia (BPD) rates were seen, that effect could have been due to the prolonged inflation time, the positive end expiratory pressure applied or the combination of the two. The aims of our study were to assess the length of inflation times used during face mask and t-piece resuscitation of prematurely born infants in the labour suite and determine whether prolonged inflations led to longer inflation flow times. A respiration monitor (NM3 respiratory profile monitor) was used to record flow, airway pressure and tidal volume changes. The first five inflations for each baby were analysed. Forty prematurely born infants (median gestational age 30, range 26-32 weeks) were examined. Their median inflation pressure was 17.6 (range 12.2-27.4) cm H2O, inflation time 0.89 (range 0.33-2.92) s, expiratory tidal volume 1.01 (range 0.02-11.41) ml/kg and inflation flow time 0.11 (range 0.04-0.54) s. There was no significant relationship between the inflation time and the inflation flow time, but there was a significant relationship between the inflation pressure and the inflation flow time (p = 0.024).

CONCLUSION

These results suggest that prolonging inflation times during face mask resuscitation of prematurely born infants would not improve ventilation as prolonged inflation did not lead to longer inflation flow times.

Is visual processing in the dorsal stream accessible to consciousness?

There are two highly interconnected clusters of visually responsive areas in the primate cortex. These two clusters have relatively few interconnections with each other, though those interconnections are undoubtedly important. One of the two main clusters (the dorsal stream) links the primary visual cortex (V1) to superior regions of the occipito-parietal cortex, while the other (the ventral stream) links V1 to inferior regions of the occipito-temporal cortex. According to our current understanding of the functional anatomy of these two systems, the dorsal stream's principal role is to provide real-time 'bottom-up' visual guidance of our movements online. In contrast, the ventral stream, in conjunction with top-down information from visual and semantic memory, provides perceptual representations that can serve recognition, visual thought, planning and memory offline. In recent years, this interpretation, initially based chiefly on studies of non-human primates and human neurological patients, has been well supported by functional MRI studies in humans. This perspective presents empirical evidence for the contention that the dorsal stream governs the visual control of movement without the intervention of visual awareness.

Lung function abnormalities in infants developing bronchopulmonary dysplasia

OBJECTIVE

To determine if infants developing bronchopulmonary dysplasia (BPD), particularly mild BPD, initially had minimal lung function abnormalities, which then worsened throughout the neonatal period.

DESIGN

Prospective observational study.

SETTING

Tertiary neonatal intensive care unit.

PATIENTS

74 infants with a median gestational age of 30 weeks (24-32) and birth weight of 1200 g (474-2000) were studied; 35 had no BPD, 12 developed mild BPD and 23 developed moderate/severe BPD.

INTERVENTIONS

BPD was diagnosed in infants who were oxygen dependent beyond 28 days after birth.

MAIN OUTCOME MEASURES

Lung function was assessed by measurement of functional residual capacity (FRC) by helium gas dilution and compliance and resistance of the respiratory system. Measurements were attempted on days 3, 5, 7, 14, 21 and 28.

RESULTS

Infants developing BPD, particularly moderate/severe BPD, had lower mean FRC (p=0.009) and mean compliance (p=0.005) throughout the 28-day period than those who did not develop BPD. Lung function improved over the neonatal period in all three groups, but the rate of improvement in FRC (p=0.004) and compliance (p=0.002) results over the first 28 days varied by BPD status, being greatest in infants developing moderate/severe BPD (all p values <0.05).

CONCLUSIONS

Overall, in infants who did and did not develop BPD, lung function improved throughout the neonatal period. Infants with more severe initial lung disease were more likely to develop moderate/severe BPD.

Chorioamnionitis, lung function and bronchopulmonary dysplasia in prematurely born infants

OBJECTIVE

To determine whether prematurely born infants exposed to chorioamnionitis compared to those not exposed have poorer lung function and are more likely to develop severe bronchopulmonary dysplasia (BPD).

DESIGN

Results were analysed from consecutive infants born at <33 weeks gestation with placental histology results and lung function measurement results on days 2 and/or 7 after birth and/or at 36 weeks postmenstrual age (PMA).

SETTING

Tertiary neonatal intensive care unit.

PATIENTS

120 infants with a median gestational age of 29 (range 23-32) weeks were studied, 76 (63%) developed BPD and 41 (34%) had been exposed to chorioamnionitis and/or funisitis.

INTERVENTIONS

Chorioamnionitis was diagnosed histologically.

MAIN OUTCOME MEASURES

Lung function was assessed by measurement of lung volume and compliance and resistance of the respiratory system. If the infants remained oxygen dependent beyond 28 days, they were diagnosed at 36 weeks PMA to have mild BPD (no longer oxygen dependent), moderate BPD (required less than 30% oxygen) or severe BPD (required more than 30% oxygen and/or positive pressure support).

RESULTS

No significant differences were found in the lung function results between the chorioamnionitis and non-chorioamnionitis groups at any postnatal age. There was no significant relationship between chorioamnionitis and the occurrence or severity of BPD. Regression analysis demonstrated BPD was significantly related only to birth weight, gestational age and use of surfactant.

CONCLUSION

In prematurely born infants, routinely exposed to antenatal steroids and postnatal surfactant, chorioamnionitis was not associated with worse lung function or more severe BPD.

Ventilatory response to added dead space and position in preterm infants at high risk age for SIDS

OBJECTIVE

The vulnerability of prematurely born infants to sudden infant death syndrome (SIDS) in the prone position might be explained by a reduced ability to respond to a stress, such as hypercarbia, in that position; our objective, therefore, was to further explore the influence of position on the response to a stress.

WORKING HYPOTHESIS

The ability of prematurely born infants to respond to added dead space in the prone compared to the supine position would be impaired at the high risk age for SIDS.

PATIENTS

Twenty infants, median gestational age of 30 (range 24-32) weeks were studied at a median postmenstrual age (PMA) of 45 weeks. In addition, comparisons were made to the results of 25 infants studied at 36 weeks PMA.

METHODOLOGY

Infants were studied supine and prone. Breath by breath minute volume was measured at baseline and after a dead space was incorporated into the breathing circuit; the time constant of the response was calculated. The pressure generated in the first 100 msec of an occlusion (P0.1 ), the maximum inspiratory pressure during an airway occlusion and functional residual capacity (FRC) were also measured in both positions.

RESULTS

The median time constant was longer (38 (range 15-85) vs. 26 (range 2-40) sec (P = 0.002)). P0.1 lower (P = 0.003) and FRC higher (P = 0.031) in the prone compared to the supine position. In the prone position, the time constant correlated with PMA (P = 0.047), that is, the rate of response to added dead space was significantly damped with increasing postnatal age up to the critical age for SIDS.

CONCLUSIONS

The dampened rate of response to added dead space in the prone compared to the supine position lends support to the hypothesis that a poorer response to a stress may contribute to prematurely born infants increased risk of SIDS in the prone position.

In vitro assessment of proportional assist ventilation

OBJECTIVE

During proportional assist ventilation (PAV) the timing and frequency of inflations are controlled by the patient and the patient's work of breathing may be relieved by elastic and/or resistive unloading. It is important and the authors' objective to determine whether ventilators delivering PAV function well in situations mimicking neonatal respiratory conditions.

DESIGN

In vitro laboratory study.

SETTING

Tertiary neonatal ICU.

INTERVENTIONS

Dynamic lung models were developed which mimicked respiratory distress syndrome, bronchopulmonary dysplasia and meconium aspiration syndrome to assess the performance of the Stephanie neonatal ventilator.

MAIN OUTCOME MEASURES

The effects of elastic and resistive unloading on inflation pressures and airway pressure wave forms and whether increasing unloading was matched by an 'inspiratory' load reduction.

RESULTS

During unloading, delivered pressures were between 1 and 4 cm H(2)O above those expected. Oscillations appeared in the airway pressure wave form when the elastic unloading was greater than 0.5 cm H(2)O/ml with a low resistance model and 1.5 cm H(2)O/ml with a high resistance model and when the resistive unloading was greater than 100 cm H(2)O/l/s. There was a time lag in the delivery of airway pressure of at least 60 ms, but increasing unloading was matched by an inspiratory load reduction.

CONCLUSIONS

During PAV, unloading does reduce inspiratory load, but there are wave form abnormalities and a time lag in delivery of the inflation pressure. The impact of these problems needs careful evaluation in the clinical setting.

Separate processing of texture and form in the ventral stream: evidence from FMRI and visual agnosia

Real-life visual object recognition requires the processing of more than just geometric (shape, size, and orientation) properties. Surface properties such as color and texture are equally important, particularly for providing information about the material properties of objects. Recent neuroimaging research suggests that geometric and surface properties are dealt with separately within the lateral occipital cortex (LOC) and the collateral sulcus (CoS), respectively. Here we compared objects that differed either in aspect ratio or in surface texture only, keeping all other visual properties constant. Results on brain-intact participants confirmed that surface texture activates an area in the posterior CoS, quite distinct from the area activated by shape within LOC. We also tested 2 patients with visual object agnosia, one of whom (DF) performed well on the texture task but at chance on the shape task, whereas the other (MS) showed the converse pattern. This behavioral double dissociation was matched by a parallel neuroimaging dissociation, with activation in CoS but not LOC in patient DF and activation in LOC but not CoS in patient MS. These data provide presumptive evidence that the areas respectively activated by shape and texture play a causally necessary role in the perceptual discrimination of these features.

Relation of exhaled nitric oxide levels to development of bronchopulmonary dysplasia

OBJECTIVE

To test the hypothesis that exhaled nitric oxide levels on day 28 and changes in exhaled nitric oxide levels in the neonatal period would differ according to whether infants developed bronchopulmonary dysplasia (BPD) and its severity.

DESIGN

Prospective observational study.

SETTING

Tertiary neonatal intensive care unit.

PATIENTS

80 infants (median gestational age 28, range 24-32 weeks), 46 of whom developed BPD.

INTERVENTIONS

Exhaled nitric oxide measurements were attempted on days 3, 5, 7, 14, 21 and 28.

MAIN OUTCOME MEASURES

BPD (oxygen dependency at 28 days), mild BPD (oxygen dependent at 28 days, but not 36 weeks postmenstrual age (PMA)); moderate BPD (oxygen dependent at 36 weeks PMA) and severe BPD (respiratory support dependent at 36 weeks PMA).

RESULTS

On day 28, exhaled nitric oxide levels were higher in infants with BPD compared to those without BPD (p<0.001) and there was a linear trend in exhaled nitric oxide results as BPD severity increased (p = 0.006). No significances in the change in exhaled nitric oxide levels over the neonatal period were found between the four groups.

CONCLUSION

Exhaled nitric oxide levels are raised in infants with established BPD, particularly in those developing moderate or severe BPD, and may reflect ongoing inflammation.

Position and ventilatory response to added dead space in prematurely born infants

OBJECTIVES

Prematurely born infants are at increased risk of sudden infant death syndrome (SIDS) if slept prone.

WORKING HYPOTHESIS

Prematurely born infants would have an impaired response to an added dead space and lower respiratory muscle strength in the prone compared to the supine position.

STUDY DESIGN

Prospective study. PATIENT-SUBJECT SELECTION: Twenty-five infants, median gestational age of 30 (range 26-32) weeks.

METHODOLOGY

The infants were studied supine and prone at a median of 36 weeks postmenstrual age. Breath by breath minute volume was measured at baseline and after a dead space was incorporated into the breathing circuit; the time constant of the response was calculated. The maximum inspiratory occlusion pressure generated (MIOP) and the pressure generated over the first 100 msec (P(0.1)) during airway occlusion were assessed.

RESULTS

The median time constant was longer (26 (range 8-106) sec vs. 22 (range 6-92) sec (P = 0.045)) and the median MIOP (P = 0.001) and P(0.1) (P = 0.003) were lower in the prone compared to the supine position.

CONCLUSION

Prematurely born infants have a dampened response to tube breathing and reduced respiratory muscle strength in the prone compared to the supine position, which may contribute to their increased vulnerability to SIDS in the prone position.

Randomized study of percutaneous endoscopic gastrostomy versus nasogastric tubes for enteral feeding in head and neck cancer patients treated with (chemo)radiation

Percutaneous endoscopic gastrostomy (PEG) tubes have largely replaced nasogastric tubes (NGT) for nutritional support of patients with head and neck cancer undergoing curative (chemo)radiotherapy without any good scientific basis. A randomized trial was conducted to compare PEG tubes and NGT in terms of nutritional outcomes, complications, patient satisfaction and cost. The study was closed early because of poor accrual, predominantly due to patients' reluctance to be randomized. There were 33 patients eligible for analysis. Nutritional support with both tubes was good. There were no significant differences in overall complication rates, chest infection rates or in patients' assessment of their overall quality of life. The cost of a PEG tube was 10 times that of an NGT. The duration of use of PEG tubes was significantly longer, a median 139 days compared with a median 66 days for NGT. We found no evidence to support the routine use of PEG tubes over NGT in this patient group.

A phase I trial of Capecitabine+Gemcitabine with radical radiation for locally advanced pancreatic cancer

Standard chemoradiotherapy with infusional 5FU for locally advanced pancreatic cancer (LAPC) has limited efficacy in this disease. The combination of Capecitabine (Cap) and Gemcitabine (Gem) are synergistic and are potent radiosensitisers. The aim of this phase I trial was thus to determine the highest administered dose of the Cap plus Gem combination with radical radiotherapy (RT) for LAPC. Patients had LAPC, adequate organ function, ECOG PS 0–1. During RT, Gem was escalated from 20–50 mg m⁻² day⁻¹ (twice per week), and Cap 800–2000 mg m⁻² day⁻¹ (b.i.d, days 1–5 of each week). Radiotherapy 50.4 Gy/28 fractions/5.5 weeks, using 3D-conformal techniques. Three patients were entered to each dose level (DL). Dose-limiting toxicity(s) (DLTs) were based on treatment-related toxicities. Twenty patients were accrued. Dose level (DL) 1: Cap/Gem; 800/20 mg m⁻² day⁻¹ (3 patients), DL2: 1000/20 (12 patients), DL3: 1300/30 (5 patients). Dose-limiting toxicities were observed in DL3; grade 3 dehydration (1 patient) and grade 3 diarrhoea and dehydration (1 patient). Dose level 2 was the recommend phase 2 dose. Disease control rate was 75%: PR=15%, SD=60%. Median overall survival was 11.2 months. The addition of Cap and Gem to radical RT was feasible and active and achieved at relatively low doses.

Synchronized mechanical ventilation for respiratory support in newborn infants

BACKGROUND

During synchronized mechanical ventilation, positive airway pressure and spontaneous inspiration coincide. If synchronous ventilation is provoked, adequate gas exchange should be achieved at lower peak airway pressures, potentially reducing baro/volutrauma, air leak and bronchopulmonary dysplasia. Synchronous ventilation can potentially be achieved by manipulation of rate and inspiratory time during conventional ventilation and employment of patient triggered ventilation.

OBJECTIVES

To compare the efficacy of: (i) synchronized mechanical ventilation, delivered as high frequency positive pressure ventilation (HFPPV) or patient triggered ventilation - assist control ventilation (ACV) or synchronous intermittent mandatory ventilation (SIMV)) with conventional ventilation (CMV) (ii) different types of triggered ventilation (ACV, SIMV, pressure regulated volume control ventilation (PRVCV) and SIMV plus pressure support (PS) SEARCH STRATEGY: Searches from 1985-2007 of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2007),Oxford Database of Perinatal Trials, MEDLINE, previous reviews, abstracts and symposia proceedings; hand searches of journals in the English language and contact with expert informants.

SELECTION CRITERIA

Randomised or quasi-randomised clinical trials comparing synchronized ventilation delivered as high frequency positive pressure ventilation (HFPPV) or triggered ventilation (ACV/SIMV) to conventional mechanical ventilation (CMV) in neonates. Randomised trials comparing different triggered ventilation modes (ACV, SIMV, SIMV plus PS and PRVCV) in neonates.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes including mortality, air leaks (pneumothorax or pulmonary interstitial emphysema (PIE)), severe intraventricular haemorrhage (grades 3 and 4), bronchopulmonary dysplasia (BPD) (oxygen dependency beyond 28 days), moderate/severe BPD (oxygen/respiratory support dependency beyond 36 weeks postmenstrual age (PMA) and duration of weaning/ventilation. Four comparisons were made: (i) HFPPV vs. CMV; (ii) ACV/SIMV vs. CMV; (iii) ACV vs. SIMV or PRVCV vs. SIMV (iv) SIMV plus PS vs. SIMV. Data analysis was conducted using relative risk for categorical outcomes, weighted mean difference for outcomes measured on a continuous scale.

MAIN RESULTS

Fourteen studies were eligible for inclusion. The meta-analysis demonstrates that HFPPV compared to CMV was associated with a reduction in the risk of air leak (typical relative risk for pneumothorax was 0.69, 95% CI 0.51, 0.93). ACV/SIMV compared to CMV was associated with a shorter duration of ventilation (weighted mean difference -34.8 hours, 95% CI -62.1, -7.4). ACV compared to SIMV was associated with a trend to a shorter duration of weaning (weighted mean difference -42.4 hours, 95% CI -94.4, 9.6). Neither HFPPV nor triggered ventilation was associated with a significant reduction in the incidence of BPD. There was a non-significant trend towards a lower mortality rate using HFPPV vs. CMV and a non-significant trend towards a higher mortality rate using triggered ventilation vs. CMV. No disadvantage of HFPPV or triggered ventilation was noted regarding other outcomes. Since the last review, two new patient triggered modes have been included: pressure regulated volume control ventilation (PRVCV) and SIMV plus pressure support. Each of these methods of ventilation has only been tested in single randomised trials with no significant advantages in important outcomes.

AUTHORS' CONCLUSIONS

Compared to conventional ventilation, benefit is demonstrated for both HFPPV and triggered ventilation with regard to a reduction in air leak and a shorter duration of ventilation, respectively. In none of the trials was complex respiratory monitoring undertaken and thus it is not possible to conclude that the mechanism of producing those benefits is by provocation of synchronized ventilation. Further trials are needed to determine whether synchronized ventilation is associated with other benefits, but optimisation of trigger and ventilator design with respect to respiratory diagnosis is encouraged before embarking on further trials. It is essential newer forms of triggered ventilation are tested in adequately powered randomised trials with long-term outcomes before they are incorporated into routine clinical practice.

The effects of antenatal smoking on lung function and respiratory symptoms in infants and children

We highlight evidence demonstrating antenatal smoking exposure is an important risk factor for increased respiratory symptoms and lung function abnormalities in infants and children. Epidemiological studies have demonstrated an excess both of wheezing in the first two years after birth and asthma and persistent wheezing in older children. Lung function testing in children exposed to antenatal smoking has demonstrated a reduction in airway function. Antenatal exposure of nicotine to animal models results in pulmonary hypoplasia, fewer but larger alveoli and altered airway morphology. Pulmonary function testing, however, has not demonstrated that infant lung volume is affected by antenatal smoking exposure, other than due to the expected effect of smoking on somatic growth, but there is an adverse effect on airway development. There is no evidence that antenatal smoking exposure increases bronchial hyperreactivity, rather it may be associated with a diminished response to both bronchoconstrictors and bronchodilators in infants.

Two visual systems re-viewed

The model proposed by the authors of two cortical systems providing 'vision for action' and 'vision for perception', respectively, owed much to the inspiration of Larry Weiskrantz. In the present article some essential concepts inherent in the model are summarized, and certain clarifications and refinements are offered. Some illustrations are given of recent experiments by ourselves and others that have prompted us to sharpen these concepts. Our explicit hope in writing our book in 1995 was to provide a theoretical framework that would stimulate research in the field. Conversely, well-designed empirical contributions conceived within the framework of the model are the only way for us to progress along the route towards a fully fleshed-out specification of its workings.

Effect of electronic compensation on plethysmographic airway resistance measurements

OBJECTIVES

To compare the performance of a plethysmograph which incorporated electronic compensation (Jaeger) to one which incorporated a heated humidified breathing system (Hammersmith plethysmograph).

WORKING HYPOTHESIS

The performance of a plethysmograph which incorporated electronic compensation would be impaired compared to that which incorporated a heated humidified system.

STUDY DESIGN

In vitro and in vivo comparison.

PATIENT SELECTION

Eleven children, median postnatal age 13 (range 5-15) months.

METHODS

In vitro, the plethysmographs were assessed using known resistances (1.94, 4.85, and 6.80 kPa, equivalent to 20, 50, and 70 cm H(2)O/L/sec, respectively). In vivo, comparison was made of the results of children studied in both plethysmographs.

RESULTS

In vitro, the resistance results of the two plethysmographs were similar to each other and to the known resistances. In vivo, the median "effective" airways resistance result of the Jaeger (4.15 kPa/L/sec) was significantly higher than the inspiratory resistance of the Hammersmith plethysmograph (3.0 kPa/L/sec), but the median inspiratory resistances of the Jaeger were significantly lower than those of the Hammersmith plethysmograph (2.8 kPa/L/sec vs. 3.0 kPa/L/sec). The mean within patient coefficient of variability for inspiratory resistance of the Jaeger plethysmograph (16.7%) was significantly higher than that of the Hammersmith plethysmograph (11.6%) (P = 0.014).

CONCLUSION

These results suggest plethysmographs which incorporate electronic compensation may be inappropriate for use in infants and very young children.

Radiotherapy for low-grade gastric marginal zone lymphoma: a retrospective study

BACKGROUND

We evaluated the efficacy and toxicity of radiotherapy (RT) in patients with low-grade gastric marginal zone lymphoma.

METHODS

A retrospective review of consecutive cases of gastric marginal zone lymphoma treated by radical RT at the Peter MacCallum Cancer Centre and Radiation Oncology Victoria between January 1980 and September 2003 was carried out.

RESULTS

Eighteen patients (11 men and 7 women) were identified. The median age at commencement of RT was 65 years (range 42-84 years). Prior treatment included Helicobacter pylori eradication in 12 patients, chemotherapy in 7 and surgery in 2, whereas 2 patients had no prior therapy. The median time to progression after commencement of last treatment before RT was 4.8 months (range 0-129.4 months). The radiation fields included the stomach plus perigastric and coeliac nodes in 15 patients (83%), stomach plus spleen in 2 patients (11%) and stomach plus para-aortic nodes in 1 patient (6%). The median RT dose was 30 Gy (range 30-36 Gy) in a median 20 fractions (range 17-24 fractions). One patient required treatment interruption for acute toxicity. A complete response on post-RT biopsies was achieved in 17 of 18 patients (94%). With a median follow up of 4.5 years after RT, 3 of these 17 patients (18%) have had a recurrence. At the last follow up, 11 patients were alive in continuous complete histological remission. No late renal toxicity was identified.

CONCLUSION

Radiotherapy is an effective, well-tolerated treatment for patients with low-grade gastric marginal zone lymphoma, including those who have had prior therapy.

Performance of neonatal ventilators in volume targeted ventilation mode

AIM

To test the hypothesis that in volume targeted ventilation modes, ventilator performance would vary according to ventilator type.

METHODS

Four neonatal ventilators: Draeger Babylog 8000 (Draeger Medical, Germany), SLE 5000 infant ventilator (SLE systems, UK), Stephanie paediatric ventilator (F. Stephan Biomedical, German) and V.I.P. Bird gold (Viasys Healthcare, USA) were assessed using a lung model. Delivered peak pressure, inflation time, mean airway pressure (MAP) and volume were measured.

RESULTS

At the same preset ventilator settings, the Stephanie and V.I.P. Bird ventilators delivered significantly lower peak pressures and tended to deliver lower MAPs than the other two ventilators. At a volume targeted ventilation level of 5 mL, the SLE and the V.I.P. Bird delivered significantly shorter inflation times. The above differences related to differences in the airway pressure waveforms delivered by the four ventilators. The V.I.P. Bird had a less variable volume delivery, but this was always significantly lower than the preset volume guarantee level but higher than the volume displayed by the ventilator.

CONCLUSION

In volume targeted ventilation modes, performance differs between neonatal ventilator types; these results may have implications for clinical practise.

A phase I/II trial of celecoxib with chemotherapy and radiotherapy in the treatment of patients with locally advanced oesophageal cancer

BACKGROUND

The study's aim was to determine the maximum tolerated dose (MTD) of celecoxib combined with chemoradiotherapy (CRT) for locally advanced oesophageal cancer (OC).

METHODS

CRT comprised of 5FU (1000 mg/m(2)/day, days 1-4, weeks 1 & 5), cisplatin (75 mg/m(2), days 1 & 29) and radiotherapy (50 Gy in 25 fractions or 50.4 Gy in 28 fractions). Celecoxib was given daily during CRT at one of five doses (200 mg bd to 600 mg bd). Three to six patients were assigned per dose.

RESULTS

Thirteen patients were recruited before trial closure due to external safety concerns regarding celecoxib. Median follow up was 17 months (95% CI 9 - >39). The highest administered dose was 400 mg bd (n=4) with one dose-limiting toxicity at this level: grade 3 rash. Five (38%) and 8(62%) patients had grade 3 non-haematological and haematological toxicities respectively. No grade 4 toxicities occurred. Radiological response rate was 54% (n=7: all CR). Six patients had resection with one pathological CR. Median progression-free and overall survival were 8.8 (95% CI 5.1 - >24.8) and 19.6 months (95% CI 7.3 - >39) respectively.

CONCLUSIONS

A MTD was not reached. The regimen was tolerable, indicating that celecoxib can be safely administered with CRT for locally advanced OC.

Parotid-sparing radiotherapy: does it really reduce xerostomia?

AIMS

Parotid-sparing radiotherapy (PSRT) was introduced for patients with selected head and neck cancer requiring bilateral upper-neck irradiation at our centre in 2000. The aim of this study was to compare the subjective degree of xerostomia in patients treated with PSRT between January 2000 and June 2003 with patients treated using conventional techniques (radiotherapy) over the same period.

MATERIALS AND METHODS

Eligible patients were required to have completed treatment 6 months previously and be recurrence-free at the time of interview. PSRT was defined as conformal radiotherapy, in which the mean dose to at least one parotid gland was 33 Gy or less, as determined by the dose-volume histogram. Patients receiving radiotherapy were treated with standard parallel-opposed fields, such that both parotids received a minimum of 40 Gy. Xerostomia was assessed using a validated questionnaire containing six questions with a rating between 0 and 10. Lower scores indicated less difficulty with xerostomia.

RESULTS

Thirty-eight eligible patients treated with PSRT were identified: 25 with oropharyngeal cancer and 13 with nasopharyngeal cancer (NPC). The mean overall questionnaire score (Q1-5) for this group was 4.20 (standard error = 0.33). Forty-four patients (24 oropharyngeal, 21 NPC) treated with radiotherapy over the same period were eligible. The mean overall questionnaire score (Q1-5) for this group was 5.86 (standard error = 0.35). The difference in mean overall scores between the two groups of patients was statistically significant (P < 0.001), as were the scores for four of the six individual questions.

CONCLUSION

These results suggest that PSRT offers improved long-term xerostomia-related quality of life compared with conventional radiotherapy.

Reaching errors in optic ataxia are linked to eye position rather than head or body position

When reaching towards a visual stimulus, spatial information about the target must be transformed into an appropriate motor command. Visual information is coded initially in retinotopic coordinates, while the reaching movement ultimately requires the specification of the target position in limb-centred coordinates. It is well established that the posterior parietal cortex (PPC) plays an important role in transforming visual target information into motor commands. Lesions in the PPC can result in optic ataxia, a condition in which the visual guidance of goal-directed movements is impaired. Here, we present evidence from two patients with unilateral optic ataxia following right PPC lesions, that the pattern of reaching errors is linked to an eye-centred frame of reference. Both patients made large errors when reaching to visual targets on the left side of space, while facing and fixating straight ahead. By varying the location of fixation and the orientation of the head and body, we were able to establish that these large errors were made specifically to targets to the left of eye-fixation, rather than to the left of head-, body-, or limb-relative space. These data support the idea that visual targets for reaching movements are coded in eye-centred coordinates within the posterior parietal cortex.

Problems in the measurement of functional residual capacity

Accurate assessment of lung volume in infancy is important to determine the impact of disease and the efficacy of therapies. A new generation of infant plethysmographs with lower apparatus deadspace has been produced, but gives lower volume results than those from older traditional plethysmographs. We hypothesized that the new plethysmographs might have greater sensitivity to the adiabatic effect and hence they, rather than the traditional plethysmographs, produced erroneous results. Our aim was to assess the influence of the adiabatic effect on the results of a contemporary plethysmograph, an older traditional plethysmograph and a helium gas dilution system using a lung model. Altering the amount of copper wool within the lung model allowed the influence of the adiabatic effect on the plethysmographic results to be assessed. The measured compared to the actual volumes were significantly lower for the contemporary plethysmograph compared to the traditional plethysmograph (p < 0.001) and to the helium gas dilution system (p < 0.001). Under optimal testing conditions the contemporary plethysmograph under-recorded by 11-13%, whereas the other two systems gave similar results to the actual volumes. As the effect of the adiabatic effect was increased, the discrepancy between the results of the contemporary and the traditional plethysmographs increased. We conclude, the contemporary plethysmograph is more sensitive to adiabatic effects and hence under-records.

A phase I trial of high-dose palliative radiotherapy plus concurrent weekly Vinorelbine and Cisplatin in patients with locally advanced and metastatic NSCLC

The role of concurrent chemoradiotherapy (CRT) in patients with non-small-cell lung cancer (NSCLC) unsuitable for radical therapy but who require locoregional treatment has not been defined. The aims of this phase I trial were thus to develop a novel regimen of weekly chemotherapy concurrent with high-dose palliative RT (40 Gy/20 fractions) and assess its tolerability, objective and symptomatic response rates. Eligible patients had stage I–IIIB NSCLC unsuitable for radical RT or limited stage IV disease, ECOG PS⩽1 and required locoregional therapy. Treatment was RT (40 Gy/20 fractions/5 per week) and weekly Vinorelbine plus Cisplatin escalated in six planned dose levels (DLs). At 4 weeks post-RT, patients received two cycles of Cisplatin 80 mg m⁻² day 1+Vinorelbine 25 mg m⁻² days 1, 8, 15. Dose-limiting toxicities (DLTs) were defined in the CRT phase. Disease-related symptoms were assessed by the Lung Cancer Symptom Scale. In all, 24 patients accrued, stage IIIB (n=12) and IV disease (n=10). The highest administered dose was at DL 4, Vinorelbine 30 mg m⁻²+Cisplatin 20 mg m⁻² with DLTs of grade 4 neutropenia in two of three patients. No grade 3 or 4 nonhaematological toxicities were observed. The overall radiological response rate was 65% (n=23: complete response 4% and partial response 61%) and infield FDG-PET responses were seen in 89% (n=18). There was an improvement or stabilisation of symptoms and quality of life. Dose level 3, Vinorelbine 25 mg m⁻²+Cisplatin 20 mg m⁻², is recommended for further assessment. This regimen was tolerable and produced meaningful responses for patients for whom locoregional control is required, but who are unsuitable for radical CRT.

Dampened ventilatory response to added dead space in newborns of smoking mothers

BACKGROUND

Term newborns can compensate fully for an imposed dead space (tube breathing) by increasing their minute ventilation.

OBJECTIVE

To test the hypothesis that infants of smoking mothers would have an impaired response to tube breathing.

DESIGN

Prospective study.

SETTING

Perinatal service.

PATIENTS

Fourteen infants of smoking and 24 infants of non-smoking mothers (median postnatal age 37 (11-85) hours and 26 (10-120) hours respectively) were studied.

INTERVENTIONS

Breath by breath minute volume was measured at baseline and when a dead space of 4.4 ml/kg was incorporated into the breathing circuit.

MAIN OUTCOME MEASURES

The maximum minute ventilation during tube breathing was determined and the time constant of the response calculated.

RESULTS

The time constant of the infants of smoking mothers was longer than that of the infants of non-smoking mothers (median (range) 37.3 (22.2-70.2) v 26.2 (13.8-51.0) seconds, p = 0.016). Regression analysis showed that maternal smoking status was related to the time constant independently of birth weight, gestational or postnatal age, or sex (p = 0.018).

CONCLUSIONS

Intrauterine exposure to smoking is associated with a dampened response to tube breathing.