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ABSTRACT: The objectives of this study were to determine the impact of different volume-targeted levels on the work of breathing and to investigate whether a level that reduced the work of breathing below that experienced during ventilatory support without volume targeting could be determined.
The transdiaphragmatic pressure-time product, as an estimate of the work of breathing, was measured for 20 infants (median gestational age: 28 weeks) who were being weaned from respiratory support by using patient-triggered ventilation (either assist-control ventilation or synchronous intermittent mandatory ventilation). The transdiaphragmatic pressure-time product was measured first without volume targeting (baseline) and then at volume-targeted levels of 4, 5, and 6 mL/kg, delivered in random order. After each volume-targeted level, the infants were returned to baseline. Each step was maintained for 20 minutes.
The mean transdiaphragmatic pressure-time product was higher with volume targeting at 4 mL/kg in comparison with baseline, regardless of the patient-triggered mode. The transdiaphragmatic pressure-time product was higher at a volume-targeted level of 4 mL/kg in comparison with 5 mL/kg and at 5 mL/kg in comparison with 6 mL/kg. The mean work of breathing was below that at baseline only at a volume-targeted level of 6 mL/kg.
Low volume-targeted levels increase the work of breathing during volume-targeted ventilation. Our results suggest that, during weaning, a volume-targeted level of 6 mL/kg, rather than a lower level, could be used to avoid an increase in the work of breathing.
PEDIATRICS 05/2009; 123(4):e679-84. · 4.47 Impact Factor
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ABSTRACT: A large number of ventilation strategies are now available for the neonate. This review has focused on new information, that is, studies published since 2000 and the implication of their results for current clinical practice. Meta-analysis of randomised trials has demonstrated that assist control and synchronous intermittent mandatory ventilation (SIMV) shortens the duration of ventilation only if started in the recovery rather than the early stage of respiratory disease. A recent randomised trial demonstrated pressure-regulated volume control ventilation may also have no advantages if started early. Weaning by SIMV with pressure support is better (reducing oxygen dependency) than SIMV alone. Meta-analysis of volume-targeted ventilation demonstrated significant reductions in the duration of ventilation and pneumothorax, but the trials were small and of different designs. Volume guarantee may provide more consistent blood gas control. The level of volume targeting appears to be crucial to the success of this technique. Meta-analysis of randomised trials of prophylactic high-frequency oscillation trials has shown a modest reduction in bronchopulmonary dysplasia. Randomised trials have failed to confirm the advantages of nasal continuous positive airway pressure (NCPAP) seen in various non-randomised studies; however, the randomised trials reported to date have been small. Inhaled nitric oxide (NO) does not improve the outcome of prematurely born infants with severe respiratory failure, but early low-dose prolonged iNO appears to have benefits that merit further testing. More randomised trials with long-term outcomes are required to identify the optimal ventilation strategy(ies) for the neonate.
European Journal of Pediatrics 11/2007; 166(10):991-6. · 1.88 Impact Factor
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ABSTRACT: To survey current practice regarding neonatal respiratory support strategies to determine whether it reflected evidence from randomised trials.
A questionnaire (in Supplementary Material online) survey of all U.K. neonatal units was undertaken to determine what modes of ventilation, types of endotracheal tube, lung function monitoring and oxygen saturation levels were used.
There was an 80% response rate. Most (73%) units used in prematurely born infants (in the first 24 h) the intermittent positive pressure ventilation, and other respiratory modes included: CPAP (2%), triggered ventilation with or without volume guarantee (22%) and high frequency oscillation (2%). Only 15% of units used assist control mode for weaning; the preferred weaning mode was synchronous intermittent mandatory ventilation (73%). Few units used shouldered endotracheal tubes (3%) or lung function measurements (25%) to aid choice of ventilator settings. Oxygen saturation levels from 80% to 98% were used, levels greater or equal to 95% were used by 11% of units for infants with acute respiratory disease but by 34% of units for BPD infants (p < 0.001).
Many practitioners do not base their choice of neonatal respiratory support strategies on the results of large randomised trials; more effective methods are required to ensure evidence-based practice.
Acta Paediatrica 08/2007; 96(8):1115-7. · 2.07 Impact Factor
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ABSTRACT: To test the hypothesis that in volume targeted ventilation modes, ventilator performance would vary according to ventilator type.
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.
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.
In volume targeted ventilation modes, performance differs between neonatal ventilator types; these results may have implications for clinical practise.
Acta Paediatrica 03/2007; 96(2):176-80. · 2.07 Impact Factor
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ABSTRACT: A variety of ventilation modes are available for the newborn. Although, there have been randomised trials assessing certain modes, these have generally only included prematurely born infants with RDS or infants with severe respiratory failure. Meta-analysis of the results of those trials has demonstrated that neither patient triggered nor high frequency oscillatory ventilation is advantageous for the prematurely born infant with RDS, but extracorporeal membrane oxygenation increases survival in infants with severe respiratory failure. Appropriately designed studies are required to determine the role of newer ventilation modes and whether forms of respiratory support avoiding intubation are less injurious to the lungs. Research should also focus on infants with other respiratory disorders, particularly BPD. Prior to further randomised trials being undertaken, it is essential that the optimum method of applying each ventilator mode is identified and it is clearly understood whether differences in ventilator/oscillator performance influence outcome.
Early Human Development 01/2006; 81(12):957-64. · 2.05 Impact Factor
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ABSTRACT: Our aim was to assess the influence of oscillatory frequency, inspiratory-to-expiratory (I:E) ratio and airway pressure on gas trapping during high frequency oscillatory ventilation (HFOV). A lung model was used, which had a high compliance (4.0 ml (cmH(2)O)(-1)) and resistance (160 cmH(2)O l(-1) s(-1)) resulting in a long time constant (0.64 s). To assess whether gas trapping occurred, the mean pressure within the lung model (equivalent to alveolar pressure) was compared to the mean airway pressure (MAP) measured at the manifold (manifold MAP) of the two oscillators used, the SLE 5000 (I:E ratio 1:1) and the Sensor Medics 3100A (tested at I:E ratios of 1:2 and 1:1). The effects were assessed of raising the MAP from 15 to 35 cmH(2)O, the oscillatory amplitude from 30 to 70 cmH(2)O and the frequency from 5 to 15 Hz (5 to 20 Hz SLE only). There were no significant trends for differences between the pressure within the lung model and the 'manifold' MAP to increase (i.e. no evidence of gas trapping), as MAP, amplitude or frequency was increased, regardless of which oscillator or I:E ratio was used. Increasing the pressure amplitude led to a progressive fall in the pressure within the lung model when an I:E ratio of 1:2 was used (p < 0.05). Our results suggest that significant gas trapping does not occur during HFOV even if there is high compliance and resistance.
Physiological Measurement 06/2005; 26(3):329-36. · 1.68 Impact Factor
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ABSTRACT: Conventional time cycled, pressure-limited ventilation has been used in neonatal intensive care units for many years. Meta-analysis of randomised trials demonstrated that conventional ventilation at rates of at least 60 breaths per minute rather than at slower rates significantly reduced the risk of airleak. Patient triggered ventilation more successfully than conventional ventilation promotes synchronous ventilation; nevertheless, randomised trials demonstrated the only advantage of patient triggered ventilation was that it was associated with a shorter duration of ventilation. More sophisticated triggered modes, pressure support, volume guarantee and proportional assist ventilation, have been developed. Results from physiological studies suggest these modes may be advantageous, but they have not been tested in large randomised controlled trials with long-term outcomes. Many anecdotal studies report avoidance of intubation and mechanical ventilation by use of continuous positive airways pressure reduces bronchopulmonary dysplasia, but the randomized trials which have been undertaken have been too small to appropriately address that outcome. Prophylactic high frequency oscillatory ventilation has been examined in many trials, but overall no benefit or disadvantage has been demonstrated. In conclusion, studies to date have not identified a clear advantage of any of the newer ventilation modes.
Current Pediatric Reviews 05/2005; 1(2):115-118.
