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Addition of low VT levels to patient-triggered modes increases the WOB during weaning. This can be avoided by using a VT level of 6 mL/kg. ABSTRACTOBJECTIVES. 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.METHODS. 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.RESULTS. 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. CONCLUSIONS. Low volume-targeted levels increase the work of breathing during volume-targeted ventilation. Our results suggest that, during weaning, a volumetargeted level of 6 mL/kg, rather than a lower level, could be used to avoid an increase in the work of breathing. Pediatrics 2009;123:e679-e684 D URING VOLUME-TARGETED VENTILATION (VTV), a nearly constant tidal volume is delivered. This minimizes excessive tidal volume delivery, reducing volutrauma and the likelihood of hypocarbia. In one study, use of VTV was associated with avoidance of severe hypocarbia or hypercarbia in Ͼ90% of the first 48 hours for infants at Ͻ33 weeks of gestation. 1 VTV may be useful in situations in which there are changes in lung function, such as when infants are recovering from respiratory distress and being weaned from a ventilator. During VTV, compared with pressure-limited ventilation, blood gas values were maintained at lower airway pressures. 2 Those results suggested that infants make a greater contribution to minute ventilation during VTV than during pressure-limited ventilation and hence their work of breathing (WOB) may be higher with VTV, which may affect weaning and extubation adversely. 3 It seems likely, however, that higher volume-targeted (VT) levels would reduce the WOB and, with a sufficiently large targeted volume, the WOB would be lower during ventilatory support with versus without volume targeting. These hypotheses have not been tested, however, and a variety of VT levels have been used in VTV studies. 4-8 The aims of this study w...

Background: During volume-targeted ventilation (VTV), a constant volume is delivered with each ventilator inflation. Objectives: To determine whether VTV compared to pressure-limited ventilation (PLV) reduced the time to reach weaning criteria in prematurely born infants with acute respiratory distress, and if any difference was explained by better respiratory muscle strength and/or a lower work of breathing (WOB). Methods: Infants of <34 weeks of gestational age ventilated for <24 h in the first week after birth were randomised to receive either VTV or PLV. The primary outcome was the time to achieve pre-specified weaning criteria. Respiratory muscle strength was assessed by the measurement of the maximum inflation and expiratory pressures, and the WOB assessed by the transdiaphragmatic pressure time product. Other outcomes reported are the duration of ventilation, occurrence of patent ductus arteriosus, pneumothorax, intraventricular haemorrhage, periventricular leukomalacia and episodes of hypocarbia. Results: Forty infants, median gestational age 27 (range 23-33) weeks, were recruited. The time taken to achieve weaning criteria was similar in the two groups [median 14 h (VTV) vs. 23 h (PLV)]. There were no significant differences between the groups with regard to respiratory muscle strength, WOB or other outcomes, except that fewer of the VTV compared to the PLV group had episodes of hypocarbia (8 vs. 19; p < 0.001). Conclusion: In prematurely born infants with acute respiratory failure, use of VTV did not reduce the time to reach weaning criteria, but was associated with a reduction in episodes of hypocarbia.

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