Page 40 - Physiological based CPAP for preterm infants at birth Tessa Martherus
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Chapter 1
Which CPAP delivering device?
Several pressure delivering devices are currently used to apply CPAP in the delivery room. It is not possible to apply CPAP with a self-inflating mask and bag. The Neopuff T-piece creates PEEP by supplying a constant flow against an adjustable resistor, whereas the Benveniste valve creates PEEP by flow opposition (38, 39). Mechanical ventilators have a microprocessor controlled expiratory valve at the end of the expiratory limb that detect pressure changes and adjust the valve to maintain the target pressure level. Bubble CPAP devices have an expiratory limb placed at fixed depths under water to create pressure with bias gas flow forming bubbles that cause oscillations in the delivered CPAP (40-42).
Although most healthcare providers prefer to use a device that is capable to deliver PPV, it is currently unclear which device is most effective for applying CPAP at birth. Bench tests (40-42) found the lowest pressure stability and highest expiratory resistance with the Neopuff when compared with bubble CPAP, ventilator and the Benveniste valve. The authors stated that these factors combined could lead to a high work of breathing (WOB) (40-42). To reduce WOB, Donaldsson et al. (43) developed a novel ventilator system that reduced the WOB during expiration. In a bench test, they reported higher pressure stability and lower WOB when using the novel device with masks or nasal prongs compared with the Neopuff. We find these findings are difficult to extrapolate to the clinical setting. The sinusoidal pump was used to simulate breathing, leading to an active and forced expiration, whereas the infants’ expiration is passive.
Pillow et al. (44) argued that the oscillation of bubble CPAP may promote opening of the airways, hence, improving alveolar recruitment. Comparing bubble CPAP and the Neopuff in newborn lambs showed that bubble CPAP improved arterial oxygen levels 3 hours after birth (45). Although the WOB is dependent on the level of gas flow, no physiological or clinical benefits were found when increasing the flow from 8 to 12 L/min.
There is no further clinical data comparing CPAP devices in the delivery room, except that Donaldson et al. (43) compared the novel resuscitation device using facemask and nasal prongs with the Neopuff in a randomised feasibility trial including 36 infants 27-34 weeks of gestation. There were no differences in study outcomes; the results were difficult to interpret given the large differences in gestational age (231±9.9 vs 228±10.7 vs 215±16.9 days) between groups. Following this feasibility trial, Jonsson et al. (46) are now comparing both devices in a large (n=250) randomised clinical trial, the CORSAD (NCT02563717), including infants<28 weeks of gestation.
Respiratory support strategies other than CPAP have also been tried in the delivery room. Non-invasive high frequency oscillation has been tested and is anecdotally used in the delivery room, although no published studies are available. Furthermore, an observational cohort study (47) in infants between 23 and 29 weeks of gestation examined nasal high flow at 6-8 L/min to support spontaneous breathing. This study stated that nasal high flow can create
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