Abstract
Background: Excised lungs expand asynchronously and nonuniformly during high frequency ventilation (Lehr 1985). Moreover, in healthy adults, pressure oscillations above 4 Hz applied at the mouth propagate inhomogeneously in the chest wall (Dellacà et al 2003).
Objective: In newborn infants receiving HFOV, characterizing the regional heterogeneities of chest wall displacements at different oscillatory frequencies.
Methods: We studied 14 newborns (gestational age=29±4 wks; postnatal age=7±8 days; body weight=1.2±0.7 Kg). The following frequencies were tested: 5, 8, 10, 12 and 15 Hz. For each frequency, the displacements of 24 passive markers placed on the infant's chest wall were measured by optoelectronic plethysmography. A subset of 6 points were used to evaluate chest wall movements in the cranio-caudal direction. For each marker we computed: the displacement normalized for the ventilation pressure amplitude, the phase shift vs. mrk 1.
Results: Pressure oscillations propagation decreased with frequency and was higher in the abdominal than in the ribcage compartment (Figure 1 left). The asynchrony of displacements in the cranio-caudal direction increases with f (Figure 1 right).
Conclusion: In infants receiving HFOV the chest wall oscillates asynchronously and non-uniformly. With increasing frequency the pressure oscillations propagation reduces with frequency, while asynchronies become more evident.
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