Our findings indicate that BNP levels are elevated in infants with PPHN but not in infants with other forms of respiratory distress not associated with PPHN. Elevated BNP levels in term or near-term infants with respiratory distress should increase the suspicion of PPHN. Serial determination may also be helpful in monitoring the clinical course of such infants.

The predicted shear-induced shift of the wave phase velocity, the essence of the shear-modified ion-acoustic (SMIA) instability mechanism that reduces ion Landau damping for otherwise damped ion-acoustic waves [V. Gavrishchaka et al., 80, 728 (1998)], is verified with direct measurements in a strongly magnetized laboratory plasma. The SMIA growth rate is shown to increase with increasing shear, as predicted. SMIA wave propagation is shown to be possible at both small and large angles to the magnetic field, consistent with space observations of ion-acoustic-like waves.

The aim of this study was to define quantitative measures for assessing the integration and maturation of suck and swallow rhythms in preterm infants as they relate to each other. Fourteen preterm infants (eight males, six females; gestational age range 26 to 32 weeks) with bronchopulmonary dysplasia (BPD) and an age-matched cohort of 20 infants (10 males, 10 females; gestational age range 26 to 33 weeks) without BPD were studied weekly from time of initiation of oral feeding using simultaneous recordings of nipple and pharyngeal pressure. The integration of suck and swallow rhythms was quantified by using the coefficient of variation (COV) of the suck-swallow dyad interval. Infants without BPD had a significant correlation between increasing postmenstrual age (PMA) and decreasing COV of the dyadic interval (increasing stabilization; r=0.45; p=0.008). In the non-BPD cohort 35 weeks or less PMA, the mean dyadic COV was 0.42 (SD 0.12) versus 0.34 (SD 0.09) in those more than 35 weeks PMA (p=0.039). In contrast, dyadic stability in infants with BPD was not correlated with PMA. Infants with BPD of more than 35 weeks PMA had less dyadic stability (0.45, SD 0.10) than did age-matched controls (p<0.001). Dyadic stability was also correlated with feeding efficiency in the non-BPD group (r=0.46;p=0.007) but not in the BPD cohort. Therefore, ontogeny of rhythmic suckle feeding can be described quantitatively in preterm infants, allowing comparison with at-risk populations. Infants with BPD do not follow predicted maturational patterns of suck-swallow rhythmic integration.

We previously used cervical auscultation (CA) to describe the stability of swallow-associated sounds of infant feeding. To date, no similar studies have been performed in adults. The objectives of this study were to identify the initial discrete sounds (IDS) of adult swallows and compare the stability of IDS signals in infants to that of adults. We performed CA with a microphone and accelerometer fixed simultaneously to the neck of 20 healthy adults. Each participant consumed a liquid, puree, and solid. The microphone and accelerometer collected signals of similar duration. The variance index (VI), an assessment of the stability of the IDS, was compared in adults and a group of low-risk preterm infants. The VI of adults swallowing liquid (29.1 [24.1, 36.6] {25%, 75%}) did not differ from that of preterm infants older than 36 weeks PMA (36.3 [33.4, 41.9]), but was lower than the VI of infants younger than 36 weeks PMA (49.0 [46.4, 51.1]; p < 0.05). This is the first real-time comparison of microphones and accelerometers for CA. The stability of IDS of low-risk preterm infants approaches that of normal adults as the infants age. Because successful feeding in infants is often used as a surrogate for normal development, the stability of swallow-associated sounds deserves more investigation as a potential marker for neurologic well-being.

This study describes swallow-breath interaction and phase of respiration with swallow during nonnutritive suck (NNS) in low-risk preterm infants. Suckle and swallow, thoracic motion, and airflow were measured in 16 infants during NNS. Logistic regression models were used to describe swallow-breath interaction and phase of respiration with swallow. One hundred seventy-six swallows occurred in 35 NNS periods. Swallow-breath interaction occurred as: central apnea (CA), obstructive apnea (OA), or attenuated respiration (AR). AR was associated with increased weeks post-first nipple feeding. OA occurred less often in males and with increased weeks post-first nipple feeding. In looking at the phase of respiration, more swallows occurred at beginning expiration with increased gestational age, increased weeks post-first nipple feed, and increased weeks before first nipple feed. More swallows occurred at midexpiration with more swallows per study, increased birth weight (BWT), and weeks before first nipple feed. Fewer swallows occurred at end expiration with increased weeks before first nipple feed. Fewer swallows occurred at midinspiration with increased swallows per study. Fewer swallows occurred at apnea with increasing BWT, more occurred with increased swallows per study. In low-risk preterm infants, swallow-breath interaction progresses from CA and OA to AR. The phase of respiration with swallow shows a maturation progression.