Effect of neck rotation on the timing and pattern of infant tidal breathing.

While neck flexion and extension are known to influence the patency of the upper airway, far less information is available regarding the effects of neck rotation. The effect of neck rotation on respiratory rate (RR), expiratory time (tE), and phase angle (phi) was assessed in 17 healthy infants aged between 1 and 4 months. An inclinometer was used to measure neck rotation and uncalibrated Respiratory inductive Plethysmography to measure the dependent variables while the infants were in natural, quiet sleep. Baseline measurements were made with the head positioned centrally (0 degree rotation); further measurement positions included 30 degrees, 60 degrees, 90 degrees rotation, and repeat measurement at 0 degree (0r degree) in randomized order. Mean RR, tE, and phi were determined for each infant in each position. Using the paired t-test, RR at 0 degree rotation was significantly higher than that at 0r degree rotation (mean difference, 5 bpm; 95% CI, 2.1, 8.1; P = 0.0023); mean tE at 0 degree rotation was significantly shorter than at 0r degree rotation (mean difference, -0.18s; 95% CI, -0.27, -0.07; P = 0.002); whereas phi remained similar (mean difference, 10 degrees; 95% CI, -2.2, 22.3; P = 0.10. These changes probably reflect the slowing of metabolism that occurs after the onset of quiet sleep, and they emphasize the importance of randomization. Measurements at 0r degree were randomized and hence were most likely to reflect the true basal condition of the infant with the head in a neutral position. Consequently, these data, rather than those collected at 0 degree at the onset of quiet sleep, were used for comparisons with all subsequent positional changes. When comparing the positions whose order was randomized, neck rotation did not significantly affect RR (P = 0.445), tE (P = 0.272), or phi (P = 0.169). However, two infants demonstrated marked changes in respiratory pattern with decreases in RR and increases in tE at 90 degrees rotation, suggesting that some infants may be susceptible to obstruction in this position.