The influence of maturation on extrathoracic airway (ETA) stability during quiet sleep was determined in 13 normal preterm infants of 1.41 ± 0.14 (SD) kg birth weight and 32 ± 2 wk estimated gestational age. Studies began in the first week of life and were performed three times at weekly intervals. A drop in intraluminal pressure within the ETA was produced by external inspiratory flow-resistive loading (60 cmH2O · l-1 · s at 1 l/min); an increase in intrinsic resistance, indicating airway narrowing, was sought as a measure of ETA instability. Baseline total pulmonary resistance was not significantly different between weeks 1, 2, and 3 (88 ± 35, 65 ± 24, and 61 ± 17 cmH2O · l-1 · s, respectively) but increased markedly above baseline with loading to 144 ± 45 cmH2O · l-1 · s during week 1 (P < 0.001), 89 ± 28 cmH2O · l-1 · s at week 2 (P < 0.01), and 74 ± 25 cmH2O · l-1 · s at week 3 (n = 10). The increment with loading was significantly greater during week 1 than during weeks 2 or 3 (P < 0.02). Similar studies were also done in seven full-term infants in the first week of life to evaluate the influence of gestational maturity on ETA stability. Despite a relatively greater drop in intraluminal pressure within the ETA of term vs. preterm infants with loading (P < 0.001), total pulmonary resistance failed to increase (68 ± 21 to 71 ± 32 cmH2O · l-1 · s). These data reveal that ETA instability is present in preterm infants at birth and decreases with increasing postnatal age. Full-term neonates, by comparison, display markedly greater ETA stability in the immediate neonatal period.
- newborn airway
- upper airway mechanics
ASJC Scopus subject areas
- Orthopedics and Sports Medicine
- Physical Therapy, Sports Therapy and Rehabilitation