Pulmonary mechanics and energetics of normal, non-ventilated low birthweight infants.
Pulmonary mechanics and energetics were determined in 33 healthy low birthweight infants (less than 1,500 g, 28-34 weeks gestation) who had never received ventilatory support. Tidal volume, dynamic pulmonary compliance, pulmonary resistance, pressure-volume relationships, and tidal flow-volume measurements were obtained by pneumotachography and the esophageal balloon technique. Standardized data collection and software data analysis by least mean squares technique yielded data at 0.5, 1, 2, and 4 weeks postnatally, as a function of gestational age (less than 30, 30-32, and greater than 32 weeks gestation). Relatively stable values were obtained for tidal volume and minute ventilation (normalized for body weight); these were associated with values of peak-to-peak esophageal pressure significantly (P less than 0.001) increasing from 4.4 +/- 0.3 SEM cmH2O at 0.5 weeks to 8.1 +/- 0.8 SEM cmH2O at 4 weeks of age. Dynamic pulmonary compliance ranged from 2.0 to 2.4 mL/cmH2O in the first 4 weeks of life. When normalized for weight, compliance decreased with age, which may suggest a slower pulmonary maturation as compared to increase of body weight. Mean pulmonary resistance decreased from 62.9 cmH2O/L/s at less than 30 weeks gestation to 32.5 cmH2O/L/s at greater than 32 weeks gestation, 0.5 weeks postnatally. Pulmonary resistance peaked at 2 weeks postnatally (P less than 0.05), at all gestational ages, then decreased. Changes in pulmonary mechanics resulted in increasing resistive work of breathing. Our findings suggest a postnatal retardation of pulmonary and airway growth, relative to gestation maturation. These data can provide an objective base of comparison for data in sick, low birthweight neonates.
Abbasi
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Section on Newborn Pediatrics, Pennsylvania Hospital, Philadelphia 19107.
Bhutani
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VK
D000403:Airway Resistance / Q000502:physiology; D006801:Humans; D007230:Infant, Low Birth Weight / Q000502:physiology*; D007231:Infant, Newborn; D016018:Least-Squares Analysis; D008168:Lung / Q000502:physiology*; D008170:Lung Compliance / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology*; D013990:Tidal Volume / Q000502:physiology; D014939:Work of Breathing