Respiratory mechanics in spontaneously breathing term and preterm neonates.
The compliance (Crs), resistance (Rrs) and passive time constant (tau rs) of the respiratory system were determined by the single-breath method (sb) in 24 healthy term and preterm newborns. In 22 of them, Crssb was compared to the slope of the pressure-volume curve determined by the multiple occlusion technique (mo), which is not dependent on the assumption of a linear flow-volume relationship. Crssb and Rrs correlated significantly with body weight (kg): Crssb = 0.56 x kg + 1.22 (r = 0.67); Rrs = -20.1 x kg + 134.6 (r = -0.68). No difference in Crs and Rrs between prone and supine positions was found. tau rs was not significantly different between premature (0.21 +/- 0.06 s) and full-term infants (0.21 +/- 0.05 s). Crssb was significantly higher than Crsmo in premature babies (2.27 +/- 0.41 ml.cm H2O-1 vs. 1.98 +/- 0.47 ml.cm H2O-1. This difference may be explained by a continuous braking of expiratory airflow after release of the occlusion, or more likely, by a difference in the lung volume at which Crssb and Crsmo are measured. However, the difference between Crssb and Crsmo (approximately 15%) is in the same range as the intrasubject variability, and is meaningless compared to the alterations of respiratory mechanics observed during neonatal ventilatory disorders. Therefore, the single-breath method appears to be a suitable and noninvasive method to measure respiratory mechanics in nonintubated prematures.
Haouzi
P
P
Laboratoire de Physiologie, Faculté de Médecine de Nancy, Unité INSERM 272, France.
Marchal
F
F
Crance
J P
JP
Monin
P
P
Vert
P
P
D000403:Airway Resistance; D006801:Humans; D007231:Infant, Newborn / Q000502:physiology*; D007234:Infant, Premature / Q000502:physiology*; D008170:Lung Compliance; D012123:Pulmonary Ventilation; D015656:Respiratory Mechanics; D012890:Sleep / Q000502:physiology