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Dynamic behavior of respiratory system during nasal continuous positive airway pressure in spontaneously breathing premature newborn infants
Author(s) -
Magnenant E.,
Rakza T.,
Riou Y.,
Elgellab A.,
Matran R.,
Lequien P.,
Storme L.
Publication year - 2004
Publication title -
pediatric pulmonology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.866
H-Index - 106
eISSN - 1099-0496
pISSN - 8755-6863
DOI - 10.1002/ppul.10445
Subject(s) - medicine , lung volumes , functional residual capacity , tidal volume , continuous positive airway pressure , respiratory system , anesthesia , ventilation (architecture) , respiratory rate , plethysmograph , respiratory minute volume , work of breathing , positive end expiratory pressure , lung , mechanical ventilation , heart rate , blood pressure , mechanical engineering , obstructive sleep apnea , engineering
The end‐expiratory lung‐volume level of premature newborn infants is maintained above passive resting volume during active breathing, through the combination of reduced time constant and high respiratory rate. To determine whether nasal continuous positive airway pressure (NCPAP) alters this characteristic dynamic breathing pattern, we studied the effects of various NCPAP levels on the dynamic elevation of end‐expiratory lung volume level (ΔEELV) in spontaneously breathing premature newborn infants, using respiratory inductive plethysmography (RIP). Eleven premature newborn infants with moderate respiratory failure were included. NCPAP levels were set in a random order to 0, 2, 4, and 6 cm H 2 O. Tidal volume (Vt), rib‐cage contribution to Vt (%RC), phase angle between abdominal and thoracic motions (θ), respiratory rate (RR), and inspiratory and expiratory times (Ti and Te) were continuously recorded by RIP. The slope of the linear part of the expiratory flow‐volume relation was extrapolated up to zero flow level to evaluate the dynamic elevation of the functional residual capacity (FRC) (ΔEELV). The time‐constant of the respiratory system (τ RS ) was calculated as the slope of the linear part of the expiratory flow‐volume loop. At NCPAP = 6 cm H 2 O, ΔEELV reached 0.6 ± 0.2 times the Vt at NCPAP = 0 cm H 2 O. An increase in NCPAP level resulted in a significant decrease in ΔEELV ( P < 0.01). A decrease in ΔEELV during NCPAP was associated with a significant increase in Te from 0.62 ± 0.13 sec at NCPAP = 0 cm H 2 O to 0.80 ± 0.07 sec at NCPAP = 6 cm H 2 O ( P < 0.05), and a decrease in τ RS from 0.4 ± 0.1 sec at NCPAP = 0 cm H 2 O to 0.24 ± 0.04 sec at NCPAP = 6 cm H 2 O ( P < 0.01). These results indicate that the characteristic spontaneous breathing pattern causing a dynamic elevation of FRC is abolished by NCPAP. We speculate that the dynamic volume‐preserving mechanisms resulting from expiratory flow braking are no longer required during NCPAP, as the constant pressure may passively elevate FRC. Pediatr Pulmonol. 2004; 37:485–491. © 2004 Wiley‐Liss, Inc.