BACKGROUND: The distribution of ventilation during HFV is asynchronous, non-homogeneous and frequency dependent. We hypothesized that differences in the regional distribution of ventilation at different oscillatory frequencies may affect gas exchange efficiency. METHODS: We studied 15 newborn infants with a median (IQR) gestational age of 28.9 (26.4-30.3) weeks and body weight of 1.0 (0.8-1.4) kg. Five ventilation frequencies (5, 8, 10, 12, 15 Hz) were tested, keeping carbon dioxide diffusion coefficient constant. The displacements of 24 passive markers placed on the infant's chest wall were measured by optoelectronic plethysmography. We evaluated the amplitude and phase shift of displacements of single markers placed along the midline and the regional displacements of the chest wall surface. RESULTS: Blood gases were unaffected by frequency. Chest wall volume changes decrease from 1.6 (0.4) mL/kg at 5 Hz to 0.7 mL/kg at 15 Hz. At all frequencies the abdomen (AB) oscillated more markedly than the ribcage (RC). The mean (SD) AB/RC ratio was 1. 95 (0.7) at 5 Hz, increased to 2.1 (1.3) at 10 Hz and then decreased to 1.1 (0.5) at 15 Hz (p-value < 0.05 vs 10 Hz). Volume changes in the AB lagged the RC and this phase shift increased with frequency. CONCLUSION: The abdomen oscillated more than the ribcage at all frequencies. Regional oscillations were highly inhomogeneous up to 10 Hz and they became progressively more asynchronous with increasing frequency. When carbon dioxide diffusion coefficient is held constant, such differences in regional chest wall expansion do not affect gas exchange.

REGIONAL DISTRIBUTION OF CHEST WALL DISPLACEMENTS IN INFANTS DURING HIGH FREQUENCY VENTILATION (HFV)

Zannin, Emanuela;Veneroni, Chiara;Dellaca, Raffaele
2019-01-01

Abstract

BACKGROUND: The distribution of ventilation during HFV is asynchronous, non-homogeneous and frequency dependent. We hypothesized that differences in the regional distribution of ventilation at different oscillatory frequencies may affect gas exchange efficiency. METHODS: We studied 15 newborn infants with a median (IQR) gestational age of 28.9 (26.4-30.3) weeks and body weight of 1.0 (0.8-1.4) kg. Five ventilation frequencies (5, 8, 10, 12, 15 Hz) were tested, keeping carbon dioxide diffusion coefficient constant. The displacements of 24 passive markers placed on the infant's chest wall were measured by optoelectronic plethysmography. We evaluated the amplitude and phase shift of displacements of single markers placed along the midline and the regional displacements of the chest wall surface. RESULTS: Blood gases were unaffected by frequency. Chest wall volume changes decrease from 1.6 (0.4) mL/kg at 5 Hz to 0.7 mL/kg at 15 Hz. At all frequencies the abdomen (AB) oscillated more markedly than the ribcage (RC). The mean (SD) AB/RC ratio was 1. 95 (0.7) at 5 Hz, increased to 2.1 (1.3) at 10 Hz and then decreased to 1.1 (0.5) at 15 Hz (p-value < 0.05 vs 10 Hz). Volume changes in the AB lagged the RC and this phase shift increased with frequency. CONCLUSION: The abdomen oscillated more than the ribcage at all frequencies. Regional oscillations were highly inhomogeneous up to 10 Hz and they became progressively more asynchronous with increasing frequency. When carbon dioxide diffusion coefficient is held constant, such differences in regional chest wall expansion do not affect gas exchange.
2019
Carbon dioxide diffusion coefficient; High Frequency Oscillatory Ventilation; Infants; Optoelectronic plethysmography
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/1075077
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