Variability of End-Expiratory Lung Volume in Premature Infants

Abstract

Background: Analysis of breath-to-breath variability of respiratory characteristics provides information on the respiratory control. In infants, the control of end-expiratory lung volume (EELV) is active and complex, and it can be altered by respiratory disease. The pattern of EELV variability may reflect the behavior of this regulatory system. Objectives: We aimed to characterize EELV variability in premature infants, and to evaluate variability pattern changes associated with respiratory distress and ventilatory support. Methods: EELV variations were recorded using inductance plethysmography in 18 infants (gestational age 30–33 weeks) during the first 10 days of life. An autocorrelation analysis was conducted to evaluate the ‘EELV memory’, i.e. the impact of the characteristics of one breath on the following breaths. Results: In infants without respiratory symptoms, EELV variability was high, with large standard deviations of EELV. Autocorrelation was found to be significant until a median lag of 7 (interquartiles: 4–8) breaths. Autocorrelation was markedly prolonged in patients with respiratory distress or ventilatory support, with a higher number of breath lags with significant autocorrelation (p < 0.01) and higher autocorrelation coefficients (p < 0.05). Conventional assisted ventilation does not re-establish a healthy EELV profile and is associated with lower respiratory variability. Conclusions: In premature infants, EELV variability pattern is modified by respiratory distress with a prolonged ‘EELV memory’, which suggests a greater instability of the control of EELV.

Neurally adjusted ventilatory assist improves patient–ventilator interaction in infants as compared with conventional ventilation

“…A decreased variability is associated with respiratory disease in adults (29) and in infants (22), and a lower variability is a predictor of weaning failure (30). In this study, the patients exhibited a large variability of their ventilatory drive whatever the mode, as reflected by large coefficient of variation of peak Edi.…”

“…However, the dispersion of delays in PCV and PSV reflects that the cycling off is dependent on conditions that are varying cycle by cycle. These varying parameters include patient inspiratory effort, neural inspiratory and expiratory time, the level of assist, the time constant of the Articles NAVA in infants respiratory system, and the level of end-expiratory lung volume (22,23). Up to one-fifth of the breaths during conventional ventilation showed cycling off before the peak of the Edi.…”

The variability of pulmonary gas exchange and respiratory pattern

“…Most studies on this problem have been carried out using variability analysis in the HF band corresponding to the respiratory rate. A theory was formed in the 1990s that the variability of the respiratory pattern found in both experimental animals and humans reflects the dynamic interaction between the chemoreflex and mechanoreflex feedback mechanisms regulating the ventilatory function of the external respiration [10,14,15]. It was shown in a number of studies on the vari ability of the pulmonary ventilation function of the lung, estimated using statistical criterions of chaos, that the chemoreceptor regulation is the main factor determining the variability [16,17].…”

Setting the Ventilator in the NICU

“…Whole-body plethysmography (Stocks et al 2001 ) and gas dilution (Sivan et al 1990 ;Vilstrup et al 1992 ), both of which give absolute values for EELV, are not appropriate for repeated measurements in a clinical setting. Other methods, including respiratory inductance plethysmography (Adams 1996 ;Emeriaud et al 2010 ), fi bre-optic plethysmography (Davis et al 1999 ) and electrical impedance tomography (Frerichs et al 2001 ), allow measurement not of absolute volume but of change in EELV relative to a baseline condition, and only with prior calibration can a gas volume change in mL be derived. Despite these limitations, a great deal of information has been obtained from experimental studies in which EELV has been measured, either at the bedside or in the laboratory, as alterations in PEEP have been made.…”