Influence of preterm onset of inspiration on tidal breathing parameters in infants with and without CLD

https://doi.org/10.1016/S1569-9048(03)00029-6Get rights and content

Abstract

The preterm onset of inspiration (POI) is a well-known breathing strategy in newborns to increase their end-expiratory lung volume. The aim of this study was to investigate to which extent POI is related to tidal breathing (TB) parameters in healthy neonates (n=54) and infants with chronic lung diseases (CLD, n=45) with same postconceptional age. Using the deadspace free flow-through technique, 10–60 consecutive breaths were evaluated during quiet sleep and POI was derived from the averaged flow–volume loop considering the end-expiratory flow level. Respiratory rate (RR), ventilation (V̇e) and peak flows were significantly higher in CLD infants compared with controls. The incidence of POI did not differ significantly between both patient groups. POI is strongly associated with TB parameters describing the shape of flow profiles or flow–volume loops. In contrast, TB parameters, which depend only on breathing depth and rate (e.g., RR, Vt, V̇e), were not significantly associated. The study shows that in infants TB parameters describing the flow profile may reflect differences in breathing strategy rather than impaired respiratory functions.

Introduction

An infant's breathing pattern, measured during tidal breathing (TB), contains physiological information about respiratory control and pulmonary mechanics. For a quantitative evaluation of the breathing pattern, TB is commonly measured at the airway opening using a pneumotachograph (PNT) connected to a face mask (Bates et al., 2000). Since this technique can be used relatively easy in sick neonates at the bedside, TB measurements are used increasingly for clinical (Carlsen et al., 1997, Schmalisch et al., 2001b, Williams et al., 2000) and research purposes (Stocks et al., 1994, Ueda et al., 1999, van der Ent et al., 1998).

However, TB measurements in infancy are influenced by the peculiarities of the breathing strategies in early postnatal age. Adults and older infants breathe from an end-expiratory lung volume determined by the opposing recoil of the lungs and chest wall. Neonates have a highly compliant chest wall which may cause several problems during breathing, e.g., small end-expiratory lung volume, low oxygen stores, and a high risk for airway occlusion and atelectasis (Stark et al., 1987). Therefore, infants compensate for this mechanical disadvantage by actively maintaining lung volume above the resting volume. Kosch and Stark (1984) have shown in the past that a preterm onset of inspiration (POI) before the complete expiration provide a neonatal breathing strategy to dynamically increase the lung volume.

Different techniques can be used to detect a POI. In newborns, the onset of inspiration is commonly measured by surface diaphragmatic electromyography (Fox et al., 1988), by intrathoracic-impedance measurements (Nikischin et al., 1996) or by pneumotachography. In a clinical study investigating synchronized mechanical ventilation, Hummler et al. (1996) have recently shown that a flow–volume signal is less prone to artifacts and chest wall distortions compared with other techniques. Furthermore, it is well known from the measurement of respiratory mechanics by occlusion tests (LeSouef et al., 1984) that a POI can be recognized from the TB flow–volume loop (TBFVL) by a sharp break of the end-expiratory flow as shown in Fig. 1.

Modern algorithms for infant respiratory function testing enable us to derive a great variety of TB parameters (Schmalisch et al., 1996), but the relation of a POI with different parameters was not yet investigated in detail. We hypothesize that a POI is associated with changes in different TB parameters. Therefore, the aim of this study was to investigate the relation of a POI with the most commonly measured TB parameters in comparison to the differences in TB parameters between healthy neonates and infants with chronic lung diseases (CLD) with the same postconceptional age. At present, infants with CLD represent the most important group for respiratory function testing in newborns and in early infancy (Bancalari, 2001, Jobe and Ikegami, 2000).

Section snippets

Subjects

In a prospective clinical study over a 25-month period, TB measurements were performed in 54 healthy neonates and 45 infants with CLD defined by mechanical ventilation >48 h and oxygen dependence at day 28 of life (Bancalari, 2001). All measurements were performed in the respiratory function laboratory of the Clinic of Neonatology at Humboldt University (Charité). Inclusion criteria for this study were the postconceptional age <50 weeks, spontaneous breathing, quiet sleep according to Prechtl

Results

Between both patient groups, there were significant differences (P<0.01) in the shape of the expiratory limb of the TBFVL (Fig. 2). In CLD infants, the incidence of concave shapes was 27% and nearly 10 times higher than in healthy neonates (3%).

The comparison of TB parameters measured in both patient groups is shown in Table 2. There were statistically significant differences between both patient groups except for tidal volume and end-expiratory flow (TEF25) related to body weight. The largest

Discussion

The main goal of this study was to investigate the relation of a POI with different TB measurements. We found that a POI is related mainly to those TB parameters describing the flow profile or the shape of the TBFVL (e.g., the extensively investigated parameter tptef/te). In contrast, conventional TB parameters, which describe only rate and depth of breathing (RR, Vt and V̇e), are relatively independent on POI.

The mechanisms explaining the association between POI and TB pattern in newborns are

Acknowledgements

The authors thank Dr. Mario Schmidt for his support in the development of the software and Mrs. Silke Schmidt for her assistance in respiratory function testing. They also gratefully acknowledge Prof. Colin Morley (Melbourne) for the critical review of the manuscript. This work was supported by the German Ministry for Education and Research, project “Perinatal Lung” (grant 01-ZZ-9511).

References (28)

  • K.C.L. Carlsen et al.

    Determinants of tidal flow volume loop indices in neonates and children with and without asthma

    Pediatr. Pulmonol.

    (1997)
  • B. Foitzik et al.

    Leak measurements in spontaneously breathing premature newborns by using the flow-through technique

    J. Appl. Physiol.

    (1998)
  • R.E. Fox et al.

    Control of inspiratory duration in premature infants

    J. Appl. Physiol.

    (1988)
  • M. Gappa et al.

    Passive respiratory mechanics: the occlusion techniques

    Eur. Respir. J.

    (2001)
  • Cited by (17)

    • Tidal breathing flow profiles during sleep in wheezing children measured by impedance pneumography

      2020, Respiratory Physiology and Neurobiology
      Citation Excerpt :

      Intercostal atony together with a lower diaphragm tone decreases the functional residual capacity (FRC) (Henderson-Smart and Read, 1979). This decrease has been linked to uninterrupted or late interruption of expiration (Morris et al., 1998; Schmalisch et al., 2003). The overnight decreasing trend in the REM bin medians, which is shared by TPTEF, TPTEF/TE, VPTEF/VE, TEF50/PTEF, and TEF25/PTEF, may have been caused by a shortening of post-inspiration inspiratory activity (PIIA) during the night.

    • Evaluation of Pulmonary Function in the Neonate

      2017, Fetal and Neonatal Physiology, 2-Volume Set
    • Evaluation of Pulmonary Function in the Neonate

      2011, Fetal and Neonatal Physiology E-Book, Fourth Edition
    • Impaired somatic growth and delayed lung development in infants with congenital diaphragmatic hernia-evidence from a 10-year, single center prospective follow-up study

      2009, Journal of Pediatric Surgery
      Citation Excerpt :

      The latter is surprising and differs from the changes in the breathing pattern seen in infants with chronic lung disease (CLD) [15]. In CLD infants, commonly, an increased RR but no significant changes in VT related to body weight was seen [16-18]. An interesting question is the relationship between delayed somatic growth and the work of breathing in CDH infants.

    • Tracheal tube airleak in clinical practice and impact on tidal volume measurement in ventilated neonates

      2011, Pediatric Critical Care Medicine
      Citation Excerpt :

      This may be explained by technical problems associated with leak measurement based on the difference between inspired and expired volumes. This form of leak measurement is affected by several technical factors (e.g., differences in the transfer characteristics of the pneumotach on inspiration and expiration (30), or quality of breath detection (31) and physiologic factors (e.g., instability of end-expiratory lung volume [32] or changes in respiratory compliance [33]). The most important cause of the high intersubject variability shown in Figure 3 is the superimposition of the flow signal by spontaneous breathing.

    View all citing articles on Scopus
    View full text