Expired tidal volumes measured by hot-wire anemometer during high-frequency oscillation in preterm infants

• Published in: Pediatric pulmonology 2006-05, Vol.41 (5), p.428-433
• Main Authors: Zimová-Herknerová, Magdalena, Plavka, Richard
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Breath Tests; high-frequency oscillatory ventilation; High-Frequency Ventilation; Humans; Infant, Newborn; Infant, Premature; Medical sciences; Pneumology; preterm infant; Tidal Volume
• ISSN: 8755-6863; 1099-0496
• DOI: 10.1002/ppul.20367

We sought to determine the normocapnic values of expiratory tidal volume measured by hot‐wire anemometer, and to evaluate how often expiratory tidal volume exceeds estimated anatomical dead space during high‐frequency oscillatory ventilation (HFOV) in preterm infants. We also sought to determine the relationship between expiratory tidal volume and other respiratory parameters. The neonatal respiration monitor SLE 2100 VPM, a hot‐wire anemometer, was used to measure expired tidal volume (VT,E) in patients ventilated by the Sensormedics 3100A during routine clinical use of HFOV. Two hundred and fourteen simultaneous measurements of PaCO2, VT,E, fraction of inspired oxygen (FiO2), continuous distending pressure (CDP), frequency, and amplitude were obtained from 28 patients. The median birth weight was 852 g (range, 435–3,450 g), and median gestational age was 27.2 weeks (range, 23.3–41.0 weeks). One hundred and eighteen (55%) normocapnic measurements, 42 (20%) hypocapnic measurements, and 54 (25%) hypercapnic measurements were recorded in which the median VT,E was 1.67 ml/kg (95% confidence interval (CI), 1.55–1.79), 1.94 ml/kg (95% CI, 1.74–2.14), and 1.54 ml/kg (95% CI, 1.42–1.66), respectively. The measured VT,E exceeded 2.0 ml/kg in 30 instances of normocapnic VT,E (14%) and 54 of all VT,E (25%), and 3 ml/kg only in 7 (3%) and 11 (5%) instances of normocapnic and all VT,E. There was a significant difference in median normocapnic VT,E obtained when FiO2 was between 0.21–0.35, compared to values obtained when FiO2 was 0.36–1.0 (1.61 ml/kg (95% CI, 1.52–1.70) vs. 2.06 ml/kg (95% CI, 1.93–2.19), P 47 should predict hypercapnia in 81% of cases. In conclusion, expired tidal volume measurement by heated double‐wire anemometer sensor is feasible, provides useful real‐time information about tidal volume changes, and may improve the clinical management of HFOV. Pediatr Pulmonol. 2006; 41:428–433. © 2006 Wiley‐Liss, Inc.