Presented at the Neonatal Society 2002 Spring Meeting.
Sinha AK, Kempley ST
Department of Child Health, Queen Mary University of London
Neonatal Unit, Royal London Hospital, London E1 1BB, UK
Aim: To determine the reproducibility of flow volume measurements from the right common carotid artery (RCCA) in preterm babies using Doppler ultrasound.
Methods: Studies were performed on 20 spontaneously breathing premature babies (mean weight 1.38 kg, range 0.68 -1.98; corrected gestation 33 weeks, range 28-39). Measurements were performed using a near focus transducer (6-15MHz, Hewlett-Packard). The artery was visualised longitudinally using colour flow and correction made for the angle of insonation. RCCA flow velocity waveforms were obtained using pulse wave Doppler, with intensity weighted mean velocity (IWM) derived from at least 5 waveforms. From a 2D cross sectional image, RCCA diameter was determined from an average of 5 maximum systolic diameters. Flow was calculated as IWM* p (d2/4) * 60. To ascertain inter- and intra-observer reproducibility, two observers alternately performed two measurements on each patient, blinded to each other’s results. Analysis used the method of Bland and Altman (1).
Results: Mean flow in the RCCA was 31 ml/min, equivalent to 22 ml/kg/min. There were no consistent differences between observers. Variability of the measurement is shown in Table 1.
Observer 2 showed evidence of a learning curve (Table 2).
Conclusions: We have been able to perform volumetric measurements of flow volume in the common carotid artery of preterm infants, with no evidence of systematic bias between observers and with reproducibility comparable to other volumetric Doppler methods (2). These measurements may prove useful in the study of factors affecting cerebral blood flow in infants undergoing intensive care.
References
1. Bland JM, Altman DG. Lancet 1986; 1: 307-310
2. Kluckow M, Evans N. Arch Dis Child 2000; 82: F182-187