Doppler assessment of pulmonary artery pressure in neonates at risk of chronic lung disease

Abstract

Aim: To evaluate the pulmonary artery pressure (PAP) change in very low birth-weight (VLBW) infants at risk of chronic lung disease (CLD).

Methods: The time to peak velocity:right ventricular ejection time (TPV:RVET) ratio calculated from the pulmonary artery Doppler waveform, which is inversely related to PAP, was used. The TPV:RVET ratio was corrected for different heart rate (TPV:RVET(c)). Seventy three VLBW infants studied on days 1, 2, 3, 7, 14, 21 and 28 were enrolled for the analysis.

Results: Twenty two infants developed CLD with a characteristic chest radiograph at day 28. Fifty one did not, of whom 17 were oxygen dependent on account of apnoea rather than respiratory disease, and 34 were non-oxygen dependent. The TPV:RVET(c) ratio rose progressively in all three groups over the first three days of life, suggesting a fall in PAP. In the oxygen and non-oxygen dependent groups, the mean (SD) ratio rose to 0.53 (0.09) and 0.57 (0.09), respectively, on day 7, then remained relatively constant thereafter. The CLD group rose more slowly after day 3 and had a significantly lower mean ratio from day 7 onwards compared with the other two groups (day 7: P < 0.001, days 14-28: P < 0.0001), and fell significantly from 0.47 (0.11) on day 7 to 0.41 (0.07) on day 28 (P = 0.01), suggesting a progressive rise in PAP. The mean (SD) ratios at day 28 of all infants were: CLD group 0.41 (0.07); oxygen dependent group 0.66 (0.15); and the non-oxygen group 0.67 (0.11). The CLD group had a significantly lower ratio than the oxygen dependent group and the non-oxygen group (P < 0.0001). Using the TPV:RVET(c) ratio of < 0.46, infants at risk of developing CLD could be predicted on day 7 (predictive value 82.8%, sensitivity 54.5%, specificity 94.1%).

Conclusion: The non-invasive assessment of PAP using the TPV:RVET(c) ratio may be useful in the longitudinal monitoring of PAP change in VLBW infants, and for prediction of chronic lung disease.

Figure 1

Mean (SD) TPV:TVET(c) ratio in the three groups according to day of study. Broken line represents lower limit of normal range for TPV:RVET(c) = 0.46; CLD, chronic lung disease; OD oxygen dependent; N-OD non-oxygen dependent. *P<0.001; **P<0.0001 (differences between CLD and other two groups).

Figure 2

TPV:RVET (c) ratio for each group at day 28. Broken line represents lower limit of normal range for TPV:RVET(c)= 0.46. Mean ratio for each group is shown by horizontal black line. The mean of the CLD groups is significantly different from that of the OD and N-OD groups (P<0.001). The means of these latter groups were not signficantly different.