Page 103 - Physiological based CPAP for preterm infants at birth Tessa Martherus

High-CPAP does not impede cardiovascular changes at birth in preterm sheep
Baseline JVP levels were measured for each CPAP level over the first 30 min after birth, to avoid pressure changes associated with movement and breathing. Baseline JVP levels were similar at CPAP levels of 5 cmH2O (8.0 (5.1-12.4)), 8 cmH2O (9.4 (5.3-13.4)), and 15 cmH2O (8.6 (6.9-10.5)) and were also similar during iPPV 5.4 ((4.9-9.4) mmHg, p=0.571). However, JVP levels were increased, by an average of 3.8 (1.6-8.3) mmHg, when lambs were actively exhaling or utilizing expiratory braking maneuvers (indicated by airway pressures above CPAP). These activities resulted in maximum JVPs of 12.3 (5.9-17.3) mmHg (Figure 5A).
Baseline UTP levels were measured for each CPAP level throughout both phases of the experiment (0-45 min) to avoid pressure changes associated with movement and breathing.
When a CPAP of 5 cmH2O was given, pressures measured at the CPAP interface (nasal prongs)
were similar to those measured in the upper trachea, below the larynx (CPAP vs. UTP, 5
cmH2O: 5.4 (5.1-5.6) vs. 5.0 (4.0-7.4), p=0.953). Similarly, at a CPAP of 8 cmH2O the pressures
measure at the CPAP interface (8.3 (8.1-8.5) cmH2O) were similar to UTPs (8.1 (6.0-9.8)
cmH2O; p=0.715). However, when 15 cmH2O of CPAP was applied, UTP was lower than the
pressure applied at the CPAP interface (12.6 (10.5-14.5) vs. 15.2 (14.9-15.5) cmH2O, respectively, p=0.013). Similarly, during iPPV, mean airway pressures measured in the UT
were significantly less than that measured at the CPAP interface (12.5 (8.5-18.2) vs. 18.6 (12.2-
22.2), respectively, p=0.028; Figure 5). 4
Figure 5. Jugular venous pressure and upper tracheal pressure. a) Jugular venous pressures (JVP; median (Q1-Q3)) measured during the first 30 minutes after birth at different CPAP levels and during iPPV as well as the maximum (Max) pressure achieved and the change in pressure (Delta) associated with body movements or forced expirations; n= the number of animals during CPAP or iPPV, whereas n= the number of breaths with active forced expiration. JVPs were compared between groups using Kruskal-Wallis Tests. b) Pressures (median (Q1-Q3)) measured simultaneously in the upper trachea (UTP, filled squares) and CPAP interface (nasal prongs, filled circles) during CPAP and iPPV throughout the entire experiment (30 + 15 minutes) n=animal number. Pressures were compared using Wilcoxon Signed-Rank Tests. Dotted horizontal line indicates 5, 8 and 15 cmH2O CPAP.
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