Time of Onset of Effective Ventilation at Birth

Abstract

A method for serial sampling of umbilical artery blood was described in a previous report. Another study using this method demonstrated that the umbilical artery blood becomes more asphyxial over the first 20 sec after birth, even though up to 5 breaths occurred over this time. In the present study, serial samples of umbilical artery blood were function obtained at slightly later intervals; the first samplings occurred at 11–41 sec and the second samplings at 22–59 sec. From 3 to 11 breaths occurred between birth and the second sampling. Unlike the results in the prior study, many infants showed a rising pH, a falling PCO₂, and a rising oxygen saturation from the first to the second sampling. When the results of one of the prior studies are combined with the present study, it appears that the fifth breath represents the approximate point of reversal of the trend from one of increasing asphyxia to one of improvement in blood gas values. The fifth breath usually occurred at 20–30 sec. It may be advantageous to allow the placental respiration to continue until the pulmonary respiration becomes effective by delaying cord clamping until 5 breaths have occurred or until 30 sec have elapsed.

Delayed umbilical cord clamping at birth has effects on arterial and venous blood gases and lactate concentrations

“…The first several breaths are ineffective for oxygenation due to dead space ventilation with the alveoli remaining unexpanded, but after approximately the fifth breath the pulmonary ventilation is established, i.e. within the first 30 seconds of life 6,7 . Once the ventilation is adequate, P aCO 2 falls rapidly but in contrast to the rapid diffusion of the volatile acids, the fixed acids accumulate and lead to a further decrease in bicarbonate and BE.…”

“…falsely high base deficit). The timing of cord blood clamping therefore seems to be critical for the interpretation of cord blood gases, but only a few small studies have addressed the issue and the results are partly contradictory 6–8 …”

“…The timing of cord blood clamping therefore seems to be critical for the interpretation of cord blood gases, but only a few small studies have addressed the issue and the results are partly contradictory. [6][7][8] The aim of the present study was to investigate the effects of delayed cord clamping on arterial and venous umbilical cord blood pH, PaCO 2 , PO 2 , bicarbonate (HCO -3 ), BE and lactate concentration in alert term newborns.…”

Human Umbilical Vessel Diameters and Blood Gas Tensions in the First Two Minutes after Delivery

“…U llrich and A ckerman [36] found no increase in oxygen saturation, at least until after the fifth breath. C hou et al [3] reported a rise between serial samples taken within the first minute after delivery.…”

Fetal Breathing Movements and Changes at Birth

“…Factors implicated in establishing continuous respiration at birth include asphyxia, vagal afferent traffi c related to respiratory/ circulatory transitions, umbilical cord occlusion, cutaneous cooling, and the rise in PaO 2 with the fi rst postnatal breath [ 5 ]. The onset of continuous respiration at birth depends neither upon afferent input from the carotid sinus and vagus nerves [ 51 ] nor interruption of the umbilical circulation [ 52 ]. Furthermore, it can occur in noncyanotic (nonasphyxiated) human infants or following a prolonged single inspiratory effort or asphyxial gasping [ 53 ].…”