The American Academy of Pediatrics and the American College of Obstetricians and Gynecologists (2012) recommend attendance at delivery of at least one person whose primary responsibility is the neonate and who is capable of initiating resuscitation that includes intubation, vascular access, and medication administration. This usually is a pediatrician, nurse practitioner, anesthesiologist, nurse anesthetist, or specially trained nurse. However, in their absence, the responsibility for neonatal resuscitation falls to the obstetrical attendant. Thus, obstetricians should be well versed in measures for immediate care of the newborn.
Initiation of Air Breathing
Immediately following birth, the infant must promptly convert to air breathing as the fluid-filled alveoli expand with air and pulmonary perfusion is established. The newborn begins to breathe and cry almost immediately after birth, which indicates establishment of active respiration. Some factors that appear to influence the first breath include:
Physical stimulation—examples include handling the neonate during delivery.
Oxygen deprivation and carbon dioxide accumulation—these serve to increase the frequency and magnitude of breathing movements both before and after birth (Dawes, 1974).
Thoracic compression—this occurs during pelvic descent, following which vaginal birth forces fluid from the respiratory tract in volume equivalent to approximately a fourth of the ultimate functional residual capacity (Saunders, 1978).
Aeration of the newborn lung does not involve the inflation of a collapsed structure, but instead, the rapid replacement of bronchial and alveolar fluid by air. After delivery, the residual alveolar fluid is cleared through the pulmonary circulation and to a lesser degree, through the pulmonary lymphatics (Chernick, 1978). Delay in fluid removal from the alveoli probably contributes to the syndrome of transient tachypnea of the newborn (TTN) (Guglani, 2008). As fluid is replaced by air, compression of the pulmonary vasculature is reduced considerably, and in turn, resistance to blood flow is lowered. With the fall in pulmonary arterial blood pressure, the ductus arteriosus normally closes (Fig. 7-8, The intricate nature of the fetal circulation is evident).
High negative intrathoracic pressures are required to bring about the initial entry of air into the fluid-filled alveoli. Normally, from the first breath after birth, progressively more residual air accumulates in the lung, and with each successive breath, lower pulmonary opening pressure is required. In the normal mature newborn, by approximately the fifth breath, pressure-volume changes achieved with each respiration are very similar to those of the adult. Thus, the breathing pattern shifts from the shallow episodic inspirations characteristic of the fetus to regular, deeper inhalations (Chap. 17, Fetal Breathing). Surfactant, which is synthesized by type II pneumocytes and already present in the alveoli, lowers alveolar surface tension and thereby prevents lung collapse. Insufficient surfactant, common in preterm infants, leads promptly to respiratory distress syndrome, which is described in Chapter 34 (Respiratory Distress Syndrome).