The patient group that defines Practice Pattern G are those neonates who have impaired ventilation, respiration/gas exchange, and aerobic capacity/endurance associated with respiratory failure.1 Patients are included in this practice pattern if they are younger than 4 months and present with the following risk factors or pathophysiologic processes:
- Abdominal thoracic surgeries
- Apnea and bradycardia
- Bronchopulmonary dysplasia
- Congenital anomalies
- Respiratory distress syndrome
- Meconium aspiration syndrome
- Neurovascular disorders
- Rapid desaturation with movement or crying and the following impairments, functional limitations, and disabilities:
- Abnormal pulmonary responses to activity
- Impaired airway clearance
- Impaired cough
- Impaired gas exchange
- Intercostal or subcostal retraction on inspiration
- Paradoxical or abnormal breathing pattern at rest or with activity
- Physiological intolerance of routine care
Patients older than 4 months are excluded from this pattern.
The first edition of this chapter was written by M. Kathleen Kelly.
Fetal to Extrauterine Transition
The transition to extrauterine life presents one of the greatest anatomic and physiologic challenges faced by an infant. At birth, a series of events must occur in order to support adequate lung and cardiac function during the conversion from liquid to air breathing and to establish parallel pulmonary and systemic circulation.2 Throughout fetal life, circulatory functions take place primarily in the placenta with relatively little blood flow through the lungs. During delivery, however, various bioch and structural changes must be initiated rapidly in order to ensure the transition from fetal to neonatal circulation. The key elements in the birth transition are the shift from maternally dependent oxygenation to continuous respiration; a switch from fetal circulation to mature circulation; the onset of independent glucose metabolism; the onset of independent oral feeding, thermoregulation, and the regulation of hormonal control of growth.3
At birth, the airways are partially filled with fluid that has been derived from the amniotic sac, tracheal glands, and lung tissue.4 The presence of this fetal lung fluid is crucial to the development of the respiratory system; however, its clearance is equally essential for the respiratory adaptations to air breathing. Within seconds of emergence from the uterine environment and the initiation of breathing, air rapidly replaces the intra-alveolar fluid. Normally, newborns rapidly establish the critical negative pressure needed to expand the alveoli and then are able to maintain adequate respiratory function and good aeration. It is only during the last few weeks of prenatal development that the lung tissue becomes fully capable of autonomous respiration—that is, gas exchange (see Table 21-1). At this time in development, the alveolar–capillary membrane thins out enough to permit gas exchange. In addition, the process of alveolarization is initiated and continues to be completed postnatally. These structural changes in the lung result in increased lung volumes and increased surface area for gas exchange. During prenatal development, a number of factors can negatively influence or affect lung development resulting in primary pulmonary hypoplasia. Secondary pulmonary hypoplasia, which ...