Functional importance of the Breuer-Hering reflex

Laryngeal muscle activities with cerebral hypoxia-ischemia in newborn lambs

This study tested the hypotheses that (1) acute cerebral hypoxia-ischemia changes laryngeal adductor, laryngeal abductor, and diaphragmatic activities, resulting in central apnea with laryngeal closure; and (2) these laryngeal muscle activities act to maintain absolute lung volume. The respiratory pattern was determined in three asphyxiated, awake preterm lambs after cesarean section birth and in 12 awake, term lambs, with normal lung function, after induction of acute cerebral hypoxia-ischemia by occlusion of the brachiocephalic artery. Electrocorticogram activity, flow, volume, electromyograms of laryngeal abductor and adductor muscles and diaphragm, and, in the term lambs, trans-upper airway pressure and carotid blood flow were recorded. With either preterm birth asphyxia or induced acute cerebral hypoxia-ischemia, minute ventilation initially increased, and then hypopnea occurred. During the hypopnea, laryngeal adductor activity was prominent, accompanied by an increased upper airway pressure and a maintained/raised absolute lung volume. Thus, when acute hypoxia-ischemia limited to the upper body is induced in lambs with normal lung function, expiratory laryngeal adduction with closure of the upper airway occurs and likely functions to aid autoresuscitation.

Effects of uneven elastic loads on breathing pattern of anesthetized and conscious men

In anesthetized subjects rib cage strapping (RCS) did not change tidal volume (VT) and increased ventilation (V), whereas abdomen strapping (AS) markedly decreased VT and V. Both kinds of strapping decreased expiratory duration (TE), but did not change inspiratory duration (TI) and breathing rate. RCS and AS decreased lung volume by about 200 ml and increased the elastance of the repiratory system by 12 cm H2O/1 and 9 CM H20/l, repectively. The changes produced are mainly due to mechanical factors, although reflexes also seem to be operating in some cases. In conscious subjects RCS decreased VT, TI, TE and did not change V, whereas AS did not change these parameters. The different changes in conscious and anesthetized subjects show the effects of cortical influences, which also partly explain the differen effects elicited in conscious subjects by RCS and AS. The effects produced by RCS are mainly due to the sensation of hindrance to rib cage expansion, rather than to that of rib cage squeezing, as shown by experiments of RCS without reduction of rib cage volume.