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Diaphragmatic and Respiratory Neuronal Activities during the Restart of Breathing after Hypocapnic Apnea
Author(s) -
Orem John M,
Fraigne Jimmy J,
Lovering Andrew T,
Vidruk Edward H
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a558-d
Subject(s) - apnea , medicine , hypercapnia , tonic (physiology) , anesthesia , diaphragmatic breathing , respiratory system , hyperventilation , control of respiration , ventilation (architecture) , alternative medicine , pathology , mechanical engineering , engineering
It is not known how breathing stops in response to mechanical hyperventilation or how it restarts. Here we present observations on the phenomenon of the restart of breathing following such apneas. We recorded diaphragmatic and neuronal activities, airflow, tidal CO2 and electroencephalograms during 90 restarts in 5 unanesthetized adult cats. Several phases were recognizable in a restart process that can be characterized generally as a transition from tonic to phasic inspiratory activity. Following a phase of apnea (no diaphragmatic activity; duration of 14.3 s +/− 6.8, s.d) there was a brief phase of tonic diaphragmatic activity with superimposed small bursts. This phase of uniphasic inspiratory efforts produced small breaths as seen in the airflow tracings and occurred in 89% of the restarts. Following this phase, diaphragmatic bursts increased in amplitude and regularity and were followed by persisting activity during the early expiratory period (postinspiratory inspiratory activity). In the final phase, postinspiratory inspiratory activity decreased. The duration of the process from apnea to eupnea required 1–2 min. Recordings of medullary inspiratory (n=56) and expiratory (n=19) respiratory neurons within the ventral respiratory group from the retrofacial nucleus caudally to approximately the level of the obex showed that central expiratory neuronal activity developed after inspiratory activity during the restart process. This indicates that in the recovery from apnea inspiratory and expiratory neurons are driven sequentially by hypoxemia and hypercapnia. Supported by grant NS 46062