engleski

LONG TERM CHANGES OF PHRENIC NERVE ACTIVITY DUE TO EXPOSURE TO HYPERCAPNIC STIMULUS

Aims: This study was performed to investigate effects of episodic and continuous hypercapnia on the phrenic nerve activity during and after hypercapnic stimulus. Methods: Experiments were performed on anesthetized, vagotomized, mechanically ventilated adult male Sprague Dawley rats. Animals were exposed to 15 minutes of continuous hypercapnia (N=6 ; cHC), or five 3 min episodic hypercapnic episodes (N=13, eHC). In eHC, animals were exposed to room air (N=9 ; eHC-air) or to 50% O2 (N=4 ; eHC-O2) in the baseline and in the recovery periods. The changes in peak phrenic nerve activity (PNA), were measured during hypercapnic exposures and 15, 30 and 60 minutes after the end of last hypercapnic episode and compared to the baseline values. Results: Intermittent hypercapnia produced increase of the peak PNA during hypercapnic episodes (average increase by 239±12% in eHC-air group, and by 478±36% in eHC-O2 group), and throughout continuous hypercapnia (increase by 459±516%) compared to baseline. At 15, 30 and 60 min peak PNA was at 100±45%, 81±52% and 86±49% of baseline value, respectively in eHC-air group, and 86±31%, 80±31% and 72±32% of baseline value, respectively in eHC-O2 group. At the same time points in the cHC group, peak PNA was 133±35%, 113±45% and 86±23%, respectively compared to baseline. Conclusion: Both continuous and episodic hypercapnia produced nonsignificant changes of the phrenic nerve activity 60 minutes after the last hypercapnic episode. However, exposure to episodic hypercapnia separated by 50% O2 produced greater depression of the phrenic nerve activity compared to continuous hypercapnia and episodic hypercapnia separated by room air.

respiratory plasticity; hypercapnia; phrenic nerve

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