TY - JOUR
T1 - Expiratory abdominal muscle activity during ventilatory chemostimulation in piglets
AU - Watchko, J. F.
AU - O'Day, T. L.
AU - Brozanski, B. S.
AU - Guthrie, R. D.
PY - 1990/1/1
Y1 - 1990/1/1
N2 - We examined abdominal muscle minute electromyographic (EMG) activity (peak moving time average EMG x respiratory rate) during eupnea, hyperoxic hypercapnia (8% CO2-40% O2-balance N2), and hypoxia (13% O2) in 12 anesthetized (0.5% halothane) newborn piglets. In addition, we assessed the role of vagal afferent pathways in the abdominal muscles' response to ventilatory chemostimulation by examining abdominal EMG activity (EMGab) before and after bilateral cervical vagotomy in five animals. Phasic expiratory EMGab was observed in 11 of 12 piglets during eupnea. Hypercapnia was associated with a sustained augmentation of minute EMGab (444 ± 208% control). In contrast, hypoxia consistently augmented (1 min, 193 ± 33% control) then diminished (5 min, 126 ± 39% control) minute EMGab. Vagotomy resulted in a decline in peak moving time average EMGab by approximately one-half (48 ± 18% control); the abdominal muscles' response to ventilatory chemostimulation, however, was qualitatively unchanged. We conclude that 1) expiration during eupnea in anesthetized newborn piglets is associated with phasic EMGab; 2) both hypercapnia and hypoxia augment minute EMGab; however, only hypercapnia is associated with sustained augmentation; and 3) although vagal afferents have a role in modulating the base-line level of EMGab, other extravagal mechanisms appear to determine the pattern of EMGab in response to ventilatory chemostimulation.
AB - We examined abdominal muscle minute electromyographic (EMG) activity (peak moving time average EMG x respiratory rate) during eupnea, hyperoxic hypercapnia (8% CO2-40% O2-balance N2), and hypoxia (13% O2) in 12 anesthetized (0.5% halothane) newborn piglets. In addition, we assessed the role of vagal afferent pathways in the abdominal muscles' response to ventilatory chemostimulation by examining abdominal EMG activity (EMGab) before and after bilateral cervical vagotomy in five animals. Phasic expiratory EMGab was observed in 11 of 12 piglets during eupnea. Hypercapnia was associated with a sustained augmentation of minute EMGab (444 ± 208% control). In contrast, hypoxia consistently augmented (1 min, 193 ± 33% control) then diminished (5 min, 126 ± 39% control) minute EMGab. Vagotomy resulted in a decline in peak moving time average EMGab by approximately one-half (48 ± 18% control); the abdominal muscles' response to ventilatory chemostimulation, however, was qualitatively unchanged. We conclude that 1) expiration during eupnea in anesthetized newborn piglets is associated with phasic EMGab; 2) both hypercapnia and hypoxia augment minute EMGab; however, only hypercapnia is associated with sustained augmentation; and 3) although vagal afferents have a role in modulating the base-line level of EMGab, other extravagal mechanisms appear to determine the pattern of EMGab in response to ventilatory chemostimulation.
KW - control of breathing
KW - diaphragm
KW - newborn respiration
KW - respiratory muscles
KW - vagal reflexes
UR - http://www.scopus.com/inward/record.url?scp=0025266325&partnerID=8YFLogxK
U2 - 10.1152/jappl.1990.68.4.1343
DO - 10.1152/jappl.1990.68.4.1343
M3 - Article
C2 - 2140826
AN - SCOPUS:0025266325
SN - 0161-7567
VL - 68
SP - 1343
EP - 1349
JO - Journal of Applied Physiology
JF - Journal of Applied Physiology
IS - 4
ER -