Buchler B, Magder S, Roussos C
J Appl Physiol (1985). 1985 Jan;58(1):265-73. doi: 10.1152/jappl.1985.58.1.265.
The effects of diaphragmatic contraction frequency (no. of intermittent tetanic contractions/min) at a given tension-time index and of duty cycle (contraction time/total cycle time) on diaphragmatic blood flow were measured in anesthetized mongrel dogs during bilateral supramaximal phrenic nerve stimulation. Diaphragmatic blood flow was measured by the radionuclide-labeled microsphere method. Contraction frequency was varied between 10 and 160/min at duty cycles of 0.25 and 0.75. Diaphragmatic blood flow increased with contraction frequency from 1.47 +/- 0.13 ml X min-1 X g-1 (mean +/- SE) at an average of 18/min to 2.65 +/- 0.16 ml X min-1 X g-1 at 74/min (P less than 0.01) with a duty cycle of 0.25 and from 1.32 +/- 0.19 ml X min-1 X g-1 at an average of 15/min to 1.96 +/- 0.15 ml X min-1 X g-1 at 80/min (P less than 0.02) with a duty cycle of 0.75. At higher contraction frequencies diaphragmatic blood flow did not increase further at both duty cycles. In addition, diaphragmatic blood flow was higher with a duty cycle of 0.25 than 0.75 at all contraction frequencies. We conclude that frequency of contraction is a major determinant of diaphragmatic blood flow and that high duty cycle impedes diaphragmatic blood flow.
在双侧膈神经超最大刺激期间，于麻醉的杂种犬身上测量了给定张力 - 时间指数下膈肌收缩频率（间歇性强直收缩次数/分钟）和占空比（收缩时间/总周期时间）对膈肌血流量的影响。膈肌血流量采用放射性核素标记微球法测量。在占空比为0.25和0.75时，收缩频率在10至160次/分钟之间变化。在占空比为0.25时，膈肌血流量随着收缩频率从平均18次/分钟时的1.47±0.13毫升·分钟⁻¹·克⁻¹增加到74次/分钟时的2.65±0.16毫升·分钟⁻¹·克⁻¹（P＜0.01）；在占空比为0.75时，膈肌血流量从平均15次/分钟时的1.32±0.19毫升·分钟⁻¹·克⁻¹增加到80次/分钟时的1.96±0.15毫升·分钟⁻¹·克⁻¹（P＜0.02）。在两个占空比下，更高的收缩频率时膈肌血流量均未进一步增加。此外，在所有收缩频率下，占空比为0.25时的膈肌血流量高于占空比为0.75时的。我们得出结论，收缩频率是膈肌血流量的主要决定因素，高占空比会阻碍膈肌血流量。
