Vianna L G, Koulouris N, Lanigan C, Moxham J
Department of Thoracic Medicine, King's College Hospital, London, United Kingdom.
J Appl Physiol (1985). 1990 Oct;69(4):1486-93. doi: 10.1152/jappl.1990.69.4.1486.
The effect of acute hypercapnia on skeletal muscle contractility and relaxation rate was investigated. The contractile force of fresh and fatigued quadriceps femoris (QF) and adductor pollicis (AP) was studied in normal humans by use of electrical stimulation. Maximum relaxation rate from stimulated contractions was measured for both muscles. Acute hypercapnia led to a rapid substantial reduction of contraction force. The respiratory acidosis after 9% CO2 was breathed for 20 min [mean venous blood pH 7.26 and end-tidal PCO2 (PETCO2) 65.1 Torr] reduced 20- and 100-Hz stimulated contractions of QF to 72.8 +/- 4.4 and 80.0 +/- 5.1% of control values, respectively. After 8 and 9% CO2 were breathed for 12 min, AP forces at 20- and 50-Hz stimulation were also reduced. Twitch tension of AP was reduced by a mean of 25.5% when subjects breathed 9% CO2 for 12 min [mean arterialized venous blood pH (pHav) 7.25 and PETCO2 66 Torr]. Over the range of 5% (pHav 7.38 and PETCO2 47 Torr) to 9% CO2, there was a linear relationship between twitch tension loss and pHav, arterialized venous blood PCO2, and PETCO2. Acute respiratory acidosis (mean PETCO2 61 Torr) increased the severity of low-frequency fatigue after intermittent voluntary contractions of AP. At 20 min of recovery, twitch tension was 63.2 +/- 13.4 and 46.8 +/- 16.4% of control value after exercise breathing air and 8% CO2, respectively. Acute hypercapnia (mean PETCO2 65.1 and 60.5 Torr) did not alter the maximum relaxation rate from tetanic contractions of fresh QF and from twitch tensions of AP.
研究了急性高碳酸血症对骨骼肌收缩力和舒张速率的影响。通过电刺激在正常人体中研究新鲜和疲劳的股四头肌（QF）及拇收肌（AP）的收缩力。测量了两块肌肉受刺激收缩后的最大舒张速率。急性高碳酸血症导致收缩力迅速大幅降低。吸入9%二氧化碳20分钟后（平均静脉血pH 7.26，呼气末PCO₂（PETCO₂）65.1 Torr）的呼吸性酸中毒使QF在20赫兹和100赫兹刺激下的收缩分别降至对照值的72.8±4.4%和80.0±5.1%。吸入8%和9%二氧化碳12分钟后，AP在20赫兹和50赫兹刺激下的力量也降低。当受试者吸入9%二氧化碳12分钟（平均动脉化静脉血pH（pHav）7.25，PETCO₂ 66 Torr）时，AP的单收缩张力平均降低25.5%。在5%（pHav 7.38，PETCO₂ 47 Torr）至9%二氧化碳范围内，单收缩张力损失与pHav、动脉化静脉血PCO₂及PETCO₂之间存在线性关系。急性呼吸性酸中毒（平均PETCO₂ 61 Torr）增加了AP间歇性自主收缩后低频疲劳的严重程度。在恢复20分钟时，运动后呼吸空气和吸入8%二氧化碳后，单收缩张力分别为对照值的63.2±13.4%和46.8±16.4%。急性高碳酸血症（平均PETCO₂ 65.1和60.5 Torr）未改变新鲜QF强直收缩及AP单收缩张力的最大舒张速率。
