第二节 肺换气和组织换气 Pulmonary Ventilation and Tissues Ventilation

一、气体交换的原理 principle of gas exchange （一）气体 扩散 gas diffusion 气体分子不停的进行着无定向的运动，其结果是气体分子从分压高处向分压低处发生净转移，这一过程称为气体扩散。 Gas molecules move freely among one another. The result is gas molecules diffuse from high-pressure area toward low-pressure area. The process is called gas diffusion. 肺换气和组织换气就是物理性的扩散过程。 Pulmonary ventilation and tissues ventilation are physical diffusion processes .

气体扩散遵循着以下物理原则 gas diffusion obeys the following physical principles 1.气体从分压高的一侧向低的一侧扩散。 Gas diffuses from the high-pressure area to the low-pressure area. 2.各气体的扩散方向和量，决定于该气体的分压差、气体的扩散速度和气体在液体中的溶解度。 The diffusion direction and volume of gas is decided by its own partial pressure difference、diffusion rate and the solubility in fluid.

3.在液体或气－液交界面，气体的扩散速度与它在液体中的溶解度密切相关。溶解度高的扩散快。 In the fluid or at the interface of gas and fluid, the diffusion rate of gas is correlate closely to its solubility in fluid. The gas which solubility is higher diffuses quicker. 4.气体的扩散速度∝（1/ √气体分子量）。分子量大的扩散速度慢。 Diffusion rate of gas ∝（1/ √molecular weight）The gas which molecular weigh is larger diffuses slowlier.

∝ D∝ △P*T*A*S d*√MW 单位时间内气体扩散的容积为气体扩散速率，它受下列因素影响 The volume of gas diffusion in unit time is called diffusion rate. It is effected by the following factors 分压差×扩散面积×温度×气体溶解度 扩散距离×√分子量 扩散速率 ∝ △P*T*A*S D∝ d*√MW

1.气体的分压差：分压差大－－扩散快 Gas partial pressure difference: gas partial pressure difference is larger—diffuses faster 2.气体分子量和溶解度：溶解度高，扩散快 分子量大，扩散慢 Gas molecular weight and solubility: when solubility is high, it diffuses fast when molecular weight is large,it diffuses slowly.

3. 肺泡膜的扩散面积：扩散面积大，扩散快 Diffusion area of alveolar membrane : when diffusion area of alveolar membrane is large,it diffuses fast. 安静状态下，肺泡扩散面积40m2 diffusion area of alveolar membrane is 40m2 in normal quiet state. 运动时肺泡扩散面积70m2 diffusion area of alveolar membrane is 70m2 during sports. 疾病状态时下降 diffusion area of alveolar membrane decreases in disease.

｝ 4. 扩散距离－肺泡膜的厚度（反比关系）(图39-9) Diffusion distance—thickness of alveolar membrane(inverse ratio relationship) 肺纤维化---- 厚度增加 Pulmonary fibrosis---Thickness increases 肺水肿----扩散下降 Pulmonary edema---Diffusion decreases 5. 温度 Temperature 液体温度上升，溶解度上升－扩散快 Temperature of fluid increases Solubility increases—Diffuses fast ｝

6. 肺血流量与通气血流比值 Pulmonary Perfusion and Ventilation /Perfusion Ratio 0.75秒 右心搏出量60ml/每搏 流经肺泡膜气体交换所需时间0.3秒，故时间上有很大贮备潜力。 0.75second RSV 60ml/per beat Exchange time of the gas flowing through alveolar membrane is 0.3 second. So there is great time reserve potential .

如果血流量下降，气体交换正常－交换的总量 下降，故肺泡通气量与血流量之间必须保持恰 当的比值。 If blood flow decreases and gas exchange are normal--the exchange total amount decreases. So alveolar ventilation and blood flow must keep an appropriate ratio. Ventilation/perfusion ratio 通气/血流比值(安静时正常值)＝4.2升/5升＝0.84 VA/Q (value of normal quiet state) ＝4.2升/5升＝0.84 VA每分肺泡通气量 alveolar ventilation per minute Q 每分肺血流量 pulmonary perfusion per minute

通气/血流比值升高：表示有部分肺泡气不能与血液中的气体充分交换＝生理无效腔增大。 ventilation /perfusion ratio increases:it means partial alveolar gas can not exchange fully with the blood gas=physiological dead space increases. 通气/血流比值下降：表示有部分血液经通气不良的肺泡，得不到充分气体交换，相当于功能性动－静脉短路。 ventilation /perfusion ratio decreases:it means partial blood flow through hypoventilation alveoli. They can not get fully exchange. And it equals functional arteriovenous shunt.

正常人直立时， 肺各局部VAQ分布不均匀 When normal adult is standing, every part of lung VAQ is not well-distributed 肺尖 VA下降/Q下降 Q下降更明显 Apex of lung VA descent/Q descent Q descenting is more obvious. 比值上升（可在3以上） ratio rises(more than 3) 肺底 VA下降/Q上升 比值下降（0.6） Base of lung VA descents/Q rises ratio descents(0.6)

7. 肺扩散容量 (pulmonary diffusion capacity) 指各种气体在单位分压差（1mmHg）下，每 分钟能通过呼吸膜的气体量（ml）。它是测定呼吸膜扩散功能的生理指标。 When all kinds of gas is under unit partial pressure difference,the gas volume(ml) passing through respiratory membrane per minute is called pulmonary diffusion capacity. It is the physiological index to test the diffusion ability of respiratory membrane.

CO2扩散率/ O2扩散率＝√O2分子量/√CO2分子量= √32/√44＝5.6/6.6 CO2 diffusibility/ O2 diffusibility= √O2 molecular weight/ √CO2 molecular weight=√32/√44＝5.6/6.6 在肺泡气O2的扩散率稍大于CO2 The diffusibility in alveolar gas is a little larger than CO2. 但由于CO2溶解度 /O2溶解= 0.592/0.0244=24.3/1.0(Herry’s law 赫利定理） But because CO2 solubility/ O2 solubility= 0.592/0.0244=24.3/1.0(Herry’s law） CO2扩散速率 /O2扩散速率= （5.6/6.6）×（0.592/0.0244)=20.6/1.0 CO2 diffusion velocity/ O2 diffusion velocity =

由上可知， CO2扩散速率 远大于O2扩散速率，临床上不存在CO2扩散障碍。一般以O2的扩散容量作为测定指标。 From all above ,we know that the diffusion velocity of CO2 is much more than that of O2. There is no diffusion disturbance of CO2 in clinical. Usually,we take the diffusion volume of O2 as test index. 正常成人20ml/(min*mmHg) normal adult 20ml/(min*mmHg) 男＞女 ；成人＞老幼 male>female; adult>the old or the immature

（二）呼吸气体和人体不同部位气体的分压 partial pressure of respiratory air and gas of different human body tissues 1. 呼吸气及肺泡气的成分和分压（表5-2） Composition and partial pressure of respiratory air and alveolar air. 呼吸周期中，肺泡气O2及CO2的含量有轻微波动。 In the respiratory cycle, composition of O2 and CO2 in alveolar air fluctuates a little.

呼吸气和肺泡气的成分和分压表5-2；血液气体和组织气体的分压 表5-3 The ingredient and partial pressure of respiratory air and alveolar gas figure 5-2; partial pressure of blood gas and tissues gas figure 5-3

混合气体的总压力是各组成气体的分压力的总和。 The total pressure of mixed gas equals to the summation of partial pressure of each composition. 各组成气的分压＝混合气总压力×该气体的容积百分比 partial pressure of each composition=the total pressure of mixed gas ×volume percentage of the gas N2 600mmHg = 760mmHg × 79% O2 159mmHg = 760mmHg×21％

2.血液气体和组织的分压（张力）（表5-3） partial pressure (tension) of blood gas and tissues gas (figure 5-3)

二、肺换气 Pulmonary gas exchange 混合静脉血PO2是5.32kPa（40mmHg），比肺泡气的13.82 kPa（104mmHg）低，肺泡气中O2向血液中扩散，血液的PO2逐渐上升，最后接近肺泡气的PO2。 PO2 of mixed venous blood is 5.32 kPa（40mmHg） is lower than 13.82 kPa（104mmHg）of alveolar gas. O2 in alveolar gas diffuses to blood. PO2 in blood rises gradually until it is almost equal to PO2 in alveolar gas.

混合静脉血PCO2是6. 12kPa（46mmHg），比肺泡气的5 混合静脉血PCO2是6.12kPa（46mmHg），比肺泡气的5.32 kPa（40mmHg）高，血液中CO2向肺泡中扩散，血液的PCO2逐渐下降，最后接近肺泡气的PCO2。 PCO2 of mixed venous blood is 6.12kPa（46mmHg） It is higher than 5.32 kPa（40mmHg) of alveolar gas. CO2 in blood diffuses to alveolar gas. PCO2 in blood descents gradually until it is almost equal to PCO2 in alveolar gas.

肺换气 Pulmonary gas exchange

三、 组织换气 Tissues Gas Exchange

第三节 气体在血液中的运输 Transport of Gas in the Blood 一、氧和二氧化碳在血液中的存在形式 Existing pattern of O2 and CO2 in the blood 物理溶解（中介作用） physical dissolving(medium) 两种形式 two kind of patterns 化学结合（为主） combination(primary) ｛

O2 溶解 化学结合 CO2 dissolve combination 组织或肺 血液blood Tissues or lung 溶解系数resolution coefficient O2 0.022 ml/1ml 全血blood CO2 0.511ml/1ml 全血blood

二、氧的运输 oxygen transportation 与Hb结合占98.5％ 98.5％ binding to Hb 氧的运输 oxygen transportation 物理溶解占1.5％ 1.5％ physical resolution ｛

氧容量指每100ml血中，血红蛋白结合氧的最大量。 Maximum capacity of ferrohemoglobin binding with O2 in every 100ml blood is named oxygen capacity. 正常Hb在15g/100ml血液中，1gHb结合1.34ml氧。 氧容量＝15×1.34＝20ml When normal Hb is in 15g/100ml blood , 1g Hb binds with 1.34ml O2. Oxygen capacity= 15×1.34＝20ml 氧含量指血红蛋白实际结合的氧量。 The volume of ferrohemoglobin binding with oxygen is called oxygen content. 动脉血：20ml氧 arterial blood: 20ml O2 静脉血：15ml氧 venous blood: 15ml O2

氧饱和度指氧含量占氧容量的百分比。 The percentage of oxygen content to oxygen capacity is called oxygen saturation. 动脉血，氧含量20ml，氧饱和度为100％ In arterial blood, oxygen content equals 20ml and oxygen saturation is 100%. 静脉血，氧含量15ml，氧饱和度为75％ In venous blood , oxygen content equals 15ml and oxygen saturation is 75%.

（一）Hb与O2的可逆结合 reversible binding of Hb and O2 O2分压高（肺）partial pressure is higher(lung) Hb＋O2 HbO2 O2分压低（组织） partial pressure is lower(tissues) （还原、紫蓝色） （氧合、红色） reduction 、royal blue oxygenation、red 盐键断裂break 分子构型紧密型 分子构型疏松型 （tension） 盐键形成form （relaxation）

特点：character 1.可逆性结合，非酶促过程，反应快，受PO2影响。 Reversible binding. Without enzyme. Fast. Effected by PO2. 2.O2与血红蛋白的亚铁离子结合，结合后亚铁离子的离子价不变，故称氧合，不是氧化。 O2 binds with Fe2+ of ferrohemoglobin . The ion value is permanent. So the process is called oxygenation but not oxidation.

3.血红蛋白的珠蛋白由两条α肽链和两条β肽链构成，每条肽链上结合一个含亚铁离子的血红素分子，每个亚铁离子结合一个O2分子。故每个血红蛋白分子可结合4个O2分子（HbO8）1gHb可结合1.34－1.39mlO2. Globin of ferrohemoglobin is made up of two αpeptide chains and two β peptide chains . There is a protoheme molecular on each peptide chain including a Fe2+. Each Fe2+ binds with an O2 . So each ferrohemoglobin can bind with four O2. （HbO8）1gHb can bind with 1.34－1.39mlO2.

4.血红蛋白两对α、β肽链与O2结合可互相促成结合或解离（释放）。 在肺部，PO2升高促结合； 在组织，PO2下降促释放。 Conjugation of peptide chains α、βof ferrohemoglobin and O2 can facilitate binding or dissociation(releasing). In lungs, increasing of PO2 promotes combination. In tissues, decreasing of PO2 promotes releasing.

5. Hb与O2的结合或解离曲线呈S型与Hb的变构效应有关 The binding or dissociation curves of Hb and O2 appear S form.This is related to the allosterism effect of Hb. Hb与O2结合－－盐键断裂，R型 Hb与O2解离－－盐键形成，T型 Hb binds with O2—salt bond breaks, R form Hb dissociates with O2—salt bond forms,T form T型对O2亲和力小。The affinity of T form to O2 is smaller. R型对O2亲和力大。 The affinity of R form to O2 is larger.

血红蛋白的异常形成 1.胎儿血红蛋白（HbF）是由两条γ链和α链结合组成，它对O2亲和力比HbA大。可能由于γ链不与2，3DPG相结合，不受2，3DPG影响的缘故。 2.镰状细胞贫血（HbS)两条β链第6位谷氨酸为缬氨酸所取代，使去氧Hb释放O2的能力下降，导致组织缺O2。 3.地中海贫血 。 我国常见β地贫。由于β链合成障碍HbA生成抑制，HbF代偿增多，O2解离曲线左移。

（二）氧解离曲线 oxygen dissociation curve 反映PO2与氧合Hb饱和度的关系的曲线。（图40-9） The curve reacts the relationship of PO2 and saturation of oxygenation Hb . (figure 40-9)

氧解离曲线 oxygen dissociation curve

特点：character 1.曲线上段：PO2 60－100mmHg. 坡度较平坦 Superior segment of curve: PO2 60－100mmHg. Slope is flat. 1）氧分压变化虽大但饱和度变异小－－即使外界或肺泡中PO2下降，但氧合饱和度依然可维持在较高水平。 Partial pressure of oxygen changes greatly. But saturation changes little—even PO2 of environment or alveoli descents, oxygenation saturation will maintain high level. 2）PO2＞100mmHg时，氧合饱和度增加很不明显，血氧量增加很少。When PO2＞100mmHg, rising of oxygenation saturation is not obvious . Rising of blood oxygen volume is little.

2. 曲线中段 PO2 60－40mmHg 是HbO2释放O2的部分。 Middle segment of curve PO2 60－40mmHg is the part that HbO2 releases O2. 此时Hb氧饱和度75％，血O2含量14.4mL％， 即每100ml血液流过组织时释放5mlO2。 At this time Hb oxygen saturation is 75%, oxygen content in blood is 14.4mL％. In the other words, every 100ml blood releases 5mlO2 when it flows over tissues. 血液流经组织时释放出的O2容积所占动脉O2含量的百分数－－O2利用系数。安静时为25％，运动时可增加到75％。 The percentage of oxygen capacity released when blood flows over tissues to oxygen content in arteria is called oxygen utilization coefficient. It is 25% in normal quiet state and it increases to 75% in sports.

3. 曲线下段 PO2 10－40mmHg . 坡度陡 . Inferior segment of curve . PO2 10－40mmHg . The slope is steep. PO2略有下降，促使较多O2解离，饱和度下降，有 利于组织活动的供氧，氧利用系数上升至75％。 PO2 descents a little. It makes oxygen dissociation saturation descent. This is benefit to supplying oxygen for tissue activity. Oxygen utilization coefficient increases to 75%. 机制：血红蛋白αβ肽链结合氧时，互相作用。 Mechanism: when αβpeptide chains of ferrohemoglobin bind with oxygen, they interact.

｛ 高原PO2下降 意义：Hb的氧缓冲功能 PO2 descents in plateau Significance: amortization 组织活动 function of Hb tissue activity 血红蛋白氧缓冲功能：不论血液本身或外界O2浓度有 较大幅度变动，而组织PO2仍可保持在稳定的正常范围 内。O2 5ml/（100ml*min） Ferrohemoglobin amortization function: even blood itself of enviroment oxygen change greatly, tissue PO2 still remain in normal range. O2 5ml/（100ml*min） ｛

影响氧解离曲线的因素 factors effect oxygen dissociation curve

（三）影响氧离曲线的因素（图40-10） factors effect oxygen dissociation curve(figure 40-10) 1. PH和CO2影响 influence of PH and CO2 通常用P50表示Hb对O2的亲和力。 Usually we use P50 as the affinity of Hb and O2. 正常P50：PO2 26.5mmHg。 Normal P50: PO2 26.5mmHg。 P50上升，亲和力下降，曲线右移；when P50 rises, affinity descents and curve moves to right. P50下降，亲和力上升，曲线左移。when P50 descents, affinity rises and curve moves to left.

Bohr效应 Bohr effect PH下降，PCO2上升－－促使盐键形成， Hb分子构型转 为T型；曲线右移， P50增大，氧饱和度下降，解离增加。 PH descents and PCO2 rises—make salt bond form. Molecular configuration of Hb changes to T form. Curve move to right. P50 increases. Oxygen saturation descents and dissociation increases. PH上升，PCO2下降－－ 促使盐键断裂，Hb分子构型转 为R型；曲线左移，P50降低，氧饱和度增加，解离下降。 PH rises and PCO2 descents—make salt bond break. Molecular configuration of Hb changes to R form. Curve move to left. P50 descents. Oxygen saturation increases and dissociation descents.

2.温度的影响 effect of temperature T增加－－ Hb对O2亲和力下降，氧饱和度下降, 曲线 右移， H+活动性增加。 T increases—affinity of Hb to O2 descents . Oxygen saturation descents. Curve moves to right. Activity of H+ increases. T下降－－Hb与O2亲和力上升，氧饱和度上升, 曲线 左移，HbO2不易解离出O2（低温麻醉）。 T descents—affinity of Hb to O2 increases . Oxygen saturation increases. Curve moves to left. HbO2 can not dissociate O2 easily(hypothermi anesthesia).

Effect of 2,3-diphosphoglycerate 2，3－DPG为RBC内一种有机磷酸盐。 2，3－DPG is a kind of organophosphate in RBC. 缺氧、贫血hypoxia anemia 长时间运动 long time sports 甲状腺素thyroxine sodium RBC 2，3DPG上升 2，3DPG increases 无氧代谢 anaerobic metabolism 脱氧血红蛋白β链形成盐键 βchain deoxyhemoglobin form salt bond. 失去氧合能力（T型） Hb miss oxygenation ability(T form) 氧离曲线右移，促氧解离 Oxygen dissociation curve move to right, make oxygen dissociate .

4.其他因素 other factors Fe++ Fe+++就失去O2结合能力 miss the ability to bind with O2 CO中毒， CO与Hb结合 CO intoxication, CO bind with Hb COHb（无与O2结合能力） no binding ability to O2

三、二氧化碳的运输（图40-13) Transportation of CO2 （figure 40-13） 物理溶解 （6％） CO2的运输 physical dissolution 碳酸氢盐形式 transportation of CO2 （87％） bicarbonate pattern 化合结合 （94％） combination 氨基甲酸血红蛋白 （7％ ） carbaminohemoglobin ｛ ｛

CO2的运输 transportation of CO2

（一）碳酸氢盐形式的运输 Transport in bicarbonate pattern 特点：character: 1.反应可逆，但需酶的促助。 Reaction is reversible. But it need the help of enzyme. 2.结合或解离决定于CO2分压差。 Conjugation or dissociation is decided by partial pressure difference of CO2. 3.反应中伴有Cl－的转移。 There is the transfer of Cl－ in the reaction.

在组织中in tissues HbNH2+CO2 HbNHCOOH 肺lung HbNHCOO－ ＋H＋ （二）氨基甲酸血红蛋白的形式运输 Transport in carbaminohemoglobin pattern 在组织中in tissues HbNH2+CO2 HbNHCOOH 肺lung HbNHCOO－ ＋H＋

特点：character 1.反应可逆，无需酶的促助。 Reaction is reversible and need not the help of enzyme. 2.结合或解离取决于Hb的氧合作用。 Conjugation or dissociation is decided by the oxygenation effect of Hb. 脱氧Hb与CO2结合多； Much Deoxy Hb binds with CO2. 氧合Hb结合少，解离多。 Little Hb binds.dissociation is much. 3.CO2分压差的影响不明显。 The effect of partial pressure difference is not obvious.

CO2解离曲线carbon dioxide dissociation curve

（三）CO2解离曲线（图40-15） carbon dioxide dissociation curve 1 .血液中CO2的运输量，决定于CO2分压。PCO2上升－－运输量上升，两者呈直线关系。 Transport volume of CO2 in blood is decided by partial pressure of CO2. PCO2 increases—transport volume increases . They appear linear relationship.

2.何尔登效应 Haldane effect O2＋Hb 促使CO2的释放（肺部） promotes the releasing of CO2(lung) 在组织促摄取CO2 intakes CO2 in the tissues 在肺部促CO2释放 releases CO2 in lungs 脱氧血红蛋白携带CO2的能力比氧合血红蛋白要 大，故动脉血携带CO2量少于静脉血。 The ability of deoxyhemoglobin taking along CO2 is larger than oxyhemoglobin. So the volume of CO2 taken along in arterial blood is less than that in venous blood.

3.碳酸酐酶的活性和含量 The content and activity of carbonic anhydrase RBC内碳酸酐酶活性上升－－运输能力上升 Activity of carbonic anhydrase in RBC increasing--transportation ability increasing RBC内碳酸酐酶含量上升－－运输能力上升 Content of carbonic anhydrase in RBC increasing--transportation ability increasing