呼吸重症：气道阻塞性疾病的呼吸机波形
常记溪亭日暮，沉醉不知归路。
云南省一院 孙丹雄
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小小医生之有趣的医学
让我们一起摇啊摇！
有人的地方，就有江湖！有呼吸机的地方，就有呼吸机波形！有呼吸机波形的地方，一般没有专门的书籍讲解波形！
难得查到一篇讲解呼吸机波形的文献：阻塞性肺疾病的呼吸机波形！
Dhand R . Ventilator graphics and respiratory mechanics in the patient with obstructive lung disease[J]. Respiratory Care, 2005, 50(2):259-61.
01 内源性PEEP
PEEP：呼气末正压！
什么情况？
Fig. 1. Airway and alveolar pressures in patients with intrinsic positive end-expiratory pressure (auto-PEEP) and the effect of increasing extrinsic PEEP. At the end of a normal expiration (left panel), the alveolar pressure equilibrates with the airway pressure. In this example the alveolar pressure is equal to airway pressure, which in turn is equal to atmospheric pressure when external PEEP is set at zero. In the presence of dynamic hyperinflation, alveolar pressure remains higher than airway pressure at end-expiration (middle panel). The pressure within alveoli at end-expiration represents the level of auto-PEEP. The difference between alveolar pressure and airway pressure may be reduced by increasing the external PEEP (right panel). Mechanical ventilators routinely display airway pressure. Special maneuvers are needed to determine end-expiratory alveolar pressure (auto-PEEP) in mechanically-ventilated patients.
02
内源性PEEP影响触发
Fig. 2. Pressure-triggering in a patient with intrinsic positive end-expiratory pressure (PEEP). In the left panel, the level of external PEEP is set at 6 cm H2O and the trigger threshold is set 2 c m H2O below that level. The ventilator is triggered when the patient’s inspiratory effort reduces the airway pressure to the set threshold level. In contrast, the right panel shows a patient with a set PEEP of zero and a similar trigger threshold of 2 cm H2O. However, this patient has an intrinsic PEEP level of 6 cm H2O. The patient’s inspiratory effort would therefore have to generate a negative pressure of 8 cm H2O to trigger the ventilator. Pt=patient. 德尔塔P=change in pressure. (From Reference 18, with permission.)
03 气体陷闭
Fig. 3. Flow-time waveform showing persistence of flow at endexpiration in a patient with intrinsic positive end-expiratory pressure (auto-PEEP). In most patients with obstructive lung disease, failure to reach zero flow at the end of a relaxed expiration signifies that lung volume is above functional residual capacity and indicates dynamic hyperinflation.
04 肺动态过度充气
每次呼气，气体都呼不完，肺里面的气体就会越积越多！
Fig. 4. In the absence of air trapping the volume of the lung at end-expiration reaches functional residual capacity (FRC). In contrast, in the presence of dynamic hyperinflation the volume of the lung at end-expiration remains higher than FRC (upper waveform in upper panel). The volume expired during a prolonged apnea could be used to determine the volume of gas trapped above FRC (lower panel). The difference between the volume at end-inspiration (VEI) and tidal volume (VT) represents the volume above FRC, or trapped gas volume (Vtrap). ALI = acute lung injury. Insp. ti = inspiratory time. Exp. ti = expiratory time. VT= tidal volume. (From Reference 39, with permission).
05 气道阻塞的压力波形
Fig. 5. Recordings of flow and airway pressure (Paw) over time in a patient with chronic obstructive pulmonary disease receiving controlled mechanical ventilation. When the airway is occluded at end-inhalation, the airway pressure declines rapidly from peak inspiratory pressure (Ppeak) to a lower initial pressure (Pinit), followed by a gradual decrease to a plateau pressure (Pplat). (From Reference 43, with permission.)
在吸气末，假如气道阻塞，气道压力达到峰值，然后迅速下降，然后缓慢的到达平台压。正常情况下，应该是很快就到达平台压，平台压要维持一段时间，而不是到平台压之后很快转为呼气。
06
内源性PEEP的测量
Fig. 6. Airway pressure (Paw), flow, and volume waveforms from a patient receiving controlled mechanical ventilation. After the third breath, an airway occlusion was performed by rapidly occluding the expiratory port of the ventilator. During the occlusion, pressure in the airway equilibrates with alveolar pressure. In the presence of intrinsic positive end-expiratory pressure (PEEPi), airway pressure increases and the plateau value signifies the level of intrinsic PEEPi. (From Reference 8, with permission.)
控制通气模式下，在呼气相阻断呼气，一段时间后气道压升高，达到稳定状态之后，气道压=内源性PEEP，这时候的气道压就是内源性PEEP。
其实，就是内源性PEEP缓慢的释放到气道，被呼吸机探测到！
07 无效触发
无效触发：病人吸气没有触发呼吸机！
Fig. 8. Flow, airway pressure (Paw), and esophageal pressure (Pes) waveforms from a patient with severe chronic obstructive pulmonary disease (COPD) receiving pressure support of 20 cm H2O. The start of inspiratory efforts that trigger the ventilator are indicated by dotted vertical lines. There is a substantial time delay between the onset of the patient’s inspiratory effort and the onset of flow from the ventilator. There are also several ineffective efforts, which are indicated by the black arrows. The ventilator rate is set at 12 breaths/min, but the patient is making 33 efforts/min. Note that ineffective efforts occur during both mechanical inspiration and expiration. Flow waveforms are helpful in identifying ineffective efforts, indicated by the open arrows. Ineffective efforts during mechanical inspiration cause an abrupt increase in inspiratory flow, whereas during mechanical expiration they cause an abrupt decrease in expiratory flow. (From Reference 47, with permission.)
图8。流量、气道压力(Paw)和食管压力(Pes)波形来自接受20厘米H2O压力支持的严重慢性阻塞性肺疾病(COPD)患者。触发呼吸机的吸气动作的开始由垂直虚线表示。从患者开始吸气到呼吸机开始流量之间有相当长的时间延迟。还有几种无效的努力，用黑箭头表示。呼吸机的速率被设定为12次呼吸/分钟，但患者正在进行33次努力/分钟。请注意，无效的努力发生在机械吸气和呼气期间。流动波形有助于识别无效的努力，如空心箭头所示。机械吸气时无效的努力会导致吸气流量的突然增加，而机械呼气时无效的努力会导致呼气流量的突然减少。(摘自参考文献47，经允许。)
08 增加流速可减少无效触发
Fig. 9. Ventilator waveforms showing the effect of inspiratory flow on ineffective patient efforts that do not trigger the ventilator. These airway pressure (Paw), flow, and esophageal pressure (Pes) waveforms are from a patient with chronic obstructive pulmonary disease receiving assist-control ventilation, with a constant tidal volume of 0.55 L. Ineffective efforts are indicated by arrows. A: Several ineffective efforts are seen with an inspiratory flow rate of 30 L/min. B: The inspiratory flow rate was increased to 90 L/min. By decreasing the inspiratory time and allowing more time for exhalation, dynamic hyperinflation was reduced and the number of ineffective efforts decreased. The ventilator rate increased as the patient was able to more effectively trigger the ventilator. In patients with dynamic hyperinflation causing ineffective triggering, an increase in the inspiratory flow rate could substantially reduce wasted patient effort. (From Reference 47, with permission.)
图9。呼吸机波形显示吸气流量对不触发呼吸机的无效患者努力的影响。这些气道压力(Paw)、流量和食管压力(Pes)波形来自接受辅助控制通气的慢性阻塞性肺疾病患者，恒定潮气量为0.55升。无效的努力用箭头表示。答:在吸气流速为30升/分钟的情况下，可以看到一些无效的努力。乙:吸气流速增加到90升/分钟。通过减少吸气时间和允许更多的呼气时间，动态过度充气减少，无效努力的数量减少。当患者能够更有效地触发呼吸机时，呼吸机频率增加。在动态过度充气导致无效触发的患者中，吸气流速的增加可以显著减少浪费的患者努力。(摘自参考文献47，经允许。)
09 流速-容量环
piu
10
流速容量环：分泌物
Fig. 12. Flow-volume curves indicating presence of airway secretions. In 4 different patients, a sawtooth pattern is observed in both inspiratory and expiratory limbs of the flow-volume curves. The numbers to the right of each panel represent the number of each patient in the study. (From Reference 55, with permission.)
11
压力容量环
Fig. 14. Pressure-volume loops may also be helpful in detecting an inappropriately low inspiratory flow setting (left) and active patient efforts during inspiration (right).
12 流速容量环：药物治疗
Fig. 15. Flow-volume loops showing a response to bronchodilator administration. The expiratory limb of the curve is concave in patients with expiratory flow limitation. Administration of a bronchodilator aerosol leads to improvement in expiratory flow. (From Reference 18, with permission.)
支气管扩张剂治疗后：峰流速增加，呼气肢凹陷消失！
杨柳岸，晓风残月。
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呼吸机波形！