不同通气模式对急性呼吸窘迫综合征模型犬呼吸力学和氧代动力学的影响

目的：研究在保留自主呼吸时，双相气道正压通气和间歇正压通气对急性呼吸窘迫综合征模型犬呼吸力学和氧代动力学的影响。方法：选择健康杂种犬12只，全麻后用油酸制成急性呼吸窘迫综合征模型，采用自身对照法观察其在机械通气前、间歇正压通气和双相气道正压通气等状态下呼吸、循环指标的变化。结果：与基础值相比，双相气道正压通气和间歇正压通气时的每分钟通气量、血氧分压、氧输送均显著增加（P〈0．05）；每分钟通气量相同时，双相气道正压通气状态下气道峰压、平均气道压较间歇正压通气的相应参数值显著降低，心输出量、氧输送显著增加（P〈0．05）；平均气道压相同时，双相气道正压通气气道峰压、氧利用率较间歇正压通气显著降低；每分钟通气量、血氧分压、氧输送显著增加（P〈0．05）。结论：保留自主呼吸时，双相气道正压通气可减少急性呼吸窘迫综合征犬肺气压伤发生。     

A comparative study of the cardiorespiratory effects of continuous positive airway pressure breathing and continuous positive pressure ventilation in acute respiratory failure

Positive end expiratory pressure (PEEP) produces cardiopulmonary effects whether administered by controlled positive pressure ventilation (CPPV) or continuous positive airway pressure (CPAP). In eight patients with acute respiratory failure, the effects of 20 cm PEEP administered via CPPV and CPAP were compared. An esophageal balloon was used to calculate the transmural vascular pressures. The control values under mechanical ventilation with no PEEP (IPPV) for PaO₂ and QS/QT (FiO₂ being 1.0) were respectively 132±15 mmHg and 31±3%; CPPV gave a PaO₂ of 369±27 mmHg and QS/QT fo 14±1.6%, CPAP 365±18 mmHg and 18±1.3% respectively. The two different modes of ventilation (CPPV and CPAP) gave identical blood gas improvement through the same level of end expiratory transpulmonary pressure despite marked differences between absolute mean airway and esophageal pressures. Conversely, hemodynamic tolerance was very different from one technique to the other: CPPV depressed cardiac index from 3.4±0.3 to 2.4±0.2 l/min/m² as well as decreasing transmural filling pressures, suggesting a reduction in venous return. Conversely, filling pressures maintained at control values during CPAP and cardiac indexes were unchanged.Abbreviations IPPV intermittent positive pressure ventilation; mechanical ventilation (controlled mode) with zero end expiratory pressure (ZEEP) - CPPV continuous positive pressure ventilation: mechanical ventilation (controlled mode) with a positive pressure during expiration - CPAP continuous positive airway pressure; spontaneous ventilation with a positive pressure maintained during expiration - PEEP positive end expiratory pressure, whatever the ventilatory mode; spontaneous (CPAP) or mechanical (CPPV) Presented in part at the 44 th annual meeting of American College of Chest Physicians, Washington DC, October 1978     

Unusual response to continuous positive pressure ventilation

In a patient with acute respiratory failure due to aspiration pneumonia, PaO₂ decrease and [(Q)\dot]_s /[(Q)\dot]_t\dot Q_s /\dot Q_t increase were observed during continuous positive pressure ventilation. This paradoxical finding was atributted to vascular collapse in well ventilated upper alveoli associated with blood flow redistribution to dependent hypoventilated areas with low ventilation-perfusion relationships.     

Hemodynamic effects of continuous positive-pressure ventilation and high-frequency jet ventilation with positive end-expiratory pressure in normal dogs

The hemodynamic effects of high-frequency jet ventilation (HFJV) at 60, 120, 240, and 480 breath/min, and conventional ventilation at 15 breath/min were compared in 6 anesthetized, paralyzed dogs, at 0, 10, and 20 cm H2O of positive end-expiratory pressure (PEEP). On HFJV at the same inspired oxygen, PaCO2, and PEEP levels, hemodynamic function improved significantly. Cardiac output was higher, whereas transmural CVP and pulmonary vascular resistances were lower. The improvement was primarily related to a decrease in mean airway pressure, particularly at higher PEEP levels. When PEEP was applied, hemodynamic function improved even when mean airway pressure was maintained constant. The findings suggest that lung volume was smaller during HFJV, and/or that lung volume changes during each respiratory cycle contributed to differences in venous return and ventricular function.     

Cardiovascular effects of positive pressure ventilation

The cardiovascular effects associated with mechanical ventilation are the result of a complex interaction between changes in (1) preload secondary to changes in VR, RV-LV interactions, and direct mechanical effects of lung inflation and (2) changes in LV afterload, especially with cardiomyopathy-induced low output states. The possible ischemia-producing effects of high airway pressure are poorly understood and should be investigated in future studies. The overall effects of mechanical ventilation also are modulated by the sympathoadrenal response to decreased CO. Patients with coronary ischemia appear to benefit from mechanical ventilation, although patient selection and the mechanisms involved need much more investigation. Positive end-expiratory pressure-induced changes in abdominal pressure at different blood volume levels need to be considered. The cardiovascular effects of mixed modes of ventilation, such as intermittent mandatory ventilation, involve even more complex interactions.     

气道压力释放通气和持续气道正压开放肺的比较

目的探讨气道压力释放通气（APRV）与持续气道正压（CPAP）通气两种通气模式实施肺复张策略治疗急性呼吸窘迫综合征（ARDS）对血流动力学、肺力学和氧代谢指标的影响。方法选择ARDS行机械通气及脉搏轮廓法持续血流动力学监测的患者15例，随机实施APRV模式肺复张或CPAP模式肺复张，每隔4h复张1次。其中APRV组设定高水平压力（Phigh）为35cm H2O（1cm H2O=0．098kPa），低水平压力（Plow）为压力-容积（P—V）曲线的下拐点（LIP）；CPAP组设定CPAP为35cm H2O；两组持续时间均为40s。记录复张前后的肺力学、氧代谢指标以及复张时的血流动力学变化。结果在APRV模式下行肺复张时心脏指数（CI）轻度下降，且持续时间较短。两种复张模式均可使肺顺应性等力学参数及氧合明显改善，以APRV模式尤为明显。结论采用APRV模式进行ARDS肺复张治疗可避免镇静剂的使用，对血流动力学干扰较小，对肺力学及氧合的改善优于CPAP模式。     

Diastolic function in neonates after the arterial switch operation: effects of positive pressure ventilation and inspiratory time

Received: 27 July 1999/Final revision received: 21 January 2000/Accepted: 26 January 2000     

双水平正压通气和持续气道正压通气治疗呼吸窘迫综合征早产儿的临床疗效比较

目的 比较双水平正压通气和持续气道正压通气治疗赣州地区呼吸窘迫综合征(RDS)早产儿的临床疗效.方法 选取2017年5月至2020年4月该院收治的RDS早产儿60例为研究对象,按照随机数字表法随机分为观察组(双水平正压通气)和对照组(持续气道正压通气),各30例.对比两种治疗方式下患儿血气分析指标、并发症发生率,以及无创正压总通气时间、住院时间、有创呼吸机上机率、后期停氧时间.结果 治疗前两组患儿二氧化碳分压(PaCO2)、氧分压(PaO2)差异无统计学意义(P>0.05),治疗后观察组患儿PaCO2、PaO2优于对照组,差异有统计学意义(P<0.05).观察组患儿并发症发生率(3.33％)低于对照组(16.67％),差异有统计学意义(P<0.05).观察组无创正压总通气时间、住院时间及后期停氧时间与对照组相比,差异无统计学意义(P>0.05);观察组有创呼吸机上机率低于对照组,差异有统计学意义(P<0.05).结论 双水平正压通气可有效改善RDS早产儿血气分析指标,降低有创呼吸机上机率及并发症发生率,同时并未延长患儿住院时间、后期停氧时间以及无创正压通气时间,有一定的应用价值.     

Potentially harmful effects of inspiratory synchronization during pressure preset ventilation

Purpose

Pressure preset ventilation (PPV) modes with set inspiratory time can be classified according to their ability to synchronize pressure delivery with patient’s inspiratory efforts (i-synchronization). Non-i-synchronized (like airway pressure release ventilation, APRV), partially i-synchronized (like biphasic airway pressure), and fully i-synchronized modes (like assist-pressure control) can be distinguished. Under identical ventilatory settings across PPV modes, the degree of i-synchronization may affect tidal volume (V _T), transpulmonary pressure (P _TP), and their variability. We performed bench and clinical studies.

Methods

In the bench study, all the PPV modes of five ventilators were tested with an active lung simulator. Spontaneous efforts of ?10 cmH₂O at rates of 20 and 30 breaths/min were simulated. Ventilator settings were high pressure 30 cmH₂O, positive end-expiratory pressure (PEEP) 15 cmH₂O, frequency 15 breaths/min, and inspiratory to expiratory ratios (I:E) 1:3 and 3:1. In the clinical studies, data from eight intubated patients suffering from acute respiratory distress syndrome (ARDS) and ventilated with APRV were compared to the bench tests. In four additional ARDS patients, each of the PPV modes was compared.

Results

As the degree of i-synchronization among the different PPV modes increased, mean V _T and P _TP swings markedly increased while breathing variability decreased. This was consistent with clinical comparison in four ARDS patients. Observational results in eight ARDS patients show low V _T and a high variability with APRV.

Conclusion

Despite identical ventilator settings, the different PPV modes lead to substantial differences in V _T, P _TP, and breathing variability in the presence spontaneous efforts. Clinicians should be aware of the possible harmful effects of i-synchronization especially when high V _T is undesirable.     

Efficacy of flow-by during continuous positive airway pressure ventilation

We investigated clinically the differences in respiratory work of patients imposed by three modes of one ventilator: the flow-by system, the demand valve system, and the pressure support system. Inspiratory work using flow-by and pressure support systems was reduced sufficiently when compared to the demand valve system. Moreover, fluctuation of the airway pressure was minimal with the flow-by mode. These results suggest that the flow-by mode is beneficial to patients breathing spontaneously with continuous positive airway pressure.     

无创机械通气不同吸气压力对慢性阻塞性肺疾病急性加重期患者腹内压的影响

目的 探讨不同吸气压力(IPAP)对慢性阻塞性肺疾病急性加重期(AECOPD)无创正压机械通气患者腹内压(IAP)的影响.方法 选取60例AECOPD无创正压机械通气患者,行机械通气前测量患者IAP值,行无创正压机械通气后,按照正压机械通气不同吸气压力将患者随机分为三组:10～ 14 cm H2O(A组),15 ～19 cm H2O(B组),20～25 cm H2O(C组);每组各20例患者,分别于调整吸气压力后2h、第1～7天每天同一时间点监测患者IAP.结果 与A组、B组比较,C组患者IAP差异有统计学意义(P＜0.05);A组与B组比较差异无统计学意义(P＞0.05).同一组不同监测时间点比较,通气后2h及通气后第1天与其他时间点比较差异有统计学意义(P＜0.05).结论 对于AECOPD无创正压机械通气患者,随着吸气压力水平的升高,患者IAP有升高趋势,并且在早期较明显.因此,在无创正压机械通气早期,监测患者IAP可能有益于为患者选择适合的吸气压力支持水平.     

Effects of pressure support ventilation and continuous positive airway pressure on diaphragm performance

Many patients who are on mechanical ventilation are on ventilator modes called pressure support ventilation (PSV) and continuous positive airway pressure (CPAP) particularly when they are being weaned. As the diaphragm is responsible for approximately 75% of breathing, it is important to promote diaphragm shortening to optimize weaning from mechanical ventilation. The purpose of our 1998 quasi-experimental study was to explore the effects of PSV and CPVP on diaphragm shortening. An animal model was utilized using four Sprague-Dawley rats from the same litter purchased from Sasco (Kansas City, USA). Also measured in this study were intrathoracic pressure (DeltaITP), positive inspiratory pressure, respiratory rate, tidal volume, end-tidal carbon dioxide, central venous pressure (CVP) and mean arterial pressure (MAP). Pressure support was increased in increments of 5 cm H2O at CPAP levels of 0, 2 and 4 cm H2O. A direct assessment of diaphragm shortening was achieved through the adherence of a miniaturized ultrasonic sensor to the inferior surface of the middle costal surface of the right hemidiaphragm of four Sprague-Dawley rats. Limitations of this study included a small sample size, anaesthetized rats and abdominal dissection for insertion of the ultrasonic sensor. As PSV was increased, there was a decrease in MAP, CVP, respiratory rate and end-tidal CO2. When increasing levels of CPAP were added to PSV, a decrease in diaphragm shortening was observed. These results support that higher levels CPAP may hinder diaphragmatic function thus prolong mechanical ventilation. The purpose of this pilot study was to explore the effects of PSV and CPAP on diaphragm shortening. Also measured were DeltaITP, positive inspiratory pressure, respiratory rate, tidal volume, end-tidal carbon dioxide, CVP and MAP. Pressure support was increased in increments of 5 cm H2O at CPAP levels of 0, 2 and 4 cm H2O. A direct assessment of diaphragm shortening was achieved through the adherence of a miniaturized ultrasonic sensor to the inferior surface of the middle costal surface of the right hemidiaphragm of four Sprague-Dawley rats. Limitations of this study included a small sample size, anaesthetized rats and abdominal dissection for insertion of the ultrasonic sensor. As PSV was increased, there was a decrease in MAP, CVP, respiratory rate and end-tidal CO2. When increasing levels of CPAP were added to PSV, a decrease in diaphragm shortening was observed.     

Cardiac and respiratory effects of continuous positive airway pressure and noninvasive ventilation in acute cardiac pulmonary edema

OBJECTIVE: Continuous positive airway pressure (CPAP) is considered an effective nonpharmacologic method of treating patients with severe acute cardiogenic pulmonary edema. However, we hypothesized that bilevel noninvasive positive-pressure ventilation (NPPV), which combines both inspiratory pressure support and positive expiratory pressure, would unload the respiratory muscles and improve cardiac and hemodynamic function more effectively than CPAP. DESIGN: Randomized crossover study. SETTING: Critical care unit, Raymond Poincaré Hospital. PATIENTS: Six consecutive patients with acute cardiogenic pulmonary edema. INTERVENTIONS: Patients were sequentially treated with 5 cm H2O CPAP, 10 cm H2O CPAP, and NPPV in a random order. MEASUREMENTS AND MAIN RESULTS: Cardiac and hemodynamic function and indexes of respiratory mechanics were measured at each treatment sequence. NPPV reduced the esophageal pressure swing and esophageal pressure-time product compared with baseline (p <.05). There was no reduction in esophageal pressure swing or esophageal pressure-time product with CPAP. NPPV and 10 cm H2O CPAP reduced the mean transmural right and left atrial filling pressures without a change in cardiac index. CONCLUSIONS: This study demonstrates that NPPV was more effective at unloading the respiratory muscles than CPAP in acute cardiogenic pulmonary edema. In addition, NPPV and 10 cm H2O CPAP produced a reduction in right and left ventricular preload, which suggests an improvement in cardiac performance.     

Noninvasive positive pressure ventilation in infants with upper airway obstruction: comparison of continuous and bilevel positive pressure

Objective This study evaluated the efficacy of noninvasive continuous positive pressure (CPAP) ventilation in infants with severe upper airway obstruction and compared CPAP to bilevel positive airway pressure (BIPAP) ventilation.Design and setting Prospective, randomized, controlled study in the pulmonary pediatric department of a university hospital.Patients Ten infants (median age 9.5 months, range 3—18) with laryngomalacia (n=5), tracheomalacia (n=3), tracheal hypoplasia (n=1), and Pierre Robin syndrome (n=1)Interventions Breathing pattern and respiratory effort were measured by esophageal and transdiaphragmatic pressure monitoring during spontaneous breathing, with or without CPAP and BIPAP ventilation.Measurements and results Median respiratory rate decreased from 45 breaths/min (range 24–84) during spontaneous breathing to 29 (range 18–60) during CPAP ventilation. All indices of respiratory effort decreased significantly during CPAP ventilation compared to unassisted spontaneous breathing (median, range): esophageal pressure swing from 28 to 10 cmH₂O (13–76 to 7–28), esophageal pressure time product from 695 to 143 cmH₂O/s per minute (264–1417 to 98–469), diaphragmatic pressure time product from 845 to 195 cmH₂O/s per minute (264–1417 to 159–1183) During BIPAP ventilation a similar decrease in respiratory effort was observed but with patient-ventilator asynchrony in all patients.Conclusions This short-term study shows that noninvasive CPAP and BIPAP ventilation are associated with a significant and comparable decrease in respiratory effort in infants with upper airway obstruction. However, BIPAP ventilation was associated with patient-ventilator asynchrony.     

Effects of continuous positive airway pressure/positive end-expiratory pressure and pressure-support ventilation on work of breathing,using an animal model

OBJECTIVE: Evaluate the effects of continuous positive airway pressure (CPAP)/positive end-expiratory pressure (PEEP) and pressure support ventilation (PSV) on work of breathing (WOB). METHODS: With 13 anesthetized lambs we measured WOB with an esophageal balloon and flow signals. All the animals were sedated, intubated, and ventilated, using 2 pediatric ventilators (Servo 300 and VIP Bird). Ventilator settings were CPAP of 0, 5, and 10 cm H(2)O and PSV of 5 and 10 cm H(2)O with PEEP of 0, 5, and 10 cm H(2)O. Data were analyzed with 2-way analysis of variance. RESULTS: With the Servo 300 the total WOB (WOB(T)) increased between CPAP/PEEP of 0 and 10 cm H(2)O (p 相似文献   

Minimizing work of breathing with continuous positive airway pressure and intermittent mandatory ventilation: an improved continuous low-flow system

Minimizing work of breathing (WOB) during intermittent mandatory ventilation (IMV) and continuous positive airway pressure (CPAP) is important as it facilitates weaning from mechanical ventilation. To minimize WOB, we devised a simple, continuous-flow CPAP-IMV system that uses a weighted, partially filled reservoir bag and operates efficiently at low fresh gas flow (FGF). We compared both the pattern and WOB of our system (FGF at 15 L/min) with a conventional continuous-flow CPAP/IMV system (FGF at 15 and 30 L/min) as well as with two relatively efficient demand-value systems, the Servo 900 B and 900 C. Six healthy male subjects were studied; tidal volumes (VT), flow, mouth pressure, and pleural pressure (Ppl) were measured. Ten breaths, matched for VT, from each subject on each system were selected for analysis. Mechanical WOB was estimated by integrating Ppl with respect to VT. The conventional continuous-flow system was associated with a high work/breath relative to the other systems (p less than .001). The weighted reservoir system was associated with a significantly lower work/breath (p less than .001), its performance approaching that of the Servo 900B. Work/breath was least with the Servo 900C (p less than .001). As breathing frequency was higher with the demand valve than continuous-flow systems (p less than .001), the difference in work/time was minimal between the weighted reservoir bag and demand-valve systems. These systems were all associated with significantly (p less than .001) lower work/time than the conventional system at both FGF.(ABSTRACT TRUNCATED AT 250 WORDS)     

持续气道正压通气、T管及压力支持通气等条件下患者呼吸功的比较性研究

目的：探讨从呼吸功角度评价呼吸机脱机方式优劣的可能性及其意义。方法：通过ＢｉｃｏｒｅＣＰ１００呼吸监测仪测定２２例患者在压力支持通气（ＰＳＶ）、持续气道内正压（ＣＰＡＰ）通气、Ｔ管及拔管后２小时等条件下的呼吸功的变化。结果：ＣＰＡＰ０．４９ｋＰａ（１ｋＰａ＝１０．２０ｃｍＨ２Ｏ）、Ｔ管、ＰＳＶ０．４９ｋＰａ时，患者呼吸功依次逐渐降低。ＣＰＡＰ０．４９ｋＰａ时呼吸功（９．９８Ｊ／ｍｉｎ）比ＰＳＶ０．４９ｋＰａ时高２３．７％（Ｐ＜０．００１），比拔管后２小时高４８．５％（Ｐ＜０．０１），与Ｔ管时比较无显著性差异。Ｔ管时呼吸功（９．３１Ｊ／ｍｉｎ）比ＰＳＶ０．４９ｋＰａ时高１５．４％（Ｐ＜０．０５），比拔管后２小时高３８．５％（Ｐ＜０．０１）。结论：患者呼吸功因脱机方式不同而显著不同，ＰＳＶ０．４９ｋＰａ比ＣＰＡＰ０．４９ｋＰａ和Ｔ管更有利于脱机。     

A comparison of continuous positive pressure ventilation,combined high frequency ventilation and airway pressure release ventilation on experimental lung injury

In pigs with oleic induced lung injury, the effectiveness of combined high frequency ventilation (CHFV, with VDR-Phasitron) and airway pressure release ventilation (APRV) were compared to continuous positive pressure ventilation (CPPV) in a randomized study. The respiratory rate was 15/min, CPAP 8 mmHg and FiO₂ 0.25. PaCO₂ was maintained at 5 kPa. PaO₂ was significantly lower with APRV (12.5±3.9 kPa, CPPV: 15.8±3.9 kPa, and CHFV: 15.5±3.2 kPa). This was in accordance with the lowest peak airway pressure during APRV (20.9±4.8 mmHg, CPPV: 26.3±4.4 mmHg and CHFV: 28.2±3.7 mmHg). There was no difference in the pericardiac pressure between the 3 ventilation modes. The pressure related depressive effects on the cardiovascular function during CHFV and APRV were similar to those during CPPV. Adequate oxygenation and ventilation could be achieved with both CHFV and APRV, but these methods were not superior to CPPV.The study was supported by Instrumentariumin Tiedesäätiö     

Superimposed inspiratory work of the Siemens Servo 300 ventilator during continuous positive airway pressure

Objective To compare the superimposed inspired work of breathing (SIW) of the Siemens Servo 300 ventilator with the Siemens Servo 900 C ventilator.Design Comparisons made at continuous positive airway pressure (CPAP) levels of 0, 4, and 8 cmH₂O, and at trigger sensitivities of –1 and –2 cmH₂O, and flow triggering.Setting General intensive care unit in a University teaching hospital.Patients 7 patients receiving CPAP.Results At all levels of CPAP, the SIW was significantly less with the Siemens Servo 300 ventilator as compared to the Siemens Servo 900 C ventilator despite similar trigger sensitivities. No significant difference was found in the SIW of the Servo 300 ventilator when comparing trigger sensitivities of –1 cmH₂O, –2 cmH₂O, and flow triggering. Different levels of CPAP had no effect on SIW.Conclusions The Siemens Servo 300 ventilator entails less superimposed inspiratory work of breathing than the Siemens Servo 900 C ventilator.