慢性阻塞性肺疾病急性发作期患者对比例辅助通气的生理反应

目的　探讨比例辅助通气 (PAV)不同辅助水平对慢性阻塞性肺疾病 (COPD)急性发作期患者生理反应的影响。方法　 9例COPD急性发作期患者接受三个不同比例辅助水平的PAV通气 ,观察患者吸气肌肉用力情况和呼吸方式的变化。结果　 (1)与自主呼吸 (SB)相比 ,PAV各辅助水平时的潮气量 (VT)、分钟通气量 (V·E)和呼吸频率 (RR)均稍增高 (P >0 0 5 )。各比例辅助水平之间的VT、V·E 和RR比较差异无显著性 (P >0 0 5 )。 (2 )与SB相比 ,各比例辅助水平时的跨膈压 (Pdi)、压力时间乘积 (PTP)和患者呼吸做功均明显减少 (P >0 0 1) ,Pdi、PTP和患者呼吸做功分别平均减少 8 36cmH2 O、11 4 9cmH2 O·s-1·L-1和 0 5 3J/L。随比例辅助水平的升高 ,Pdi、PTP和患者呼吸功无明显变化(P >0 0 5 )。 (3)PAV可减轻患者呼吸困难 (P <0 0 5 )。结论　本试验证实了无创PAV在COPD急性发作期患者中应用的可行性。患者感觉最舒适的PAV辅助比例水平是 (5 7± 11) %。根据患者感觉舒适情况而设定比例辅助水平的无创PAV可减轻患者的呼吸肌肉负担 ,最舒适水平时呼吸功减少5 7% ,Pdi减少 72 % ,PTP减少 6 5 % ;并改善患者的呼吸方式和呼吸困难     

Mask proportional assist vs pressure support ventilation in patients in clinically stable condition with chronic ventilatory failure

OBJECTIVE: To compare the short-term physiologic effects of mask pressure support ventilation (PSV) and proportional assist ventilation (PAV) in patients in clinically stable condition with chronic ventilatory failure (CVF). DESIGN: Randomized, controlled physiologic study. SETTING: Lung function units of two pulmonary rehabilitation centers. PATIENTS: Eighteen patients with CVF caused by COPD (11 patients) and restrictive chest wall diseases (RCWDs) [7 patients]. METHODS: Assessment of breathing pattern and minute ventilation (E), respiratory muscles and lung mechanics, and patient/ventilator interaction during both unassisted and assisted ventilation. After baseline assessment during spontaneous breathing (SB), mask PSV and PAV were randomly applied at the patient's comfort, with the addition of the same level of continuous positive airway pressure (2 cm H2O or 4 cm H2O in all patients), for 30 min each, with a 20-min interval of SB between periods of assisted ventilation. RESULTS: A longer time was spent to set PAV than PSV (663 +/- 179 s and 246 +/- 58 s, respectively; p < 0.001). Mean airway opening pressure (Pao) computed over a period of 1 min, but not peak Pao, was significantly lower with PAV than with PSV (151 +/- 45 cm H2O/s/min and 207 +/- 73 cm H2O/s/min, respectively; p < 0.002). Tidal volume (VT) exhibited a greater variability with PAV than with PSV (variation coefficient, 16.3% +/- 10.5% vs 11.6% +/- 7.7%, respectively; p < 0.05). Compared with SB, both modalities resulted in a significant increase in VT (by 40% and 36% with PAV and PSV, respectively, on average) and E (by 37% and 35%) with unchanged breathing frequency and duty cycle. Both modalities significantly reduced esophageal (by 39% and 51%) and diaphragmatic (by 42% and 63%) pressure-time products, respectively. Ineffective efforts were observed with neither modes of assistance in any patient. CONCLUSIONS: In resting, awake patients in clinically stable condition with CVF caused by either COPD or RCWD, noninvasive application of PAV, set at the patient's comfort, was not superior to PSV either in increasing VT and E or in unloading the inspiratory muscles. We failed to find any difference in patient/ventilator interaction between ventilatory modes.     

Tolerance and physiologic effects of nocturnal mask pressure support vs proportional assist ventilation in chronic ventilatory failure

STUDY OBJECTIVES: To compare the tolerance and physiologic effects of a 5-night treatment with either nasal proportional assist ventilation (PAV) or pressure support ventilation (PSV) in patients with chronic ventilatory failure. DESIGN: Cross-over, randomized, controlled study. SETTING: Rehabilitation units of pneumology department. PATIENTS OR PARTICIPANTS: Four patients with COPD and 10 patients with restrictive thoracic diseases with chronic hypercapnia (median baseline Paco(2), 55.1 mm Hg) were studied. INTERVENTIONS: In a cross-over study, nasal PAV and PSV set at the patient's comfort were randomly applied during 5 consecutive nights (with a 2-night washout period). MEASUREMENTS AND RESULTS: Continuous nocturnal pulse oximetric saturation (Spo(2)) and arterial blood gas results at wake-up were evaluated at baseline during spontaneous breathing and on the fifth day of ventilatory support. Dyspnea, sleep quality, adaptation, and comfort at inspiration and expiration by visual analog scale (VAS) were evaluated every day as well as a side effects score. On the fifth day, there were no significant differences in daytime Paco(2) (median PAV, 53.3 mm Hg; median PSV, 50.2; p = 0.168). Mean nocturnal Spo(2) improved significantly with both PAV and PSV without any significant differences between modes (baseline median, 92%; PAV median, 94.5%; PSV median, 95%). The percentage of the study night spent < 90% Spo(2) (T90) was slightly but significantly higher with PAV than with PSV (median PAV T90, 4%; median PSV T90, 2%; p = 0.049). The VAS symptom score was similar at day 5 between modes; however, nasal and oral dryness were lower (p = 0.05) and alarm noise was higher (p = 0.037) with PAV. CONCLUSIONS: After 5 days of treatment, both modes had similar tolerance, and were equally effective in reducing daytime hypercapnia and improving nocturnal saturation and symptoms. However, PAV induced less nasal and oral dryness but was associated with higher alarm noise.     

比例辅助通气临床应用的方法学及疗效评价

目的建立比例辅助通气（PAV）临床应用的方法,评价其治疗慢性阻塞性肺疾病（COPD）急性发作期患者的疗效,并与压力辅助通气（PSV）比较。方法选取10例COPD插管机械通气患者,分别采用吸气阻断法和脱逸法设定参数。每例随机先后采用PAV或PSV,PAV辅助比例分别设为80％、60％和40％。同时监测主观感受、血流动力学、氧动力学和呼吸力学指标。结果吸气阻断法与脱逸法设定的参数有很好的相关性r＝0．928（P＜0．01）。PAV不同的辅助比例只影响吸气峰压、呼吸机及患者做功,对通气指标无显著影响（P＞0．05）。对循环功能稳定者,PAV组与PSV组的血流动力学指标差异无显著性（P＞0．05）,氧合均保持在满意水平。PAV组比PSV组潮气量有减小趋势（P＞0．05）,动脉血二氧化碳分压（PaCO2）显著增高（P＜0．05）,吸气峰压显著减低（P＜0．05）。结论采用脱逸法设定参数简单可靠。PAV是安全有效的通气模式,人机协调性好。在做功相同时,PAV比PSV吸气峰压降低,并根据患者的需要保持相应的通气量。     

Effect of different levels of pressure support and proportional assist ventilation on breathing pattern, work of breathing and gas exchange in mechanically ventilated hypercapnic COPD patients with acute respiratory failure

BACKGROUND: Proportional assist ventilation (PAV) has been shown to maintain better patient-ventilator synchrony than pressure support ventilation (PSV); however, its clinical advantage regarding invasive ventilation of COPD patients has not been clarified. OBJECTIVES: To compare the effect of PAV and PSV on respiratory parameters of hypercapnic COPD patients with acute respiratory failure (ARF). METHODS: Nine intubated hypercapnic COPD patients were placed on the PAV or PSV mode in random sequence. For each mode, four levels (L1-L4) of support were applied. At each level, blood gases, flow, tidal volume (VT), airway pressure (Paw), esophageal pressure (Pes) (n = 7), patient respiratory rate (fp), ventilator rate (fv), missing efforts (ME = fp - fv) were measured. RESULTS: We found increases in ME with increasing levels of PSV but not with PAV. PO2 and VT increased whereas PCO2 decreased significantly with increasing levels of PSV (p < 0.05). With PAV, PCO2 decreased and VT increased significantly only at L4 whereas PO2 increased from L1 to L4. Runaways were observed at L3 and L4 of PAV. The pressure-time product (PTP) was determined for effective and missing breaths. The mean total PTP per minute (of effective plus missing breaths) was 160 +/- 57 cm H2O/s.min in PSV and 194 +/- 60 cm H2O/s.min in PAV. CONCLUSION: We conclude that in COPD patients with hypercapnic ARF, with increasing support, PSV causes the appearance of ME whereas PAV develops runaway phenomena, due to the different patient-ventilator interaction; however, these do not limit the improvement of blood gases with the application of both methods.     

Preserved spontaneous breathing improves cardiac output during partial liquid ventilation.

The aim of this study was to examine whether preserved spontaneous breathing (SB) supported by proportional-assist ventilation (PAV) would improve cardiac output (CO) during partial liquid ventilation (PLV) in rabbits with and without lung disease if compared with time-cycled, volume-controlled ventilation (CV) combined with muscle paralysis (MP). PLV was initiated in 17 healthy rabbits and 17 surfactant-depleted rabbits using 12 to 15 ml/kg of perfluorodecaline. Both ventilatory modes, SB+PAV and CV+MP, were applied in random sequence using a crossover design. CO was measured by thermodilution. CO was significantly higher during SB+PAV than during CV+MP: 136 +/- 21 ml/kg x min (mean +/- SD) versus 120 +/- 30 ml/kg x min (p = 0.004) in healthy rabbits, and 147 +/- 19 ml/kg x min versus 111 +/- 13 ml/kg x min (p < 0.0001) in surfactant-depleted rabbits, resulting in an improved oxygen delivery. This difference was mainly caused by a larger stroke volume during SB+PAV, whereas there was little change in heart rate. In surfactant-depleted rabbits, SB+PAV resulted in improved arterial blood pressure and arterial and mixed venous pH and in a higher PaO2 at the same level of PEEP and mean airway pressure. We conclude that during PLV, CO is higher during SB+PAV than during CV+MP, resulting in an improved oxygen delivery. In surfactant-depleted rabbits, improved CO, oxygen delivery, and arterial blood pressure resulted in higher pH, possibly reflecting improved tissue perfusion and oxygenation.     

Physiological response to intrapulmonary percussive ventilation in stable COPD patients

Intrapulmonary percussive ventilation (IPV) is a ventilatory technique that delivers bursts of high-flow respiratory gas into the lung at high rates, intended for treating acute respiratory failure and for mobilization of secretions. We performed a study, aimed at assessing the physiological response to IPV, on patients' breathing pattern, inspiratory effort, lung mechanics and tolerance to ventilation. Ten COPD patients underwent randomized trials of IPV through a face mask at different pressure/frequency combinations (1.2 bar/250 cycles/min; 1.8/250; 1.2/350; 1.8/350), separated by return to baseline (SB), using the IMP2 ventilator. In 5 patients we have also compared the physiological changes of IPV with those obtained during pressure support ventilation (PSV). Minute ventilation did not vary among the trials, but tidal volumes (VT) were significantly greater during 1.2/250, 1.2/350 and 1.8/350 compared to SB. The pressure time product of the diaphragm per minute (PTPdi/min) estimate of the diaphragm oxygen expenditure was also significantly reduced during 1.2/250 and 1.8/250 (209 cmH2O x s/min for SB vs. 143 and 125 for 1.2/250 and 1.8/250, respectively P < 0.05), as well as dynamic intrinsic end-expiratory pressure (PEEPi,dyn). Similar reduction in PTPdi/min were obtained also during PSV. Tolerance to ventilation and oxygen saturation were satisfactory and did not change during the different trials. In 5 normal subjects a prolonged apnea trial lasting > 2 min was also performed, without any significant decrease in SaO2 or subjective discomfort. In conclusion, IPV was able to guarantee an adequate ventilation, while inducing a significant unloading of the diaphragm during the "low-frequency" trials.     

Lack of additional effect of adjunct of assisted ventilation to pulmonary rehabilitation in mild COPD patients

Different modalities of assisted ventilation improve breathlessness and exercise tolerance in patients with chronic obstructive pulmonary disease (COPD).The aim of this study was to evaluate the effects of the addition of assisted ventilation during exercise training on the outcome of a structured pulmonary rehabilitation programme (PRP) in COPD patients. Thirty-three male patients with stable COPD (mean (SD) forced expiratory volume in 1 s (FEV1) 44 (16) % pred), without chronic ventilatory failure, undergoing a 6-week multidisciplinary outpatient PRP including exercise training, were randomised to training during either mask proportional assist ventilation (PAV: 18 patients) or spontaneous breathing (SB: 15 patients). Assessment included exercise tolerance, dyspnoea, leg fatigue, and health-related quality of life (HRQL). Five out of 18 patients (28%) in the PAV group dropped out due to lack of compliance with the equipment. Both groups showed significant post-PRP improvements in exercise tolerance (peak work rate difference: 20 (95% Cl 2.4-37.6) and 14 (3.8% CI to 24.2) W in PAV and SB group, respectively), dyspnoea and leg fatigue, but not in HRQL, without any significant difference between groups. It is concluded that with the modality and in the patients assessed in this study assisted ventilation during training sessions included in a multidisciplinary PRP was not well tolerated by all patients and gave no additional physiological benefit in comparison with exercise training alone.     

Nasal proportional assist ventilation unloads the inspiratory muscles of stable patients with hypercapnia due to COPD.

This study was undertaken to assess the physiological effects of proportional assist ventilation (PAV), administered noninvasively through a nose mask, on ventilatory pattern, arterial blood gases, lung mechanics, and inspiratory muscle effort in stable, hypercapnic patients with chronic obstructive pulmonary disease. In 15 patients, PAV was set by adjusting volume assist (VA) and flow assist (FA) according to the "run-away" technique and the patient's comfort respectively. The level of support was fixed at 80% of the total possible assistance and averaged 13.9+/-4.1 cmH2O x L(-1) and 4.1+/-1.3 cmH2O x L(-1) x s for VA and FA, respectively. Continuous positive airway pressure (CPAP) was established at 2 cmH2O and then increased to 5 cmH2O. Physiological measurements were made during spontaneous breathing (SB), after more than 40 min of PAV, and 20 min after the rise in CPAP. On average, PAV improved ventilation (10.3+/-2.1 to 12.5+/-2.0 L x m(-1)), tidal volume (0.60+/-0.11 to 0.76+/-0.24 L), arterial oxygen tension and arterial carbon dioxide pressure (from 6.7+/-0.7 to 7.1+/-0.9 and from 7.6+/-1.0 to 7.2+/-1.2 kPa, respectively). During SB, pulmonary resistance and dynamic lung elastance averaged 15.0+/-7.6 cmH2O x L(-1) s and 15.8+/-8.0 cmH2O x L(-1), respectively. Assuming a normal chest wall elastance (5 cmH2O x L(-1)), VA and FA relieved respectively approximately 70% of the elastic and 30% of the resistive burden, with PAV set with the procedure of this study. The overall magnitude of the patients' inspiratory effort, measured by means of the oesophageal and diaphragmatic pressure time product in 10 patients was significantly reduced by PAV, on average, 328+/-122 to 226+/-118 (-31%) and 361+/-119 to 254+/-126 (-30%) cmH2O x min(-1), respectively. In 10 patients the electrical activity of the diaphragm (Edi) was also reduced by PAV to approximately 70%, on average, of the SB activity. The rise of CPAP 25 cmH2O did not cause any further significant change in the physiological variables. In all instances there was a good patient-ventilator interaction, the ventilatory breath never entering into the patient's neural expiratory time. These data show that nasal proportional assist ventilation can provide physiological benefits to the stable hypercapnic chronic obstructive pulmonary disease patients. In fact, proportional assist ventilation, which was well tolerated by all patients, unloaded the inspiratory muscles and improved arterial blood gases. Further studies can clarify whether these beneficial physiological effects of nasal proportional assist ventilation can bear profitable consequences in the overall clinical management of chronic obstructive pulmonary disease patients with chronic carbon dioxide retention.     

Noninvasive proportional assist ventilation for acute respiratory insufficiency. Comparison with pressure support ventilation.

Noninvasive positive pressure ventilation (NPPV) is usually applied using pressure support ventilation (PSV). Proportional assist ventilation (PAV) is a newer mode that delivers assisted ventilation in proportion to patient effort. We hypothesized that PAV for NPPV would support gas exchange and avoid intubation as well as PSV and be more comfortable and tolerable for patients. Adult patients with acute respiratory insufficiency were randomized to receive NPPV with PAV delivered using the Respironics Vision ventilator or PSV using a Puritan-Bennett 7200ae critical care ventilator. Each mode was adjusted to relieve dyspnea and improve gas exchange until patients met weaning or intubation criteria, died, or refused to continue. Twenty-one and 23 patients were entered into the PAV and PSV groups, respectively, and had similar diagnoses and baseline characteristics, although pH was slightly lower in the PAV group (7.30 versus 7.35, p = 0.02). Mortality and intubation rates were similar, but refusal rate was lower, reduction in respiratory rate was more rapid, and there were fewer complications in the PAV group. We conclude that use of the PAV mode is feasible for noninvasive therapy of acute respiratory insufficiency. Compared with PSV delivered with the Puritan-Bennett 7200ae, PAV is associated with more rapid improvements in some physiologic variables and is better tolerated.     

Proportional assist ventilation

Partial ventilatory support techniques are intended for patients who are unable to maintain a normal alveolar ventilation, despite normal central control for respiration. Proportional assist ventilation (PAV) is a novel mode of partial ventilatory support in which the ventilator generates an instantaneous inspiratory pressure in proportion to the instantaneous effort of the patient. In theory, PAV should normalize the neuro-ventilatory coupling by making the ventilator an extension of patient's respiratory muscles, while leaving to the patient the entire control of all aspects of breathing. PAV, however, shares a common problem with the conventional partial ventilatory support modes. In mechanically ventilated patients, the respiratory system impedance may change over time. These changes may impair the good matching between ventilator output and patient's ventilatory demand and lead to patient-ventilator asynchrony. To take full advantage of PAV, the authors believe that PAV should continuously and automatically adapt to the respiratory system passive mechanics, assessed by continuous noninvasive measurement of total elastance and resistance.     

Comparison of inspiratory work of breathing in T-piece breathing, PSV, and pleural pressure support ventilation (PPSV)

We have compared the inspiratory work of breathing during T-piece breathing, pressure support ventilation (PSV), and pleural pressure support ventilation (PPSV) by using a lung model with variable compliance and resistance, under simulated spontaneous breathing. Our lung model consists of two spring-loaded bellows, representing the lung and diaphragm, placed in an airtight container. Inspiration begins with the withdrawal of air from the diaphragm bellows by a time-cycled jet-flow-creating Venturi mechanism. Expiration occurs by opening the diaphragm bellows to the atmosphere. Work of breathing (WOB) is calculated by plotting the pressure-volume curve, with pressure corresponding to intrabox pressure and volume corresponding to the tidal volume; PPSV is a new mode of mechanical ventilatory support accomplished by setting the ventilator (Servo 900C) into the PSV mode with a level of 0 cm H2O, using the pleural pressure as the input and target signal. The PPSV maximally reduces WOB under any circumstances. The PSV sufficiently reduced WOB only in the normal lung and the lung with low compliance; however, a pressure supporting time is diminished in the lung with low compliance. The serious limitations of PSV remain in its application to the lung with high resistance. It is concluded that PPSV is closer to the actual patient's signal and has a potential advantage in reducing WOB in the lung with low compliance or high resistance (or both). The lung with flow limitation is still a challenging issue for mechanical ventilatory assistance.     

神经电活动辅助通气:一种新的机械通气模式

机械通气是呼吸衰竭患者重要的支持手段,但传统的机械通气存在明显人机不同步,可能导致机械通气时间延长、呼吸机相关肺损伤等相关并发症.神经电活动辅助通气,通过监测膈肌电活动.根据自身吸气驱动,成比例地持续辅助通气.目前研究表明神经电活动辅助通气明显改善有创及无创机械通气人机同步性;减轻呼吸肌肉负载;能自动调节通气支持水平,具有一定的肺保护作用;利用膈肌电活动,发挥独特的监测功能.     

慢性阻塞性肺疾病撤机困难呼吸力学特征10例分析

目的为提高慢性阻塞性肺疾病(COPD)患者撤机成功率提供生理学依据。方法检测2006年1月至2009年12月广州医学院第一附属医院收治的10例撤机困难COPD患者的呼吸力学指标,观察患者自主呼吸(SB)及机械通气时的呼吸力学指标变化。结果 SB时的呼吸频率(RR)、潮气量(VT)和分钟通气量(Ve)分别为(27.94±8.23)次/min、(0.266±0.107)L和(6.843±1.333)L/min,机械通气时的RR降低,而VT和Ve时升高(均P<0.05)。SB和机械通气时的动态内源性呼吸末正压分别为(0.82±0.19)kPa和(0.41±1.12)kPa,SB时明显增高(P<0.01),吸气中期气道阻力(RL)(2.43±0.94)kPa/(L.S)。SB时的P0.1为(0.61±0.16)kPa。SB时的最大跨膈压、最大食管负压和最大吸气口腔压分别为(5.08±0.93)kPa、(-5.00±0.95)kPa和(-3.78±0.86)kPa。SB时跨膈压(Pdi)和吸气压力时间乘积(PTPins)分别为(0.82±0.20)kPa和(48.93±11.94)kPa.s;机械通气时较SB显著降低,分别为(0.67±0.17)kPa和(30.33±11.72)kPa.s(P均<0.05)。结论撤机困难COPD患者存在显著的呼吸力学异常,SB时呼吸浅快,动态内源性呼吸末正压、RL与呼吸中枢驱动等均增高,吸气肌肉无力;应用PSV(1.57 kPa)联合PEEP(48%动态内源性呼吸末正压)可降低约50%的动态内源性呼吸末正压、17.8%的Pdi和38%的PTPins。     

Respiratory function during pressure support ventilation

Pressure support ventilation (PSV) is a pressure assist form of mechanical ventilatory support that augments the patient's spontaneous inspiratory efforts with a clinician selected level of positive airway pressure. To understand the effects of PSV on respiratory function, experiments were performed on 15 stable patients requiring synchronized intermittent mandatory ventilation (SIMV), as well as on a mechanical model simulating these patients' ventilatory systems. In the clinical study, gas exchange, airway pressures, blood pressure and heart rate were measured while SIMV was replaced by enough PSV to approximate the baseline SIMV tidal volume (VT). Measurements were repeated while this PSV level was then reduced in three 5 cm H2O steps every 10 to 15 minutes. It was found that PSV was a reasonable form of mechanical ventilatory support in patients with spontaneous ventilatory drives. It improves patient comfort, reduces the patient's ventilatory work, and provides a more balanced pressure and volume change form of muscle work to the patient. The clinical significance of these properties during the weaning process remain to be determined.     

Comparison of two methods for weaning patients with chronic obstructive pulmonary disease requiring mechanical ventilation for more than 15 days.

We designed a prospective multicenter randomized controlled study in three long-term weaning units (LWU) to evaluate which protocol, inspiratory pressure support ventilation (PSV) or spontaneous breathing trials (SB), is more effective in weaning patients with chronic obstructive pulmonary disease (COPD) requiring mechanical ventilation for more than 15 d. Fifty-two of 75 patients, failing an initial T-piece trial at admission, were randomly assigned to PSV or SB (26 in both groups). No significant difference was found in weaning success rate (73% versus 77% in the PSV and SB group, respectively), mortality rate (11.5% versus 7.6%), duration of ventilatory assistance (181 +/- 161 versus 130 +/- 106 h), LWU (33 +/- 12 versus 35 +/- 19 d), or total hospital stay. The results of these defined protocols were retrospectively compared with an "uncontrolled clinical practice" in weaning historical control patients. The overall 30-d weaning success rate was significantly greater (87% versus 70%) and the time spent under mechanical ventilation by survived and weaned patients was shorter in the patients in the study than in historical control patients (103 +/- 144 versus 170 +/- 127 h). The LWU and hospital stays were also significantly shorter (27 +/- 12 versus 38 +/- 18 and 38 +/- 17 versus 47 +/- 18 d). Spontaneous breathing trials and decreasing levels of PSV are equally effective in difficult-to-wean patients with COPD. The application of a well-defined protocol, independent of the mode used, may result in better outcomes than uncontrolled clinical practice.     

比例辅助通气、压力支持通气、间歇正压通气对急性呼吸衰竭患者心肺功能影响的比较

目的 观察比例辅助通气（PAV）在临床初步应用疗效及其对急性呼吸衰竭患者呼吸、循环功能的影响,并与间歇正压通气（IPPV）、压力支持通气（PSV）进行比较,为PAV临床广泛应用奠定基础。方法 对10例急性呼衰患者先用IPPV模式通气,同时计算弹性阻力（Ers)和粘性阻力（Rrs),然后将模式改为PSV,根据IPPV时数据设置支持压力,使得潮气量（VT）与IPPV时大致相同。再将模式改为PAV,根据PSV时的数据设置辅助百分比,使得VT和峰压（Ppeak)分别与PSV时大致相同。观察通气期间呼吸力学、血气和血流动力学的变化。结果 在VT相似的情况下,PAV时Ppeak显著低于PSV、IPPV,其患者呼吸功（WOBp)、呼吸机呼吸功（WOBv)均低于PSV、IPPV、PAV与PSV相比,血流动力学各参数间无显著差异,PAV与IPPV相比,其中心静脉压（CVP）和肺毛细血管楔压比,血流动力学各参数间无显著差异,PAV与IPPV相比,其中心静脉压（CVP）和肺毛细血管楔压（PCWP）显著低于IPPV。PAV与PSV相比,在Ppeak相似的情况下,PAV时VT、平均动脉压（mBP)、心输出量（CO）高于PSV,其平均肺动脉压（mPAP)、WOBp低于PSV,其中WOBp显著低于PSV。结论 对于临床急性呼衰患者,PAV与PSV、IPPV相比,其气道压力低,减少了呼吸功,对血流动力学影响较小。     

Proportional assist ventilation may improve exercise performance in severe chronic obstructive pulmonary disease.

PURPOSE: Exercise tolerance is impaired in chronic obstructive pulmonary disease (COPD), in part because of a reduction in ventilatory capacity and excessive dyspnea experienced. The authors reasoned that proportional assist ventilation (PAV), a ventilator mode in which the level of support varies proportionately with patient effort, could be used during exercise to assist ventilation. The purpose of this study was to evaluate the efficacy of PAV to improve exercise endurance and related physiologic parameters in COPD. METHODS: In 8 patients (age = 62.8 years mean, +/- 6.9 standard deviation) with severe COPD (forced expiratory volume in 1 second = 0.70 +/- 0.21 L) flow, volume, dyspnea, leg fatigue, arterial blood gases, and gas exchange were measured during constant workrate exercise (37 +/- 18 watts; i.e., 80% previously determined maximum oxygen consumption). Crossover exercise trials were performed in random order: while spontaneously breathing through the experimental circuit without assistance (control trial) and with PAV (using 9.8 +/- 2.1 cm H2O/L and 3.3 +/- 1.0 cm H2O/L/sec of volume assist and flow assist, respectively). RESULTS: The application of PAV during exercise was well tolerated by each subject. Compared with the control measurement at equivalent time during exercise, PAV improved breathing pattern and arterial blood gases while dyspnea was reduced. Consequently, there was a significant increase in exercise duration with PAV (323 +/- 245 seconds during the control trial compared with 507 +/- 334 seconds with PAV, P = 0.02). CONCLUSIONS: Proportional assist ventilation can improve performance during constant workrate exercise in severe COPD.     

适应性支持通气对慢性阻塞性肺疾病合并呼吸衰竭患者呼吸力学参数的影响

目的 观察适应性支持通气(ASV)不同水平的目标每分钟通气量(MV)对接受机械通气支持患者的呼吸力学参数的影响.方法 2003年11月至2009年12月本院呼吸监护中心收治的呼吸衰竭患者49例,男性37例,女性12例,年龄62～89岁,基础疾病均为慢性阻塞性肺疾病急性加重期.所有人选患者均为机械通气支持至少24 h以上...     

Physiologic effects of negative pressure ventilation in acute exacerbation of chronic obstructive pulmonary disease

To assess the physiologic effects of continuous negative extrathoracic pressure (CNEP), negative pressure ventilation (NPV), and negative extrathoracic end-expiratory pressure (NEEP) added to NPV in patients with acute exacerbation of chronic obstructive pulmonary disease (COPD), we measured in seven patients ventilatory pattern, arterial blood gases, respiratory mechanics, and pressure- time product of the diaphragm (PTPdi) under four conditions: (1) spontaneous breathing (SB); (2) CNEP (-5 cm H(2)O); (3) NPV; (4) NPV plus NEEP. CNEP and NPV were provided by a microprocessor-based iron lung capable of thermistor-triggering. Compared with SB, CNEP improved slightly but significantly Pa(CO(2 ))and pH, and decreased PTPdi (388 +/- 59 versus 302 +/- 43 cm H(2)O. s, respectively, p < 0.05) and dynamic intrinsic positive end-expiratory pressure (PEEPi) (4.6 +/- 0.5 versus 2.1 +/- 0.3 cm H(2)O, respectively, p < 0.001). NPV increased minute ventilation (V E), improved arterial blood gases, and decreased PTPdi to 34% of value during SB (p < 0.001). NEEP added to NPV further slightly decreased PTPdi and improved patient-ventilator interaction by reducing dynamic PEEPi and nontriggering inspiratory efforts. We conclude that CNEP and NPV, provided by microprocessor-based iron lung, are able to improve ventilatory pattern and arterial blood gases, and to unload inspiratory muscles in patients with acute exacerbation of COPD.