Tracheal gas insufflation and related techniques to introduce gas flow into the trachea

Over the past 50 years, a variety of techniques have been developed that have in common the insufflation of gas into the central airway to facilitate carbon dioxide (CO2) clearance. These include continuous insufflation of oxygen, transtracheal jet ventilation, high frequency jet ventilation, transtracheal oxygen administration, intratracheal pulmonary ventilation, and tracheal gas insufflation (TGI). Continuous insufflation of oxygen is a technique used to enhance CO2 removal in the presence of apnea. Transtracheal jet ventilation and high frequency jet ventilation promote bulk gas flow into the lungs. Some techniques, such as transtracheal oxygen administration, provide insufflation of oxygen as an adjunct to spontaneous ventilation. However, other techniques, such as TGI, are used as an adjunct to positive pressure ventilation. Intratracheal pulmonary ventilation provides positive pressure ventilation while bypassing the upper airway. Although some of these techniques are promising adjuncts to mechanical ventilation and may help reduce ventilator-associated lung injury, much remains to be learned about their role in the care of patients with acute lung injury.     

Alternative modes of ventilation. Part I. Disadvantages of controlled mechanical ventilation: intermittent mandatory ventilation

Controlled mechanical ventilation is an accepted therapy for acute respiratory failure but by virtue of the increase in intrathoracic pressure has a large number of disadvantages. It is to overcome these disadvantages that alternative modes of ventilation have been introduced. These aim to reduce the effects of abnormally high airway pressure on the lung whilst recruiting solid alveoli and at the same time maintaining effective blood volume. Intermittent mandatory ventilation is a mode of ventilation first introduced to aid weaning which may reduce the need for sedation, permit better tolerance of high levels of PEEP and maintain urine osmolar output. High frequency ventilation utilising low airway pressures can maintain pulmonary gas exchange whilst reducing the effects of stretch on the lung. Its major role would seem to be in cases of bronchopleural fistula and necrotising pneumonia where a low mean airway pressure is essential. Low frequency positive pressure ventilation with extra corporeal CO₂ removal, whilst a very labour intensive technique, has produced a favourabie outcome in patients with terminal respiratory failure. Use of PEEP is associated with further deleterious haemodynamic effects which are largely overcome with use of continuous positive airway pressure during spontaneous respiration. PEEP is widely used. Its effect on pulmonary compliance, dead space and oxygen delivery are unpredictable making haemodynamic monitoring mandatory. Inversed ratio ventilation requires further evaluation whereas differential lung ventilation is logical, complicated but very valuable where the time constants for each lung are significantly different.     

Bronchopulmonary dysplasia: A new look at an old problem

William Northway Jr. first described bronchopulmonary dysplasia (BPD) in 1967. Even with the many advances in the care of neonatal respiratory diseases BPD has remained a problem, but the gestational age of most affected infants has gradually lowered. Some therapies have been tried and abandoned or remain unproven. BPD in the extremely immature population follows a different pathology than originally described. There appears to be a disruption in lung development. The mechanisms of injury are similar (oxygen toxicity, ventilator-induced injury), with new evidence of perinatal inflammation playing a role. Preventing or minimizing lung injury beyond surfactant may be possible with high frequency oscillatory ventilation or the newer modes of tidal volume ventilation but remains unproven. Avoidance of mechanical ventilation and treatment with only continuous positive airway pressure holds promise. This article is an overview of current knowledge.     

Lung isolation in a child with unilateral necrotizing Clostridium perfringens pneumonia

OBJECTIVE: To describe lung isolation and the selective application of continuous positive airway pressure using an endobronchial blocker in a patient with sickle cell disease and unilateral necrotizing Clostridium perfringens pneumonia. DESIGN: Case report. SETTING: Pediatric intensive care unit. PATIENT: A 12-yr-old male with sickle cell disease developed persistent necrotizing pneumonia of the left lung following exchange transfusion for acute chest syndrome and hyper-hemolytic syndrome. INTERVENTIONS: An endobronchial blocker was placed into the left main stem bronchus for lung isolation and application of continuous positive airway pressure to the left lung for 48 hrs. MEASUREMENTS AND MAIN RESULTS: After 14 days of persistent atelectasis of the left lung despite thorascopic decortication and multiple bronchoscopies, our patient had substantial lung aeration within 48 hrs of continuous positive airway pressure applied via the endobronchial blocker. Lung resection was avoided and the patient was successfully extubated 2 days after removal of the blocker. CONCLUSIONS: This case report demonstrates a therapeutic application of prolonged lung isolation and differential ventilation in a patient with an airway too small for commercially available double-lumen endotracheal tubes. The apparent success of this intervention suggests the feasibility of selective ventilation in pediatric patients and highlights a novel application of the bronchial blocker.     

Unilateral high frequency jet ventilation

A young alcoholic presented with severe bilateral bronchopneumonia, which required prolonged treatment with intermittent positive pressure ventilation. High airway pressures were necessary for effective gas exchange. A recurrent tension pneumothorax led to a persistent bronchopleural fistula which resulted in hypercarbia and hypoxaemia despite the use of large minute volumes. Surgical resection was not considered feasible because of extensive local infection. Asynchronous independent lung ventilation was instituted, using a double-lumen endobronchial tube. A considerable leak still occurred through the bronchopleural fistula, and it was only when high frequency jet ventilation was substituted to the fistula-containing lung that the leak was virtually abolished, while improving gas exchange. High frequency jet ventilation in bronchopleural fistula is of potential benefit.     

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     

高频通气在肺抢救监护病房(PICU)中应用(附25例分析)

我们对PICU中25例危重患儿行高频通气(HFV)32例次(占同期机械通气病人的18.6％)。其中混合高频通气(CHFV)6例次,高频喷射通气(HFJV)10例次,高频正压通气(HFPPV)2例次,经鼻塞高频喷射给氧14例次。年龄范围:1天～10岁,主要原发病:重症肺炎伴呼衰、心衰,心肺复苏后,重症支气管哮喘,呼吸窘迫综合征等。经鼻气管内插管为高频通气主要途经。应用结果显示:经鼻塞高频给氧与普通给氧(口罩或头罩)相比,PaO_2和PaO_2/Fio2值明显上升(P<0.01),PaCO_2和PH无明显变化(P>0.05),混合高频通气组均无CO_2潴留,并提示其所需平均气道压(Paw)和吸气峰压值(PIP)较单纯常频通气时为低。本文对高频通气适应症、高频呼吸器参数的调节略加讨论。并指出:CO_2潴留和呼吸道湿化不足仍是高频喷射通气应用中存在的主要问题,为此可采取与常频通气交替使用,注意调节驱动力和频率等参数和加强气道管理等方法加以解决。     

Airway pressure release ventilation during acute lung injury: a prospective multicenter trial

OBJECTIVE: To evaluate the feasibility of airway pressure release ventilation (APRV) in providing ventilatory support to patients with acute lung injury of diverse etiology and mild-to-moderate severity. DESIGN: Prospective, multicenter, nonrandomized crossover trial. SETTING: ICUs in six major referral hospitals. PATIENTS: Fifty adult patients with respiratory failure requiring mechanical ventilation and positive end-expiratory airway pressure. INTERVENTIONS: After optimization of continuous positive airway pressure (CPAP), conventional ventilation and APRV were administered sequentially for 30 mins. During APRV, the CPAP level and airway pressure release level were adjusted to prevent hypoxemia, while the degree of ventilatory support was adjusted by altering the frequency of pressure release. MEASUREMENTS AND MAIN RESULTS: Circulatory and ventilatory pressures, arterial blood gases and pH, heart rate, and respiratory rate were measured. Alveolar ventilation was augmented adequately in 47 of 50 patients by APRV. Adjustment of APRV required an increase in mean CPAP from 13 +/- 3 (SD) to 21 +/- 9 cm H2O and a release pressure of 6 +/- 5 cm H2O. This airway pressure pattern produced a mean airway pressure comparable to that pressure achieved during conventional ventilation. Failure of APRV in three patients could be attributed to an inadequate level of CPAP or an inadequate APRV rate. While maintaining oxygenation of arterial blood and circulatory function, APRV allowed a substantial (55 +/- 17%; p less than .0001) reduction in peak airway pressure compared with conventional positive pressure ventilation adjusted to deliver a comparable or lower level of ventilatory support. CONCLUSIONS: APRV is a feasible alternative to conventional mechanical ventilation for augmentation of alveolar ventilation in patients with acute lung injury of mild-to-moderate severity.     

机械通气患者应用阶梯性吸痰法的可行性研究

目的 探讨阶梯性吸痰法对机械通气患者氧合及血流动力学的影响.方法 将60例患者随机分为试验组和对照组,每组30例.试验组采用阶梯吸痰法,第1阶梯应用最佳呼气末正压(PEEP);第2阶梯为体外振动排痰;第3阶梯为开放吸痰;第4阶梯为持续气道正压(CPAP)肺复张.对照组采用常规开放吸痰加人工气囊肺复张.试验组和对照组均在60min后进行下一次吸痰,同时监测各时间点血流动力学参数、氧代谢指标、肺机械参数的变化.结果 试验组和对照组吸痰后2h血流动力学指标变化不大,试验组氧合指数、肺机械参数较前明显改善并保持2h以上.结论 阶梯性吸痰法可以明显改善氧合,对正常心功能状态下的血流动力学的影响并不显著.     

Airway pressure release ventilation and pediatrics: theory and practice

Airway pressure release ventilation (APRV) facilitates oxygenation and ventilation by maintaining an elevated baseline airway pressure similar to continuous positive airway pressure (CPAP). APRV differs from CPAP only by the addition of regular, brief release of airway pressure to facilitate carbon dioxide removal. The baseline pressure maintains a near continuous airway pressure to facilitate recruitment, improving ventilation and oxygenation. Pediatric patients who have recruitable lung disease may be well suited to the application of APRV.     

手控高频持续正压通气技术在院前转运新生儿ARDS中的应用效果

目的评价手控高频持续正压通气技术在院前转运新生儿急性呼吸窘迫综合征(ARDS)中的应用效果,为今后推广应用该技术提供依据。方法所有需转运的ARDS新生儿均在解除气道梗阻、循环支持等治疗基础上,根据转运时通气方式不同将其分为治疗组和对照组,每组15例新生儿。治疗组给予SIB+PEEP阀通气设备,采用手控高频持续正压通气;对照组给予SIB设备,采用传统常频手控非持续正压通气。收集两组患儿不同时间点的血气pH、PaO₂、PaCO₂、PaO₂/FiO₂变化情况,统计并发症发生情况和随访60 d的生存情况。结果所有患儿转运成功。重复测量方差分析显示,两组在通气前、后重复测量血气pH、PaO₂、PaO₂/FiO₂比较,差异均有统计学意义(P=0.000)。多变量方差分析显示,通气前,两组患儿血气pH、PaO₂、PaCO₂、PaO₂/FiO₂比较,差异无统计学意义(P>0.05),通气后0.5、1、2、3 h,两组血气pH、PaO₂、PaCO₂、PaO₂/FiO₂比较,差异具有统计学意义(P<0.05)。治疗组并发症总发生率显著低于对照组,差异具有统计学意义(P<0.05)。治疗组的总体生存情况为生存13例,死亡2例;对照组的总体生存情况为生存8例,死亡7例;治疗组的生存率高于对照组。结论SIB+PEEP阀手控高频持续正压通气技术转运ARDS新生儿效果明显,可以显著降低新生儿ARDS的死亡率,适宜推广应用。     

Position of exhalation port and mask design affect CO2 rebreathing during noninvasive positive pressure ventilation

OBJECTIVE: Noninvasive positive pressure ventilation may be considered a first line intervention to treat patients with hypercapnic respiratory failure. However, CO2 rebreathing from the ventilator circuit or mask may impair CO2 elimination and load the ventilatory muscles. This study was conducted to evaluate the effect of exhalation port location and mask design on CO2 rebreathing during noninvasive positive pressure ventilation. DESIGN: Lung model evaluation. SETTING: Experimental laboratory of a large university-affiliated hospital. SUBJECTS: A dual-chamber test lung was used to simulate the ventilatory mechanics of a patient with obstructive lung disease. INTERVENTION: Hypercapnic respiratory failure (end-tidal CO2 of 75 mm Hg) and obstructive lung disease were simulated in a double-chamber lung model. A facial mask (inner volume of 165 mL) with exhalation port within the mask (Facial-MEP) or the same mask with exhalation port in the ventilator circuit (Facial-WS) and a total face mask with exhalation port within the mask (inner volume 875 mL, Total Face) were tested during continuous positive airway pressure and pressure support ventilation provided by a single-limb circuit ventilator at the same frequency and tidal volume. MEASUREMENTS AND MAIN RESULTS: A capnometer and a flow transducer were placed in the lung model upper airway to measure the volume of CO2 rebreathed and tidal volume (Vt). The inspiratory load was estimated from the pressure variation in the lung model driving chamber (PDR). Volume of CO2 rebreathed was smaller during Facial-MEP compared with the other masks in all tested conditions (p <.001). The Vt and PDR necessary to decrease end-tidal CO2 20% (from 75 to 60 mm Hg) was different among the tested masks (Facial-MEP, Vt 701 +/- 9 mL, PDR 8.1 +/- 0.1 cm H2O/sec; Facial-WS, Vt 745 +/- 9 mL, PDR 10.2 +/- 0.1 cm H2O/sec; Total Face, Vt 790 +/- 12 mL, PDR 11.4 +/- 0.2 cm H2O/sec, p <.001). CONCLUSION: Facial-MEP with its exhalation port within the mask and the smallest mask volume demonstrated less rebreathed CO2 and a lower PDR than either the Facial-WS or Total Face masks. Additional studies are necessary to confirm if mask design can clinically affect patient's inspiratory effort during noninvasive positive pressure ventilation.     

A study of a complex ARDS patient

With a high percentage of ICU patients suffering from ARDS from a direct or indirect lung injury, successful therapy and treatment modalities are important for all of us to know. It is our hope, as critical care professionals, to assist the patient through the course of this complication and prevent further lung injury related to the increasing oxygen demands, high positive pressure ventilation, and high volumes. When traditional methods of improving ventilation fail, we do have the options of proning our patients and/or trying high frequency oscillating ventilation to optimize oxygen exchange. The authors outline the course of events surrounding the care of a young patient with ARDS over 44 days in ICU. Proning, high frequency ventilation, and the use of steroids played a role in the recovery of Mr. M. Aggressive nursing care helped minimize the complications from these treatments and aided in the psychosocial aspects of a challenging family dynamic.     

纤维支气管镜肺灌洗联合机械正压通气对重症肺不张患者的治疗研究

目的:研究纤维支气管镜肺灌洗联合机械正压通气对重症肺不张患者的治疗可行性及治疗效果。方法:对31例重症肺不张患者在综合治疗的基础上行机械通气和纤维支气管镜肺灌洗,监测患者生命体征、动脉血气分析,对治疗前后各项指标及临床情况进行对比分析。术后继续持续气道正压机械通气治疗,治疗后第3天复查胸部CT,对病情严重患者进行二次灌洗。结果:术中10%患者会出现血压升高,脉氧短暂轻度下降,心率增快,但所有患者都能顺利完成治疗。治疗前后各项生命体征基本平稳,多数指标变化不大,氧合指标有明显改善,复查胸部CT显示肺复张率达90%。结论:纤维支气管镜肺灌洗联合机械正压通气治疗重症肺不张是安全有效的方法。     

Effects of cyclic opening and closing at low- and high-volume ventilation on bronchoalveolar lavage cytokines

OBJECTIVE: To examine the mechanisms of ventilator-induced lung injury at low and high lung volumes. DESIGN: Prospective, randomized, laboratory study. SETTING: University research laboratory. SUBJECTS: Eighty-eight adult male Sprague-Dawley rats. INTERVENTIONS: Mechanical ventilation using low and high lung volumes. MEASUREMENTS AND MAIN RESULTS: An ex vivo rat lung model was used. In study I (ventilation at low lung volumes), rat lungs (n = 40) were randomly assigned to various modes of ventilation: a) opening and closing with positive end-expiratory pressure (PEEP; control): tidal volume 7 mL/kg and PEEP 5 cm H2O; b) opening and closing from zero end-expiratory pressure (ZEEP): tidal volume 7 mL/kg and PEEP 0; or c) atelectasis. Peak inspiratory pressure was monitored at the beginning and end of 3 hrs of ventilation. At the end of 3 hrs of ventilation, the lungs were lavaged, and the concentrations of tumor necrosis factor-alpha, macrophage inflammatory protein-2, and interleukin-6 cytokines were measured in the lavage. In study II (ventilation at high volumes), rat lungs (n = 45) were randomly assigned to a) cyclic lung stretch: pressure-controlled ventilation, peak inspiratory pressure 50 cm H2O, and PEEP 8 cm H2O; b) continuous positive airway pressure at 50 cm H2O (CPAP50); or c) CPAP at the mean airway pressure of the cyclic stretch group (CPAP 31 cm H2O). Bronchoalveolar lavage cytokine concentrations (tumor necrosis factor-alpha, macrophage inflammatory protein-2, and interleukin-6) were measured at the end of 3 hrs of ventilation. In the low volume study, there was no difference in bronchoalveolar lavage cytokine concentrations between the PEEP group and the atelectatic group. All cytokines were significantly higher in the ZEEP group compared with the atelectasis group. Macrophage inflammatory protein-2 was significantly higher in the ZEEP group compared with the PEEP group. Lung compliance, as reflected by change in peak inspiratory pressure, was also significantly worse in the ZEEP compared with the PEEP group. In the high-volume study, tumor necrosis factor-alpha and interleukin-6 were significantly higher in the cyclic stretch group compared with the CPAP 31 group. There was no significant difference between the cytokine concentrations in the cyclic stretch group compared with the CPAP 50 group. CONCLUSION: We conclude that at low lung volumes, cyclic opening and closing from ZEEP leads to greater increases in bronchoalveolar lavage cytokines than atelectasis. With high-volume ventilation, over time, the degree of overdistension is more associated with increases in bronchoalveolar lavage cytokines than cyclic opening and closing alone.     

Insights in pediatric ventilation: timing of intubation, ventilatory strategies, and weaning

PURPOSE OF REVIEW: Mechanical ventilation is a common intervention provided by pediatric intensivists. This fact notwithstanding, the management of mechanical ventilation in pediatrics is largely guided by a few pediatric trials along with careful interpretation and application of adult data. RECENT FINDINGS: A low tidal volume, pressure limited approach to mechanical ventilation as established by the Acute Respiratory Distress Syndrome Network investigators, has become the prevailing practice in pediatric intensive care. Studies by these investigators suggest that high positive end expiratory pressure and recruitment maneuvers are not uniformly beneficial. High frequency oscillatory ventilation continues to be evaluated in an attempt to provide 'open lung' ventilation. Airway pressure release ventilation is a newer mode of ventilation that may combine the 'open lung' approach with spontaneous breathing. Prone positioning was demonstrated in a recent pediatric trial to have no effect on outcome, while calfactant was found to potentially improve outcomes in pediatric acute respiratory distress syndrome. Ventilator weaning protocols may not be as useful in pediatrics as in adults. Systemic corticosteroids decrease the incidence of post extubation stridor and may reduce reintubation rates. SUMMARY: Mechanical ventilation with pressure limitation and low tidal volumes has become customary in pediatric intensive care units, and this lung protective approach will continue into the foreseeable future. Further investigation is warranted regarding use of high frequency oscillatory ventilation, airway pressure release ventilation, and surfactant to assist pediatric intensivists in application of these therapies.     

A simple technique for managing a bronchopleural fistula while maintaining positive pressure ventilation.

The development of a bronchopleural fistula (BPF) is an infrequent, but potentially devastating complication of positive pressure ventilation. A case report is detailed in which a BPF arose in a patient on controlled ventilation with a PEEP of 22 cm H2O. Within 12 hours, fistula flow was continuous and accounted for 75% of the delivered tidal volume. PEEP fell rapidly during expiration; oxygenation steadily deteriorated as the aAO2 fell 0.27 to 0.14. Conventional treatment methods were unsuccessful, and a system was constructed for adding controlled levels of positive pressure ot the pleural space on the side of the BPF. By decreasing the expiratory transpulmonary pressure difference (PEEP minus pleural pressure), the fistula leak was greatly decreased, and PEEP and oxygenation were stabilized. This system can be rapidly constructed at the bedside with equipment routinely available in most hospitals and offers the ability to adjust the expiratory transpulmonary pressure, lung volume, and BPF flow while maintaining positive pressure ventilation with PEEP.     

Cardiorespiratory effects of an inspiratory hold and continuous positive pressure ventilation in goats

The cardiorespiratory effects of three different patterns of mechanical ventilation were compared in sixteen anaesthetized goats. Intermittent positive pressure ventilation (IPPV), with an inspiratory: expiratory (I:E) time ratio of 1:3, was compared with an inspiratory hold pattern (IPPVH), with an I:E ratio of 3:1, and with continuous positive pressure ventilation (CPPV) adjusted to produce the same mean airway pressure. In eight animals with normal lungs, IPPVH reduced VD/VT and PaCO2, but produced no changes in oxygenation. CPPV did not significantly alter the efficiency of gas exchange. In a further eight animals, with oleic acid-induced lung damage, both IPPVH and CPPV produced a decrease in both VD/VT and PaCO2. Qs/Qt was significantly reduced by both CPPV and IPPVH, but the effect was more marked with CPPV, and the PaO2 was significantly increased only by CPPV. The increased effectiveness of CPPV in increasing PaO2 in this model may have been due to the greater increase in end-expiratory lung volume produced by this pattern of ventilation.     

高频部分液体通气治疗吸入性肺损伤的实验研究

目的：观察高频部分液体通气治疗吸入性肺损伤的效果,并与单纯高频喷射通气的疗效比较。方法：将16只犬经蒸气吸入造成吸入性肺损伤模型,并随机分为对照组和治疗组。2组动物致伤后均行高频喷射通气,治疗组动物同时经气管导管将氟碳液体（3ml/kg)缓慢注入肺内,实行高频部分液体通气治疗,于30、60及90分钟测定动脉血气、肺顺应性和气道阻力。结果：治疗组动脉血氧分压（PaO2)进行性上升,各时间点与致伤后比较均有显著性差异（P均＜0．05）,动脉血二氧化碳分压（PaCO2)也逐渐增高,于60和90分钟显著高于致伤后水平（P均＜0．05）;与对照组比较,治疗组各时间点的PaO2稍有升高,而PaCO2于90分钟显著增高（P＜0．05）。在各时间点的动、静态气道阻力和动、静态肺顺应性,2组比较均无明显差异。结论：高频部分液体通气与单纯高频喷射通气相比,更有利于动脉血氧合,但也有轻度CO2潴留现象。     

Regional lung aeration and ventilation during pressure support and biphasic positive airway pressure ventilation in experimental lung injury

Introduction  

There is an increasing interest in biphasic positive airway pressure with spontaneous breathing (BIPAP+SB_mean), which is a combination of time-cycled controlled breaths at two levels of continuous positive airway pressure (BIPAP+SB_controlled) and non-assisted spontaneous breathing (BIPAP+SB_spont), in the early phase of acute lung injury (ALI). However, pressure support ventilation (PSV) remains the most commonly used mode of assisted ventilation. To date, the effects of BIPAP+SB_mean and PSV on regional lung aeration and ventilation during ALI are only poorly defined.