The growing role of noninvasive ventilation in patients requiring prolonged mechanical ventilation

For many patients with chronic respiratory failure requiring ventilator support, noninvasive ventilation (NIV) is preferable to invasive support by tracheostomy. Currently available evidence does not support the use of nocturnal NIV in unselected patients with stable COPD. Several European studies have reported benefit for high intensity NIV, in which setting of inspiratory pressure and respiratory rate are selected to achieve normocapnia. There have also been studies reporting benefit for the use of NIV as an adjunct to exercise training. NIV may be useful as an adjunct to airway clearance techniques in patients with cystic fibrosis. Accumulating evidence supports the use of NIV in patients with obesity hypoventilation syndrome. There is considerable observational evidence supporting the use of NIV in patients with chronic respiratory failure related to neuromuscular disease, and one randomized controlled trial reported that the use of NIV was life-prolonging in patients with amyotrophic lateral sclerosis. A variety of interfaces can be used to provide NIV in patients with stable chronic respiratory failure. The mouthpiece is an interface that is unique in this patient population, and has been used with success in patients with neuromuscular disease. Bi-level pressure ventilators are commonly used for NIV, although there are now a new generation of intermediate ventilators that are portable, have a long battery life, and can be used for NIV and invasive applications. Pressure support ventilation, pressure controlled ventilation, and volume controlled ventilation have been used successfully for chronic applications of NIV. New modes have recently become available, but their benefits await evidence to support their widespread use. The success of NIV in a given patient population depends on selection of an appropriate patient, selection of an appropriate interface, selection of an appropriate ventilator and ventilator settings, the skills of the clinician, the motivation of the patient, and the support of the family.     

Heliox in upper airway obstruction

The use of a helium-oxygen (heliox) mixture in patients with airway obstruction was used as early as the 1930s. Although heliox does not resolve airway obstruction, it decreases airway resistance providing time to allow other treatments to become therapeutic, and thus, possibly preventing the need for intubation and mechanical ventilation. Despite new and advanced treatment options in airway obstruction, heliox continues to be a choice for treatment. It is important for critical care nurses to understand the rationale for the use of heliox, the mechanism of action and administration of heliox. Through a case study, the authors discuss the physical properties of helium and its use in airway obstruction. Nursing management of patients receiving heliox is also reviewed.     

Noninvasive ventilation in neuromuscular disease: equipment and application

Noninvasive support of ventilation is commonly needed in patients with neuromuscular disease. Body ventilators, which are used rarely, function by applying intermittent negative pressure to the thorax or abdomen. More commonly, noninvasive positive-pressure ventilation (NPPV) is used. This therapy can be applied with a variety of interfaces, ventilators, and ventilator settings. The patient interface has a major impact on comfort during NPPV. The most commonly used interfaces are nasal masks and oronasal masks. Other interfaces include nasal pillows, total face masks, helmets, and mouthpieces. Theoretically, any ventilator can be attached to a mask rather than an artificial airway. Portable pressure ventilators (bi-level positive airway pressure) are available specifically to provide NPPV and are commonly used to provide this therapy. Selection of NPPV settings in patients with neuromuscular disease is often done empirically and is symptom-based. Selection of settings can also be based on the results of physiologic studies or sleep studies. The use of NPPV in this patient population is likely to expand, particularly with increasing evidence that it is life-prolonging in patients with diseases such as amyotrophic lateral sclerosis. Appropriate selection of equipment and settings for NPPV is paramount to the success of this therapy.     

Noninvasive ventilation and the upper airway: should we pay more attention?

In an effort to reduce the complications related to invasive ventilation, the use of noninvasive ventilation (NIV) has increased over the last years in patients with acute respiratory failure. However, failure rates for NIV remain high in specific patient categories. Several studies have identified factors that contribute to NIV failure, including low experience of the medical team and patient–ventilator asynchrony. An important difference between invasive ventilation and NIV is the role of the upper airway. During invasive ventilation the endotracheal tube bypasses the upper airway, but during NIV upper airway patency may play a role in the successful application of NIV. In response to positive pressure, upper airway patency may decrease and therefore impair minute ventilation. This paper aims to discuss the effect of positive pressure ventilation on upper airway patency and its possible clinical implications, and to stimulate research in this field.     

Mechanical effects of airway humidification devices in difficult to wean patients

OBJECTIVE: To evaluate the influence of airway humidification devices on the efficacy of ventilation in difficult to wean patients. DESIGN: A prospective, randomized, controlled physiologic study. SETTING: A 22-bed medical intensive care unit in a university hospital. PATIENTS: Chronic respiratory failure patients. INTERVENTIONS: Performances of a heated humidifier and a heat and moisture exchanger were evaluated on diaphragmatic muscle activity, breathing pattern, gas exchange, and respiratory comfort during weaning from mechanical ventilation by using pressure support ventilation. Eleven patients with chronic respiratory failure were submitted to four pressure support ventilation sequences by using the heated humidifier and the heat and moisture exchanger at two different levels of pressure support ventilation (7 and 15 cm H(2)O). MEASUREMENT AND MAIN RESULTS: Compared with the heated humidifier and regardless of the pressure support ventilation level used, the heat and moisture exchanger significantly increased all of the inspiratory effort variables (inspiratory work of breathing expressed in J/L and J/min, pressure time product, changes in esophageal pressure, and transdiaphragmatic pressure; p <.05) and dynamic intrinsic positive end-expiratory pressure (p <.05). Similarly, the heat and moisture exchanger produced a significant increase in Paco(2) (p <.01) responsible for severe respiratory acidosis (p <.05), which was insufficiently compensated for despite a significant increase in minute ventilation (p <.05). This resulted in respiratory discomfort for all patients with the heat and moisture exchanger (p <.01). Adverse effects were partially counterbalanced by increasing the pressure support ventilation level with the heat and moisture exchanger by >or=8 cm H(2)O. CONCLUSIONS: The type of airway humidification device used may negatively influence the mechanical efficacy of ventilation and, unless the pressure support ventilation level is considerably increased, the use of a heat and moisture exchanger should not be recommended in difficult or potentially difficult to wean patients with chronic respiratory failure.     

Non‐invasive positive pressure ventilation in patients with acute respiratory failure

Non‐invasive positive pressure ventilation is an emerging modality in contemporary critical care practice. Perhaps the most widely utilized and familiar form of non‐invasive positive pressure ventilation is mask continuous positive airway pressure. Other common modes include mask Bi‐level positive airway pressure and mask pressure support ventilation. All feature the delivery of positive airway pressure via a mask (full‐face, naso‐oral or nasal), and a patient‐controlled respiratory cycle. The physiological benefits of non‐invasive positive pressure ventilation suggested by a number of studies include improved oxygenation, decreased work of breathing, improved ventilation and perfusion matching, decreased fatigue, and increased minute ventilation. The utilization of non‐invasive positive pressure ventilation has now been reported for a variety of clinical indications. In most, randomized trials are lacking, and the benefits and preferred mode of non‐invasive positive pressure ventilation are still to be elucidated. In general, in patients that are candidates for endotracheal intubation, non‐invasive positive pressure ventilation should be used as a way to possibly avoid endotracheal intubation rather than as an alternative to endotracheal intubation. Whilst the benefit of non‐invasive positive pressure ventilation appears to be established in patients with chronic obstructive airways disease with hypercapnic acute respiratory failure, one of the major unresolved issues is whether one modality is significantly better than the others. Unfortunately, the question of whether Bi‐level positive airway pressure is better than continuous positive airway pressure in this clinical scenario has not been satisfactorily addressed in any large randomized and controlled clinical trial. Further, there is no ‘gold standard’ for predicting success with non‐invasive positive pressure ventilation, although several studies have looked at this aspect.     

New approaches in the rehabilitation of the traumatic high level quadriplegic

The use of noninvasive alternatives to tracheostomy for ventilatory support have been described in the patient management of various neuromuscular disorders. The use of these techniques for patients with traumatic high level quadriplegia, however, is hampered by the resort to tracheostomy in the acute hospital setting. Twenty traumatic high level quadriplegic patients on intermittent positive pressure ventilation (IPPV) via tracheostomy with little or no ability for unassisted breathing were converted to noninvasive ventilatory support methods and had their tracheostomy sites closed. Four additional patients were ventilated by noninvasive methods without tracheostomy. These methods included the use of body ventilators and the noninvasive intermittent positive airway pressure alternatives of IPPV via the mouth, nose, or custom acrylic strapless oral-nasal interface (SONI). Overnight end-tidal pCO2 studies and monitoring of oxyhemoglobin saturation (SaO2) were used to adjust ventilator volumes and to document effective ventilation during sleep. No significant complications have resulted from the use of these methods over a period of 45 patient-years. Elimination of the tracheostomy permitted significant free time by glossopharyngeal breathing for four patients, two of whom had no measurable vital capacity. We conclude that noninvasive ventilatory support alternatives can be effective and deserve further study in this patient population.     

The role of noninvasive ventilation: CPAP and BiPAP in the treatment of congestive heart failure.

Congestive heart failure (CHF) is a common cause of respiratory failure for which patients seek emergency care. Mechanical ventilation is commonly used in the treatment for severe CHF. Studies have shown that noninvasive ventilation (NIV) methods, such as continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BiPAP), are effective in treating CHF and have fewer complications than endotracheal intubation. The use of NIV in the treatment of CHF has been shown to increase oxygenation, improve hemodynamic stability, and decrease the need for intubation. When NIV is chosen for a patient in CHF, the critical care nurse needs to be vigilant in assessing and monitoring these patients, especially those in severe CHF. This article evaluates the differences between the 2 types of NIV, the controversies that may exist, practice issues for the critical care nurse, and any financial considerations.     

The respiratory system during resuscitation: a review of the history, risk of infection during assisted ventilation, respiratory mechanics, and ventilation strategies for patients with an unprotected airway

The fear of acquiring infectious diseases has resulted in reluctance among healthcare professionals and the lay public to perform mouth-to-mouth ventilation. However, the benefit of basic life support for a patient in cardiopulmonary or respiratory arrest greatly outweighs the risk for secondary infection in the rescuer or the patient. The distribution of ventilation volume between lungs and stomach in the unprotected airway depends on patient variables such as lower oesophageal sphincter pressure, airway resistance and respiratory system compliance, and the technique applied while performing basic or advanced airway support, such as head position, inflation flow rate and time, which determine upper airway pressure. The combination of these variables determines gas distribution between the lungs and the oesophagus and subsequently, the stomach. During bag-valve-mask ventilation of patients in respiratory or cardiac arrest with oxygen supplementation (> or = 40% oxygen), a tidal volume of 6-7 ml kg(-1) ( approximately 500 ml) given over 1-2 s until the chest rises is recommended. For bag-valve-mask ventilation with room-air, a tidal volume of 10 ml kg(-1) (700-1000 ml) in an adult given over 2 s until the chest rises clearly is recommended. During mouth-to-mouth ventilation, a breath over 2 s sufficient to make the chest rise clearly (a tidal volume of approximately 10 ml kg(-1) approximately 700-1000 ml in an adult) is recommended.     

Clinical review: Long-term noninvasive ventilation

Noninvasive positive ventilation has undergone a remarkable evolution over the past decades and is assuming an important role in the management of both acute and chronic respiratory failure. Long-term ventilatory support should be considered a standard of care to treat selected patients following an intensive care unit (ICU) stay. In this setting, appropriate use of noninvasive ventilation can be expected to improve patient outcomes, reduce ICU admission, enhance patient comfort, and increase the efficiency of health care resource utilization. Current literature indicates that noninvasive ventilation improves and stabilizes the clinical course of many patients with chronic ventilatory failure. Noninvasive ventilation also permits long-term mechanical ventilation to be an acceptable option for patients who otherwise would not have been treated if tracheostomy were the only alternative. Nevertheless, these results appear to be better in patients with neuromuscular/-parietal disorders than in chronic obstructive pulmonary disease. This clinical review will address the use of noninvasive ventilation (not including continuous positive airway pressure) mainly in diseases responsible for chronic hypoventilation (that is, restrictive disorders, including neuromuscular disease and lung disease) and incidentally in others such as obstructive sleep apnea or problems of central drive.     

A protocol for high-frequency oscillatory ventilation in adults: results from a roundtable discussion

OBJECTIVE: Ventilator settings typically used for high-frequency oscillatory ventilation (HFO) in adults provide acceptable gas exchange but may not take best advantage of its lung-protective aspects. We provide guidelines for HFO in adults with acute respiratory distress syndrome that should optimize the lung-protective characteristics of this ventilation mode. DESIGN: Roundtable discussions, iterative revisions, and consensus. SETTING: Five academic medical centers. PATIENTS: Not applicable. INTERVENTIONS: Participants addressed how to best maintain ventilation through combinations of oscillation pressure amplitude, frequency, and the use of an endotracheal tube cuff leak, and to maintain oxygenation through combinations of recruitment maneuvers, mean airway pressure, and oxygen concentration. The guiding principles were to provide lung protective ventilation by minimizing the size of tidal volumes, and balance the risks and benefits of lung recruitment and distension. MAIN RESULTS: HFO may provide smaller tidal volumes and more complete lung recruitment than conventional modes. To optimize these features, we recommend use of the maximum pressure-oscillation amplitude coupled with the highest tolerated frequency, targeting a pH of only 7.25-7.35. This will yield a smaller tidal volume than typical HFO settings where frequency is limited to 6 Hz or less and pressure amplitude is submaximal. Lung recruitment can be achieved with the use of recruitment maneuvers, especially during the first several days of HFO. Recruitment may be augmented or sustained with generous mean airway pressures. These may either be chosen from a table of recommended mean airway pressure and oxygen concentration combinations, or individually titrated based on the oxygenation response of each patient. CONCLUSIONS: Modification of the goals and tactics of HFO use may better protect against ventilator-associated lung injury. Further clinical trials are needed to compare the effects on patient outcome of the best use of HFO compared to the most protective use of conventional modes in adult acute respiratory distress syndrome.     

Home negative pressure ventilation: report of 20 years of experience in patients with neuromuscular disease

Twenty years of experience using negative pressure devices (NPD) at home to ventilate 40 patients with neuromuscular disease is presented. The purpose of the study was to determine the costs, complications, and clinical outcome of this form of respiratory support, and to ascertain the reasons for failure to institute effective negative pressure ventilation (NPV) in nine patients. Emerson tank respirators, used mainly to rest respiratory muscles at night, and intermittent positive pressure breathing machines were used by 98% of patients at an average equipment cost of +2,700 annually. Patients in whom NPV was initiated on an elective rather than emergent basis saved an average of +12,000 during their initial hospitalization. Life table analysis shows a five-year survival of 76%, and a 10-year survival of 61%. Complications were minor and occurred at an average rate of less than one per year per patient at home on NPV. Failure to achieve satisfactory NPV in nine patients was associated with age (six patients were younger than 3 years of age), or severe thoracocervical scoliosis, which prevented proper fitting of the NPD. For reasons of safety, economy, and quality of life, NPV at home is the preferred treatment for patients having neuromuscular disease who need respiratory assistance.     

Prediction of post-extubation work of breathing

OBJECTIVE: To evaluate which mode of preextubation ventilatory support most closely approximates the work of breathing performed by spontaneously breathing patients after extubation. DESIGN: Prospective observational design. SETTING: Medical, surgical, and coronary intensive care units in a university hospital. PATIENTS: A total of 22 intubated subjects were recruited when weaned and ready for extubation. INTERVENTIONS: Subjects were ventilated with continuous positive airway pressure at 5 cm H2O, spontaneous ventilation through an endotracheal tube (T piece), and pressure support ventilation at 5 cm H2O in randomized order for 15 mins each. At the end of each interval, we measured pulmonary mechanics including work of breathing reported as work per liter of ventilation, respiratory rate, tidal volume, negative change in esophageal pressure, pressure time product, and the airway occlusion pressure 100 msec after the onset of inspiratory flow, by using a microprocessor-based monitor. Subsequently, subjects were extubated, and measurements of pulmonary mechanics were repeated 15 and 60 mins after extubation. MEASUREMENTS AND MAIN RESULTS: There were no statistical differences between work per liter of ventilation measured during continuous positive airway pressure, T piece, or pressure support ventilation (1.17+/-0.67 joule/L, 1.11+/-0.57 joule/L, and 0.97+/-0.57 joule/L, respectively). However, work per liter of ventilation during all three preextubation modes was significantly lower than work measured 15 and 60 mins after extubation (p < .05). Tidal volume during pressure support ventilation and continuous positive airway pressure (0.46+/-0.11 L and 0.44+/-0.11 L, respectively) were significantly greater than tidal volume during both T-piece breathing and spontaneous breathing 15 mins after extubation (p < .05). Negative change in esophageal pressure, the airway occlusion pressure 100 msec after the onset of inspiratory flow, and pressure time product were significantly higher after extubation than during any of the three preextubation modes (p < .05). CONCLUSIONS: Work per liter of ventilation, negative change in esophageal pressure, the airway occlusion pressure 100 msec after the onset of inspiratory flow, and pressure time product all significantly increase postextubation. Tidal volume during continuous positive airway pressure or pressure support ventilation overestimates postextubation tidal volume.     

Our paper 20 years later: how has withdrawal from mechanical ventilation changed?

Withdrawal from mechanical ventilation (or weaning) is one of the most common procedures in intensive care units. Almost 20 years ago, we published one of the seminal papers on weaning in which we showed that the best method for withdrawal from mechanical ventilation in difficult-to-wean patients was a once-daily spontaneous breathing trial with a T-piece. Progress has not stood still, and in the intervening years up to the present several other studies, by our group and others, have shaped weaning into an evidence-based technique. The results of these studies have been applied progressively to routine clinical practice. Currently, withdrawal from mechanical ventilation can be summarized as the evaluation of extubation readiness based on the patient’s performance during a spontaneous breathing trial. This trial can be performed with a T-piece, which is the most common approach, or with continuous positive airway pressure or low levels of pressure support. Most patients can be disconnected after passing the first spontaneous breathing trial. In patients who fail the first attempt at withdrawal, the use of a once-daily spontaneous breathing trial or a gradual reduction in pressure support are the preferred weaning methods. However, new applications of standard techniques, such as noninvasive positive pressure ventilation, or new methods of mechanical ventilation, such as automatic tube compensation, automated closed-loop systems, and automated knowledge-based weaning systems, can play a role in the management of the patients with difficult or prolonged weaning.     

Pressure support ventilation

The management of patients with respiratory failure can be challenging. A relatively new technique may be useful in freeing these patients from mechanical ventilation. With a spontaneously taken breath, positive pressure is provided by a ventilator equipped to detect small changes in airway pressure. Pressure support ventilation may mean the difference between an independent life and ventilator dependency.     

适当呼气末正压及不同通气模式对肝移植患者血流动力学和氧代谢动力学的影响

目的 寻找适宜的呼气末正压(PEEP),研究不同机械通气方式对肝移植术后患者血流动力学及氧代谢动力学的影响.方法 采用随机、单盲、交叉试验方法.选取11例背驮式肝移植术后呼吸机辅助通气患者为观察对象,经漂浮导管、桡动脉导管进行持续心排血量(CO)、平均肺动脉压(MPAP)、平均动脉血压(MABP)、中心静脉压(CVP)和气道压力监测.压力调节容量控制通气(PRVCV)的PEEP定为0、5、10和15 cm H2O(1 cm H2O=0.098 kPa),不同水平PEEP各用30 min;交替使用PRVCV和压力控制同步间歇指令通气加压力支持通气(PC-SIMV+PSV)各60 min;观察4种PEEP水平和两种通气模式下血流动力学和氧代谢动力学指标的变化.结果 不同水平PEEP时肝移植术后患者气道峰压、平均气道压、CVP及MPAP差异均有显著性,其中在PEEP为10 cm H2O和15 cm H2O时显著高于PEEP为0和5 cm H2O时;不同水平PEEP对pH、动脉血二氧化碳分压(PaCO2)、动脉血氧分压(PaO2)、动脉血氧饱和度(SaO2)、氧供给(DO2)、氧消耗(VO2)、氧摄取率(O2ER)均无明显影响.PRVCV模式时平均气道压明显低于PC-SIMV+PSV模式[(8.78±1.53)cm H2O比(11.64±3.30)cm H2O,P＜0.05];PRVCV模式时VO2虽低于PC-SIMV+PSV模式,但差异无显著性.两种通气模式对患者的其他血流动力学指标以及氧代谢动力学指标并无显著影响.结论 为减少对患者体循环及移植肝脏血液回流的影响,肝移植术后患者通气支持时宜选用5 cm H2O的低水平PEEP.PRVCV模式可作为肝移植术后患者呼吸支持和脱机过渡较为理想的通气模式.     

Bedside waveforms interpretation as a tool to identify patient-ventilator asynchronies

Objective During assisted modes of ventilatory support the ventilatory output is the final expression of the interaction between the ventilator and the patients controller of breathing. This interaction may lead to patient-ventilator asynchrony, preventing the ventilator from achieving its goals, and may cause patient harm. Flow, volume, and airway pressure signals are significantly affected by patient-ventilator interaction and may serve as a tool to guide the physician to take the appropriate action to improve the synchrony between patient and ventilator. This review discusses the basic waveforms during assisted mechanical ventilation and how their interpretation may influence the management of ventilated patients. The discussion is limited on waveform eye interpretation of the signals without using any intervention which may interrupt the process of mechanical ventilation.Discussion Flow, volume, and airway pressure may be used to (a) identify the mode of ventilator assistance, triggering delay, ineffective efforts, and autotriggering, (b) estimate qualitatively patients respiratory efforts, and (c) recognize delayed and premature opening of exhalation valve. These signals may also serve as a tool for gross estimation of respiratory system mechanics and monitor the effects of disease progression and various therapeutic interventions.Conclusions Flow, volume, and airway pressure waveforms are valuable real-time tools in identifying various aspects of patient-ventilator interactionElectronic Supplementary Material Electronic supplementary material to this paper can be obtained by using the Springer Link server located at     

Second- and third-generation ventilators: sorting through available options. When, and for which patients, are special functions needed?

Currently available ventilators offer a number of special options to meet the needs of critically ill patients. Intermittent mandatory ventilation allows a patient to breathe spontaneously without assistance. CPAP and PEEP ensure that the patient breathes at an elevated pressure either constantly or during expiration. Pressure support ventilation allows patients to participate in breathing but provides inspiratory assistance and is most useful during weaning. Airway pressure release ventilation facilitates venous return and decreases airway pressure. Sophisticated monitors provide detailed information on the patient's status, but alarm features are somewhat unreliable. Thorough knowledge of the controls on modern ventilators can help you provide the optimum form of respiratory support.     

Using non-invasive ventilation in acute wards: Part 1

Non-invasive ventilation (NIV) is increasingly being used in domestic and acute health settings. Part one of this article identifies the benefits of NIV and describes the use of continuous positive airway pressure (CPAP). Part two, published in next week's Nursing Standard, discusses bilevel NIV, which has fewer complications and so is largely replacing CPAP. Part two also examines how to monitor and assess patients receiving NIV.     

Ventilator strategies for posttraumatic acute respiratory distress syndrome: airway pressure release ventilation and the role of spontaneous breathing in critically ill patients

PURPOSE OF REVIEW: Patients who experience severe trauma are at increased risk for the development of acute lung injury and acute respiratory distress syndrome. The management strategies used to treat respiratory failure in this patient population should be comprehensive. Current trends in the management of acute lung injury and acute respiratory distress syndrome consist of maintaining acceptable gas exchange while limiting ventilator-associated lung injury. RECENT FINDINGS: Currently, two distinct forms of ventilator-associated lung injury are recognized to produce alveolar stress failure and have been termed low-volume lung injury (intratidal alveolar recruitment and derecruitment) and high-volume lung injury (alveolar stretch and overdistension). Pathologically, alveolar stress failure from low- and high-volume ventilation can produce lung injury in animal models and is termed ventilator-induced lung injury. The management goal in acute lung injury and acute respiratory distress syndrome challenges clinicians to achieve the optimal balance that both limits the forms of alveolar stress failure and maintains effective gas exchange. The integration of new ventilator modes that include the augmentation of spontaneous breathing during mechanical ventilation may be beneficial and may improve the ability to attain these goals. SUMMARY: Airway pressure release ventilation is a mode of mechanical ventilation that maintains lung volume to limit intra tidal recruitment /derecruitment and improves gas exchange while limiting over distension. Clinical and experimental data demonstrate improvements in arterial oxygenation, ventilation-perfusion matching (less shunt and dead space ventilation), cardiac output, oxygen delivery, and lower airway pressures during airway pressure release ventilation. Mechanical ventilation with airway pressure release ventilation permits spontaneous breathing throughout the entire respiratory cycle, improves patient comfort, reduces the use of sedation, and may reduce ventilator days.