Respir Care Clin N Am
· 2002 Sep · PMID 12481963
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V(A)/Q mismatching and load/capacity imbalance are the major physiologic determinants of chronic respiratory failure. The former underlies lung failure and the consequent development of hypoxemia. The latter causes chron...V(A)/Q mismatching and load/capacity imbalance are the major physiologic determinants of chronic respiratory failure. The former underlies lung failure and the consequent development of hypoxemia. The latter causes chronic ventilatory failure and hypercapnia. This is the consequence of an inefficient breathing pattern with lower VT and higher respiratory rate, probably due to the "wise choice" of preventing excessive inspiratory effort and eventually respiratory muscle fatigue. In many disorders, V(A)/Q mismatching and the load/capacity imbalance coexist, particularly in COPD, where the interplay between the two pathophysiologically represents the advanced stage of the disease. In other disorders, one of the two mechanisms prevails; for example, V(A)/Q mismatching in pure lung diseases, and chest wall mechanics in thoracic disorders. This has important therapeutic implications because oxygen administration can relieve hypoxemia, whereas mechanical ventilation can prevent excessive hypercapnia and respiratory acidosis. Although the role of oxygen therapy is well established, the role of chronic mechanical ventilation is still a matter of debate, particularly in COPD. A major task for future research is to achieve the best possible understanding of the pathophysiologic factors predisposing to chronic ventilatory failure, to prevent the progression of the respiratory diseases to the stage when chronic respiratory failure eventually develops.
Respir Care Clin N Am
· 2002 Sep · PMID 12481962
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The reports published to date support the concept that LTMV can extend life for patients with respiratory insufficiency, particularly adults and children with neuromuscular and chest wall diseases. The impact of LTMV on...The reports published to date support the concept that LTMV can extend life for patients with respiratory insufficiency, particularly adults and children with neuromuscular and chest wall diseases. The impact of LTMV on survival in patients with obstructive lung diseases, such as COPD and bronchiectasis, is less clear and deserves further study. For all disease states, research is needed to determine the characteristics of patients who are most likely to benefit from LTMV and whether one method of ventilation is superior to another. In addition to survival, other important outcomes, such as patient satisfaction, quality of life, and costs associated with LTMV, should be assessed in future long-term studies.
Respir Care Clin N Am
· 2002 Sep · PMID 12481961
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An increasing number of patients are receiving prolonged ventilation worldwide. The excessive financial burden associated with chronic ventilation hinders effective discharge from the intensive care unit to any other alt...An increasing number of patients are receiving prolonged ventilation worldwide. The excessive financial burden associated with chronic ventilation hinders effective discharge from the intensive care unit to any other alternative site of care or to the home. The beneficial outcome of caring for chronic ventilator-dependent patients relies on the organization of the treatment team, quality of the medical and rehabilitative treatment programs, and leadership of the medical director. These patients require a highly organized and integrated care plan that has sufficient and prolonged administrative oversight to ensure optimum outcome and reduce costs.
Respir Care Clin N Am
· 2002 Jun · PMID 12481822
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Aerosol medications are used commonly in mechanically ventilated patients. Several classes of drugs with different properties and indications may be given by inhalation. In all cases, inhaled therapy's main advantage ove...Aerosol medications are used commonly in mechanically ventilated patients. Several classes of drugs with different properties and indications may be given by inhalation. In all cases, inhaled therapy's main advantage over the systemic route is that, for a given therapeutic response, the drug dose is several-fold lower, whereas systemic absorption is negligible. Because of this, the side effects are minimized greatly. Additionally, for some medications, the systemic route either causes nonacceptable side effects or results in considerably inferior therapeutic response, rendering the inhaled route the method of choice of drug administration. Bronchodilators, vasoactive drugs, surfactant, antibiotics, and helium are some agents that can be inhaled during mechanical ventilation.
Respir Care Clin N Am
· 2002 Jun · PMID 12481821
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Because of its low density, the He/O2 mixture markedly affects the dynamics of gas-flow, increasing inspiratory and expiratory flows, reducing WOB and respiratory acidosis, and relieving dyspnea in various clinical situa...Because of its low density, the He/O2 mixture markedly affects the dynamics of gas-flow, increasing inspiratory and expiratory flows, reducing WOB and respiratory acidosis, and relieving dyspnea in various clinical situations associated with obstructive airway disease. The magnitude of these changes varies according to the proportion of turbulent, transitional, and laminar flow conditions. These effects, however, last only as long as the patient breathes the He/O2 mixture, because it has no curative effect on the cause of airway obstruction. Thus, He/O2 ventilation is mostly useful while awaiting the effects of more definitive treatment. Evidence shows that He/O2 ventilation can improve pathophysiologic and clinical parameters in spontaneously breathing patients with upper airway obstruction, asthma. COPD, bronchopulmonary dysplasia. and bronchiolitis. Furthermore. He/O2 ventilation may prove to be a valuable adjunct in decompensated COPD patients, during both NIV and conventional mechanical ventilation. Despite promising results, however, there are two primary pitfalls to He/O2 ventilation. First, the consequences of the physical properties of the He/O2 mixture on various ventilator functions, the major differences between machines, and the correction factors to apply (if necessary) should be known. Second, in this age of cost control, particular attention should be paid to the cost-benefit ratio of He/O2 ventilation. Indeed, despite clinical evidence that the pathophysiologic principles on which He/O2 ventilation rests can be translated into favorable short-term physiologic and subjective effects, there is presently no evidence of a significant effect on patient outcome. Hence, before He/O2 ventilation can be recommended for widespread use, prospective outcome studies should be conducted in patients who suffer from the conditions discussed in this article to identify which, if any, are most likely to receive a benefit. Meanwhile, the authors recommend that He/O2 ventilation be reserved for patients who have a severe condition and who do not respond to the classic validated treatment modalities.
Respir Care Clin N Am
· 2002 Jun · PMID 12481820
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Maintaining optimal lung recruitment has a marked effect on the outcome of patients who suffer from ARDS. RMs superimposed on mechanical ventilation have the potential to recruit atelectatic lungs in the course of genera...Maintaining optimal lung recruitment has a marked effect on the outcome of patients who suffer from ARDS. RMs superimposed on mechanical ventilation have the potential to recruit atelectatic lungs in the course of general anesthesia; however, the physiologic benefits are less evident in ARDS patients who are ventilated at low VT values and high PEEP levels. Currently, the following technical aspects warrant further investigation: optimal time (the first hours after intubation or the first days of ARDS), duration (from 15 seconds to 2 minutes), mode (continuous positive end-expiratory pressure or pressure controlled ventilation with high PEEP), and type of patients (pulmonary versus extrapulmonary ARDS). Before the routine implementation of RMs to recruit the lungs fully in ARDS patients, clinicians also need more information on side effects and contraindications. Although RMs are transient, they may be associated with complications such as hypotension, bradycardia, and barotrauma. Moreover, further studies are needed to compare the efficacy of periodic high-pressure RMs that are superimposed on mechanical ventilation with ventilation using high PEEP levels and low VT values without RMs in patients who have early ARDS after initial hemodynamic stabilization.
Respir Care Clin N Am
· 2002 Jun · PMID 12481819
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Inhaled NO offers a novel therapy for the treatment of pulmonary hypertensive diseases and the symptomatic relief of hypoxemia. The use of iNO reduces the necessity for ECMO in newborns and infants with acute hypoxemic r...Inhaled NO offers a novel therapy for the treatment of pulmonary hypertensive diseases and the symptomatic relief of hypoxemia. The use of iNO reduces the necessity for ECMO in newborns and infants with acute hypoxemic respiratory failure. Proper indications, contraindications, dosing criteria, and implications of the toxic actions of NO must be delineated fully. Randomized clinical trials of patients with carefully defined, specific acute disease states that are characterized by pulmonary hypertension or hypoxemia have not been completed.
Respir Care Clin N Am
· 2002 Jun · PMID 12481818
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The term high-frequency ventilation is used to describe a heterogeneous group of ventilation modes that are characterized by high respiratory frequencies and low tidal volumes. The increasing understanding of the pathoge...The term high-frequency ventilation is used to describe a heterogeneous group of ventilation modes that are characterized by high respiratory frequencies and low tidal volumes. The increasing understanding of the pathogenesis of VILI, including concepts such as volutrauma and atelectrauma, has led to a renewed interest in the role of HFV in lung-protective ventilation strategies. Inherent to many modes of HFV are low tidal volumes and small pressure swings during the respiratory cycle, which allow for higher mean airway pressures than those safely achieved with CMV. This has the potential to reduce lung injury by limiting volutrauma, whereas maintaining bigger lung volumes at end-expiration may reduce atelectrauma. Of the various forms of HFV, HFO is the only mode with an active expiration phase. This characteristic, combined with superior gas conditioning, may make HFO a promising ventilatory strategy for adults. Although a significant amount of data exists in the literature to support the application of HFO in infants and children who have acute respiratory failure, clinical data on the use of HFO in adults is only now emerging. Early studies of applying HFO in ARDS patients have demonstrated its safety and benefit in terms of oxygenation. Additionally, limited data exist on the comparison between HFO and CMV in this patient population; however, encouraging preliminary results have been reported. The optimum strategy for the application of HFV, including the timing of HFV initiation, remains unclear.
Respir Care Clin N Am
· 2002 Jun · PMID 12481817
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Acute respiratory distress syndrome (ARDS) is a severe form of respiratory failure that is characterized by marked hypoxemia, bilateral infiltrates on chest radiograph, and no clinical evidence of left ventricular failur...Acute respiratory distress syndrome (ARDS) is a severe form of respiratory failure that is characterized by marked hypoxemia, bilateral infiltrates on chest radiograph, and no clinical evidence of left ventricular failure. Mechanical ventilation with positive end-expiratory pressure (PEEP) is a cornerstone therapy for ARDS patients. Because the fundamental aim of supportive treatment is to improve arterial oxygenation, several alternatives to mechanical ventilation with PEEP have been used. One of these alternative therapies is prone positioning, which has been used safely to improve oxygenation in many patients with ARDS. Despite encouraging results, however, the use of prone positioning is not widely accepted as an adjunct to therapy in hypoxemic patients because, aside from temporarily improving gas exchange, it does not seem to affect the outcome of these patients. This article reviews the rationale for using prone positioning in ARDS patients who require intubation and mechanical ventilation.
Respir Care Clin N Am
· 2002 Jun · PMID 12481816
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Alterations in pulmonary surfactant is an important contributing factor in the pathogenesis of ARDS. Surfactant deficiency affects the progression and prognosis of ARDS patients and increases the susceptibility of ARDS i...Alterations in pulmonary surfactant is an important contributing factor in the pathogenesis of ARDS. Surfactant deficiency affects the progression and prognosis of ARDS patients and increases the susceptibility of ARDS in patients who are at risk for it. Several studies have suggested that the use of exogenous surfactant preparations can improve lung function and overall outcome in ARDS patients; however, large randomized clinical trials have failed to show any benefit. Continued work on surfactant therapy-including efforts to improve the mode of delivery, to understand better the pathophysiology of exogenous surfactant, and to develop synthetic surfactants that emulate natural ones more closely-will help to elucidate its role in ARDS.
Respir Care Clin N Am
· 2002 Jun · PMID 12481815
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In laboratory models, PLV is clearly more effective than conventional ventilation alone; however, this advantage has not been observed in any human study. The reasons for this are unclear, but the approach to ventilation...In laboratory models, PLV is clearly more effective than conventional ventilation alone; however, this advantage has not been observed in any human study. The reasons for this are unclear, but the approach to ventilation during PLV may have been inappropriate. HFO may require further study or perhaps PLV should be combined with nitric oxide or some other vasoactive agent. Additionally, perfluorocarbons may need to be aerosolized instead of instilled. Kandler et al. recently demonstrated better gas exchange that was sustained for a longer period in lavage-injured piglets when a perfluorocarbon was aerosolized. This preliminary result demonstrates that there are other options for the delivery of perfluorocarbons in the management of critically ill patients. Based on the failure of the two trials in adult ARDS patients, however, a long time may pass before another human PLV trial is undertaken.
Respir Care Clin N Am
· 2002 Jun · PMID 12481814
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Tracheal gas insufflation (TGI) as an adjunct to mechanical ventilation delivers fresh gas into the central airways continuously or in a phasic fashion to improve the efficiency of alveolar ventilation or to minimize the...Tracheal gas insufflation (TGI) as an adjunct to mechanical ventilation delivers fresh gas into the central airways continuously or in a phasic fashion to improve the efficiency of alveolar ventilation or to minimize the ventilatory pressure requirements. Recently, TGI has received increasing attention as an adjunctive tool for lung-protective mechanical-ventilation strategies. Experimental studies in animal and mechanical-lung models have been essential in the quest to understand TGI's mechanisms of action and operational characteristics. Experimental studies in animal models of lung injury have substantiated the potential role of TGI in clinical practice. Currently, the evolution of TGI is entering a phase in which overcoming obstacles to clinical implementation may lead to the development of commercial systems with more widespread TGI application.
Respir Care Clin N Am
· 2002 Jun · PMID 12481813
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There has been increasing recognition that mechanical ventilation can cause acute parenchymal lung injury (ventilator-induced lung injury, or VILI) in addition to the more widely recognized forms of barotrauma. Furthermo...There has been increasing recognition that mechanical ventilation can cause acute parenchymal lung injury (ventilator-induced lung injury, or VILI) in addition to the more widely recognized forms of barotrauma. Furthermore, in patients with acute lung injury, this type of injury may cause considerable morbidity and mortality. Subsequently, the goals of mechanical ventilation have been altered to avoid this outcome. In patients with relatively normal lungs who are receiving mechanical ventilation because of neuromuscular dysfunction or impaired conscious level or for short-term postoperative support, maintaining normal blood-gas tensions without risk of VILI is usually easy. In patients with acute asthma, chronic obstructive pulmonary disease, or acute lung injury, however, accepting abnormal blood-gas tensions, particularly an elevated PaCO2 (permissive hypercapnia), to improve survival and reduce complications is frequently necessary. Extensive experience has shown that ventilated patients usually tolerate moderate hypercapnia and frequently some degree of hypoxemia in the absence of shock, anemia, severe cardiac disease, or other contraindications.
Respir Care Clin N Am
· 2002 Mar · PMID 12184659
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Children deserve quality care when they are critically ill or injured. Specialized pediatric services may be limited outside major medical centers. Transport by specialized pediatric and neonatal transport teams may be r...Children deserve quality care when they are critically ill or injured. Specialized pediatric services may be limited outside major medical centers. Transport by specialized pediatric and neonatal transport teams may be required to deliver patients to tertiary pediatric medical centers. In addition, in the past decade a cost-effective, organized, systematic approach to health care management has assumed greater importance, leading to the concept of the so-called medical home. In this model, a child with a complex medical problem is cared for in the environment in which he or she will receive the best care, with emphasis on providing rehabilitative and long-term care near the child's home. It is likely, then, that the field of pediatric transport medicine will assume greater importance in the coming decade.
Respir Care Clin N Am
· 2002 Mar · PMID 12184658
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Although the primary focus of this article is on interhospital transport, some of the same basic transport principles and management techniques apply to intrahospital transport. The level of care provided during interhos...Although the primary focus of this article is on interhospital transport, some of the same basic transport principles and management techniques apply to intrahospital transport. The level of care provided during interhospital and intrahospital transport should be based on the neonate's diagnosis, clinical status, anticipated problems, and local, state, and national standards and regulations. The transport team should have policies and procedures to direct their practice. Documentation of the transport process should be initiated with the referral call and continued until the completion of transport. Planning and anticipation of problems are essential, as is care of the family. The transport team should evaluate each neonate's individual response to the transport.
Respir Care Clin N Am
· 2002 Mar · PMID 12184657
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Mechanical ventilation during long-range aeromedical transport presents significant challenges. Patient, crew member, and equipment are placed in an environment with reduced barometric pressure, noise, vibration, and lim...Mechanical ventilation during long-range aeromedical transport presents significant challenges. Patient, crew member, and equipment are placed in an environment with reduced barometric pressure, noise, vibration, and limited space, oxygen, electrical power, and access to imaging technology. It is the transport team's responsibility to provide care in this environment, which approximates that given in the ICU as closely as possible. This is achieved through careful preparation and planning. Preparation starts with training of the personnel and selection of optimal equipment. Planning needs to consider the patient's physiologic reserve, available supplies of oxygen and electrical power, and the crew's ability to sustain high performance for the duration of the mission.
Reynolds HN, Habashi NM, Cottingham CA
… +2 more, Frawley PM, McCunn M
Respir Care Clin N Am
· 2002 Mar · PMID 12184656
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Interhospital transport of the adult mechanically ventilated patient may be necessary for those who require specialized care. An experienced medical team can safely transport even the most critically ill patients if the...Interhospital transport of the adult mechanically ventilated patient may be necessary for those who require specialized care. An experienced medical team can safely transport even the most critically ill patients if the care is optimized before departure. Patients with severe respiratory failure may have to remain on an ICU ventilator throughout the transport period, depending on the specific transport ventilator. Near-terminal ARDS can be treated with ECLS, and these patients also may be safely transported to a regional center.
Respir Care Clin N Am
· 2002 Mar · PMID 12184655
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Today there are a number of automatic resuscitators and simple and complex transport ventilators on the market. The user must consider the purpose of the device, the patient population to be ventilated and the capabiliti...Today there are a number of automatic resuscitators and simple and complex transport ventilators on the market. The user must consider the purpose of the device, the patient population to be ventilated and the capabilities of the individual devices before purchasing a transport ventilator.
Respir Care Clin N Am
· 2002 Mar · PMID 12184654
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The transport of critically ill patients is hazardous, yet necessary. In these conditions monitoring may be challenging, and the ability to intervene when problems arise is often limited. Conducting safe transport of the...The transport of critically ill patients is hazardous, yet necessary. In these conditions monitoring may be challenging, and the ability to intervene when problems arise is often limited. Conducting safe transport of these patients has been shown to be possible when experienced personnel apply their knowledge appropriately. It is a complex exercise, however, with significant potential for breakdown. Despite the magnitude of such transports of high-risk patients, no substantive focus on formal training exists. This article proposes that formal training of transport teams be strongly considered at the institutional level, and it introduces the content and method of delivery of this training. Because these are expressed opinions, the concept should be explored and validated by an interventional study, establishing a baseline of transport complications in a given facility, implementing some form of training, and reevaluating the performance of the trained providers in the same institution. A significant reduction in complications would validate the time, effort, and expense of developing such a course and would provide a model for other institutions to follow.
Respir Care Clin N Am
· 2002 Mar · PMID 12184653
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As the diagnosis and treatment of critically ill patients continues to advance, the frequency of intrahospital transport of ventilator-dependent patients increases. Once the risks and benefits of transport are establishe...As the diagnosis and treatment of critically ill patients continues to advance, the frequency of intrahospital transport of ventilator-dependent patients increases. Once the risks and benefits of transport are established, even the sickest ICU patient can be transported safely when adequate time is taken and preparations are made before beginning the transport. Patients should be stabilized as much as possible and monitored before, during, and after transport. Those responsible for the patient should be trained to provide a safe outcome. This necessitates that caregivers receive education in patient evaluation, potential risks, complications, interventions, equipment operation, and troubleshooting that may be necessary when caring for ventilated patients outside the ICU. All members of the transport team should communicate effectively and be aware of their roles in the transport process to minimize delays and mishaps during transport and at the final destination. Written policies that define the level of personnel, level of training, level of support, and equipment necessary can facilitate the transport process. When choosing a device to provide ventilation, the patient's clinical condition should be determine which method is used for transport.