Showing papers in "Respiratory Care in 2005"

Dry powder inhaler formulation.

Abstract: A drug product combines pharmacologic activity with pharmaceutical properties. Desirable performance characteristics are physical and chemical stability, ease of processing, accurate and reproducible delivery to the target organ, and availability at the site of action. For the dry powder inhaler (DPI), these goals can be met with a suitable powder formulation, an efficient metering system, and a carefully selected device. This review focuses on the DPI formulation and development process. Most DPI formulations consist of micronized drug blended with larger carrier particles, which enhance flow, reduce aggregation, and aid in dispersion. A combination of intrinsic physicochemical properties, particle size, shape, surface area, and morphology affects the forces of interaction and aerodynamic properties, which in turn determine fluidization, dispersion, delivery to the lungs, and deposition in the peripheral airways. When a DPI is actuated, the formulation is fluidized and enters the patient's airways. Under the influence of inspiratory airflow, the drug particles separate from the carrier particles and are carried deep into the lungs, while the larger carrier particles impact on the oropharyngeal surfaces and are cleared. If the cohesive forces acting on the powder are too strong, the shear of the airflow may not be sufficient to separate the drug from the carrier particles, which results in low deposition efficiency. Advances in understanding of aerosol and solid state physics and interfacial chemistry are moving formulation development from an empirical activity to a fundamental scientific foundation.

The pathogenesis of ventilator-associated pneumonia: its relevance to developing effective strategies for prevention.

Abstract: Ventilator-associated pneumonia (VAP) is the most common nosocomial infection in the intensive care unit and is associated with major morbidity and attributable mortality. Strategies to prevent VAP are likely to be successful only if based upon a sound understanding of pathogenesis and epidemiology. The major route for acquiring endemic VAP is oropharyngeal colonization by the endogenous flora or by pathogens acquired exogenously from the intensive care unit environment, especially the hands or apparel of health-care workers, contaminated respiratory equipment, hospital water, or air. The stomach represents a potential site of secondary colonization and reservoir of nosocomial Gram-negative bacilli. Endotracheal-tube biofilm formation may play a contributory role in sustaining tracheal colonization and also have an important role in late-onset VAP caused by resistant organisms. Aspiration of microbe-laden oropharyngeal, gastric, or tracheal secretions around the cuffed endotracheal tube into the normally sterile lower respiratory tract results in most cases of endemic VAP. In contrast, epidemic VAP is most often caused by contamination of respiratory therapy equipment, bronchoscopes, medical aerosols, water (eg, Legionella) or air (eg, Aspergillus or the severe acute respiratory syndrome virus). Strategies to eradicate oropharyngeal and/or intestinal microbial colonization, such as with chlorhexidine oral care, prophylactic aerosolization of antimicrobials, selective aerodigestive mucosal antimicrobial decontamination, or the use of sucralfate rather than H(2) antagonists for stress ulcer prophylaxis, and measures to prevent aspiration, such as semirecumbent positioning or continuous subglottic suctioning, have all been shown to reduce the risk of VAP. Measures to prevent epidemic VAP include rigorous disinfection of respiratory equipment and bronchoscopes, and infection-control measures to prevent contamination of medical aerosols. Hospital water should be Legionella-free, and high-risk patients, especially those with prolonged granulocytopenia or organ transplants, should be cared for in hospital units with high-efficiency-particulate-arrestor (HEPA) filtered air. Routine surveillance of VAP, to track endemic VAPs and facilitate early detection of outbreaks, is mandatory.

Problems with inhaler use: a call for improved clinician and patient education.

Abstract: Patient education is a critical factor in the use and misuse of medication inhalers. Inhalers represent advanced technology that is considered so easy to use that many patients and clinicians do not receive adequate training in their use. Between 28% and 68% of patients do not use metered-dose inhalers or powder inhalers well enough to benefit from the prescribed medication, and 39-67% of nurses, doctors, and respiratory therapists are unable to adequately describe or perform critical steps for using inhalers. Of an estimated 25 billion dollars spent for inhalers annually, 5-7 billion dollars is wasted because of inhaler misuse. Reimbursement and teaching strategies to improve patient education could substantially reduce these wasted resources. Problems with inhaler use, the cost of inhalers, and myths associated with inhalers are reviewed, with recommendations for strategies and techniques to better educate patients in inhaler use.

Principles of metered-dose inhaler design

Abstract: The pressurized metered-dose inhaler (pMDI) was introduced to deliver asthma medications in a convenient and reliable multi-dose presentation. The key components of the pMDI device (propellants, formulation, metering valve, and actuator) all play roles in the formation of the spray, and in determining drug delivery to the lungs. Hence the opportunity exists to design a pMDI product by adjusting the formulation, metering-valve size, and actuator nozzle diameter in order to obtain the required spray characteristics and fine-particle dose. Breath-actuated pMDIs, breath-coordinated pMDIs, spray-velocity modifiers, and spacer devices may be useful for patients who cannot use a conventional press-and-breathe pMDI correctly. Modern pMDI devices, which contain non-ozone-depleting propellants, should allow inhalation therapy via pMDI to extend well into the 21st century for a variety of treatment indications.

The inhalation of drugs: Advantages and problems

Abstract: Inhalation is a very old method of drug delivery, and in the 20th century it became a mainstay of respiratory care, known as aerosol therapy. Use of inhaled epinephrine for relief of asthma was reported as early as 1929, in England. An early version of a dry powder inhaler (DPI) was the Aerohalor, used to administer penicillin dust to treat respiratory infections. In the 1950s, the Wright nebulizer was the precursor of the modern hand-held jet-venturi nebulizer. In 1956, the first metered-dose inhaler (MDI) was approved for clinical use, followed by the SpinHaler DPI for cromolyn sodium in 1971. The scientific basis for aerosol therapy developed relatively late, following the 1974 Sugarloaf Conference on the scientific basis of respiratory therapy. Early data on the drug-delivery efficiency of the common aerosol delivery devices (MDI, DPI, and nebulizer) showed lung deposition of approximately 10-15% of the total, nominal dose. Despite problems with low lung deposition with all of the early devices, evidence accumulated that supported the advantages of the inhalation route over other drug-administration routes. Inhaled drugs are localized to the target organ, which generally allows for a lower dose than is necessary with systemic delivery (oral or injection), and thus fewer and less severe adverse effects. The 3 types of aerosol device (MDI, DPI, and nebulizer) can be clinically equivalent. It may be necessary to increase the number of MDI puffs to achieve results equivalent to the larger nominal dose from a nebulizer. Design and lung-deposition improvement of MDIs, DPIs, and nebulizers are exemplified by the new hydrofluoroalkane-propelled MDI formulation of beclomethasone, the metered-dose liquid-spray Respimat, and the DPI system of the Spiros. Differences among aerosol delivery devices create challenges to patient use and caregiver instruction. Potential improvements in aerosol delivery include better standardization of function and patient use, greater reliability, and reduction of drug loss.

The microbiology of ventilator-associated pneumonia.

Abstract: Ventilator-associated pneumonia (VAP) is a common complication of ventilatory support for patients with acute respiratory failure and is associated with increased morbidity, mortality, and costs. Awareness of the microbiology of VAP is essential for selecting optimal antibiotic therapy and improving these outcomes. The specific microbial causes of VAP are many and varied. Most cases of VAP are caused by bacterial pathogens that normally colonize the oropharynx and gut, or that are acquired via transmission by health-care workers from environmental surfaces or from other patients. Common pathogens include Pseudomonas species and other highly resistant Gram-negative bacilli, staphylococci, the Enterobacteriaceae, streptococci, and Haemophilus species. Antibiotic-resistant pathogens such as Pseudomonas and Acinetobacter species and methicillin-resistant strains of Staphylococcus aureus are much more common after prior antibiotic treatment or prolonged hospitalization or mechanical ventiation, and when other risk factors are present. The bacterial pathogens responsible for VAP also vary depending on patient characteristics and in certain clinical circumstances, such as in acute respiratory distress syndrome or following tracheostomy, traumatic injuries, or burns. But these differences appear to be due primarily to the duration of mechanical ventilation and/or degree of prior antibiotic exposure of these patients. The causes of VAP can vary considerably by geographic location (even between units in the same hospital), emphasizing the importance of local epidemiological and microbiological data. Atypical bacteria, viruses, and fungi also have been implicated as causes of VAP, but these pathogens have not been studied systematically and their role is presently unclear. In conclusion, information about the microbiology of VAP serves to guide optimal antibiotic therapy. The risk of antibiotic-resistant pathogens can be estimated using simple clinical features and awareness of local microbiology patterns. The roles of atypical bacterial and nonbacterial pathogens in VAP are incompletely understood and should be investigated further.

Dry powder inhalers: an overview.

Abstract: Dry powder inhalers (DPIs) are a widely accepted inhaled delivery dosage form, particularly in Europe, where they currently are used by a large number of patients for the delivery of medications to treat asthma and chronic obstructive pulmonary disease. The acceptance of DPIs in the United States after the slow uptake following the introduction of the Serevent Diskus in the late 1990s has been driven in large part by the enormous success in recent years of the Advair Diskus. This combination of 2 well-accepted drugs in a convenient and simple-to-use device has created an accepted standard in pulmonary delivery and disease treatment that only a few years ago could not have been anticipated. The DPI offers good patient convenience, particularly for combination therapies, and also better compliance. The design and development of any powder drug-delivery system is a highly complex task. Optimization of the choice of formulation when matched with device geometry is key. The use of particle engineering to create a formulation matched to a simple device is being explored, as is the development of active powder devices in which the device inputs the energy, making it simpler for patients to receive the correct dose. Patient interface issues are also critically important. However, one of the most important factors in pulmonary delivery from a DPI is the requirement for a good-quality aerosol, in terms of the aerosol's aerodynamic particle size, and its potential to consistently achieve the desired lung deposition in vivo.

Delivered Oxygen Concentrations Using Low-Flow and High-Flow Nasal Cannulas

Abstract: INTRODUCTION: Nasal cannulas are commonly used to deliver oxygen in acute and chronic care settings; however, there are few data available on delivered fraction of inspired oxygen (FIO2). The purposes of this study were to determine the delivered FIO2 on human subjects using low-flow and high-flow nasal cannulas, and to determine the effects of mouth-closed and mouth-open breathing on FIO2. METHODS: We measured the pharyngeal FIO2 delivered by adult nasal cannulas at 1–6 L/min and high-flow nasal cannulas at 6–15 L/min consecutively in 10 normal subjects. Oxygen was initiated at 1 L/min, with the subject at rest, followed by a period of rapid breathing. Gas samples were aspirated from a nasal catheter positioned with the tip behind the uvula. This process was repeated at each liter flow. Mean, standard deviation, and range were calculated at each liter flow. FIO2 during mouth-open and mouth-closed breathing were compared using the dependent t test for paired values, to determine if there were significant differences. RESULTS: The mean resting FIO2 ranged from 0.26–0.54 at 1–6 L/min to 0.54–0.75 at 6–15 L/min. During rapid breathing the mean FIO2 ranged from 0.24–0.45 at 1–6 L/min to 0.49–0.72 at 6–15 L/min. The mean FIO2 increased with increasing flow rates. The standard deviation (±0.04–0.15) and range were large, and FIO2 varied widely within and between subjects. FIO2 during mouth-open breathing was significantly (p CONCLUSIONS: FIO2 increased with increasing flow. Subjects who breathed with their mouths open attained a significantly higher FIO2, compared to those who breathed with their mouths closed.

The expanding role of aerosols in systemic drug delivery, gene therapy, and vaccination.

Abstract: Aerosolized medications have been used for centuries to treat respiratory diseases. Until recently, inhalation therapy focused primarily on the treatment of asthma and chronic obstructive pulmonary disease, and the pressurized metered-dose inhaler was the delivery device of choice. However, the role of aerosol therapy is clearly expanding beyond that initial focus. This expansion has been driven by the Montreal protocol and the need to eliminate chlorofluorocarbons (CFCs) from traditional metered-dose inhalers, by the need for delivery devices and formulations that can efficiently and reproducibly target the systemic circulation for the delivery of proteins and peptides, and by developments in medicine that have made it possible to consider curing lung diseases with aerosolized gene therapy and preventing epidemics of influenza and measles with aerosolized vaccines. Each of these drivers has contributed to a decade or more of unprecedented research and innovation that has altered how we think about aerosol delivery and has expanded the role of aerosol therapy into the fields of systemic drug delivery, gene therapy, and vaccination. During this decade of innovation, we have witnessed the coming of age of dry powder inhalers, the development of new soft mist inhalers, and improved pressurized metered-dose inhaler delivery as a result of the replacement of CFC propellants with hydrofluoroalkane. The continued expansion of the role of aerosol therapy will probably depend on demonstration of the safety of this route of administration for drugs that have their targets outside the lung and are administered long term (eg, insulin aerosol), on the development of new drugs and drug carriers that can efficiently target hard-to-reach cell populations within the lungs of patients with disease (eg, patients with cystic fibrosis or lung cancer), and on the development of devices that improve aerosol delivery to infants, so that early intervention in disease processes with aerosol therapy has a high probability of success.

Comparing clinical features of the nebulizer, metered-dose inhaler, and dry powder inhaler.

Abstract: Topically inhaled bronchodilators and corticosteroids are the mainstay of treatment for asthma and chronic obstructive pulmonary disease. These medications are delivered via jet or ultrasonic nebulizer, metered-dose inhaler (MDI), or dry powder inhaler (DPI). While the number of devices may be confusing to patients and clinicians, each device has distinct advantages and disadvantages. Most clinical evidence shows that any of these devices will work for most situations, including exacerbations and in the stable outpatient setting. There is a high rate of errors in device use with all these devices, especially the MDI. In choosing a drug/device combination for a patient, the clinician must take into account several factors, including the cognitive and physical ability of the patient, ease of use, convenience, costs, and patient preferences. Clinicians should also have a rudimentary understanding of aerosol principles in order to be able to teach appropriate use of aerosol devices to their patients.

Pressure-volume curves of the respiratory system.

Abstract: The quasi-static pressure-volume (P-V) curve of the respiratory system describes the mechanical behavior of the lungs and chest wall during inflation and deflation. To eliminate resistive and convective acceleration effects, the measurement of volume and pressure must be performed during short periods of apnea or during very slow flow. There are 3 main techniques for acquiring quasi-static P-V curves: the supersyringe method, the constant flow method, and the multiple-occlusion (or ventilator) method. For the information to be interpreted correctly, one must understand the interaction between the lungs and the chest wall, the effects of the supine position, and the meaning of hysteresis. The P-V curve has been studied in many disease states, but it has been applied most extensively to patients with acute respiratory distress syndrome, in hopes that it might allow clinicians to customize ventilator settings according to a patient's individual respiratory mechanics and thus protect the patient from ventilator-induced lung injury. However, lack of standardization of the procedure used to acquire P-V curves, difficulties in measuring absolute lung volume, lack of knowledge regarding how to use the information, and a paucity of data showing a benefit in morbidity and mortality with the use of P-V curves have tempered early enthusiasm regarding the clinical usefulness of the quasi-static P-V curve.

Measurement of air trapping, intrinsic positive end-expiratory pressure, and dynamic hyperinflation in mechanically ventilated patients.

Abstract: Severe airflow obstruction is a common cause of acute respiratory failure. Dynamic hyperinflation affects tidal ventilation, increases airways resistance, and causes intrinsic positive end-expiratory pressure (auto-PEEP). Most patients with asthma and chronic obstructive pulmonary disease have dynamic hyperinflation and auto-PEEP during mechanical ventilation, which can cause hemodynamic compromise and barotrauma. Auto-PEEP can be identified in passively breathing patients by observation of real-time ventilator flow and pressure graphics. In spontaneously breathing patients, auto-PEEP is measured by simultaneous recordings of esophageal and flow waveforms. The ventilatory pattern should be directed toward minimizing dynamic hyperinflation and auto-PEEP by using small tidal volume and preserving expiratory time. With a spontaneously breathing patient, to reduce the work of breathing and improve patient-ventilator interaction, it is crucial to set an adequate inspiratory flow, inspiratory time, trigger sensitivity, and ventilator-applied PEEP. Ventilator graphics are invaluable for monitoring and treatment decisions at the bedside.

Ventilator-induced lung injury: from barotrauma to biotrauma.

Abstract: I am very honored to have been asked to give the Egan Lecture, especially as you are celebrating your golden anniversary Congress—50 years of international respiratory care. Donald Egan was a remarkable man. Through his vision, his hard work, and his textbook, he impacted respiratory care in a major way throughout his life, and posthumously. In preparation for this talk, I looked over the previous Egan lecturers and was very impressed with the individuals who have given this lecture in the past, and I was very humbled. In these talks, you’ve heard about everything from the alveolus to hyperoxia to the top of Mt Everest. What I’m going to talk to you about today is ventilator-induced lung injury: from barotrauma to biotrauma. I chose this topic for a number of reasons:

What is ventilator-associated pneumonia and why is it important?

Abstract: Hospital-associated pneumonia (HAP) is one of the most common infections acquired among hospitalized patients. HAP is associated with excess mortality and increased medical care costs. The rise in HAP due to antibiotic-resistant bacteria has resulted in more common administration of inappropriate antimicrobial treatment, with an associated increased risk of hospital mortality. Ventilator-associated pneumonia (VAP) refers to HAP occurring in patients requiring mechanical ventilation. VAP is the most common nosocomial infection among patients with acute respiratory failure. Physicians treating patients with HAP and VAP should be aware of the predominant local pathogens associated with these infections and their antimicrobial susceptibility patterns. This will allow more appropriate initial antibiotic selection in order to optimize treatment regimens and clinical outcomes. Additionally, clinical strategies aimed at the prevention of HAP and VAP should be employed in all hospital settings caring for patients at risk for these infections.

Using Ventilator Graphics to Identify Patient-Ventilator Asynchrony

Abstract: Patient-ventilator interaction can be described as the relationship between 2 respiratory pumps: (1) the patient's pulmonary system, which is controlled by the neuromuscular system and influenced by the mechanical characteristics of the lungs and thorax, and (2) the ventilator, which is controlled by the ventilator settings and the function of the flow valve. When the 2 pumps function in synchrony, every phase of the breath is perfectly matched. Anything that upsets the harmony between the 2 pumps results in asynchrony and causes patient discomfort and unnecessarily increases work of breathing. This article discusses asynchrony relative to the 4 phases of a breath and illustrates how asynchrony can be identified with the 3 standard ventilator waveforms: pressure, flow, and volume. The 4 phases of a breath are: (1) The trigger mechanism (ie, initiation of the inspiration), which is influenced by the trigger-sensitivity setting, patient effort, and valve responsiveness. (2) The inspiratory-flow phase. During both volume-controlled and pressure-controlled ventilation the patient's flow demand should be carefully evaluated, using the pressure and flow waveforms. (3) Breath termination (ie, the end of the inspiration). Ideally, the ventilator terminates inspiratory flow in synchrony with the patient's neural timing, but frequently the ventilator terminates inspiration either early or late, relative to the patient's neural timing. During volume-controlled ventilation we can adjust variables that affect inspiratory time (eg, peak flow, tidal volume). During pressure-controlled or pressure-support ventilation we can adjust variables that affect when the inspiration terminates (eg, inspiratory time, expiratory sensitivity). (4) Expiratory phase. Patients with obstructive lung disease are particularly prone to developing intrinsic positive end-expiratory pressure (auto-PEEP) and therefore have difficulty triggering the ventilator. Bedside evaluation for the presence of auto-PEEP should be routinely performed and corrective adjustments made when appropriate.

Esophageal and Gastric Pressure Measurements

Abstract: The measurement of esophageal and gastric pressures with balloon-tipped catheters has been used with great success over the past half century to delineate the physiology of the mechanical respiratory system. Pleural pressure and abdominal pressure values estimated from esophageal and gastric pressure measurements allow analysis of lung and chest wall compliance, as well as work of breathing, respiratory muscle function, and the presence of diaphragm paralysis. Although much of the use of these measurement techniques has been in the clinical laboratory, to improve the understanding of basic physiologic mechanisms, the techniques have also been used in clinical situations to diagnose diaphragm paralysis, assess the work of breathing during mechanical ventilation, and estimate pulmonary compliance. In this article I review the historical background, physiology, placement techniques, and potential clinical applications of esophageal and gastric pressure measurements. In addition, I will briefly review the measurement of bladder pressure, which is a related topic.

Counseling about turbuhaler technique: needs assessment and effective strategies for community pharmacists.

Abstract: Optimal effects of asthma medications are dependent on correct inhaler technique. In a telephone survey, 77/87 patients reported that their Turbuhaler technique had not been checked by a health care professional. In a subsequent pilot study, 26 patients were randomized to receive one of 3 Turbuhaler counseling techniques, administered in the community pharmacy. Turbuhaler technique was scored before and 2 weeks after counseling (optimal technique = score 9/9). At baseline, 0/26 patients had optimal technique. After 2 weeks, optimal technique was achieved by 0/7 patients receiving standard verbal counseling (A), 2/8 receiving verbal counseling augmented with emphasis on Turbuhaler position during priming (B), and 7/9 receiving augmented verbal counseling plus physical demonstration (C) (Fisher's exact test for A vs C, p = 0.006). Satisfactory technique (4 essential steps correct) also improved (A: 3/8 to 4/7; B: 2/9 to 5/8; and C: 1/9 to 9/9 patients) (A vs C, p = 0.1). Counseling in Turbuhaler use represents an important opportunity for community pharmacists to improve asthma management, but physical demonstration appears to be an important component to effective Turbuhaler training for educating patients toward optimal Turbuhaler technique.

Determinants of patient adherence to an aerosol regimen.

Abstract: Patient adherence with prescribed inhaled therapy is related to morbidity and mortality. The terms "compliance" and "adherence" are used in the literature to describe agreement between prescribed medication and patient practice, with "adherence" implying active patient participation. Patient adherence with inhaled medication can be perfect, good, adequate, poor, or nonexistent, although criteria for such levels are not standardized and may vary from one study to another. Generally, nonadherence can be classified into unintentional (not understood) or intentional (understood but not followed). Failing to understand correct use of an inhaler exemplifies unintentional nonadherence, while refusing to take medication for fear of adverse effects constitutes intentional nonadherence. There are various measures of adherence, including biochemical monitoring of subjects, electronic or mechanical device monitors, direct observation of patients, medical/pharmacy records, counting remaining doses, clinician judgment, and patient self-report or diaries. The methods cited are in order of more to less objective, although even electronic monitoring can be prone to patient deception. Adherence is notoriously higher when determined by patient self-report, compared to electronic monitors. A general lack of adherence with inhaled medications has been documented in studies, and adherence declines over time, even with return clinic visits. Lack of correct aerosol-device use is a particular type of nonadherence, and clinician knowledge of correct use has been shown to be imperfect. Other factors related to patient adherence include the complexity of the inhalation regimen (dosing frequency, number of drugs), route of administration (oral vs inhaled), type of inhaled agent (corticosteroid adherence is worse than with short-acting beta2 agonists), patient awareness of monitoring, as well as a variety of patient beliefs and sociocultural and psychological factors. Good communication skills among clinicians and patient education about inhaled medications are central to improving adherence.

Early complications of tracheostomy.

Abstract: Complications from surgical procedures are common and must be taken into account when assessing the risks and benefits of a particular treatment approach. Common acute risks of tracheostomy include bleeding, airway loss, damage to adjacent structures, and failure of the chosen technique to achieve successful airway placement. The frequency and severity of these occurrences depends on several factors. These include the specific approach to tracheostomy, the skill and experience of the operator, and patient anatomic and physiologic factors. The incidence of undesired outcomes during tracheostomy cannot be exactly predicted because of the interaction of the above issues. This paper will consider some of the common and less common acute complications of several of the usual techniques for temporary tracheostomy placement in critically ill patient.

History of Aerosol Therapy: Liquid Nebulization to MDIs to DPIs

Abstract: Inhaled therapies have been used since ancient times and may have had their origins with the smoking of datura preparations in India 4,000 years ago. In the late 18th and in the 19th century, earthenware inhalers were popular for the inhalation of air drawn through infusions of plants and other ingredients. Atomizers and nebulizers were developed in the mid-1800s in France and were thought to be an outgrowth of the perfume industry as well as a response to the fashion of inhaling thermal waters at spas. Around the turn of the 20th century, combustible powders and cigarettes containing stramonium were popular for asthma and other lung complaints. Following the discovery of the utility of epinephrine for treating asthma, hand-bulb nebulizers were developed, as well as early compressor nebulizers. The marketing of the first pressurized metered-dose inhaler for epinephrine and isoproterenol, by Riker Laboratories in 1956, was a milestone in the development of inhaled drugs. There have been remarkable advances in the technology of devices and formulations for inhaled drugs in the past 50 years. These have been influenced greatly by scientific developments in several areas: theoretical modeling and indirect measures of lung deposition, particle sizing techniques and in vitro deposition studies, scintigraphic deposition studies, pharmacokinetics and pharmacodynamics, and the 1987 Montreal Protocol, which banned chlorofluorocarbon propellants. We are now in an era of rapid technologic progress in inhaled drug delivery and applications of aerosol science, with the use of the aerosolized route for drugs for systemic therapy and for gene replacement therapy, use of aerosolized antimicrobials and immunosuppressants, and interest in specific targeting of inhaled drugs.

Ventilator-associated pneumonia: issues related to the artificial airway.

Abstract: Pooling of contaminated secretions above the cuff of the endotracheal tube predisposes patients to ventilator-associated pneumonia (VAP). Subglottic secretion drainage requires a special endotracheal tube that has a separate lumen that opens in the subglottic region above the tracheal tube. A recent meta-analysis of the 5 randomized clinical trials that evaluated the efficacy of removing these secretions found that this technique significantly reduces the incidence of VAP. One cost-effectiveness analysis showed savings of $4,900 per episode of VAP prevented. Greatest benefit is derived by patients requiring fewer than 10 days of mechanical ventilation and not exposed to antibiotic therapy. Maintaining the intracuff pressure between 25 and 30 cm H2O is mandatory to guarantee effective drainage and safety. While silver-coated endotracheal tubes reduce pseudomonas pneumonia in intubated dogs and delay airway colonization in intubated patients, evaluation of studies with a variety of case mixes is warranted to identify subsets likely to benefit from the technique before it is implemented on a large scale. A patient who has a colonized airway and who undergoes percutaneous tracheotomy has an increased risk of VAP, particularly due to Pseudomonas aeruginosa, in the week following the procedure. As many studies suggest that incidence of VAP is highly dependent on the strategies of airway management, health care workers should be alerted to issues related to the artificial airway.

Optimizing Aerosol Delivery by Pressurized Metered-Dose Inhalers

Abstract: The modern era of aerosol therapy began with the introduction of the Medihaler Epi in 1956, after a 13-year-old asthmatic told her father, an officer in the Riker company, that asthma medications should be as convenient to use as hair spray and she complained that the bulb atomizer leaked in her school bag. Since then, advances in technology have made aerosol delivery much more efficient, so that it is now the most widely used mode of medication delivery for chronic airways diseases. Today the pressurized metered-dose inhaler (pMDI) is a metal canister containing a mixture of propellants, surfactants, preservatives, and drug. However, pMDIs are underused in the United States. One barrier to use is the misconception related to pMDI effectiveness relative to small-volume nebulizers, especially among pediatricians. This is despite the strongest evidence of pMDI superiority, from well-controlled pediatric studies. In this manuscript we discuss ways to optimize the use of medications given via pMDI and examine recent changes in pMDI technology that will make drug delivery more efficient and consistent.

Knowledge and Use of Office Spirometry for the Detection of Chronic Obstructive Pulmonary Disease by Primary Care Physicians

Abstract: BACKGROUND: The importance of office spirometry has been strongly advocated in the pulmonary community, but whether its importance is recognized and accepted by primary care physicians is less well established. METHODS: To assess primary care physicians9 knowledge and use of office spirometry for the detection of chronic obstructive pulmonary disease, we conducted a brief mail survey on the local practice of office spirometry, barriers to performing office spirometry, and general knowledge about spirometry. We also provided 60-min educational workshops to assess whether such an approach would increase spirometry testing or perceptions about spirometry. RESULTS: Twenty-nine of 57 (51%) primary care offices responded to the survey. Of these, 66% owned their own spirometer. The most common reasons for not performing spirometry were uncertainty about the impact of the test (41%), physician and staff unfamiliarity (38%), and lack of training (34%). Twenty-one respondents participated in the workshops. In the 3 months following the workshops, the number of spirometry tests increased by 59% (p = 0.004). After the workshops, the proportion of clinics that reported reasons for not performing the test decreased by 13% (p = 0.01), but important barriers to performing office spirometry were still present, including physician and staff unfamiliarity (22%), uncertain interpretation of results (22%), time (22%), and reimbursement (22%). CONCLUSIONS: The general knowledge and use of office spirometry in the primary care community is poor, but can be improved, at least in the short-term, by a simple educational workshop.

Noninvasive positive-pressure ventilation in Patients with milder chronic obstructive pulmonary disease exacerbations: A Randomized controlled trial

Abstract: OBJECTIVES: To determine the effect of the addition of noninvasive positive-pressure ventilation (NPPV) to standard medical therapy on length of hospital stay among patients presenting with mild exacerbations of chronic obstructive pulmonary disease (COPD) requiring hospitalization. DESIGN: Randomized controlled unblinded study with concealed allocation. SETTING: Respiratory ward of a single-center, academic, tertiary-care hospital. PARTICIPANTS: Patients with a prior history of COPD who presented with a recent onset of shortness of breath and a pH of > 7.30 were eligible for inclusion in the study. INTERVENTIONS: NPPV daily for 3 days for intervals of 8, 6, and 4 hours, respectively, plus standard therapy, versus standard therapy alone. MEASUREMENTS: Borg dyspnea index at baseline, 1 hour, and daily. Length of hospital stay, endotracheal intubation, hospital survival. RESULTS: We found that NPPV was generally poorly tolerated, with only 12 of 25 patients wearing it for the prescribed 3 days. With the exception of a decrease in dyspnea at 1 hour and 2 days, significant between-group differences were not seen for any measured variable. CONCLUSIONS: The effectiveness and cost-effectiveness of the addition of NPPV to standard therapy in milder COPD exacerbations remains unclear.

Effects of Expiratory Rib-Cage Compression on Oxygenation, Ventilation, and Airway-Secretion Removal in Patients Receiving Mechanical Ventilation

Abstract: BACKGROUND: Expiratory rib-cage compression, a chest physiotherapy technique, is well known as the “squeezing” technique in Japan. OBJECTIVE: To determine the effects of rib-cage compression on airway-secretion removal, oxygenation, and ventilation in patients receiving mechanical ventilation. SETTING: An intensive care unit of an emergency and critical care center at a tertiary-care teaching hospital in Tokyo, Japan. METHODS: Thirty-one intubated, mechanically ventilated patients in an intensive care unit were studied in a randomized, crossover trial. The patients received endotracheal suctioning with or without rib-cage compression, with a minimum 3-hour interval between the 2 interventions. Rib-cage compression was performed for 5 min before endotracheal suctioning. Arterial blood gas and respiratory mechanics were measured 5 min before endotracheal suctioning (baseline) and 25 min after suctioning. The 2 measurement periods were carried out on the same day. RESULTS: There were no significant differences in the ratio of arterial partial pressure of oxygen to fraction of inspired oxygen, PaCO2, or dynamic compliance of the respiratory system between the 2 periods (before and after endotracheal suctioning). Moreover, there were no significant differences in airway-secretion removal between the 2 periods. CONCLUSIONS: This study suggests that rib-cage compression prior to endotracheal suctioning does not improve airway-secretion removal, oxygenation, or ventilation after endotracheal suctioning in this unselected population of mechanically ventilated patients.

Tracheostomy tubes and related appliances.

Abstract: Tracheostomy tubes are used to administer positive-pressure ventilation, to provide a patent airway, to provide protection from aspiration, and to provide access to the lower respiratory tract for airway clearance. They are available in a variety of sizes and styles, from several manufacturers. The dimensions of tracheostomy tubes are given by their inner diameter, outer diameter, length, and curvature. Differences in length between tubes of the same inner diameter, but from different manufacturers, are not commonly appreciated but may have important clinical implications. Tracheostomy tubes can be angled or curved, a feature that can be used to improve the fit of the tube in the trachea. Extra proximal length tubes facilitate placement in patients with large necks, and extra distal length tubes facilitate placement in patients with tracheal anomalies. Several tube designs have a spiral wire reinforced flexible design and have an adjustable flange design to allow bedside adjustments to meet extra-length tracheostomy tube needs. Tracheostomy tubes can be cuffed or uncuffed. Cuffs on tracheostomy tubes include high-volume low-pressure cuffs, tight-to-shaft cuffs, and foam cuffs. The fenestrated tracheostomy tube has an opening in the posterior portion of the tube, above the cuff, which allows the patient to breathe through the upper airway when the inner cannula is removed. Tracheostomy tubes with an inner cannula are called dual-cannula tracheostomy tubes. Several tracheostomy tubes are designed specifically for use with the percutaneous tracheostomy procedure. Others are designed with a port above the cuff that allows for subglottic aspiration of secretions. The tracheostomy button is used for stoma maintenance. It is important for clinicians caring for patients with a tracheostomy tube to understand the nuances of various tracheostomy tube designs and to select a tube that appropriately fits the patient.

Indications for and timing of tracheostomy.

Abstract: Tracheostomy is one of the most common intensive care unit procedures performed. The advantages include patient comfort, safety, ability to communicate, and better oral and airway care. Patients may have shorter intensive care unit stays, days of mechanical ventilation, and hospital stays. There are risks, long-term and acute, and the timing of when to do a tracheostomy must be individualized. As soon as the need for prolonged airway access is identified, the tracheostomy should be considered. Generally, this decision can be made within 7-10 days. Bedside techniques allow rapid tracheostomy with low morbidity.

Reducing ventilation frequency during cardiopulmonary resuscitation in a porcine model of cardiac arrest.

Abstract: INTRODUCTION: American Heart Association/American College of Cardiology guidelines recommend a compression-to-ventilation ratio (C/V ratio) of 15:2 during cardiopulmonary resuscitation (CPR) for out-of-the-hospital cardiac arrest. Recent data have shown that frequent ventilations are unnecessary and may be harmful during CPR, since each positive-pressure ventilation increases intrathoracic pressure and may increase intracranial pressure and decrease venous blood return to the right heart and thereby decrease both the cerebral and coronary perfusion pressures. HYPOTHESIS: We hypothesized that reducing the ventilation rate by increasing the C/V ratio from 15:2 to 15:1 will increase vital-organ perfusion pressures without compromising oxygenation and acid-base balance. METHODS: Direct-current ventricular fibrillation was induced in 8 pigs. After 4 min of untreated ventricular fibrillation without ventilation, all animals received 4 min of standard CPR with a C/V ratio of 15:2. Animals were then randomized to either (A) a C/V ratio of 15:1 and then 15:2, or (B) a C/V ratio of 15:2 and then 15:1, for 3 min each. During CPR, ventilations were delivered with an automatic transport ventilator, with 100% oxygen. Right atrial pressure, intratracheal pressure (a surrogate for intrathoracic pressure), aortic pressure, and intracranial pressure were measured. Coronary perfusion pressure was calculated as diastolic aortic pressure minus right atrial pressure. Cerebral perfusion pressure was calculated as mean aortic pressure minus mean intracranial pressure. Arterial blood gas values were obtained at the end of each intervention. A paired t test was used for statistical analysis, and a p value RESULTS: The mean ± SEM values over 1 min with either 15:2 or 15:1 C/V ratios were as follows: intratracheal pressure 0.93 ± 0.3 mm Hg versus 0.3 ± 0.28 mm Hg, p = 0.006; coronary perfusion pressure 10.1 ± 4.5 mm Hg versus 19.3 ± 3.2 mm Hg, p = 0.007; intracranial pressure 25.4 ± 2.7 mm Hg versus 25.7 ± 2.7 mm Hg, p = NS; mean arterial pressure 33.1 ± 3.7 mm Hg versus 40.2 ± 3.6 mm Hg, p = 0.007; cerebral perfusion pressure 7.7 ± 6.2 mm Hg versus 14.5 ± 5.5 mm Hg, p = 0.008. Minute area intratracheal pressure was 55 ± 17 mm Hg · s versus 22.3 ± 10 mm Hg · s, p CONCLUSIONS: In a porcine model of ventricular fibrillation cardiac arrest, reducing the ventilation frequency during CPR by increasing the C/V ratio from 15:2 to 15:1 resulted in improved vital-organ perfusion pressures, higher end-tidal CO2 levels, and no change in arterial oxygen content or acid-base balance.

Respiratory Mechanics Derived From Signals in the Ventilator Circuit

Abstract: The aim of this article is to identify and interpret the data provided by modern ventilators that provide the greatest clinical help in evaluating respiratory mechanics during mechanical ventilation. In intensive care, respiratory mechanics can be assessed in dynamic conditions (no flow-interruption) or static conditions (occlusion techniques) to record compliance and resistance and to monitor pressure, flow, and volume. Real-time visualization of the pressure curve is crucial for monitoring during volume-controlled ventilation, in which pressure is the dependent variable. Analysis of the pressure curve has little clinical utility during pressure-controlled ventilation, in which the dependent variable is the flow waveform, which varies according to changes in the mechanics of the respiratory system. Pressure-volume loops and flow-volume loops provide useful information on the dynamic trends of the respiratory system compliance and resistance, respectively. Modern ventilators provide complete monitoring of respiratory system mechanics, which is our guideline for optimizing ventilatory support and avoiding complications associated with mechanical ventilation.

The endotracheal tube cuff-leak test as a predictor for postextubation stridor.

Abstract: BACKGROUND: The endotracheal tube (ETT) cuff-leak test (CLT) has been proposed as a relatively simple, noninvasive method for detecting the presence of laryngeal edema prior to tracheal extubation. OBJECTIVE: To determine the value of the CLT for predicting postextubation stridor (PES) among medical and surgical patients, and to assess the impact of certain variables on the incidence of PES. METHODS: We conducted a prospective, observational study in the intensive care unit at Washington Hospital Center, a 907-bed acute care hospital in Washington DC, with patients who were intubated for > 24 h. As part of respiratory therapy quality assurance, patients intubated for > 24 h are evaluated daily for extubation readiness, and CLT is conducted prior to extubation. The CLT results and the postextubation outcomes were prospectively recorded for 6 months. RESULTS: Of the 462 patients studied, 20 (4.3%) developed PES that required treatment; 7 of those 20 (1.5%) required reintubation. With patients who failed the CLT, defined by an absolute leak volume 45%, and patients intubated for > 6 d were more likely to develop PES. Key words: stridor, tracheal intubation, endotracheal tube cuff, airway obstruction, laryngeal edema, extubation failure. [Respir Care 2005;50(12):1632–1638. © 2005 Daedalus Enterprises]