Search

Patients with obstructive sleep apnea (OSA) may experience apneas and hypopneas primarily during stage R (REM) sleep when end-expiratory lung volume (EELV) reaches its nadir. The purpose of this study was to determine if REM-related reductions in EELV persist in the presence of continuous positive airway pressure (CPAP) prescribed during non-stage REM (NREM) sleep. We prospectively recruited 17 subjects referred to the sleep laboratory for CPAP titration. CPAP was titrated per AASM protocol to control respiratory events. The change in EELV was measured using magnetometry. Of the 17 subjects, 12 (71%) had moderate to severe OSA. Despite the application of CPAP, there was a significant reduction in EELV between NREM and REM sleep (− 105.9 ± 92.2 to − 325.0 ± 113.1 mL, respectively, p

The change in vital capacity from the seated to supine position (∆VC-supine) is used to screen for diaphragm dysfunction (DD), but some individuals are unable to tolerate the supine position. Since expiratory muscle function is often preserved in patients with isolated DD and inspiratory strength is reduced, the purpose of this study was to examine if the ratio of maximal expiratory pressure to maximal inspiratory pressure (MEP/MIP) may provide an alternative to ∆VC-supine when screening patients for DD. We performed a cross-sectional analysis on 76 patients referred for evaluation of unexplained dyspnea and possible DD. MEP and MIP were measured in the seated position as well as the percent change in VC from the seated to supine position (∆VC-supine %). The presence of unilateral diaphragm paralysis (UDP), bilateral diaphragm paralysis (BDP), or normal diaphragm function (N) was confirmed by ultrasound. Of the 76 patients, 23 had N, 40 had UDP, and 13 had BDP. MEP/MIP was significantly greater for UDP compared to N (2.1(1.2–5.7) and 1.5(0.7–2.2), respectively) (median and interquartile range) and for BDP compared to UDP (4.3(2.3–7.5) and 2.1(1.2–5.7), respectively) (p

Metabolic myopathies are a heterogeneous group of disorders characterized by inherited defects of enzymatic pathways involved in muscle cellular energetics and adenosine triphosphate synthesis. Skeletal and respiratory muscles are most affected. There are multiple mechanisms of disease. The age of onset and prognosis vary. Metabolic myopathies cause exercise intolerance, myalgia, and increase in muscle breakdown products during exercise. Some affect smooth muscle like the diaphragm and cause respiratory failure. The pathophysiology is complex and the evidence in literature to guide diagnosis and management is sparse. Treatment is limited. This review discusses the pathophysiology and diagnostic evaluation of these disorders.

Obstructive sleep apnea (OSA) is underdiagnosed in women compared with men. Women have a tendency to underreport or present with atypical symptoms such as behavior changes, insomnia, fatigue, and depression. Nocturia, waking up from sleep 2 times or more to void, has been shown to be associated with OSA, but it is not an included symptom in commonly used screening questionnaires in primary provider offices. About 50% of patients with OSA have nocturia, and treatment of OSA improves it. Recognition of nocturia as a relevant symptom of OSA is important for primary providers to provide timely referral for the diagnosis of OSA.

An incisional hernia is a common complication after abdominal surgery. Complaints of dyspnea in this population may be attributed to cardiopulmonary dysfunction or deconditioning. Large abdominal incisional hernias, however, may cause diaphragm dysfunction and result in dyspnea, which is more pronounced when standing (platypnea). The use of an abdominal binder may alleviate platypnea in this population. We discuss the link between diaphragm dysfunction and the lack of abdominal wall integrity and how abdominal wall support partially restores diaphragm function.

As lung volume decreases radial traction on the upper airway is reduced, making it more collapsible. The purpose of this study was to measure change in end-expiratory lung volume (EELV) following sleep onset and to evaluate the relationship between change in EELV and sleep-disordered breathing.Twenty subjects underwent overnight polysomnography, of whom 14 (70%) had obstructive sleep apnea (OSA). Change in EELV was measured throughout the night using magnetometry. Sleep was staged and respiratory events scored using American Academy of Sleep Medicine criteria. An additional 10 subjects had change in EELV measured simultaneously by magnetometer and spirometer while awake.In the subjects studied while awake, change in EELV calculated from magnetometer data correlated very strongly (Magnetometry provides a precise, unobtrusive, and continuous means to study lung volume changes during sleep. EELV declines from sleep onset, reaching its nadir during stage R sleep. The reduction in EELV in stage R sleep was associated with lower mean oxygen saturation but was not associated with greater sleep-disordered breathing.

"Optimal" mean airway pressure (MAP) during high-frequency oscillatory ventilation (HFOV) can be defined as the pressure that allows for maximal alveolar recruitment while minimizing alveolar overdistension. Choosing a MAP near or just below the point of maximal curvature (PMC) of the volume-pressure characteristics of the lung can serve as a guide to avoid overdistention during HFOV, while simultaneously preventing derecruitment. The purpose of this study was to assess whether optimal MAP at the PMC can be determined by using measures of PaO(2) in patients with acute respiratory distress syndrome (ARDS) undergoing HFOV.We prospectively studied seven patients with ARDS who underwent HFOV after failed conventional ventilation. In addition, 11 healthy subjects were studied to validate measurements of changes in end-expiratory lung volume (∆EELV) using magnetometers. Using this validated method, plots of ∆EELV and MAP were constructed during decremental changes in MAP following a recruitment maneuver in seven ventilated patients with ARDS. The PMC was defined as the point where the slope of the ∆EELV versus MAP curve acutely changed. The MAP at the PMC was compared to that determined from plots of PaO(2) versus MAP.In the healthy cohort, measurements of ∆EELV obtained by magnetometry approximated the line of identity when compared to those obtained by spirometry. The MAP determined using either the ∆EELV or PaO(2) techniques were identical in all seven HFOV ventilated patients. Additionally, there was a significant correlation between the MAP associated changes in PaO2 and the MAP associated changes in ∆EELV (p 0.001).The finding that MAP at the PMC is the same whether determined by measures of ∆EELV or PaO(2) suggest that bedside measures PaO(2) may provide an acceptable surrogate for measures of EELV when determining "optimal" MAP during HFOV.

Repeated antigen-driven proliferations cause CD28 on T cells to down-regulate. We hypothesized that alloantigen-induced proliferations could cause CD28 down-regulation in lung transplant recipients.To ascertain if CD28 down-regulation on CD4 T cells associated with manifestations of allograft dysfunction in lung transplant recipients.Peripheral blood CD4 T cells from 65 recipients were analyzed by flow cytometry, cytokine multiplex and proliferative assays, and correlated with clinical events.Findings that CD28 was present on less than 90% of total CD4 T cells were predominantly seen among the recipients with bronchiolitis obliterans syndrome (specificity = 88%). Perforin and granzyme B were produced by50% of the CD4(+)CD28(null) cells, but less than 6% of autologous CD4(+)CD28(+) cells (P0.006). CD4(+)CD28(null) cells also had increased productions of proinflammatory cytokines, but less frequently expressed regulatory T-cell marker FoxP3 (2.1 +/- 1.3%), compared with autologous CD4(+)CD28(+) (9.5 +/- 1.4; P = 0.01). Cyclosporine A (100 ng/ml) inhibited proliferation of CD4(+)CD28(null) cells by 33 +/- 11% versus 68 +/- 12% inhibition of CD4(+)CD28(+) (P = 0.025). FEV(1) fell 6 months later (0.35 +/- 0.04 L) in recipients with CD4(+)CD28(+)/CD4(total) less than 90% (CD28% Low) compared with 0.08 +/- 0.08 L among CD4(+)CD28(+)/CD4(total) (CD28% High) greater than 90% (CD28% High) recipients (P = 0.013). Two-year freedom from death or retransplantation in CD28% Low recipients was 32 +/- 10% versus 78 +/- 6% among the CD28% High subjects (P0.0001).CD28 down-regulation on CD4 cells is associated with bronchiolitis obliterans syndrome and poor outcomes in lung transplantation recipients. CD4(+)CD28(null) cells have unusual, potentially pathogenic characteristics, and could be important in the progression of allograft dysfunction. These findings may illuminate a novel paradigm of transplantation immunopathogenesis, and suggest that CD28 measurements could identify recipients at risk for clinical deteriorations.

The hemodynamic response to hypoxia may be influenced by exposure pattern and inducible biological signals, such as nitric oxide synthase (iNOS) expression. The systemic blood pressure (BP) and heart rate (HR) response to intermittent and continuous hypoxia (IH and CH) were examined as was the relationship between these responses and iNOS expression in 10 normal subjects. BP and HR were recorded during exposure to IH or CH (total hypoxic time=60 min/dayx3 days for each exposure profile), whereas arterial oxygen saturation (SpO2) was maintained at 80-90%. Total RNA was isolated from peripheral blood lymphocytes before exposure on Day 1 and 2 hours after the last exposure on Day 3, and it was assayed for iNOS messenger RNA (mRNA) expression using quantitative polymerase chain reaction (PCR). HR, systolic BP (SBP), and diastolic BP (DBP) increased during both experimental conditions (P

This chapter provides a concise review of the principles of ultrasound generation, propagation through tissue and image formation and emphasizes the clinical relevance of the basic physics upon which this imaging modality is based. A practical understanding of the topic is emphasized over discussion of theoretical issues. The most common ways of modulating the ultrasound beam to optimize image quality are presented, together with a description and illustrations of the common artifacts that are encountered in clinical practice.

Management of airway inflammation requires proper monitoring and treatment to improve long-term outcomes. However, achieving this goal is difficult, as current methods have limitations. Although nitric oxide (NO) was first identified 200 years ago, its physiological importance was not recognized until the early 1980s. Many studies have established the role of NO as an essential messenger molecule in body systems. In addition, studies have demonstrated a significant relationship between changes in exhaled NO levels and other markers of airway inflammation. The technique used to measure NO in exhaled breath is noninvasive, reproducible, sensitive, and easy to perform. Consequently, there is growing interest in the use of exhaled NO in the management of asthma and other pulmonary conditions. The purpose of this review is to promote a basic understanding of the physiologic actions of NO, measurement techniques, and ways that research findings might translate to future application in clinical practice. Specifically, the article will review the role of exhaled NO in regard to its historical background, mechanisms of action, measurement techniques, and implications for clinical practice and research.

IL-10 is an anti-inflammatory cytokine that suppresses NO synthase (NOS) and production of NO; its lack may promote NO production and alterations in cytokines modulated by NO with allergic airway inflammation (AI), such as IL-18 and IL-4. Therefore, we induced AI in IL-10 knockout (−/−) and IL-10-sufficient C57BL/6 (C57) mice with inhaled OVA and measured airway NO production, as exhaled NO (ENO) and bronchoalveolar lavage fluid nitrite levels. ENO and nitrite levels were elevated significantly in naive IL-10−/− mice as compared with C57 mice. With AI, ENO and nitrite levels increased in C57 mice and decreased in IL-10−/− mice. IL-18 production fell with both AI and addition of S-nitroso-N-acetyl-d,l-penicillamine (a NO donor) but was not significantly increased by chemical NOS inhibition by l-N5-(1-iminoethyl)-ornithine. IL-4 AI was increased significantly (up to 10-fold greater) in the absence of IL-10 but was reduced significantly with chemical inhibition of NOS. Airway responsiveness was lower in IL-10−/− mice and was associated with alteration in production of NO and IL-4. Thus, IL-4 production was increased, and likely decreased NO production, in a way not predicted by the absence of IL-10. Inhibition of IL-4 production, with inhibition of NOS in the absence of IL-10, demonstrated the importance of a NO and IL-4 feedback mechanism regulating this interaction.

Interleukin (IL)-10 is an anti-inflammatory cytokine implicated in the regulation of airway inflammation in asthma. Among other activities, IL-10 suppresses production of nitric oxide (NO); consequently, its absence may permit increased NO production, which can affect airway smooth muscle contractility. Therefore, we investigated airway reactivity (AR) in response to methacholine (MCh) in IL-10 knockout (−/−) mice compared with wild-type C57BL/6 (C57) mice, in which airway NO production was measured as exhaled NO (ENO), and NO production was altered with administration of either NO synthase (NOS)-specific inhibitors or recombinant murine (rm)IL-10. AR, measured as enhanced pause in vivo, and tracheal ring tension in vitro were lower in IL-10−/−mice by 25–50%, which was associated with elevated ENOlevels (13 vs. 7 ppb). Administration of NOS inhibitors NG-nitro-l-arginine methyl ester (8 mg/kg ip) or l- N6-(1-iminoethyl)-lysine (3 mg/kg ip) to IL-10−/−mice decreased ENOby an average of 50%, which was associated with increased AR, to levels similar to C57 mice. ENOin IL-10−/−mice decreased in a dose-dependent fashion in response to administered rmIL-10, to levels similar to C57 mice (7 ppb), which was associated with a 30% increment in AR. Thus increased NO production in the absence of IL-10, decreased AR, which was reversed with inhibition of NO, either by inhibition of NOS, or with reconstitution of IL-10. These findings suggest that airway NO production can modulate airway smooth muscle contractility, resulting in airway hyporesponsiveness when IL-10 is absent.

Carbon monoxide is produced endogenously in humans through the breakdown of hemoglobin by heme oxygenase. Although originally thought to be a superfluous by-product of heme catabolism, carbon monoxide is now known to play a central role in many aspects of human health and disease. The functions of carbon monoxide that have been described to date are myriad, including blood pressure regulation, maintenance of organ-specific vascular tone, neurotransmission, stress response, platelet activation, and smooth muscle relaxation. This review outlines what is known to date about carbon monoxide as it relates to human disease.

Introduction The purpose of this study was to evaluate if ultrasound derived measures of diaphragm thickening, rather than diaphragm motion, can be used to predict extubation success or failure. Methods Sixty-three mechanically ventilated patients were prospectively recruited. Diaphragm thickness (tdi) was measured in the zone of apposition of the diaphragm to the rib cage using a 7–10 MHz ultrasound transducer. The percent change in tdi between end-expiration and end-inspiration (Δtdi%) was calculated during either spontaneous breathing (SB) or pressure support (PS) weaning trials. A successful extubation was defined as SB for >48 h following endotracheal tube removal. Results Of the 63 subjects studied, 27 patients were weaned with SB and 36 were weaned with PS. The combined sensitivity and specificity of Δtdi%≥30% for extubation success was 88% and 71%, respectively. The positive predictive value and negative predictive value were 91% and 63%, respectively. The area under the receiver operating characteristic curve was 0.79 for Δtdi%. Conclusions Ultrasound measures of diaphragm thickening in the zone of apposition may be useful to predict extubation success or failure during SB or PS trials.

Smoking is overwhelmingly the major cause of chronic bronchitis and emphysema worldwide. Additional risk factors for developing COPD are presented, along with the variables that govern cigarette smoke deposition in the lung. Major paradigms for the pathogenesis of COPD, including the protease-antiprotease and oxidant-antioxidant theories are described, and evidence for impaired reparative mechanisms in the causation of emphysema is noted. A description of the natural history of declining lung function in smokers and in the susceptible subset of smokers that ultimately develop smoking-induced COPD is accompanied by a discussion of the effects of smoking cessation on preservation of lung health. The disordered ventilation and gas-exchange physiology in the cigarette smoke-damaged lung is explained on the basis of the observed morphological changes.

The acute respiratory distress syndrome (ARDS)/acute lung injury (ALI) was described 30 yr ago, yet making a definitive diagnosis remains difficult. The identification of biomarkers obtained from peripheral blood could provide additional noninvasive means for diagnosis. To identify gene expression profiles that may be used to classify patients with ALI, 13 patients with ALI + sepsis and 20 patients with sepsis alone were recruited from the Medical Intensive Care Unit of the University of Pittsburgh Medical Center, and microarrays were performed on peripheral blood samples. Several classification algorithms were used to develop a gene signature for ALI from gene expression profiles. This signature was validated in an independently obtained set of patients with ALI + sepsis ( n = 8) and sepsis alone ( n = 1). An eight-gene expression profile was found to be associated with ALI. Internal validation found that the gene signature was able to distinguish patients with ALI + sepsis from patients with sepsis alone with 100% accuracy, corresponding to a sensitivity of 100%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 100%. In the independently obtained external validation set, the gene signature was able to distinguish patients with ALI + sepsis from patients with sepsis alone with 88.9% accuracy. The use of classification models to develop a gene signature from gene expression profiles provides a novel and accurate approach for classifying patients with ALI.

BackgroundNitric oxide (NO) and carbon monoxide (CO) in exhaled breath are considered obtainable biomarkers of physiologic mechanisms. Therefore, obtaining their measures simply, non-invasively, and repeatedly, is of interest, and was the purpose of the current study.MethodsExpired NO (ENO) and CO (ECO) were measured non-invasively using a gas micro-analyzer on several strains of mice (C57Bl6, IL-10-/-, A/J, MKK3-/-, JNK1-/-, NOS-2-/-and NOS-3-/-) with and without allergic airway inflammation (AI) induced by ovalbumin systemic sensitization and aerosol challenge, compared using independent-sample t-tests between groups, and repeated measures analysis of variance (ANOVA) within groups over time of inflammation induction. ENOand ECOwere also measured in C57Bl6 and IL-10-/- mice, ages 8–58 weeks old, the relationship of which was determined by regression analysis. S-methionyl-L-thiocitrulline (SMTC), and tin protoporphyrin (SnPP) were used to inhibit neuronal/constitutive NOS-1 and heme-oxygenase, respectively, and alter NO and CO production, respectively, as assessed by paired t-tests. Methacholine-associated airway responses (AR) were measured by the enhanced pause method, with comparisons by repeated measures ANOVA and post-hoc testing.ResultsENOwas significantly elevated in naïve IL-10-/-(9–14 ppb) and NOS-2-/-(16 ppb) mice as compared to others (average: 5–8 ppb), whereas ECOwas significantly higher in naïve A/J, NOS-3-/-(3–4 ppm), and MKK3-/-(4–5 ppm) mice, as compared to others (average: 2.5 ppm). As compared to C57Bl6 mice, AR of IL-10-/-, JNK1-/-, NOS-2-/-, and NOS-3-/-mice were decreased, whereas they were greater for A/J and MKK3-/-mice. SMTC significantly decreased ENOby ~30%, but did not change AR in NOS-2-/-mice. SnPP reduced ECOin C57Bl6 and IL-10-/-mice, and increased AR in NOS-2-/-mice. ENOdecreased as a function of age in IL-10-/-mice, remaining unchanged in C57Bl6 mice.ConclusionThese results are consistent with the ideas that: 1) ENOis associated with mouse strain and knockout differences in NO production and AR, 2) alterations of ENOand ECOcan be measured non-invasively with induction of allergic AI or inhibition of key gas-producing enzymes, and 3) alterations in AR may be dependent on the relative balance of NO and CO in the airway.

Exacerbations of COPD are a leading indication for MV in the intensive care unit. A thorough understanding of the pathophysiology of AVF in COPD is critical for physicians caring for these patients. In particular, physicians should understand DHI and use the ventilator and ancillary techniques to minimize its impact. Noninvasive positive-pressure ventilation should be considered strongly in relatively stable patients with an adequate mental status and manageable secretions. Once AVF resolves, patients should be removed from the ventilator as soon as is safe to do so to minimize the adverse effects of prolonged MV. An organized approach to weaning and identifying patients capable of independent breathing is crucial. Most patients with COPD and AVF benefit from MV and generally return to or approach their premorbid functional status. A significant subset, however, will not benefit from, or choose not to undergo, MV. Deciding upon appropriate therapeutic options for these patients relies heavily on effective communication between physician and patient. Comprehensive discussions before the development of AVF can assist decision-making after respiratory failure develops.

Heme oxygenase (HO) was first described, in 1968, as the enzyme responsible for the rate-limiting step in the catalytic breakdown of the heme moiety of hemoglobin, and understandably, initial work focused on the regulation and function of this enzyme in heme metabolism (1). That HO could be important for much more than the color changes of a bruise as heme was broken down through biliverdin to bilirubin, was not suspected until the work of Tyrrell and his colleagues. These researchers showed that HO-1 could be vigorously induced not just by heme, its natural substrate, but by a variety of agents that had as their common feature the ability to generate reactive oxidant species (ROS) (2). Examples of the broad spectrum of agents capable of inducing HO include lipopolysaccharide (LPS), phorbol esters, sodium arsenite, hydrogen peroxide, ultraviolet radiation, hyperthermia, hyperoxia, sulfhydryl reagents, heat shock, and heavy metals. This extraordinary variety of inducers is surprising for an enzyme subserving a seemingly housekeeping function of heme turnover, and speculation arose that the enzyme was also vital to cellular homeostasis.

Exhaled carbon monoxide and nitric oxide reflect allergic inflammation in asthma and have clinical utility for monitoring disease severity. The effects of allergen challenge and of inflammatory versus non-inflammatory bronchoconstrictive stimuli on the exhalation kinetics of these gases are unclear. The aim of this study is to compare and contrast the effects of methacholine and allergen challenges on the exhaled levels of carbon monoxide and nitric oxide in a cohort of adult subjects with atopic asthma. Eight subjects underwent inhaled allergen testing, nine underwent methacholine testing, and five subjects underwent both tests. Additionally, seven healthy controls underwent a mock challenge. Mixed-expired and end-expiratory carbon monoxide and end-expiratory nitric oxide levels were measured together with spirometry before, during (i.e. after each step of the inhalations), and after the challenges. Decreases in both end-expiratory (-14.4% in 9/11 subjects, p = 0.04) and mixed-expired (-7.5%, 9/11 subjects, p = 0.007) levels of carbon monoxide were noted during the immediate phase of the allergen challenge, with similar reductions after methacholine challenge, but levels were unaffected by repeated forced vital capacity exhalations alone. End-expiratory nitric oxide increased during the immediate phase of allergen challenge in 10/13 subjects (+10.8%, p = 0.05), but decreased after methacholine challenge in 14/14 subjects (-32.2%, p = 0.00009). Bronchospasm negatively modulates exhaled carbon monoxide and nitric oxide, but the inflammatory stimulus of allergen exposure increases exhaled nitric oxide. Measurements of exhaled monoxides may need to be referenced to the FEV(1).

Carbon monoxide (CO) can be detected on the exhaled breath of humans. Exhaled CO (E-CO) originates from the inspiration of ambient CO and from endogenous metabolic sources that include heme metabolism catalyzed by heme oxygenase (HO) enzymes. HO occurs in both constitutive (HO-2) and inducible (HO-1) forms; the latter responds to pro-inflammatory or pro-oxidative stimuli. E-CO may arise in the airways from inducible HO-1 activity in the bronchial epithelium, alveolar macrophages and other lung cell types, as a consequence of local inflammation, and from the alveolae in equilibrium with carboxyhemoglobin (Hb-CO) in the pulmonary circulation. Elevations in Hb-CO in turn may reflect increases in ambient CO, as well as increased HO activity in systemic tissues. E-CO increases dramatically in active smokers and can be used to monitor the smoking habit. Elevations in E-CO have been observed in critically ill or post-surgical patients and those with various pulmonary diseases associated with inflammation, including chronic obstructive pulmonary disease (COPD), asthma, cystic fibrosis and infections. Despite improvements in the standardization and sensitivity of methods to detect E-CO, the predictive value of this measurement as a diagnostic tool remains unclear.