Seminars in respiratory and critical care medicine
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The term obesity hypoventilation syndrome (OHS) refers to the combination of obesity and chronic hypercapnia that cannot be directly attributed to underlying cardiorespiratory disease. Despite a plethora of potential pathophysiological mechanisms for gas exchange and respiratory control abnormalities that have been described in the obese, the etiology of hypercapnia in OHS has been only partially elucidated. Of particular note, obesity and coincident hypercapnia are often associated with some form of sleep disordered breathing (apnea/hypopnea or sustained periods of hypoventilation). ⋯ A unifying view of how this comes about is presented in the following review. In brief, our concept is that chronic sustained hypercapnia (as in obesity hypoventilation) occurs when the disorder of ventilation that produces acute hypercapnia interacts with inadequate compensation (both during sleep and during the periods of wakefulness); neither alone is sufficient to fully explain the final result. The following discussion will amplify on both the potential reasons for acute hypercapnia in the obese and on what is known about the failure of compensation that must occur in these subjects.
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Semin Respir Crit Care Med · Jun 2009
ReviewHypoventilation in asthma and chronic obstructive pulmonary disease.
Chronic hypoventilation is a marker of disease severity in asthma and chronic obstructive pulmonary disease (COPD). The degree to which this predicts severity or objective measures of lung function is variable, and more reliable for COPD than for asthma. ⋯ There is consensus that early treatment with noninvasive ventilation for acute hypoventilation due to a COPD exacerbation is not only highly effective, but it reduces mortality, the need for endotracheal intubation, and hospital length of stay. There is probable benefit to the use of noninvasive ventilation in acute asthma, but the evidence to support this is far less robust than for COPD.
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The diaphragm is a chief muscle of inspiration. Its paralysis can lead to dyspnea and can affect ventilatory function. Diaphragmatic paralysis can be unilateral or bilateral. ⋯ In bilateral diaphragm paralysis or in patients with ventilatory failure continuous positive airway pressure or mechanical ventilation and tracheostomy are generally needed. Prognosis is good in unilateral paralysis, especially in the absence of underlying neurological or pulmonary process. Prognosis is usually poor in patients with advanced lung disease, bilateral paralysis, and chronic demyelinating conditions.
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Despite potent antibiotics, community-acquired pneumonia (CAP) remains the most common cause of death from infection and the seventh overall leading cause of death in the United States. For this reason, interest has been redirected into non-antibiotic therapeutic measures. Despite theoretical benefits, the existing literature does not suggest a clear benefit for corticosteroid treatment, but large prospective randomized trials are needed. ⋯ Exogenous surfactant replacement is being explored as adjunctive therapy for acute lung injury due to CAP. Statin use before CAP diagnosis is associated with improved outcome but requires further research to determine if initiation at the time of diagnosis will affect outcome. Other therapies have theoretical benefit but are not yet in the stage of clinical trials.
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Semin Respir Crit Care Med · Apr 2009
ReviewStreptococcus pneumoniae: does antimicrobial resistance matter?
Over the past 3 decades, antimicrobial resistance among Streptococcus pneumoniae, the most common cause of community-acquired pneumonia (CAP), has escalated dramatically worldwide. In the late 1970s, strains of pneumococci displaying resistance to penicillin were described in South Africa and Spain. By the early 1990s, penicillin-resistant clones of S. pneumoniae spread rapidly across Europe and globally. ⋯ Given these confounding factors, dissecting out the impact of antimicrobial resistance on clinical outcomes is difficult, if not impossible. Prospective, randomized trials designed to assess the clinical significance of antimicrobial resistance among pneumococci are lacking, and for logistical reasons, will never be done. Does in vitro resistance translate into clinical failures? Should changing resistance patterns modify our choice of therapy for CAP or for suspected pneumococcal pneumonia? In this review, we discuss several facets, including mechanisms of antimicrobial resistance among specific antibiotic classes, epidemiology and spread of antimicrobial resistance determinants regionally and worldwide, risk factors for acquisition and dissemination of resistance, the impact of key international clones displaying multidrug resistance, the clinical impact of antimicrobial resistance, and strategies to limit or curtail antimicrobial resistance among this key respiratory tract pathogen.