American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Jun 1994
Soluble TNF receptors (TNF-sR55 and TNF-sR75) in lung allograft recipients displaying cytomegalovirus pneumonitis.
Two distinct types of tumor necrosis factor receptors (TNF-R) have been identified (TNF-R55 and TNF-R75). Both TNF-R also exist in soluble forms (TNF-sR), resulting from the release of the extracellular domains (TNF-sR55 and TNF-sR75). TNF-sR may play an important role in vivo as they can bind to TNF alpha and prevent ligand binding to the cellular TNF-R, thus acting as naturally occurring inhibitors of TNF alpha. ⋯ Serum TNF alpha concentration was low in case of rejection or in control subjects (< 20 pg/ml). Conversely increased levels of TNF alpha were detected in the serum of six out of the 12 patients with CMV pneumonitis (p < 0.03 versus rejection and control subjects). Ganciclovir treatment of CMV pneumonitis led to a dramatic decrease of TNF alpha, TNF-sR55, and TNF-sR75 serum levels.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. J. Respir. Crit. Care Med. · May 1994
Physiologic effects of positive end-expiratory pressure and mask pressure support during exacerbations of chronic obstructive pulmonary disease.
To assess physiologic effects of continuous positive airway pressure (CPAP) and positive end-expiratory pressure (PEEP) during noninvasive pressure support ventilation (PSV) in patients with acute exacerbation of chronic obstructive pulmonary disease (COPD), we measured in seven patients the breathing pattern, lung mechanics, diaphragmatic effort (PTPdi), and arterial blood gases under four conditions: (1) spontaneous breathing (SB); (2) CPAP; (3) PSV of 10 cm H2O; and (4) PSV plus PEEP (PEEP + PSV). CPAP and PEEP were set between 80 and 90% of dynamic intrinsic PEEP (PEEPidyn) measured during SB and PSV, respectively. PEEPidyn was obtained (1) from the decrease in pleural pressure (delta Ppl) preceding inspiration, and (2) subtracting the fall in gastric pressure (delta Pga) caused by relaxation of the abdominal muscles from the delta Ppl decrease. ⋯ PSV increased minute ventilation, improved gas exchange, and decreased PTPdi. PEEP added to PSV, likewise CPAP compared with SB, further significantly decreased the diaphragmatic effort (PTPdi went from 322 +/- 111 to 203 +/- 63 cm H2O.s) by counterbalancing PEEPidyn, which went from 5.4 +/- 4.0 to 3.1 +/- 2.3 cm H2O. These data support the use of low levels of PEEP (80 to 90% of PEEPidyn) to treat acute exacerbation of COPD by means of mask PSV.
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Am. J. Respir. Crit. Care Med. · May 1994
Patient work of breathing during pressure support and volume-cycled mechanical ventilation.
A computer-assisted technique based on the equation of motion of the respiratory system was used to measure inspiratory work of breathing in 11 patients during pressure support ventilation (PSV) and assisted, volume-cycled mechanical ventilation (AMV). During both modes of ventilation, patient work of breathing was calculated as the difference between the total work performed on the respiratory system (as predicted by the equation of motion) and the work performed by the ventilator. Patient work of breathing during AMV was also calculated as the difference between ventilator work measured during assisted and controlled mechanical breaths. ⋯ In addition, when equal tidal volumes were delivered, there was no significant difference between the work performed by the patient during AMV and PSV. Patient work of breathing during PSV was found, however, to vary inversely with the level of pressure support. We conclude that: (1) patient work of breathing during AMV and PSV can be calculated using a computer-assisted technique based on the equation of motion of the respiratory system, and (2) depending on the amount of pressure support provided, patient work of breathing during PSV may be greater than, less than, or equal to the work performed during AMV.
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Am. J. Respir. Crit. Care Med. · May 1994
Gender- and race-specific effects of asthma and wheeze on level and growth of lung function in children in six U.S. cities.
The gender-and race-specific effects of asthma/wheeze on pulmonary function level and annual growth velocity were studied in a cohort of 10,792 white and 944 black children 6 to 18 yr of age, examined annually between 1974 and 1989 in six U. S. cities. In comparison with white boys who never reported asthma or wheeze, FEV1 levels were 5.7% lower and FEF 25-75 levels were 16.9% lower for white boys with a diagnosis of asthma who reported wheeze symptoms in the past year. ⋯ We conclude that in absolute terms, but not in percent terms, the pulmonary function deficits associated with asthma and wheeze increase throughout childhood. In the preadolescent and adolescent years, the mechanical properties of the lungs and the inflammatory process in asthmatics may differ by gender, leading to gender differences in their pulmonary function. We also conclude that lung function may not return to normal, even when asthmatics become asymptomatic.
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Am. J. Respir. Crit. Care Med. · May 1994
Should inverse ratio ventilation be used in adult respiratory distress syndrome?
IRV-induced increases in MAP are clearly associated with shunt reduction, but we find no studies that show shunt reduction without increased end-expiratory alveolar pressure. On the other hand, various studies in humans with ARDS and hyaline membrane disease and animal models of acute lung injury indicate that shunt reduction does not occur with IRV if there is no increase in end-expiratory alveolar pressure (21), that shunt reduction is the same with IRV as with conventional ventilation with PEEP when there are comparable levels of end-expiratory volume or alveolar pressure (16, 32), and that shunt reduction is greater when MAP is raised with PEEP than with IRV (27). Improved ventilation-perfusion matching with IRV is theoretically unlikely and, given the high FIO2 used in ARDS, improvements in oxygenation from more even ventilation would not be great. ⋯ However, these potentially salutary effects of IRV are unproven. On the other hand, there are potential deleterious effects of IRV, including increased risk of volotrauma and the requirements for heavy sedation and neuromuscular blockage. IRV remains of unproven value in the management of ARDS.