Journal of applied physiology
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Despite advances in critical care, the mortality rate in patients with acute lung injury remains high. Furthermore, most patients who die do so from multisystem organ failure. It has been postulated that ventilator-induced lung injury plays a key role in determining the negative clinical outcome of patients exposed to mechanical ventilation. ⋯ This information must then be integrated in the nucleus, and an appropriate response must be generated to implement and/or modulate its response and that of neighboring cells. In this review, we present a perspective on ventilator-induced lung injury with a focus on mechanisms and clinical implications. We highlight some of the most recent findings, which we believe contribute to the generation and propagation of ventilator-induced lung injury, placing a special emphasis on their implication for future research and clinical therapies.
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The ventilatory and arterial blood pressure (ABP) responses to isocapnic hypoxia during wakefulness progressively increased in normal subjects staying 4 wk at 5,050 m (Insalaco G, Romano S, Salvaggio A, Braghiroli A, Lanfranchi P, Patruno V, Donner CF, and Bonsignore G; J Appl Physiol 80: 1724-1730, 1996). In the same subjects (n = 5, age 28-34 yr) and expedition, nocturnal polysomnography with ABP and heart rate (HR) recordings were obtained during the 1st and 4th week to study the cardiovascular effects of phasic (i.e., periodic breathing-dependent) vs. tonic (i. e., acclimatization-dependent) hypoxia during sleep. ⋯ Despite attenuation of hypoxemia, ABP and HR behaviors during sleep in the 4th wk were similar to those in the 1st wk. Because ABP during periodic breathing in the ventilatory phase increased similarly to the ABP response to progressive hypoxia during wakefulness, ABP variations during ventilatory phases may reflect ABP responsiveness to peripheral chemoreflex sensitivity rather than the absolute value of hypoxemia, suggesting a major tonic effect of hypoxia on cardiorespiratory control at high altitude.
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Comparative Study
A new ventilator for monitoring lung mechanics in small animals.
Researchers investigating the genetic component of various disease states rely increasingly on murine models. We have developed a ventilator to simplify respiratory research in small animals down to murine size. The new ventilator provides constant-flow inflation and tidal volume delivery independent of respiratory parameter changes. ⋯ In contrast, if dynamic hyperinflation was prevented by lengthening expiratory time, (respiratory rate = 20 breaths/min), static compliance remained constant. More importantly, the coefficient of variation of the results decreased when lung volume shifts were prevented. In conclusion, airway challenge studies have greater precision when dynamic hyperinflation is prevented.
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We hypothesized that a decreased susceptibility to the development of hypocapnic central apnea during non-rapid eye movement (NREM) sleep in women compared with men could be an explanation for the gender difference in the sleep apnea/hypopnea syndrome. We studied eight men (age 25-35 yr) and eight women in the midluteal phase of the menstrual cycle (age 21-43 yr); we repeated studies in six women during the midfollicular phase. Hypocapnia was induced via nasal mechanical ventilation for 3 min, with respiratory frequency matched to eupneic frequency. ⋯ Premenopausal women are less susceptible to hypocapnic disfacilitation during NREM sleep than men. This effect was not explained by progesterone. Preservation of ventilatory motor output during hypocapnia may explain the gender difference in sleep apnea.