Respiratory physiology & neurobiology
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Respir Physiol Neurobiol · Sep 2004
Comparative StudyPersistence of diaphragmatic contraction influences the pulmonary inflammatory response to mechanical ventilation.
Because we already showed (Brégeon, F., Roch, A., Delpierre, S., Ghigo, E., Autillo-Touati, A., Kajikawa, O., Martin, T., Pugin, J., Portugal, H., Auffray, J., Jammes, Y., 2002. Conventional mechanical ventilation of healthy lungs induced pro-inflammatory cytokine gene transcription, Respir. Physiol. ⋯ Compared to the P group and despite the tidal volume was the same, we measured in the NP one a lower compliance of the respiratory system (Crs,stat), a longer inspiratory time (Ti), a negative inspiratory tracheal pressure (Ptr) wave preceding the pump-induced positive pressure wave, and a higher peak tracheal pressure. Moreover, in NP animals, gross autopsy showed negligible lung abnormalities, and marked reduction of leukocyte count and lung cytokines (P < 0.05). Thus, the absence of neuromuscular blockade decreased the pulmonary chemotactic response to MV suggesting that the total suppression of negative pressure waves elicited by the diaphragmatic (di) contractions could be involved in this lung response to positive pressure MV.
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Respir Physiol Neurobiol · Sep 2004
Comparative StudyIncreased hypoxic ventilatory response during 8 weeks at 3800 m altitude.
Acclimatization to chronic hypoxia (CH) increases ventilation (V(I)) and the isocapnic hypoxic ventilatory response (HVR) over 2-14 days but hypoxic desensitization blunts the HVR after years of CH. We tested for hypoxic desensitization during the first 2 months of CH by studying five normal subjects at sea level (SL) and for 8 weeks at 3800 m (CH, PI(O(2)) approximately 90 Torr). ⋯ HVD was similar at SL and during 8 weeks of CH. Hence, hypoxic desensitization of the HVR does not occur after only 8 weeks of hypoxia and the increased HVR during this time does not involve changes in HVD.
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Respir Physiol Neurobiol · Aug 2004
Comparative StudyEffects of mechanical load on flow, volume and pressure delivered by high-frequency percussive ventilation.
High-frequency percussive ventilation (HFPV) has proved its unique efficacy in the treatment of acute respiratory distress, when conventional mechanical ventilation (CMV) has demonstrated a limited response. We analysed flow (V(dot)), volume (V) and airway pressure (Paw) during ventilation of a single-compartment mechanical lung simulator, in which resistance (R) and elastance (E) values were modified, while maintaining the selected ventilatory settings of the HFPV device. ⋯ Although peak Paw increased 70.3% in relation to control value, mean Paw augmented solely 36.5% under the same circumstances (maximum of 9.4 cm H2O). Finally, a mechanism for washing gas out of the lung was suggested.
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Respir Physiol Neurobiol · Aug 2004
ReviewImplications of hypoxic hypometabolism during mammalian ontogenesis.
During hypoxia, many newborn mammals, including the human infant, decrease metabolic rate, therefore adopting a strategy common to many living creatures of all classes, but usually not adopted by adult humans and other large mammals. In acute hypoxic conditions, hypometabolism largely consists in actively dropping mechanisms of thermoregulation. One implication is a decrease in body temperature. ⋯ Upon termination of hypoxia, the newborn's metabolic rate recovers and growth resumes at higher rate. Even if body weight may be completely regained, alterations in the respiratory mechanical properties and in aspects of ventilatory control can persist into adulthood, a phenomenon not seen when the hypoxia was experienced at later stages of development. Some of the long-term respiratory effects of neonatal hypoxia are reminiscent of those observed in adult animals and humans native and living in high altitude regions.
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Respir Physiol Neurobiol · May 2004
Comparative StudyTongue mechanical characteristics and genioglossus muscle EMG in obstructive sleep apnoea patients.
The increased genioglossus muscle (GGm) activity seen in obstructive sleep apnoea syndrome (OSAS) may lead to increased fatigability or longer recovery time of the tongue. Maximal force, endurance, and recovery times of the tongue, electromyogram (EMG) absolute value, and EMG spectral analysis of the GGm obtained during submaximal contractions were compared in eight individuals without chronic snoring and eight OSAS patients. Endurance time values were not significantly different between the two groups (P = 0.40). ⋯ Final EMG median frequency was significantly higher (P = 0.01) and the final low-frequency EMG component smaller in the OSAS patients (P = 0.02). Patients did not have changes in endurance time or fatigability but had longer recovery times and changes in spectral analysis variations. This functional investigation may be helpful in determining the presence of OSAS and the potential contribution of the tongue to pharyngeal obstruction.