Biomedical subjects

A Belaguid

Publications and source records attributed to A Belaguid.

4 recordsLinked to original sources

PubMed1995

Persistent increased lung response to methacholine after normobaric hyperoxia in rabbits.

This study was performed to determine the occurrence and time course of airway hyperreactivity following exposure to normobaric hyperoxia. Twenty-six rabbits were studied. Twelve served as control (group 1), and 14 were exposed to normobaric hyperoxia (FiO2 > or = 95%) for 48 h: 9 rabbits (group 2) were studied after 1 day of recovery in room air and 5 (group 3) after 7 days. The rabbits were anesthetized, curarized and artificially ventilated. Respiratory resistance (Rrs) and elastance (Ers) and their respective changes induced by cumulative doses of aerosolized methacholine were assessed by the multiple linear regression analysis of airway pressure, tidal flow and volume. Weight-specific Rrs and Ers were significantly higher in group 2 (respectively, 87.7 +/- 6.5 cmH2O.L-1.sec.kg and 1100.2 +/- 87.1 cmH2O.L-1.kg, mean +/- SEM) than in group 1 (respectively, 65.2 +/- 3.2 cmH2O.L-1.sec.kg and 904.4 +/- 49.7 cmH2O.L-1.kg (P < 0.05)), but were not different from group 3 (79.4 +/- 7.9 cmH2O.L-1.sec.kg and 952.3 +/- 125.0 cmH2O.L-1.kg, respectively). The dose of methacholine required to increase Rrs by 50% (PDRrs50) was significantly lower in both treated groups: 0.37 +/- 0.11 mg in group 2 and 0.51 +/- 0.19 mg in group 3 vs 2.07 +/- 0.51 mg in group 1 (P < 0.05)). PDErs50 was significantly lower in group 2 (0.45 +/- 0.15 mg) and 3 (0.75 +/- 0.43 mg) compared with controls (1.11 +/- 0.26 mg (P < 0.05)). These results show that hyperoxia induces an increase in Rrs and Ers, and airway hyperreactivity in the rabbit. The latter is prolonged beyond the immediate post-exposure period.

Analysis of Variance↗

PubMed1994

Variations in flows and pressures during jet ventilation in the infant: a model study.

Ventilatory flow rates with either He-O2 (heliox) or N2-O2 (nitrox) mixtures during high frequency jet ventilation (HFJV) were calculated using a mathematical model, and were measured in a physical monoalveolar model of the infant lung. A constant flow was delivered to the model (Vd) drawing with it an entrained flow (Ve). When the inspiratory time (Tl) was long, a back flow (Vr) was generated that increased progressively as the alveolar pressure increased. In order to reduce Vr, the reflux time (Tr), i.e., the time needed for the injected gas to reflux, was measured (Trm) and calculated (Trc) with the model. The Tr depends on both chest-lung compliance and resistance to reflux as well as on the Ve/Vd ratio. For a given setting of the ventilator, values of Trm and Trc were significantly lower with heliox than nitrox (P < 0.01), and the correlation between Trm and Trc were fair with both gases. Tidal volume (VT) was calculated when the Tl was interrupted at Tr. The values of VT were significantly higher with helix than nitrox (P < 0.05). It is concluded that the evaluation of Tr during HFJV may provide useful information for setting the ventilator.

Airway Resistance↗

PubMed1993

Low-frequency vs. high-frequency respiratory mechanics after methacholine challenge in artificially ventilated rabbits.

Respiratory system resistance (Rrs) and elastance (Ers) were estimated by two methods, before and after methacholine in six anesthetized, paralyzed, and artificially ventilated rabbits. Rrs and Ers were obtained (1) by multiple linear regression analysis of the relationship between tracheal pressure and tidal volume and flow [Rrs(mlr)], Ers(mlr), and (2) by analysis of the Fourier transforms of tracheal pressure and flow resulting from 4 to 30 Hz pseudorandom pressure oscillations delivered by an Infant Star respirator [Rrs(os), Ers(os)]. Rrs(os) was significantly lower than Rrs(mlr). For instance, Rrs(os) at 20 Hz [Rrs(os)20] was (mean +/- SD) 17.3 +/- 3.5 vs 21.4 +/- 3.6 cm H2O x L-1 x s (P < 0.01) for Rrs(mlr). Ers(os) was significantly higher than the respective value obtained by multiple linear regression (718.2 +/- 81.0 vs 403.7 +/- 43.0 cm H2O L-1; P < 0.01). After methacholine, the changes of respiratory mechanics were similar with both methods. Rrs(mlr) and Rrs(os)20 increased respectively by 131 +/- 45 and 134 +/- 76%, and Ers(mlr) and Ers(os) increased respectively by 63 +/- 7 and 54 +/- 13%. A significant correlation was observed between Rrs(mlr) and Rrs(os)20 (r = 0.97) and between Ers(mlr) and Ers(os) (r = 0.96). We conclude that positive response to methacholine may be detected by forced oscillation as well as by multiple linear regression. However, the identified physiological components of the lung response (alteration in lung viscoelastic properties, increased lung inhomogeneity or increased intrathoracic airway shunt) are likely to be different with each method.

Airway Resistance↗

PubMed1991

High frequency jet ventilation and upper tracheal stenosis: a model study.

A chest-lung model, consisting of a human laryngo-tracheo-bronchial tree cast (4 or 5 bronchial generations) tightly enclosed in a 100 l rigid box was used to assess the potential efficiency of high frequency jet ventilation in patients with upper tracheal stenosis. The elasticity of the air in the box stimulated normal adult chest-lung compliance. Diaphragms (0.5 or 1.5 cm thick) were inserted into the upper trachea to simulate stenoses of 0.7, 1, 1.5 and 1.75 cm inner diameter. A rigid injector-catheter (5 mm outside diameter) was directed in the axis of the trachea with its tip 2.5 cm beneath the stenosis. The end inspiratory alveolar pressure (PA), the end expiratory pressure (PEEP) and the tidal volume (VT) were measured at a rate of 100/min and 30% inspiratory to total periods ratio. Entrained flow, Vem, measured at the start of air insufflation, was compared to that calculated (Vec) from a simple model. For a given setting of the ventilator, PEEP, PA--PEEP and VT were approximately linearly related to the difference in diameters of stenosis and injector. While PEEP decreased, both PA--PEEP and VT increased with increasing diameter of stenosis. When the diameter of the stenosis was higher than 1.5 cm no changes in PA--PEEP and VT were observed, owing to the narrowest section of the larynx. Vec was always higher than Vem. The thickness of the stenosis did not affect the results, and the diameter of the stenosis appeared to be the main factor affecting the ventilatory parameters under our experimental conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

High-Frequency Jet Ventilation↗