Biomedical subjects

A Harf

Publications and source records attributed to A Harf.

At least 127 records · Page 7Linked to original sources

PubMed1994

Acoustic method to estimate the longitudinal area profile of endotracheal tubes.

A problem in mechanical ventilation is the accumulation of mucus secretions in the endotracheal tube (ETT), which tends to reduce the patent cross-sectional area. Here we characterized the extent and locus of the ETT obstruction using an acoustic reflection method recently modified to be applied at bedside. Experiments were conducted both in vivo in 10 intubated patients and in vitro in ETT with or without known constrictions of 1 to 3 mm over 5 cm, located at various distances from the ETT entry: 5, 10, 15, and 20 cm. Acoustic results were compared with the results obtained by an hydraulic reference method, which was the only method available to measure ETT obstruction in mechanically ventilated patients. In vivo acoustic results showed that area reductions were maximal near the tracheal extremity of the ETT, with a range from 2 to 36% (mean value 13 +/- 10%), when estimated relative to the area measured in an unused ETT of the same inner diameter (7 to 9 mm). Statistical analysis of the differences between acoustic reflection data and hydraulic data showed that the two methods did not differ significantly. In vitro acoustic results obtained in constricted ETT showed a highly significant correlation with the actual area (r = 0.97, p = 0.0001). Thus, reductions in ETT area may be detected, quantified, and located by the present acoustic reflection method, which therefore provides a means to avoid emergency extubation because of ETT obstruction.

Acoustics↗

PubMed1994

Prevalence of sleep-disordered breathing in patients on a heart transplant waiting list.

We investigated the prevalence of sleep-disordered breathing in 20 outpatients on a heart transplant waiting list. All were younger than 60 years and had severe stable cardiac failure with a cardiac index below 2.5 L/min/m2 and a left ventricular ejection fraction below 25%. Nine patients (45%) exhibited ten or more apneas and hypopneas per hour of sleep (apneic group). In all patients but one, apneas and hypopneas were predominantly of the central type and occurred during Cheyne-Stokes respiration. There were no statistically significant differences between the apneic and nonapneic groups of patients in terms of age (51 +/- 5 years vs 49 +/- 11), body mass index (24 +/- 4 kg/m2 vs 22 +/- 3), cardiac index (1.87 +/- 0.35 L/min/m2 vs 1.84 +/- 0.40), isotopic left ventricular ejection fraction (13 +/- 5 vs 12 +/- 3%), arterial blood gas, or pulmonary function tests. Hypnogram characteristics showed poorer sleep quality in the apneic group than in the nonapneic group, with a larger number of arousals; this difference was found both for arousals lasting more than 30 s (8 +/- 5/h vs 4 +/- 2) and for arousals lasting less than 30 s (18 +/- 16/h vs 5 +/- 6) and was associated with increased wakefulness after sleep onset in the apneic group (138 +/- 82 min vs 84 +/- 45). Arousals were strongly associated with hyperpneic phases of Cheyne-Stokes respiration. We conclude that sleep-disordered breathing is common in patients with end-stage heart disease and adversely affects the quality of sleep.

Cheyne-Stokes Respiration↗

PubMed1994

Changes in respiratory resistance to low dose carbachol inhalation and to pneumatic trouser inflation are correlated.

Inflation of the leg compartments of pneumatic trousers increases thoracic blood volume. The resultant response in respiratory impedence was investigated in nine normal volunteers, and compared with the response to increasing doses of inhaled carbachol. Respiratory impedance was measured by the forced oscillation technique (4-32 Hz), and respiratory resistance at zero frequency (R0) was extrapolated from linear regression analysis of resistive impedance versus frequency. The mean increase in R0 was 31% after inhalation of 125 micrograms carbachol, and 21% after inflation of pneumatic trousers. The percentage changes in R0 following pneumatic trouser inflation highly correlated those induced by inhalation of 125 micrograms carbachol (r = 0.98) Our data demonstrate that, even in normal subjects, pneumatic trouser inflation causes an increase in respiratory resistance, which can be predicted by the response to a low dose of carbachol. These results support the assumption that cholinergic agents might not only be bronchoconstrictors but also vasodilators of the bronchial vessels. At a low dose, the vasodilating action of carbachol could be the major factor involved in the respiratory response.

Adult↗

PubMed1994

Do turbines with servo-controlled speed improve continuous positive airway pressure generation?

Nasal continuous positive airway pressure (CPAP) devices with a servo-mechanism to control pressure have recently been developed. We evaluated six such devices and three conventional systems in terms of effectiveness in maintaining constant pressure. Machines were tested with pressure levels of 5, 10 and 15 cmH2O. Dynamic behaviour was evaluated: 1) by calculating the imposed work of breathing during simulated breath generated by a sinusoidal pump; and 2) by following the fall in pressure after a transient flow of 1 l.s-1. Quasi-static behaviour was evaluated by simulating a predetermined air leak. Under dynamic conditions, work of breathing was lowest with one conventional nasal CPAP device and three servo-controlled nasal CPAP devices; whereas, the highest levels of work of breathing were recorded with two servo-controlled nasal CPAP devices. The pressure-time response to a transient flow yielded similar results, with a significant inverse correlation between pressure values observed after 300 ms and imposed work of breathing during simulated breathing (r = -0.91). Under quasi-static conditions, microprocessor servo-controlled devices exhibited the best performance. These results suggest that microprocessor servo-controlled nasal CPAP devices are not always the best systems for maintaining constant airway pressure in dynamic situations. However, they are more effective in ensuring maintenance of the desired pressure in the event of an air leak at the mask.

Equipment Design↗

PubMed1993

High-frequency ventilation in newborn lambs after intra-uterine creation of diaphragmatic hernia.

Infants with congenital diaphragmatic hernia (CDH) die, because their lungs are hypoplastic and their pulmonary vascular resistance remains elevated after birth. In human newborns, it is difficult to appreciate the benefit of new therapeutic approaches, because the pathological findings are not uniform, the disease is rare and the clinical criteria for poor prognosis with conventional therapy are uncertain. To study the benefit of high-frequency ventilation (HFV) the use of Tolazoline in CDH, we created a diaphragmatic defect in sheep fetuses at 0.6 gestation and studied full-term newborns after a caesarian section. A sternotomy was performed to place catheters and flow probes on the aorta and pulmonary artery and to clamp the ductus arteriosus and the left pulmonary artery. Twins were used as control, and the CDH lambs were either ventilated with conventional ventilation (CV) or HFV. 23 ewes were operated upon with a 22% abortion rate and 31 newborn lambs (10 controls and 21 CDH) were studied. A complete gasometric and hemodynamic study was performed in 23 lambs (7 controls, 8 CDH with CV and 8 CDH with HFV). Clinical and pathological findings of the lambs with CDH were very similar to severe CDH in humans with bilateral lung hypoplasia, severe respiratory distress, high pulmonary vascular resistance and severe hypoxemia. HFV dramatically improved CO2 elimination, allowed less aggressive ventilation, and was associated with higher flows and lower systemic and pulmonary vascular resistance. However, HFV did not improve oxygenation leaving the newborn with severe hypoxemia associated with massive intrapulmonary foramen ovale shunting from right to left.

Animals↗

PubMed1993

Techniques for measuring respiratory mechanics: an analytic approach with a viscoelastic model.

A homogeneous model with stress relaxation that is described by a pure viscoelastic component was recently proposed to describe the mechanical behavior of the respiratory system during mechanical ventilation (Bates et al. J. Appl. Physiol. 67: 2276-2285, 1989). With the use of this model, analytic expressions of the pressure in response to typical volume inputs are developed, and the recently published studies relating to the influence of the ventilatory pattern on respiratory mechanics are reviewed and analyzed. The analytic expression of pressure responses to rapid airway occlusion following constant-flow inflation and to sinusoidal volume oscillations allows prediction of most of the reported results. The theoretical analysis suggests that in normal subjects the observed flow and volume dependencies of respiratory mechanics are, in fact, illustrations of the dependence of the viscoelastic resistance on inspiratory time and respiratory frequency. Thus the homogeneous viscoelastic model appears suitable to describe respiratory system mechanical behavior under mechanical ventilation.

Animals↗

PubMed1993

Bronchoconstriction-induced hyperinflation assessed by thoracic area measurement in guinea pigs.

The changes in end-expiratory lung volume (EELV) accompanying histamine-induced bronchoconstriction were compared for two routes of drug administration in anesthetized, paralyzed, and mechanically ventilated guinea pigs. Changes in EELV were estimated from measurements of thoracic cross-sectional area, assessed from the voltage induced by an external uniform magnetic field in a pickup coil encircling the rib cage. Increasing doses of histamine were administered as bolus injections in Group 1 (n = 7) and as nebulizations in Group 2 (n = 7). After each bronchial challenge, the maximum change in EELV and the associated intrinsic positive end-expiratory pressure (PEEPi) were measured at the same time. In both groups, bronchoconstriction was accompanied by an increase in EELV, which was related to the degree of bronchoconstriction and reached about 70 to 100% of the basal functional residual capacity. The increases in EELV were linearly related to the PEEPi values (p < 0.001) and did not depend on the route of histamine administration. These results indicate that dynamic hyperinflation is not the only mechanism involved in lung volume response to bronchoconstriction and suggest that gas trapping may have occurred in alveolar spaces.

Administration, Inhalation↗

PubMed1993

Involvement of tachykinins in pentamidine-induced airway constriction and microvascular leakage in the guinea pig.

We investigated the effects of aerosolized pentamidine isethionate on airway constriction and microvascular leakage in the guinea pig, and the role of tachykinins in these abnormalities. The bronchoconstrictor response to pentamidine was determined in anesthetized, tracheotomized and mechanically ventilated guinea pigs by exposing them to increasing concentrations of aerosolized pentamidine (5 to 30 mg/ml; 60 breaths). Respiratory system resistance was measured by the occlusion method. Airway microvascular permeability was evaluated by measuring the Evans blue dye concentration in the trachea and main bronchi. Aerosolized pentamidine caused a concentration-related increase in respiratory system resistance that was prevented by pretreatment with 50 mg/kg capsaicin given subcutaneously 2 wk before pentamidine and was significantly reduced by pretreatment with 1 mg/kg morphine given intravenously. Pretreatment with 10(-4) M aerosolized phosphoramidon (90 breaths) significantly enhanced the bronchoconstrictor response to pentamidine. Aerosolized pentamidine (50 mg/ml; 90 breaths) increased airway microvascular permeability, as the Evans blue dye concentration was 72.6 +/- 3.7 ng/mg tissue in guinea pigs aerosolized with pentamidine versus 34.2 +/- 3.5 ng/mg tissue in the controls. Capsaicin pretreatment inhibited the increase in microvascular leakage induced by pentamidine. Pretreatment with 5 mg/ml aerosolized albuterol (90 breaths) prevented the bronchoconstrictor response to pentamidine but failed to prevent the pentamidine-induced increase in microvascular permeability. Atropine did not modify the bronchoconstrictor response to pentamidine. These results indicate that in the guinea pig, pentamidine isethionate induces bronchoconstriction and airway microvascular leakage, which are mediated by tachykinins released from sensory nerves. Albuterol, which is used in humans to prevent bronchoconstriction, does not seem able to prevent airway edema.

Aerosols↗

PubMed1993

Mechanisms of impaired arterial oxygenation in patients with liver cirrhosis and severe respiratory insufficiency. Effects of indomethacin.

The mechanisms of impaired arterial oxygenation that occur in certain patients with chronic liver cirrhosis are still debated. In the present study, we investigated nine cirrhotic patients with severe respiratory disability (mean PaO2, 64 +/- 5 mm Hg), using the inert gas elimination technique to assess the distribution of ventilation-perfusion (VA/Q) ratios. We also determined shunt fraction during pure oxygen breathing, both in supine and sitting positions. To test the hypothesis that vasodilating prostaglandins could contribute to alter gas exchange in such patients with cirrhosis, we examined the hemodynamic and gasometric responses to indomethacin, 50 mg IV, in six of them. During baseline conditions, patients had high cardiac index (CI, 4.9 +/- 0.2 L/min/m2), and low pulmonary (PVR, 1.78 +/- 0.37 mm Hg/L/min/m2) or systemic (SVR, 17.7 +/- 1.15 mm Hg/L/min/m2) vascular resistances. Large intrapulmonary shunt fraction was documented in each patient with a mean value of 19.6 +/- 2.7 percent. Small perfusion in low VA/Q areas was associated with shunt in only three patients (2.5 to 5.3 percent of blood flow). Arterial PO2 was negatively related to shunt (p < 0.01) and to the dispersion of blood flow distribution (p < 0.02). There was no difference between measured and predicted PaO2. Shunt estimates from the inert gas and the 100 percent O2 breathing techniques were, respectively, 19.6 +/- 2.7 percent and 21.7 +/- 3.0 percent. During 100 percent oxygen breathing, changing from supine to sitting position decreased PaO2 from 401 +/- 50 to 333 +/- 64 mm Hg (p < 0.02), while O2 shunt remained unchanged, arteriovenous difference widened, and mixed venous PO2 decreased, from 61 +/- 3 to 47 +/- 4 mm Hg (p < 0.001). Indomethacin did not improve gas exchange or VA/Q distribution and did not affect systemic or pulmonary hemodynamics. The results show that in cirrhotic patients with severe respiratory disability, intrapulmonary shunting is the main determinant of impaired gas exchange, with no evidence of a defect in oxygen diffusion or an extrapulmonary shunt. Vasodilating prostaglandins do not appear to contribute to these alterations.

Aged↗

PubMed1993

Effects of obesity on respiratory resistance.

To assess the effects of obesity on pulmonary function, 46 healthy subjects exhibiting various degrees of obesity underwent lung function tests. Subjects were divided into three groups according to body mass index (BMI): 13 had minimal obesity (BMI, 25 to 29 kg/m2, group 1); 24 had a BMI in the 30 to 40 range (group 2); and 9 displayed to morbid obesity (BMI > 40, group 3). Respiratory resistance was estimated by the forced random noise oscillation technique and airway resistance was determined by body plethysmography. Lung volumes and expiratory flows were also determined and significant negative correlations with BMI were found. Expiratory flows diminished in proportion to lung volumes, and the ratio of forced expiratory volume in 1 s to forced vital capacity was within normal limits. Although expiratory flows did not suggest bronchial obstruction, both respiratory resistance and airway resistance rose significantly with the level of obesity (p < 0.005 and p < 0.025, respectively), from 3.2 (+/- 0.02) and 3.2 (+/- 0.02) cm H2O.s.L-1, respectively, in group 1, to 5.5 (+/- 0.06) and 5.0 (+/- 0.05), respectively, in group 3. Evaluation of the factors responsible for this increased resistance disclosed a significant linear correlation between airway conductance and functional residual capacity (r = 0.70, p < 10(-4)), but specific airway conductance was found to be independent of the degree of obesity. The difference between respiratory resistance and airway resistance did not widen significantly according to the level of obesity, suggesting that chest wall resistance was not a factor enhancing these resistances. Taken together, these findings suggest that in addition to the elastic load, obese subjects have to overcome increased respiratory resistance resulting from the reduction in lung volumes related to being overweight.

Adolescent↗

PubMed1993

Assessment of the respiratory compliance in awake subjects using pressure support.

Pressure support (PS), a new mode of ventilatory assistance, is known to induce respiratory muscle relaxation. It was used to obtain reliable measurements of the compliance of the respiratory system (Crs) in awake subjects. PS was applied, through a mouthpiece, at four successive levels (0, 0.75, 1 and 1.25 kPa) to 30 healthy subjects. At the highest PS level, the subject's relaxation was obtained as assessed by a decrease in the occlusion pressure from 0.10 +/- 0.06 to 0.05 +/- 0.04 kPa, whereas the minute ventilation increased (from 7.5 +/- 1.5 to 13.8 +/- 3.3 l.min-1), and the end-tidal carbon dioxide tension (PCO2) decreased (from 5.0 +/- 0.4 to 3.2 +/- 0.5 kPa) below its apnoea threshold. In three subjects, respiratory muscle relaxation was confirmed by a fall in diaphragmatic electromyographic activity. Crs was calculated as the ratio of the tidal volume to the corresponding end-inspiratory airway pressure (i.e. PS level) since, at end inspiration, a zero-flow period was obtained. Crs was highly correlated (r = 0.77) to the height (Ht) of the subjects: Crs (l.kPa-1) = 3.56 x Ht (m) -4.86 (+/- 0.23), allowing normal values to be determined. In order to evaluate the applicability of the method to patients, Crs was measured in four patients with scoliosis, and was found to range from 45-82% of the predicted values. It is suggested that this simple method of Crs determination may be used to characterize various chest wall or pulmonary diseases.

Adult↗

PubMed1992

High impedance mechanical ventilator for small animals: use of programmable controller.

We built a simple high impedance ventilator, which generates a pattern of flow largely independent of respiratory mechanics, to mechanically ventilate anaesthetized small animals. The system includes a source of compressed gas with an electronic valve and a flow controller on the inspiratory side and a second valve on the expiratory side. The two valves are driven by a programmable controller. To assess the performance of this ventilator we measured the delivered tidal volume while the ventilator was connected to an external, gradually varying resistance. This resistance was progressively increased to simulate bronchoconstriction of the respiratory system. Comparison with a volume-controlled ventilator was made. The use of a programmable controller also allows control of different patterns of mechanical ventilation, such as end-inspiratory pause or the static pressure-volume relationship, which can be used to perform lung function tests. The system is a simple, versatile device allowing both reliable mechanical ventilation and lung function assessment in small rodents and is suitable for routine use in laboratories.

Animals↗

PubMed1992

A knowledge-based system for assisted ventilation of patients in intensive care units.

The procedure for weaning a patient with respiratory insufficiency from mechanical ventilation may be complex and requires expertise obtained by long clinical practice. We designed a knowledge-based system for the management of patients receiving respiratory support and implemented a weaning procedure. The system is intended for patients whose spontaneous respiratory activity is assisted by a Hamilton Veolar ventilator delivering a positive pressure plateau during inspiration (Pressure Support Ventilation mode). Our closed-loop real-time system running on a Personal Computer continuously adapts the assistance provided by the ventilator to the patient's evolution, and indicates when the patient can be withdrawn from the ventilator. Three parameters are used to appreciate the 'respiratory comfort' of the patient: breathing frequency, which we consider the most informative index, tidal volume and end-tidal CO2 pressure. A preliminary study of 19 patients was performed to evaluate the ability of our system to adapt the assistance to the patient's needs, with the main objective of facilitating weaning by gradually lowering the level of assistance. In 10 of these patients, considered as good candidates for weaning on the strength of objective criteria, the system maintained the breathing pattern in a zone of comfort for 95% of the period of assisted ventilation and stated that they were 'weanable'. This was consistent with the clinical evolution of all 10 patients. These results show that such a system can provide effective management for mechanically ventilated patients.

Adult↗

PubMed1992

Test of 20 similar intensive care ventilators in daily use conditions--evaluation of accuracy and performances.

Infrequent control, aging of components, may compromise the accuracy of ICU ventilators. In order to assess the reliability of ventilators during their clinical use, we bench tested a group of 20 CPU1 ventilators (Ohmeda) sampled at random in several ICU units. We found major leaks in 5 ventilators, attributable to the disposable tubings used in these systems. Mean error in expired tidal volume and corresponding standard deviation (precision) were greater than 100 ml in two. Positive end expiratory pressure measurement comprised a mean error higher than 2 cm H2O in 40% of the ventilators tested. The valve opening pressure threshold was correlated to the inspiratory flow (r = 0.81) contrary to the valve opening delay (average 138 +/- 40 ms). These two parameters did not correlate with the age of the ventilator. Our study addresses the need for periodic control of ventilator performance in order to minimize the risks of errors and malfunctions.

Age Factors↗

PubMed1992

Respiratory response to positive and negative inspiratory pressure in humans.

To investigate the effect of positive or negative inspiratory pressure on respiration, eight subjects breathed, either without or with added external dead space (VD, 600 ml), through either added inspiratory laminar flow resistances (RES; peak inspiratory airway pressure, Pinsp, down to -9 cmH2O) or with inspiratory pressure support (IPS; Pinsp up to +10 cmH2O). IPS, triggered by the subject's inspiratory effort, provided positive airway pressure throughout inspiration, but allowed for attainment of the subject's own respiratory pattern. The following main results were obtained with IPS or RES relative to the control (no IPS, no RES): (1) with VD, IPS led to small, but significant, increases in tidal volume (VT), respiratory frequency (fR) and ventilation (VE), with no changes in inspiratory time (TI) or duty cycle (TI/TT). Mean inspiratory flow (VT/TI) increased, and mouth occlusion pressure 0.1 sec after onset of inspiration (P0.1) decreased significantly with IPS. The changes during RES were essentially in the opposite direction; (2) without VD, similar, but smaller effects were observed, and only the changes in VT/TI and P0.1 during IPS were significant; (3) highly significant decreases were observed during IPS in end-tidal PCO2 (PETCO2); on the average from 39.6 to 29.2 Torr without VD, and from 45.7 to 39.3 Torr with VD breathing. A small, but significant decrease in PETCO2 occurred also during RES with VD. We conclude that while resistive loading is nearly completely compensated with but small changes in PETCO2, inspiratory pressure support leads to marked hyperventilation, which is not effectively counteracted by central timing commands.

Adult↗

PubMed1992

Airway anesthesia during positive and negative inspiratory pressure breathing in man.

We have measured the effects of airway anesthesia (aerosolized 5% lidocaine) on the respiratory pattern during positive or negative inspiratory pressure in 8 resting subjects. The subjects breathed through a 600 ml dead space (peak inspiratory airway pressure, Paw = -2 cmH2O) without or with negative (approx. -5 or -10 cmH2O) or positive (approx. +5 or +10 cmH2O) inspiratory pressure, provided by a laminar flow resistance or a positive pressure source, respectively. Control measurements were performed before and after measurements with airway anesthesia. Measurements included tidal volume, respiratory frequency, ventilation, inspiratory and expiratory duration, occlusion pressure (P0.1) and end-tidal PCO2. None of the parameters measured was significantly altered by airway anesthesia, which was effective in suppressing the cough reflex. We conclude that information from lung afferents that are suppressed with the elimination of the cough reflex is not important for the breathing pattern during resting ventilation with elevated tidal volume (dead space load) and with positive or negative inspiratory pressure.

Adult↗

PubMed1992

Risk factors for oxygen desaturation during sleep, after abdominal surgery.

The postoperative period after major abdominal surgery is known to be a period of increased episodic oxygen desaturation. In order to assess the risk factors for episodic desaturation, we have studied 29 surgical patients using pulse oximetry during the preoperative night (Npre) when they received benzodiazepine premedication and breathed air, and also during the first three nights after operation when they received nasal oxygen supplementation. Modal oxygen saturation (SpO2) exceeded 95% during all nights studied. The time spent at less than 90% (t90) and 85% (t85) SpO2 and the average SpO2 nadir (SpO2, nadir) did not differ each night. Heart rate was greater (mean 90.1 (SD 16.6) vs 68.2 (12.0) beat min-1, P < 0.001) during the second night after operation (N2) than during Npre. Before operation, the number of desaturations, t90 and t85 correlated with pharyngeal hypertrophy (P = 0.003, P = 0.002, P = 0.001, respectively). At the same time, t90 and t85 correlated with body mass index (P = 0.02 and P = 0.05, respectively). During N2, t90 correlated with radiological lung consolidation (P = 0.05) and SpO2, nadir correlated with FEV1 (P = 0.03). We conclude that there are several mechanisms responsible for oxygen desaturation and that these mechanisms differ before and after surgery.

Abdomen↗

PubMed1992

Effects of neuraminidase on airway reactivity in the guinea pig.

We investigated the effects of neuraminidase, a viral enzyme that cleaves alpha ketosidic cell-bound sialic acids, to see if it accounts for parainfluenza and influenza virus-induced airway hyperreactivity. Accordingly, Vibrio cholerae neuraminidase was administered intratracheally in guinea pigs, and airway reactivity was assessed 3 h later. Removal of sialic acid residues was evaluated by histologic studies. Airway responsiveness was determined in anesthetized, tracheotomized, and mechanically ventilated guinea pigs by exposing them to increasing concentrations of aerosolized bronchoconstrictor agents. Respiratory system conductance was measured by the occlusion method. Neuraminidase injected intratracheally did not change airway reactivity to 10(-4) to 10(-2) M acetylcholine or 10(-4) to 2.5 x 10(-3) M histamine; nor did it prevent aerosolized albuterol from inhibiting histamine-induced bronchoconstriction. Substance P (10(-6) to 5 x 10(-5) M) had no significant bronchoconstrictor effect on guinea pigs pretreated with saline or neuraminidase. In guinea pigs pretreated with aerosols of the neutral endopeptidase inhibitor phosphoramidon (10(-4) M) before the concentration curve to aerosolized substance P was recorded, neuraminidase significantly reduced substance P-induced bronchoconstriction. When bronchoconstriction was induced by the 4-11 fragment of substance P (10(-5) to 10(-2) M), which is devoid of positive charges, it did not differ significantly in guinea pigs pretreated with saline and those pretreated with neuraminidase. These results indicate that in the guinea pig, neuraminidase injected intratracheally does not induce non-specific airway hyperreactivity and may alter the binding of substance P to its receptors.

Albuterol↗