Dose-response effects and time course of effects of inhaled fenoterol on respiratory mechanics and arterial oxygen tension in mechanically ventilated patients with chronic airflow obstruction

Abstract

To investigate the dose-response relationship and the time course of the effects of fenoterol (a selective beta 2-adrenergic agonist) on respiratory function in mechanically ventilated patients with acute respiratory failure due to exacerbation of chronic airflow obstruction (CAO), seven consecutive acutely ill patients were studied within 3 days of the onset of mechanical ventilation. Airflow, airway pressure, and changes in lung volume were measured with the transducers of the 900 C Servo Ventilator, the last by electronic integration. The end-expiratory lung volume (EELV), the intrinsic positive end-expiratory pressure (PEEPi), the static respiratory compliance (Cstrs), maximum and minimum respiratory resistance (Rrsmax and Rrsmin), and arterial oxygen tension (PaO2), were measured under control conditions (all patients were receiving aminophylline infused at a constant rate) 5, 15, and 30 min after administration of 4 ml aerosolized saline solution and 5, 15, and 30 min after inhalation of 0.4, 0.8, and 1.2 mg fenoterol. After the last dose, measurements were repeated at 60, 120, and 180 min. We found that, on average, while saline did not cause any significant change in respiratory mechanics, a low dose (0.4 mg) of inhaled fenoterol was followed by a rapid (5 min) and significant decrease in Rrsmax (-33%), Rrsmin (-28%), EELV (-34%), and PEEPi (-44%), with a slight but not significant further fall with higher doses. However, changes were short-lasting, and by 2 h after the end of administration were no longer significant. PaO2 dropped significantly on average, with a maximum mean fall of 15 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerosol Therapy in Mechanically Ventilated Patients: Recent Advances and New Techniques

“…59 From these measurements in a passively ventilated patient, respiratory mechanics can be calculated as Most mechanically ventilated patients with COPD demonstrate a decrease in values of R rs max and R rs min after bronchodilator administration. 43,44,[46][47][48][49] Because delta R rs did not decrease significantly after albuterol administration in our studies, 48,49 it appears that the effect of albuterol was manifested mainly in the central airways without much apparent effect on viscoelastic behavior or time constant inhomogeneities in the lung. The time constant (R rs min ‫ן‬ C rs ) in our patients improved after albuterol administration but was not significantly different compared with the value at baseline.…”

“…Bronchodilators are among the most commonly used drugs in patients admitted to the ICU, 3 chiefly in mechanically ventilated patients with severe asthma or chronic obstructive pulmonary disease (COPD). [41][42][43][44][45][46][47][48][49][50] Because the presence of airflow limitation in mechanically ventilated patients is difficult to predict on clinical grounds, 51 the efficacy of bronchodilators in a heterogeneous population of mechanically ventilated patients needs further study. A response to bronchodilator administration has been observed after administration of either aerosolized beta-adrenergic 41,[46][47][48][49] or anticholinergic bronchodilators.…”

“…A response to bronchodilator administration has been observed after administration of either aerosolized beta-adrenergic 41,[46][47][48][49] or anticholinergic bronchodilators. 42,45,46 Inhaled isoproterenol, 51,52 isoetharine, 53 metaproterenol, fenoterol, 43 and albuterol 44,[46][47][48][49] all produce significant bronchodilation when administered to mechanically ventilated patients. In patients with COPD receiving mechanical ventilation, a combination of fenoterol and ipratropium bromide was shown to be more effective than ipratropium alone.…”

“…Most investigators have assessed the effect of bronchodilators on airway resistance to determine their clinical efficacy. [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] Airway resistance in mechanically ventilated patients is commonly measured by performing rapid airway occlusions at constant flow inflation. 56 In this technique, a breathhold is performed at end-inspiration by occluding the expiratory port (Fig.…”

Effect of indacaterol on arterial blood gases in patients suffering from acute exacerbation of COPD

“…Actually, some studies suggest that these agents, as a class, are of benefit in AECOPD, showing improvements in lung function and dyspnoea scores [2]. However, there is a great deal of controversy regarding the timing and optimal dose of SABAs, also considering that the duration of the bronchodilator effect of SABAs is decreased in AECOPD [3]. For this reason, several authors suggest not only using larger-than-usual doses that are sometimes necessary to relieve airway obstruction, but also to shorten the posologic interval [2,4].…”