The effect of aminophylline on the force-length characteristics of the diaphragm

Pulmonary outcomes following specialized respiratory management for acute cervical spinal cord injury: a retrospective analysis

Study Design

Retrospective analysis.

Objectives

To identify multivariate interactions of respiratory function that are sensitive to spinal cord injury level and pharmacological treatment to promote strategies that increases successful liberation from mechanical ventilation.

Setting

United States regional spinal cord injury (SCI) treatment center.

Methods

Retrospective chart review of patients consecutively admitted to Santa Clara Valley Medical Center (SCVMC) between May 2013 and December 2014 for ventilator weaning with C1-5 AIS A or B SCI, < 3 months from injury and who had a tracheostomy in place. A non-linear, categorical principal component analysis (NL-PCA) was performed to test the multivariate interaction of respiratory outcomes from patients (N=36) being weaned off ventilator support after acute SCI with (N=15) or without (N=21) theophylline treatment.

Results

36 patients met inclusion criteria (2 C1, 5 C2, 11 C3, 14 C4, 4 C5). The NL-PCA returned 3 independent components that accounted for 95% of the variance in the dataset. Multivariate general linear models (GLM) hypothesis tests revealed a significant syndromic interaction between theophylline treatment and SCI level (Wilks’ Lambda, p=0.028, F(12,64)=2.116, η2=0.256, 1−β=0.838), with post-hoc testing demonstrating a significant interaction on PC1, explained by a positive correlation between improved forced vital capacity and time it took to reach 16 hours of ventilator free breathing. Thirty-three patients (92%) achieved 16 hours ventilator-free breathing (VFB), 30 (83%) achieved 24 hours VFB.

Conclusions

We suspect that some portion of the high success rate of ventilator weaning may be attributable to theophylline use in higher cervical SCI; in addition to our aggressive regimen of high volume ventilation, medication optimization, and pulmonary toilet (positive pressure treatments and mechanical insufflation-exsufflation).

Xanthines and Phosphodiesterase Inhibitors

Theophylline is an orally acting xanthine that has been used since 1937 for the treatment of respiratory diseases including asthma and chronic obstructive pulmonary disease (COPD). However, in most treatment guidelines, xanthines have now been consigned to third-line therapy because of their narrow therapeutic window and propensity for drug-drug interactions. However, lower than conventional doses of theophylline considered to be bronchodilator are now known to have anti-inflammatory actions of relevance to the treatment of respiratory disease. The molecular mechanism(s) of action of theophylline are not well understood, but several potential targets have been suggested including non-selective inhibition of phosphodiesterases (PDE), inhibition of phosphoinositide 3-kinase, adenosine receptor antagonism and increased activity of certain histone deacetylases. Although theophylline has a narrow therapeutic window, other xanthines are in clinical use that are claimed to have a better tolerability such as doxofylline and bamifylline. Nonetheless, xanthines still play an important role in the treatment of asthma and COPD as they can show clinical benefit in patients who are refractory to glucocorticosteroid therapy, and withdrawal of xanthines from patients causes worsening of disease, even in patients taking concomitant glucocorticosteroids.More recently the orally active selective PDE4 inhibitor, roflumilast, has been introduced into clinical practice for the treatment of severe COPD on top of gold standard treatment. This drug has been shown to improve lung function in patients with severe COPD and to reduce exacerbations, but is dose limited by a range side effect, particularly gastrointestinal side effects.

Lung Injury and Bronchopulmonary Dysplasia in Newborn Infants

Bronchopulmonary dysplasia is the most common morbidity among surviving premature infants. Injury to the developing lung is the result of the interaction between a susceptible host and a number of contributing factors such as mechanical ventilation and infection. The resulting persistent impairment of pulmonary function and need for ongoing therapy are the underlying characteristics of bronchopulmonary dysplasia. Important insights into the pathogenesis of bronchopulmonary dysplasia have led to numerous therapies and preventive approaches. Although significant progress has been made, in order to further affect the incidence and severity of the disease, we need to further study (a) the genetically determined predisposing factors, (b) the relative contribution of the various pathogenetic pathways, and, most important, (c) how to best translate the knowledge gained from these studies into effective clinical approaches.

Aminophylline increases ventilation and diaphragm contractility in awake canines

Traditional theophylline bronchodilators are still used clinically, especially in COPD. However, the effect of theophyllines on ventilation and respiratory muscles remains uncertain and these effects have not been measured directly in any awake, intact mammal. We hypothesized that aminophylline in the usual therapeutic dosage range, would elicit in the awake mammal, a significant increase in ventilation, and a significant increase in costal diaphragm shortening and contractility as recorded directly from the muscle. Therefore, we studied 13 awake canines, which had been chronically implanted with fine-wire EMG electrodes and sonomicrometer crystals in the costal segment of the diaphragm. Ventilatory parameters, moving average muscle EMG activity and muscle length and shortening, were measured at baseline and with aminophylline, during resting and hypercapnic stimulated breathing. Experiments were carried out prior to administration of aminophylline (baseline), and 1.5h after loading and ongoing infusion with aminophylline. Minute ventilation, tidal volume and respiratory frequency all increased significantly with aminophylline, both during resting breathing and at equivalent levels of hypercapnic stimulated breathing. Costal diaphragm baseline muscle length was entirely unchanged with aminophylline. Costal diaphragm shortening increased significantly with aminophylline while corresponding costal diaphragm EMG activity remained constant, consistent with increased diaphragm contractility. Thus, in awake, intact mammals, aminophylline in usual therapeutic dosage elicits increased ventilation and increased contractility of respiratory muscles.

Effects of theophylline on pulmonary function in patients with traumatic tetraplegia

BACKGROUND/OBJECTIVES

To assess the effects of theophylline on pulmonary function in patients with chronic traumatic tetraplegia, we conducted a double-blind placebo-controlled crossover study in 10 patients.

METHODS

The patients (age: 41 +/- 3 years; time from injury: 16 +/- 3 years; neurological levels: C3 to C7-T1) were randomized to receive oral theophylline or placebo for 6 weeks. After 2 months of washout, the patients received the medication not taken in the first trial for an additional 6 weeks. We measured lung volumes, expiratory flow rates, maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP) at both baseline and at the end of each treatment arm. Theophylline blood serum assays were measured during the first week of the treatment and on the day of respiratory measurements.

RESULTS

Mean theophylline level on the day of treatment completion was 12.6 +/- 1.4 microg/mL. In analyzing the data from the group of 10 patients, the percent changes from baseline in total lung capacity, forced vital capacity, forced expiratory volume at 1 second, MIP, and MEP did not differ significantly between the two treatment arms (P > 0.05 in all).

CONCLUSION

These data show that in this small group of 10 subjects with chronic tetraplegia, administration of oral theophylline did not improve pulmonary function.

Intravenous aminophylline for acute severe asthma in children over two years receiving inhaled bronchodilators

BACKGROUND

Since the advent of inhaled beta2-agonists, anticholinergic agents and glucocorticoids, the role of aminophylline in paediatric acute asthma has become less clear. There remains some consensus that it is beneficial in children with acute severe asthma, receiving maximised therapy (oxygen, inhaled bronchodilators, and glucocorticoids).

OBJECTIVES

To determine if the addition of intravenous aminophylline produces a beneficial effect in children with acute severe asthma receiving conventional therapy.

SEARCH STRATEGY

The Cochrane Airways Group register of trials was used to identify relevant studies. The latest search was carried out in December 2004

SELECTION CRITERIA

Randomised-controlled trials comparing intravenous aminophylline with placebo in addition to usual care in children met the inclusion criteria.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed studies and extracted data. Disagreement in the selection of trials was resolved by consensus. Attempts were made to contact authors to verify accuracy of data.

MAIN RESULTS

Seven trials met the inclusion criteria (380 participants). Methodological quality was high. All studies recruited children with acute severe asthma and requiring hospital admission. Six studies sought participants who were unresponsive to nebulised short-acting beta-agonist and administered systemic steroids to study participants. In two studies where some children were able to perform spirometry, baseline FEV1 was between 35 and 45% predicted. The addition of aminophylline to steroids and beta2-agonist significantly improved FEV1% predicted over placebo at 6-8 hours, 12-18 hours and 24 hours. Aminophylline led to a greater improvement in PEF% predicted over placebo at 12-18 hours. There was no significant difference in length of hospital stay, symptoms, frequency of nebulsations and mechanical ventilation rates. There were insufficient data to permit aggregation for oxygenation and duration of supplemental oxygen therapy. Aminophylline led to a three-fold increase in the risk of vomiting. There was no significant difference between treatment groups with regard to hypokalaemia, headaches, tremour, seizures, arrhythmias and deaths.

AUTHORS' CONCLUSIONS

In children with a severe asthma exacerbation, the addition of intravenous aminophylline to beta2-agonists and glucocorticoids (with or without anticholinergics) improves lung function within 6 hours of treatment. However there is no apparent reduction in symptoms, number of nebulised treatment and length of hospital stay. There is insufficient evidence to assess the impact on oxygenation, PICU admission and mechanical ventilation. Aminophylline is associated with a significant increased risk of vomiting.

Effect of acute aminophylline administration on diaphragm function in high cervical tetraplegia: a case report

Theophylline has been shown to have beneficial effects on phrenic nerve and diaphragm activation. This case report involves a C5-C6 chronic tetraplegic patient with acute respiratory failure and ventilator dependence. IV aminophylline was administered in increasing doses (2 mg/kg, 4 mg/kg, and 6 mg/kg) over the course of 1 day. Diaphragm surface electromyography (sEMG), measures of respiration (tidal volume, minute ventilation, and frequency), and serum theophylline levels were captured. Diaphragm sEMG activity increased by a maximum of 50% at therapeutic levels. The rapid shallow breathing index dropped from 112 to 86. The subject was successfully weaned from ventilatory support. We conclude that administration of aminophylline facilitated weaning from ventilatory support in this tetraplegic patient.

Intravenous aminophylline for acute severe asthma in children over 2 years using inhaled bronchodilators

BACKGROUND

Intravenous aminophylline was the bronchodilator of choice for many years until supplanted by more effective bronchodilators in the treatment of acute paediatric asthma. Recently there has been renewed interest in this therapy for children with acute severe asthma.

OBJECTIVES

To determine whether addition of intravenous aminophylline produces a beneficial effect in children with acute severe asthma receiving oxygen, maximised inhaled bronchodilators and oral/intravenous glucocorticoids.

SEARCH STRATEGY

The Cochrane Airways Group register of trials (based on MEDLINE, EMBASE, CINAHL and hand searched respiratory journals) and reference lists of relevant articles were used to identify relevant studies. The latest search was carried out in October 2000.

SELECTION CRITERIA

Only randomised-controlled trials comparing intravenous aminophylline with placebo in children treated with inhaled bronchodilators and systemic glucocorticoids for acute asthma were considered for this review.

DATA COLLECTION AND ANALYSIS

Full text of 35 trials were anonymized for author, date and publication and two blinded independent reviewers selected eligible studies for inclusion. Disagreement was resolved through consensus. Seven trials met the inclusion criteria. Attempts were made to contact authors to verify accuracy. Results were reported as weighted mean differences (WMD) or relative risk (RR) with 95% confidential intervals (CI).

MAIN RESULTS

Patients in these trials were predominantly school-aged children hospitalised for acute severe asthma with a baseline FEV1 at 35-40% of predicted and/or a baseline Pulmonary Index of 6-7. Aminophylline significantly improved percentage predicted FEV1 by 6 - 8 hours (WMD 8.4%; 95% CI: 0.82, 15.92%). The effect was maintained for 24 hours. Improvements were also seen in symptom scores at 6-8 hours (WMD= -0.71; 95% CI: -0.82,-0.60). There was no reduction in hospital stay or in number of nebulisers required. Vomiting was more likely with aminophylline therapy (Relative Risk = 3.69; 95% CI: 2.15, 6.33).

REVIEWER'S CONCLUSIONS

Addition of intravenous aminophylline should be considered early in the treatment of children hospitalised with acute severe asthma with sub optimal response to the initial inhaled bronchodilator therapy. Although the improvement is sustained for 24 hours, there is no apparent reduction in length of hospital stay or number of inhaled beta2-agonists nebulisations. Treatment with aminophylline is associated with an increased risk of vomiting.

Aminophylline modulation of the mouse respiratory network changes during postnatal maturation

Aminophylline is a respiratory stimulant commonly used for the treatment of central apnea. Experiences from clinical practice, however, revealed that aminophylline is not reliably effective in preterm infants, whereas it is normally effective in infants and mature patients. In an established animal model for postnatal development of respiratory control mechanisms, we therefore examined the hypothesis that the clinical observations reflect a developmental change in the sensitivity of the central respiratory network to methylxanthines. The medullary respiratory network was isolated at different postnatal ages (postnatal days 1-13; P1-P13) in a transverse mouse brain stem slice preparation. This preparation contains the pre-Bötzinger complex (PBC), a region that is critical for generation of respiratory rhythm. Spontaneous rhythmic respiratory activity was recorded from the hypoglossal (XII) rootlets and from neurons in the PBC by using the whole cell patch clamp technique. Bath-applied aminophylline [20 microM] increased the frequency (+41%) in neonatal animals (P1-P6) without affecting the amplitude of respiratory burst activity in XII rootlets. The same concentration of aminophylline did not have any significant effect on the frequency of respiratory XII bursts but increased the amplitude (+31%) in juvenile animals (P7-P13). In the same age group, aminophylline also augmented the amplitude and the duration of respiratory synaptic drive currents in respiratory PBC neurons. The data demonstrate that augmentation of the respiratory output is due to direct enhancement of central respiratory network activity and increase of synaptic drive of hypoglossal motoneurons in juvenile, but not neonatal, animals. This indicates a developmental change in the efficacy of aminophylline to reinforce central respiratory network activity. Therefore, we believe that the variable success in treating respiratory disturbances in premature infants reflects maturational changes in the expression of receptors and/or intracellular signal pathways in the central respiratory network.

Maximal airway pressures during crying in healthy preterm and term neonates

Respiratory muscle strength can be assessed by measurement of maximal inspiratory (PIMAX) and maximal expiratory pressure (P(EMAX)) during crying. There are, however, relatively few data on P(IMAX) and P(EMAX) in infancy, particularly from those born preterm. Our aim was to investigate which factors influenced P(IMAX) and P(EMAX) in preterm and term infants. Forty infants, median gestational age 37 weeks (range 26-43) and birthweight 2.579 kg (range 0.956-5.180) were studied at a postconceptional age (PCA) of 38 weeks (range 32-44). None had respiratory problems. A facemask was placed firmly over the infant's mouth and nose and the infant studied during spontaneous crying. A pneumotachograph fitted snugly into the facemask and from a sideport airway pressure changes were measured. During crying, the distal end of the pneumotachograph was occluded for five breaths and at least three separate occlusions were made. The highest P(EMAX) value sustained for at least 1 s and the highest peak inspiratory pressure P(IMAX) were recorded. The mean P(IMAX) and P(EMAX) were higher in the term compared to the preterm infants (70 cmH2O +/-S.D. 19 versus 58 cmH2O +/-S.D. 17 P(IMAX) and 53 cmH2O +/-S.D. 13 versus 44 cmH2O +/-S.D. 19 P(EMAX), P< 0.05). Both P(IMAX) and P(EMAX) related significantly with postconceptional age, gestational age and weight, but not postnatal age. Stepwise regression analysis demonstrated P(IMAX) related independently with PCA and P(EMAX) with weight. These results suggest respiratory muscle strength is influenced by maturation at birth.

Skeletal muscle abnormalities in patients with COPD: contribution to exercise intolerance

Exercise intolerance in COPD patients appears to be in part because of skeletal muscle dysfunction. Studies using biopsy techniques and magnetic resonance spectroscopy have demonstrated changes in enzyme activities and metabolism that indicate reduced oxidative capacity in the peripheral muscles of these patients. Regarding the respiratory muscles, the biochemical characteristics have been studied in only a few works and the results seem to depend on the specific muscle group studied. Several factors, such as hypoxemia, nutritional status, pharmacological treatment, and deconditioning, may be responsible for these skeletal muscle abnormalities. This brief review describes the changes in peripheral and respiratory muscles in COPD patients based on data from the literature. The causes of these muscle abnormalities, their contribution to exercise intolerance, and the effects of training are then discussed. We conclude with suggested directions for future investigation using contemporary noninvasive technologies.