Effects of dihydrocodeine, alcohol, and caffeine on breathlessness and exercise tolerance in patients with chronic obstructive lung disease and normal blood gases

Bronchodilator effects of caffeine in coffee. A dose-response study of asthmatic subjects

Although caffeine is a universal drug and has multiple pharmacologic and physiologic actions in man, there are surprisingly few objective data about its effect on pulmonary function. We conducted a short-term, double-blind, randomized crossover study in nine asthmatic adults who ingested decaffeinated coffee containing varying amounts of added caffeine (mean of 0.2,2.5,5.6, and 7.2 mg/kg of body weight) on different days. The subjects also ingested decaffeinated coffee and aminophylline (200 mg) on a separate day of study. Baseline and post-drug determinations of serum levels of caffeine and theophylline, forced expired volume and flow, specific airway conductance (Gaw/VL), vital signs, and reported symptoms were obtained. Peak increases in serum caffeine concentrations (mean, 12.4 micrograms/ml +/- 1.5 micrograms/ml) occurred 45 minutes following the highest dose of caffeine (7.2 mg/kg), whereas the peak theophylline level (mean 3.8 micrograms/ml +/- 0.4 micrograms/ml) occurred 90 minutes following oral administration of aminophylline (mean theophylline, 2.6 mg/kg). Comparable peak increases in the forced expiratory volume in one second (FEV1), the forced expiratory flow during the middle half of the forced vital capacity (FEF25-75%), and Gaw/VL occurred at 120 minutes following aminophylline and the highest dose of caffeine, indicating that caffeine is an effective bronchodilator but is only 40 percent as active as an equivalent molar dose of theophylline. Regression analysis revealed statistically significant dose-response relationships between peak increases in serum caffeine concentrations and increases in FEV1, FEF25-75%, and Gaw/VL from baseline values. These findings have diagnostic and therapeutic implications regarding the use of caffeine prior to tests of pulmonary function and as a dietary agent, alone or in combination with theophylline.

Caffeine and endurance performance

The belief among athletes that caffeine is an ergogenic aid is common, and several governing bodies of sport have barred use of the drug during competition. At the cellular level, caffeine has been implicated to affect the translocation of calcium in muscle, promote an increase in cellular levels of cyclic AMP and cause a blockade of adenosine receptors in the central nervous system. The general systemic effect of caffeine is to cause central nervous system arousal, mobilisation of free fatty acids and other metabolites, and possibly enhance the contractile status of muscle. At present, the scientific community remains divided as to whether caffeine ingestion will indeed produce an ergogenic effect upon sport performance. Some evidence suggests that caffeine may improve performance in events relying upon strength and power; however, the lack of in vivo research in humans makes it difficult to form firm conclusions. In addition, reports concerning caffeine's effect on VO2max and performance during incremental exercise are not in agreement. On the other hand, recent studies suggest that caffeine might indeed have ergogenic potential in endurance events (e.g. marathon running). It is hypothesised that the mechanism behind these findings is related to the increased availability of free fatty acids for muscle metabolism which has a glycogen-sparing effect.

A rationale for training respiratory muscles

In planning a training programme for respiratory muscles several factors should be considered: establish the objective according to the patient's pathology, provide an adequate stimulus (both in intensity and quality), define if the goal is to increase coordination, strength, endurance, or all three. Several respiratory muscle conditioning plans have been used, mostly derived from three major protocols: sustained hyperventilation, resistive breathing, and manipulations of the breathing pattern. They have proved to be effective in quadriplegia, cystic fibrosis and to some extent in COPD patients. Respiratory muscle recovery and training in patients with respiratory failure is discussed.

Effects of codeine on the respiratory responses to exercise in healthy subjects

In six healthy subjects, respiration and the sensation of breathlessness were assessed during submaximal exercise and the subsequent recovery. The overall responses were expressed by the relationship of breathlessness to minute volume. Because of the high subjective component in the assessments, validation of the method in these particular subjects was an integral part of the study. The relationship of breathlessness to ventilation during identical periods of exercise was highly reproducible and sensitivity was demonstrated by an alteration in this relationship in the presence of an inspiratory resistance. Codeine at a dose of 60 mg by mouth was compared with placebo, each treatment being given on two occasions. The study was conducted in a double-blind fashion with randomization of the order of treatments. Codeine at this dose allowed higher levels of carbon dioxide to be tolerated during breath-holding; oxygen uptakes at rest and during exercise were unaffected. Ventilation and breathlessness at the end of exercise were each slightly but significantly reduced by codeine but the relationship between breathlessness and ventilation was not changed. Codeine did not prevent detection of an inspiratory resistance.

Dihydrocodeine for breathlessness in "pink puffers"

Eighteen patients with severe breathlessness due to chronic airflow obstruction completed a randomised placebo controlled double blind cross over trial of the effect of dihydrocodeine 15 mg on breathlessness, disability, and exercise tolerance. There were three periods of one week each. During the first two weeks patients were instructed to take dihydrocodeine 15 mg or placebo 30 minutes before exercise as required up to three times daily. During the third week patients received either dihydrocodeine or placebo on alternate days. During the weekly dihydrocodeine period patients were more mobile (pedometer distance increased by 16.8%) and less breathless (daily visual analogue score of breathlessness reduced by 17.8%). This benefit was confirmed by treadmill testing at the end of each treatment period, when maximum distance walked was 16.5% higher and breathlessness 11.8% less after dihydrocodeine compared with placebo. Similar benefit in breathlessness occurred during alternate day treatment. No adverse effects were encountered. Dihydrocodeine 15 mg 30 minutes before exercise offers appreciable benefit to patients with severe breathlessness due to chronic airflow obstruction.

Breathlessness and psychiatric morbidity in chronic bronchitis and emphysema: a study of psychotherapeutic management

This paper describes a study of the outcome of psychotherapy with patients disabled by chronic obstructive airways disease giving rise to dyspnoea. Forty-three men and 22 women with severe COAD were randomly allocated for 8 weeks to one of three types of psychotherapy or to an untreated control group, and were followed up six months later. The group treated by a medical nurse without training in psychotherapy experienced sustained relief of dyspnoea but tended to undergo less psychodynamic change; psychiatric symptoms were reduced in those receiving supportive, but not analytical, psychotherapy. The psychosomatic mechanisms involved and the implications for medical and nursing practice and for liaison psychotherapy are discussed.

Are "pink puffers" more breathless than "blue bloaters"?

Breathlessness, disability, and exercise tolerance were assessed in 26 patients with severe chronic airflow limitation (forced expiratory volume in one second (FEV1) less than or equal to 1 litre) divided into two groups--15 patients who were normocapnic (pressure of arterial carbon dioxide (Paco2) less than 5.5 kPa (less than 41.4 mm Hg)), and 11 patients who were hypercapnic (Paco2 greater than 6 kPa (greater than than 45.1 mm Hg)). The two groups were well matched for spirometric values (FEV1 0.59 1 and 0.62 1, respectively). All of the hypercapnic patients could improve blood gas tensions towards normal by hyperventilation. There were no significant differences in visual analogue scores of breathlessness during treadmill exercise, disability (oxygen-cost diagram, dyspnoea grade), or exercise tolerance (six-minute walk, maximal consumption of oxygen during bicycle ergometry, distance walked to exhaustion in progressive treadmill test). The findings show that the "fight" to maintain normal blood gas tensions in the face of severe airflow limitation does not have an appreciable cost in terms of disability.