Hyperinflation with intrinsic positive end-expiratory pressure (PEEPi) loads the respiratory muscles and causes dyspnea in obstructive lung disease. Continuous positive airway pressure (CPAP) has shown some efficacy in reducing inspiratory work and dyspnea. However, in obstructive lung disease, inspiratory work and dyspnea may be increased by additional factors that may not be affected by CPAP. Therefore, to study the effects of hyperinflation with intrinsic PEEP and CPAP in isolation, we used a mechanical analog of airway closure to increase end-expiratory lung volume in normal subjects. In five subjects in whom inspiratory work was measured, increasing end-expiratory lung volume by 1 and 2 L increased inspiratory work per breath from 0.42 +/- 0.04 J to 1.17 +/- 0.15 J (p < 0.05 compared with baseline) and 1.58 +/- 0.22 J (p < 0.05 compared with baseline and to the lesser level of hyperinflation). Although CPAP reduced work per breath and per minute to levels not significantly different from baseline, it had little effect on dyspnea. In ten subjects hyperinflated to 2.4 +/- 0.12 L above FRC, breathing could be sustained 19.5 +/- 4.5 min before quitting the load. This was increased to 26.7 +/- 5.2 min by 10 cm H2O CPAP (p = 0.052). Inspiratory dyspnea was modestly reduced by CPAP during these endurance trials. We conclude that CPAP can substantially ameliorate the respiratory work load induced by hyperinflation with intrinsic PEEP. However, the effects of CPAP on dyspnea and endurance are more limited. This suggests that the limits to breathing at high lung volumes are related to factors in addition to respiratory muscle work, and that CPAP may be of more value in reducing the work than in relieving the distress of obstructive lung disease.

Dramatic changes in the management of acute myocardial infarction (AMI) have occurred in the past decade. While previous management strategies were primarily supportive, current strategies focus on achieving and maintaining patency of the infarct-related artery restoring blood flow to jeopardized myocytes, preserving left ventricular function, and preventing recurrences and complications in addition to promoting healing. Restoration of blood flow can be achieved pharmacologically with thrombolytic agents or mechanically with percutaneous transluminal coronary angioplasty (PTCA). Early use of antiplatelet agents and anticoagulants helps maintain patency of the infarct-related arteries and prevents thromboembolic complications. Administration of beta-blockers and angiotensin enzyme inhibitors are more specific means of conserving myocardium and preserving ventricular function. Additionally, several strategies for preventing arrhythmias such as prophylactic lidocaine use and routine long-term suppression of premature ventricular contractions with antiarrhythmic drugs are no longer routinely advocated. Basically, in the era prior to the eighth decade of this century, the primary direction of the therapeutic strategy for AMI was to reduce the oxygen demands in the infarcted myocardium; whereas in the subsequent years, the emphasis shifts to improvement in oxygen delivery, via thrombolysis, PTCA, and coronary artery bypass graft surgery. These interventional changes, when added to greater sophistication in the use of drugs to reduce oxygen demands, resulted in significant lowering of myocardial mortality.

Viral infections are known to be associated with severe exacerbations of asthma in children. In contrast, there is limited data that viral infections evoke acute episodes of asthma that require emergency care in adults. To determine the role of viral infections in exacerbations of asthma in adults, we examined 33 patients who presented to the emergency room with 35 exacerbations of asthma between September 1990 and March 1991 for the presence of a viral infection. A nasal swab was obtained for virus isolation by culture and rapid antigen detection by fluorescent staining. In 16 patients, serum was collected at initial presentation and 3 to 4 weeks later for acute and convalescent viral antibody titers. All patients had acute episodes of asthma ascertained by medical history and physical examination. About 56% of the patients with asthma exacerbations had symptoms suggestive of viral illness. Rapid antigen detection and viral cultures for influenza A and B, parainfluenza-1, 2, 3, respiratory syncytial virus, adenovirus, and rhinovirus were negative on all patients. Likewise, in all 16 patients tested, acute and convalescent serologic studies did not show a significant rise in titer by complement fixation test. Thus, despite symptoms consistent with viral infection, viral pathogens could not be shown by current virologic techniques. This study suggests that viral infection may not be as prevalent a precipitate of asthma in adults requiring emergency room treatment as is generally thought.

Three cases of rapidly reversible severe myocardial depression are described in patients with status asthmaticus. Initial echocardiograms obtained within 1 day of hospital admission revealed global left ventricular hypokinesis with ejection fractions of 11 to 34%. Follow-up echocardiograms obtained only 3 to 8 days later revealed marked improvement of left ventricular function. Possible mechanisms responsible for the observed rapidly reversible myocardial depression and the clinical implications of this finding are discussed.

Until recently, it had not been recognized that predictions regarding the number of sinus beats interposed between two consecutive parasystolic beats could be made. In a case of perfect, pure parasystole resulting from unintentional fixed rate ventricular pacing, the following was observed: there were consistently three different values (0,2,3) for the number of interposed sinus beats; only one of these values was odd, and the sum of the two smaller values was one less than the larger value. Our findings, which are in keeping with those obtained in an mathematical model, may be of additional help in the diagnosis of this elusive arrhythmia.

We have performed a study assessing the prevalence of sleep-disordered breathing in a large US trucking company using a validated portable monitor (MESAM-4) and a validated symptom questionnaire. Three hundred eighty-eight drivers with a mean age of 36 years filled out the questionnaire. One hundred fifty-nine drivers with a mean age of 35 years spent the night at the terminal hub where they underwent monitoring for identification of sleep-disordered breathing. The drivers also had blood pressure recorded while awake, seated, and after 15 min of quiet rest. Seventy-eight percent of the drivers had an oxygen desaturation index (ODI) > or = 5 per hour of sleep; 10% had an ODI > or = 30 per hour of sleep. There was a significant difference in the body mass index (BMI) between drivers with ODI < 5 and drivers with ODI > or = 5 (25.7 +/- 6.0 kg/m2 in drivers with ODI < 5 vs 29.0 +/- 6.3 kg/m2 in drivers with ODI > or = 5, p < 0.001). Sixteen percent of all drivers tested were hypertensive. Twelve percent were unaware of their hypertension. Hypertensive drivers were significantly more overweight (p < 0.0001), slept more restlessly (p < 0.04), took more naps (p < 0.03), and woke up more frequently during the night (p < 0.005). About 20% of drivers presented symptoms indicating very regular sleep disturbances. Drivers who had been with the company for more than 1 year were more likely to present daytime fatigue, daytime tiredness, unrestorative sleep, hypertension, and higher BMI. Long-haul truck drivers have very irregular sleep/wake schedules and a high prevalence of sleep-disordered breathing. Chronic sleep/wake disruption and partial, prolonged sleep deprivation may worsen sleep-disordered breathing. This combination of problems may impact significantly on the daytime alertness of truckers.

We tested the hypothesis that a distractive stimulus, such as music, introduced during exercise can reduce perception of respiratory effort at any given level of exercise, whereas sensory deprivation increases effort perception. Thirty-six patients with moderate COPD participated in four sessions of symptom-limited exercise. The first session familiarized the subject with the protocol. The other sessions were performed under partial visual isolation while listening to music (M), or to grey noise (GN), or in silence (SIL), presented in randomized order. Subjects graded their respiratory effort using the Borg rating of perceived exertion (RPE) scale. Total exercise time (EXT) and external work (WT) were objective indices of exercise tolerance. EXT was 22% longer with M than with either GN or SIL (p < 0.001), and WT was 44% and 53% greater with M than with GN or SIL, respectively (p < 0.001). These increases occurred at a heart rate that was only a few beats higher than during GN or SIL (104 +/- 3 bpm for M and 101 +/- 3 bpm for GN and SIL), a minimal difference that was statistically significant (p < 0.001). At every level of exercise, perceived exertion with M was lower than for either GN or SIL (p < 0.001). Although the respective RPE was higher for SIL than for GN (p < 0.01) at every level of exercise, WT and EXT were no different. These data indicate that perceived effort can be significantly influenced by external factors. This in turn suggests that the use of distractive stimuli during exercise training programs with patients with COPD may significantly decrease perceived symptoms of respiratory discomfort, thus allowing the patient to exercise to a higher intensity, and potentially achieving more effective exercise reconditioning training.

Relatively little is known about the influence of inhaled corticosteroids on general well-being (quality of life) in patients with asthma or COPD. In a 4-year prospective controlled study, we examined the influence of beclomethasone dipropionate (BDP), 400 micrograms, two times daily, on quality of life in 56 patients with asthma or COPD in comparison with the effects of BDP on symptoms and lung function. During the first 2 years, patients received only bronchodilator therapy with salbutamol or ipratropium bromide. During the third and fourth years, additional treatment with BDP was given. Fifty-six patients (28 with asthma, 28 with COPD) with an annual decline in the forced expiratory volume in 1 s (FEV1) of at least 80 mL/yr in combination with at least two exacerbations per year during bronchodilator therapy alone participated. Quality of life was assessed at the start and after 2 and 4 years by means of the Inventory of Subjective Health (ISH) and the Nottingham Health Profile (NHP). Although BDP significantly improved the course of lung function (FEV1)(p < 0.0001), it did not improve the ISH score or the six dimensions of the NHP neither in asthma nor in COPD. Beclomethasone dipropionate temporarily decreased respiratory symptoms during months 4 to 6 of BDP treatment in patients with asthma (p < 0.01) and during months 7 to 12 in patients with COPD (p < 0.05). A weak correlation was found both cross-sectionally and longitudinally between (change in) symptoms and quality of life on the one hand, and the (change in) FEV1 on the other. It was concluded that BDP did not improve the general well-being of patients with asthma or COPD as measured by these generic health instruments. However, BDP significantly improved the course of lung function and temporarily decreased the severity of symptoms. It seems probable that changes in quality of life would have been better detected by use of a disease-specific health instrument. Such an instrument was not available at the start of the study. Another possible explanation for these observations is that patients soon get used to different levels of lung function and learn to live with their disease. It is advised that disease-specific health instruments are used in future intervention studies and that quality of life is measured frequently during the early phase of the intervention, eg, once every month.

This study was designed to determine whether ambulatory electrocardiography in patients with recent stroke would lead to a change in clinical management or outcome and to express these findings in terms of cost benefit. A prospective, consecutive sample of patients (n = 100) with recent stroke referred from the neurology or medical services for ambulatory electrocardiography was identified. Ambulatory electrocardiograms were reviewed to identify patients with potentially important bradyarrhythmias, tachyarrhythmias, or atrial fibrillation. Patients were then followed up without interference with ongoing care to determine whether these findings led to changes in clinical management that might influence patient outcome. Of the 100 patients, 16 had an index "important" arrhythmia. No significant bradyarrhythmias were noted. Nonsustained ventricular tachycardia (> or = 6 complexes) in two patients and supraventricular tachycardia (> or = 10 complexes) in seven patients did not lead to management changes. Four patients had a history of atrial fibrillation who were in sinus rhythm; anticoagulation had been addressed in three; the fourth patient died before the issue could be addressed. Of three patients in atrial fibrillation, there was a history of atrial fibrillation and a decision regarding anticoagulation in each before monitoring. The cost of these 100 ambulatory electrocardiograms was about $55,000. In conclusion, these findings do not support the routine use of ambulatory electrocardiography in the evaluation of patients with stroke.

Pulmonary infection and tumor in the AIDS population has a variable clinical and radiographic presentation. The association between the radiographic presentation of pulmonary tuberculosis and CD4 T lymphocyte count in the HIV-infected patient is investigated in order to provide an empirical approach for early diagnosis, treatment, and isolation of infected subjects.