Precision and accuracy of self-measured peak expiratory flow rates in chronic obstructive pulmonary disease.

BACKGROUND: The precision and accuracy of self-measured peak expiratory flow rates (PEFR) have not been determined for patients with chronic obstructive pulmonary disease (COPD). METHODS: Twenty-eight male veterans recorded their PEFR twice daily, before and after bronchodilators, for 6 months. Spirometry was also done in the pulmonary function laboratory up to 11 times per patient during the observation period. A 4-week "baseline" was identified for each patient. Baseline coefficients of variation (CV) were calculated for the morning (AM) and evening (PM) PEFR, before (PRE) and after (POST) bronchodilators. RESULTS: The baseline CVs for AMPRE, AMPOST, PMPRE and PMPOST were 14.9+/-6.9%, 12.6+/-5.6%, 14.9+/-4.8%, and 11.2+/-6.0%, respectively. There were strong correlations between self-measured PEFR and values obtained in the pulmonary function laboratory on the same day. CONCLUSIONS: Self-measured PFFRs are reasonably precise and accurate in patients with COPD.

A multivariate model for predicting respiratory status in patients with chronic obstructive pulmonary disease.

OBJECTIVE: To develop and validate a multivariate model for predicting respiratory status in patients with advanced chronic obstructive pulmonary disease (COPD). DESIGN: Prospective, double-blind study of peak flow monitoring. SETTING: Albuquerque Veterans Affairs Medical Center. PATIENTS: Male veterans with an irreversible component of airflow obstruction on baseline pulmonary function tests. MEASUREMENTS: This study was conducted between January 1995 and May 1996. At entry, subjects were instructed in the use of the modified Medical Research Council Dyspnea Scale and a mini-Wright peak flow meter equipped with electronic storage. For the next 6 months, they recorded their dyspnea scores once daily and peak expiratory flow rates twice daily, before and after the use of bronchodilators. Patients were blinded to their peak expiratory flow rates, and medical care was provided in the customary manner. Readings were aggregated into 7-day sampling intervals, and interval means were calculated for dyspnea score and peak expiratory flow rate parameters. Intervals from all subjects were then pooled and randomized to separate groups for model development (training set) and validation (test set). In the training set, logistic regression was used to identify variables that predicted future respiratory status. The dependent variable was the log odds that the subject would attain his highest level of dyspnea in the next 7 days. The final model was used to stratify the test set into "high-risk" and "low-risk" categories. The analysis was repeated for 3-day intervals. MAIN RESULTS: Of the 40 patients considered eligible for study, 8 declined to participate, 4 could not master the technique of peak flow monitoring, and 6 had no fluctuations in their dyspnea level. The remaining 22 subjects form the basis of this report. Fourteen (64%) of the latter completed the 6-month protocol. Data from the 8 who were dropped or died were included up to the point of withdrawal. For 7-day forecasts, mean dyspnea score and mean daily prebronchodilator peak expiratory flow rate were identified as predictor variables. The adjusted odds ratio (OR) for mean dyspnea score was 2.71 (95% confidence interval [CI] 1.79, 4.12) per unit. For mean prebronchodilator peak expiratory flow rate, it was 1.05 (95% CI 1.01, 1.09) per percentage predicted. For 3-day forecasts, the model was composed of mean dyspnea score and mean daily bronchodilator response. The ORs for these terms were 2.66 (95% CI 2.06, 3.44) per unit and 0.980 (95% CI 0.962, 0.998) per percentage of improvement over baseline, respectively. For a given level of dyspnea, higher pre-bronchodilator peak expiratory flow rate and lower bronchodilator response were poor prognostic findings. When the models were applied to the test sets, "high-risk" intervals were 4 times more likely to be followed by maximal symptoms than "low-risk" intervals. CONCLUSIONS: Dyspnea scores and certain peak expiratory flow rate parameters are independent predictors of respiratory status in patients with COPD. However, our results suggest that monitoring is of little benefit except in patients with the most advanced form of this disease, and its contribution to their management is modest at best.

Patient compliance with peak flow monitoring in chronic obstructive pulmonary disease.

BACKGROUND: The factors affecting patient compliance with peak flow monitoring in advanced chronic obstructive pulmonary disease (COPD) were examined using a prospective, blinded study. METHODS: Twenty-eight male veterans were instructed in the use of an electronic, hand-held peak flow meter and the modified Medical Research Council dyspnea scale. They then entered a 6-month monitoring phase in which they recorded a dyspnea score once daily and peak expiratory flow rates twice daily, before and after bronchodilator use. The meter displays were disabled so that the patients were blinded to their values. Medical care was provided in the customary manner. Compliance was defined as the ratio of recorded values to all values specified by the protocol, exclusive of those missing due to circumstances beyond the patient's control. RESULTS: Of 40 patients who met the entry criteria for this study, 8 refused to participate and 4 could not master the technique. The remaining 28 patients were enrolled. Overall, 25 (63% of those eligible) adhered to the protocol until its conclusion or until they became unable to comply because of medical or social problems. Compliance was 89.8+/-15.0%. Of those followed for longer than 150 days, linear regression showed that only one patient had a decline in compliance over time (r=0.84, P=0.04). Compliance was lower in the afternoons (P < 0.001) and on days with higher dyspnea scores (P < 0.001). No other clinical factors had an effect on patient measurements. CONCLUSIONS: A substantial proportion of patients with advanced COPD can be trained in the technique of peak flow monitoring. Compliance is high if patients are enrolled in a long-term, structured program of supervision and periodic retraining.

Time course of respiratory decompensation in chronic obstructive pulmonary disease: a prospective, double-blind study of peak flow changes prior to emergency department visits.

The aim of this study was to look at changes in peak expiratory flow rates (PEFR) prior to emergency department visits for decompensated chronic obstructive pulmonary disease (COPD). It was designed as a prospective, double-blind study at the Albuquerque Veterans Affairs Medical Center. Twelve patients with an irreversible component of airflow obstruction on pulmonary function tests were assessed. At entry, all subjects were instructed in the use of a mini-Wright peak flow meter with electronic data storage. They then entered a 6-month monitoring phase in which they recorded PEFR twice daily, before and after bronchodilators. The meter displays were disabled so that the patients and their physicians were blinded to all values. Medical care was provided in the customary manner. Patients were considered to have respiratory decompensation if they required treatment for airflow obstruction in the Emergency Department (ED) and no other causes of dyspnea could be identified. Simple linear regression was used to model changes in PEFR over time. The 12 subjects had 22 episodes of respiratory decompensation during 1741 patient-days of observation. Two episodes could not be analysed because of missing values. Ten episodes in seven subjects were characterized by a significant linear decline in at least one peak flow parameter prior to presentation. The mean rates of change for the four daily parameters varied from 0.22% to 0.27% predicted per day (or 1.19 to 1.44 1 min-1 day-1). The average decrement in these parameters ranged from 30.0 to 33.8 1 min-1 (or 18.6%-25.9% of their baseline values). No temporal trends were found for the 10 episodes occurring in the other five subjects. We concluded that respiratory decompensation is characterized by a gradual decline in PEFR in about half of cases. Future studies should be done to elucidate the mechanisms of respiratory distress in the other cases.

A comparison of the effects of nifedipine and verapamil on exercise performance in patients with mild to moderate hypertension.

Twenty-four patients completed a double-blind, randomized clinical trial comparing the effects of nifedipine GITS (N) and verapamil SR (V) on blood pressure (BP) control and exercise performance. After a 2-week placebo phase, all subjects had measurements of VO2max, maximal workload, and endurance time. They were then randomized to either N (30 to 90 mg/day) or V (240 to 480 mg/day) and retested when BPs had stabilized. At rest, N lowered systolic (S) BP by 12 mm Hg (P = .02 compared to baseline) and diastolic (D) BP by 11 mm Hg (P = .001). V lowered SBP by 8 mm Hg (P = .013) and DBP by 11 mm Hg (P = .002). Neither drug affected resting heart rate. V significantly decreased resting epinephrine (P = .05) and there was a tendency for V to reduce norepinephrine (P = .07) and dopamine (P = .08). N tended to increase plasma renin activity (P = .07). During graded cycle ergometry N, compared with placebo, significantly lowered DBP at all exercise levels (P = .011), but had no significant effect on heart rate (HR), SBP, or heart rate pressure product (HRPP). Pulse pressure (PP) was significantly increased (P = .045), which was most noticeable at high exercise levels. Compared with placebo, V caused a marked reduction of exercise HR (P < .001), which was more pronounced at high levels, SBP (P = .004), DBP (P = .004), mean arterial pressure (MAP) (P = .001), and HRPP (P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

A multivariate model for the prediction of relapse after outpatient treatment of decompensated chronic obstructive pulmonary disease.

PURPOSE: To develop and validate a multivariate model for predicting relapses after treatment of decompensated chronic obstructive pulmonary disease in an emergency department. METHODS: A 5-year survey was conducted, including training and validation periods. Stepwise logistic regression was used to develop a multivariate predictive model using clinical data obtained at the time of each visit. A relapse was defined as an unscheduled return to the emergency department within 48 hours. SITE: The study was conducted in the emergency department of the Albuquerque (New Mexico) Veterans Affairs Medical Center. SUBJECTS: The subjects were 289 patients with documented chronic obstructive pulmonary disease. MEASUREMENTS AND MAIN RESULTS: During the first 3 years, there were 705 visits in which the patient was treated and released from the emergency department. Relapse occurred 82 times (11.6%). Logistic regression showed that the following variables had an effect on the risk of relapse: the relapse rate for previous visits, a previous visit within 7 days, long-term home oxygen therapy, the number of doses of nebulized bronchodilators, the administration of aminophylline, and the use of antibiotics and prednisone at the time of discharge from the emergency department. During the next 2 years, the 48-hour relapse rate was 9.9% (47 of 476 discharges). When the model was fitted to these data, all of the original variables contributed to the prediction of relapse except antibiotic use and long-term home oxygen therapy. The logistic model was used to categorize each visit during the validation phase. The relapse rate for "high-risk" visits was significantly higher than that for "low-risk" visits (18.4% vs 6.1%). The method identified 57.4% of visits that ended in relapse at 48 hours. CONCLUSIONS: A multivariate model can be used to identify patients with a poor prognosis after the outpatient treatment of decompensated chronic obstructive pulmonary disease.

A multivariate model for predicting hospital admissions for patients with decompensated chronic obstructive pulmonary disease.

PURPOSE: To develop a method for predicting hospital admissions for patients with decompensated chronic obstructive pulmonary disease treated in an emergency department. METHODS: A 4-year survey including training and validation periods was conducted. Stepwise logistic regression was used to develop a multivariate model using information from the patient's previous visits and results of baseline pulmonary function tests. MEASUREMENTS AND MAIN RESULTS: During the first 2 years, there were 693 visits to the emergency department for decompensated chronic obstructive pulmonary disease. The patient was admitted to the hospital on 210 occasions (30.3%). Logistic regression showed that the probability of admission was related to the following: the admission and relapse rates for previous visits, the proportion of previous discharges from the emergency department in which "conservative therapy" was given, the highest baseline post-bronchodilator forced expiratory volume in 1 second within 3 years of entry, and the highest baseline pre-bronchodilator forced expiratory volume in 1 second-vital capacity ratio. A relapse was defined as an unscheduled return to the emergency department within 48 hours. "Conservative therapy" was any treatment regimen that did not include parenteral medications. During the next 2 years, the model was validated with patients not previously treated at this medical center. Seventy-six (28.3%) of 269 episodes resulted in hospital admission. The logistic model was used to categorize each visit during the validation phase. "High-risk" visits had calculated probabilities of admission greater than .208, while "low-risk" visits had values that were less. The admission rate for 98 low-risk visits (8.2%) was much lower than the rate for 171 high-risk visits (39.8%). CONCLUSIONS: A multivariate model can be used to identify patients with decompensated chronic obstructive pulmonary disease who are unlikely to need hospitalization. This model could be used to select episodes of decompensated chronic obstructive pulmonary disease for treatment at home.

Understanding serum electrolytes. How to avoid mistakes.

Serum electrolyte levels by themselves may be difficult to interpret. For example, an abnormal serum potassium concentration cannot be understood without taking into account the patient's history, other serum electrolyte values, and possibly results of other laboratory tests. Knowledge of the principles of serum electrolyte concentrations, therefore, is an important adjuvant to understanding their implications.

Upper respiratory tract infections increase self-rated hostility and distress.

The authors administered a personality inventory, the Eysenck Personality Inventory and a distress scale, the Symptom Questionnaire, to all patients in a walk-in clinic of a general hospital during an influenza epidemic. Hostility, depression, anxiety and somatic symptoms were significantly higher in patients with upper respiratory tract infections (p less than .005); the majority scored in the range of psychiatric patients, regardless of whether patients had clinically classical influenza or merely symptoms and signs of another respiratory tract infection. There were no differences in the personality traits of extraversion or neuroticism between any of the groups, suggesting that hostility and distress were consequences of the viral infections and were largely unaffected by preexisting personality traits.