Predictive values of the character, timing, and complications of chronic cough in diagnosing its cause.

BACKGROUND: It is not clear whether careful history taking with detailed questioning of the characteristics of cough is diagnostically useful. OBJECTIVE: To determine if the character, timing, or complications of chronic cough were helpful in determining its cause. METHODS: A prospective, descriptive study of consecutive, unselected, immunocompetent patients referred to our university outpatient clinic because of chronic cough. All patients were evaluated by a previously published and validated systematic diagnostic protocol, a self-administered questionnaire, and by observing the character of involuntary and voluntary coughs. The final diagnosis of the cause of cough required fulfillment of pretreatment criteria plus having cough disappear or substantially improve as a complaint with specific therapy. RESULTS: Eighty-eight patients met inclusion criteria and were fully evaluated. The mean +/- SD age was 53.1 +/- 16 years (range, 15-83 years) and 24 were males and 64 were females with a mean +/- SD history of cough for 6.6 +/- 9.8 years (range, 1 month-44 years). The cause of chronic cough was established in 86 (98%) of 88 patients. Eighty-one (92%) of 88 had cough disappear as a complaint. Cough was as a result of a single cause in 39% and multiple causes in 59%. Gastroesophageal reflux disease, postnasal drip syndrome, and asthma were the 3 most common causes of chronic cough and accounted for 90% of diagnoses. Gastroesophageal reflux disease, postnasal drip syndrome, and asthma were again found to be the 3 most common causes of chronic cough irrespective of patient estimated quantity of daily sputum production. These 3 conditions caused chronic cough in 99.4% of patients with the following characteristics: (1) nonsmoker; (2) not receiving an angiotensin-converting enzyme inhibitor drug; and (3) normal or nearly normal and stable chest radiograph. With respect to the spectrum and frequency of diagnoses and their interrelationships with the character, timing, and complications of cough, multiple stepwise linear regression analysis showed that none of the variability of the character, timing, or complications of cough could be explained by any specific diagnosis. CONCLUSIONS: A carefully taken history with detailed questioning of the character, timing, and complications of chronic cough is not likely to be useful in diagnosing the cause of cough. The cause can be determined and successfully treated with specific therapy in the greatest majority of cases. Chronic cough is often caused by multiple, simultaneously contributing causes. Postnasal drip syndrome, asthma, and gastroesophageal reflux disease remain the 3 most common causes of chronic cough and there is a clinical profile that nearly always predicts their presence in immunocompetent patients.

Cause and evaluation of chronic dyspnea in a pulmonary disease clinic.

To test whether, in patients with chronic dyspnea, a diagnostic approach based on objective confirmation of suspected diagnoses would be superior to one based on clinical impression alone, we prospectively studied 85 patients with a primary complaint of dyspnea seen in a pulmonary subspecialty clinic. We achieved 100% success in determining the causes of dyspnea compared with only 66% accuracy based on clinical impression alone. Four groups of disorders, asthma, chronic obstructive pulmonary disease, interstitial lung diseases, and cardiomyopathy accounted for two thirds of the cases. Findings on the history and physical examination were too nonspecific to determine the specific diagnosis. Pulmonary function testing, including a methacholine bronchoprovocation challenge, were the most useful diagnostic tests, particularly for chronic obstructive pulmonary disease and asthma. Chest roentgenogram was most useful for interstitial lung disease, and comprehensive exercise testing for dyspnea due to psychogenic factors or deconditioning. Specific therapy was effective in reducing or eliminating dyspnea in the majority of cases. We conclude that a diagnostic approach to chronic dyspnea based on objective findings and verification, rather than clinical impression alone, will consistently lead to an accurate diagnosis and an improved therapeutic outcome.

'Toxic strep syndrome'. A manifestation of group A streptococcal infection.

Three patients presented with multisystem disease that shared many of the features of toxic shock syndrome. Bacteriologic and serologic evidence strongly suggested that group A beta-hemolytic Streptococcus had caused the illnesses. Group A streptococcal infection may be an underdiagnosed cause of a toxic streptococcal syndrome, a syndrome of multisystem disease apparently mediated by toxins.

From a prospective study of chronic cough: diagnostic and therapeutic aspects in older adults.

BACKGROUND: Cough is the most common complaint for which adults see a physician in the ambulatory setting in the United States. An anatomical diagnostic protocol has been used since 1981 to evaluate patients with chronic cough. It has been shown to be effective in diagnosing the cause of cough and leading to specific treatment in a variety of adult populations but has never been evaluated specifically in a population of older adults. OBJECTIVES: To question whether the spectrum and frequency of causes of chronic cough and the response to therapy would be different in older adults. METHODS: Thirty patients at least 64 years of age with a history of cough lasting at least 3 weeks were prospectively evaluated with a protocol designed to detect diseases that stimulate the afferent limb of the cough reflex. The final diagnosis of the cause of chronic cough required fulfillment of pretreatment criteria and having cough disappear with specific therapy. When more than one disease fulfilled pretreatment diagnostic criteria, therapy was instituted in the order that these were fulfilled. Probability statistics were used to describe the testing characteristics of individual components of the diagnostic protocol in terms of sensitivity, specificity, positive predictive value, and negative predictive value as they applied to chronic cough. RESULTS: Forty causes of chronic cough were identified in all 30 patients. Postnasal drip syndrome, gastroesophageal reflux disease, and asthma were the most common causes of chronic cough, accounting for 85% of all causes found. Among patients with normal chest radiograph findings who were not cigarette smokers and not taking an angiotensin-converting enzyme inhibitor, postnasal drip syndrome, gastroesophageal reflux disease, and asthma accounted for 100% of all causes found. Specific therapy was successful in eliminating chronic cough in 100% of the patients studied. Except for barium esophagography, all laboratory tests for which information was available had sensitivities and negative predictive values of 100%. CONCLUSIONS: Postnasal drip syndrome, gastroesophageal reflux disease, and asthma accounted for 85% of all causes of chronic cough in older adults. Chronic cough caused substantial physical and emotional morbidity among older patients. The major value of performing objective testing in evaluating chronic cough is its ability to rule out specific diseases as a diagnostic possibility. The following clinical profile consistently predicts patients with cough attributable to gastroesophageal reflux disease: the patient has cough that has been persistently troublesome for at least 3 weeks; does not smoke cigarettes; does not take an angiotensin-converting enzyme inhibitor; does not have or has not responded to therapy for postnasal drip syndrome and asthma; and has normal or nearly normal findings and stable chest radiograph. The differences between what we observed regarding chronic cough in older adults and observations by ourselves and others regarding chronic cough in general are minor.

Interpretation of positive results of a methacholine inhalation challenge and 1 week of inhaled bronchodilator use in diagnosing and treating cough-variant asthma.

BACKGROUND: In diagnosing cough due to asthma, methacholine chloride inhalation challenge (MIC) interpreted in a traditional fashion has been shown to have positive predictive values from 60% to 82%. OBJECTIVE: To determine whether any features of positive results of an MIC or the results of a 1-week trial of inhaled beta-agonist therapy were helpful in predicting when the cough was due to asthma. METHODS: The study design was a prospective, randomized, double-blind, placebo-controlled, crossover format performed in adult, nonsmoking subjects, who were referred for diagnosis and treatment of chronic cough. The subjects had no other respiratory complaints or medical conditions for which they were taking medications, the results of baseline spirometry and chest roentgenograms were normal, and the results of MIC were positive. After obtaining baseline data, including MICs on 2 separate days, objective cough counting, and self-assessment of cough severity using a visual analog scale, subjects were randomized to receive 2 inhalations (1.3 mg) of metaproterenol sulfate or placebo by metered dose inhaler attached to a spacer device every 4 hours while awake. At 1 week, data identical to baseline were collected, and subjects received the other metered dose inhaler for 7 days. At 1 week, data identical to baseline were collected. After completion of the protocol, subjects were followed up in the clinic to observe the final response of the cough to specific therapy. RESULTS: Based on the disappearance of the cough with specific therapy, the cough was due to asthma in 9 of 15 subjects and nonasthma in 6 of 15 subjects. Baseline data were similar between groups. With respect to MICs, there were no significant differences between groups in the cumulative dose of methacholine that provoked a 20% decrease in forced expiratory volume in 1 second from the postsaline baseline value (PD20 values), slopes of dose-response curves, and maximal-response plateaus. Cough severity significantly improved after 1 week of metaproterenol use compared with the severity of the cough at baseline (P = .03) and with placebo (P = .02) only in subjects with asthma. CONCLUSIONS: No matter how the results are analyzed, positive MIC results, without observing response to therapy, are only consistent with asthma as the cause of the cough. The results are only diagnostic of asthma when they are followed by a favorable response to asthma therapy. After 1 week of inhaled beta-agonist, only the cough due to cough-variant asthma is significantly better.

Impact of chronic cough on quality of life.

BACKGROUND: Cough is the most common complaint for which adult patients seek medical care in the United States; however, the reason(s) for this is unknown. OBJECTIVES: To determine whether chronic cough was associated with adverse psychosocial or physical effects on the quality of life and whether the elimination of chronic cough with specific therapy improved these adverse effects. METHODS: The study design was a prospective before-and-after intervention trial with patients serving as their own controls. Study subjects were a convenience sample of 39 consecutive and unselected adult patients referred for evaluation and management of a chronic, persistently troublesome cough. Baseline data were available for 39 patients and follow-up for 28 patients (22 women and 6 men). At baseline, demographic, Adverse Cough Outcome Survey (ACOS), and Sickness Impact Profile (SIP) data were collected and patients were managed according to a validated, systematic protocol. Following specific therapy for cough, ACOS and SIP instruments were readministered. RESULTS: The ages, sex, duration, and spectra and frequencies of the causes of cough were similar to multiple other studies. At baseline, patients reported a mean +/- SD of 8.6 +/- 4.8 types of adverse occurrences related to cough. There were significant correlations between multiple ACOS items and total, physical, and psychosocial SIP scores. Psychosocial score correlated with total number of symptoms (P<.02). After cough disappeared with treatment, ACOS complaints decreased to a mean +/- SD of 1.9 +/- 3.2 (P<.0001) as did total (mean +/- SD, 4.8 +/- 4.5 to 1.8 +/- 2.2) (P= .004), psychosocial (mean +/- SD, 4.2 +/- 6.8 to 0.8 +/- 2.3) (P = .004), and physical (mean +/- SD, 2.2 +/- 2.9 to 0.9 +/- 1.8) (P = .05) SIP scores. Multiple linear regression analysis showed that 54% of variability of the psychosocial SIP score was explained by 4 ACOS items while none of the physical score was explained. CONCLUSIONS: Chronic cough was associated with deterioration in patients' quality of life. The health-related dysfunction was most likely psychosocial. The ACOS and SIP appear to be valid tools in assessing the impact of chronic cough.

The clinical implications of bilaterally abnormal impedance plethysmography.

Although impedance plethysmography (IPG) is a test of recognized value in the diagnosis of acute proximal deep venous thrombosis (DVT), its meaning in patients with bilaterally abnormal IPGs is unclear. Consequently, we sought to determine the clinical significance of the bilaterally abnormal IPG in hospitalized patients. In a five-month prospective study, 19% (81/425) of all IPGs done at our institution were bilaterally abnormal (55% of all abnormal IPGs). Acute proximal DVT was found in 26% (14/53) of patients with bilaterally abnormal IPGs who underwent further diagnostic testing. Thirty-five percent of the patients with DVT were found to have either bilateral lower extremity DVT or clots in the inferior vena cava. A numerical score, the venous function index (VFI), was computed for the 101 legs for which further definitive diagnostic evaluations for DVT had been completed. The mean VFI of seven for legs with acute proximal DVT was significantly less than the mean VFI of 13 for legs with no DVT. Fifty percent of legs with a VFI less than or equal to five had DVT, whereas only 7% of legs with a VFI greater than 15 had DVT. The bilaterally abnormal IPG is a common clinical occurrence, is frequently associated with acute DVT, and the VFI is helpful in discriminating legs with acute proximal DVT from normal legs in patients with a bilaterally abnormal IPG.

Complications associated with thoracentesis. A prospective, randomized study comparing three different methods.

To determine what role the technique plays in complications associated with thoracentesis performed by physicians in training, we undertook a prospective study of thoracentesis in the medical service at our institution in which the sampling method was randomized among needle, needle with catheter, and needle with direct sonographic guidance. Fifty-two spontaneously breathing, cooperative patients with free-flowing effusions obliterating more than half of the hemidiaphragm on an upright, posteroanterior chest roentgenogram were randomized. When we analyzed those complications that were potentially life-threatening (eg, pneumothorax) and/or placed patients at increased risk for further morbidity (eg, pneumothorax, dry tap, inadequate tap), the sonography-guided method was associated with significantly fewer serious complications (0 of 19) than the needle-catheter (9 of 18) or needle-only methods (5 of 15). The sonography-guided method was associated with fewer pneumothoraces (0 of 19) than the needle-catheter (7 of 18) or needle-only methods (3 of 15). The difference between needle-catheter and needle-only methods was not significant. From our results, we conclude that the method by which thoracentesis was performed significantly influenced the spectrum and frequency of complications, and the sonography-guided method was the safest.

Appropriate use of antitussives and protussives. A practical review.

As a symptom of an underlying condition, cough is one of the most common reasons patients see physicians. To the majority, a cough means that 'something is wrong' and it causes exhaustion and/or self-consciousness. Patients find these reasons as well as effects on lifestyle, fear of cancer and/or AIDS or tuberculosis to be the most troublesome concerns for which they seek medical attention. The treatment of cough can be divided into two main categories: (a) therapy that controls, prevents or eliminates cough (i.e. antitussive); and (b) therapy that makes cough more effective (i.e. protussive). Antitussive therapy can be either specific or nonspecific. Definitive or specific antitussive therapy depends on determining the aetiology or operant pathophysiological mechanism, and then initiating specific treatment. Since the cause of chronic cough can almost always be determined, it is possible to prescribe specific therapy that can be almost uniformly successful. Non-specific antitussive therapy is directed at the symptom; it is indicated when definitive therapy cannot be given. Practically speaking, the efficacy of nonspecific therapy must be evaluated in double-blind, placebo-controlled, randomised studies of pathological cough in humans. Such studies have demonstrated the efficacy of dextromethorphan, codeine and ipratropium bromide aerosol in patients with chronic bronchitis. While the preferred treatment for patients with cough due to angiotensin converting enzyme (ACE) inhibitor therapy is withdrawal of the offending drugs, it may be possible to ameliorate the cough by adding nifedipine, sulindac or indomethacin to the treatment regimen. The efficacy of protussive therapy has not been well documented. Although hypertonic saline aerosol and erdosteine in patients with bronchitis, and amiloride aerosol in patients with cystic fibrosis have been shown to improve mucus clearance, their clinical utility has not been adequately studied.

Difficult-to-control asthma. Contributing factors and outcome of a systematic management protocol.

To our knowledge, there are no published results of protocols for managing difficult to control asthma (DTCA) or of the spectrum and frequencies of reasons why asthma can be difficult to control (DTC). To assess the usefulness of a systematic management protocol and determine the reason(s) why asthmatics are DTC, we developed a protocol that systematically considered multiple factors that may make asthma worse and prospectively evaluated the outcomes of therapeutic interventions for these factors and of inhaled corticosteroids (ICS) and azathioprine. We studied 42 consecutive and unselected DTCAs (19 men and 23 women) whose age was 48 +/- 15.9 years. They had a diagnosis of asthma for 15.1 +/- 15.8 years, were DTC for 4.8 +/- 7.8 years, and were followed up by us in the study for a total of 3.5 +/- 1.9 years. Initially, the dose of prednisone was 30.2 +/- 22 mg/d. Following utilization of the protocol, 74 percent were no longer DTC. It took 1.8 +/- 1.7 years for them to no longer be DTC; they remained so for 1.8 +/- 1.5 years. In these patients, 2.7 +/- 1.2 factors appeared to be responsible for the DTC state; 80 percent had > or = 2. Improvement was more likely if gastroesophageal reflux (GER) was a factor (p = 0.014); it correlated with the addition of ICS (p = 0.04) and treatment for GER (p = 0.02). Failure to reverse DTCA correlated with the suspicion (p = 0.004) and admission of nonadherence (p = 0.04). In 14 patients given azathioprine, prednisone dose decreased from 45 +/- 25.3 to 13.3 +/- 21.6 mg/d (p = 0.003); 6 of 14 achieved no longer DTC status; and substantial morbidity occurred. The reason(s) for DTCA could be determined in most instances by utilizing a systematic protocol; multiple factors were responsible in the majority of cases; treatment for GER and ICS were the two most helpful interventions; nonadherence was the most likely reason suspected for maintaining DTCA; and azathioprine acted as a corticosteroid-sparing agent that should not be prescribed routinely.

Chronic cough with a history of excessive sputum production. The spectrum and frequency of causes, key components of the diagnostic evaluation, and outcome of specific therapy.

STUDY OBJECTIVE: To determine (1) the spectrum and frequency of causes of chronic cough with a history of excessive sputum production (CCS) and (2) the response of these causes to specific therapy. STUDY DESIGN: Prospective study utilizing the anatomic diagnostic protocol originally developed to diagnose chronic cough. PATIENTS: Seventy-one immunocompetent adults who complained of expectoration of greater than 30 mL of sputum per day. LOCATION: University hospital pulmonary outpatient clinic. RESULTS: Patients were seen an average of 4.2 times over 4.6 months before a specific diagnosis was made. The cause of CCS was determined in 97%. It was due to one cause in 38%, 2 in 36%, and three in 26%. Postnasal drip syndrome (PNDS) was a cause 40% of the time, asthma 24%, gastroesophageal reflux disease (GERD) 15%, bronchitis 11%, bronchiectasis 4%, left ventricular failure 3%, and miscellaneous causes 3%. Among patients with a normal chest radiograph who were nonsmokers and not taking an angiotensin converting enzyme inhibitor; CCS was due to PNDS, or asthma, or GERD, or all three in 100% of cases. Chest radiograph, methacholine inhalation challenge, 24-h esophageal pH monitoring, bronchoscopy, and spirometry with bronchodilator each had a sensitivity and negative predictive value of 100%. Chest radiograph and barium swallow had positive predictive values of only 38% and 30%, respectively. CONCLUSIONS: (1) The anatomic diagnostic protocol for cough is also valid for CCS; (2) the major causes of chronic excessive sputum production and chronic cough are so similar that CCS should be considered a form of chronic cough; (3) the evaluation of CCS is more complicated and takes longer than the evaluation of chronic cough; (4) the major strength of the laboratory diagnostic protocol is that it reliably rules out conditions; (5) the outcome of specific therapy is almost always successful; and (6) the term "bronchorrhea" can be misleading if it is applied to excessive sputum production before a specific diagnosis of its source is made since the most common cause of excessive sputum that is expectorated (PNDS) is a disorder of the upper respiratory tract. Therefore, nonspecific therapies theoretically aimed at reducing mucus production in the lower respiratory tract are not likely to be helpful.

Chronic cough due to gastroesophageal reflux. Clinical, diagnostic, and pathogenetic aspects.

BACKGROUND: Gastroesophageal reflux (GER) is a common cause of chronic cough. Moreover, chronic cough can be the sole presenting manifestation of GER disease (GERD). It has been suggested recently that GER most often causes chronic cough by stimulating the distal esophagus. To gain further diagnostic and pathophysiologic knowledge, we prospectively evaluated a group of patients with chronic cough likely to be due to GER with extensive gastrointestinal and respiratory studies and then observed their response to antireflux therapy. METHODS: We prospectively characterized 12 subjects whose chronic cough was likely to be due to GER by chest radiographs, barium esophagography, 24-h esophageal pH monitoring (EPM) with probes in the distal and proximal esophagus, esophagoscopy, and bronchoscopy. Then, prior to instituting antireflux therapy, we objectively counted coughs during the distal esophageal infusion of 0.1 N HCl or 0.9 percent saline solution administered in a randomized, double-blind, standardized fashion (ie, Bernstein acid-perfusion test). RESULTS: Gastroesophageal reflux was determined to cause cough in all subjects based on disappearance of cough with antireflux therapy. It was clinically "silent" in 75 percent. The EPM was the test most frequently abnormal (sensitivity, 92 percent). Distal esophageal data revealed that 10 of 12 subjects had GER-induced coughs (12 +/- 12) while only 7 of 12 had an abnormal esophageal pH conventional parameter (eg, percent time pH < 4). Compared with the distal esophagus, GER to the proximal esophagus occurred (p = 0.017) and induced cough (p = 0.004) less often. Compared with baseline (9.3 +/- 17.6), there were no differences in coughs induced by the infusion of saline solution (9.2 +/- 15.9) or acid (15.1 +/- 26.7); the number of coughs induced by acid was negatively correlated with distal esophageal acid-GER events during EPM (r = -0.64, p = 0.01). Neither bronchoscopy nor chest radiographs were consistent with aspiration. CONCLUSIONS: There is a clinical profile that prospectively predicts which patients have chronic cough due to GER. The cough was most likely due to stimulation of the distal esophagus, not aspiration. Intraesophageal acid is unlikely to be the sole mediator in gastric juice causing the cough. While EPM is the single most helpful diagnostic test, conventionally utilized diagnostic indices of GERD can be misleadingly normal; observing GER-induced coughs is more frequently helpful.

Transbronchial lung biopsy: can specimen quality be predicted at the time of biopsy?

STUDY OBJECTIVES: To determine the bronchoscopist's ability to predict specimen quality at the time of transbronchial biopsy and to determine the influence of biopsy specimen size and alveolar content on diagnostic value. DESIGN: Prospective, blinded, observational analysis. SETTING: Tertiary care academic hospital-based pulmonary practice. PATIENTS: Forty-three adult patients who underwent transbronchial lung biopsy. INTERVENTIONS: Each of 170 biopsy specimens was rated as to likelihood of containing diagnostic tissue, size and ability to float, tissue types present, number of alveoli, and pathologic diagnosis. RESULTS: Fifteen percent of biopsy specimens were small and 40% were large. Seventy-six percent of specimens floated; 61.8% of the 170 biopsy specimens contained abnormal lung tissue; and 14.7% of individual specimens were diagnostic. Fifty-two percent of specimens contained >20 alveoli. Larger biopsy specimens were more likely to contain diagnostic tissue (r=0.29, p=0.001). Cup forceps retrieved smaller pieces of tissue (p=0.007) and were less likely to obtain diagnostic tissue (p=0.06). Physician ratings of specimen quality (mean+/-SD) did not differ between specimens containing normal and abnormal tissue (5.98+/-2.3 vs 5.46+/-5.5; p=0.24) or between specimens containing diagnostic vs nondiagnostic tissue (5.56+/-2.5 vs 6.25+/-2.1; p=0.14). Specimens that floated were no more likely to be diagnostic or abnormal than specimens that sank (p<0.05). Diagnosis when established was made by the first biopsy specimen in 53.3% and the second in 33.3% CONCLUSIONS: Physician estimate of biopsy specimen quality and the float sign are not helpful in predicting that the biopsy specimen contains abnormal or diagnostic tissue. Diagnostic biopsy specimen will likely be obtained if the size of the specimen fills the forceps, 2 to 4 biopsies are performed, and toothed forceps are used.

Accuracy of 30-minute indirect calorimetry studies in predicting 24-hour energy expenditure in mechanically ventilated, critically ill patients.

BACKGROUND: There is no consensus regarding the optimal duration of measurement or time of day to perform indirect calorimetry (IC). Energy expenditure (EE) varies at different times of day and with different activity levels. We sought to assess the variability of EE in mechanically ventilated patients over a 24-hour period and the accuracy of 30-minute IC studies in predicting the 24-hour energy expenditure (EE24). METHODS: The study was a prospective comparison between the resting EE obtained by 30-minute measurement of IC and EE values obtained from 24-hour measurements. Tests were performed in the Medical Intensive Care Unit (MICU) of a tertiary care, university hospital. Oxygen consumption (VO2) and carbon dioxide production (VCO2) were measured for 24 hours in eight ventilated patients. Measurements were made every 3 minutes and used to calculate 30-minute and 24-hour oxygen consumption values. EE24 was calculated using the modified Weir equation. Each 30-minute interval was compared with the value obtained from the 24-hour measurement. RESULTS: Three hundred forty-one of 384 30-minute intervals remained for analysis. Average EE24 measured was 1490 +/- 486 kcal/d. Average EE24 predicted by extrapolation from 30-minute studies was 1501 +/- 503 kcal/d, with a mean difference of 0 +/- 209 kcal/d from the measured 24-hour values (range: -1068 to +585 kcal/d). Thirty-minute studies were within 20% of 24-hour measurements for 89% of intervals. The difference between 24-hour and 30-minute studies correlated with changes in minute ventilation (VE), heart rate, systolic blood pressure, and breath rate from their 24-hour means (p < .001). The mean error of EE estimate was greatest between 3 and 11 PM (p < .001). CONCLUSIONS: We conclude the following: (1) EE in MICU patients is variable; (2) 30-minute IC studies predict measured EE24 acceptably well for clinical purposes; and (3) accuracy is maximized if a 30-minute study is performed between 11 PM and 3 PM, and when Ve, heart rate, systolic blood pressure, and breath rate are near the day's average.

Stereociliary pathology and noise-induced threshold shift: a scanning electron microscopic study.

Cats were exposed unilaterally to narrow-band noise at an intensity of 118-120 dB SPL for two hours. After long survival times thresholds of single auditory units were measured and the organ of Corti examined with a scanning electron microscope (SEM). The purpose of the study was to correlate pathologies of the hair cell stereocilia seen with the SEM with permanent hearing loss measured by elevated thresholds of single auditory nerve units. Pathological changes in inner hair cell (IHC) stereocilia were more severe and more numerous near the lesion focus diminishing progressively with increasing distance from it. Increasingly elevated thresholds correlated with increased damage to stereocilia of IHCs. Thresholds of nerve fibers innervating IHCs with missing or fused stereocilia were greatly elevated. Thresholds of fibers to IHCs with disarrayed stereocilia also seemed to be elevated but to a lesser degree.