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Objective: The anaerobic threshold (AT) is a submaximal index related to endurance exercise performance, which is usually determined by the measurement of blood lactate concentration during an incremental exercise test (lactate threshold [LT]). The LT, and thus the AT, can also be detected noninvasively in normal subjects by means of the gas exchange threshold (GET). This study was undertaken to validate the use of GET in patients with cystic fibrosis (CF) with a wide range of disease severity, and to assess the reproducibility of this index. Methods: In patients with CF (FEV1 range, 23 to 118% of predicted) and control subjects, gas exchange was measured breath by breath during the incremental exercise tests to allow determination of the GET. Arterialized-venous blood was sampled for determination of the LT. The GET and LT were determined in a blinded manner. Results: The mean differences (GET LT) for control subjects (n 18) and patients with CF (n 23) were 40 mL/min and 10 mL/min, respectively, neither being significantly different from zero. The limits of agreement were 550 mL/min and 410 mL/min, respectively. The mean test-retest differences in GET for control subjects (n 14) and patients with CF (n 12) were 50 mL/min and 0 mL/min, respectively, neither being significantly different from zero; the respective limits of reproducibility were 450 mL/min and 350 mL/min. Conclusions: This study demonstrates that in patients with CF, the GET can be used to obtain an unbiased estimate of the LT, and that the GET is reproducible. (CHEST 2002; 121:1761–1770)

Study objectives: To determine whether the adenine (A)-guanine (G) substitution polymorphism at position - 308 on the tumor necrosis factor-a gene confers susceptibility to COPD or to the development of a more severe form of disease. Design: A cross-sectional study was undertaken to compare the frequency of the A allele in a group of 106 patients with COPD with that in a control population (n 5 99). Patients were followed up prospectively for a period of 2 years. Participants and setting: Participants included 106 COPD patients recruited from a respiratory outpatient clinic and 99 control subjects recruited from patients admitted for cardiac catheterization. Measurements and results: DNA was extracted from venous blood, and each subject was genotyped for the polymorphism by polymerase chain reaction amplification and restriction digestion using Nco1. There was no increased frequency of the A allele in patients compared to control subjects. AA homozygous patients had less reversible airflow obstruction (p < 0.05) and a significantly greater mortality (both all-cause and respiratory deaths) on follow-up (p < 0.001), despite a shorter cigarette smoking history. Conclusions: This study suggests that homozygosity for this A allele predisposes to more severe airflow obstruction and a worse prognosis in COPD. (CHEST 2000; 118:971‐975)

Objectives Exercise testing in patients with cystic fibrosis (CF) has become an important tool in assessing disease severity and predicting overall outcome. The reproducibility of maximal exercise testing was examined in adult subjects with stable CF. Methods Nine subjects with CF underwent a total of three maximal exercise tests carried out under identical circumstances over a 28-day period. Oxygen uptake ( o 2), minute ventilation ( e ), respiratory frequency (f), heart rate (HR), and arterial oxygen saturation (Sa o 2) were measured at rest, at end exercise, and at 40% and 70% of maximum workload. Results There were no significant differences in these measurements among the three tests. Reproducibility of exercise performance was assessed using the coefficient of variation. The mean within-subject coefficient of variation for test variables at end exercise are as follows: o 2, 6.9%; e , 6.2%; f, 5.8%; HR, 3.0%; and Sa o 2, 1.1%. The mean within-subject coefficient of variation for test variables at 40% and 70% of maximal work rates are as follows: o 2, 5.2% and 4.6%; Sa o 2, 0.3% and 0.9%; HR, 4.0% and 3%; e , 5.7% and 6.5%; and f, 5.8% and 7.2%, respectively. Conclusions Variables measured during clinical cycle ergometer exercise testing in adult patients with stable CF are reproducible. No learning effect was found on repeated testing.

Chronic eosinophilic pneumonia (CEP) is a rare disorder of unknown etiology characterized by striking systemic and pulmonary manifestations such as fever, weight loss, blood eosinophilia, characteristic fluffy peripheral opacities on chest radiograph, and a prompt response to corticosteroid therapy. While the initial phase has been well documented, there is very limited information concerning the long-term natural history and treated course of this condition. We report the clinical and laboratory findings together with the long-term follow-up data on 12 patients with classic CEP who were followed up for a mean of 10.2 years (range, 4 to 13 years). The most striking feature of the long-term follow-up was the occurrence of relapses of CEP (often on multiple occasions) when corticosteroid therapy was discontinued or the dose was tapered. In those nine patients in whom steroid withdrawal was commenced, there was a clinical, hematologic, and radiologic relapse in seven (58 percent). However, prompt reinstitution of therapy led to a rapid resolution of symptoms. By contrast, two patients (17 percent) showed no evidence of relapse when steroid therapy was discontinued. A further three patients (25 percent) are maintained on a regimen of low-dose steroid therapy with no episodes of relapse. Reassuringly, all 12 patients are well at the end of a long period of follow-up. These data suggest that the long-term prognosis for patients with CEP is excellent but the majority will require long-term low-dose oral corticosteroid therapy in order to prevent relapse.

Patients with cystic fibrosis (CF) desaturate during sleep and during exercise but by different mechanisms. To determine the need for supplemental oxygen, many centers measure resting and exercise arterial oxygen saturation (SaO2). We examined the associations among resting, sleep, and exercise SaO2 to ascertain the validity of this approach. We studied 21 adult and adolescent CF patients, eight of whom were hypoxemic (SaO2 less than 95 percent; group A) and 13 of whom were nonhypoxemic (SaO2 greater than or equal to 95 percent; group B) by overnight oximetry and treadmill exercise testing. The whole group desaturated more during sleep than during exercise, the change in SaO2 being 10.59 +/- 8.35 vs 6.25 +/- 4.44 (p less than 0.002). Group B desaturated significantly more during sleep than during exercise, with a reduction in SaO2 of 7.9 +/- 3.3 vs 3.3 +/- 1.49 (p less than 0.05). Group A desaturated more during exercise than group B, with a reduction of 11 +/- 3.2 vs 3.3 +/- 1.5 (p less than 0.001). Despite a strong correlation between awake SaO2 and mean sleep SaO2 (r = 0.68; p less than 0.001), minimum sleep SaO2 (r = 0.55; p less than 0.01), and minimum exercise SaO2 (r = 0.92; p less than 0.001), there was no correlation between awake SaO2 and sleep-related desaturation or between exercise- and sleep-related desaturation. In conclusion, clinically significant oxygen desaturation during sleep may be missed unless specifically checked in CF patients, and awake and exercise SaO2 may not give an indication of the degree of sleep-related desaturation.

We describe two siblings with a progressive unrelenting and unique syndrome of bilateral fibrosing pleuritis of unknown cause occurring in association with Fanconi's syndrome (renal tubular acidosis). The parents of the siblings were second cousins. Both siblings had identical pleural histologic characteristics and identical urinary metabolic defects. This condition resulted in the development of severe respiratory failure in both patients and ultimately the death of the older sibling at the age of 21 years.

Paradoxical vocal cord adduction (PVCA) is a rare disorder that may present with symptoms similar to asthma. Incorrect diagnosis may result in patients being unwittingly treated with prolonged high doses of antiasthma medication. PVCA probably forms part of a spectrum of uncommon and complex breathing disorders related to laryngeal dysfunction. Herein, we describe three cases of PVCA that illustrate the spectrum of clinical and physiologic presentation and the long-term natural history over a 10-year follow-up period. We conclude that PVCA, contrary to previous reports, is not always a benign condition; it may feature marked hypoxemia, fail to respond to previously advocated therapeutic strategies, and can persist on a long-term basis.

To investigate the role of bronchoalveolar lavage type 3 procollagen peptide as a prognostic indicator in sarcoidosis, we measured type 3 procollagen N-terminal peptide levels in lavage fluids from 84 sarcoidosis patients and monitored disease progress in these patients for a period of 12 months. Lavage procollagen peptide levels were significantly elevated in sarcoidosis patients compared to control subjects (p (Chest 1989; 96:339–44)