Long-term effects of treatment with nasal continuous positive airway pressure on lung function in patients with overlap syndrome.

We assessed the effects of chronic nasal continuous positive airway pressure (CPAP) therapy on lung function in a series of unselected patients with overlap syndrome, and we determined whether there were differences in the response induced by CPAP between hypercapnic (PaCO2 > or =45 mm Hg) and eucapnic patients with overlap syndrome. The study population included 55 unselected patients (48 men, mean age of 58.5 +/- 10.5 years) with a concurrent diagnosis of chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea-hypopnea syndrome (OSAHS) who had been referred to the Department of Pulmonology of our hospital over 2 consecutive years and in whom work-up studies resulted in the prescription of nasal CPAP therapy. An apnea-hypopnea index (AHI) greater than or equal to 10 in the cardiorespiratory polygraphy was required for the diagnosis of OSAHS. A forced expiratory volume in one second (FEV1) less than 80% and FEV1-forced vital capacity (FVC) ratio less than 70% of the reference values were required for the diagnosis of COPD. Control lung function studies and arterial blood gas measurements were performed at 6 and 18 months of CPAP therapy. These patients with overlap syndrome accounted for 28.5% of all patients with OSAHS treated with CPAP during the study period. The mean AHI was 37.3 +/- 26.1 and the mean CPAP level 7.3 +/- 1.3 cm H2O. Thirty-three patients were hypercapnic (PaCO2 > or = 45 mm Hg) and 22 eucapnic. The hypercapnic group had higher AHI value (44.3 +/- 26.9) than the eucapnic group (28.6 +/- 21.9) (P < 0.05). After 6 months of CPAP therapy, there were statistically significant increases in PaO2, FEV1, and FVC, accompanied by significant decreases in PaCO2, serum bicarbonate levels, and alveolar-arterial oxygen difference. Response of overlap syndrome patients to CPAP therapy was superior in the hypercapnic group, particularly in relation to improvement of arterial blood gases. However, statistically significant differences in all parameters for the comparison between 6 and 18 months were not recorded.

Cigarette smoking behavior and respiratory alterations during sleep in a healthy population.

BACKGROUND AND STUDY OBJECTIVE: The importance of tobacco smoking in the origin of sleep ventilatory abnormalities is disputed. The purpose of our study was to evaluate the influence of cigarette smoking behavior on the sleep respiratory alterations in a healthy population. DESIGN AND METHODS: We studied 38 healthy volunteers (21 M, 17 F; age 42 +/- 12 years; BMI 23.7 +/- 3.6 kg/m(2)) who were divided into two matched groups: current tobacco smokers (n = 18; over 10 pack-years) and nonsmokers (n = 20). All individuals underwent a single nocturnal domiciliary polygraphic study (Polygraphics CNS, Minneapolis, Minnesota). Apnea (AI), apnea-hypopnea (AHI), and desaturation (DI) indexes were defined according to conventional criteria. A nocturnal hypoxia index (NHI) was calculated as an index of the magnitude and duration of oxyhemoglobin desaturation during sleep. The mean transcutaneous oxygen saturation (SpO(2)) of the first 60 seconds of oxymetric registration (subject supine and awake) was considered basal SpO(2). Venous carboxyhemoglobin (COHb) levels were measured (CO-Oximeter AVL-912, Basel, Switzerland) in all individuals before (22:00 h) and after (10:00 h) sleep. A correction factor of 0.9 x COHb was applied to the basal SpO(2) values to calculate the corrected basal SpO(2) (SpO(2 corr)). RESULTS: AI, AHI, and DI were not significantly different between smokers and nonsmokers. The smokers have significantly higher NHI than nonsmokers [median (25th percentile-75th percentile): 5.3 (0-39.7) vs. 0.5 (0-1.7); p = 0.017]. There were significant correlations (P < 0.05) in smokers between NHI and pack-years index, between NHI and COHb levels, and between current smoking intensity and COHb levels. As expected, smokers had higher COHb levels at 10:00 as well as at 22:00 hours. The SpO(2 corr) was significantly lower (p < 0.001) among smokers than nonsmokers (88.9 +/- 3.3% vs. 94.7 +/- 1.3%). In multiple regression analyses, AHI and DI showed a significant correlation (p = 0.02 and p = 0.05, respectively) with habitual snoring, and NHI with pack-years and BMI (p = 0.02 and p = 0.04, respectively). CONCLUSIONS: Cigarette smoking does not seem to be associated with increased apneic activity during sleep. However, it is associated with a decrease in nocturnal oxygen saturation.