Characterization of obstructive sleep apnea-hypopnea syndrome (OSA) population by means of cluster analysis.

Obstructive sleep apnea-hypopnea syndrome (OSA) is being identified increasingly as an important health issue. It is typified by repeated episodes of upper airway collapse during sleep leading to occasional hypoxaemia, sleep fragmentation and poor sleep quality. OSA is also being considered as an independent risk factor for hypertension, diabetes and cardiovascular diseases, leading to increased multi-morbidity and mortality. Cluster analysis, a powerful statistical set of techniques, may help in investigating and classifying homogeneous groups of patients with similar OSA characteristics. This study aims to investigate the (possible) different groups of patients in an OSA population, and to analyse the relationships among the main clinical variables in each group to better understand the impact of OSA on patients. Starting from a well-characterized OSA population of 198 subjects afferent to our sleep centre, we identified three different communities of OSA patients. The first has a very severe disease [apnea-hypopnea index (AHI) = 65.91 ± 22.47] and sleep disorder has a strong impact on daily life: a low level of diurnal partial pressure of oxygen (PaO2 ) (77.39 ± 11.64 mmHg) and a high prevalence of hypertension (64%); the second, with less severe disease (AHI = 28.88 ± 17.13), in which sleep disorders seem to be less important for diurnal PaO2 and have a minimum impact on comorbidity; and the last with very severe OSA (AHI = 57.26 ± 15.09) but with a low risk of nocturnal hypoxaemia (T90 = 11.58 ± 8.54) and less sleepy (Epworth Sleepiness Scale 10.00 ± 4.77).

Is the Exhaled Breath Temperature Sensitive to Cigarette Smoking?

The smoking habit is accompanied by an acute inflammatory response which follows tissue injury. It would be desirable to find a non-invasive inflammatory marker that would simplify the task of studying and monitoring smokers more simply and allow us to identify populations at risk of contracting Chronic Obstructive Pulmonary Disease (COPD). Today's expectations regarding research focus on issues ranging from inflammatory markers to those of exhaled breath temperature (EBT) are considerable. That said, although the EBT has been largely studied in asthma and COPD, there have not been any studies thus far that have analysed the effect of cigarette smoking on the EBT. Bearing this in mind, in this longitudinal study we aim to analyse the EBT in current smokers, monitor the effects both of cigarette smoking on EBT and of what happens after smoking cessation. Twenty-five (25) smokers (59.5 ± 3.1 yrs, 12 M) who participated in a multi-disciplinary smoking cessation programme and 25 healthy never-smokers (58.7 ± 2.9, 13 M) underwent EBT measurement. EBT values were higher in smokers before smoking (T0) than in never-smokers [34.6 (34.2-35) vs 33.2 (32.4-33.7)°C, p < 0.001. The smokers repeated measurement 5 minutes after smoking a cigarette (T1) and 2 hours after (T2). They repeated EBC measurement after 1 week (T3) and then after 3 months (T4) from smoking cessation. EBT is higher in smokers compared to controls. EBT increases after cigarette smoking and progressively decreases with the increase of time from when the last cigarette was smoked. Thus, we can conclude that EBT is increased in smokers and also sensitive to the acute effect of cigarette smoke.