Background -Smoking may cause inflammation of the airways and impairment of lung function. To determine the relationship between the type and degree of airways inflammation and the decline in lung function, leucocytes in the

A cross-sectional epidemiological study was carried out among 141 male subjects exposed to inorganic manganese (Mn) in a Mn oxide and salt producing plant (mean age 34.3 years; duration of exposure, mean 7.1 years, range 1-19 years). The results were compared with those of a matched control group of 104 subjects. The intensity of Mn exposure was moderate as reflected by the airborne Mn levels and the concentrations of Mn in blood (Mn-B) and in urine (Mn-U). A significantly higher prevalence of cough in cold season, dyspnea during exercise, and recent episodes of acute bronchitis was found in the Mn group. Lung ventilatory parameters (forced vital capacity, FVC; forced expiratory volume in one second, FEV1; peak expiratory flow rate, PEFR) were only mildly altered in the Mn group (smokers) and the intensity and the prevalence of these changes were not related to Mn-B, Mn-U, or duration of exposure. There was no synergistic effect between Mn exposure and smoking on the spirometric parameters. Except for a few nonspecific symptoms (fatigue, tinnitus, trembling of fingers, increased irritability), the prevalence of the other subjective complaints did not differ significantly between the control and Mn groups. Psychomotor tests were more sensitive than the standardized neurological examination for the early detection of adverse effects of Mn on the central nervous system (CNS). Significant alterations were found in simple reaction time (visual), audioverbal short-term memory capacity, and hand tremor (eye-hand coordination, hand steadiness). A slight increase in the number of circulating neutrophils and in the values of several serum parameters (ie, calcium, ceruloplasmin, copper, and ferritin) was also found in the Mn group. There were no clear-cut dose-response relationships between Mn-U or duration of Mn exposure and the prevalence of abnormal CNS or biological findings. The prevalences of disturbances in hand tremor and that of increased levels of serum calcium were related to Mn-B. The response to the eye-hand coordination test suggests the existence of a Mn-B threshold at about 1 microgram Mn/100 ml of whole blood. This study demonstrates that a time-weighted average exposure to airborne Mn dust (total dust) of about 1 mg/m3 for less than 20 years may present preclinical signs of intoxication.

To characterise the relation between pharyngeal anatomy and sleep related disordered breathing, 17 men with complaints of snoring were studied by all night polysomnography. Ten of them had obstructive sleep apnoea (mean (SD) apnoea-hypopnoea index 56 3 (41-7), age 52 (10) years, body mass index 31-4 (5 3) kg/m2); whereas seven were simple snorers (apnoea-hypopnoea index 6-7 (4 6), age 40 (17) years, body mass index 25-9 (4-3) kg/m2). The pharynx was studied by magnetic resonance imaging in all patients and in a group of eight healthy subjects (age 27 (6) years, body mass index 21P8 (2 2) kg/m2, both significantly lower than in the patients; p < 0 05). On the midsagittal section and six transverse sections equally spaced between the nasopharynx and the hypopharynx several anatomical measurements were performed. Results showed that there was no difference between groups in most magnetic resonance imaging measurements, but that on transverse sections the pharyngeal cross section had an elliptic shape with the long axis oriented in the coronal plane in normal subjects, whereas in apnoeic and snoring patients the pharynx was circular or had an elliptic shape but with the long axis oriented in the sagittal plane. It is suggested that the change in pharyngeal cross sectional shape, secondary to a reduction in pharyngeal transverse diameter, may be related to the risk of developing sleep related disordered breathing.

No abstract

Several organs (lung, skin, thyroid, heart, bone marrow) (British Joumnal ofIndustrial Medicine 1993;50:835-842)

Increased upper airways (UA) collapsibility has been implicated in the pathogeny of sleep-disordered breathing (SDB). An increased UA instability during expiration has recently been shown in healthy subjects. The present study assessed UA collapsibility in SDB patients by applying negative pressure during expiration.Full-night polysomnography was performed in 16 subjects (all snorers) with a wide range of SDB, and in six healthy control subjects. Physical examination, spirometry, and maximal inspiratory and expiratory flow rates were within normal limits for all 22 subjects. Negative expiratory pressure (NEP) (-5 cmH 2 O) was applied during quiet breathing in seated and supine position. Flow limitation (FL) during NEP was expressed as the percentage of tidal volume during which expiratory flow was less than or equal to the flow recorded during quiet breathing (%FL).The mean desaturation index (DI) of the 16 subjects was 27.3 26.4 ( SD) and the average FL in supine position was 38.4 37.9%. A close correlation between %FL supine during wakefulness and DI during sleep (r=0.84, p<0.001) was found. All obstructive sleep apnoea subjects had >30%FL supine. There was no FL in the six control subjects.In conclusion, negative expiratory pressure application during expiration appears to be a useful, noninvasive method for the evaluation of subjects with sleep-disordered breathing. Present results suggest that upper airway collapsibility can be detected in these subjects during wakefulness.

WE studied eight Belgian subjects well advanced in the practice of hatha-yoga and compared them with eight sex-, age-, and height-matched control subjects. Practice of yoga (range 4-12 yr) involves control of posture and manipulation of breathing, including slow near-vital capacity maneuvers accompanied by apnea at end inspiration and end expiration. Average values for the yoga and the control group (in parentheses) are as follows: ventilation (VE) 5.53 1 X min-1 (7.07); tidal volume (VT), 1.03 liters (0.56); rate of breathing, 5.5 min-1 (13.4); end-tidal PCO2, 39.0 Torr (35.3). All differences are significant (P less than 0.05). Ventilatory response to CO2 (rebreathing technique) was significantly lower in the yoga group (P less than 0.01). The regression relating VE to VT during rebreathing of CO2 was VE = 8.1 (VT - 0.23) for the yoga group and VE = 15.8 (VT - 0.16) for the control group (P less than 0.005). We attribute these changes to chronic manipulation of respiration.

We measured respiratory mechanical characteristics during sleep in five heavy, nonapneic snorers (HS) and in five obstructive sleep apnea (OSA) patients. In two HS and in two OSA patients we obtained lateral pharyngeal cineradiographic images during sleep while snoring. Flow limitation preceded all snores in both HS and OSA. Pattern of snoring, hysteresis and temporal relationship between supraglottic pressure (Psg) and flow rate were different in HS and OSA. Maximal flow during snoring was less (p less than 0.05) in OSA (0.18 +/- 0.07 liter/second) than in HS (0.36 +/- 0.06 liter/second). Linear supraglottic resistance during inspiratory snoring was higher, though not significantly, in OSA patients (7.11 +/- 3.01 cm H2O/liter/second) than in HS (4.80 +/- 2.83 cm H2O/liter/second). We conclude that: 1) Snoring is characterized by high frequency oscillations of the soft palate, pharyngeal walls, epiglottis and tongue. 2) Flow limitation appears to be a sine qua non for snoring during sleep. 3) The pattern of snoring is different in OSA and HS. 4) Pharyngeal size during snoring is probably larger in HS than in OSA patients.