Nasal versus full face mask for noninvasive ventilation in chronic respiratory failure.

This study was undertaken to determine the efficacy of nasal mask (NM) versus full face mask (FFM) for the delivery of noninvasive ventilation (NIV) in subjects with nocturnal hypoventilation. A total of 16 patients (11 males) were enrolled, all with nocturnal hypoventilation currently treated at home with NIV via pressure preset devices. Subjects underwent full polysomnography on three occasions; on the first night current therapy on NM was reviewed, followed by two experimental studies in randomised order using either NM or FFM. NIV settings and oxygen flow rate were the same under both conditions. Notably, 14 of the 16 subjects required the use of a chinstrap to minimise oral leak. Apnoea-hypopnoea indices were within normal limits under both conditions (1.7 +/- 3.4 NM versus 1.6 +/- 2.4 h FFM). The type of interface did not significantly affect gas exchange during sleep (minimum average arterial oxyhaemoglobin saturation total sleep time 93.4 +/- 2.1 NM versus 92.8 +/- 2.5% FFM, Delta transcutaneous carbon dioxide nonrapid eye movement sleep to rapid eye movement sleep (0.58 +/- 0.36 NM versus 0.50 +/- 0.40 kPa FFM). Sleep efficiency was significantly reduced on the FFM (78 +/- 9 NM versus 70 +/- 14% FFM), although arousal indices were comparable under both conditions (15.6 +/- 9.8 NM versus 15.8 +/- 8.8 h FFM). Full face masks appear to be as effective as nasal masks in the delivery of noninvasive ventilation to patients with nocturnal hypoventilation. However, a chinstrap was required to reduce oral leak in the majority of subjects using the nasal mask.

Sleep hypoventilation in hypercapnic chronic obstructive pulmonary disease: prevalence and associated factors.

Sleep hypoventilation (SH) may be important in the development of hypercapnic respiratory failure in chronic obstructive pulmonary disease (COPD). The prevalence of SH, associated factors, and overnight changes in waking arterial blood gases (ABG), were assessed in 54 stable hypercapnic COPD patients without concomitant sleep apnoea or morbid obesity. Lung function assessment, anthropomorphic measurements, and polysomnography with ABG measurement before and after sleep were conducted in all patients. Transcutaneous carbon dioxide tension (Pt,CO2) was measured in sleep, using simultaneous arterial carbon dioxide tension (Pa,CO2) for in vivo calibration and to correct for drift in the sensor. Of the patients, 43% spent > or = 20% of sleep time with Pt,CO2 > 1.33 kPa (10 mmHg) above waking baseline. Severity of SH was best predicted by a combination of baseline Pa,CO2, body mass index and per cent rapid-eye movement (REM) sleep. REM-related hypoventilation correlated significantly with severity of inspiratory flow limitation in REM, and with apnoea/hypopnoea index. Pa,CO2 increased mean+/-SD 0.70+/-0.65 kPa (5.29+/-4.92 mmHg) from night to morning, and this change was highly significant. The change in Pa,CO2 was strongly correlated with severity of SH. Sleep hypoventilation is common in hypercapnic chronic obstructive pulmonary disease, and related to baseline arterial carbon dioxide tension, body mass index and indices of upper airway obstruction. Sleep hypoventilation is associated with significant increases in arterial carbon dioxide tension night-to-morning, and may contribute to long-term elevations in arterial carbon dioxide tension.

Ventilation of sheep and goat barns.

Good ventilation is an important part of any livestock housing system. It may be accomplished by either natural or mechanical means. Generally, except for buildings that must be kept at warm, nonfluctuating temperatures, naturally ventilated cold housing is satisfactory for sheep and goats provided it is dry and draft-free in pen and resting areas, and air exchange is taking place at a rate high enough to remove moisture, gases, and airborne disease organisms from the building. Understanding the importance of site location, building orientation, and principles of ventilation design increases the likelihood of successful barn ventilation.

Behaviour of turnip yellow mosaic virus nucleoproteins under alkaline conditions.

A modified CsCl density gradient procedure is described by which purified preparations of turnip yellow mosaic virus (TYMV) can be fractionated to give 12 nucleoprotein components. When the B1 nucleoprotein is subjected to pH 11.5-11.6 in 1 M KCl (conditions under which artificial empty protein shells are formed), the apparent radius (r) of the virus increases from about 14.6 to 15.2 nm within 30 sec. The increase in r is most probably due to swelling of the particles. Escape of the RNA from these particles is completed in 3-10 min, while RNA degradation continues for at least 30 min. On return to pH 7.0, r returns to about 14.6 nm. When any of the minor nucleoprotein fractions containing less than the full complement of RNA are subjected to the above conditions, the RNA does not escape from the particle. Experiments with the B0 components also showed that these particles did not give an increase in r, although the RNA was degraded to about the same extent as that of the B1 nucleoprotein.