During invasive mechanical ventilation due to the dryness of medical gases is necessary to provide an adequate level of conditioning. The hot water humidifiers (HWH) heat the water, thus allowing the water vapor to heat and humidify the medical gases. In the common HWH there is a contact between the medical gases and the sterile water, thus increasing the risk of patient's colonization and infection. Recently to avoid the condensation in the inspiratory limb of the ventilator circuit, new heated ventilator circuits have been developed. In this in vitro study we evaluated the efficiency (absolute/relative humidity) of three HWH: (1) a common HWH without a heated ventilator circuit (MR 730, Fisher&Paykel, New Zeland), (2) the same HWH with a heated ventilator circuit (Mallinckrodt Dar, Italy) and (3) a new HWH (DAR HC 2000, Mallinkckrodt Dar, Italy) with a heated ventilator circuit in which the water vapor reaches the medical gases through a gorotex membrane, avoiding any direct contact between the water and gases. At a temperature of 35°C and 37°C the HWH and heated tube were evaluated.The absolute humidity (AH) and relative humidity (RH) were measured by a psychometric method. The minute ventilation, tidal volume respiratory rate and oxygen fraction were: 5.8 ± 0.1 l/min, 740 ± 258 ml, 7.5 ± 2.6 bpm and 100%, respectively. Ventilator settings were maintained constant for all the study period. The measurements were taken after 60 min of continuous use.At 35°C the output of the MR 730 with a heated tube was insufficient to provide adequate levels of conditioning, while at 37°C all the three devices were satisfactory. Table 1 Results as mean ± SD MR 730 heated tube Dar HC MR 730 Set temperature, 35°C AH (mgH 2 O/l) 26.7 ± 0.3* 37.4 ± 0.6 38.0 ± 0.9 RH (%) 83.7 ± 1.0* 97.7 ± 1.4 93.2 ± 1.5 Set temperature, 37°C AH (mgH 2 O/l) 34.5 ± 1.6* 38.7 ± 2.2 † 43.1 ± 1.1 RH (%) 91.8 ± 3.2 87.7 ± 7.4 † 94.6 ± 0.9 *P < 0.05 vs DAR HC and MR 730, † P < 0.05 vs MR 730.

Studies on head injury-induced pituitary dysfunction are limited in number and conflicting results have been reported. To further clarify this issue, 29 consecutive patients (24 males), with severe (n = 21) or moderate (n = 8) head trauma, having a mean age of 37 ± 17 years were investigated in the immediate post-trauma period. All patients required mechanical ventilatory support for 8-55 days and were enrolled in the study within a few days before ICU discharge. Basal hormonal assessment included measurement of cortisol, corticotropin, free thyroxine (fT4), thyrotropin (TSH), testosterone (T) in men, estradiol (E2) in women, prolactin (PRL), and growth hormone (GH). Cortisol and GH levels were measured also after stimulation with 100 µg human corticotropin releasing hormone (hCRH) and 100 µg growth hormone releasing hormone (GHRH), respectively. Cortisol hyporesponsiveness was considered when peak cortisol concentration was less than 20 µg/dl following hCRH. TSH deficiency was diagnosed when a subnormal serum fT4 level was associated with a normal or low TSH. Hypogonadism was considered when T (males) or E2 (women) were below the local reference ranges, in the presence of normal PRL levels. Severe or partial GH deficiencies were defined as a peak GH below 3 µg/l or between 3 and 5 µg/l, respectively, after stimulation with GHRH. Twenty-one subnormal responses were found in 15 of the 29 patients (52%) tested; seven (24%) had hypogonadism, seven (24%) had cortisol hyporesponsiveness, five (17%) had hypothyroidism, and two patients (7%) had partial GH deficiency. These preliminary results suggest that a certain degree of hypopituitarism occurs in more than 50% of patients with moderate or severe head injury in the immediate post-trauma period, with cortisol hyporesponsiveness and hypogonadism being most common. Further studies are required to elucidate the pathogenesis of these abnormalities and to investigate whether they affect long-term morbidity. P2 Cortisol reserve in head trauma victims: evaluation with the low-dose (1 µ µg) corticotropin (ACTH) stimulation test