In man assuming the straight position, end-tidal gradient in the lung was modelled using nine lung segments. monitor of during cardiovascular resuscitation (Blumenthal & Voorhees, 1997). We regarded as the postural decrease in can contribute to hypocapnia. Earlier studies have focused on the effect of gravity and body position within the distribution of air flow (Zardini & Western, 1966; Bryan 1966; Milic-Emili 1966), perfusion (Western & Dollery, 1959; Anthonisen & Milic-Emili, 1966) and the ventilationCperfusion (1963; Musch 2002) in the lung. Gravity induces a perfusion gradient in the upright lung, having a decrease in lung perfusion in apical areas and an increase in perfusion in basal areas. In the standing up subject, air flow expired from alveoli active in gas exchange is definitely diluted by air flow from apical lung segments which are relatively underperfused, resulting in a decrease in 1995; Cencetti 1997; Novak 1998; Harms 191089-60-8 2000; Hughson 2001; Edwards 2002), which is definitely affected by mismatch determine the decrease in ratios are modelled for each lung compartment, accounting for effects of gravity. Input data to the model are Fick-calibrated breath-to-breath SV of the heart, pulmonary O2 uptake (1963), we arranged the model gradient. Furthermore, on going from supine to upright respiratory 1962; Rea 1977). Bjurstedt (1962) founded an increase in (2001) for which informed consent had been from all participants, and which was authorized by the ethics committee of Copenhagen (KF 01-120/96) and was performed in accordance with the guidelines laid down in the Declaration of Helsinki. Instrumentation occurred as previously explained; after 5 min of supine rest, each subject actively assumed the upright position and remained standing up for 5 min while continuous finger arterial blood pressure (ABP) and breath-to-breath online gas concentrations were recorded. The data we analysed were from a recording of each subject standing up just once. For the purpose of tracking short-term 1999; Harms 1999). Cardiac output was the 191089-60-8 product of SV and HR. To obtain complete ideals of to calibrate Modelflow was from arterial and central venous O2 content and the were used to calibrate Modelflow to hypocapnia in the standing up position, the following protocol was carried out in seven healthy nonsmoking subjects (aged 29 5 years, height 176 8 cm, excess weight 71 11 kg). Informed consent was from all participants. 191089-60-8 The study was authorized by the ethics committee of the Academic Medical Center (MEC 01-147) and performed in accordance with the guidelines laid down in the Declaration of Helsinki. First, the effect of increased air flow was eliminated by using a protocol that involved standing up during controlled deep 191089-60-8 breathing. Second, we eliminated the effect of mismatch, FRC increase and increased air flow. To achieve this we used a protocol involving standing up with inflated lower leg splints (Pneumasplint, International deposit Nr. 844181), which augment venous return, followed by quick lower leg splint deflation, with deep breathing frequency and were carried out at the beginning and end of each process using the inert gas rebreathing technique (Innocor Magic size: SpO2 & O2 options; Gabrielsen 2002). Rebreathing episodes were designated and Modelflow was level-corrected. The sum of FRC and on model output (M-parameter sensitivity, which was determined starting with 200 s steady-state supine settings, followed by 900 s with upright settings. Steady-state values were: =supine. The output value used in the analysis was M-test. Agreement between test. A value < 0.05 was considered to indicate a statistically significant difference. Results Input to the model The group average haemodynamic and ventilatory reactions to standing up from Bivalirudin Trifluoroacetate the test database are given in Table 2. Upon standing up, decreased from 6.5 1.1 l min?1 to 4.0 0.9 l min?1 in the standing up position. The response ranged from ?0.6.