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Ultrasonography in the intensive care unit: Looking at the world through colored glasses
No full textAbstract
INTRODUCTION:
To investigate haemodynamic and respiratory changes during lung recruitment and decremental positive end-expiratory pressure (PEEP) titration for open lung ventilation in patients with acute respiratory distress syndrome (ARDS) a prospective, clinical trial was performed involving 12 adult patients with ARDS treated in the surgical intensive care unit in a university hospital.
METHODS:
A software programme (Open Lung Tool) incorporated into a standard ventilator controlled the recruitment (pressure-controlled ventilation with fixed PEEP at 20 cmH2O and increased driving pressures at 20, 25 and 30 cmH2O for two minutes each) and PEEP titration (PEEP lowered by 2 cmH2O every two minutes, with tidal volume set at 6 ml/kg). The open lung PEEP (OL-PEEP) was defined as the PEEP level yielding maximum dynamic respiratory compliance plus 2 cmH2O. Gas exchange, respiratory mechanics and central haemodynamics using the Pulse Contour Cardiac Output Monitor (PiCCO), as well as transoesophageal echocardiography were measured at the following steps: at baseline (T0); during the final recruitment step with PEEP at 20 cmH2O and driving pressure at 30 cmH2O, (T20/30); at OL-PEEP, following another recruitment manoeuvre (TOLP).
RESULTS:
The ratio of partial pressure of arterial oxygen (PaO2) to fraction of inspired oxygen (FiO2) increased from T0 to TOLP (120 +/- 59 versus 146 +/- 64 mmHg, P < 0.005), as did dynamic respiratory compliance (23 +/- 5 versus 27 +/- 6 ml/cmH2O, P < 0.005). At constant PEEP (14 +/- 3 cmH2O) and tidal volumes, peak inspiratory pressure decreased (32 +/- 3 versus 29 +/- 3 cmH2O, P < 0.005), although partial pressure of arterial carbon dioxide (PaCO2) was unchanged (58 +/- 22 versus 53 +/- 18 mmHg). No significant decrease in mean arterial pressure, stroke volume or cardiac output occurred during the recruitment (T20/30). However, left ventricular end-diastolic area decreased at T20/30 due to a decrease in the left ventricular end-diastolic septal-lateral diameter, while right ventricular end-diastolic area increased. Right ventricular function, estimated by the right ventricular Tei-index, deteriorated during the recruitment manoeuvre, but improved at TOLP.
CONCLUSIONS:
A standardised open lung strategy increased oxygenation and improved respiratory system compliance. No major haemodynamic compromise was observed, although the increase in right ventricular Tei-index and right ventricular end-diastolic area and the decrease in left ventricular end-diastolic septal-lateral diameter during the recruitment suggested an increased right ventricular stress and strain. Right ventricular function was significantly improved at TOLP compared with T0, although left ventricular function was unchanged, indicating effective lung volume optimisation
Odorant-binding proteins: Structural aspects
No full textStructural data on odorant-binding proteins (OBPs), both in vertebrates and in insects, are reviewed and discussed. OBPs are soluble proteins interacting with odor molecules and pheromones in the perireceptor areas, the nasal mucus in vertebrates and the sensillar lymph in insects. The physiological function of these proteins is still uncertain, but information on their structure is abundant and accurate. Based on complete amino acid sequences, several subclasses have been identified, suggesting a role in odor discrimination. The OBPs of vertebrates belong to the family of lipocalins that includes proteins involved in the delivery of pheromonal messages. Those of insects do not bear significant similarity to any other class of proteins. The three-dimensional structure of the bovine OBP is a beta-barrel, while for insect OBPs a model, has been proposed, mainly containing alpha-helix motifs. In some cases the amino acid residues involved in ligand binding have been identified with the use of photoaffinity label analogues
ODORANT-BINDING PROTEINS
No full textOdorant-binding proteins (OBPs) are low-molecular-weight soluble proteins highly concentrated in the nasal mucus of vertebrates and in the sensillar lymph of insects. Their affinity toward odors and pheromones suggests a role in olfactory perception, but their physiological function has not been clearly defined. Several members of this class of proteins have been isolated and characterized both in insects and vertebrates; in most species two or three types of OBPs are expressed in the nasal area. Vertebrates OBPs show significant sequence similarity with a superfamily of soluble carrier proteins called lipocalins. They include some proteins of particular interest that are thought to be involved in the mechanism of releasing and modulating chemical messages with pheromonal activity. The data on vertebrate OBPs are here reviewed together with the most relevant information on related proteins. Theories and models of the physiological functions of odorant-binding proteins are presented and discussed
ODORANT-BINDING PROTEINS OF THE MOUSE
No full textAfter the isolation of two odorant-binding proteins (OBP-I and OBP-II) from mouse nasal tissue, we have purified two additional OBPs, which bind tritiated 2-isobutyl-3-methoxypyrazine. OBP-III is a homodimer with subunits of M(r) 22,000 and pI 4.2, OBP-IV is a homodimer with subunits of M(r) 21,000 and pI 4.85, N-terminal amino acid sequences indicate that OBP-III is identical in its first 40 amino acids to the mouse urinary protein, MUP-5, (ii) OBP-IV is > 90% identical in its first 30 amino acids to the MUP-4, OBP-II is nearly 80% similar in its first 40 amino acids to OBP-I of the rat, and both subunits of OBP-I are > 50% identical with hamster aphrodisin
PHYSIOLOGICAL FUNCTIONS OF THE ODOR-BINDING PROTEINS
No full textThe chemical characteristics of odorant-binding proteins (OBPs) are summarised and compared with those of other types of binding proteins involved in chemical communication. The recent finding of multiple forms of OBPs in the same animal species could suggest an odour discriminating role for these proteins. In this respect, the vertebrates' olfactory system is similar to other chemoreception systems, such as those present in insects for detecting pheromones and general odours, bacterial chemotaxis and taste
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