The droplets that are driven into the airstream and into the lung fields are lofted by way of Bernoullis principle. There is also a condition called oxidative damage that occurs when concentrations of pure oxygen come into prolonged contact with cells and this damages the cilia of the cells, thus inhibiting their action as part of the bodys first line of defense. Whether bacteria also travel from the sinuses or the stomach into the lungs is, as of 2005, controversial. However, spread to the lungs from the blood stream or the gut is uncommon. Once inside the lungs, bacteria then take advantage of any deficiencies in the immune system (such as due to malnutrition or chemotherapy) and multiply. Patients with VAP demonstrate impaired function of key immune cells, including the neutrophil, both in the blood and in the alveolar space, with this impairment being driven by pro-inflammatory molecules such as C5a. These defects in immune function appear to be causally linked to the development of VAP, as they are seen before clinical infection develops. A combination of bacterial damage and consequences of the immune response lead to disruption of gas exchange with resulting symptoms. Diagnosis
Diagnosis of ventilator-associated pneumonia is difficult and is not standardized.
Laboratory animal studies are usually cited in the literature. In serious drug dependency (high tolerance), 2000–3000 mg per day can be tolerated. Pharmacology
Pharmacodynamics
Morphine is the prototypical opioid and is the standard against which other opioids are tested. It interacts predominantly with the μ–δ-opioid (Mu-Delta) receptor heteromer. The μ-binding sites are discretely distributed in the human brain, with high densities in the posterior amygdala, hypothalamus, thalamus, nucleus caudatus, putamen, and certain cortical areas. They are also found on the terminal axons of primary afferents within laminae I and II (substantia gelatinosa) of the spinal cord and in the spinal nucleus of the trigeminal nerve.Morphine is a phenanthrene opioid receptor agonist – its main effect is binding to and activating the μ-opioid receptor (MOR) in the central nervous system. Its intrinsic activity at the MOR is heavily dependent on the assay and tissue being tested; in some situations it is a full agonist while in others it can be a partial agonist or even antagonist. In clinical settings, morphine exerts its principal pharmacological effect on the central nervous system and gastrointestinal tract. Its primary actions of therapeutic value are analgesia and sedation. Activation of the MOR is associated with analgesia, sedation, euphoria, physical dependence, and respiratory depression. Morphine is also a κ-opioid receptor (KOR) and δ-opioid receptor (DOR) agonist. Activation of the KOR is associated with spinal analgesia, miosis (pinpoint pupils), and psychotomimetic effects. The DOR is thought to play a role in analgesia.