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With a normal P a O 2 of 60–100 mmHg and an oxygen content of F I O 2 of 0.21 of room air, a normal P a O 2 /F I O 2 ratio ranges between 300 and 500 mmHg. A P a O 2 /F I O 2 ratio less than or equal to 200 mmHg is necessary for the diagnosis of acute respiratory distress syndrome by the AECC criteria. [7]
Positive end-expiratory pressure (PEEP) is the pressure in the lungs (alveolar pressure) above atmospheric pressure (the pressure outside of the body) that exists at the end of expiration. [1] The two types of PEEP are extrinsic PEEP (PEEP applied by a ventilator) and intrinsic PEEP (PEEP caused by an incomplete exhalation).
The oxygenation index is a calculation used in intensive care medicine to measure the fraction of inspired oxygen (FiO2) and its usage within the body. A lower oxygenation index is better - this can be inferred by the equation itself. As the oxygenation of a person improves, they will be able to achieve a higher PaO2 at a lower FiO2.
The standard definition of a reference range for a particular measurement is defined as the interval between which 95% of values of a reference population fall into, in such a way that 2.5% of the time a value will be less than the lower limit of this interval, and 2.5% of the time it will be larger than the upper limit of this interval, whatever the distribution of these values.
The alveolar oxygen partial pressure is lower than the atmospheric O 2 partial pressure for two reasons.. Firstly, as the air enters the lungs, it is humidified by the upper airway and thus the partial pressure of water vapour (47 mmHg) reduces the oxygen partial pressure to about 150 mmHg.
A high V/Q ratio decreases pCO 2 and increases pO 2 in alveoli. Because of the increased dead space ventilation, the arterial pO 2 is reduced and thus also the peripheral oxygen saturation is lower than normal, leading to tachypnea and dyspnea
Hyperoxia is the state of being exposed to high levels of oxygen; it may refer to organisms, cells and tissues that are experiencing excessive oxygenation, [1] or to an abnormally high oxygen concentration in an environment (e.g. a body of water).
A low PaO 2 indicates that the patient's current minute ventilation (whether high or normal) is not enough to allow adequate oxygen diffusion into the blood. Therefore, the A–a gradient essentially demonstrates a high respiratory effort (low arterial PaCO 2) relative to the achieved level of oxygenation (arterial PaO 2). A high A–a gradient ...