0000000000205384
AUTHOR
Friedrich Mertzlufft
Arterial O2-Partial Pressure at Positve Endexpiratory Pressure in Hyperoxia for Verification of Patent Foramen Ovale?
As a rule, during anaesthesia a time dependent increase in pulmonary shunting occurs even in states of normal lung function. Therefore positive end-expiratory pressure ventilation (PEEP) is often used to decrease intrapulmonary right/left shunting (RL shunt) and thus to increase arterial O2 partial pressure (paO2) without increasing the inspiratory oxygen fraction.
Blood CO2 and pH Transients During Apnoea after O2 Breathing in Patients
Endotracheal intubation always is combined with an apnoea the duration of which is dependent on the technique used, the skills of the intubator, and the anatomical situation. The resulting typical potential risks may be (among others) both hypoxaemia and hypercapnia. Therefore the tolerable apnoea time for an intubation procedure is limited in clinical practice to 1 – 2 minutes. It must be noted that the developing hypercapnia is inevitable, whereas hypoxaemia may be avoided even in prolonged apnoea (e.g. >2 min) with “adaequate” preoxygenation [Duda et al., 1988]. Using de-nitrogenation techniques (breathing pure oxygen for 30 to 60 min) “anaesthetized and curarized normal subjects tolerat…
Accuracy of delivered versus preset minute ventilation of portable emergency ventilators.
The accuracy of delivered minute volume (VE) ventilation of portable emergency ventilators (PEV) was evaluated. Five PEV from three manufacturers were adapted to an artificial lung for varying compliance and resistance. Each PEV was tested in the "no airmix" (pure oxygen) and "airmix" (approximately 60% oxygen) setting at different frequencies and VE. Measurement of delivered VE (VEdel) was made using a pneumotachograph and digital integration of the flow values greater than 1 min (maximal error +/- 2%). Maximal inspiratory pressure (Pinsp) was measured with a transducer. Two PEV from one manufacturer produced severe hyperventilation when used at low VE (i.e., in children). Two other PEV fr…
Normal Values of Oxygen Concentration in Human Blood
Under physiological conditions, the oxygen supply as the product of O2-concentration (mlO2/dl; %(v/v)) and perfusion is influenced by many factors (cf. Fig. 1): perfusion on one hand, oxygen partial pressure (pO2; mmHg), haemoglobin (Hb) concentration (g/dl) and O2 binding power of Hb on the other hand. Under pathological conditions, oxygen supply disturbances are related to hypoxemia, i.e. reduction of O2-concentration in the blood. The differential diagnosis of hypoxemia includes normoxic, hypoxic and circulatoric disturbances of oxygen supply (cf. Fig. 1). Thus it is necessary to describe a NORMOXIC HYPOXEMIA (anemic or toxemic), a HYPOXIC HYPOXEMIA (decreased O2-concentration caused by …