Measurements in intubated patients

If the patient is fully relaxed measurements of pressure at the airway can be made easily. Flow is commonly measured using a pneumotachograph which consists of a resistor and equipment to measure the small pressure drop across it. The resistor can have a number of different designs and is placed in the gas flow close to the subject's or patient's airway. By introducing a linear resistance, the pressure drop across the resistance is proportional to the flow rate. If the flow signal derived from the pneumotachograph is integrated, volume can be obtained simultaneously. Measurement errors are easily introduced; for example, if the flow past the pneumotachograph is not linear, at a given flow rate the pressure drop will be higher and a greater flow rate will be recorded. This circumstance can occur if dust or secretions occlude the resistor. Therefore it is important to calibrate the flow-measuring equipment accurately before and after use.

Sleep Apnea

Sleep Apnea

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