Monitoring for patients receiving airway pressure therapy

The multitude of monitoring modalities theoretically available at the present time mandates a match of patient requirements to the most applicable technology. Both risk-to-benefit ratios and the most likely pathophysiologic derangements must be considered on an individual basis because currently available devices range from noninvasive monitors providing basic information to invasive research tools. Patients treated with positive pressure ventilation may experience dramatic changes of cardiovascular and pulmonary function secondary to underlying disease or to the effects of therapy. Therefore, basic monitoring applied during positive pressure ventilation must detect major changes in patient condition and warn against malfunction of basic equipment. These basic devices would include ventilatory pressure monitoring, including a disconnection alarm; FIO₂ analysis; continuous ECG display; noninvasive blood pressure measurement; and periodic chest radiography. Pulse oximetry, with its attendant ability to provide early detection of hypoxemia, is probably the greatest addition to monitoring technology in this decade and may become a mandatory monitor for all ventilated patients. A second tier of patient care is represented by those ventilated patients in whom significant and rapid physiologic changes are anticipated. The increased level of risk in these cases justifies the cost and the risk of applying secondary modalities in addition to baseline monitoring. Continuous peripheral artery catheterization, capnography, pulse oximetry, and calculations of pulmonary compliance will allow more accurate titration of therapy and earlier detection of clinical deterioration. A third tier of requirements is primarily represented by those patients with combined cardiac and pulmonary dysfunction in whom evaluation of the interaction between CO and ventilatory support is necessary. Highly invasive and costly technology, such as pulmonary artery catheterization, is justified in critical circumstances. Continuous Sv̄O₂ measurement, transesophageal echocardiography, and cardiac nuclear imaging may be useful in order to provide appropriate fluid, inotropic, and ventilatory support. Transcapillary albumin flux and EVLW may also eventually improve patient care under these circumstances, but they currently remain in the research stage of development. The greatest area of current progress is the proliferation of noninvasive technology. Epitomized by pulse oximetry and capnography, this noninvasive approach to monitoring may ultimat replace many of the traditional invasive modes. Patient morbidity due to iatrogenic complications may decrease, and continuous on-line measurements will aid in rapid titration of therapy. We are witnessing a true technological explosion as evidenced by the multitude of 'horizon' techniques mentioned in the preceding pages, and we can expect further major monitoring refinements and changes in the standard of clinical care during the coming years.