Journal of clinical monitoring and computing
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J Clin Monit Comput · Jan 2000
ReviewAssessment and monitoring of flow limitation and other parameters from flow/volume loops.
Flow/volume (F/V) spirometry is routinely used for assessing the type and severity of lung disease. Forced vital capacity (FVC) and timed vital capacity (FEV1) provide the best estimates of airflow obstruction in patients with asthma, chronic obstructive pulmonary disease (COPD) and emphysema. Computerized spirometers are now available for early home recognition of asthma exacerbation in high risk patients with severe persistent disease, and for recognition of either infection or rejection in lung transplant patients. ⋯ Finally, the mechanism of ventilatory constraint can be identified with the use of exercise tidal volume F/V loops referenced to maximum F/V loops and static lung volumes. Patients with severe COPD show inspiratory F/V loops approaching 95% of total lung capacity, and flow limitation over the entire expiratory F/V curve during light levels of exercise. Surprisingly, patients with a history of congestive heart failure may lower lung volume towards residual volume during exercise, thereby reducing airway diameter and inducing expiratory flow limitation.
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J Clin Monit Comput · Jan 2000
Randomized Controlled Trial Clinical TrialDoes monitoring of post-tetanic count prevent alarms of airway pressure or visible muscle activity during intratracheal jet ventilation? A prospective study with five different neuromuscular blocking agents.
Profound neuromuscular block (NMB) quantified by post-tetanic count (PTC) may prevent all muscle activity during anesthesia. We studied whether monitoring of PTC prevents airway pressure alarms or visible movements of the vocal cords and the abdomen during endolaryngeal procedures (ELPs). ⋯ PTC-monitoring following 50 Hz stimulation does not ensure total inactivity of muscles during alfentanil-propofol anesthesia, regardless which relaxant has been chosen. During ELPs, simultaneous observation of the vocal cords and the abdomen is more sensitive in detecting early recovery of NMB compared to our method of airway pressure monitoring.
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J Clin Monit Comput · Jan 2000
Clinical TrialMonitoring of respiratory rate in postoperative care using a new photoplethysmographic technique.
Photoplethysmography (PPG) is a non-invasive optical technique that measures variations in skin blood volume and perfusion. The PPG signal contains components that are synchronous with respiratory and cardiac rhythms. We undertook this study to evaluate PPG for monitoring patients' respiratory rate in the postoperative care unit, using a new prototype device. We compared it with the established technique, transthoracic impedance (TTI). ⋯ Our results indicate that PPG has the potential to be useful for monitoring respiratory rate in the postoperative period.
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J Clin Monit Comput · Jan 2000
ReviewAtelectasis formation during anesthesia: causes and measures to prevent it.
Pulmonary gas exchange is regularly impaired during general anaesthesia with mechanical ventilation. This results in decreased oxygenation of blood. A major cause is collapse of lung tissue (atelectasis), which can be demonstrated by computed tomography but not by conventional chest x-ray. ⋯ In summary, atelectasis is present in most humans during anaesthesia and is a major cause of impaired oxygenation. Avoiding high fractions of oxygen in inspired gas during induction and maintenance of anaesthesia may prevent formation of atelectasis. Finally, intermittent "vital capacity"-manoeuvres together with PEEP reduces the amount of atelectasis and pulmonary shunt.
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J Clin Monit Comput · Jan 2000
The effect of single twitch and train-of-four stimulation on twitch forces during stable neuromuscular block.
We investigated whether the response to a single twitch (ST) stimulus or the first response (T1) to a train-of-four (TOF; 4 stimuli at 2 Hz) stimulus following a stimulus interval of 10 s (i.e., the time between two consecutive ST or TOF stimuli) is influenced by the preceding stimulus in the presence of a stable 50% neuromuscular block. In addition, we determined whether ST and TOF stimulation yield different results under these circumstances. ⋯ The ST or T1 force during stimulation with a stimulus interval of 10 s or more during a stable 50% neuromuscular block in the tibialis anterior muscle of the cat is not affected by the preceding stimulus. In addition, ST and T1 forces do not differ when employing a stimulus interval of 10 s or more under these circumstances. Our results thus indicate that the known differences between ST and T1 forces after a bolus injection of a muscle relaxant can not be explained by differences in acetylcholine release when the stimulus interval exceeds 10 s.