Reader response

Myron Yaster MD

From Proshad Efune, MD, Assistant Professor, Department of Anesthesiology and Pain Management, Department of Pediatrics, University of Texas Southwestern Medical Center and Children's Health, Dallas 

We recently used the ExSpiron®2Xi, a noninvasive respiratory volume monitor, in a study of 60 children with severe OSA having adenotonsillectomy to monitor minute ventilation in the postoperative period, including the first postoperative night. More on this to come when the manuscript is published!

Considering the ExSpiron®2Xi is a non-standard monitor, we also evaluated the feasibility of its use. To start, I should mention that the ExSpiron®2Xi requires calibration against invasive minute ventilation measurements after endotracheal intubation, at least for now, in children. This is easy and simple to do, but if done incorrectly, will result in inaccurate minute ventilation measurements. Feasibility of monitoring was excellent in the PACU, where patients were sedated part of the time, and a PACU nurse and a member of our study team were continuously sitting at the bedside. Monitoring on the postoperative ward was significantly more challenging. Because the bedside nurses were not trained in its use, and in fact blinded to the measurements, we had study staff regularly rounding on the patients overnight to make sure the monitoring was ongoing. Despite this, in four patients the monitor was unplugged and the battery ran out of power. This was not noticed by nursing and several hours of data were lost. In four additional patients, monitor disconnects and misplaced chest sensors were only picked up by study staff during rounds. In several additional patients, monitoring issues were noticed by bedside nursing or parents and either they alerted study staff, or they were able to troubleshoot themselves. In only three patients was the monitor not tolerated. These patients were all under the age of three and all eventually withdrew from the study.  

We believe one of the main reasons why monitoring lapses were not picked up by bedside nurses is because we used the ExSpiron®2Xi as a “stand alone” monitor without connection to the patient monitor. Without a mechanism for monitoring at the nurses’ station, these lapses would only be noticed by the parents or when the nurse had other cause to enter the room. This also means that the monitor would be essentially useless as a clinical monitor of ventilation, unless someone is looking at it frequently at the bedside, or unless parents alert nursing when alarms sound. While alarms can be configured, the default alarm is for minute ventilation < 40% predicted for 30 seconds. We believe outside perhaps the ICU setting, there should be a mechanism for centralized monitoring for the ExSpiron®2Xi to be effective clinically.