Comparison of acoustic and impedance methods with mask capnometry to assess respiration rate in obese patients recovering from general anaesthesia

Abstract

SummaryRespiratory depression, a potentially serious complication after general anaesthesia, can be detected promptly by close monitoring of both oxygen saturation and respiratory rate. Obese patients have morphological changes that may impair the reliability of monitoring devices. In this study, respiration rate was simultaneously recorded every second for up to 60 min using a computer in 30 adult obese patients (body mass index ≥ 35 kg.m À2 ), by three methods: acoustic; thoracic impedance; and capnometry via a facemask (Capnomask â , reference method). Of the 99 771 data triplets collected, only 85 520 (86%) were included; 12 021 (84%) were not studied due to failure of capnometry and 2240 (16%) due to failure of the acoustic method. Compared with capnometry, bias was similar using both the acoustic method and impedance (À0.3 bpm vs À0.6 bpm, respectively, p = 0.09), but limits of agreement were narrower for the acoustic method (AE3.5 bpm vs AE5.3 bpm, respectively, p = 0.0008). The proportion of respiration rate values obtained with the acoustic method and impedance that differed by at least 10% or 20% for more than 15 s were 11% vs 23% and 2% vs 6%, respectively (p = 0.0009 for both comparisons). The acoustic sensor was well tolerated, while the facemask was pulled off on several occasions by four (13%) agitated patients. In obese patients requiring close monitoring of respiration rate, the acoustic method may be more precise than thoracic impedance and better tolerated than capnometry with a facemask.

Acoustic method respiratory rate monitoring is useful in patients under intravenous anesthesia

“…Capnography using a nasal or facial interface is a useful technique [13][14][15]. Recently, the acoustic method for respiratory rate monitoring has been used in post-anesthesia care units, intensive care units, and in the operating room under laryngeal mask airway general anesthesia [4,5,[16][17][18]. Thus, we compared the acoustic method with capnography during non-intubated intravenous general anesthesia for dental procedures.…”

Advanced Monitoring Is Associated with Fewer Alarm Events During Planned Moderate Procedure-Related Sedation

“… 37 An acoustic monitor of respiratory rate has been found to have acceptable agreement with Et co 2 in nonintubated patients. 31 , 38 – 40 Processed electroencephalography has been used to assess drug-induced cerebral suppression 41 and could have a role in monitoring depth of sedation. 42 …”

The effect of dental scaling noise during intravenous sedation on acoustic respiration rate (RRa™)

“…Studies of RRa report that it is a reliable method for respiratory monitoring in patients undergoing extubation in the recovery room after general anesthesia [ 12 13 ], patients in the intensive care unit [ 14 ], patients in the emergency department [ 15 ], and patients undergoing dental treatment under sedation [ 7 ]. Studies also report that there is no significant difference in accuracy, compared with capnography or impedance pneumography [ 16 17 18 ].…”