Thermistor-based device may help detect pneumonia
A simple instrument that uses thermistor-based breathing sensors can accurately measure respiratory rate (RR) in children and in adults, holding great potential for diagnosing paediatric pneumonia in low-resource settings, according to a study.
Respimometer is used like an oral thermometer and consists of a mouth piece, an upper lip flap incorporating two thermistors positioned at the nasal outlet, and a lower flap so that it remains in place inside the mouth.
RR is obtained by measuring the temperature waveform of the inhaled/exhaled air at the nasal outlet with the use of thermistors. Readings are shown on a separate LED display box after a fixed 30-second interval.
The authors sought to compare the accuracy of Respimometer measurements against RR values obtained using timed breaths in adults and capnography in children.
In adult volunteers, the device accurately measured RR in the 10–65 min–1 range, in which the correlation coefficient between the delivered RR and the Respimometer measurement was median 0.992 (IQR, 0.980–0.999). Measurement bias, calculated using the Bland-Altman plot, was −0.50 min–1 (95 percent CI, −1.1 to 0.07; p=0.093). [BMJ Innovations 2018;doi:10.1136/bmjinnov-2017-000267]
In children, no evidence of bias was detected (mean difference in RR, 1.0 min−1; −2.1 to 4.1; p=0.52). The upper and lower limits of agreement were −18 and 20 min−1, respectively.
Respimometer provides unbiased measurement of RR in a range that is adequate for the diagnosis of childhood pneumonia, with the threshold defined for tachypnoea being >50 min–1 in children aged 2–12 months and >40 min–1 in those aged 1–5 years, the authors said.
Although further issues (eg, hygiene, cost, portability and acceptability) will need to be addressed prior to additional testing and clinical use of the Respimometer, the initial prototype represents a promising first step towards objective RR measurement in children in low-resource communities in Africa and Asia.
According to the authors, measuring RR in children remains a challenge. Measurement devices that come into contact with the child often cause distress and, in turn, alter the child’s RR. Indeed, during the testing phase, it was noted that some children were frightened by the Respimometer and/or unwilling to keep the device in their mouth.
In contrast, noncontact devices that depend on a health professional or a smartphone to count RR are prone to error, especially in diagnosis, leading to overtreatment and/or undertreatment. Meanwhile, those that are automated such as infrared thermography and radar are expensive high-technology devices that are not appropriate for use in low-resource settings. [Pediatr Pulmonol 2011;46:523-529; J Advs Biomed Eng Techno 2016;3:21–27]
The current Respimometer prototype requires access to electricity and is sterilized using a 70% ethanol solution. The authors plan to create a battery-operated device with a display screen located on the device for the next prototype. Other improvements being explored are as follows: adding an oral temperature sensor to detect fever, enabling simultaneous measurement of multiple vital signs, and increasing child-friendliness and acceptability.
“Given the magnitude of paediatric pneumonia deaths (900,000 per year, globally) concentrated in prehospital settings in low-income and middle-income countries, improving the case management of pneumonia with appropriate technology has the potential for substantial impact on global child survival,” the authors said.