Response time of indirectly accessed gas exchange depends on measurement method

Abstract

Noninvasive techniques are routinely used for assessment of tissue effects of lung ventilation. However, comprehensive studies of the response time of the methods are scarce. The aim of this study was to compare the response time of noninvasive methods for monitoring of gas exchange to sudden changes in the composition of the inspired gas. A prospective experimental study with 16 healthy volunteers was conducted. A ventilation circuit was designed that enabled a fast change in the composition of the inspiratory gas mixture while allowing spontaneous breathing. The volunteers inhaled a hypoxic mixture, then a hypercapnic mixture, a hyperoxic mixture and finally a 0.3% CO mixture. The parameters with the fastest response to the sudden change of O2 in inhaled gas were peripheral capillary oxygen saturation (SpO2) and regional tissue oxygenation (rSO2). Transcutaneous oxygen partial pressure (tcpO2) had almost the same time of reaction, but its time of relaxation was 2-3 times longer. End-tidal carbon dioxide (EtCO2) response time to change of CO2 concentration in inhaled gas was less than half in comparison with transcutaneous carbon dioxide partial pressure (tcpCO2). All the examined parameters and devices reacted adequately to changes in gas concentration in the inspiratory gas mixture.

Commercial smartwatch with pulse oximeter detects short-time hypoxemia as well as standard medical-grade device: Validation study

“…Generally, there are differences between the reaction times of pulse oximeters to sudden hypoxia. 46 During the experiments, we also observed a faster return of smartwatch values than oximeter in the final stabilization phase after the desaturation phase, but not being the primary concern of our study, there were not enough data to evaluate for this.…”

Skin temperature influence on transcutaneous carbon dioxide (CO2) conductivity and skin blood flow in healthy human subjects at the arm and wrist

“…Regarding the response time of tcpCO 2 monitors following a sudden change in paCO 2 , a lag has been reported in the literature between end-tidal pCO 2 -petCO 2 -paCO 2 , and tcpCO 2 , inducing a higher in vivo response time than in the ideal in vitro case. Reported values for this latter lag fall within the 1-5 min range (Kesten et al, 1991;Carter and Banham, 2000;Cuvelier et al, 2005;Rafl et al, 2018). An overall response time requirement of approximatively 5 min can thus de facto be assumed for a tcpCO 2 monitor to meet field expectations.…”