Terminology and the current limitations of time capnography: A brief review

Abstract

The carbon dioxide (CO2) trace versus time (time capnography) is convenient and adequate for clinical use. This is the method most commonly utilized in capnography. However, the current terminology in time capnography has not yet been standardized and is, therefore, a potential source of confusion. Standard terminology that is based on convention and logic to represent the various phases of a time capnogram is essential. The time capnogram should be considered as two segments: an inspiratory segment and an expiratory segment. The inspiratory segment is termed as phase ); the expiratory segment is divided into phases I, II, III, and, occasionally, IV. Phase I represents the CO2-free gas from the airways (anatomical dead space); phase II consists of a rapid S-shaped upswing on the tracing due to mixing of dead space gas with alveolar gas; and phase III, the alveolar plateau, represents CO2-rich gas from the alveoli. The physiologic basis of phase IV, the terminal upswing at the end of phase III, which is observed in capnograms recorded under certain circumstances (such as in pregnant subjects and obese subjects) is discussed in detail. The clinical implications of the alpha angle, which is the angle between phases II and III, and the beta angle, which is the angle between phases III and the descending limb of phase 0, are outlined. The subtle but important limitations of time capnography are reviewed; its current status as well as its future potential are explored.

Correlations between capnographic waveforms and peak flow meter measurement in emergency department management of asthma

“…This runs the risk of analysing waveforms that may not be indicative of the situation or having too few waveforms to analyse. Secondly, as Goldman and Landis have proposed, recognition of the different waveform morphologies, either through neural network algorithms or as clusters of morphologically similar waveforms, can be programmed [20–22]. On the whole, this will reduce the influence of waveforms with artefacts or sub-optimal waveforms and this may then form the basis of waveform selection for analysis.…”

Sleep-disordered breathing in nonobese diabetic subjects with autonomic neuropathy

“…Although arterial Pa,CO 2 was not measured in these subjects, it is widely accepted that, in the absence of lung disease and in the presence of an adequate "plateau", as in the diabetics in this study, Pet,CO 2 reflects satisfactorily alveolar CO 2 pressure and, thus, Pa,CO 2 [45].…”

“…Twenty-six adult diabetic patients, 18 with autonomic neuropathy (DANz; age 45 (95% confidence interval (CI) [41][42][43][44][45][46][47][48][49][50] yrs, body mass index (BMI) 24.1 (22)(23)(24)(25)(26) kg?m -2 ) and eight without autonomic neuropathy (DAN-; age 45 yrs, BMI 24.8 (23)(24)(25)(26) kg?m -2 ), were consecutively recruited from the Dipartimento di Medicina Interna e Scienze Endocrine e Metaboliche (DiMISEM) of the University of Perugia (Perugia, Italy) (table 1). The subjects were enrolled after they had given fully informed consent and all subjects completed the study.…”

Capnography Use In The Emergency Department

“…Bu açılar solunum sistemi patolojilerini değerlendirmede kullanılmaktadır. [10,11] Teknoloji Solunum havasında CO 2 ölçümünde kütle spektrometre, moleküler korelasyon spektrometre, raman spektrometre, fotoakustik spektrometre gibi yöntemler kullanılabilse de günümüzde en çok tercih edilen yöntem kızılötesi spektrometre yöntemidir. Kızılötesi spektrometre tekniğinde, kızı-lötesi ışık gaz örneğinin içinden geçirilir ve fotodedektörle kaydedilir (Şekil 3).…”