Noninvasive determination of upper airway resistance and flow limitation

Abstract

We have shown that a polynomial equation, FP = AP3 + BP2 + CP + D, where F is flow and P is pressure, can accurately determine the presence of inspiratory flow limitation (IFL). This equation requires the invasive measurement of supraglottic pressure. We hypothesized that a modification of the equation that substitutes time for pressure would be accurate for the detection of IFL and allow for the noninvasive measurement of upper airway resistance. The modified equation is Ft = At3 + Bt2 + Ct + D, where F is flow and t is time from the onset of inspiration. To test our hypotheses, data analysis was performed as follows on 440 randomly chosen breaths from 18 subjects. First, we performed linear regression and determined that there is a linear relationship between pressure and time in the upper airway (R2 0.96 +/- 0.05, slope 0.96 +/- 0.06), indicating that time can be a surrogate for pressure. Second, we performed curve fitting and found that polynomial equation accurately predicts the relationship between flow and time in the upper airway (R2 0.93 +/- 0.12, error fit 0.02 +/- 0.08). Third, we performed a sensitivity-specificity analysis comparing the mathematical determination of IFL to manual determination using a pressure-flow loop. Mathematical determination had both high sensitivity (96%) and specificity (99%). Fourth, we calculated the upper airway resistance using the polynomial equation and compared the measurement to the manually determined upper airway resistance (also from a pressure-flow loop) using Bland-Altman analysis. Mean difference between calculated and measured upper airway resistance was 0.0 cmH2O x l(-1) x s(-1) (95% confidence interval -0.2, 0.2) with upper and lower limits of agreement of 2.8 cmH2O x l(-1) x s(-1) and -2.8 cmH2O x l(-1) x s(-1). We conclude that a polynomial equation can be used to model the flow-time relationship, allowing for the objective and accurate determination of upper airway resistance and the presence of IFL.

Inspiratory airflow dynamics during sleep in irritable bowel syndrome: a pilot study

“…From this observation, we suspect that the presence of the supraglottic catheter during the second PSG led to decreased pharyngeal collapsibility of these three participants, eliminating IFL from their studies. To avoid this potential problem in future research, we are examining methods for reliably identifying flow-limited breathing without a supraglottic pressure catheter [13,23,24].…”

Automatic classification of inspiratory flow limitation assessed non-invasively during sleep

“…The non-invasive IFL classifiers presented here were tested on an overall of 8000 breaths, which is up to a fivefold increase in the number of test breaths than in previous studies [3,10,11]. This fact underlines the robustness of the automatic system presented here.…”

“…1) has been considered to contain information on the variation in upper airway (UA) resistance causing IFL [2][3][4][5][9][10][11]. Thus, the flow contour is a key element for a successful non-invasive classification of IFL.…”

“…This work was supported in part by the Grant 2007FIC00933 of the Generalitat de Catalunya, Spain, and by the Spanish Ministerio de Educación y Ciencia under grant TEC2007-68076-C02-01. C. Morgenstern cumbersome and time-consuming procedure, so several methods for non-invasive estimation of IFL and/or automatic flow contour classification [3,[10][11][12] have been recently proposed with mixed results.…”

Upper Airway Resistance Syndrome - A Twenty-Five Years Experience

“…The shape of the inspiratory flow contour has been proposed as a noninvasive predictor of increased upper airway obstruction, increasing the potential for erroneous classification of respiratorye events (Hosselet 1998;Rees 2000;Ayyapa & Rapoport 2003). Various definitions of airflow limitation exist (Norman 2007;Mansour 2004;Kaplan 2000;Aittokallio 2001) (Table 2). RERA is the most important event in UARS patients.…”