Biology subjects

Hurr, T. J.

Publications and source records attributed to Hurr, T. J..

2 recordsLinked to original sources

bioRxiv2025

Graphical examples used to show why caution is required if using the coefficient of determination (R2) to interpret data for medical case reports.

A patient with a medical condition can have medical tests or symptoms scored that generate numerical results before a treatment, during a treatment or after a treatment, usually over several days, to determine if any benefits have occurred. The changes in the numerical measurements or scores over time can be readily plotted using computer software to show an equation for the line of best fit for either linear or log equations, together with the coefficient of determination (R2). Despite the ease of generating this type of graphical representations caution is required in interpreting the R2 value with reference to medical case reports. To understand why this is so, at a basic level, four scenarios using hypothetical patient scores were used to generate scatter plots showing the equation for the line of best fit and R2 values with comparison to the average and standard deviation (SD) values. The graphical examples are used to supplement the more complex mathematical and statistical explanations and choice for effect measures that are available. It was found R2 values for log equations for the line of best fit did not follow a trend with increasing treatment days. For linear equations, higher R2 value may not necessarily correspond to a lower standard deviation (SD) value for the averaged scores. The R2 value can be influenced by the day on which the scores were recorded, despite the equivalence of the average scores and SD values. R2 values may not indicate the strength of a treatment benefit or the magnitude of scatter between data sets. Score averaging can increase R2 values, while average values remain the same but with the SD value decreasing. The graphical examples shown provide an explanation why line graphs may be the simplest and best option for reporting, particularly non-linear numerical data, in case reports. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=154 HEIGHT=200 SRC="FIGDIR/small/670747v2_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@1ad866org.highwire.dtl.DTLVardef@75282forg.highwire.dtl.DTLVardef@1a1592forg.highwire.dtl.DTLVardef@1e64166_HPS_FORMAT_FIGEXP M_FIG Graphical examples of the line of best fit and R2 values from hypothetical patient scores are compared with average (Av.) and standard deviation (SD) values A. From the line of best fit, Patient 1 has a higher R2 value than Patient 2 even though the average score has a higher SD value. B. Patient 1 records scores on days 6 and 7 and Patient 2 records the same scores on days 9 and 10, yet Patient 1 has a higher R2 value for the line of best fit despite the scores average and SD values being the same. C. For Patients 1 and 2, the R2 values for the line of best fit are the same, despite the score averages and SD values being different and show R2 values do not predict a treatment benefit or allow a comparison of the magnitude of a benefit between data sets. D. Averaging daily scores removes scatter, increasing R2 values however the average scores remain the same, but the SD value ({+/-} 0.51) was reduced despite an identical slope and intercept for the line of best fit. C_FIG

bioinformatics↗

bioRxiv2025

Quantification of the volume of swallowed air in the gut finds low volumes when asleep may reduce aerobic digestion and explain why short dinner to sleep times are associated with nocturnal reflux

It has been previously reported that air swallowing and breathing exercises could reduce the severity of digestive reflux by supplying oxygen directly to the gut lumen and supporting aerobic digestion, however the normal volume of air swallowed over 24 hours has not been determined. To determine the volume of air swallowed over 24 hours, the number of swallows during eating, drinking and snacks (EDS), asleep, at other times awake (OTA) and the volume of air swallowed per bolus were sought from the literature. Four models were developed to determine the volume of air swallowed per bolus, finding volumes between 0 ml and an average maximum pharyngeal volume of 40 ml were possible, with an average and range of values {approx} 11(1.7-32) ml. From a literature search, the number of swallows over 24 hours determined using a microphone, was found to be the most complete set of data to calculate the volumes of air swallowed while EDS, asleep and OTA. There was on average during EDS {approx} 31 ml air swallowed per minute, when asleep {approx} 1 ml air swallowed per minute and at OTA {approx} 4.3 ml air swallowed per minute giving a total air swallow volume of {approx} 6,400(320-47,000) ml air over 24 hours. The volume of the gases contained in swallowed air were also calculated as nitrogen {approx} 5000 ml, oxygen {approx} 1000 ml and noting swallowed air is expired air from the lungs, carbon dioxide {approx} 320 ml over 24 hours. If improved aerobic digestion reduced the probability of digestive reflux and was related to the volume of air swallowed, then digestive reflux would be least likely to occur during EDS, with the highest air swallow rate, followed by OTA and most likely to occur when asleep, when the lowest volume of air is swallowed. The volume of air swallowed over 24 hours was equivalent to only one or two minutes of breathing at {approx} 6,000 ml per minute for an adult at rest. It is still not clear whether luminal oxygen supply from air swallowing, or luminal (and systemic) oxygen supply from breathing, is the major source of oxygen supply to the gut lumen for aerobic digestion, however if air swallowing is the major source of luminal oxygen supply, then air swallowing is likely an important factor for digestive health. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=163 SRC="FIGDIR/small/633483v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@156ef39org.highwire.dtl.DTLVardef@73c778org.highwire.dtl.DTLVardef@12cc39forg.highwire.dtl.DTLVardef@1df2247_HPS_FORMAT_FIGEXP M_FIG C_FIG The low volumes of air swallowed during sleep may reduce aerobic digestion and explain why eating, drinking and snacks less than 3 hours before sleep have been associated with an increased probability of gastric /digestive reflux. The volume of air swallowed per 24 hours is equivalent to only 1-2 minute of breathing at 6,000 ml per minute for an adult at rest. Air swallowing link to reflux diseases [8], air swallow volume per bolus [9-14], rates of swallowing per 24 hours [16] breathing air volumes [35], increased reflux less than 3 hours dinner to sleep [38].

biophysics↗