Collaborative strategies for teaching common acid-base disorders to medical students

IlluminationsCollaborative strategies for teaching common acid-base disorders to medical studentsMarie Warrer Petersen, Linea Natalie Toksvang, Ronni R. Plovsing, and Ronan M. G. BergMarie Warrer PetersenCentre of Inflammation and Metabolism, Department of Infectious Diseases, University Hospital Rigshospitalet, Copenhagen, Denmark; Intensive Care Unit 4131 University Hospital Rigshospitalet, Copenhagen, Denmark; and , Linea Natalie ToksvangCentre of Inflammation and Metabolism, Department of Infectious Diseases, University Hospital Rigshospitalet, Copenhagen, Denmark; , Ronni R. PlovsingIntensive Care Unit 4131 University Hospital Rigshospitalet, Copenhagen, Denmark; and , and Ronan M. G. BergCentre of Inflammation and Metabolism, Department of Infectious Diseases, University Hospital Rigshospitalet, Copenhagen, Denmark; Renal and Vascular Research Section, Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Copenhagen, DenmarkPublished Online:01 Mar 2014https://doi.org/10.1152/advan.00106.2013MoreSectionsPDF (133 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat the ability to recognize and diagnose acid-base disorders is of the utmost importance in the clinical setting. However, in our experience, medical students often have difficulties learning the basic principles of acid-base physiology in the respiratory physiology curriculum, particularly when applying this knowledge to the analysis of arterial blood gases. Collaborative teaching strategies may enhance student performance in quizzes in undergraduate physiology courses (1, 2). In particular, the so-called peer instruction technique (3) has been reported to enhance both the transfer and retention of learned material in a time-efficient fashion (4). The Harvard professor Eric Mazur originally developed peer instruction for teaching physics to undergraduate students (3). In this teaching approach, specific questions are integrated in the conventional lecture format; in an initial "individual phase," students mark down their answer and rate how confident they are about the correctness of their answer, and this is followed by a "pair phase," where students are asked to convince their neighbor of their answer. After this, they may revise the answer and again rate their confidence in their second answer. This teaching approach may differ substantially from conventional group work, where students typically discuss questions in small groups and mark down their answer during the lecture. In the present study, we attempted to implement and compare conventional group work and Mazur's peer instruction technique for teaching second-year medical students to diagnose common acid-base disorders by arterial blood gas analysis.We obtained institutional approval for the present study from the Faculty of Health Sciences at the University of Copenhagen, and participation was voluntary. A total of 41 second-year medical students participated in a 2-h lesson on acid-base physiology that was conducted on two separate occasions. On the first occasion (group A), students performed conventional group work (n = 22), and, on the second occasion (group B), students performed group work according to Mazur's peer instruction technique (n = 19). Before the lesson, all students reported their age, sex, and preparation time. The two groups were similar with regard to age, sex, and preparation time, with no statistically significant differences between groups (data not shown). The first part of the lesson consisted of a 45-min introduction to the basic principles of acid-base physiology and disorders taught ex cathedra by R. M. G. Berg. The mnemonic rule, "paper cut bleeding" (PCB; pH-CO2-base excess), developed by L. N. Toksvang, was used as a structure to the blood gas analysis. During the lesson, students received a sheet with normal ranges for all arterial acid-base variables and were introduced to a PCB-structured flow chart (Fig. 1). Afterward, M. W. Petersen conducted a 20-min session during which students solved eight different arterial blood gases (Table 1) using two different collaborative strategies: group A interpreted each gas in groups of two in 2 min and rated how confident they felt about the answer. Group B first assessed each arterial blood gas individually for 1 min (individual phase) and rated how confident they were about the answer; students then reassessed the gas in groups of two students for another minute (pair phase) and then rated how confident they were about their second answer. Reference ranges were available during the whole session, and the correct diagnosis was highlighted immediately after the students' assessment of each gas, using the PCB-based flow chart as a visual aid (Fig. 1).Fig. 1."Paper cut bleeding" [pH-CO2-base excess (BE)]-structured flow chart. Students were instructed to 1) assess pH, to identify the presence of acidosis or alkalosis; 2) consider arterial Pco2 (PaCO2), to identify to what extent a respiratory component contributes; and 3) assess BE, to identify to what extent a nonrespiratory component contributes to a given acid-base disorder.Download figureDownload PowerPointTable 1. Arterial blood gasesArterial Po2, kPaArterial O2 Saturation, %Arterial Pco2, kPapHHCO3−, mMBase Excess, mM1. Partially compensated respiratory alkalosis9.8963.57.5123−2.12. No acid-base disorder9.0945.97.38251.13. Combined respiratory and metabolic acidosis10.7936.87.2018−7.34. Partially compensated metabolic acidosis20.7983.27.058−225. Respiratory acidosis without compensation10.29310.37.18230.26. Metabolic acidosis without compensation9.3854.77.1613−15.07. Metabolic alkalosis without compensation13.7985.97.533612.88. Partially compensated respiratory acidosis13.2968.27.33296.39. Respiratory alkalosis without compensation10964.27.4825−0.310. Fully compensated respiratory acidosis9.3947.57.40329.211. Partially compensated metabolic acidosis11.6953.17.2011−18.012. No acid-base disorder13.2985.77.3623−1.4Normal range11.1–14.493–984.5–6.07.35–7.4521–28−2 to 2Gases 1–4 were used in the pretest and posttest and were solved individually by the students. Gases 5–12 were used in the 20-min session of collaborative activities, between the pre- and posttest. Students had access to the normal ranges as listed above; they were informed that these may vary between laboratories and departments, but, to ensure consistency, we instructed them to be rigid in their approach to these ranges when assessing the arterial blood gases during the class.All students underwent an identical test immediately before and after the 20-min session of collaborative activities. The test encompassed four arterial blood gases (Table 1). Students were to complete the test in 8 min. For each arterial blood gas, students reported how confident (from 0% to 100%) they were that their diagnosis was correct. In the analysis of the test results, one point was awarded for each correctly diagnosed acid-base disorder. SAS statistical software (version 9.2, SAS Institute, Cary, NC) was used to compare pre- to posttest scores, to analyze student performance during the 20-min session of collaborative activities, and to compare student evaluations. Data were either ordinal (test scores and evaluations) or non-normally distributed (confidence levels and self-perceived improvement), as evaluated by normality plots and Shapiro-Wilk's test for normality, and we therefore used nonparametric statistics (Wilcoxon's signed rank sum test and the Mann-Whitney U-test). All data are reported as medians with corresponding interquartile ranges.During the 20-min session of collaborative activities, 97% of the arterial gases were interpreted correctly in group A, with confidence levels of 100% (range: 95–100%). In group B, 73% of the answers were correct after the individual phase, with confidence levels of 90% (range: 60–100%, both P < 0.01 vs. group A). This increased to 91% correct answers with confidence levels of 100% (range: 90–100%) after the pair phase (both P < 0.01 vs. the individual phase), which were similar to scores and confidence levels in group A (P = 0.10 and P = 0.88, respectively).Test scores improved in both groups from the pretest to the posttest (Table 2). In group A, test scores were 2 points (range: 1–2 points) before and 4 points (range: 3–4 points) after the class, whereas group B scored 2 points (range: 1–2 points) before and 3 points (range: 3–4 points) after the class (both P < 0.0001). However, no difference was present between groups when the improvement in test scores was compared (P = 0.31). The individual confidence levels for all four arterial blood gases increased similarly in both groups (Table 2). Subsequent to the posttest, students evaluated their academic gain, the quality of the teaching, and their own effort and provided an overall assessment of the lesson. These four parameters were rated as poor, below average, average, above average, or excellent. Furthermore, students reported their self-perceived improvement in their ability to diagnose acid-base disorders (from 0% to 100%). The evaluations of the lesson were positive in both groups, and >60% of the students evaluated the overall assessment of the lesson as excellent, regardless of the teaching strategy. Similarly, more than half of the students in both groups evaluated the academic gain, quality of teaching, and their own effort as above average or excellent. None of the students in either group rated any of the four parameters as below average or poor. Group A reported that their self-perceived ability of arterial blood gas analysis had improved by 100% (range: 90–100%). The corresponding value of group B was 100% (range: 85–100%), with no difference between groups (P = 0.71).Table 2. Correct answers and confidence levels in the pre- and posttestGroup AGroup BPretestPosttestPretestPosttestAcid-Base DisorderCorrect answers, %Confidence levels, median (interquartile range)Correct answers, %Confidence levels, median (interquartile range)Correct answers, %Confidence levels, median (interquartile range)Correct answers, %Confidence levels, median (interquartile range)Partially compensated respiratory alkalosis5543 (10–50)82*95* (90–100)4240 (10–65)79*90* (73–100)No acid-base disorder3620 (0–50)100*100* (100–100)7950 (8–65)95*100* (95–100)Combined respiratory and metabolic acidosis2315 (0–50)77*90* (85–100)510 (0–30)58*90* (55–100)Partially compensated metabolic acidosis275 (0–45)91*98* (90–100)261 (0–55)89*90* (78–100)n = 22 students in group A and 19 students in group B.*Significant difference from the pretest (P < 0.05).In accordance with former studies in the field of physiology education (1, 2, 4), the present data demonstrate that the number of correct answers and confidence levels are increased from the individual phase to the pair phase in the context of Mazur's peer instruction technique. However, none of the former studies assessed the overall effect on learning, which was evaluated by a pre- and posttest in the present study. Notwithstanding that a practice effect may be present and thus at least, to some extent, may have confounded our findings because identical gases were used in the tests, no difference between the two collaborative teaching strategies could be detected. A larger study, in which a third intervention group where students work individually without any collaborative activities is also included, is nonetheless needed before any definitive conclusions can be made on this matter. In any event, our findings indicate that collaborative strategies are efficient for teaching students to diagnose common acid-base disorders by arterial blood gas analysis, regardless of whether conventional group work or peer instruction is used, and both approaches are associated with a high degree of student satisfaction. Collaborative teaching strategies may therefore be beneficial for conveying the complexity of arterial blood gas analysis in a time-restricted setup.DISCLOSURESNo conflicts of interest, financial or otherwise, are declared by the author(s).AUTHOR CONTRIBUTIONSAuthor contributions: M.W.P., L.N.T., R.R.P., and R.M.G.B. performed experiments; M.W.P. and R.M.G.B. analyzed data; M.W.P., L.N.T., R.R.P., and R.M.G.B. interpreted results of experiments; M.W.P. prepared figures; M.W.P. and R.M.G.B. drafted manuscript; M.W.P., L.N.T., R.R.P., and R.M.G.B. edited and revised manuscript; M.W.P., L.N.T., R.R.P., and R.M.G.B. approved final version of manuscript; R.M.G.B. conception and design of research.REFERENCES1. Cortright RN, Collins HL, DiCarlo SE. Peer instruction enhanced meaningful learning: ability to solve novel problems. Adv Physiol Educ 29: 107–111, 2005.Link | ISI | Google Scholar2. Giuliodori MJ, Lujan HL, DiCarlo SE. Peer instruction enhanced student performance on qualitative problem-solving questions. Adv Physiol Educ 30: 168–173, 2006.Link | ISI | Google Scholar3. Mazur E. Peer instruction: getting students to think in class. In: The Changing Role of Physics Departments in Modern Universities. Proceedings of the ICUPE, edited by , Redish EF, Rigden JS. Woodbury, NY: The American Institute of Physics, 1997, p. 981–988.Crossref | Google Scholar4. Rao SP, DiCarlo SE. Peer instruction improves performance on quizzes. Adv Physiol Educ 24: 51–55, 2000.Link | ISI | Google ScholarAUTHOR NOTESAddress for reprint requests and other correspondence: R. M. G. Berg, Rigshospitalet, Centre of Inflammation and Metabolism, Dept. of Infectious Diseases, section 7641, Blegdamsvej 9, DK-2100 Copenhagen Ø, Denmark (e-mail: [email protected]com). 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