P031: CARDIAC AUSCULTATION THOUGH CLOTHING: THE TRUTH BEHIND THE TABOO
Joseph E LaGrew, MD1, Delaney Lagrew2, Juanito Abrigo3, Megan Koenig1, Talles Sidronio2, Terrie Vasilopoulos, PhD1, Nik Gravenstein, MD1; 1University of Florida Department of Anesthesiology, 2University of Florida College of Medicine, 3University of Florida
Introduction: Medical students are taught that transmission of heart sounds to the stethoscope occurs optimally when the bell or diaphragm is placed on the patient’s skin; however, many providers in practice admit to auscultation through a layer of clothing for cleanliness, efficiency and patient privacy.1 This prospective, non-inferiority cohort study evaluated the effect of auscultation on the skin as compared to through a single layer of clothing on normal and abnormal heart sounds.
Methods: 71 consenting subjects were recruited and heart sounds were recorded in four areas on skin and over their clothing or hospital gown in the sitting position. Previous cardiac exams, recent echocardiograms, medical comorbidities and basic demographics including weight and BMI were recorded. All patient data was de-identified prior to inclusion in the study database. Recordings were imported to a computer, transformed, and processed to analyze the peak of S1 and S2 heart sounds in amplitude as well as the average amplitudes of any murmurs. The study was powered to detect non-inferiority of no more than a 3 decibel (dB) difference in amplitude between normal and abnormal heart sounds. Demographics were analyzed using descriptive statistics. Heart sounds’ composite waveforms were analyzed with linear mixed models for repeated measures to assess differences between skin and clothing on decibel magnitude.
Results: 71 patients were recruited with one patient being excluded for not having a murmur. Additionally, 3 patients had no measurements recorded at least one site or had corrupted files which could not be uploaded into StethAssist. This study cohort was comprised of 80% clinic patients who were evaluated with their clothing from home and 20% inpatients who wore a hospital gown during the exam. The average age was 65 years old, 63% of the study cohort was female, average ASA was 3.5, and average BMI was 30.4. A significant proportion of the population had obesity (42.3%), previous sternotomy (32.4%) and COPD (14.1%). There was no difference in sounds based on auscultation on skin compared to over one layer of clothing or hospital gown (p = 0.58). Means with 95% confidence intervals are depicted in Figure 1. This difference persisted for both normal heart sounds (S1 and S2) (p=0.43) as well as for murmurs (p=0.74) as depicted in Figure 2.
Discussion/Conclusion: This prospective, case control study demonstrated non-inferiority of heart sound and murmur auscultation over clothing compared to directly on skin, contrary to classic teaching but consistent with a previous study in which doctors were unable to discern the difference between normal heart sounds recorded on skin compared to those recorded through one layer of clothing.1 Cardiac auscultation on skin increases the length of the exam as well as the likelihood of and may make patients uncomfortable. This data indicates that skin auscultation is not necessary in most patients. Additionally, this study utilized different operators of varying levels of training with no differences found in sound amplitude on clothing compared to skin when instructed to provide “firm” pressure with the stethoscope, demonstrating broad applicability of the results shown here.