Precordial Doppler Research Articles

Optimal dose of normal saline for confirming correct peripheral venous access with precordial Doppler ultrasonography in children

Precordial Doppler ultrasound technology can be utilized to confirm correct peripheral intravenous vascular (PIV) access in children during surgery. This study aimed to determine the minimally required dose of normal saline (NS) for confirming correct PIV access. Healthy children were randomly allocated to receive a 0.1 mL/kg, 0.3 mL/kg, or 0.5 mL/kg dose of NS injected via PIV access. Two independent raters judged the change in the recorded precordial Doppler sound test (S-test) before and after NS injection. Typically, rapid injection of NS increased the pitch of the heartbeat as the injection volume increased. Changes in blood flow velocity test (V-test) results were evaluated using a cut-off value of 1 cm/s. Both in the S- and V-tests, the detection rate of correct PIV access was lower with 0.1 mL/kg NS than with 0.3 mL/kg or 0.5 mL/kg. Logistic regression analysis showed that the positive results in both the S- and V-tests were significantly decreased with a 0.1 mL/kg NS; no significant difference was observed with a 0.3 mL/kg NS (reference dose: 0.5 mL/kg). These results suggest 0.3 mL/kg is the minimally required dose of NS for confirming correct PIV access. This study is registered with the University Hospital Medical Information Network (UMIN000041330).

A fully automated algorithm for heart rate detection in post-dive precordial Doppler ultrasound

Background: Doppler ultrasound is used currently in decompression research for the evaluation of venous gas emboli (VGE). Estimation of heart rate from post-dive Doppler ultrasound recordings can provide a tool for the evaluation of physiological changes from decompression stress, as well as aid in the development of automated VGE detection algorithms that relate VGE presence to cardiac activity. Method: An algorithm based on short-term autocorrelation was developed in MATLAB to estimate the heart rate in post-dive precordial Doppler ultrasound. The algorithm was evaluated on 21 previously acquired and labeled precordial recordings spanning Kisman-Masurel (KM) codes of 111–444 (KM I–IV) with manually derived instantaneous heart rates. Results: A window size of at least two seconds was necessary for robust and accurate instantaneous heart rate estimation with a mean error of 1.56 ± 7.10 bpm. Larger window sizes improved the algorithm performance, at the cost of beat-to-beat heart rate estimates. We also found that our algorithm provides good results for low KM grade Doppler recordings with and without flexion, and high KM grades without flexion. High KM grades observed after movement produced the greatest mean absolute error of 6.12 ± 8.40 bpm. Conclusion: We have developed a fully automated algorithm for the estimation of heart rate in post-dive precordial Doppler ultrasound recordings.

Neonatal heart rate monitoring at birth with hands-free foetal doppler

There is a need for improved measurement and documentation of the neonatal heart rate immediately after birth, which currently relies on auscultation with a stethoscope. Measurement of the heart rate is a medical requirement within the first minute after birth in all babies. Heart rate at birth is the only reliable indicator of the health of the neonate which does not establish breathing immediately. In sick neonates pulse oximetry is usually available but does not provide an output for the first minute even in healthy neonates. Although the ECG is considered the gold standard, it may provide a false measurement due to pulseless electrical activity of the myocardium. Neonatal ECG technology is not routinely available at birth, however prior to birth the fetal heart rate is routinely obtained and documented by a low cost doppler ultrasound. Recently the fetal doppler has been shown to be effective immediately after birth on the neonatal chest (Hutchon 2022) but requires constant attention by the carer, and may interfere with measures to provide positive pressure ventilation or other resuscitation measures. A fetal doppler ultrasound device has been extended to provide a hands free sensor which is secured on the neonatal chest by the surface tension of the transducer gel. The system also works well through polythene and provides a safe and effective neonatal heart rate monitor inside a sterile polythene bag for use at caesarean birth. The design features are presented and preliminary data showing the precordial doppler provides a heart rate closely equivalent to the heart rate from the gold standard ECG.

The Use of Foetal Doppler Ultrasound to Determine the Neonatal Heart Rate Immediately after Birth: A Systematic Review.

Determining the neonatal heart rate immediately after birth is unsatisfactory. Auscultation is inaccurate and provides no documented results. The use of foetal Doppler ultrasound has been recognised as a possible method of determining the neonatal heart rate after birth over the last nine years. This review includes all published studies of this approach, looking at accuracy, speed of results, and practical application of the approach. Precordial Doppler ultrasound has been shown to be as accurate as ECG and more accurate than oximetry for the neonatal heart rate, and provides quicker results than either ECG or oximetry. There is the potential for a much improved determination and documentation of the neonatal heart rate using this approach.

Optimal probe position for precordial Doppler ultrasound inchildren.

Precordial Doppler ultrasound technology can be used to confirm correct peripheral intravenous access in children. Changes in precordial Doppler sound from the baseline after injecting normal saline are detected using a correct peripheral intravenous access. However, the location of the precordial Doppler probe has been inconsistent in previous studies. Our study aimed to determine whether the right or left parasternal border is the optimal location for precordial Doppler probe placement. This single-center, prospective interventional study was conducted between July 2021 and January 2022 and included children aged 1-6 years. The Doppler probe was placed under general anesthesia at the most audible site on the right and left parasternal borders of patients. Baseline heartbeat was recorded by the Doppler for 10 s on the right and left parasternal borders. After randomizing the order of the recorded data, two blinded raters separately listened to the data and decided the audibility of the sounds. A total of 77 patients were enrolled in the study. The proportion of the audible baseline heartbeat was significantly higher on the left parasternal borders than on the right by both rater 1 (96.1%, 22.1%, p< 0.001) and rater 2 (96.1%, 27.3%, p< 0.001). Regarding inter-rater reproducibility, Cohen's kappa statistics for the left and right parasternal borders were significant (0.65 and 0.79, both p< 0.001). The baseline heartbeat was more audible on the left parasternal border than on the right parasternal border with acceptably high interrater reproducibility. This is inconsistent with the interpretations of previous reports.

Precordial Doppler to assess vascular access in children: A preliminary report

Delayed identification and dysfunction of peripheral intravenous (PIV) infiltration can lead to serious injury in children. This preliminary study aimed to describe the application of precordial Doppler ultrasound to detect and confirm the correct PIV access in children with congenital heart disease (CHD). This study was conducted on children (<18 years) diagnosed with CHD and admitted to the pediatric intensive care unit (PICU) of a single center after cardiac surgery or cardiac catheterization between February 2020 and May 2021. Three raters judged the precordial Doppler sound change (S test) after injection of 0.5 mL/kg of normal saline (NS) through the PIV access. Blood-flow velocities before and after the NS injection were recorded and the accuracy of detecting PIV catheter infiltration and dysfunction was analyzed (V test). The overall incidence of PIV infiltration and dysfunction was in 3 out of 103 patients (2.9%). The sensitivity, specificity, positive and negative likelihood ratios, and area under the receiver operating characteristic curve were 3 out of 3 [100%, 95% confidence interval (CI): 29.2-100], 86 out of 100 (86%, 95% CI: 77.6%-92.1), 7.1, 0.0, and 0.93, respectively, in the S test and they were 2 out of 3 (66.7%, 95% CI: 9.4%-99.2), 94 out of 100 (94.0%, 95% CI: 87.4%-7.8%), 11.1, 0.36, and 0.80, respectively in the V test. Precordial Doppler ultrasound was a feasible and accurate technique for confirming correct PIV access in children with CHD; however, a larger, prospective investigation is necessary to examine its diagnostic accuracy.

Introduction of precordial Doppler ultrasound to confirm correct peripheral venous access during general anesthesia in children: A preliminary study.

Delayed identification of infiltration and dysfunction of peripheral intravenous (PIV) access can lead to serious consequences during general anesthesia in children. This preliminary study aimed to describe the application of precordial Doppler ultrasound during general anesthesia in children to detect and confirm the correct PIV access and to evaluate the accuracy of this method. This was a single-center, preliminary study that was conducted in children (<18 years) who were scheduled for elective surgeries between October 2019 and March 2020. Rater anesthesiologists judged the change in precordial Doppler sound (S test) before and after injection of 0.5 mL/kg of normal saline (NS) via PIV. Blood flow velocity before and after NS injection was recorded, and multiple cutoff points were set to analyze the accuracy of detecting the infiltration and dysfunction of PIV catheter (V test). The total incidence of peripheral infiltration and dysfunction of PIV catheter was 7/512 (1.4%). In the S test, the sensitivity, specificity, positive and negative likelihood ratios, and area under the receiver-operating characteristic curves (AUCs) were 5/7 (71.4%; 95% confidence interval [CI], 29.0%-96.3%), 490/505 (97.0%; 95% CI, 95.1%-98.3%), 24.0, 0.29, and 0.84, respectively. The V test showed that the reasonable threshold of blood flow velocity change was 1.0 m/s, with sensitivity, specificity, positive and negative likelihood ratios, and AUC of 4/7 (57.1%; 95% CI, 18.4%-90.1%), 489/505 (96.8%; 95% CI, 94.9%-98.2%), 18.0 and 0.44, and 0.84, respectively. This preliminary study demonstrated that precordial Doppler ultrasound is a feasible, easy-to-use, and noninvasive technique with good accuracy to confirm the correct PIV access during general anesthesia in children. However, its accuracy requires further evaluation.

Early Detection is Vital in Successful Resuscitation after Massive Mixed-air and Carbon dioxide Venous Embolism during Laparoscopic Surgery

Air embolism is a life threatening condition, which is commonly reported in sitting position surgery or when the venous sinuses are open. Symptoms may appear depending on volume of air entrained and rate of entrainment. Lung acts as a filter and if the area exposed is more than the critical volume, then ventilation – perfusion (V/Q) mismatch leads to hypoxia and ultimately death. In contrast, carbon dioxide in large volume, lead to right ventricular outflow tract (RVOT) obstruction and reduce cardiac output. In people with probe patent patent foramen ovale, this can reach left atrium and lead to systemic embolism. Laparoscopic surgery, in general is safe and in situations, where there is abnormal organ placement and arterio venous connection may lead to gas placement into circulation. Detection is by trans esophageal echocardiography, precordial doppler, end tidal carbon dioxide monitoring and pulse oximetry. We present one such case with altered anatomy leading to ptosis of liver and massive mixed air and carbon dioxide embolism, which was successfully re-suscitated. Keywords: Air embolism; Carbon dioxide embolism; Laparoscopy.

Hand- held Precordial Doppler Ultrasound Detects Heart Rate Faster than Electrocardiogram in Neonatal Resuscitation

Hand- held Precordial Doppler Ultrasound Detects Heart Rate Faster than Electrocardiogram in Neonatal Resuscitation

Hand- held Precordial Doppler Ultrasound Detects Heart Rate Faster than Electrocardiogram in Neonatal Resuscitation

Background: A fast and accurate newborn heart rate (HR) assessment is critical to neonatal resuscitation. The 7th edition of Neonatal Resuscitation Program (NRP) guidelines recommends initial use of precordial auscultation (PA) and then the use of pulse oximetry (PO) and electrocardiogram (ECG) if the HR is unobtainable via PA or if advanced resuscitation is necessary. Studies have shown that PA is inaccurate. PO and ECG are subject to …

Serum tau concentration after diving - an observational pilot study.

Increased concentrations of tau protein are associated with medical conditions involving the central nervous system, such as Alzheimer's disease, traumatic brain injury and hypoxia. Diving, by way of an elevated ambient pressure, can affect the nervous system, however it is not known whether it causes a rise in tau protein levels in serum. A prospective observational pilot study was performed to investigate changes in tau protein concentrations in serum after diving and also determine their relationship, if any, to the amount of inert gas bubbling in the venous blood. Subjects were 10 navy divers performing one or two dives per day, increasing in depth, over four days. Maximum dive depths ranged from 52-90 metres' sea water (msw). Air or trimix (nitrogen/oxygen/helium) was used as the breathing gas and the oxygen partial pressure did not exceed 160 kPa. Blood samples taken before the first and after the last dives were analyzed. Divers were monitored for the presence of venous gas emboli (VGE) at 10 to15 minute intervals for up to 120 minutes using precordial Doppler ultrasound. Median tau protein before diving was 0.200 pg·mL⁻¹ (range 0.100 to 1.10 pg·mL⁻¹) and after diving was 0.450 pg·mL⁻¹ (range 0.100 to 1.20 pg·mL⁻¹; P = 0.016). Glial fibrillary acidic protein and neurofilament light protein concentrations analyzed in the same assay did not change after diving. No correlation was found between serum tau protein concentration and the amount of VGE. Repeated diving to between 52-90 msw is associated with a statistically significant increase in serum tau protein concentration, which could indicate neuronal stress.

Gas embolism during endoscopic retrograde cholangiopancreatography: diagnosis and management.

Air embolism is rarely diagnosed and is often fatal. The diagnosis is often not made in a timely manner given the rapid and severe clinical deterioration that often develops, frequently leading to cardiac arrest. Many patients are only diagnosed post-mortem. With the increasing use of endoscopic retrograde cholangiopancreatography, air embolism should be considered in the differential diagnosis in patients who experience sudden clinical deterioration during or immediately after the procedure. Clinical suspicion is key in the diagnosis and management of air embolism. Use of precordial Doppler ultrasound and transesophageal echocardiogram can aid in the diagnosis of air embolism. Once the diagnosis is made, supportive management of airway, breathing and circulation is pivotal. Advanced cardiac life support should be initiated when necessary. Fluid resuscitation and vasopressors can improve cardiac output. Hyperbaric oxygen therapy should be considered when possible in cases of suspected cerebral air embolism cases to improve neurological outcome. A multidisciplinary team approach and effective communication with experts, potentially including an anesthesiologist, cardiologist, intensivist, radiologist and surgeon, can improve the outcome in air embolism.

Surgical Strategy in Large Vestibular Schwannoma.

Particular care to facial nerve function preservation should be the ultimate goal in surgery for large vestibular schwannomas. We present a 60-year-old patient who presented with an enlarging right vestibular schwannoma and nonserviceable hearing. The patient was operated in the semisitting position after a patent foramen ovale was ruled out. During the positioning, the feet were positioned at the level of the heart. Precordial Doppler was used to monitor for air embolism. Straight skin incision and retrosigmoid craniotomy was performed. Specific attention to venous bleeding was made during the approach. Meticulous arachnoid dissection of the capsule preserving the arachnoid plane at the surface of the brain stem and the facial nerve can be achieved more efficiently with the patient in the semisiting position and with bimanual microdissection technique. After drilling of the internal auditory canal (IAC), we were able to achieve near total removal of the tumor, leaving a tiny tumor carpet due to extreme adherence to the nerve. Water-tight dura closure and replacement of the bone flap was performed. The patient woke up with a House–Brackmann grade III facial weakness which improved to grade I at 6 weeks postoperatively. Postoperative magnetic resonance imaging (MRI) showed a tiny residual at the surface of the facial nerve at the entrance of the IAC. Near total (> 98%) resection of large vestibular schwannomas is an acceptable surgical strategy with excellent facial nerve outcome. With appropriate patient positioning in semisitting and proper anesthesiological and surgical management, the risk of air embolism is negligible. The link to video can be found at: https://youtu.be/ErG9VexbiGw .

The relationship between end-expired carbon dioxide tension and severity of venous air embolism during sitting neurosurgical procedures – A contemporary analysis

Study objectiveDetermine if changes in expired carbon dioxide tension correlate with the severity of venous air embolism (VAE) associated hemodynamic changes in humans. DesignRetrospective case series. SettingA single academic medical center with high-volume neurosurgical practice. PatientsOne hundred forty seven adult patients having neurosurgical procedures performed with general anesthesia in the sitting position who experienced venous air embolism. InterventionsIdentification of documentation of venous air embolism by either precordial Doppler sonography or transesophageal echocardiography. MeasurementRetrospective determination of changes in end-expired carbon dioxide (EECO2) changes associated with venous air embolism. Main resultsGreater absolute and relative decreases in end-expired carbon dioxide tension were associated with greater hemodynamic manifestations of venous air embolism. However, based on receiver operating characteristic curve analysis, the absolute and relative changes in EECO2 have moderate utility for predicting the severity of hemodynamic consequences of venous air embolism as area under the curve for absolute and relative carbon dioxide tensions were 0.7654 and 0.7263, respectively. ConclusionsGreater magnitude of decreases in EECO2 is associated with hemodynamically-significant VAE in mechanically-ventilated patients. However, the magnitude of changes may have limited utility to diagnose VAE or exclude the diagnosis of VAE in patients with unexplained intraoperative hypotension.

Incidence of Venous Air Embolism During Endoscopic Retrograde Cholangiopancreatography

Known complications of endoscopic retrograde cholangiopancreatography (ERCP) include pancreatitis, bleeding, duodenal perforation, and venous air embolism (VAE). The aim of this study was to determine the incidence of VAE during ERCP and be able to differentiate high-risk versus low-risk ERCP procedures. This is a prospective cohort study consisting of patients who underwent ERCP and were monitored with a precordial Doppler ultrasound (PDU) for VAE. PDU monitoring was digitally recorded and analyzed to confirm the suspected VAE. Demographic and clinical data related to the anesthetic care, endoscopic procedure, and intraoperative hemodynamics were analyzed. A total of 843 ERCP procedures were performed over a 15-month period. The incidence of VAE was 2.4% (20 patients). All VAE's occurred during procedures in which stent placement, sphincterotomy, biopsy, duct dilation, gallstone retrieval, cholangioscopy, or necrosectomy occurred. Ten of 20 (50%) of VAEs were associated with hemodynamic alterations. None occurred if the procedure was only diagnostic or for stent removal. Subanalysis for the type of procedure showed that VAE was statistically more frequent when stents were removed and then replaced or if a cholangioscopy was performed. The high incidence of VAE highlights the need for practitioners to be aware of this potentially serious event. Use of PDU can aid in the detection of VAE during ERCP and should be considered especially during high-risk therapeutic procedures. Detection may allow appropriate interventions before serious adverse events such as cardiovascular collapse occur.

Indices of Increased Decompression Stress Following Long-Term Bed Rest.

Human extravehicular activity (EVA) is essential to space exploration and involves risk of decompression sickness (DCS). On Earth, the effect of microgravity on physiological systems is simulated in an experimental model where subjects are confined to a 6° head-down bed rest (HDBR). This model was used to investigate various resting and exercise regimen on the formation of venous gas emboli (VGE), an indicator of decompression stress, post-hyperbaric exposure. Eight healthy male subjects participating in a bed rest regimen also took part in this study, which incorporated five different hyperbaric exposure (HE) interventions made before, during and after the HDBR. Interventions i–iv were all made with the subjects lying in 6° HD position. They included (C1) resting control, (C2) knee-bend exercise immediately prior to HE, (T1) HE during the fifth week of the 35-day HDBR period, (C3) supine cycling exercise during the HE. In intervention (C4), subjects remained upright and ambulatory. The HE protocol followed the Royal Navy Table 11 with 100 min spent at 18 m (280 kPa), with decompression stops at 6 m for 5 min, and at 3 m for 15 min. Post-HE, regular precordial Doppler audio measurements were made to evaluate any VGE produced post-dive. VGE were graded according to the Kisman Masurel scale. The number of bubbles produced was low in comparison to previous studies using this profile [Kisman integrated severity score (KISS) ranging from 0–1], and may be because subjects were young, and lay supine during both the HE and the 2 h measurement period post-HE for interventions i–iv. However, the HE during the end of HDBR produced significantly higher maximum bubble grades and KISS score than the supine control conditions (p < 0.01). In contrast to the protective effect of pre-dive exercise on bubble production, a prolonged period of bed rest prior to a HE appears to promote the formation of post-decompression VGE. This is in contrast to the absence of DCS observed during EVA. Whether this is due to a difference between hypo- and hyperbaric decompression stress, or that the HDBR model is a not a good model for decompression sensitivity during microgravity conditions will have to be elucidated in future studies.

Study of the Entropy as a Way to Detect Venous Air Embolism Using a Pre-cordial Doppler

Venous air embolism (VAE) is the air bubble accumulation in the right side of the heart, or in the pulmonary region. Pre-cordial Doppler allows a real-time monitoring of heart sound and is used to detect VAE episodes through changes in cardiac sound. Sometimes these changes are not detected by the operator, which reveals the importance of finding other robust methods for VAE detection. This work aims to study entropy as a feature of the heart sound that may provide useful information on VAE episodes.A clinical protocol was designed: Doppler Heart Sound (DHS) was collected at baseline, and following infusions of saline with 4 distinct volumes and 2 infusion rates, and given through 2 infusion vias, to 4 patients enrolled in the clinical study. Entropy of these segments was obtained, and relation between the extracted feature and saline infusions was studied.Entropy presents a good performance showing an increase in response to saline injections (increased blood flow turbulence).

Incidence of venous air embolism and blood gas changes seen in infratentorial surgeries operated in sitting position

Our aim was to find out the rate and timing of venous air embolism (VAE), other complications associated with sitting position and changes on arterial blood gas during and after VAE. We analyzed retrospectively files of 124 patients who underwent posterior fossa surgery in department of Neurosurgery of our institute between January 2004 and April 2014. The incidence of emboli was 76,3% in the first 3 hours of the surgery while it was 38.2% in the first 2 hours in total. VAE was seen in a total of 21 patients (16.9%) and it was detected by a sudden drop of minimum 2mmHg of end-tidal CO2 (EtCO2)(25.38 ± 3.28 mmHg) in all cases (100%). The pH, PaO2 and PaCO2 values of the patients with and without emboli were evaluated pre and post-operatively and no significant difference was found (p>0.05). Precordial doppler ultrasonography is the most sensitive non-invasive monitoring device for accurate detection of even small VAE which are not clinically relevant. The most sensitive technique for detection of VAE is transoesophageal echocardiography but it is expensive, invasive and can cause some serious complications. In our study, emboli were most frequently seen in the 3rd hour of the surgery which coincide with tumor resection, thus proposing anaesthesiologists to be more cautious about VAE and EtCO2 during the tumor resection period.

Simulated High Altitude Helium-Oxygen Diving.

Experience with commercial heliox diving at high altitude is limited. The purpose of this study was to evaluate the effects of acute high-altitude exposure on fitness to dive and the safety of decompression after heliox diving while using U.S. Navy heliox decompression tables with Cross correction. Four professional male divers were consecutively decompressed in a hypo- and hyperbaric chamber to altitudes of 3000 m (9842.5 ft), 4000 m (13,123.4 ft), and 5200 m (17,060.4 ft) during the 8-d study. The dive profiles tested were to 30 m (98.4 ft) for 60 min at all three altitudes and, in addition, a dive to 50 m (164 ft) for 60 min at 5200 m altitude. The decompression followed the U.S. Navy heliox decompression table. The safety of decompression was evaluated by precordial Doppler venous gas emboli (VGE) monitoring during the decompression stages and postdive monitoring of the divers for symptoms of decompression sickness (DCS). Effects of altitude exposure were measured as subjective rating and EEG signs of sleepiness and fatigue, clinical symptoms of high altitude disease, and fitness to dive. A total of 24 person-dives were conducted. There were no VGE detected during the decompression and no postdive symptoms of decompression illness. Both the EEG findings and subjective evaluation indicated increased sleepiness and fatigue at 3000 m, 4000 m, and 5200 m, all compared with the sea level baseline. During the diving phase, both the EEG findings and subjective evaluation scores returned to the baseline and the divers successfully completed diving. Diving at high altitude with a short acclimatization period appears safe despite divers exhibiting clinical symptoms and EEG signs of impairment by hypoxia at high altitude. Despite a small number of dives, the results of this study indicate that our application of U.S. Navy standard heliox decompression tables with Cross correction is effective and could be used for underwater constructions up to 5200 m altitude, with due caution.Shi L, Zhang Y, Tetsuo K, Shi Z, Fang Y, Denoble PJ, Li Y. Simulated high altitude helium-oxygen diving. Aerosp Med Hum Perform. 2017; 88(12):1088-1093.

Dive Risk Factors, Gas Bubble Formation, and Decompression Illness in Recreational SCUBA Diving: Analysis of DAN Europe DSL Data Base.

Introduction: The popularity of SCUBA diving is steadily increasing together with the number of dives and correlated diseases per year. The rules that govern correct decompression procedures are considered well known even if the majority of Decompression Sickness (DCS) cases are considered unexpected confirming a bias in the “mathematical ability” to predict DCS by the current algorithms. Furthermore, little is still known about diving risk factors and any individual predisposition to DCS. This study provides an in-depth epidemiological analysis of the diving community, to include additional risk factors correlated with the development of circulating bubbles and DCS.Materials and Methods: An originally developed database (DAN DB) including specific questionnaires for data collection allowed the statistical analysis of 39,099 electronically recorded open circuit dives made by 2,629 European divers (2,189 males 83.3%, 440 females 16.7%) over 5 years. The same dive parameters and risk factors were investigated also in 970 out of the 39,099 collected dives investigated for bubble formation, by 1-min precordial Doppler, and in 320 sea-level dives followed by DCS symptoms.Results: Mean depth and GF high of all the recorded dives were 27.1 m, and 0.66, respectively; the average ascent speed was lower than the currently recommended “safe” one (9–10 m/min). We found statistically significant relationships between higher bubble grades and BMI, fat mass, age, and diving exposure. Regarding incidence of DCS, we identified additional non-bubble related risk factors, which appear significantly related to a higher DCS incidence, namely: gender, strong current, heavy exercise, and workload during diving. We found that the majority of the recorded DCS cases were not predicted by the adopted decompression algorithm and would have therefore been defined as “undeserved.”Conclusion: The DAN DB analysis shows that most dives were made in a “safe zone,” even if data show an evident “gray area” in the “mathematical” ability to predict DCS by the current algorithms. Some other risk factors seem to influence the possibility to develop DCS, irrespective of their effect on bubble formation, thus suggesting the existence of some factors influencing or enhancing the effects of bubbles.