Ovine plasma dipalmitoylphosphatidylcholine does not predict decompression bubbling

Most severe cases of decompression illness are caused by vascular bubbles. We showed that there are active hydrophobic spots (AHS) on the luminal aspect of ovine blood vessels where bubbles are produced after decompression. It has been suggested that AHS may be composed of lung surfactant. Dipalmitoylphosphatidylcholine (DPPC) is the main component of lung surfactants. Blood samples and four blood vessels, the aorta, superior vena cava, pulmonary vein, and pulmonary artery, were obtained from 11 slaughtered sheep. Following exposure to 1,013 kPa for 20.4 h, we started photographing the blood vessels 15 min after the end of decompression for a period of 30 min to determine AHS by observing bubble formation. Phospholipids were extracted from AHS and from control tissue and plasma for determination of DPPC. DPPC was found in all blood vessel samples and all samples of plasma. The concentration of DPPC in the plasma samples (n = 8) was 2.04 ± 0.90 μg/ml. The amount of DPPC in the AHS which produced four or more bubbles (n = 16) was 1.59 ± 0.92 μg. This was significantly higher than the value obtained for AHS producing less than four bubbles and for control samples (n = 19) (0.97 ± 0.61 μg, P = 0.027). DPPC leaks from the lungs into the blood, settling on the luminal aspect of the vasculature to create AHS. Determining the constituents of the AHS might pave the way for their removal, resulting in a dramatic improvement in diver safety.

1 H NMR and 31 P NMR studies of DiPalmitoyl Phosphatidyl Choline (DPPC) in CDCl 3 , at various DPPC concentrations, indicate that DPPC exists as reverse micelles for concentrations beyond 6mM. At low concentrations (< 1.0 mM) aggregates of DPPC (dimers, trimers etc.) exist in CDCl 3 . The results suggest that at low concentrations of DPPC, intramolecular interactions predominate, whereas at high concentrations, intermolecular interactions predominate. Addition of water at higher concentrations of DPPC, reduces intermolecular interactions.

HISTORY: Twenty-five years ago, a 17-year-old healthy, right-handed male presented with right hemiparesis and sensory loss after scuba diving. The patient descended to 37 meters and ascending following typical dive safety protocol. Upon reaching the dive boat, he had a seizure and lost consciousness. Upon regaining consciousness, he noted new onset right-sided hemiplegia and hemiparesis. Due to the remote dive location, it took four hours to reach the nearest medical center. PHYSICAL EXAMINATION: Right-sided hemiparesis and sensory loss to light touch. Regular rate and rhythm without murmur. DIFFERENTIAL DIAGNOSIS: Decompression illness. Cardioembolic stroke from atrial fibrillation. Ischemic stroke from cerebrovascular disease. Epilepsy complicated by Todd’s Paralysis TEST AND RESULTS: Cerebrovascular imaging revealed stroke and spinal cord injury with normal cerebral vessels. Transesophageal echocardiogram (TEE) demonstrated a patent foramen ovale (PFO) with a right-to-left shunt and normal biventricular function. ECG was without atrial fibrillation FINAL WORKING DIAGNOSIS: Stroke and spinal cord injury due to decompression illness TREATMENT AND OUTCOMES:100% oxygen and one week of recompression therapy were administered. Extensive physical therapy partially improved his paralysis and paresthesia. However, diminished strength (4/5) and light touch sensation (1/2) in his right leg persisted. Despite recommendations to stop diving, the patient continued to dive at shallow depths (4.5 to 6 meters). Twenty-five years later, the patient was referred by his primary care provider to cardiology to discuss the safety of scuba diving. Repeat TEE demonstrated PFO with moderate right-to-left shunt as well as atrial septal aneurysm, normal biventricular function and mild right ventricular enlargement. Cardiac CT revealed normally connected pulmonary veins. The patient’s PFO anatomy was amenable to percutaneous closure. Given his history of decompression illness, percutaneous closure was considered to decrease the risk of adverse events associated with scuba diving. After a shared decision-making discussion, the patient elected against closure of his PFO and continues to dive recreationally at shallow depths.

Scuba diving is a popular recreational and professional activity with inherent risks. Complications related to barotrauma and decompression illness can pose significant morbidity to a diver's hearing and balance systems. The majority of dive-related injuries affect the head and neck, particularly the outer, middle and inner ear. Given the high incidence of otologic complications from diving, an evidence-based approach to the diagnosis and treatment of otic pathology is a necessity. We performed a systematic and comprehensive literature review including the pathophysiology, diagnosis, and treatment of otologic pathology related to diving. This included inner, middle, and outer ear anatomic subsites, as well as facial nerve complications, mal de debarquement syndrome, sea sickness and fitness to dive recommendations following otologic surgery. Sixty-two papers on diving and otologic pathology were included in the final analysis. We created a set of succinct evidence-based recommendations on each topic that should inform clinical decisions by otolaryngologists, dive medicine specialists and primary care providers when faced with diving-related patient pathology.

Prediction of respiratory distress syndrome by the novel dipalmitoyl phosphatidylcholine test

To establish a method by which to measure dipalmitoylphosphatidylcholine (DPPC), which is the most prevalent phospholipid in lung surfactant, by high-performance liquid chromatography (HPLC), and to measure DPPC secretion in type-II alveolar cell culture to determine whether glucocorticoid has a direct accerelating effect. Type-II alveolar cell suspensions were made with fetal rat lungs and then cultured. Dexamethasone, (10(-9), 10(-8) M) was added to some of the culture dishes. DPPC was extracted from the culture medium, purified, and measured by high-performance liquid chromatography (HPLC). In the measurements of DPPC, the specificity of isolation and measurement parity were excellent [coefficient of variation: intraassay; 5.66% (0.005 mg/ml), 25.37% (0.05 mg/ml): interassay; 8.35% (0.005 mg/ml), 0.08% (0.05 mg/ml)]. The DPPC concentration in the culture dishes of the dexamethasone was not significantly different than that of the control dishes (Student's t-test). The above results prove that dexamethasone does not directly stimulate lung alveolar type-II cells.

Gene–environment mismatch in decompression sickness and air embolism

This autopsy-based study aims to investigate the underlying causes and forensic characteristics of fatal diving incidents in Turkey, emphasizing the autopsy-based strategies employed to distinguish drowning from other diving-related pathologies such as decompression illness and arterial gas embolism. A retrospective analysis was conducted on 11 fatal diving cases evaluated by the First Forensic Medicine Specialization Board between 2002 and 2023. Data were retrieved from judicial records, including detailed autopsy reports, histopathological findings, toxicological analyses, and scene investigations. The decedents consisted of ten males and one female (median age: 45), reflecting the male-dominant profile of diving activity. Diving modalities included SCUBA (n=7), breath-hold (n=2), and surface-supplied compressor diving (n=2). The leading cause of death was drowning (n=5), followed by arterial gas embolism (AGE; n=2), sudden cardiac death (n=2), subarachnoid hemorrhage (n=1), and asphyxia due to mechanical entrapment (n=1). AGE cases demonstrated intravascular gas via specialized autopsy techniques. Cardiovascular comorbidities were identified in four cases, while medications- primarily prescribed-were detected in five. Alcohol and illicit drugs were absent in all cases. Diving fatalities pose complex medicolegal challenges that require a multidisciplinary approach. Drowning and AGE were the most frequent causes, often accompanied by cardiovascular pathology. Proper autopsy techniques, scene correlation, and pre-dive medical screening remain critical for accurate diagnosis and prevention. The findings underscore the need for standardized forensic protocols, especially in regions with limited access to postmortem imaging.

Differences in circulating bubble production have been described after exposures in altitude chambers between men and women. The present study was designed to examine gender differences in circulating bubble production after a dive. Fifty-two men and 52 women performed the same dive profile (25 min to 35 m). Circulating bubbles were detected by continuous wave Doppler. Tests were conducted at sea in a boat, at 10-min intervals for 1 h after surfacing. Signals were graded according to the Spencer scale. The categorical data were then converted to a single number reflecting total bubble activity using the KISS index. Considering each measurement period, bubble grade was higher in men than women 30, 40 and 50 min postdive. On the contrary, bubble grade was comparable between men and women 10, 20 and 60 min after the dive. KISS index was significantly higher in men than women (6.77 [0.65-32.3] versus 0.91 [0-22.9], P<0.02). KISS index was significantly correlated with age, weight and body fat mass in the whole population and in the men and women separately. Postmenopausal women had a higher KISS index (42 [15-47]) when compared with premenopausal women and men older than 50 years. No difference in bubble production was found according to the use of oral contraceptive pills or the phase of the menstrual cycle. Overall, we observed fewer circulating bubbles in women than in men after an open sea SCUBA dive. This difference disappeared in the postmenopausal women.

Effect of particle emissions from biofuel combustion on surface activity of model and therapeutic pulmonary surfactants

Nanotechnology is a rapidly growing field with silver nanoparticles (AgNP) in particular utilized in a wide variety of consumer products. This has presented a number of concerns relating to exposure and the associated toxicity to humans and the environment. As inhalation is the most common exposure route, this study investigates the potential toxicity of AgNP to A549 alveolar epithelial carcinoma cells and the influence of a major component of lung surfactant dipalmitoylphosphatidylcholine (DPPC) on toxicity. It was illustrated that exposure to AgNP generated low levels of oxidative stress and a reduction in cell viability. While DPPC produced no significant effect on viability studies its presence resulted in increased reactive oxygen species formation. DPPC also significantly modified the inflammatory response generated by AgNP exposure. These findings suggest a possible interaction between AgNP and DPPC causing particles to become more reactive, thus increasing oxidative insult and inflammatory response within A549 cells.

Non-invasive and quantitative sampling of particles in exhaled air may provide valuable information on the status of the peripheral airways. Studies of particles have confirmed the presence of pulmonary surfactant, including both important phospholipids and surfactant proteins. The aim of this study was to develop a reliable method for the quantification of the major phosphatidylcholines (PCs) in exhaled particles. Methods: Exhaled particles were counted and collected on membranes using the PExA method. The particles were extracted with methanol:chloroform prior to flow injection into an electrospray ionization tandem mass spectrometer. A quantitative method was developed for dipalmitoylphosphatidylcholine (DPPC) and palmitoyl-oleoylphosphatidylcholine (POPC) using selected reaction monitoring. The method was validated by investigating within- and between-batch precision, accuracy, carry-over, stock stability, short-term and long-term stability, freeze-thaw stability and processed sample integrity. The validated method was used to investigate the inter-individual variation in exhaled particles from 6 healthy volunteers. Results: The method had a linear response for DPPC and POPC with a limit of quantification of 0.005 µM. The DPPC and POPC concentration, expressed as weight % in exhaled particles, were 13.9 (median, range 8.8-16%) and 4.1 (median, range 2.4-4.9%), respectively, of the total particle sample. Conclusion: We have developed a reliable method for the quantification of surfactant PCs in exhaled particles using a simple sample extraction and mass spectrometry. The method can readily be applied in clinical studies to investigate the role of PCs in different lung related diseases.

Comparative study of clinical pulmonary surfactants using atomic force microscopy

Background: Despite evolution in decompression algorithms, decompression illness is still an issue. Reducing vascular gas emboli (VGE) production by varying decompression procedures is very common among divers. Several methods have been tried, either mechanical, cardiovascular, desaturation-aimed or biochemical, with encouraging results. In this study, we tested two different decompression methods: one called DEEP, where the decompression starts deeper, the other one SHALLOW, where shallower stops were planned, for the same dive and decompression time. Material and methods: In total, 18 healthy, non-smoking divers participated [1 female, 17 males; mean age 44.94 ± 5.74 years; body mass index (BMI) 27.3 ± 5.9 kg/m2]. Each diver performed two standardized Open Circuit trimix (21/35) dives, decompression mix EAN50. The deep profile used stops at 21, 18, 15, 12, 9, 6, and 3 meters. The shallow profile used stops at 9, 6, 3, with the same total bottom and decompression times for both groups. All dives were done in a pool (Y-40, Montegrotto, Italy) at a depth of 40 m for 40 min of bottom time and 80 minutes of total runtime. VGE counts were recorded every 15 min from 0 (0–5 min) to 90 min by echocardiography. Results: Vascular gas emboli were significantly reduced after the deep stops decompression procedure (DEEP: 6.7 ± 7.2 VGE per heartbeat vs. shallow: 10.7 ± 11.6 VGE per heartbeat, p = 0.0006). Three DCS cases were recorded after the “shallow” stop procedure (p = 0.24 Fisher’s exact test). Conclusions: There are significant differences between the two tested decompression procedures. The DEEP procedure resulted in a lower production of bubbles compared to the SHALLOW procedure.

Background: The association of patent foramen ovale (PFO) with cryptogenic stroke and decompression illness in SCUBA divers led to an increase in requests for echocardiographic detection of PFO in our department. The need for medically qualified personnel in performing these studies became a limiting factor. We describe the development of a technician-led screening service for PFO detection. Method: Permission from the local Health Trust …