Chest sonography detects lung water accumulation in healthy elite apnea divers

Breath-Hold Diving Injuries - A Primer for Medical Providers

ABSTRACT

Breath-hold divers, also known as freedivers, are at risk of specific injuries that are unique from those of surface swimmers and compressed air divers. Using peer-reviewed scientific research and expert opinion, we created a guide for medical providers managing breath-hold diving injuries in the field. Hypoxia induced by prolonged apnea and increased oxygen uptake can result in an impaired mental state that can manifest as involuntary movements or full loss of consciousness. Negative pressure barotrauma secondary to airspace collapse can lead to edema and/or hemorrhage. Positive pressure barotrauma secondary to overexpansion of airspaces can result in gas embolism or air entry into tissues and organs. Inert gas loading into tissues from prolonged deep dives or repetitive shallow dives with short surface intervals can lead to decompression sickness. Inert gas narcosis at depth is commonly described as an altered state similar to that experienced by compressed air divers. Asymptomatic cardiac arrhythmias are common during apnea, normally reversing shortly after normal ventilation resumes. The methods of glossopharyngeal breathing (insufflation and exsufflation) can add to the risk of pulmonary overinflation barotrauma or loss of consciousness from decreased cardiac preload. This guide also includes information for medical providers who are tasked with providing medical support at an organized breath-hold diving event with a list of suggested equipment to facilitate diagnosis and treatment outside of the hospital setting.

Exercise Stress Echocardiography in Athletes: Applications, Methodology, and Challenges

This comprehensive review explores the role of exercise stress echocardiography (ESE) in assessing cardiovascular health in athletes. Athletes often exhibit cardiovascular adaptations because of rigorous physical training, making the differentiation between physiological changes and potential pathological conditions challenging. ESE is a crucial diagnostic tool, offering detailed insights into an athlete's cardiac function, reserve, and possible arrhythmias. This review highlights the methodology of ESE, emphasizing its significance in detecting exercise-induced anomalies and its application in distinguishing between athlete's heart and other cardiovascular diseases. Recent advancements, such as LV global longitudinal strain (GLS) and myocardial work (MW), are introduced as innovative tools for the early detection of latent cardiac dysfunctions. However, the use of ESE also subsumes limitations and possible pitfalls, particularly in interpretation and potential false results, as explained in this article.

Relative hypoxemia at depth during breath-hold diving investigated through arterial blood gas analysis and lung ultrasound

Pulmonary gas exchange in breath-hold diving (BHD) consists of a progressive increase in arterial partial pressures of oxygen ([Formula: see text]) and carbon dioxide ([Formula: see text]) during descent. However, recent findings have demonstrated that [Formula: see text] does not consistently rise in all subjects. This study aimed at verifying and explaining [Formula: see text] derangements during BHD analyzing arterial blood gases and searching for pulmonary alterations with lung ultrasound. After ethical approval, 14 fit breath-hold divers were included. Experiments were performed in warm water (temperature: 31°C). We analyzed arterial blood gases immediately before, at depth, and immediately after a breath-hold dive to -15 m of fresh water (mfw) and -42 mfw. Signs of lung interstitial edema and atelectasis were searched simultaneously with a marinized lung ultrasound. In five subjects (-15 mfw) and four subjects (-42 mfw), the [Formula: see text] at depth seems to decrease instead of increasing. [Formula: see text] and lactate showed slight variations. At depth, no lung ultrasound alterations were seen except in one subject (hypoxemia and B-lines at -15 mfw; B-lines at the surface). Lung interstitial edema was detected in 3 and 12 subjects after resurfacing from -15 to -42 mfw, respectively. Two subjects developed hypoxemia at depth and a small lung atelectasis (a focal pleural irregularity of triangular shape, surrounded by thickened B-lines) after resurfacing from -42 mfw. Current experiments confirmed that some BH divers can experience hypoxemia at depth. The hypothesized explanation for such a discrepancy is lung atelectasis, which could not be detected in all subjects probably due to limited time available at depth.NEW & NOTEWORTHY During breath-hold diving, arterial partial pressure of oxygen ([Formula: see text]) and arterial partial pressure of carbon dioxide ([Formula: see text]) are believed to increase progressively during descent, as explained by theory, previous end-tidal alveolar gas measurements, and arterial blood gas analysis in hyperbaric chambers. Recent experiments in real underwater environment found a paradoxical [Formula: see text] drop at depth in some divers. This work confirms that some breath-hold divers can experience hypoxemia at depth. The hypothesized explanation for such a discrepancy is lung atelectasis, as suggested by lung ultrasound findings.

Machine Learning Algorithm Detection of Confluent B-Lines

OBJECTIVE

B-lines are a ring-down artifact of lung ultrasound that arise with increased alveolar water in conditions such as pulmonary edema and infectious pneumonitis. Confluent B-line presence may signify a different level of pathology compared with single B-lines. Existing algorithms aimed at B-line counting do not distinguish between single and confluent B-lines. The objective of this study was to test a machine learning algorithm for confluent B-line identification.

METHODS

This study used a subset of 416 clips from 157 subjects, previously acquired in a prospective study enrolling adults with shortness of breath at two academic medical centers, using a hand-held tablet and a 14-zone protocol. After exclusions, random sampling generated a total of 416 clips (146 curvilinear, 150 sector and 120 linear) for review. A group of five experts in point-of-care ultrasound blindly evaluated the clips for presence/absence of confluent B-lines. Ground truth was defined as majority agreement among the experts and used for comparison with the algorithm.

RESULTS

Confluent B-lines were present in 206 of 416 clips (49.5%). Sensitivity and specificity of confluent B-line detection by algorithm compared with expert determination were 83% (95% confidence interval [CI]: 0.77-0.88) and 92% (95% CI: 0.88-0.96). Sensitivity and specificity did not statistically differ between transducers. Agreement between algorithm and expert for confluent B-lines measured by unweighted κ was 0.75 (95% CI: 0.69-0.81) for the overall set.

CONCLUSION

The confluent B-line detection algorithm had high sensitivity and specificity for detection of confluent B-lines in lung ultrasound point-of-care clips, compared with expert determination.

Diagnostic ultrasound imaging of the lung: A simulation approach based on propagation and reverberation in the human body

Although ultrasound cannot penetrate a tissue/air interface, it images the lung with high diagnostic accuracy. Lung ultrasound imaging relies on the interpretation of "artifacts," which arise from the complex reverberation physics occurring at the lung surface but appear deep inside the lung. This physics is more complex and less understood than conventional B-mode imaging in which the signal directly reflected by the target is used to generate an image. Here, to establish a more direct relationship between the underlying acoustics and lung imaging, simulations are used. The simulations model ultrasound propagation and reverberation in the human abdomen and at the tissue/air interfaces of the lung in a way that allows for direct measurements of acoustic pressure inside the human body and various anatomical structures, something that is not feasible clinically or experimentally. It is shown that the B-mode images beamformed from these acoustical simulations reproduce primary clinical features that are used in diagnostic lung imaging, i.e., A-lines and B-lines, with a clear relationship to known underlying anatomical structures. Both the oblique and parasagittal views are successfully modeled with the latter producing the characteristic "bat sign," arising from the ribs and intercostal part of the pleura. These simulations also establish a quantitative link between the percentage of fluid in exudative regions and the appearance of B-lines, suggesting that the B-mode may be used as a quantitative imaging modality.

Sonographic Evaluation of Pulmonary Interstitial Edema in Patient With Preeclampsia

ABSTRACT

The aim of this study was to sonographically detect pulmonary edema, which is a major problem in pregnant women with preeclampsia, in the interstitial phase. We evaluated 41 preeclampsia patients and 21 control subjects prospectively. In the preeclampsia group, 26 patients had severe features, whereas the other 15 patients had none. To detect early fluid loading in lungs, sonographic B lines were counted from the intercostal space by using ultrasonography, and left ventricular loading findings were examined for corporation by using transthoracic echocardiography both before and after birth. In severe preeclampsia, the number of B lines before and after birth is statistically significant compared with the other groups. In addition, the total number of B lines calculated at 24 hours after delivery was significantly lower than that calculated before delivery (P < 0.018). In terms of prenatal E values, a statistically significant difference was found between all groups (P < 0.001). A strong positive and statistically significant relationship was found between B lines and prenatal E/e' (r = 0.768; P < 0.001). The overall accuracy rate of the prenatal E/e' and E value for estimation of the B line number classification is 0.791 (95% confidence interval, 0.674-0.908; P < 0.001) and 0.829 (95% confidence interval, 0.722-0.936; P < 0.001), respectively. Pulmonary edema is a serious complication in patients with severe preeclampsia and may be detected interstitially in some patients, even if it does not occur clinically.

Association Between Arterial Oxygen Saturation and Lung Ultrasound B-Lines After Competitive Deep Breath-Hold Diving

Breath-hold diving (freediving) is an underwater sport that is associated with elevated hydrostatic pressure, which has a compressive effect on the lungs that can lead to the development of pulmonary edema. Pulmonary edema reduces oxygen uptake and thereby the recovery from the hypoxia developed during freediving, and increases the risk of hypoxic syncope. We aimed to examine the efficacy of SpO₂, via pulse-oximetry, as a tool to detect pulmonary edema by comparing it to lung ultrasound B-line measurements after deep diving. SpO₂ and B-lines were collected in 40 freedivers participating in an international deep freediving competition. SpO₂ was measured within 17 ± 6 min and lung B-lines using ultrasound within 44 ± 15 min after surfacing. A specific symptoms questionnaire was used during SpO₂ measurements. We found a negative correlation between B-line score and minimum SpO₂ (r_s = −0.491; p = 0.002) and mean SpO₂ (r_s = −0.335; p = 0.046). B-line scores were positively correlated with depth (r_s = 0.408; p = 0.013), confirming that extra-vascular lung water is increased with deeper dives. Compared to dives that were asymptomatic, symptomatic dives had a 27% greater B-line score, and both a lower mean and minimum SpO₂ (all p < 0.05). Indeed, a minimum SpO₂ ≤ 95% after a deep dive has a positive predictive value of 29% and a negative predictive value of 100% regarding symptoms. We concluded that elevated B-line scores are associated with reduced SpO₂ after dives, suggesting that SpO₂ via pulse oximetry could be a useful screening tool to detect increased extra-vascular lung water. The practical application is not to diagnose pulmonary edema based on SpO₂ – as pulse oximetry is inexact – rather, to utilize it as a tool to determine which divers require further evaluation before returning to deep freediving.

Immersion pulmonary oedema in a triathlete - a diagnostic challenge in sports cardiology

Immersion pulmonary oedema, also referred to as swimming-induced pulmonary oedema, is a form of pulmonary oedema which usually occurs during swimming in cold water. The condition is most common in triathlon athletes; it was first reported in military divers. The main symptoms include acute dyspnoea, cough, and occasionally haemoptysis, which usually subside within approximately 48 hours. The pathomechanism is not fully understood, but oedema is suspected to be due to an increased systemic vascular resistance that overloads the left ventricle. The diagnostic process can be challenging and require multiple stages to rule out a number of other possible conditions. In view of the circumstances in which incidents typically occur, immersion pulmonary oedema poses an immediate life threat to individuals involved in selected forms of physical activity, where survival is often determined by appropriate training of medical services.

B-Line Artifact as a Diagnostic Tool in Various Conditions at the Emergency Department

BACKGROUND: B-line artifacts (BLAs) play an important role in identifying lung pathology. They may indicate different diseases. However, the diagnostic study of BLA as applied to emergency patients has not been well studied. AIM: The aim of this study was to determine the diagnostic accuracy of BLA in various conditions. METHODS: This was a retrospective observational study of emergency patients who had received lung ultrasound at Srinagarind Hospital’s Emergency Department throughout January 2020–December 2020. Ultrasound artifacts were recorded. Ultrasonography findings were correlated with final diagnosis. Sensitivity and specificity were also calculated. RESULTS: A total of 105 patients were evaluated. The most prevalent condition which BLA found in this study was pulmonary edema (44.12%) with 88.24% sensitivity and 46.48% specificity. BLA also indicated pneumonia with 66.67% sensitivity and 35.71% specificity. Diffuse BLA indicated pulmonary edema with 70% sensitivity and 70.42% specificity. Focal BLA indicated pneumonia with 28.57% sensitivity and 76.19% specificity. CONCLUSIONS: The sensitivity of BLA for pulmonary edema and pneumonia diagnosis in this study was of moderate to good sensitivity, but low specificity. BLA may become crucial in the diagnosis of lung pathology in the emergency department.

Temporal changes in pulmonary gas exchange efficiency when breath-hold diving below residual volume

NEW FINDINGS

What is the central question of this study? How does deep breath-hold diving impact cardiopulmonary function, both acutely and over the subsequent 2.5 hours post-dive? What is the main finding and its importance? Breath-hold diving, to depths below residual volume, is associated with acute impairments in pulmonary gas exchange, which typically resolve within 2.5 hours. These data provide new insight into the behaviour of the lungs and pulmonary vasculature following deep diving.

ABSTRACT

Breath-hold diving involves highly integrative and extreme physiological responses to both exercise and asphyxia during progressive elevations in hydrostatic pressure. Over two diving training camps (Study 1 and 2), 25 breath-hold divers (recreational to world-champion) performed 66 dives to 57 ± 20 m (range: 18-117 m). Using the deepest dive from each diver, temporal changes in cardiopulmonary function were assessed using non-invasive pulmonary gas exchange (indexed via the O₂ deficit), ultrasound B-line scores, lung compliance and pulmonary haemodynamics at baseline and following the dive. Hydrostatically induced lung compression was quantified in Study 2, using spirometry and lung volume measurement, enabling each dive to be categorized by its residual volume (RV)-equivalent depth. From both studies, pulmonary gas exchange inefficiency - defined as an increase in O₂ deficit - was related to the depth of the dive (r²  = 0.345; P < 0.001), with dives associated with lung squeeze symptoms exhibiting the greatest deficits. In Study 1, although B-lines doubled from baseline (P = 0.027), cardiac output and pulmonary artery systolic pressure were unchanged post-dive. In Study 2, dives with lung compression to ≤RV had higher O₂ deficits at 9 min, compared to dives that did not exceed RV (24 ± 25 vs. 5 ± 8 mmHg; P = 0.021). The physiological significance of a small increase in estimated lung compliance post-dive (via decreased and increased/unaltered airway resistance and reactance, respectively) remains equivocal. Following deep dives, the current study highlights an integrated link between hydrostatically induced lung compression and transient impairments in pulmonary gas exchange efficiency.

Hook Breathing Facilitates SaO2 Recovery After Deep Dives in Freedivers With Slow Recovery

To facilitate recovery from hypoxia, many freedivers use a breathing method called “hook breathing” (HB) after diving, involving an interrupted exhale to build up intrapulmonary pressure. Some divers experience a delay in recovery of arterial oxygen saturation (SaO₂) after diving, interpreted as symptoms of mild pulmonary edema, and facilitated recovery may be especially important in this group to avoid hypoxic “blackout.” We examined the influence of HB on recovery of SaO₂ in freedivers with slow recovery (SR) and fast recovery (FR) of SaO₂ after deep “free immersion” (FIM) apnea dives to 30 m depth. Twenty-two male freedivers, with a mean (SD) personal best in the discipline FIM of 57(26) m, performed two 30 m deep dives, one followed by HB and one using normal breathing (NB) during recovery, at different days and weighted order. SaO₂ and heart rate (HR) were measured via pulse oximetry during recovery. The SR group (n = 5) had a faster SaO₂ recovery using HB, while the FR group (n = 17) showed no difference between breathing techniques. At 105 s, the SR group reached a mean (SD) SaO₂ of 95(5)% using HB, while using NB, their SaO₂ was 87(5)% (p < 0.05), and 105–120 s after surfacing SaO₂ was higher with HB (p < 0.05). In SR subjects, the average time needed to reach 95% SaO₂ with HB was 60 s, while it was 120 s at NB (p < 0.05). HR was similar in the SR group, while it was initially elevated at HB in the FR group (p < 0.05). We conclude that HB efficiently increases SaO₂ recovery in SR individuals, but not in the FR group. The proposed mechanism is that increased pulmonary pressure with HB will reverse any pulmonary edema and facilitate oxygen uptake in divers with delayed recovery.

Effects of Breath-Hold Deep Diving on the Pulmonary System

This short review focuses on pulmonary injury in breath-hold (BH) divers. When practicing their extreme leisure sport, they are exposed to increased pressure on pulmonary gas volumes, hypoxia, and increased partial gas pressures. Increasing ambient pressures do present a serious problem to BH deep divers, because the semi-rigid thorax prevents the deformation required by the Boyle-Mariotte law. As a result, a negative-pressure barotrauma (lung squeeze) with acute hemoptysis is not uncommon. Respiratory maneuvers such as glossopharyngeal insufflation (GI) and glossopharyngeal exsufflation (GE) are practiced to prevent lung squeeze and to permit equalizing the paranasal sinuses and the middle ear. GI not only impairs venous return, thereby provoking hypotension and even fainting, but also produces intrathoracic pressures likely to induce pulmonary barotrauma that is speculated to induce long-term injury. GE, in turn, further increases the already negative intrapulmonary pressure, thereby favoring alveolar collapse (atelectasis). Finally, hypoxia seemingly not only induces brain injury but initiates the opening of intrapulmonary shunts. These pathways are large enough to permit transpulmonary passage of venous N2 bubbles, making stroke-like phenomena in deep BH divers possible.

A New Modality for the Diagnosis of Bleomycin-induced Toxicity: Ultrasonography

OBJECTIVE

To evaluate the role of ultrasonography (USG) in the diagnosis of bleomycin-induced pulmonary toxicity (BT).

MATERIAL AND METHODS

The study included patients with suspected BT during treatment with bleomycin due to various oncologic diseases between June 2015 and May 2017. The patients initially underwent clinical and high-resolution computed tomography (HRCT) examinations and pulmonary function tests (PFT)-diffusing capacity of the lung for carbon monoxide (DLCO), followed by registration of USG findings-number of comet tail artifact (CTA) images by a different pulmonologist. We compared the findings from USG, HRCT, and PFT-DLCO tests between BT and non-BT groups. With the diagnosis based on clinical-radiologic and PFT-DLCO assessments taken as the gold standard, we determined the sensitivity and specificity of the USG outcomes for diagnosis of BT.

RESULTS

The study included a total of 30 patients. Nine patients were diagnosed as having BT according to their clinical and radiologic findings and PFT-DLCO measurements. The mean number of CTA images was 68.7±22 in patients with BT vs 28.2±9.3 in those without BT (P<.001). The difference in CTA images between the patients with and without ground glass density was statistically significant (28.3±9.5 and 64.6±24.5, respectively, P<.001). In patients with BT, there was a negative correlation between the number of CTAs and DLCO% and FVC% values (P=.004; P=.016). USG had a sensitivity of 100%, and a specificity of 95% diagnosing BT in selected patients.

CONCLUSION

In bleomycin-induced toxicity, USG findings are correlated with HRCT and PFT-DLCO findings, with a remarkably increased number of CTAs in BT. Thoracic USG examination is a diagnostic tool with a high sensitivity and specificity for diagnosing BT.

Stressing the Cardiopulmonary Vascular System: The Role of Echocardiography

The cardiopulmonary vascular system represents a key determinant of prognosis in several cardiorespiratory diseases. Although right heart catheterization is considered the gold standard for assessing pulmonary hemodynamics, a comprehensive noninvasive evaluation including left and right ventricular reserve and function and cardiopulmonary interactions remains highly attractive. Stress echocardiography is crucial in the evaluation of many cardiac conditions, typically coronary artery disease but also heart failure and valvular heart disease. In stress echocardiographic applications beyond coronary artery disease, the assessment of the cardiopulmonary vascular system is a cornerstone. The possibility of coupling the left and right ventricles with the pulmonary circuit during stress can provide significant insight into cardiopulmonary physiology in healthy and diseased subjects, can support the diagnosis of the etiology of pulmonary hypertension and other conditions, and can offer valuable prognostic information. In this state-of-the-art document, the topic of stress echocardiography applied to the cardiopulmonary vascular system is thoroughly addressed, from pathophysiology to different stress modalities and echocardiographic parameters, from clinical applications to limitations and future directions.

Chest Ultrasonography in Modern Day Extreme Settings: From Military Setting and Natural Disasters to Space Flights and Extreme Sports

Chest ultrasonography (CU) is a noninvasive imaging technique able to provide an immediate diagnosis of the underlying aetiology of acute respiratory failure and traumatic chest injuries. Given the great technologies, it is now possible to perform accurate CU in remote and adverse environments including the combat field, extreme sport settings, and environmental disasters, as well as during space missions. Today, the usage of CU in the extreme emergency setting is more likely to occur, as this technique proved to be a fast diagnostic tool to assist resuscitation manoeuvres and interventional procedures in many cases. A scientific literature review is presented here. This was based on a systematic search of published literature, on the following online databases: PubMed and Scopus. The following words were used: "chest sonography," " thoracic ultrasound," and "lung sonography," in different combinations with "extreme sport," "extreme environment," "wilderness," "catastrophe," and "extreme conditions." This manuscript reports the most relevant usages of CU in the extreme setting as well as technological improvements and current limitations. CU application in the extreme setting is further encouraged here.

Lung ultrasound predicts acute respiratory distress syndrome in patients with paraquat intoxication

Objective:

We assessed the evolution of lung aeration by “Lung Ultrasound Score” to predict the acute respiratory distress syndrome in patients with paraquat intoxication.

Methods:

Patients with paraquat intoxication treated in the intensive care unit were reviewed. Patients who had been assessed by transthoracic lung ultrasound at 3 time points as day 1, day 3, and day 7 after the treatment were analyzed. Lung aeration was represented by the lung ultrasound score. The relationship of the score with the development of acute respiratory distress syndrome was evaluated.

Results:

There were 50 patients included. On day 7, 18 patients developed the acute respiratory distress syndrome. The acute respiratory distress syndrome patients demonstrated a higher mortality rate than that for the non-acute respiratory distress syndrome patients (88.9% vs 31.5%, p < 0.001). In addition, the acute respiratory distress syndrome patients not only had a higher creatinine level (p < 0.001), and Sepsis-related Organ Failure Assessment 48-h scores (p < 0.001), and a longer time to gastric lavage but also suffered from a lower PaO2/FiO2 (p < 0.001) and a higher lung ultrasound score (p < 0.001) compared to those in the non-acute respiratory distress syndrome patients. The decrease in PaO2/FiO2 between day 3 and day 7 correlated with the increase in lung ultrasound score between day 3 and day 7. There was also a significant correlation between the Sepsis-related Organ Failure Assessment score and lung ultrasound score in acute respiratory distress syndrome patient on day 7.

Conclusion:

The transthoracic lung ultrasound may be a useful tool for lung aeration assessment on patients with paraquat intoxication receiving treatment. Further studies are needed to evaluate the impact of this screening strategy on predicting acute respiratory distress syndrome.

B-lines with Lung Ultrasound: The Optimal Scan Technique at Rest and During Stress

Various lung ultrasound (LUS) scanning modalities have been proposed for the detection of B-lines, also referred to as ultrasound lung comets, which are an important indication of extravascular lung water at rest and after exercise stress echo (ESE). The aim of our study was to assess the lung water spatial distribution (comet map) at rest and after ESE. We performed LUS at rest and immediately after semi-supine ESE in 135 patients (45 women, 90 men; age 62 ± 12 y, resting left ventricular ejection fraction = 41 ± 13%) with known or suspected heart failure or coronary artery disease. B-lines were measured by scanning 28 intercostal spaces (ISs) on the antero-lateral chest, 2nd-5th IS, along with the midaxillary (MA), anterior axillary (AA), mid-clavicular (MC) and parasternal (PS) lines. Complete 28-region, 16-region (3rd and 4th IS), 8-region (3rd IS), 4-region (3rd IS, only AA and MA) and 1-region (left 3rd IS, MA) scans were analyzed. In each space, the B-lines were counted from 0 = black lung to 10 = white lung. Interpretable images were obtained in all spaces (feasibility = 100 %). B-lines (>0 in at least 1 space) were present at ESE in 93 patients (69%) and absent in 42. More B-lines were found in the 3rd IS and along AA and MA lines. The B-line cumulative distribution was symmetric at rest (right/left = 1.10) and asymmetric with left lung predominance during stress (right/left = 0.67). The correlation of per-patient B-line number between 28-S and 16-S (R² = 0.9478), 8-S (R² = 0.9478) and 4-S scan (R² = 0.9146) was excellent, but only good with 1-S (R² = 0.8101). The average imaging and online analysis time were 5 s per space. In conclusion, during ESE, the comet map of lung water accumulation follows a predictable spatial pattern with wet spots preferentially aligned with the third IS and along the AA and MA lines. The time-saving 4-region scan is especially convenient during stress, simply dismissing dry regions and focusing on wet regions alone.

Observational study of potential risk factors of immersion pulmonary edema in healthy divers: exercise intensity is the main contributor

BACKGROUND

The risk factors of pulmonary edema induced by diving in healthy subjects are not well known. The aim of the present study was to assess the parameters contributing to the increase in extravascular lung water after diving.

METHODS

This study was carried out in a professional diving institute. All divers participating in the teaching program from June 2012 to June 2014 were included in the study. Extravascular lung water was assessed using the detection of ultrasound lung comets (ULC) by chest ultrasonography. Clinical parameters and dive profiles were recorded using a questionnaire and a dive computer.

RESULTS

One-hundred six divers were investigated after 263 dives. They used an open-circuit umbilical supplying compressed gas diving apparatus in 202 cases and a self-contained underwater breathing apparatus in 61 cases. A generalized linear mixed model analysis was performed which demonstrated that the dive induced a significant increase in ULC score (incidence rate ratio: 3.16). It also identified that the predictive variable of increased extravascular lung water after the dive was the exercise intensity at depth (z = 3.99, p < 0.0001). The other parameters studied such as the water temperature, dive profile, hyperoxic exposure, or anthropometric data were not associated with the increase in extravascular lung water after the dive.

CONCLUSIONS

In this study, the exercise intensity was the main contributor to the increase in extravascular lung water in healthy divers. To improve the prevention of immersion pulmonary edema, the exercise intensity experienced during the dive should thus be adapted to the aerobic fitness level of the divers.

Stress echo 2020: the international stress echo study in ischemic and non-ischemic heart disease

BACKGROUND

Stress echocardiography (SE) has an established role in evidence-based guidelines, but recently its breadth and variety of applications have extended well beyond coronary artery disease (CAD). We lack a prospective research study of SE applications, in and beyond CAD, also considering a variety of signs in addition to regional wall motion abnormalities.

METHODS

In a prospective, multicenter, international, observational study design, > 100 certified high-volume SE labs (initially from Italy, Brazil, Hungary, and Serbia) will be networked with an organized system of clinical, laboratory and imaging data collection at the time of physical or pharmacological SE, with structured follow-up information. The study is endorsed by the Italian Society of Cardiovascular Echography and organized in 10 subprojects focusing on: contractile reserve for prediction of cardiac resynchronization or medical therapy response; stress B-lines in heart failure; hypertrophic cardiomyopathy; heart failure with preserved ejection fraction; mitral regurgitation after either transcatheter or surgical aortic valve replacement; outdoor SE in extreme physiology; right ventricular contractile reserve in repaired Tetralogy of Fallot; suspected or initial pulmonary arterial hypertension; coronary flow velocity, left ventricular elastance reserve and B-lines in known or suspected CAD; identification of subclinical familial disease in genotype-positive, phenotype- negative healthy relatives of inherited disease (such as hypertrophic cardiomyopathy).

RESULTS

We expect to recruit about 10,000 patients over a 5-year period (2016-2020), with sample sizes ranging from 5,000 for coronary flow velocity/ left ventricular elastance/ B-lines in CAD to around 250 for hypertrophic cardiomyopathy or repaired Tetralogy of Fallot. This data-base will allow to investigate technical questions such as feasibility and reproducibility of various SE parameters and to assess their prognostic value in different clinical scenarios.

CONCLUSIONS

The study will create the cultural, informatic and scientific infrastructure connecting high-volume, accredited SE labs, sharing common criteria of indication, execution, reporting and image storage of SE to obtain original safety, feasibility, and outcome data in evidence-poor diagnostic fields, also outside the established core application of SE in CAD based on regional wall motion abnormalities. The study will standardize procedures, validate emerging signs, and integrate the new information with established knowledge, helping to build a next-generation SE lab without inner walls.

Ultrasound of extravascular lung water: a new standard for pulmonary congestion

Extravascular lung water (EVLW) is a key variable in heart failure management and prognosis, but its objective assessment remains elusive. Lung imaging has been traditionally considered off-limits for ultrasound techniques due to the acoustic barrier of high-impedance air wall. In pulmonary congestion however, the presence of both air and water creates a peculiar echo fingerprint. Lung ultrasound shows B-lines, comet-like signals arising from a hyper-echoic pleural line with a to-and-fro movement synchronized with respiration. Increasing EVLW accumulation changes the normal, no-echo signal (black lung, no EVLW) into a black-and-white pattern (interstitial sub-pleural oedema with multiple B-lines) or a white lung pattern (alveolar pulmonary oedema) with coalescing B-lines. The number and spatial extent of B-lines on the antero-lateral chest allows a semi-quantitative estimation of EVLW (from absent, ≤5, to severe pulmonary oedema, >30 B-lines). Wet B-lines are made by water and decreased by diuretics, which cannot modify dry B-lines made by connective tissue. B-lines can be evaluated anywhere (including extreme environmental conditions with pocket size instruments to detect high-altitude pulmonary oedema), anytime (during dialysis to titrate intervention), by anyone (even a novice sonographer after 1 h training), and on anybody (since the chest acoustic window usually remains patent when echocardiography is not feasible). Cardiologists can achieve much diagnostic gain with little investment of technology, training, and time. B-lines represent 'the shape of lung water'. They allow non-invasive detection, in real time, of even sub-clinical forms of pulmonary oedema with a low cost, radiation-free approach.

Lung B-line artefacts and their use

BACKGROUND

The analysis of lung artefacts has gained increasing importance as markers of lung pathology. B-line artefact (BLA), caused by a reverberation phenomenon, is the most important lung artefact. In this review, we discuss the current role of BLA in pneumology and explore open questions of the published consensus.

METHODS

We summarized current literature about BLA. Also, we presented observations on healthy subjects and patients with interstitial syndrome (pulmonary fibrosis and edema), to investigate technical factors influencing BLA visualization.

RESULTS

BLA imaging is influenced by more factors than recently assumed. When multiple BLA is visualized in the lung, they represent a sign of increased density due to the loss of aeration in the lung periphery. This condition may indicate different diseases including cardiogenic pulmonary edema, diffuse or focal interstitial lung diseases (ILD), infections and acute respiratory distress syndrome (ARDS). Correct interpretation of BLA in lung ultrasound is strongly influenced by associated sonographic signs and careful integration of all relevant clinical information.

CONCLUSIONS

BLA is useful to monitor clinical response, and may become crucial in directing the diagnostic process. Further research is warranted to clarify technical adjustments, different probe and machine factors that influence the visualization of BLA.

Imaging Congestion With a Pocket Ultrasound Device: Prognostic Implications in Patients With Chronic Heart Failure

BACKGROUND

Venous congestion is common in patients with chronic heart failure (HF). We used a pocket-sized ultrasound imaging device (PID) to assess the patients' congestive status and related our findings to prognosis.

METHODS AND RESULTS

One hundred four consecutive outpatients from an HF outpatient clinic were studied. Interstitial lung water (ILW), pleural effusion (PE), and the diameter of the inferior vena cava (VCI) were assessed with the use of a PID. ILW was assessed by demonstration of B-lines (comet tail artifact (CTA). Out of the 104 patients, 28 had CTA and 8 had PE. Median VCI diameter was 18 mm (interquartile range 14-22 mm). Each of these parameters correlated weakly (r = 0.26-0.37; P < .05) with the HF biomarker N-terminal pro-B-type natriuretic peptide (NT-proBNP). During the median follow-up time of 530 days, 18 hospitalizations and 14 deaths were registered. Findings of CTA, PE, or both increased the risk of death or hospitalization (hazard ratio 3-4; P < .05). After adjustment for age, cardiac systolic function, and NT-proBNP, this difference remained significant for CTA alone and CTA + PE combined, but not for PE alone.

CONCLUSIONS

With the use of a handheld ultrasound device, signs of pulmonary congestion could be demonstrated. When found, these had a significant prognostic impact in clinically stable HF.

Ultrasonography for clinical decision-making and intervention in airway management: from the mouth to the lungs and pleurae

OBJECTIVES

To create a state-of-the-art overview of the new and expanding role of ultrasonography in clinical decision-making, intervention and management of the upper and lower airways, that is clinically relevant, up-to-date and practically useful for clinicians.

METHODS

This is a narrative review combined with a structured Medline literature search.

RESULTS

Ultrasonography can be utilised to predict airway difficulty during induction of anaesthesia, evaluate if the stomach is empty or possesses gastric content that poses an aspiration risk, localise the essential cricothyroid membrane prior to difficult airway management, perform nerve blocks for awake intubation, confirm tracheal or oesophageal intubation and facilitate localisation of tracheal rings for tracheostomy. Ultrasonography is an excellent diagnostic tool in intraoperative and emergency diagnosis of pneumothorax. It also enables diagnosis and treatment of interstitial syndrome, lung consolidation, atelectasis, pleural effusion and differentiates causes of acute breathlessness during pregnancy. Patient safety can be enhanced by performing procedures under ultrasound guidance, e.g. thoracocentesis, vascular line access and help guide timing of removal of chest tubes by quantification of residual pneumothorax size.

CONCLUSIONS

Ultrasonography used in conjunction with hands-on management of the upper and lower airways has multiple advantages. There is a rapidly growing body of evidence showing its benefits.

TEACHING POINTS

• Ultrasonography is becoming essential in management of the upper and lower airways. • The tracheal structures can be identified by ultrasonography, even when unidentifiable by palpation. • Ultrasonography is the primary diagnostic approach in suspicion of intraoperative pneumothorax. • Point-of-care ultrasonography of the airways has a steep learning curve. • Lung ultrasonography allows treatment of interstitial syndrome, consolidation, atelectasis and effusion.

Lung ultrasound for the evaluation of pulmonary congestion in outpatients: a comparison with clinical assessment, natriuretic peptides, and echocardiography

OBJECTIVES

The aim of this study was to define the performance of lung ultrasound (LUS) compared with clinical assessment, natriuretic peptides, and echocardiography, to evaluate decompensation in patients with systolic heart failure (HF) in an outpatient clinic.

BACKGROUND

Evaluation of pulmonary congestion in chronic HF is challenging. LUS has been recently proposed as a reliable tool for the semiquantification of extravascular lung water through assessment of B-lines.

METHODS

This was a cohort study of patients with moderate to severe systolic HF. Receiver-operating characteristic (ROC) analyses were performed to compare LUS with a previously validated clinical congestion score (CCS), amino-terminal portion of B-type natriuretic peptide (NT-proBNP), E/e' ratio, chest x-ray, and 6-min walk test.

RESULTS

Ninety-seven patients were enrolled. Decompensation was present in 57.7% of patients when estimated by CCS, 68% by LUS, 53.6% by NT-proBNP, and 65.3% by E/e' ≥15. The number of B-lines was correlated to NT-proBNP (r = 0.72; p < 0.0001), E/e' (r = 0.68; p < 0.0001), and CCS (r = 0.43; p < 0.0001). In ROC analyses, considering as reference for decompensation a combined method (E/e' ≥ 15 and/or NT-proBNP >1,000 pg/ml), LUS yielded a C-statistic of 0.89 (95% confidence interval: 0.82 to 0.96), providing the best accuracy with a cutoff ≥ 15 B-lines (sensitivity 85%, specificity 83%). A systematic approach using CCS, E/e', NT-proBNP, chest x-ray, and 6-min walk test in different combinations as reference for decompensation also corroborated this cutoff and found a similar accuracy for LUS.

CONCLUSIONS

In an HF outpatient clinic, B-lines were significantly correlated with more established parameters of decompensation. A B-line ≥15 cutoff could be considered for a quick and reliable assessment of decompensation in outpatients with HF.

Clinical review: the role of ultrasound in estimating extra-vascular lung water

The estimation of extra-vascular lung water (EVLW) is an essential component in the assessment of critically ill patients. EVLW is independently associated with mortality and its manipulation has been shown to improve outcome. Accurate assessment of lung water is possible with CT and MR imaging but these are impractical for real-time measurement in sick patients and have been superseded by single thermal dilution techniques. While useful, single thermo-dilution requires repeated calibration and is prone to error, suggesting a need for other monitoring methods. Traditionally the lung was not thought amenable to ultrasound examination owing to the high acoustic impedance of air; however, the identification of artefacts in diseased lung has led to increased use of ultrasound as a point of care investigation for both diagnosis and to monitor response to interventions. Following the initial description of B-lines in association with increased lung water, accumulating evidence has shown that they are a useful and responsive measure of the presence and dynamic changes in EVLW. Animal models have confirmed a correlation with lung gravimetry and the utility of B-lines has been demonstrated in many clinical situations and correlated against other established measures of EVLW. With increasing availability and expertise the role of ultrasound in estimating EVLW should be embedded in clinical practice and incorporated into clinical algorithms to aid decision making. This review looks at the evidence for ultrasound as a valid, easy to use, non-invasive point of care investigation to assess EVLW.

Inter-rater reliability of quantifying pleural B-lines using multiple counting methods

OBJECTIVES

Sonographic B-lines are a sign of increased extravascular lung water. Several techniques for quantifying B-lines within individual rib spaces have been described, as well as different methods for "scoring" the cumulative B-line counts over the entire thorax. The interobserver reliability of these methods is unknown. This study examined 3 methods of quantifying B-lines for inter-rater reliability.

METHODS

Videotaped pleural assessments of adult patients presenting to the emergency department with dyspnea and suspected acute heart failure were reviewed by 3 blinded pairs of emergency physicians. Each pair performed B-line counts within single rib spaces using 1 of the following 3 predetermined methods: 1, individual B-lines are counted over an entire respiratory cycle; 2, as per method 1, but confluent B-lines are counted as multiple based on the percentage of the rib space they occupy; and 3, as per method 2, but the count is made at the moment when the most B-lines are seen, not over an entire respiratory cycle. A single-measures interclass correlation coefficient was used to assess inter-rater reliability for the 3 definitions of B-line counts.

RESULTS

A total of 456 video clips were reviewed. The interclass correlation coefficients (95% confidence intervals) for methods 1, 2, and 3 were 0.84 (0.81-0.87), 0.87 (0.85-0.90), and 0.89 (0.87-0.91), respectively. The difference between methods 1 and 3 was significant (P = .003).

CONCLUSIONS

All methods of B-line quantification showed substantial inter-rater agreement. Method 3 is more reliable than method 1. There were no other significant differences between the methods. We recommend the use of method 3 because it is technically simpler to perform and more reliable than method 1.

Ultrasound assessment of lung aeration loss during a successful weaning trial predicts postextubation distress*

OBJECTIVE

Postextubation distress after a successful spontaneous breathing trial is associated with increased morbidity and mortality. Predicting postextubation distress is therefore a major issue in critically ill patients. To assess whether lung derecruitment during spontaneous breathing trial assessed by lung ultrasound is predictive of postextubation distress.

DESIGN AND SETTING

Prospective study in two multidisciplinary intensive care units within University Hospital.

PATIENTS AND METHODS

One hundred patients were included in the study. Lung ultrasound, echocardiography, and plasma B-type natriuretic peptide levels were determined before and at the end of a 60-min spontaneous breathing trial and 4 hrs after extubation. To quantify lung aeration, a lung ultrasound score was calculated. Patients were followed up to hospital discharge.

MEASUREMENTS AND MAIN RESULTS

Fourteen patients failed the spontaneous breathing trial, 86 were extubated, 57 were definitively weaned (group 1), and 29 suffered from postextubation distress (group 2). Loss of lung aeration during the successful spontaneous breathing trial was observed only in group 2 patients: lung ultrasound scores increased from 15 [13;17] to 19 [16; 21] (p < .01). End-spontaneous breathing trial lung ultrasound scores were significantly higher in group 2 than in group 1 patients: 19 [16;21] vs. 10 [7;13], respectively (p < .001) and predicted postextubation distress with an area under the receiver operating characteristic curve of 0.86. Although significantly higher in group 2, B-type natriuretic peptide and echocardiography cardiac filling pressures were not clinically helpful in predicting postextubation distress.

CONCLUSION

Lung ultrasound determination of aeration changes during a successful spontaneous breathing trial may accurately predict postextubation distress.

The promising role of lung ultrasound in systemic sclerosis

Ultrasound (US) has an emergent and relevant role in the assessment of systemic sclerosis (SSc) even if there are many fields and applications that still have not been sufficiently explored. In this review, we will report an update of the available data regarding the use of US in lung involvement that might cause disability and mortality in SSc patients. Lung US does not employ ionizing radiation and is more rapid and less expensive than traditional high-resolution tomography (HRCT). Furthermore, recent initial studies have demonstrated that US scores correlated to HRCT and functional respiratory test results in SSc interstitial lung disease. The research agenda for the future should include a more profound investigation of its specificity (comparison with healthy subjects and other diseases) and sensitivity to change at follow-up, to adequately disseminate its use in daily practice and clinical trials.

Portable bedside ultrasound: the visual stethoscope of the 21st century

Over the past decade technological advances in the realm of ultrasound have allowed what was once a cumbersome and large machine to become essentially hand-held. This coupled with a greater understanding of lung sonography has revolutionized our bedside assessment of patients. Using ultrasound not as a diagnostic test, but instead as a component of the physical exam, may allow it to become the stethoscope of the 21st century.

Heart rate variability in free diving athletes

The aim of the study was to evaluate the cardiac autonomic activity in free diving (FD) athletes. Thirteen Greek male free divers (group I, aged 33.4 ± 6.3 years, 6.6 ± 4.5 years of training experience) volunteered to participate while 13 age-matched sedentary subjects served as control group (group II). All subjects were submitted to ambulatory 24-h ECG recording for heart rate variability (HRV) analysis on a day of regular activities with no exercise or training. The results showed that group I had significantly lower minimum and mean heart rate by 23.9% (P < 0.001) and 20.6% (P < 0.001), respectively. All the measured time and frequency domain indices of HRV which reflect cardiac parasympathetic activity were higher in group I than in group II by 37.6% to 146% (P < 0.001). Conclusively, the resting cardiac autonomic activity and especially the parasympathetic branch was significantly increased in free divers compared to untrained subjects. This finding should be rather attributed to the accumulated effect of both exercise training and frequent exposure to FD stimulus.

Early subclinical increase in pulmonary water content in athletes performing sustained heavy exercise at sea level: ultrasound lung comet-tail evidence

Whether prolonged strenuous exercise performed by athletes at sea level can produce interstitial pulmonary edema is under debate. Chest sonography allows to estimate extravascular lung water, creating ultrasound lung comet-tail (ULC) artifacts. The aim of the study was to determine whether pulmonary water content increases in Ironmen (n = 31) during race at sea level and its correlation with cardiopulmonary function and systemic proinflammatory and cardiac biohumoral markers. A multiple factor analysis approach was used to determine the relations between systemic modifications and ULCs by assessing correlations among variables and groups of variables showing significant pre-post changes. All athletes were asymptomatic for cough and dyspnea at rest and after the race. Immediately after the race, a score of more than five comet tail artifacts, the threshold for a significant detection, was present in 23 athletes (74%; 16.3 ± 11.2; P < 0.01 ULC after the race vs. rest) but decreased 12 h after the end of the race (13 athletes; 42%; 6.3 ± 8.0; P < 0.01 vs. soon after the race). Multiple factor analysis showed significant correlations between ULCs and cardiac-related variables and NH(2)-terminal pro-brain natriuretic peptide. Healthy athletes developed subclinical increase in pulmonary water content immediately after an Ironman race at sea level, as shown by the increased number of ULCs related to cardiac changes occurring during exercise. Hemodynamic changes are one of several potential factors contributing to the mechanisms of ULCs.

Pulmonary edema in healthy subjects in extreme conditions

There are several pieces of evidence showing occurrence of pulmonary edema (PE) in healthy subjects in extreme conditions consisting of extreme psychophysical demand in normal environment and psychophysical performances in extreme environment. A combination of different mechanisms, such as mechanical, hemodynamic, biochemical, and hypoxemic ones, may underlie PE leading to an increase in lung vascular hydrostatic pressure and lung vascular permeability and/or a downregulation of the alveolar fluid reabsorption pathways. PE can be functionally detected by closing volume measurement and lung diffusing capacity test to different gases or directly visualized by multiple imaging techniques. Among them chest ultrasonography can detect and quantify the extravascular lung water, creating “comet-tail” ultrasound artefacts (ULCs) from water-thickened pulmonary interlobular septa. In this paper the physiopathological mechanisms of PE, the functional and imaging techniques applied to detect and quantify the phenomenon, and three models of extreme conditions, that is, ironman athletes, climbers and breath-hold divers, are described.

Ultrasound lung comets induced by repeated breath-hold diving, a study in underwater fishermen

Pulmonary edema has been reported in breath-hold divers during fish-catching diving activity. The present study was designed to detect possible increases in extravascular lung water (EVLW) in underwater fishermen after a competition. Thirty healthy subjects were studied. They participated in two different 5-h fish-catching diving competitions: one organized in the winter (10 subjects) and one organized in the autumn (20 subjects). A questionnaire was used to record underwater activity and note respiratory problems. An increase in EVLW was investigated from the detection of ultrasound lung comets (ULC) by chest ultrasonography. Complementary investigations included echocardiography and pulmonary function testing. An increase in EVLW was detected in three out of 30 underwater fishermen after the competition. No signs of cardiovascular dysfunction were found in the entire population and in divers with an increase in the ULC score. Two divers with raised ULC presented respiratory disorders such as cough or shortness of breath. Impairment in spirometric parameters was recorded in these subjects. An increase in EVLW could be observed after a fish-catching diving competition in three out of 30 underwater fishermen. In two subjects, it was related to respiratory disorders and impairment in pulmonary flow.

Lung ultrasound: a new tool for the cardiologist

For many years the lung has been considered off-limits for ultrasound. However, it has been recently shown that lung ultrasound (LUS) may represent a useful tool for the evaluation of many pulmonary conditions in cardiovascular disease. The main application of LUS for the cardiologist is the assessment of B-lines. B-lines are reverberation artifacts, originating from water-thickened pulmonary interlobular septa. Multiple B-lines are present in pulmonary congestion, and may help in the detection, semiquantification and monitoring of extravascular lung water, in the differential diagnosis of dyspnea, and in the prognostic stratification of chronic heart failure and acute coronary syndromes.

B-lines quantify the lung water content: a lung ultrasound versus lung gravimetry study in acute lung injury

B-lines (also termed ultrasound lung comets) obtained with lung ultrasound detect experimental acute lung injury (ALI) very early and before hemogasanalytic changes, with a simple, noninvasive, nonionizing and real-time method. Our aim was to estimate the correlation between B-lines number and the wet/dry ratio of the lung tissue, measured by gravimetry, in an experimental model of ALI. Seventeen Na-pentobarbital anesthetized, cannulated (central vein and carotid artery) minipigs were studied: five sham-operated animals served as controls and, in 12 animals, ALI was induced by injection of oleic acid (0.1 mL/kg) via the central venous catheter. B-lines were measured by echographic scanner in four predetermined chest scanning sites in each animal. At the end of each experiment, both lungs were dissected, weighed and dried to determine wet/dry weight ratio by gravimetry. After the injection of oleic acid, B-lines number increased over time. A significant correlation was found between the wet/dry ratio and B-lines number (r = 0.91, p < 0.001). These data suggest that in an experimental pig model of ALI/ARDS, B-lines assessed by lung ultrasound provide a simple, semiquantitative, noninvasive index of lung water accumulation, strongly correlated to invasive gravimetric assessment.

Frequent subclinical high-altitude pulmonary edema detected by chest sonography as ultrasound lung comets in recreational climbers

OBJECTIVE

The ultrasound lung comets detected by chest sonography are a simple, noninvasive, semiquantitative sign of increased extravascular lung water. The aim of this study was to evaluate, by chest sonography, the incidence of interstitial pulmonary edema in recreational high-altitude climbers.

DESIGN

Observational study.

SUBJECTS

Eighteen healthy subjects (mean age 45 +/- 10 yrs, ten males) participating in a high-altitude trek in Nepal.

INTERVENTIONS

Chest and cardiac sonography at sea level and at different altitudes during ascent. Ultrasound lung comets were evaluated on anterior chest at 28 predefined scanning sites.

MEASUREMENTS AND MAIN RESULTS

At individual patient analysis, ultrasound lung comets during ascent appeared in 15 of 18 subjects (83%) at 3440 m above sea level and in 18 of 18 subjects (100%) at 4790 m above sea level in the presence of normal left and right ventricular function and pulmonary artery systolic pressure rise (sea level = 24 +/- 5 mm Hg vs. peak ascent = 42 +/- 11 mm Hg, p < .001). Ultrasound lung comets were absent at baseline (day 2, altitude 1350 m, 1.06 +/- 1.3), increased progressively during the ascent (day 14, altitude 5130 m: 16.5 +/- 8; p < .001 vs. previous steps), and decreased at descent (day 20, altitude 1355 m: 2.9 +/- 1.7; p = nonsignificant vs. baseline). An ultrasound lung comet score showed a negative correlation with O(2) saturation (R = -.7; p < .0001).

CONCLUSIONS

In recreational climbers, chest sonography revealed a high prevalence of clinically silent interstitial pulmonary edema mirrored by decreased O(2) saturation, whereas no statistically significant relationship with pulmonary artery systolic pressure was observed during ascent.

Bedside ultrasound assessment of positive end-expiratory pressure-induced lung recruitment

RATIONALE

In the critically ill patients, lung ultrasound (LUS) is increasingly being used at the bedside for assessing alveolar-interstitial syndrome, lung consolidation, pneumonia, pneumothorax, and pleural effusion. It could be an easily repeatable noninvasive tool for assessing lung recruitment.

OBJECTIVES

Our goal was to compare the pressure-volume (PV) curve method with LUS for assessing positive end-expiratory pressure (PEEP)-induced lung recruitment in patients with acute respiratory distress syndrome/acute lung injury (ARDS/ALI).

METHODS

Thirty patients with ARDS and 10 patients with ALI were prospectively studied. PV curves and LUS were performed in PEEP 0 and PEEP 15 cm H₂O₂. PEEP-induced lung recruitment was measured using the PV curve method.

MEASUREMENTS AND MAIN RESULTS

Four LUS entities were defined: consolidation; multiple, irregularly spaced B lines; multiple coalescent B lines; and normal aeration. For each of the 12 lung regions examined, PEEP-induced ultrasound changes were measured, and an ultrasound reaeration score was calculated. A highly significant correlation was found between PEEP-induced lung recruitment measured by PV curves and ultrasound reaeration score (Rho = 0.88; P < 0.0001). An ultrasound reaeration score of +8 or higher was associated with a PEEP-induced lung recruitment greater than 600 ml. An ultrasound lung reaeration score of +4 or less was associated with a PEEP-induced lung recruitment ranging from 75 to 450 ml. A statistically significant correlation was found between LUS reaeration score and PEEP-induced increase in Pa(O₂) (Rho = 0.63; P < 0.05).

CONCLUSIONS

PEEP-induced lung recruitment can be adequately estimated with bedside LUS. Because LUS cannot assess PEEP-induced lung hyperinflation, it should not be the sole method for PEEP titration.

Assessment of extravascular lung water and cardiac function in trimix SCUBA diving

An increasing number of recreational self-contained underwater breathing apparatus (SCUBA) divers use trimix of oxygen, helium, and nitrogen for dives deeper than 60 m of sea water. Although it was seldom linked to the development of pulmonary edema, whether SCUBA diving affects the extravascular lung water (EVLW) accumulation is largely unexplored.

METHODS

Seven divers performed six dives on consecutive days using compressed gas mixture of oxygen, helium, and nitrogen (trimix), with diving depths ranging from 55 to 80 m. The echocardiographic parameters (bubble grade, lung comets, mean pulmonary arterial pressure (PAP), and left ventricular function) and the blood levels of the N-terminal part of pro-brain natriuretic peptide (NT-proBNP) were assessed before and after each dive.

RESULTS

Venous gas bubbling was detected after each dive with mean probability of decompression sickness ranging from 1.77% to 3.12%. After each dive, several ultrasonographically detected lung comets rose significantly, which was paralleled by increased pulmonary artery pressure (PAP) and decreased left ventricular contractility (reduced ejection fraction at higher end-systolic and end-diastolic volumes) as well as the elevated NT-proBNP. The number of ultrasound lung comets and mean PAP did not return to baseline values after each dive.

CONCLUSIONS

This is the first report that asymptomatic SCUBA dives are associated with accumulation of EVLW with concomitant increase in PAP, diminished left ventricular contractility, and increased release of NT-proBNP, suggesting a significant cardiopulmonary strain. EVLW and PAP did not return to baseline during repetitive dives, indicating possible cumulative effect with increasing the risk for pulmonary edema.

Why, when, and how to assess pulmonary congestion in heart failure: pathophysiological, clinical, and methodological implications

Acute heart failure syndrome (AHFS) is a major public health problem. It is defined as gradual or rapid change in heart failure (HF) signs and symptoms, which often results in an unplanned hospitalization and a need for urgent therapy. Many evidence-based pharmacologic, device, and surgical treatment for HF are available or under development. Despite these new treatments and improvement in survival, hospitalizations in HF have steadily increased over the last 30 years, and the post-discharge prognosis of patients hospitalized with AHFS remains poor (Gheorghiade et al. Circulation 112:3958-3968, 2005; Fonarow et al. Rev Cardiovasc Med 4:S21-30, 2003). Most hospitalizations for AHFS are related to "congestion" rather than to low cardiac output. The definition, identification, quantification, and monitoring of congestion are therefore essential in AHFS. The purpose of this article is: (1) to characterize the different types of hemodynamic, clinical, and pulmonary congestion in AHFS; (2) to focus on the different possible ways to assess pulmonary congestion (probably the most important, and up to now the most diagnostically elusive of the three types of congestions); (3) to propose new possible ways to implement objective and user-friendly measures of pulmonary congestion in clinical and scientific decision-making in AHFS in the near future.

Ultrasonic evidence of acute interstitial lung edema after SCUBA diving is resolved within 2-3h

Recently, an increase in extravascular lung water (EVLW) accumulation with diminished left ventricular contractility within 60 min after SCUBA diving was reported. We have observed previously that diving was associated with reduced diffusing lung capacity for carbon monoxide (DLCO) and arterial oxygen pressure for up to 60-80 min postdive. Here we investigated whether increased EVLW persists 2-3h after successive deep dives in a group of seven male divers. The echocardiographic indices of pulmonary water accumulation (ultrasound lung comets (ULC)) and left ventricular function, respiratory functional measurements and arterial oxygen saturation (SaO(2)) were assessed 2-3h post diving, while venous gas bubbles (VGB) and the blood levels of NT-proBNP and proANP were analyzed 40 min after surfacing. Spirometry values, flow-volume, DLCO, SaO(2) and ULC were unchanged after each dive, except for significant increase in ULC after the second dive. Left ventricular function was reduced, while NT-proBNP and proANP levels were significantly elevated after majority of dives, suggesting a cardiac strain.