Thanks, knotical.
Cheers,
DocV
---------- Post added February 18th, 2014 at 03:52 AM ----------
"
International Journal of Cardiology
Available online 21 January 2014
In Press, Corrected Proof —
Note to users
Letter to the Editor
[h=1]Hypertension is predictive of recurrent immersion pulmonary edema in scuba divers[/h]
- Department of Hyperbaric and Diving Medicine, Sainte Anne's Military Teaching Hospital, BP600, 83800 Toulon Cedex 9, France
Received 18 November 2013, Revised 7 January 2014, Accepted 10 January 2014, Available online 21 January 2014
Choose an option to locate/access this article:
Dear editor
Pulmonary edema in scuba divers, usually termed immersion pulmonary edema (IPE), is a clinical entity increasingly described since several years but it is still underdiagnosed with a prevalence estimated at 0.2% in a previous survey
[1]. This syndrome is characterized by an accumulation of extravascular lung water resulting from increased pulmonary vascular pressure. The exact mechanisms remain elusive but abnormal capillary leak with transudative edema due to elevated hydrostatic pressure and capillary stress failure with increased permeability of the blood-gas barrier are likely involved in acting synergistically. It is generally accepted that the combination of multiple environmental stressors encountered during diving such as immersion in cold water, exercise and elevated negative inspiratory pressure are the main contributing factors to explain its development. Increasing age, female gender, emotional stress and pre-existing hypertension may pose an additional risk
[2],
[3] and
[4]. Recent case reports have outlined that IPE could be potentially fatal with a tendency to recur, particularly in older divers without evidence of underlying cardiac disease
[5] and
[6]. To date, the determinants of recurrent IPE during diving remain unknown. We, therefore, conducted a retrospective cross-sectional study to evaluate the potential predictors associated with this condition.
From March 2006 to October 2013, there were 73 consecutive scuba divers with IPE who were treated in our hyperbaric facility (Toulon, France). These 73 cases include 43 patients reported elsewhere in a recent study dealing with reversible myocardial dysfunction in the setting of IPE
[7].
The presumptive diagnosis initially based on clinical criteria (i.e. onset of dyspnea during diving, cough, frothy sputum, and bilateral rales) was promptly confirmed by chest computed tomography in the 6 h following hospital admission revealing the characteristic patchy ground-glass opacities within the lung parenchyma. The medical records of each patient were reviewed with special emphasis on the past history of IPE within the months or years preceding the current episode. Demographic data, diving parameters, pre-existing pulmonary and cardiac diseases with cardiovascular risk factors were collected and investigated as possible predictors of recurrent IPE. All the patients were followed up at 1 month with a cardiac evaluation including echocardiography, exercise testing, blood pressure measurement and determination of the blood lipid levels. For the purposes of the present study, the number of patients with hypertension or dyslipidemia was the sum of those who had been treated with appropriate medication before the acute event and those with hypertension and dyslipidemia detected during hospitalization or the follow-up study and medicated thereafter. The differences in various parameters between diver groups with and without a previous episode of IPE were examined by using univariate analyses, Fisher's exact test for categorical variables and unpaired
t-test or Mann–Whitney
U-test for numerical variables and the results were considered significant if p < 0.05. Odds ratios (ORs) with 95% confident intervals (CIs) were determined, when needed. The statistical calculations were done with GraphPad Prism, version 5.00 (GraphPad Software, San Diego, California). The study complies with the principles of Ethical Publishing in the International Journal of Cardiology.
A total of 15% of our sample (11/73) experienced a previous episode of IPE in the past. The characteristics of the patients and the analysis of data regarding the factors influencing the recurrence of IPE are given in
Table 1. Among the variables tested, the presence of hypertension appeared to be the only risk factor associated with a repeated episode (OR 5.5, 95% CI 1.4 to 21.5, p = 0.015). It is interesting to note that 3 patients in the recurrence group and 4 patients in the group of unique IPE not known to have hypertension before the admission were found to have this disease throughout their hospitalization or at the follow-up examination.
Table 1. Demographic, medical history and details of incident dives between injured divers with and without a previous episode of immersion pulmonary edema (IPE).
| Variables | Recurrence
(n = 11) | Non-recurrence
(n = 62) | p-Value | OR
(95% CI) |
|---|
| Male/female | 7/4 | 40/22 | 1 | – |
| Mean age (years) | 51 ± 14 | 47 ± 12 | 0.29 | – |
| Median BMI (kg/m2) | 24.4 [22.1–30] | 25 [22.8–28.1] | 0.80 | – |
| Cigarette smoker | 4 (36%) | 2 (3%) | 0.22 | – |
| Hypertension | 6 (54%) | 11 (18%) | 0.015 | 5.5 (1.4–21.5) |
| Diabetes mellitus | 0 | 3 (5%) | 1 | |
| Hyperlipidemia ⁎⁎⁎ | 2 (18%) | 8 (13%) | 0.64 | – |
| Pre-existing pulmonary disease ⁎ | 1 (9%) | 3 (5%) | 0.48 | – |
| Pre-existing heart disease ⁎⁎ | 1 (9%) | 1 (2%) | 0.28 | – |
| Mean depth (msw) | 32 ± 11 | 32 ± 13 | 0.9 | – |
| Mean total dive time (min) | 29 ± 10 | 28 ± 14 | 0.85 | – |
| Violation of decompression guidelines | 3 (27%) | 21 (34%) | 1 | – |
| Breathing gas | | | 0.42 | – |
| – Air | 52 | 8 | | – |
| – Nitrox | 10 | 3 | | – |
| Repetitive dive (2/24 h) | 8 (72%) | 38 (61%) | 0.73 | – |
| Mean water temperature (°C) | 16.4 ± 3 | 15.7 ± 3 | 0.53 | – |
| Exertion in diving/after surfacing | 3 (27%) | 17 (27%) | 1 | – |
| Emotional stress | 2 (18%) | 24 (39%) | 0.3 | – |
| Diving certification (PADI) | | | 0.06 | – |
| – Low and average levels | 6 | 51 | | |
| – High level | 5 | 11 | | |
Data are presented as mean ± SD or median [IQR] for continuous variables while categorical variables are expressed in number (%).
Low and average levels for diving certifications consisted of divers with a certificate of open-water, advanced open-water, rescue diver or equivalent, while high level comprised divemasters and diving instructors.
⁎Indicates obstructive sleep apnea (n = 2) or asthma induced by exertion (n = 2).
⁎⁎Indicates coronary artery disease previously treated by revascularization.
⁎⁎⁎Determined by serum LDL cholesterol levels > 3.5 mmol/L or triglycerides > 1.8 mmol/L.
Full-size tableTable options
Our results are unique but are in line with previous findings indicating that hypertension is frequently observed in scuba divers experiencing IPE
[3] and
[5]. It has been suggested that an increased forearm vascular resistance to cold pressure test may be a pre-existing condition to the development of this injury, predating in addition the rise in blood pressure with time
[8]. Thus, IPE may share a common neurohumoral mechanism with pulmonary edema induced by psychological or physical stress
[4] and central nervous system insult
[9], which are believed to be mediated by a significant release of endogenous catecholamines. This phenomenon would lead to myocardial toxicity
[7] or an enhanced sympathetic discharge that affects directly the systemic circulation and the pulmonary vascular bed with subsequent peripheral vasoconstriction, pulmonary venoconstriction and pulmonary endothelial disruption
[9].
We advise physicians to exercise caution in divers with occult hypertension. Affected patients (even those receiving medical therapy) should forego scuba diving or reduce the additional environmental stressors associated with this activity (i.e. exertion, cold exposure)."
