Swimming-Induced Pulmonary Edema
2022; Elsevier BV; Volume: 162; Issue: 2 Linguagem: Inglês
10.1016/j.chest.2022.02.054
ISSN1931-3543
AutoresClaudia Seiler, Linda Kristiansson, Cecilia Klingberg, Josefin Sundh, Annika Eriksson, Daniel Lundeqvist, Kristofer F. Nilsson, Maria Hårdstedt,
Tópico(s)Cardiovascular and Diving-Related Complications
ResumoBackgroundSwimming-induced pulmonary edema (SIPE) occasionally occurs during swimming in cold open water. Although optimal treatment for SIPE is unknown, non-invasive positive pressure ventilation (NPPV) is an option for prehospital treatment.Research QuestionIs NPPV a feasible and safe prehospital treatment for SIPE, and which outcome measures reflect recovery after treatment?Study Design and MethodsA prospective observational study was conducted at Vansbrosimningen, Sweden's largest open water swimming event, from 2017 through 2019. Swimmers with a diagnosis of SIPE and with peripheral oxygen saturation (Spo2) of ≤ 95%, persistent respiratory symptoms, or both were eligible for the study. NPPV was administered on site as CPAP by facial mask or as positive expiratory pressure (PEP) by a PEP device. Discharge criteria were Spo2 of > 95% and clinical recovery. Four outcome measures were evaluated: Spo2, crackles on pulmonary auscultation, pulmonary edema on lung ultrasound (LUS), and patient-reported respiratory symptoms.ResultsOf 119 treated individuals, 94 received CPAP, 24 received treatment with a PEP device, and one required tracheal intubation. In total, 108 individuals (91%) were discharged after NPPV for a median of 10 to 20 min and 11 individuals (9%) required hospital transfer. NPPV resulted in increased Spo2 from a median of 91% to 97% (P < .0001) together with improvement of six patient-reported respiratory symptoms (median numerical rating scales, 1-7 to 0-1; P < .0001). No significant decrease in auscultation of crackles (93% vs 87%; P = .508) or pulmonary edema on LUS (100% vs 97%; P = .500) was seen during NPPV treatment.InterpretationNPPV administered as CPAP or via a PEP device proved feasible and safe as prehospital treatment for SIPE with a vast majority of patients discharged on site. Spo2 and patient-reported respiratory symptoms reflected recovery after treatment, whereas pulmonary auscultation or LUS findings did not. Swimming-induced pulmonary edema (SIPE) occasionally occurs during swimming in cold open water. Although optimal treatment for SIPE is unknown, non-invasive positive pressure ventilation (NPPV) is an option for prehospital treatment. Is NPPV a feasible and safe prehospital treatment for SIPE, and which outcome measures reflect recovery after treatment? A prospective observational study was conducted at Vansbrosimningen, Sweden's largest open water swimming event, from 2017 through 2019. Swimmers with a diagnosis of SIPE and with peripheral oxygen saturation (Spo2) of ≤ 95%, persistent respiratory symptoms, or both were eligible for the study. NPPV was administered on site as CPAP by facial mask or as positive expiratory pressure (PEP) by a PEP device. Discharge criteria were Spo2 of > 95% and clinical recovery. Four outcome measures were evaluated: Spo2, crackles on pulmonary auscultation, pulmonary edema on lung ultrasound (LUS), and patient-reported respiratory symptoms. Of 119 treated individuals, 94 received CPAP, 24 received treatment with a PEP device, and one required tracheal intubation. In total, 108 individuals (91%) were discharged after NPPV for a median of 10 to 20 min and 11 individuals (9%) required hospital transfer. NPPV resulted in increased Spo2 from a median of 91% to 97% (P < .0001) together with improvement of six patient-reported respiratory symptoms (median numerical rating scales, 1-7 to 0-1; P < .0001). No significant decrease in auscultation of crackles (93% vs 87%; P = .508) or pulmonary edema on LUS (100% vs 97%; P = .500) was seen during NPPV treatment. NPPV administered as CPAP or via a PEP device proved feasible and safe as prehospital treatment for SIPE with a vast majority of patients discharged on site. Spo2 and patient-reported respiratory symptoms reflected recovery after treatment, whereas pulmonary auscultation or LUS findings did not. Take-home PointsStudy Question: Is noninvasive positive pressure ventilation (NPPV) a feasible and safe prehospital treatment for swimming-induced pulmonary edema?Results: Most patients (91%) could be discharged safely after a median of 10 to 20 min of NPPV treatment on site.Interpretation: NPPV, administered as CPAP ventilation or by a positive expiratory pressure device, proved feasible and safe as prehospital treatment for swimming-induced pulmonary edema.FOR EDITORIAL COMMENT, SEE PAGE 277Swimming-induced pulmonary edema (SIPE) occurs in predominantly healthy individuals during swimming in cold open water.1Grünig H. Nikolaidis P.T. Moon R.E. Knechtle B. Diagnosis of swimming induced pulmonary edema: a review.Front Physiol. 2017; 8: 652Crossref PubMed Scopus (29) Google Scholar Symptoms consist of dyspnea, cough, or hemoptysis together with hypoxemia and findings of crackles on pulmonary auscultation.1Grünig H. Nikolaidis P.T. Moon R.E. Knechtle B. Diagnosis of swimming induced pulmonary edema: a review.Front Physiol. 2017; 8: 652Crossref PubMed Scopus (29) Google Scholar,2Hårdstedt M. Seiler C. Kristiansson L. Lundeqvist D. Klingberg C. Braman Eriksson A. Swimming-induced pulmonary edema: diagnostic criteria validated by lung ultrasound.Chest. 2020; 158: 1586-1595Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar Pulmonary edema in patients with SIPE has been visualized by radiograph or CT scan, but also been confirmed in prehospital settings by point-of-care lung ultrasound (LUS).1Grünig H. Nikolaidis P.T. Moon R.E. Knechtle B. Diagnosis of swimming induced pulmonary edema: a review.Front Physiol. 2017; 8: 652Crossref PubMed Scopus (29) Google Scholar, 2Hårdstedt M. Seiler C. Kristiansson L. Lundeqvist D. Klingberg C. Braman Eriksson A. Swimming-induced pulmonary edema: diagnostic criteria validated by lung ultrasound.Chest. 2020; 158: 1586-1595Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar, 3Alonso J.V. Chowdhury M. Borakati R. Gankande U. Swimming-induced pulmonary oedema an uncommon condition diagnosed with POCUS ultrasound.Am J Emerg Med. 2017; 35: 1986.e1983-1986.e1984Abstract Full Text Full Text PDF Scopus (6) Google Scholar Although the pathophysiologic features are not understood fully, SIPE is considered a hydrostatic edema with high pulmonary capillary transmural pressure. The proposed mechanism is a combination of central pooling of blood and increased left ventricular afterload resulting from immersion in cold water, increased pulmonary capillary pressure during physical exercise, and negative intrathoracic pressures during head-out water immersion in susceptible individuals.4Castagna O. Regnard J. Gempp E. et al.The key roles of negative pressure breathing and exercise in the development of interstitial pulmonary edema in professional male SCUBA divers.Sports Med Open. 2018; 4: 1Crossref PubMed Scopus (13) Google Scholar, 5Shearer D. Mahon R. Brain natriuretic peptide levels in six basic underwater demolitions/SEAL recruits presenting with swimming induced pulmonary edema (SIPE).J Spec Oper Med. 2009; 9: 44-50Crossref PubMed Google Scholar, 6Wester T.E. Cherry A.D. Pollock N.W. et al.Effects of head and body cooling on hemodynamics during immersed prone exercise at 1 ATA.J Appl Physiol. 2009; 106: 691-700Crossref PubMed Scopus (36) Google Scholar, 7Moon R.E. Martina S.D. Peacher D.F. et al.Swimming-induced pulmonary edema: pathophysiology and risk reduction with sildenafil.Circulation. 2016; 133: 988-996Crossref PubMed Scopus (49) Google Scholar, 8Pendergast D.R. Moon R.E. Krasney J.J. Held H.E. Zamparo P. Human physiology in an aquatic environment.Compr Physiol. 2015; 5: 1705-1750Crossref PubMed Scopus (108) Google Scholar Consequently, SIPE usually resolves spontaneously within 24 to 48 h after removal of the patient from water and rest, but occasionally may be life-threatening.1Grünig H. Nikolaidis P.T. Moon R.E. Knechtle B. Diagnosis of swimming induced pulmonary edema: a review.Front Physiol. 2017; 8: 652Crossref PubMed Scopus (29) Google Scholar,9Cochard G. Henckes A. Deslandes S. et al.Swimming-induced immersion pulmonary edema while snorkeling can be rapidly life-threatening: case reports.Undersea Hyperb Med. 2013; 40: 411-416PubMed Google Scholar,10Vinkel J. Bak P. Juel Thiis Knudsen P. Hyldegaard O. Forensic case reports presenting immersion pulmonary edema as a differential diagnosis in fatal diving accidents.J Forensic Sci. 2018; 63: 299-304Crossref PubMed Scopus (6) Google Scholar The optimal strategy for treatment of SIPE is unknown. Based on pathophysiologic characteristics, noninvasive positive pressure ventilation (NPPV) could be a favorable treatment.5Shearer D. Mahon R. Brain natriuretic peptide levels in six basic underwater demolitions/SEAL recruits presenting with swimming induced pulmonary edema (SIPE).J Spec Oper Med. 2009; 9: 44-50Crossref PubMed Google Scholar,11Berbenetz N. Wang Y. Brown J. et al.Non-invasive positive pressure ventilation (CPAP or bilevel NPPV) for cardiogenic pulmonary oedema.Cochrane Database Syst Rev. 2019; 4: CD005351PubMed Google Scholar Interestingly, other than a pilot study published by our research group in 2016, we could find only seven cases of patients treated with NPPV for SIPE in the literature.9Cochard G. Henckes A. Deslandes S. et al.Swimming-induced immersion pulmonary edema while snorkeling can be rapidly life-threatening: case reports.Undersea Hyperb Med. 2013; 40: 411-416PubMed Google Scholar,12Beinart R. Matetzky S. Arad T. Hod H. Cold water-induced pulmonary edema.Am J Med. 2007; 120: e3Abstract Full Text Full Text PDF PubMed Scopus (10) Google Scholar, 13Bloch A.M. Weiss E.M. Ingold U. Gigathlon extreme experience—the limits of physical endurance.Swiss Med Forum. 2009; 9: 171-173Google Scholar, 14Stefanko G. Lancashire B. Coombes J.S. Fassett R.G. Pulmonary oedema and hyponatraemia after an ironman triathlon.BMJ Case Rep. 2009; (2009:bcr04.2009.1764)Crossref PubMed Scopus (14) Google Scholar, 15Braman Eriksson A. Annsberg M. Hårdstedt M. Swimming-induced pulmonary edema in Swedish conditions has been insufficiently studied [in Swedish]..Lakartidningen. 2017; 114: 1130-1132Google Scholar, 16Volk C. Spiro J. Boswell G. et al.Incidence and impact of swimming-induced pulmonary edema on Navy SEAL candidates.Chest. 2021; 159: 1934-1941Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar, 17Paz P. Makram J. Mallah H. Mantilla B. Ball S. Nugent K. Swimming-induced pulmonary edema.Proc (Bayl Univ Med Cent). 2020; 33: 409-412PubMed Google ScholarAn important aspect of prehospital care for SIPE is the growing popularity of open water swimming competitions that challenges the surrounding health care organizations.15Braman Eriksson A. Annsberg M. Hårdstedt M. Swimming-induced pulmonary edema in Swedish conditions has been insufficiently studied [in Swedish]..Lakartidningen. 2017; 114: 1130-1132Google Scholar,18Smith R. Ormerod J.O.M. Sabharwal N. Kipps C. Swimming-induced pulmonary edema: current perspectives.Open Access J Sports Med. 2018; 9: 131-137Crossref PubMed Google Scholar Vansbrosimningen is the largest open water swimming event in Sweden and attracts approximately 11,000 participants yearly. A considerable number of patients with SIPE seeking medical care during the swimming event each year, together with a 78-km distance to the nearest hospital, puts pressure on the on-site prehospital medical service.19Hardstedt M. Kristiansson L. Seiler C. Braman Eriksson A. Sundh J. Incidence of swimming-induced pulmonary edema: a cohort study based on 47,600 open-water swimming distances.Chest. 2021; 160: 1789-1798Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar With the purpose of providing efficient treatment on site and possibly saving ambulance and hospital resources, prehospital CPAP for treatment of SIPE was implemented during Vansbrosimningen in 2013.15Braman Eriksson A. Annsberg M. Hårdstedt M. Swimming-induced pulmonary edema in Swedish conditions has been insufficiently studied [in Swedish]..Lakartidningen. 2017; 114: 1130-1132Google Scholar In 2019, treatment with a positive expiratory pressure (PEP) device was added for patients with less severe SIPE.The aim of this study was to evaluate the feasibility and outcome of prehospital treatment of SIPE with NPPV administered as CPAP by facial mask or by PEP device. Furthermore, we assessed which of the following outcome measures that could reflect successful treatment: peripheral oxygen saturation (Spo2), crackles on pulmonary auscultation, findings of pulmonary edema on LUS, and patient-reported respiratory symptoms. In a subgroup with less severe SIPE based on Spo2, treatment with CPAP was compared with treatment with a PEP device.Study Design and MethodsStudy Design and PopulationA prospective observational treatment study was conducted during the open water swimming event Vansbrosimningen in 2017, 2018, and 2019. This yearly event takes place during a 3-day weekend in July in the municipality of Vansbro, Sweden. Approximately 11,000 swimmers complete distances of 1,000 m, 1,500 m, or 3,000 m in cold (16-20 °C) freshwater rivers. The participants represent a broad range of all ages (≥ 10 years), both sexes, competitive swimmers, as well as recreational swimmers. The on-site health care organization includes first aid teams positioned along the riverside and a mobile medical unit (MMU) at the finish area. The MMU consists of a warmed-up military tent and a heated container equipped with four oxygen-driven CPAP stations. Swimmers seeking or being referred to the MMU because of acute onset of cough, dyspnea, or both during or directly after swimming were evaluated for SIPE. Patients arrived within about 10 to 60 min from exiting the water. No treatment was provided before arrival the MMU except for single patients who received oxygen or CPAP during a short ambulance ride to the MMU or used their own asthma medication at the riverside.All swimmers (≥ 18 years of age) with a diagnosis of SIPE and with indication for acute treatment were eligible for the study. SIPE diagnosis was based on previously published criteria.2Hårdstedt M. Seiler C. Kristiansson L. Lundeqvist D. Klingberg C. Braman Eriksson A. Swimming-induced pulmonary edema: diagnostic criteria validated by lung ultrasound.Chest. 2020; 158: 1586-1595Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar,19Hardstedt M. Kristiansson L. Seiler C. Braman Eriksson A. Sundh J. Incidence of swimming-induced pulmonary edema: a cohort study based on 47,600 open-water swimming distances.Chest. 2021; 160: 1789-1798Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar LUS findings of pulmonary edema confirmed SIPE diagnosis in 2018 and 2019. In case of missing LUS examination during these years (2018, n = 1; 2019, n = 3) and for all individuals in 2017 (n = 59), clinical diagnostic criteria were used based on Spo2 of ≤ 95%, crackles on pulmonary auscultation, or both.2Hårdstedt M. Seiler C. Kristiansson L. Lundeqvist D. Klingberg C. Braman Eriksson A. Swimming-induced pulmonary edema: diagnostic criteria validated by lung ultrasound.Chest. 2020; 158: 1586-1595Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar,19Hardstedt M. Kristiansson L. Seiler C. Braman Eriksson A. Sundh J. Incidence of swimming-induced pulmonary edema: a cohort study based on 47,600 open-water swimming distances.Chest. 2021; 160: 1789-1798Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar The indication for acute treatment of SIPE with NPPV (CPAP or PEP device) was Spo2 remaining at ≤ 95% after initial assessment, persistent respiratory symptoms, or both. Patients who did not receive NPPV treatment on site because of spontaneous recovery during initial assessment, because they recieved β-agonist inhalation only, or because they declined treatment as well as patients who were transferred to hospital because of chest pain were excluded from analysis.Ethical approval was received from the regional ethical review board in Uppsala, Sweden (Identifiers: 2017/216 and 2017/216/1-2). All individuals gave written informed consent for participation.Data Collection and Outcome MeasuresOn arrival at the MMU, wetsuits were removed and patients were warmed with blankets. Medical history, clinical parameters, and symptoms were documented. Clinical symptoms were noted by the physician as yes or no for dyspnea, cough, sputum, or hemoptysis. Treatment with CPAP or PEP device was applied as described separately. To evaluate which measures could indicate successful treatment outcome, data for the following four measures were collected: Spo2, crackles on pulmonary auscultation, findings of pulmonary edema on LUS, and patient-reported respiratory symptoms. The latter three outcome measures were added over the study period (Table 1). Spo2 was measured with a pulse oximeter (Nellcor Oximax N-65; Covidien). Pulmonary auscultation findings were reported by the attending physician as normal breathing sounds, crackles, and other findings. LUS examination was performed by two experienced consultant anesthesiologists as described previously (BK Medical Flex Focus 500 with a curved probe [BK Medical type 8823] of 2-6 MHz; BK Medical AB).2Hårdstedt M. Seiler C. Kristiansson L. Lundeqvist D. Klingberg C. Braman Eriksson A. Swimming-induced pulmonary edema: diagnostic criteria validated by lung ultrasound.Chest. 2020; 158: 1586-1595Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar,20Volpicelli G. Elbarbary M. Blaivas M. et al.International evidence-based recommendations for point-of-care lung ultrasound.Intensive Care Med. 2012; 38: 577-591Crossref PubMed Scopus (1667) Google Scholar Eight chest regions were scanned for B-lines. For each lung region, a clip of 2 s was recorded, and later reviewed in a masked fashion by the other physician. Bilateral or unilateral presence of two or more positive regions (≥ 3 B-lines) was defined as pulmonary edema.2Hårdstedt M. Seiler C. Kristiansson L. Lundeqvist D. Klingberg C. Braman Eriksson A. Swimming-induced pulmonary edema: diagnostic criteria validated by lung ultrasound.Chest. 2020; 158: 1586-1595Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar,20Volpicelli G. Elbarbary M. Blaivas M. et al.International evidence-based recommendations for point-of-care lung ultrasound.Intensive Care Med. 2012; 38: 577-591Crossref PubMed Scopus (1667) Google Scholar Six different patient-reported respiratory symptoms were assessed by a numerical rating scale (0-10) (e-Fig 1): two symptoms typically occurring in patients with SIPE (cough and mucus in the airways) as well as four different qualities of dyspnea, modified from the multidimensional dyspnea profile instrument (air hunger, physical breathing effort, tightness of the chest, and anxiety).21Banzett R.B. O'Donnell C.R. Guilfoyle T.E. et al.Multidimensional dyspnea profile: an instrument for clinical and laboratory research.Eur Respir J. 2015; 45: 1681-1691Crossref PubMed Scopus (155) Google Scholar,22Ekström M. Sundh J. Swedish translation and linguistic validation of the multidimensional dyspnoea profile.Eur Clin Respir J. 2016; 3: 32665Crossref PubMed Google ScholarTable 1Treatment With CPAP or PEP Device and Outcome Measures Over the 3 Years of the Study2017 (n = 37)2018 (n = 37)2019 (n = 45)Treatment properties Device (oxygen saturation before treatment)CPAP (≤ 95%)CPAP (≤ 95%)CPAP (≤ 91%)PEP device (≥ 92%) Treatment cycle: time with device plus rest, min10 + 1010 + 1020 + 10 10-20 min of treatment: No. of treatment cycles1-21-21 30-40 min of treatment: No. of treatment cycles3-43-42Outcome measuresSpo2Spo2Spo2. . .Pulmonary auscultationPulmonary auscultation. . .LUSLUS. . .. . .Patient-reported respiratory symptomsLUS = lung ultrasound; PEP = positive expiratory pressure; Spo2 = peripheral oxygen saturation. Open table in a new tab Prehospital Treatment With CPAP or PEP DeviceOver the years, treatment with CPAP or a PEP device was modified slightly to follow updated guidelines for oxygen treatment and to improve treatment flow on site (Table 1).23Siemieniuk R.A.C. Chu D.K. Kim L.H. et al.Oxygen therapy for acutely ill medical patients: a clinical practice guideline.BMJ. 2018; 363: k4169Crossref PubMed Scopus (134) Google Scholar Briefly, NPPV was provided by either oxygen-driven CPAP or by a PEP device breathing air (Fig 1). In 2017 and 2018, oxygen-driven CPAP by facial mask was administered to all individuals with indication for NPPV treatment. Here, oxygen flow was set to 10 to 12 L/min to achieve continuous positive pressure of approximately 7 to 8 cm H2O, resulting in an inspired oxygen fraction of 40% to 60% (Flow-Safe II; Infiniti Medical). In 2019, patients with saturation of ≤ 91% received oxygen-driven CPAP and patients with saturation of ≥ 92% received treatment with a PEP device. This year, a facial CPAP mask delivering a fixed pressure of 7.5 cm H2O by oxygen flow of 10 L/min and stable inspired fraction of oxygen of 30% was used to decrease variation in treatment parameters (GO-PAP; Pulmodyne). The PEP device generated a positive pressure of approximately 7 to 8 cm H2O on expiration when patients were instructed to breathe in through the nose and breathe out through the device (Mini-PEP 3.0 mm; Dolema). For all 3 years, adverse events during treatment were noted.Duration of treatment was set to cycles of 10 min in 2017 and 2018 and was modified to 20 min in 2019. That is, treatment durations of 10 to 20 min corresponded to one or two cycles and treatment of 30 to 40 min corresponded to two to four cycles in the different years (Table 1). Each cycle was followed by a 10-min pause, breathing air, to wash out oxygen before Spo2 was measured and further actions were taken. Based on the following clinical evaluation, a new treatment cycle begun or the patient was discharged or transferred to hospital. Discharge criteria consisted of improved Spo2, aiming for a stable value of > 95%, together with alleviated subjective respiratory symptoms.24Smith G.B. Prytherch D.R. Watson D. et al.S(p)O(2) values in acute medical admissions breathing air—implications for the British Thoracic Society guideline for emergency oxygen use in adult patients?.Resuscitation. 2012; 83: 1201-1205Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar Ambulance transfer to hospital was initiated if discharge criteria were not met after a total treatment duration of 30 to 40 min. A follow-up phone call was made to all patients within 10 days after discharge to register requirement for acute medical care within 24 h after treatment at the MMU.Statistical AnalysisStatistical analysis was performed for all individuals treated with CPAP or PEP device and for a subgroup with Spo2 of ≥ 92% before treatment. Treatment data were divided based on duration of treatment into three groups: 10 to 20 min, 30 to 40 min, or hospital transfer. An unweighted Kruskal-Wallis test based on pseudoranks was used for comparison of Spo2 and respiratory rate in individuals with different treatment duration.25Brunner E. Konietschke F. Pauly M. Puri M.L. Rank-based procedures in factorial designs: hypotheses about non-parametric treatment effects.J R Stat Soc Series B Stat Methodol. 2017; 79: 1463-1485Crossref Scopus (54) Google Scholar To identify outcome measures that indicated successful treatment on site, those parameters were evaluated separately for individuals discharged from the MMU or transferred to hospital. The Wilcoxon signed-rank test and McNemar test were used for comparison of continuous or nominal data before vs after treatment. The Spearman correlation was used to evaluate the association between Spo2 before or after treatment with patient-reported respiratory symptoms. Interrater reliability for LUS was presented by percentage and Cohen's κ value. Within the subgroup, the Mann-Whitney U test and Fisher exact test were used for comparison of continuous or nominal data, respectively. The level of significance of P < .05 was adjusted family-wise using the Bonferroni correction for multiple comparisons. For statistical analysis we used IBM SPSS Statistics for Windows version 26.0 (IBM Corp.), the package rankFD version 0.1.0,26Brenner E. Bathke A.C. Konietschke Rank and Pseudo-Rank Procedures forIndependent Observations in Factorial Designs: Using R and SAS. Springer, Cham2018https://link.springer.com/book/10.1007/978-3-030-02914-2Crossref Google Scholar and R software version 4.1.2 (R Foundation for Statistical Computing). GraphPad Prism version 8.4.3 software (GraphPad Software) was used for graphic presentation.ResultsAltogether, 32,908 swimmers (≥ 18 years of age) participated in the swimming event from 2017 through 2019.19Hardstedt M. Kristiansson L. Seiler C. Braman Eriksson A. Sundh J. Incidence of swimming-induced pulmonary edema: a cohort study based on 47,600 open-water swimming distances.Chest. 2021; 160: 1789-1798Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar Of a total of 165 individuals with a diagnosis of SIPE, 119 received treatment with CPAP or a PEP device at the MMU (Fig 2). The mean age of treated swimmers was 48 years, a majority were women, and the median Spo2 at admission was 91% (Table 2).Figure 2Flow chart showing study progression. PEP = positive expiratory pressure; SIPE = swimming-induced pulmonary edema; Spo2 = peripheral oxygen saturation.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Table 2Background Characteristics and Clinical Findings Before TreatmentVariableAll Individuals (N = 119)Subgroup With Spo2 of ≥ 92%CPAP (n = 24)PEP Device (n = 24)Age, y48 ± 1046 ± 1148 ± 10Sex Male10 (8)1 (4)0 Female109 (92)23 (96)24 (100)Medical history Hypertension18 (15)6 (25)1 (4) Heart disease5 (4)01 (4) Asthma19 (16)5 (21)3 (13) Smoker1 (1)00Clinical findings Spo2, %91 (88-94)94 (92-95)94 (93-95) Crackles on lung auscultation111 (93)24 (100)21 (87) Pulmonary edema on LUSaData from 2018 and 2019. All individuals: n = 82; subgroup: CPAP, n = 12; PEP device, n = 24.80 (100)bMissing values: n = 2.12 (100)24 (100) Clinical symptomsDyspnea or cough only79 (66)17 (71)18 (75)Sputum or hemoptysis40 (34)7 (29)6 (25) Patient-reported respiratory symptoms, NRScData from 2019. All individuals: n = 45; subgroup: CPAP, n = 0; PEP device, n = 24.Cough4 (2-7)—4 (2-6)Mucus in the airways3 (1-7)—2 (1-5)Air hunger4 (2-7)—4 (2-7)Physical breathing effort7 (3-8)—7 (3-8)Tightness of the chest5 (2-7)—5 (1-7)Anxiety1 (0-4)—1 (0-4)Data are presented as No. (%), mean ± SD, or median (interquartile range). IQR = interquartile range; LUS = lung ultrasound; NRS = numerical rating scale (0-10); PEP = positive expiratory pressure; Spo2 = peripheral oxygen saturation; — = no data available.a Data from 2018 and 2019. All individuals: n = 82; subgroup: CPAP, n = 12; PEP device, n = 24.b Missing values: n = 2.c Data from 2019. All individuals: n = 45; subgroup: CPAP, n = 0; PEP device, n = 24. Open table in a new tab Clinical Course of Prehospital Treatment With CPAP or PEP DeviceOf 119 included individuals, 94 were treated with CPAP, 24 were treated with a PEP device, and one required tracheal intubation on site. In total, 108 patients (91%) improved with treatment on site and could be discharged from the MMU. For those, durations of treatment with CPAP or PEP device were 10 min (n = 30), 20 min (n = 52), 30 min (n = 12), and 40 min (n = 13), with missing treatment time for one patient. Transfer to hospital was required for 11 patients (9%), of whom three were treated at the ICU. In addition, one individual discharged from the MMU sought emergency care for respiratory symptoms later the same day. At the ED, this patient showed an Spo2 of 100% and normal findings on chest radiography. Longer duration of treatment with CPAP or PEP device was associated with lower Spo2 at admission (Fig 3A). Requirement of hospital care was associated with lower Spo2 or higher respiratory rate at admission (Fig 3A, 3B), while other clinical findings or background data were similar (data not shown). Three individuals reported adverse events during treatment with CPAP as a feeling of panic (n = 2) and blocked ears (n = 1). No adverse events were reported for treatment with the PEP device. In addition to treatment with CPAP or PEP device, 10 patients (of whom two had previously diagnosed asthma) received inhalation of a β-agonist at the MMU. Furosemide was administered by paramedics to two patients during transfer to hospital. Detailed courses of Spo2 during treatment with CPAP or PEP device are presented in e-Table 1.Figure 3A, B, Box and whisker plots showing treatment duration and corresponding peripheral oxygen saturation (A) and respiratory rate at admission (B) for all individuals. Comparison between groups by the unweighted Kruskal-Wallis test based on pseudoranks (P < .0001). Post hoc pairwise comparisons are as follows: P < .0001 (10-20 min vs 30-40 min) and P = .0005 (30-40 min vs hospital care) (A) and P = .833 (10-20 min vs 30-40 min) and P = .028 (30-40 min vs hospital care) (B). The level of significance was set to 0.006 after Bonferroni correction for multiple comparisons. Missing values: n = 4 (A) and n = 8 (B).View Large Image Figure ViewerDownload Hi-res image Download (PPT)Evaluation of Outcome MeasuresIn patients discharged from the MMU, median Spo2 improved from 91% to 95% (P < .0001) after the first treatment circle and to 97% after completing treatment with CPAP or PEP device (e-Table 1, Fig 4A). No significant di
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