To Örebro University

BACKGROUND: Swimming-induced pulmonary edema (SIPE) has been reported to subside within 24-48 hours, but comprehensive follow-up studies on symptom duration and long-term effects are missing.

RESEARCH QUESTION: What is the symptom duration, recurrence, and long-term effects of SIPE?

STUDY DESIGN AND METHODS: A follow-up study was conducted based on 165 cases of SIPE from Sweden's largest open water swimming event with 26,125 individuals participating during 2017-2019. Data on patient characteristics, clinical findings and symptoms were collected upon admission. Telephone interviews at 10 days and 30 months were performed to explore symptom duration, recurrence of SIPE symptoms, need of medical evaluation and long-term effects of self-assessed general health and physical activity level.

RESULTS: Follow-up at 10 days was performed for 132 cases and at 30 months for 152 cases. Most of the cases were women and mean age was 48 years. At the 10-day follow-up, symptom duration >2 days after the swimming race were reported by 38%. The most common symptoms were dyspnea and cough. In patients followed for 30 months, recurrence of respiratory symptoms during open water swimming was reported by 28%. In multivariable logistic regression, asthma was independently associated with both symptom duration >2 days and recurrence of SIPE symptoms (p =0.045 and p =0.022 respectively). Most participants reported equal or improved general health (93%) and physical activity level (85%) after experiencing SIPE, but 58% had not swum in open water since the event.

INTERPRETATION: The present large cohort study challenges the established hallmark of SIPE symptom duration of <48 hours, while SIPE recurrence was in the previously reported range. At 30 months, most patients reported unchanged self-assessed general health and physical activity level. These findings add to our understanding of the course of SIPE and can provide evidence-based information to swimmers and health care professionals.

BACKGROUND: Swimming-induced pulmonary edema (SIPE) occasionally occurs during swimming in cold open water. While optimal treatment for SIPE is unknown, non-invasive positive pressure ventilation (NPPV) is an option for prehospital treatment.

RESEARCH QUESTION: Is NPPV a feasible and safe prehospital treatment for SIPE, and which outcome measures reflect recovery after treatment?

STUDY DESIGN AND METHODS: A prospective observational study was conducted at Vansbrosimningen, Sweden's largest open water swimming event, in 2017-2019. Swimmers diagnosed with SIPE and with peripheral oxygen saturation (SpO₂) ≤95% and/or persistent respiratory symptoms were eligible for the study. NPPV was administered on-site as continuous positive airway pressure (CPAP) by facial mask or as positive expiratory pressure device (PEP-device). Discharge criteria were SpO₂ >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.

RESULTS: Of 119 treated individuals, 94 received CPAP, 24 PEP-device and one required tracheal intubation. In total, 108 (91%) individuals were discharged after NPPV for median 10-20 minutes, 11 (9%) required hospital transfer. NPPV resulted in increased SpO₂ from median 91% to 97% (p<0.0001) together with improvement of six patient-reported respiratory symptoms (median numerical rating scales 1-7 to 0-1; p<0.0001). No significant decrease in auscultation of crackles (93% vs 87%, p=0.508) or pulmonary edema on LUS (100% vs 97%, p=0.500) was seen during NPPV-treatment.

INTERPRETATION: NPPV administered as CPAP or 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 did not.

BACKGROUND: Despite increasing awareness of swimming-induced pulmonary edema (SIPE), there is a lack of large population-based studies and the incidence is unknown.

RESEARCH QUESTION: What is the incidence of SIPE in a mixed group of competitive and recreational swimmers during a large open water swimming event?

METHODS: In four consecutive years (2016-2019), a prospective cohort study was conducted during Sweden's largest open water swimming event - Vansbrosimningen. All swimmers seeking medical care with acute respiratory symptoms were eligible for the study. SIPE diagnosis was based on clinical findings in 2016-2017 and pulmonary edema assessed by lung ultrasound in 2018-2019. Data on patient characteristics, clinical findings and information about the race were collected.

RESULTS: Based on 47 573 consecutive swimming distances, 322 cases of acute respiratory symptoms (0.68%; C.I. 0.61%-0.75%) were presented at the mobile medical unit. Of these, 211 (0.44%; C.I. 0.39%-0.51%) were diagnosed with SIPE. The annual incidence of SIPE was 0.34%, 0.47%, 0.41% and 0.57%, respectively in 2016-2019. A majority of patients diagnosed with SIPE were women (90%) despite about equal percentage of men and women participating (47% men; 53% women). The incidence of SIPE was overall 0.75% in women and 0.09% in men. The incidence increased with age, from 0.08% in the youngest age group (18-30 years) to 1.1% in the oldest age group (≥61 years). Based on multiple logistic regression analysis, the adjusted odds for acquiring SIPE was 8.59 times higher for women compared to men and 12.74 times higher for the oldest age group compared to the youngest.

INTERPRETATION: The incidence of SIPE over four years during a large open water swimming event in Sweden was 0.44%. The incidence was higher in women than in men and increased with higher age.

OBJECTIVES: Indication for invasive mechanical ventilation in COVID-19 pneumonia has been a major challenge. This study aimed to evaluate if lung ultrasound (LUS) can assist identification of requirement of invasive mechanical ventilation in moderate to severe COVID-19 pneumonia.

MATERIALS AND METHODS: Between April 23 and November 12, 2020, hospitalized patients with moderate to severe COVID-19 (oxygen demand ≥4 L/min) were included consecutively. Lung ultrasound was performed daily until invasive mechanical ventilation (IMV-group) or spontaneous recovery (non-IMV-group). Clinical parameters and lung ultrasound findings were compared between groups, at intubation (IMV-group) and highest oxygen demand (non-IMV-group). A reference group with oxygen demand <4 L/min was examined at hospital admission.

RESULTS: Altogether 72 patients were included: 50 study patients (IMV-group, n = 23; non-IMV-group, n = 27) and 22 reference patients. LUS-score correlated to oxygen demand (SpO₂ /FiO₂ -ratio) (r = 0.728; p < .0001) and was higher in the IMV-group compared to the non-IMV-group (20.0 versus 18.0; p = .026). Based on receiver operating characteristic analysis, a LUS-score of 19.5 was identified as cut-off for requirement of invasive mechanical ventilation (area under the curve 0.68; sensitivity 56%, specificity 74%). In 6 patients, LUS identified critical coexisting conditions. Respiratory rate and oxygenation index ((SpO₂ /FiO₂ )/respiratory rate) ≥4.88 identified no requirement of invasive mechanical ventilation with a positive predictive value of 87% and negative predictive value of 100%.

CONCLUSIONS: LUS-score had only a moderate diagnostic value for requirement of invasive mechanical ventilation in moderate to severe COVID-19. However, LUS proved valuable as complement to respiratory parameters in guidance of disease severity and identifying critical coexisting conditions.

BACKGROUND: Despite the increasing popularity of open water swimming worldwide, swimming-induced pulmonary edema (SIPE) is a poorly recognized condition lacking established diagnostic criteria.

RESEARCH QUESTION: The aim of this study was to identify diagnostic criteria of SIPE during a large open water swimming event.

STUDY DESIGN AND METHODS: In this cross-sectional study, 17,904 individuals swam 1,000, 1,500, or 3,000 m in cold open water during Sweden's largest open water swimming event in 2018 and 2019. Of 166 swimmers seeking medical attention for acute respiratory symptoms, 160 were included in the study. Medical history, symptoms, and clinical findings were collected. On-site lung ultrasound (LUS) was performed to verify pulmonary edema.

RESULTS: Pulmonary edema was confirmed by LUS in 102 patients (64%); findings were unilateral in 11 (7%). Peripheral oxygen saturation was identified as a strong independent diagnostic test for pulmonary edema, with ≤ 95% as the suggested cut off based on receiver-operating characteristic curve analysis (area under the curve, 0.893; P < .0001). Crackles on lung auscultation, predominantly over the anterior chest, identified 88% of patients with edema. Peripheral oxygen saturation ≤ 95% or auscultation findings of crackles identified pulmonary edema with a sensitivity of 97% and a specificity of 86%. A specificity of 98% and a positive predictive value of 99% for LUS-verified pulmonary edema were reached if patients presented with both oxygen saturation ≤ 95% and auscultation of crackles.

INTERPRETATION: We suggest a clinical algorithm for diagnosis of SIPE for swimmers with acute respiratory symptoms during swimming in cold open water. Novel features of focally distributed edema in the anterior parts of the lungs, sometimes unilateral, add to this unique dataset of an underreported condition.