An Unusual Presentation of Pulmonary Edema During an Ice Dive at Altitude

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An Unusual Presentation of Pulmonary Edema During an Ice Dive at Altitude
MILITARY MEDICINE, 188, 1/2:392, 2023

An Unusual Presentation of Pulmonary Edema During an Ice Dive
                          at Altitude
              LCDR Aliye Z. Sanou, DO, MPH, MC, USN*; LCDR Robert L. Murray, MSC, USN*,†;
             HMC Eli Hernandez, DWS/EXW/FMF/SW/AW, USN‡; LT David Sherrier, MD, MC, USN§

             ABSTRACT Military diving operations occur in a wide range of austere environments, including high-altitude envi-
             ronments and cold weather environments; however, rarely do both conditions combine. Ice diving at altitude combines
             the physiologic risks of diving, a hypothermic environment, and a high-altitude environment all in one. Careful planning
             and consideration of the potential injuries and disease processes affiliated with the aforementioned physiologic risks must

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             be considered. In this case report, we describe a Navy diver who became obtunded secondary to hypoxia during an ice
             dive at 2,987 m (9,800 ft) elevation and was subsequently diagnosed with high-altitude pulmonary edema. Further con-
             sideration of the environment, activities, and history does not make this a clear case, and swimming-induced pulmonary
             edema which physiologically possesses many overlaps with high-altitude pulmonary edema may have contributed or
             been the ultimate causal factor for the diver’s acute response.

BACKGROUND                                                                      of HAPE are reported as decreased exercise capacity, dry
A rapid ascent or travel to elevations of 2,500 m (8,000 ft)                    cough that progresses to tachypnea, tachycardia, productive
or more from the sea level presents humans with the chal-                       cough with pink frothy sputum, orthopnea, dyspnea at rest,
lenge of decreased ambient partial pressures of oxygen (PO2 )                   and hypoxia.7,9
and is associated with the risk of developing different forms                       High-altitude pulmonary edema (HAPE) is a form of non-
of high-altitude illnesses. Decreased PO2 ultimately affects                    cardiogenic pulmonary edema due to a failure in the pul-
all aspects of the oxygen transport system to the tissues and                   monary blood–gas barrier in the setting of hypobaric hypoxia.
as a result complications arise, most commonly acute moun-                      This failure is the result of many maladaptive physiologic
tain sickness (AMS), high-altitude cerebral edema (HACE),                       responses; a few of which are exaggerated and nonuni-
and high-altitude pulmonary edema (HAPE).1 While the eti-                       form pulmonary vasoconstriction, poor hypoxic ventilatory
ology of HAPE is fairly well understood, the pathophysiology                    response, and inadequate endothelial nitric oxide synthesis.
of pulmonary edema resulting from diving or swimming-                           At altitude, most persons who are susceptible to HAPE have
induced pulmonary edema (SIPE) has been ambiguous.2,3                           a poor hypoxic ventilatory response, leading to a low alveolar
Diving at altitude can confound the symptoms presented for                      PO2 and therefore a greater stimulus for hypoxic pulmonary
both HAPE and SIPE.                                                             vasoconstriction.10 However, hypoxic pulmonary vasocon-
    High-altitude illness typically occurs in individuals who                   striction is nonuniform. This leads to a patchy distribution of
ascend over 2500 m in 24 hours and progresses with symp-                        the pulmonary edema.1,9 Heavy exercise or exertion itself can
toms of headache; insomnia; gastrointestinal symptoms such                      contribute to and further increase the risk of pulmonary edema
as anorexia, nausea, vomiting, and diarrhea; and fatigue.4,5                    by increasing pulmonary blood flow and exacerbating over
These symptoms attributed most commonly to AMS generally                        perfusion to sections of the lung, leading to further capillary
resolve with acclimation or decent, but as affected individ-                    stress and vascular leaking into the lung parenchyma.1,10
uals remain at or ascend in altitude AMS may advance to                             The treatment for HAPE focuses primarily on descent and
HACE and HAPE.6,7 High-altitude cerebral edema (HACE)                           supplemental oxygen. When descent is not practical, admin-
is conceptualized as an extreme form and progression of AMS                     istering supplemental oxygen via nasal cannula or facemask
where additional neurological findings of lethargy, ataxia, or                  with a goal SpO2 greater than 90% may be a suitable alter-
altered mental status affect the individual.7,8 Early symptoms                  native to descent.11 Further elaboration of the mechanisms
                                                                                behind HAPE or its presentation and treatment is beyond the
   * Force                                                                      scope of this report but can be reviewed elsewhere.1,5,7,10,11
            Surgeon’s Office, Unit 35605, III Marine Expeditionary Force,
FPO, AP 96382-5605, USA                                                             Swimming-induced pulmonary edema (SIPE), also some-
    † Uniformed Services University, Bethesda, MD 20814, USA                    times called scuba dive pulmonary edema, occurs in swim-
    ‡ Surface Warfare Medical Institute, San Diego, CA 92134, USA               mers and divers in cold water, with symptoms similar to
    § Navy Experimental Dive Unit, Panama City Beach, FL 32407, USA
                                                                                HAPE: dyspnea, chest tightness, cough, hemoptysis, and
    The opinions and assertions expressed herein are those of the authors and   hypoxia occurring during water submersion with exercise.12
do not reflect the official policy or position of the associations with which   The SIPE symptoms last up to 48 hours and typically resolve
they are affiliated, including the Department of Defense.
    doi:https://doi.org/10.1093/milmed/usac081                                  spontaneously. Care is supportive and includes removing
   Published by Oxford University Press on behalf of the Association of         the stricken patient from water and placing them in a warm
Military Surgeons of the United States 2022. This work is written by (a) US     environment. More aggressive therapy includes supplemental
Government employee(s) and is in the public domain in the US.                   oxygen and inhaled beta-2 agonists. Additionally, continuous

392                                                                                   MILITARY MEDICINE, Vol. 188, January/February 2023
An Unusual Presentation of Pulmonary Edema During an Ice Dive at Altitude
Pulmonary Edema During an Ice Dive at Altitude

positive airway pressure, nitroglycerine, antibiotics, and pred-                snow, setting up heavy equipment, and acclimatizing to the
nisolone have also been used as adjunct therapies.12                            area without dives. During the first 3 days at the camp, the
   In this case, the first of its kind in published literature,                 diver noted that he felt more winded than usual with exercise
we report on the difficulties in differentiating the diagnoses                  and snow shoveling. He was able to engage in these activi-
of HAPE and SIPE in a diver at altitude and propose that                        ties despite this, and his discomfort was not apparent to his
the pathophysiologic pathways that lead to HAPE and SIPE                        teammates. He reported a stabbing headache to his medical
may work synergistically, rendering ice divers at altitude                      provider—an independent duty corpsman (IDC)—the fourth
at an increased risk of either or both types of pulmonary                       night at camp. His headache was partially relieved by 800 mg
edema.                                                                          Motrin and completely relieved by the addition of caffeine.
                                                                                Retrospectively, the diver noted that his headache would
CASE PRESENTATION                                                               return throughout his time at the camp and was minimal in
A 27-year-old male active duty Navy diver traveled with                         daytime and worse at night, causing him periods of insomnia.

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a detachment team from his unit on the Atlantic seaboard                        He did not endorse mental fog, gastrointestinal symptoms, or
(sea level) to a reservoir in Utah (elevation 2,987 m or                        dyspnea at rest at any time. Vital signs were taken by the IDC
9,800 ft) for the purpose of training for ice dives (Fig. 1). The               on all members of the team at the onset of the camp stay,
team flew in to Las Vegas, NV, altitude 610 m (2,001 ft) and                    and it was noted that pulse oxygen levels of members were
drove to the reservoir diving site within 24 hours in order to                  anywhere from 89% to 96% on ambient air.
set up camp. The initial plan to acclimatize and ascend more                        On the morning of the fifth day at camp, the diver and
slowly over a 5- to 6-day period was altered after snowstorms                   his dive partner completed an ice dive (Fig. 2). Diving at
on the Atlantic seaboard delayed their westward flight. For the                 altitude requires using a separate set of calculations for dive
first 3 days at the camp, primary activities included shoveling                 table decompression due to the reduced atmospheric pressure.

FIGURE 1. Ice dive—overhead view of camp. The tent, at the center of the circle, is the primary entry and exit point for divers.

MILITARY MEDICINE, Vol. 188, January/February 2023                                                                                         393
An Unusual Presentation of Pulmonary Edema During an Ice Dive at Altitude
Pulmonary Edema During an Ice Dive at Altitude

To calculate decompression requirements, sea level equivalent                   water within a minute. His total time underwater for the dive
depth (SLED), also known as the “cross correction” tech-                        evolution was 20 minutes. At this point the diver experienced
nique, is applied as follows:                                                   amnesia. His team noted that he was speaking nonsensically
                                                                                to his dive partner over the communication system as he was
          Equivalent depth (ft seawater)                                        being extracted from the water. At the surface, his facemask
                                                                                was removed, revealing a cyanotic facial complexion. He was
              = Altitude depth (ft seawater)
                                                                                immediately started on O2 . After less than a minute on a 10-L
                 Pressure at sea level (1.00 atmosphere)                        non-rebreather facemask of O2 , the member reported that he
             ×
                    Pressure at altitude (atmosphere)                           could think clearly again. His pulse oxygen (OX) saturation
                                                                                was noted to be 100% while on non-rebreather after extrac-
                                                                                tion and resuscitation. His dive unit members remarked that
   The altitude environment necessitates divers to have added
                                                                                he had been breathing heavily during the dive as could be

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decompression to their dives.13 The diver and his partner
                                                                                heard over the communication system and suspected that his
undertook their first dive to a maximum depth of 15 ft
                                                                                symptoms were all consistent with a hypoxic event. As per the
(physiologic SLED equivalent 25 ft) without any incident. On
                                                                                protocol, dive injury was suspected and immediate full neuro-
the morning of the sixth day at camp, the diver and his part-
                                                                                logic, cardiac, and pulmonary exams were performed, which
ner completed a more strenuous ice dive to a maximum depth
                                                                                revealed no neurologic or cardiac findings. The pulmonary
of 30 ft (SLED equivalent 45 ft), with finning underwater for
                                                                                exam was significant for tachypnea, with his respiratory rate
approximately 15 minutes. During this dive, the diver and his
                                                                                at 20 and pulse ox reading 85% on ambient air after the oxygen
partner returned to the surface to receive equipment and then
                                                                                mask was removed, but otherwise benign with good inspira-
submerged again and moved approximately 15 ft away from
                                                                                tory effort and all lung fields clear to auscultation bilaterally.
the ice hole. At that time, the diver reported feeling air hunger
                                                                                The member endorsed no chest pain, dyspnea, palpitations,
mixed with a feeling of euphoria, anxiety, lightheadedness,
                                                                                coughing, or air hunger. He endorsed that he felt winded with
headache, and tunnel vision. He immediately signaled his dive
                                                                                minimal exertion and noted the persistent headache, but other-
partner and his tender that he needed to abort the dive and
                                                                                wise stated that he was feeling well. His IDC tested the pulse
return to the surface. He was extracted and removed from the
                                                                                ox machine (only one available) on other team members to see
                                                                                if it was compromised. Other members had readings between
                                                                                89% and 94% O2 on ambient air.
                                                                                    The diver was given an albuterol inhaler and Mucinex by
                                                                                his IDC and continued to be observed closely through the day
                                                                                and overnight. The next day, he was noted to have a pulse ox
                                                                                reading that dropped from 85% to 74% on ambient air dur-
                                                                                ing vigorous walking. An adjunct flight nurse present with
                                                                                a standby helicopter medevac crew drew an arterial blood
                                                                                gas, with the notable finding of PO2 of 53 mmHg (refer-
                                                                                ence range 80-90 mmHg). A repeat cardiopulmonary exam
                                                                                was conducted by the IDC. Although the member remained
                                                                                clear to auscultation bilaterally in all lung fields, paradoxi-
                                                                                cally the IDC reported positive findings for bronchophony,
                                                                                egophony, tactile fremitus, and whispered pectoriloquy, each
                                                                                indicating signs of consolidation in the right upper lobe.

FIGURE 2. Ice diver entering the water. One of the two divers entering water,   FIGURE 3. (A) and (B) Both lateral and posterior–anterior chest X-rays were
with the umbilical line in the hands of the dive tender.                        read as unremarkable by radiologist.

394                                                                                     MILITARY MEDICINE, Vol. 188, January/February 2023
Pulmonary Edema During an Ice Dive at Altitude

These paradoxical findings were observed by both the IDC                     use a commercial flight home in the next 24-48 hours by the
and the flight nurse. At this point, the diver was transported               treating physician.
by vehicle to a local emergency room at an altitude of 1,830 m
(6,008 ft) for his persistent hypoxia and findings on physical               DISCUSSION
exam.                                                                        This case focuses on a well-trained and physically conditioned
    Upon arrival at the local emergency room after a 30-minute               27-year-old diver who became obtunded during his second
transit by car, the member had a benign physical exam without                ice dive at altitude, with relief of symptoms with oxygen and
significant findings. Pulse ox readings were 98% on room air.                descent to a lower altitude. Before the patient’s second dive,
Preliminary chest X-ray read by the emergency room physi-                    he experienced symptoms consistent with AMS: headache
cian and IDC showed mild edema between upper and middle                      that was worse at night but responsive to caffeine and dyspnea
lobes of the right lung. The emergency room physician inter-                 with minimal exertion. The acute symptoms experienced by
preted this in the context of the patient’s history as HAPE.                 the diver during the second dive—euphoria, impaired mem-

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However, the X-ray was read as unremarkable by the radiol-                   ory, and air hunger are consistent with an acute hypoxic event.
ogist on duty (Fig. 3). The D-Dimer was negative. The diver                  Ultimately, the diver was diagnosed with HAPE; but given the
was diagnosed with HAPE and started on nifedipine and kept                   constellation of symptoms and their chronology, the case is
at low altitude for the remainder of the trip. He was cleared to             worth revisiting.

FIGURE 4. Shared pathogenesis of HAPE and SIPE. Figure is derived from text and diagrams in Smith et al.3 and Li et al.9

MILITARY MEDICINE, Vol. 188, January/February 2023                                                                                      395
Pulmonary Edema During an Ice Dive at Altitude

    The diver was exposed to multiple potentiating factors            individuals who have previously ascended or been at altitude
that are shared by both HAPE and SIPE pathophysiologies;              many times, despite no history of previous complication.16
these include cold, vigorous exercise, and sympathetic over-          Some literature on SIPE cases suggest that once an individ-
activity induced by decreased PO2 . Similarities exist between        ual has had one episode, they are more likely to have repeat
the pathophysiologic mechanisms believed to underlie both             episodes with cool water or cool air swimming and dives.12
HAPE and SIPE; water immersion and exertion lead to cen-              The military experience with special operations reports the
tralized pooling of blood in the cardiovascular unit, elevating       opposite—that one episode of SIPE does not predispose to
pulmonary artery pressure.2,3 Patchy or nonuniform areas of           further episodes.14 Based on what is known about the patho-
pulmonary vasoconstriction lead to some capillaries experi-           physiology and as demonstrated in the reported case here,
encing higher pressure and subsequent leakage.12 Exertion             the same physiologic factors are at work, leading to cases of
exacerbates both the work of breathing and airway pressures,          HAPE and SIPE that may potentiate each other (see Fig. 4).
resulting in further capillary permeability14 (Fig. 4). These         This case illustrates the importance of having dive and swim-

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contributing factors resulted in a pathology common to both           ming personnel and their medical attendants understand that
HAPE and SIPE: increased pulmonary artery pressure leading            multiple environments may potentiate common pathophys-
to patchy capillary leakage, tachypnea, and eventual dysp-            iologies and complicate differential diagnoses. Mitigation
nea and worsening hypoxia. Other diving-specific injuries,            strategies and training need to be tailored for each event to
such as decompression sickness or arterial gas embolism, are          best support prevention and in case of occurrence, diagnosis
unlikely in this case, given his dive profile and that the onset of   and treatment.
symptoms occurred at depth. The possibility of either hypo-
or hypercapnia combined with hypoxia should be considered.                                            FUNDING
Hypocapnia is more likely, given heavy breathing was heard            There was no funding received for this case report.
over the communication system and hyperventilation is com-
mon in cold-water diving. When combined with hypoxia,                           CONFLICT OF INTEREST STATEMENT
hypo- or hypercapnia potentiates the symptoms of hypoxia.15           None declared.
An altitude diver experiencing AMS that may be progressing
toward HAPE would be potentially more prone to respiratory                                        REFERENCES
injury, leading to worsening hypoxia and disturbance in the
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Pulmonary Edema During an Ice Dive at Altitude

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MILITARY MEDICINE, Vol. 188, January/February 2023                                                                                          397
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