Continuous Positive Airway Pressure as Adjunct Treatment of Acute Altitude Illness

Abstract

Walmsley, Megan. Continuous positive airway pressure as adjunct treatment of acute altitude illness. High Alt Med Biol 14:405–407, 2013.—Altitude related illness occurs in unacclimatized individuals ascending to altitudes over 2500 m. Treatment usually involves descending to lower altitudes and pharmacological therapies. There are very few cases, studies, or recommendations regarding the use of positive pressure ventilation in acute mountain sickness (AMS) or high altitude pulmonary edema (HAPE). This case describes the use of CPAP as part of the treatment of a trekker diagnosed with AMS and HAPE in a remote location at 4200 m in Nepal.

Case Report

A62-year-old, previously well trekker had planned to trek to Everest Base Camp in Nepal. He was assessed and treated for altitude-related illness at the Himalayan Rescue Association clinic in Pheriche, altitude 4200 m.

The trekker had a standard ascent profile for the region. He commenced the trek at Lukla airport (2800 m). Two days later, he arrived in Namche Bazaar (3420 m) where he spent 2 nights. He then had 1 night in Tengbouche (3870 m) before reaching Pheriche (4200 m). He had no previous exposure to high altitude and had been taking prophylactic acetazolamide (125 mg bd) as prescribed by his family doctor in the United States.

On arrival in Pheriche, the trekker complained of a worsening headache for the past 2 days. He had a cough of 3 days' duration, difficulty sleeping for the past 3 nights, and had taken zolpidem in Namche Bazaar. During the day of presentation, he had been feeling tired and weak and had been lagging behind his trekking group. He had worsening shortness of breath and was short of breath at rest on arrival. He complained of moderate dizziness but no confusion or nausea.

On examination, he was afebrile with heart rate of 100 bpm and oxygen saturation of 70%. He had increased work of breathing, with dyspnea, an increased respiratory rate, and labored breathing. He also had widespread crepitations and wheezes to auscultation, as well as a wet sounding cough. He was orientated, but ataxic and unable to walk in a straight line. He had a Lake Louise Score of 11.

The trekker was diagnosed with acute mountain sickness (AMS), high altitude pulmonary edema (HAPE), and early high altitude cerebral edema (HACE) (Table 1).

Table 1.

Diagnosis of Altitude Illness. The Lake Louise Consensus on the Definition of Altitude Illness

AMS	In the setting of a recent gain in altitude, the presence of headache and at least one of the following symptoms:
	- gastrointestinal (anorexia, nausea or vomiting)
	- fatigue or weakness
	- dizziness or lightheadedness
	- difficulty sleeping
HACE	Can be considered “end stage” or severe AMS. In the setting of a recent gain in altitude, either:
	- the presence of a change in mental status and/or ataxia in a person with AMS
	- or, the presence of both mental status changes and ataxia in a person without AMS
HAPE	In the setting of a recent gain in altitude, the presence of the following:
	Symptoms: at least two of:
	- dyspnea at rest
	- cough
	- weakness or decreased exercise performance
	- chest tightness or congestion
	Signs: at least two of:
	- crackles or wheezing in at least one lung field
	- central cyanosis
	- tachypnea
	- tachycardia

The initial treatment consisted of dexamethasone (8 mg po), nifedipine (30 mg SR po), acetazolamide (250 mg po), and salbutamol via puffer. He was also placed on CPAP (7 cm H₂0, Fio₂ 21%) via a nasal mask. The CPAP device had a built in humidifier and was small and portable (Remstar, Phillips Respironics, USA). It was operated with a lithium battery (Novuscell, Battery Geeks, Austin, Texas, USA), which could be recharged via portable solar cells.

The trekker responded well to CPAP and within a short space of time had a marked improvement in shortness of breath and work of breathing. His O₂ saturation quickly improved to 92%. This was a much more rapid response to treatment than had previously been observed in other patients using medications alone. In this situation, the trekker was treated with CPAP instead of oxygen, which was available at the clinic via an oxygen concentrator. Due to the rapid improvement in both oxygen saturations and respiratory effort, it was felt that CPAP provided adequate treatment. It also had the additional benefit of being battery operated and so not draining the limited electricity supplies of the clinic.

The trekker slept in the clinic overnight on CPAP. He slept well for the first time in several nights, and the following morning had HR 66 bpm and SaO₂ 86%. His headache had resolved, and fatigue and dizziness improved. His ataxia had improved but was still present. His shortness of breath had also improved but was still present on exertion. His Lake Louise Score was 2.

The trekker decided to discontinue his trek and was taken to Kathmandu via helicopter the morning after presentation.

Discussion

Acute high altitude illness describes the neurological and respiratory syndromes experienced when unacclimatized individuals ascend too rapidly to high altitude (Brown and Grocott, 2013). It includes acute mountain sickness (AMS), high altitude cerebral edema (HACE), and high altitude pulmonary edema (HAPE).

Altitude-related illnesses most commonly occur at altitudes over 2500 m (Basnyat and Tabin, 2012; Luks et al., 2010). They are associated with the reduction in the partial pressure of oxygen in inspired gas that occurs with the fall in barometric pressure during ascent (Basnyat and Tabin, 2012; Imray et al., 2010).

The characteristics of altitude-related illness are described in Table 1.

HACE and HAPE and potentially fatal conditions

The current suggested approach to treatment of AMS and HACE includes: descent, supplemental oxygen, simulated descent using portable hyperbaric chamber, acetazolamide, and dexamethasone (Imray et al., 2010; Luks et al., 2010).

The current suggested treatment for HAPE includes: descent, supplemental oxygen, portable hyperbaric chamber, nifedipine, beta-agonists, and phosphodiesterase inhibitors (Imray et al., 2010; Luks et al., 2010; Stream and Grissom, 2008).

Noninvasive positive pressure ventilation (NIPPV) is a well established and effective treatment of cardiogenic pulmonary edema (Peter et al., 2006; Vital et al., 2008). However, NIPPV modes such as CPAP are not used routinely during either the treatment of noncardiogenic pulmonary edemas such as HAPE, or in the treatment of AMS. A literature search of the topic revealed very few instances in which NIPPV was used or recommended in the treatment of HAPE or AMS.

One small study published in 1985 demonstrated the use of expiratory positive airway pressure (EPAP) to transiently improve gas exchange in HAPE. Four climbers with HAPE at rest and 13 healthy climbers were studied (Schoene et al., 1985). Another small study, also published in 1985, of 3 climbers with and 5 without HAPE, found an improvement in O₂ saturation in HAPE subjects after EPAP (Larson, 1985). Agostoni et al. (2010) applied CPAP (7 cm H₂0) for 30 min to healthy individuals at 4559 m and found that CPAP increased hemoglobin O₂ saturation after acute, but not prolonged, exposure to high altitude.

One case report demonstrated the successful use of BiPAP, along with pharmacological treatment for severe HAPE. However, this was in the ICU setting as opposed to the remote setting in which HAPE frequently occurs (Gregorius et al., 2008). Another case report described effective use of a CPAP helmet in a mountaineer at 5300 m (Koch et al., 2009).

Burgess and Johnson (2004) concluded that desaturation during sleep has an association with AMS. Johnson (2010) then went on to use positive pressure ventilation (PPV) on subjects sleeping at 3800 m. It was found that subjects sleeping with PPV had both increased sleeping oxygen saturation and a decrease in symptoms of AMS. Johnson (2013) later looked at the feasibility of using CPAP in the remote high altitude setting and the use of CPAP in the treatment of AMS at 4200 m in Nepal. It was concluded that the availability of both CPAP machines and batteries, which are small and lightweight, and the use of batteries, which can be recharged via a portable roll up solar panel, made the use of CPAP at altitude much more feasible.

Fourteen subjects with AMS were treated with overnight CPAP (6–7 cm H₂O) in addition to acetazolamide (250 mg, po). Subjects had both a significant increase in overnight sleeping oximetry and decrease in AMS symptoms as demonstrated by a deceased score on Lake Louise Questionnaire (Johnson et al., 2013). Johnson (2013) postulated that this improvement in both oxyhemoglobin saturation and AMS symptoms observed after overnight CPAP was multifactorial. Increased alveolar gas exchange, recruitment of microatelectatic alveoli, and prevention of upper airway collapse during sleep, as well as shift of fluid from the alveolar–capillary membrane are all probable factors.

The current Wilderness Medical Society Consensus Guidelines for the Prevention and Treatment of Acute Altitude Illness have not suggested CPAP for the treatment of AMS. CPAP for the treatment of HAPE has been classified as a weak recommendation (grade 2B). The guidelines recommend considering use in the hospital setting, but found it was generally not feasible in the field setting and that the required level of pressure had not been established (Luks et al., 2010).

The lack of evidence and logistical difficulties of using CPAP for HAPE was also recognized in update and review articles (Maggiorini, 2006; Stream and Grissom, 2008).

Conclusion

As increasing numbers of trekkers and mountaineers continue to visit high altitude regions such as the Himalayas, altitude related illnesses are likely to remain a common diagnosis. This case demonstrates that, in conjunction with standard pharmacological therapy, CPAP can be successfully used as adjunct therapy in the treatment of AMS and HAPE. The availability of small, portable CPAP devices, which are used with a lightweight, rechargeable lithium battery, means that CPAP could be more widely available in remote locations such as the Everest region. Further studies are now needed to fully investigate the utility of CPAP in the treatment of AMS.

Footnotes

Author Disclosure Statement

No competing financial interests exist.

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