Effects of Inspired CO2 and Breathing Resistance on Neurocognitive and Postural Stability in U.S. Navy Divers

Haran, F. Jay; Lovelace, Amelia H.

doi:10.21236/ad1003579

Cited by 3 publications

(3 citation statements)

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“…In a subsequent study by Haran and Lovelace, U.S. Navy Divers were exposed to up to 2% surface equivalent value (SEV) CO 2 with an imposed external breathing resistance of up to 1.8 kPa (gauge, equivalent to 13.5 mmHg) during endurance exercise testing at a depth of 12 fsw (1.35 ATA). While physical symptoms such as headache increased with both higher resistance and higher inspired CO 2 , there was no significant change in cognition (measured before and after exercise by a subset of Automated Neuropsychological Assessment Metrics) or in balance [23].…”

Section: Cognitive Impairmentsmentioning

confidence: 80%

“…In fact, at very high levels (over about 10% inspired CO 2 ), hypercapnia is known to uniformly cause unconsciousness [99]. Conversely, at low levels, hypercapnia is often tolerated [23][24][25]. At levels between these two extremes, hypercapnia is thought to exert both physical and mental effects, although there is some inconsistency with regard to its observed cognitive effects.…”

Section: Physical and Cognitive Impact Of Hypercapniamentioning

confidence: 99%

“…During exercise, however, elevations in inspired PCO 2 are less tolerated and can lead to carbon dioxide retention [22]. The resulting hypercapnia is often tolerated to an extent [23][24][25], but can lead to incapacitation or to unconsciousness [3,4,7,9,11,12,15]. In divers, such incapacitation is especially problematic and can be deadly [14].…”

Section: Introductionmentioning

confidence: 99%

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Hypercapnia in diving: a review of CO2 retention in submersed exercise at depth

Dunworth

Natoli

Cooter

et al. 2017

UHM

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Carbon dioxide (CO 2) retention, or hypercapnia, is a known risk of diving that can cause mental and physical impairments leading to life-threatening accidents. Often, such accidents occur due to elevated inspired carbon dioxide. For instance, in cases of CO 2 elimination system failures during rebreather dives, elevated inspired partial pressure of carbon dioxide (PCO 2) can rapidly lead to dangerous levels of hypercapnia. Elevations in P a CO 2 (arterial pressure of CO 2) can also occur in divers without a change in inspired PCO 2. In such cases, hypercapnia occurs due to alveolar hypoventilation. Several factors of the dive environment contribute to this effect through changes in minute ventilation and dead space. Predominantly, minute _____________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________ KEYWORDS: carbon dioxide; carbon dioxide retention; hypercapnia; PCO 2 ; P a CO 2 ; P ET O 2 ; diving; Haldane effect ventilation is reduced in diving due to changes in respiratory load and associated changes in respiratory control. Minute ventilation is further reduced by hyperoxic attenuation of chemosensitivity. Physiologic dead space is also increased due to elevated breathing gas density and to hyperoxia. The Haldane effect, a reduction in CO 2 solubility in blood due to hyperoxia, may contribute indirectly to hypercapnia through an increase in mixed venous PCO 2. In some individuals, low ventilatory response to hypercapnia may also contribute to carbon dioxide retention. This review outlines what is currently known about hypercapnia in diving, including its measurement, cause, mental and physical effects, and areas for future study.

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Section: Cognitive Impairmentsmentioning

confidence: 80%

Section: Physical and Cognitive Impact Of Hypercapniamentioning

confidence: 99%