Cardiovascular Adjustments to Heat Stress

Johnson, John M.; Proppe, D. W.

doi:10.1002/cphy.cp040111

Cited by 215 publications

(296 citation statements)

References 235 publications

(237 reference statements)

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“…We found limited effect modification of respiratory heat effects by climate, which could be explained if respiratory heat effects are triggered by very brief exposure to heat, because even widespread use of air conditioning cannot eliminate brief (e.g., <10 min) outdoor heat exposure. Although an hour or more of exposure is required for some thermoregulatory responses to heat (39), a few minutes of heat exposure can trigger direct human airway responses to inhaling hot air. This rapid response has been demonstrated in studies of asthma (40,41), and it likely operates through the cholinergic reflex pathway (40,42,43).…”

Section: Discussionmentioning

confidence: 99%

Heat-related Emergency Hospitalizations for Respiratory Diseases in the Medicare Population

Anderson¹,

Dominici

Wang

et al. 2013

Am J Respir Crit Care Med

212

168

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Rationale: The heat-related risk of hospitalization for respiratory diseases among the elderly has not been quantified in the United States on a national scale. With climate change predictions of more frequent and more intense heat waves, it is of paramount importance to quantify the health risks related to heat, especially for the most vulnerable. Objectives: To estimate the risk of hospitalization for respiratory diseases associated with outdoor heat in the U.S. elderly. Methods: An observational study of approximately 12.5 million Medicare beneficiaries in 213 United States counties, January 1, 1999 to December 31, 2008. We estimate a national average relative risk of hospitalization for each 10 8 F (5.6 8 C) increase in daily outdoor temperature using Bayesian hierarchical models. Measurements and Main Results: We obtained daily county-level rates of Medicare emergency respiratory hospitalizations (International Classification of Diseases, Ninth Revision,(464)(465)(466)(480)(481)(482)(483)(484)(485)(486)(487)(490)(491)(492) in 213 U.S. counties from 1999 through 2008. Overall, each 10 8 F increase in daily temperature was associated with a 4.3% increase in same-day emergency hospitalizations for respiratory diseases (95% posterior interval, 3.8, 4.8%). Counties' relative risks were significantly higher in counties with cooler average summer temperatures. Conclusions: We found strong evidence of an association between outdoor heat and respiratory hospitalizations in the largest population of elderly studied to date. Given projections of increasing temperatures from climate change and the increasing global prevalence of chronic pulmonary disease, the relationship between heat and respiratory morbidity is a growing concern.Keywords: chronic obstructive pulmonary disease; hospitalization; hot temperature; respiratory tract infections; weatherOutdoor heat can cause spikes in respiratory deaths (1, 2), but considerably less is known about heat's impacts on respiratory morbidity. Given that: (1) climate change will increase exposure to extreme heat (3), (2) the prevalence of chronic respiratory diseases is increasing (4), and (3) the elderly will likely be most affected by heat-related problems (5), there is a pressing need to improve our understanding of respiratory heat effects among the elderly for both fatal and nonfatal outcomes.There are two major limitations to current research on the relationship between heat and respiratory hospitalizations. First, this relationship has not been adequately studied worldwide to confidently identify a consistent link between respiratory hospitalizations and heat. The few studies that have investigated heat and respiratory hospitalizations have found somewhat conflicting results (6). For example, studies of Brisbane, Australia (7,8) and Athens, Greece (9) found hospitalization rates decreased slightly during hot weather, whereas studies of California (10, 11), New York (12, 13), and 12 European cities (14) found respiratory hospitalizations increased with heat. Although a me...

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Section: Discussionmentioning

confidence: 99%

Heat-related Emergency Hospitalizations for Respiratory Diseases in the Medicare Population

Anderson¹,

Dominici

Wang

et al. 2013

Am J Respir Crit Care Med

212

168

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“…Furthermore, SkBF and the cutaneous microvascular reactivity are subject to diurnal rhytms (Aoki et al, 2003). Another modulator that resets the threshold for active cutaneous vasodilation is physical exercise (Johnson, 1996;Rowell, 1993) that is covered in more detail elsewhere in the chapter.…”

Section: Neural Control Mechanismsmentioning

confidence: 99%

“…During exposure to cold it can be reduced to almost zero, whereas it can increase up to 8 l/min during strenous exercise in a hot environment. It is thus obvious that it plays an important role in hemodynamics, since during strenous exercise and in severe heat stress it can comprise over 50% of the cardiac output, as compared to only 5% in resting thermoneutral conditions (Johnson, 1996;Rowell, 1993). The range of flows is therefore wide, and, in extreme conditions, high SkBF also represents a burden on the working heart.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Human Skin Microcirculation and Its Endothelial Function Using Laser Doppler Flowmetry

Lenasi¹

2011

Medical Imaging

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“…THE CONTROL of human skin blood flow is critical for the regulation of internal temperature and, during heat stress, for blood pressure regulation (8,16,17). Mechanisms that regulate skin blood flow are impaired in the normal ageing process and in a variety of physiological diseases such as diabetes and congestive heart failure (3,7,18,19,22,27).…”

mentioning

confidence: 99%

Methodological assessment of skin and limb blood flows in the human forearm during thermal and baroreceptor provocations

Wingo

Hubing

Crandall³

2010

Journal of Applied Physiology

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Brothers RM, Wingo JE, Hubing KA, Crandall CG. Methodological assessment of skin and limb blood flows in the human forearm during thermal and baroreceptor provocations. J Appl Physiol 109: 895-900, 2010. First published July 15, 2010 doi:10.1152/japplphysiol.00319.2010.-Skin blood flow responses in the human forearm, assessed by three commonly used technologies-single-point laser-Doppler flowmetry, integrated laser-Doppler flowmetry, and laser-Doppler imaging-were compared in eight subjects during normothermic baseline, acute skin-surface cooling, and whole body heat stress (⌬ internal temperature ϭ 1.0 Ϯ 0.2°C; P Ͻ 0.001). In addition, while normothermic and heat stressed, subjects were exposed to 30-mmHg lower-body negative pressure (LBNP). Skin blood flow was normalized to the maximum value obtained at each site during local heating to 42°C for at least 30 min. Furthermore, comparisons of forearm blood flow (FBF) measures obtained using venous occlusion plethysmography and Doppler ultrasound were made during the aforementioned perturbations. Relative to normothermic baseline, skin blood flow decreased during normothermia ϩ LBNP (P Ͻ 0.05) and skin-surface cooling (P Ͻ 0.01) and increased during whole body heating (P Ͻ 0.001). Subsequent LBNP during whole body heating significantly decreased skin blood flow relative to control heat stress (P Ͻ 0.05). Importantly, for each of the aforementioned conditions, skin blood flow was similar between the three measurement devices (main effect of device: P Ͼ 0.05 for all conditions). Similarly, no differences were identified across all perturbations between FBF measures using plethysmography and Doppler ultrasound (P Ͼ 0.05 for all perturbations). These data indicate that when normalized to maximum, assessment of skin blood flow in response to vasoconstrictor and dilator perturbations are similar regardless of methodology. Likewise, FBF responses to these perturbations are similar between two commonly used methodologies of limb blood flow assessment. heat stress; blood flow; laser-Doppler flowmetry

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Cardiovascular Adjustments to Heat Stress

Cited by 215 publications

References 235 publications

Heat-related Emergency Hospitalizations for Respiratory Diseases in the Medicare Population

Heat-related Emergency Hospitalizations for Respiratory Diseases in the Medicare Population

Assessment of Human Skin Microcirculation and Its Endothelial Function Using Laser Doppler Flowmetry

Methodological assessment of skin and limb blood flows in the human forearm during thermal and baroreceptor provocations

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