<i>Estimation of Critical Dead Space in Respiratory Protective Devices</i>

Stannard, J. N.; Russ, E. M.

doi:10.1152/jappl.1948.1.4.326

Cited by 17 publications

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“…Capillary PaO 2 , CO 2 and pH at peak exercise were not different between surgical mask vs. N95 vs. standard CPET facemask, suggesting that alveolar ventilation/gas exchange are not significantly impacted by facemasks(31). Work using applied external deadspace loading as a means to stimulate the respiratory system generally shows little change in the end-tidal or arterial CO 2 until the applied deadspace is greater than 100-200 ml(32)(33)(34), a value that is larger than that expected with most facemasks other than some industrial respirators. However, studies measuring transcutaneous PCO 2 as a proxy for PaCO 2 in young healthy adults show small increases of 1-2 mmHg during moderate intensity treadmill walking with an N95 respirator compared to unmasked(29).…”

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confidence: 90%

Face Masks and the Cardiorespiratory Response to Physical Activity in Health and Disease

Hopkins¹,

et al. 2021

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To minimize transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the novel coronavirus responsible for coronavirus disease (COVID-19), the U.S. Centers for Disease Control and Prevention and the World Health Organization recommend wearing face masks in public. Some have expressed concern that these may affect the cardiopulmonary system by increasing the work of breathing, altering pulmonary gas exchange and increasing dyspnea, especially during physical activity. These concerns have been derived largely from studies evaluating devices intentionally designed to severely affect respiratory mechanics and gas exchange. We review the literature on the effects of various face masks and respirators on the respiratory system during physical activity using data from several models: cloth face coverings and surgical masks, N95 respirators, industrial respirators, and applied highly resistive or high–dead space respiratory loads. Overall, the available data suggest that although dyspnea may be increased and alter perceived effort with activity, the effects on work of breathing, blood gases, and other physiological parameters imposed by face masks during physical activity are small, often too small to be detected, even during very heavy exercise. There is no current evidence to support sex-based or age-based differences in the physiological responses to exercise while wearing a face mask. Although the available data suggest that negative effects of using cloth or surgical face masks during physical activity in healthy individuals are negligible and unlikely to impact exercise tolerance significantly, for some individuals with severe cardiopulmonary disease, any added resistance and/or minor changes in blood gases may evoke considerably more dyspnea and, thus, affect exercise capacity.

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Face Masks and the Cardiorespiratory Response to Physical Activity in Health and Disease

Hopkins¹,

et al. 2021

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“…The limiting factor to the dogs' acceptance of added external dead space has not been fully determined. Stannard and Russ (20) reported that the most significant subjective change noted by humans breathing through tubes of increasing length was the resistance to airflow and the subsequently large effort necessary to ventilate through the tube. At this time, we regard the test as somewhat subjective and nonspecific.…”

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confidence: 99%

The Effects of Inhaled 90 Y Fused Clay Aerosol on Pulmonary Function and Related Parameters of the Beagle Dog

Mauderly¹,

Pickrell²,

Hobbs³

et al. 1973

Radiation Research

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“…In fact, hypoventilation associated with breathing through inspiratory resistances (5,6) can cause significant increases in CO 2 partial pressure and blood lactate, and can be indistinguishable from similar increases expected to come because of respirator dead volume. Stannard and Russ (7) determined that there was almost complete respiratory compensation at rest to mask dead volume by a tidal volume increase. This may be true at rest, but the dead volume response is smaller during mild exercise, (7) and it certainly cannot be true above the anaerobic threshold, where tidal volume is limited.…”

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confidence: 99%

“…Stannard and Russ (7) determined that there was almost complete respiratory compensation at rest to mask dead volume by a tidal volume increase. This may be true at rest, but the dead volume response is smaller during mild exercise, (7) and it certainly cannot be true above the anaerobic threshold, where tidal volume is limited. (8) Additional dead volume cannot increase exhalation flow rate during heavy breathing, when the flow rate is limited.…”

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Effect of External Dead Volume on Performance While Wearing a Respirator

Johnson

Scott

Lausted

et al. 2000

AIHAJ - American Industrial Hygiene Association

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Respirator dead volume accumulates exhaled carbon dioxide and returns it to the respiratory system during subsequent inhalations. Because inhaled carbon dioxide is known to be a powerful respiratory stimulant and psychoactive gas, respirator dead volume would be expected to influence performance times while respirators are worn during work. This experiment was performed at intense levels of treadmill walking (80-85% VO2max) to demonstrate maximum sensitivity to respiratory stress. Six dead volume conditions (representing a range of 280 to 1,160 mL) were imposed on the subjects. Results show linear decreases in performance times and breathing apparatus comfort with increasing dead volumes. For each 350 mL of external dead volume, a 19% decrease of performance time and an 18% decrease in breathing apparatus comfort can be expected.

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Estimation of Critical Dead Space in Respiratory Protective Devices

Cited by 17 publications

References 0 publications

Face Masks and the Cardiorespiratory Response to Physical Activity in Health and Disease

Face Masks and the Cardiorespiratory Response to Physical Activity in Health and Disease

The Effects of Inhaled 90 Y Fused Clay Aerosol on Pulmonary Function and Related Parameters of the Beagle Dog

Effect of External Dead Volume on Performance While Wearing a Respirator

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