Respiration

Powell, Frank L.

doi:10.1016/b978-0-12-407160-5.00013-0

Cited by 20 publications

(18 citation statements)

References 203 publications

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“…2). In a mammal that exhales passively, this would have little physiological consequence, but because birds expire actively, even at rest (Powell, 2015), increased expiratory compliance should reduce the elastic work of every breath and allow the highland birds to breathe using larger tidal volumes than lowland birds for a given power output. When the flow component was introduced (dynamic measurements), however, highland species were not found to be consistently more compliant than lowland species and, in the case of the ruddy ducks and cinnamon teals, the highland birds were significantly less compliant.…”

Section: Discussion Morphological and Mechanical Variation In Avian Rmentioning

confidence: 99%

Respiratory mechanics of eleven avian species resident at high and low altitude

York

Chua

Ivy

et al. 2017

Journal of Experimental Biology

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The metabolic cost of breathing at rest has never been successfully measured in birds, but has been hypothesized to be higher than in mammals of a similar size because of the rocking motion of the avian sternum being encumbered by the pectoral flight muscles. To measure the cost and work of breathing, and to investigate whether species resident at high altitude exhibit morphological or mechanical changes that alter the work of breathing, we studied 11 species of waterfowl: five from high altitudes (>3000 m) in Peru, and six from low altitudes in Oregon, USA. Birds were anesthetized and mechanically ventilated in sternal recumbency with known tidal volumes and breathing frequencies. The work done by the ventilator was measured, and these values were applied to the combinations of tidal volumes and breathing frequencies used by the birds to breathe at rest. We found the respiratory system of high-altitude species to be of a similar size, but consistently more compliant than that of lowaltitude sister taxa, although this did not translate to a significantly reduced work of breathing. The metabolic cost of breathing was estimated to be between 1 and 3% of basal metabolic rate, as low or lower than estimates for other groups of tetrapods.

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Section: Discussion Morphological and Mechanical Variation In Avian Rmentioning

confidence: 99%

Respiratory mechanics of eleven avian species resident at high and low altitude

York

Chua

Ivy

et al. 2017

Journal of Experimental Biology

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“…Some CAS methods rely simply on reduction of oxygen to levels below which the bird cannot survive typically by diluting air with argon or nitrogen so that oxygen is below 2 to 5% for 2 to 5 minutes. Powell ( 2015 ) summarized the physiology of hypoxia in poultry and noted that broilers show changes in the depth and rate of respiration at 15% and arrhythmia of the heart rate around 7% oxygen. At ≤5% oxygen, there are profound effects in the brain, respiratory, and cardiovascular systems resulting in cardiovascular collapse (see Raj, Gregory and Wotton, 1991 ; Woolley and Gentle, 1998 ; Raj et al., 2008 and Powell, 2015 ).…”

Section: Introductionmentioning

confidence: 99%

Effects of ambient temperature and water vapor on chamber pressure and oxygen level during low atmospheric pressure stunning of poultry

Holloway¹,

Pritchard²

2017

Poultry Science

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The characteristics of the vacuum used in a low atmospheric pressure stunning system to stun (render unconscious) poultry prior to slaughter are described. A vacuum chamber is pumped by a wet screw compressor. The vacuum pressure is reduced from ambient atmospheric pressure to an absolute vacuum pressure of ∼250 Torr (∼33 kPa) in ∼67 sec with the vacuum gate valve fully open. At ∼250 Torr, the sliding gate valve is partially closed to reduce effective pumping speed, resulting in a slower rate of decreasing pressure. Ambient temperature affects air density and water vapor pressure and thereby oxygen levels and the time at the minimum total pressure of ∼160 Torr (∼21 kPa) is varied from ∼120 to ∼220 sec to ensure an effective stun within the 280 seconds of each cycle. The reduction in total pressure results in a gradual reduction of oxygen partial pressure that was measured by a solid-state electrochemical oxygen sensor. The reduced oxygen pressure leads to hypoxia, which is recognized as a humane method of stunning poultry. The system maintains an oxygen concentration of <5% for at least 2 minutes, which ensures that birds are irreversibly stunned. Calculated pump down (pressure versus time) data match experimental data very closely because the programmable logic controller and the human machine interface enable precise and accurate control. The vacuum system operates in the turbulent viscous flow regime, and is best characterized by absolute vacuum pressure rather than gauge pressure. Neither the presence of broiler chickens nor different fore-line pipe designs of four parallel commercial systems affected the pressure-time data. Water in wet air always reduces the oxygen concentrations to a value lower than in dry air. The partial pressure of water and oxygen were found to depend on the pump down parameters due to the formation of fog in the chamber and desorption of water from the birds and the walls of the vacuum chamber.

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“…Collapse of the air capillaries has also long been considered unlikely because of their probable inability to reexpand secondary to their small diameter and radius of curvature (Duncker, 1974(Duncker, , 1972. Given that lung air volume is about 10% of the total respiratory air volume (Duncker, 1974;Powell, 2015;Scheid, 1979), it has been previously postulated that some compensatory mechanism must occur in birds diving deeper than 90-100 m (Croll et al, 1992).…”

Section: Baroprotection: Potential Mechanismsmentioning

confidence: 99%

“…Spontaneous ventilation and air sac volume change with anesthesia and body position; in addition, air sac volume differs between spontaneous and artificial ventilation (Hawkins et al, 2013;King and Payne, 1964;Malka et al, 2009;Scheid et al, 1974). Shrinkage/expansion of cast materials, injection/inflation pressures and differences in abdominal mass can all contribute to potential error and variation in measurements (Powell, 2015;Scheid and Piiper, 1969). Although inert gas washout techniques have been used to measure air sac volume during steady-state ventilation (Scheid et al, 1974), such techniques do not provide the largest volumes that might be attained during a maximum inspiration prior to the dive of a penguin.…”

Section: Techniquementioning

confidence: 99%

“…The estimated oxygen store of the lungs and air sacs of various penguin species constitutes 30-45% of the total body oxygen store in comparison to 5-20% in most marine mammals (Burns et al, 2007;Ponganis et al, 2011). In addition, although the air sacs of birds are compliant and presumably collapse under ambient pressure at depth (Jones and Furilla, 1987;Powell, 2015), requirements for the avoidance of pulmonary barotrauma ('lung squeeze') in the relatively rigid avian lung may limit the routine and maximum dive depths of penguins. It is unknown how tissue disruption in the walls of the air capillaries and parabronchi is avoided at depth.…”

Section: Introductionmentioning

confidence: 99%

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Penguin lungs and air sacs: implications for baroprotection, oxygen stores and buoyancy

Ponganis

Leger

Scadeng

2015

Journal of Experimental Biology

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The anatomy and volume of the penguin respiratory system contribute significantly to pulmonary baroprotection, the body O 2 store, buoyancy and hence the overall diving physiology of penguins. Therefore, three-dimensional reconstructions from computerized tomographic (CT) scans of live penguins were utilized to measure lung volumes, air sac volumes, tracheobronchial volumes and total body volumes at different inflation pressures in three species with different dive capacities [Adeĺie (Pygoscelis adeliae), king (Aptenodytes patagonicus) and emperor (A. forsteri) penguins]. Lung volumes scaled to body mass according to published avian allometrics. Air sac volumes at 30 cm H 2 O (2.94 kPa) inflation pressure, the assumed maximum volume possible prior to deep dives, were two to three times allometric air sac predictions and also two to three times previously determined end-of-dive total air volumes. Although it is unknown whether penguins inhale to such high volumes prior to dives, these values were supported by (a) body density/buoyancy calculations, (b) prior air volume measurements in free-diving ducks and (c) previous suggestions that penguins may exhale air prior to the final portions of deep dives. Based upon air capillary volumes, parabronchial volumes and tracheobronchial volumes estimated from the measured lung/airway volumes and the only available morphometry study of a penguin lung, the presumed maximum air sac volumes resulted in air sac volume to air capillary/ parabronchial/tracheobronchial volume ratios that were not large enough to prevent barotrauma to the non-collapsing, rigid air capillaries during the deepest dives of all three species, and during many routine dives of king and emperor penguins. We conclude that volume reduction of airways and lung air spaces, via compression, constriction or blood engorgement, must occur to provide pulmonary baroprotection at depth. It is also possible that relative air capillary and parabronchial volumes are smaller in these deeper-diving species than in the spheniscid penguin of the morphometry study. If penguins do inhale to this maximum air sac volume prior to their deepest dives, the magnitude and distribution of the body O 2 store would change considerably. In emperor penguins, total body O 2 would increase by 75%, and the respiratory fraction would increase from 33% to 61%. We emphasize that the maximum pre-dive respiratory air volume is still unknown in penguins. However, even lesser increases in air sac volume prior to a dive would still significantly increase the O 2 store. More refined evaluations of the respiratory O 2 store and baroprotective mechanisms in penguins await further investigation of species-specific lung morphometry, start-of-dive air volumes and body buoyancy, and the possibility of air exhalation during dives.

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Respiration

Cited by 20 publications

References 203 publications

Respiratory mechanics of eleven avian species resident at high and low altitude

Respiratory mechanics of eleven avian species resident at high and low altitude

Effects of ambient temperature and water vapor on chamber pressure and oxygen level during low atmospheric pressure stunning of poultry

Penguin lungs and air sacs: implications for baroprotection, oxygen stores and buoyancy

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