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At least 145 records · Page 8Linked to original sources
PubMed1976

The effect of hypercapnia on respiratory characteristics and diving behaviour of freely diving seals.

Three trained young seals, one harp seal, Pagophilus groenlandicus, and two hooded seals, Cystophora cristata, have been used to study the effect of hypercapnia on respiratory characteristics and diving behaviour. The seals were allowed free movements within a circular pool, while diving and respiratory behaviour were recorded. During the experiments the alveolar CO2 tension was continually recorded. There was a significant decrease in duration of dives with increasing Paco2 for all animals. Ve increased significantly with increasing Paco2. This increase was caused by more frequent surfacing rather than by a higher respiratory frequency during the breathing periods. Tidal volume increased from 3 to 43% when inspired CO2 was increased from 0.03 to 9 vol%. The seals were all found to be less sensitive to CO2 than man. A decreased sensitivity to CO2 with age is suggested from the results.

Age Factors↗
PubMed1979

Mechanical properties of the harbor porpoise lung, Phocoena phocoena.

The pressure-volume and pressure-flow characteristics of the excised lungs of 5 harbor porpoise were determined. It was found that: (1) in comparison to terrestrial mammals the lung volume relative to body weight is large, (2) the lungs are capable of emptying to less than 17% of total lung capacity, (3) peak expiratory flowrates of 5 to 10 vital capacities (VC).sec-1 are relatively high for mammals, (4) isovolume pressure flow curves showed a clustering of flowrate plateaus from 40 to 80% VC, with a marked drop in the flow rate plateau at 20% VC, (5) the profile of flow-volume curves is unusually square shaped with flows remaining above 2 VC.sec-1 at a lung volume of 20% VC, (6) this feature is responsible for the short emptying time of less than 0.2 sec. It is concluded that cartilaginous airway reinforcement, which extends to the alveolar sac, is responsible for the unusual flow-volume properties. These porpoises have the capability of exchanging a large percent of their lung gas very rapidly during their brief pass through the air-water interface.

Animals↗
PubMed1983

Respiratory adaptations in diving mammals.

This report examines the evidence for the presence of oxygen stores in the lungs, blood and systemic musculature of diving mammals, the modifications in the respiratory functions of blood that may be important in utilizing the lung and blood oxygen stores, and the potential importance of the oxygen stores and the respiratory functions of blood in supporting short-duration, aerobic dives. Increasing oxygen stores by increasing lung volume does not occur in diving mammals. The long-duration diving whales have small lung volumes which results in lung collapse during dives and the seals dive following partial expiration which produces the same effect. The short-duration diving dolphins, porpoises and rodents have lung volumes comparable to terrestrial mammals, dive following inspiration and appear to use the lungs as an oxygen store. Adaptations in the oxygen affinity of the blood parallel the modifications in lung volume. Where the lungs do not represent a potential oxygen store the oxygen affinity is low, maximizing the unloading of oxygen while maintaining a high tissue oxygen tension. Where the lungs do represent an oxygen store, the affinity is high, maximizing the uptake of oxygen from the alveolar space. Increases in the concentration of respiratory pigment in the blood and in muscle are important adaptations in diving mammals. The blood oxygen stores in diving mammals vary from near normal to over three times normal for terrestrial mammals while the muscle oxygen stores vary from near normal to nearly ten times normal. The degree to which the blood and muscle oxygen stores are increased can be equated to the duration of the dive and demands for oxygen; longer duration divers and those with higher metabolic demands have greater oxygen stores than divers that remain submersed for shorter periods or have lower rates of oxygen utilization.

Animals↗