Respiratory Function in Voluntary Participating Patagonia Sea Lions (Otaria flavescens) in Sternal Recumbency

Abstract

We measured esophageal pressures (n = 4), respiratory flow rates (n = 5), and expired O2 and CO2 (n = 4) in five adult Patagonia sea lions (Otaria flavescens, body mass range 94.3–286.0 kg) during voluntary breaths while laying down out of water. The data were used to estimate the dynamic specific lung compliance (sCL), the O2 consumption rate (trueV˙O2) and CO2 production rates (trueV˙CO2) during rest. Our results indicate that the resting tidal volume in Patagonia sea lions is approximately 47–73% of the estimated total lung capacity. The esophageal pressures indicated that expiration is passive during voluntary breaths. The average sCL of sea lions was 0.41 ± 0.11 cmH2O−1, which is similar to those measured in anesthetized sea lions and awake cetaceans, and significantly higher as compared to humans (0.08 cmH2O−1). The average estimated trueV˙O2 and trueV˙CO2 using breath-by-breath respirometry were 1.023 ± 0.327 L O2 min−1 (range: 0.695–1.514 L O2 min−1) and 0.777 ± 0.318 L CO2 min−1, (range: 0.510–1.235 L CO2 min−1), respectively, which is similar to previously published metabolic measurements from California and Steller sea lions using conventional flow-through respirometry. Our data provide end-tidal gas composition and offer novel data for respiratory physiology in pinnipeds, which may be important for clinical medicine and conservation efforts.

Respiratory function and mechanics in pinnipeds and cetaceans

“…Understanding the respiratory traits that allow marine mammals to manage life in an extreme environment and cope daily with alveolar collapse and recruitment, extreme respiratory flow, transient hyperoxia, extreme hypoxia, hyper-and hypotension, intravascular gas bubbles, lung squeeze and inert gas narcosis is vital in understanding the physiological constraints imposed on these animals, and how these limitations may affect survival. Few studies have investigated respiratory physiology in live or awake marine mammals (Olsen et al, 1969;Ridgway et al, 1969;Kerem et al, 1975;Kooyman and Cornell, 1981;Fahlman et al, 2015b;Fahlman and Madigan, 2016). Whereas useful information can be derived from comparative studies from the molecular level to cellular, organ, systemic and whole-animal levels, probably the most valuable tool for an integrated understanding of how respiratory physiology affects diving capability is the ability to work with live trained animals voluntarily participating in research trials.…”

“…The allometric mass-exponent is significantly different from that calculated for terrestrial mammals (−0.26, Stahl, 1967); thus, for similarly sized animals, f R is significantly lower in an aquatic mammal as compared with a terrestrial one. In addition, the terrestrial breathing strategy in adult land mammals involves a brief expiratory pause whereas the aquatic breathing strategy in marine mammals involves an inspiratory pause, which often lasts for seconds to minutes (Scholander, 1940;Spencer et al, 1967;Olsen et al, 1969;Kooyman et al, 1971;Kooyman, 1973;Kerem et al, 1975;Mortola and Lanthier, 1989;Reed et al, 1994;Mortola and Limoges, 2006;Fahlman et al, 2015b;Fahlman and Madigan, 2016). In pinnipeds, this breathing strategy persists on land (Mortola and Lanthier, 1989;Mortola and Limoges, 2006;Fahlman and Madigan, 2016).…”

“…With increasing V T , the duration of the expiratory phase decreases while that of the inspiratory phase increases (Kerem et al, 1975). In Patagonia sea lions (southern sea lion, Otaria flavescens), resting while laying down, the expiratory duration is significantly longer than the inspiratory duration (Fahlman and Madigan, 2016). In the gray whale (Eschrichtius robustus), expiratory durations range greatly (Table 1) (Wahrenbrock et al, 1974;Kooyman et al, 1975;Sumich, 2001).…”

“…In addition to anatomical descriptions of the thorax of some marine mammal species (Piscitelli et al, 2010), limited work has investigated the functional and mechanical properties of the respiratory system in live animals (Scholander, 1940;Olsen et al, 1969;Kooyman et al, 1971Kooyman et al, , 1973Kooyman et al, , 1975Kerem et al, 1975;Leith, 1976;Kooyman and Cornell, 1981;Kooyman and Sinnett, 1982;Kasting et al, 1989;Leith, 1989;Reed et al, 1994Reed et al, , 2000Fahlman et al, 2014Fahlman et al, , 2015bFahlman and Madigan, 2016). For example, it has been suggested that the diaphragm and intercostal muscles are important to generate high respiratory flow and rapid f R (Ridgway, 1972;Dearolf, 2003;Cotten et al, 2008).…”

“…The relationship between estimated total lung capacity (TLC est ; broken line, Kooyman, 1973) and M b for marine mammals reveals that the volume of most breaths of marine mammals is not close to the vital capacity of the animal. References: bottlenose dolphin (Fahlman et al, 2015b), gray seal (Reed et al, 1994), Weddell seal (Kooyman et al, 1971), harbor porpoise (Reed et al, 2000), California sea lion (Kerem et al, 1975;Matthews, 1977), pilot whale (Olsen et al, 1969), killer whale (Spencer et al, 1967;Kasting et al, 1989), beluga whale (Kasting et al, 1989;Epple et al, 2015), walrus (Fahlman et al, 2015a), Patagonia sea lion (Fahlman and Madigan, 2016) Denison and Kooyman, 1973;Kooyman, 1973;Tarasoff and Kooyman, 1973;Leith, 1976;Kooyman and Sinnett, 1979;Kooyman and Cornell, 1981;Fahlman et al, 2011Fahlman et al, , 2014Fahlman et al, , 2015bMoore et al, 2011Moore et al, , 2014. Studies using trained marine mammals that voluntarily participate have been used to define flowvolume characteristics (Olsen et al, 1969;Kooyman and Cornell, 1981;Fahlman et al, 2015b;Fahlman and Madigan, 2016).…”