Recruitment in networks of pulmonary capillaries

West, J. B.; Schneider, Alan M.; Mitchell, M. M.

doi:10.1152/jappl.1975.39.6.976

Cited by 29 publications

(19 citation statements)

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“…In a complex network, however, pressure gradients between feeders and drainers could fall to zero as elements in other parts of the network are recruited, which would cause that element to close (derecruit). In other circumstances, the pressure in the drainer could exceed the feeder pressure, thus reversing the direction of flow, as predicted by West et al (32) and observed in these experiments.…”

supporting

confidence: 81%

“…The scatter in the data of Godbey et al as capillaries recruited suggests confirmation of the Warrell data, i.e., that capillary recruitment could be heterogeneous. West et al (32), using an elegant computer model, deduced that recruitment in a network of resistors could be heterogeneous. Nevertheless, the variety of models, each based on credible evidence, does not present a coherent picture of how alveolar capillaries recruit.…”

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confidence: 99%

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Heterogeneous capillary recruitment among adjoining alveoli

Baumgartner

Jaryszak

Peterson

et al. 2003

Journal of Applied Physiology

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. Heterogeneous capillary recruitment among adjoining alveoli. J Appl Physiol 95: 469-476, 2003; 10.1152/ japplphysiol.01115.2002.-Pulmonary capillaries recruit when microvascular pressure is raised. The details of the relationship between recruitment and pressure, however, are controversial. There are data supporting 1) gradual homogeneous recruitment, 2) sudden and complete recruitment, and 3) heterogeneous recruitment. The present study was designed to determine whether alveolar capillary networks recruit in a variety of ways or whether one model predominates. In isolated, pump-perfused canine lung lobes, fields of six neighboring alveoli were recorded with video microscopy as pulmonary venous pressure was raised from 0 to 40 mmHg in 5-mmHg increments. The largest group of alveoli (42%) recruited gradually. Another group (33%) recruited suddenly (sheet flow). Half of the neighborhoods had at least one alveolus that paradoxically derecruited when pressure was increased, even though neighboring alveoli continued to recruit capillaries. At pulmonary venous pressures of 40 mmHg, 86% of the alveolar-capillary networks were not fully recruited. We conclude that the pattern of recruitment among neighboring alveoli is complex, is not homogeneous, and may not reach full recruitment, even under extreme pressures. pulmonary microcirculation; isolated perfused lung lobes; video microscopy; dogs PULMONARY CAPILLARIES ARE recruited with increasing microvascular pressure. Different investigators, however, have found different patterns of recruitment. With the introduction of the zone model, West et al. (31) showed that pulmonary blood flow increased down a vertical gradient as pulmonary arterial and venous pressures increased relative to alveolar pressure. Glazier and colleagues (6) studied red blood cell distributions in rapidly frozen lungs and showed that there was gradual, homogeneous recruitment as capillary pressure increased, especially in zone 2. Fung and Sobin (5) developed the sheet flow theory, which suggested that the entire capillary bed opened suddenly and completely as capillary transmural pressure exceeded alveolar pressure. This hypothesis was supported experimentally by Sobin et al. (19), who studied latex casts of the capillary bed. Godbey et al. (9) showed in excised lungs that sheet flow tended to occur at low airway pressure when alveoli were not highly distended, whereas gradual recruitment tended to occur in more distended alveoli. Although the zone and sheet flow models predict homogeneous recruitment, Warrell et al. (28), studying rapidly frozen lungs under zone 2 conditions, found an uneven distribution of capillary red blood cells within areas likely to have been supplied by a common arteriole. The scatter in the data of Godbey et al. as capillaries recruited suggests confirmation of the Warrell data, i.e., that capillary recruitment could be heterogeneous. West et al. (32), using an elegant computer model, deduced that recruitment in a network of resistors could be heterogeneous. Nevertheless...

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confidence: 81%

mentioning

confidence: 99%

Heterogeneous capillary recruitment among adjoining alveoli

Baumgartner

Jaryszak

Peterson

et al. 2003

Journal of Applied Physiology

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“…65(9): 965-970, 2003 In normal dogs, an increase in pulmonary blood flow is associated with a decrease in pulmonary vascular resistance without a marked elevation in pulmonary arterial pressure [14,15]. The reduction in pulmonary vascular resistance is generally considered to be due to capillary recruitment and/ or dilatation [6,19]. In dogs with heartworm disease, however, the reduction in pulmonary vascular resistance that accompanies an increase in cardiac output is smaller in magnitude than normal dogs [12,13].…”

mentioning

confidence: 99%

“…The reduction in pulmonary vascular resistance is generally considered to be due to capillary recruitment and/ or dilatation [6,19]. In dogs with heartworm disease, however, the reduction in pulmonary vascular resistance that accompanies an increase in cardiac output is smaller in magnitude than normal dogs [12,13].…”

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confidence: 99%

Pressure-Flow Relationship and Longitudinal Distribution of Pulmonary Vascular Resistance in Heartworm-Infected Dogs

Kondo

Washizu

Matsukura

et al. 2003

The Journal of Veterinary Medical Science

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ABSTRACT. The pressure-flow relationships and the longitudinal distributions of pulmonary vascular resistance in normal and heartworminfected (HWI) dogs were compared in an isolated, blood perfused preparation. The pulmonary circulation was partitioned into pulmonary arterial, middle, and venous segment based on the concept of a five element lumped model. The pulmonary arterial pressure-flow relationships were found to be non-linear and convex to the pressure axis in both normal and HWI lungs. The pressure-flow relationships of the pulmonary arterial and venous segment were linear and these slopes in the HWI lungs were significantly higher than the normal lungs. The pressure gradient of the middle segment was increased as flow increased at lower flow range, however, it was not increased during higher perfusion range in both lungs. At higher flow, the pressure gradient of the middle segment in the HWI lungs was significantly higher than the normal lungs. These results suggest that the ohmic resistance was almost equal to the sum of the two slopes of the pressure-flow relationships of the pulmonary arterial and venous segment because the pressure gradient of the middle segment was not altered as flow increased during higher perfusion rate. Because the slopes of the pressure-flow relationships of the pulmonary arterial and venous segment were increased with heartworm infection, the ohmic resistance of HWI lungs would be higher than normal lungs. The intercept pressure on the pressure axis of the linear portion of the pulmonary arterial pressure-flow relationship, a critical closing pressure, was regarded as pressure gradient of the middle segment during higher perfusing rate because the intercept pressures of pressure-flow relationships of pulmonary arterial and venous segment were almost equal to zero. Therefore, the critical closing pressure of HWI lungs would be higher than normal lungs. The pulmonary hypertension of filariasis appears to be due to an increase in ohmic resistance and elevated critical closing pressure. KEY WORDS: canine, filariasis, pressure-flow relationship, pulmonary vascular resistance, vascular occlusion technique.J. Vet. Med. Sci. 65(9): 965-970, 2003 In normal dogs, an increase in pulmonary blood flow is associated with a decrease in pulmonary vascular resistance without a marked elevation in pulmonary arterial pressure [14,15]. The reduction in pulmonary vascular resistance is generally considered to be due to capillary recruitment and/ or dilatation [6,19]. In dogs with heartworm disease, however, the reduction in pulmonary vascular resistance that accompanies an increase in cardiac output is smaller in magnitude than normal dogs [12,13]. The capillary bed in heartworm-infected (HWI) dogs may not be able to recruit and/or dilate efficiently with the increase in cardiac output [14,15]. The behaviors of the pulmonary vasculature in HWI dogs in response to increases in cardiac output have not been well studied.In this study, pressure-flow curves at different perfusing flows were obtaine...

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“…Thereafter, PA flow and pressure were recorded during irregular pacing (R-R intervals uniformly distributed reduction of the perfused pulmonary vascular bed in unilateral lung is expected to double both RP and ZC and halve CP, 12 the pulmonary circulation is unique in that a recruitment phenomenon, that is, opening up of previously closed peripheral vessels, occurs when PA flow and pressure increase. 13, 14 As the recruitment phenomenon likely compensates for the increase in RP with little impact on ZC, RP may not increase proportionally to ZC when a large volume of the pulmonary vascular bed is lost, such as in the case of acute PTE in the proximal PA. The fact that the ratio of ZC to RP in the pulmonary circulation is not as small as that in the systemic circulation 15,16 also indicates the importance of assessing both ZC and RP in the pulmonary circulation.…”

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confidence: 99%