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. Apr-Jun 2018;30(2):144-152.
doi: 10.5935/0103-507X.20180028.

Sizing the Lung in Dogs: The Inspiratory Capacity Defines the Tidal Volume

[Article in Portuguese, English]
Affiliations
Free PMC article

Sizing the Lung in Dogs: The Inspiratory Capacity Defines the Tidal Volume

[Article in Portuguese, English]
Pablo Alejandro Donati et al. Rev Bras Ter Intensiva. .
Free PMC article

Abstract

Objective: To evaluate a novel physiological approach for setting the tidal volume in mechanical ventilation according to inspiratory capacity, and to determine if it results in an appropriate mechanical and gas exchange measurements in healthy and critically ill dogs.

Methods: Twenty healthy animals were included in the study to assess the tidal volume expressed as a percentage of inspiratory capacity. For inspiratory capacity measurement, the mechanical ventilator was set as follows: pressure control mode with 35cmH2O of inspired pressure and zero end-expiratory pressure for 5 seconds. Subsequently, the animals were randomized into four groups and ventilated with a tidal volume corresponding to the different percentages of inspiratory capacity. Subsequently, ten critically ill dogs were studied.

Results: Healthy dogs ventilated with a tidal volume of 17% of the inspiratory capacity showed normal respiratory mechanics and presented expected PaCO2 values more frequently than the other groups. The respiratory system and transpulmonary driving pressure were significantly higher among the critically ill dogs but below 15 cmH2O in all cases.

Conclusions: The tidal volume based on the inspiratory capacity of each animal has proven to be a useful and simple tool when setting ventilator parameters. A similar approach should also be evaluated in other species, including human beings, if we consider the potential limitations of tidal volume titration based on the calculated ideal body weight.

Objetivo: Avaliar uma nova abordagem fisiológica para a determinação do volume corrente em ventilação mecânica, de acordo com a capacidade inspiratória, e determinar se isso resulta em medidas mecânicas e de troca gasosa adequadas em cães saudáveis e em estado crítico.

Métodos: Incluíram-se, neste estudo, 24 animais para avaliar o volume corrente expresso como porcentagem da capacidade inspiratória. Para mensuração da capacidade inspiratória, o ventilador mecânico foi regulado como segue: modo controle de pressão, com 35cmH2O de pressão de inspiração e pressão expiratória final de zero, por 5 segundos. Subsequentemente, estudaram-se dez cães em condições clínicas críticas.

Resultados: Cães saudáveis ventilados com volume corrente que correspondia a 17% da capacidade inspiratória demonstraram mecânica respiratória normal e apresentaram os valores previstos de PaCO2 mais frequentemente do que os animais nos demais grupos. A pressão no sistema respiratório e a pressão transpulmonar foram significantemente mais elevadas nos cães em condição crítica, porém em todos os casos, estiveram abaixo de 15cmH2O.

Conclusões: O volume corrente calculado com base na capacidade inspiratória de cada animal comprovou ser uma ferramenta útil e simples para o estabelecimento dos parâmetros do ventilador. Convém também realizar abordagem semelhante em outras espécies, inclusive no ser humano, quando se consideram as potenciais limitações da titulação do volume corrente, com base no peso corpóreo ideal calculado.

Conflict of interest statement

Conflicts of interest: None.

Figures

Figure 1
Figure 1
Relationship between body weight and inspiratory capacity in healthy dogs. IC - inspiratory capacity.
Figure 2
Figure 2
Tidal volume per kg of body weight according to inspiratory capacity percentage group. IC - inspiratory capacity.
Figure 3
Figure 3
Partial pressure of carbon dioxide according to the inspiratory capacity percentage group. Horizontal dashed lines represent the expected partial pressure of carbon dioxide value. PaCO2 - partial pressure of carbon dioxide; IC - inspiratory capacity.
Figure 4
Figure 4
Static respiratory system and transpulmonary inspiratory pressures according to tidal volume group. IC - inspiratory capacity.

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