The effect of alveolar dead space on the measurement of end-expiratory lung volume by modified nitrogen wash-out/wash-in in lavage-induced lung injury.

Abstract

BACKGROUND:

The accuracy of end-expiratory lung volume measurement by the modified nitrogen wash-out/wash-in method (EELV-N(2)) depends on the precise determination of carbon dioxide elimination (V(CO(2))), which is affected by alveolar dead space (V(D-alv)). The purpose of this study was to investigate the influence of V(D-alv) on EELV-N(2).

METHODS:

Six piglets with lavage-induced acute lung injury were mechanically ventilated in a decremental PEEP trial that was reduced from 20 to 4 cm H(2)O in steps of 4 cm H(2)O every 10 min. EELV was measured by the modified EELV-N(2) method and computed tomography scan (EELV-CT), volumetric capnography, blood gas measurements, and hemodynamic data were recorded at each PEEP level. The data were divided into higher and lower PEEP groups.

RESULTS:

During the decremental PEEP trial, EELV-N(2) exhibited a high correlation (r(2) = 0.86, P < .001) with EELV-CT, with a bias of -48.6 ± 150.7 mL (1 ± 18%). In the higher PEEP group, EELV-N(2) was not correlated with EELV-CT, with a bias of -168.1 ± 171.5 mL (-14 ± 14%). However, in the lower PEEP group, EELV-N(2) exhibited a high correlation (r(2) = 0.86, P < .001) with EELV-CT, with a bias of 11.2 ± 97.2 mL (6 ± 17%). The measurement bias was negatively correlated with V(D-alv) (r(2) = 0.44, P = .04) and V(CO(2)) (r(2) = 0.47, P = .03) in the higher PEEP group.

CONCLUSIONS:

In this surfactant-depleted model, EELV measurement by the modified EELV-N(2) method reveals a systematic underestimation at high PEEP levels that is partly due to an increase in V(D-alv).

• Authors: Rui Tang, Yingzi Huang, Qiuhua Chen, Xia Hui, Yang Li, Qing Yu, Hongjie Zhao, Yi Yang, Haibo Qiu
• Journal: Respiratory care (Respir Care) Vol. 57 Issue 12 Pg. 2074-81 (Dec 2012) ISSN: 0020-1324 [Print] United States
• PMID: 22613077 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Nitrogen

Topics

• Acute Lung Injury (physiopathology)
• Animals
• Capnography
• Disease Models, Animal
• Female
• Lung Volume Measurements
• Male
• Nitrogen
• Positive-Pressure Respiration
• Pulmonary Alveoli
• Respiratory Dead Space (physiology)
• Swine
• Therapeutic Irrigation