### Abstract

Traditional descriptions of the pressure-volume properties of the craniospinal axis have expressed pressure as a function of volume. This study develops a theoretical and practical rationale for expressing volume as a function of pressure. We tested the rationale by comparing the two functions using pressure and volume data collected from 37 hydrocephalic patients during ventricular fluid removal. Two equivalent expressions were evaluated, one expressing pressure as an exponential function of volume and one relating volume as an exponential function of pressure. Each expression had three parameters, adjustable to the specific case. We used a nonlinear curve-fitting algorithm to determine the best estimate of the parameters. We could fit three-parameter exponential functions of either type to the data in all cases. We found a superior goodness-of-fit to aggregated data when expressing volume as a three-parameter exponential function of pressure changes. This finding is discussed in the context of the preferable number of parameters in a model and the interpretation of the terms in the models. This 'reversed' volume-pressure relationship has importance in the development of more complicated models involving these same relationships.

Original language | English (US) |
---|---|

Pages (from-to) | 694-699 |

Number of pages | 6 |

Journal | Neurosurgery |

Volume | 15 |

Issue number | 5 |

State | Published - 1984 |

Externally published | Yes |

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### ASJC Scopus subject areas

- Clinical Neurology
- Surgery

### Cite this

*Neurosurgery*,

*15*(5), 694-699.

**A comparison of pressure-volume models in hydrocephalus.** / Simon, R. H.; Lehman, R. A W; O'Connor, Sean.

Research output: Contribution to journal › Article

*Neurosurgery*, vol. 15, no. 5, pp. 694-699.

}

TY - JOUR

T1 - A comparison of pressure-volume models in hydrocephalus

AU - Simon, R. H.

AU - Lehman, R. A W

AU - O'Connor, Sean

PY - 1984

Y1 - 1984

N2 - Traditional descriptions of the pressure-volume properties of the craniospinal axis have expressed pressure as a function of volume. This study develops a theoretical and practical rationale for expressing volume as a function of pressure. We tested the rationale by comparing the two functions using pressure and volume data collected from 37 hydrocephalic patients during ventricular fluid removal. Two equivalent expressions were evaluated, one expressing pressure as an exponential function of volume and one relating volume as an exponential function of pressure. Each expression had three parameters, adjustable to the specific case. We used a nonlinear curve-fitting algorithm to determine the best estimate of the parameters. We could fit three-parameter exponential functions of either type to the data in all cases. We found a superior goodness-of-fit to aggregated data when expressing volume as a three-parameter exponential function of pressure changes. This finding is discussed in the context of the preferable number of parameters in a model and the interpretation of the terms in the models. This 'reversed' volume-pressure relationship has importance in the development of more complicated models involving these same relationships.

AB - Traditional descriptions of the pressure-volume properties of the craniospinal axis have expressed pressure as a function of volume. This study develops a theoretical and practical rationale for expressing volume as a function of pressure. We tested the rationale by comparing the two functions using pressure and volume data collected from 37 hydrocephalic patients during ventricular fluid removal. Two equivalent expressions were evaluated, one expressing pressure as an exponential function of volume and one relating volume as an exponential function of pressure. Each expression had three parameters, adjustable to the specific case. We used a nonlinear curve-fitting algorithm to determine the best estimate of the parameters. We could fit three-parameter exponential functions of either type to the data in all cases. We found a superior goodness-of-fit to aggregated data when expressing volume as a three-parameter exponential function of pressure changes. This finding is discussed in the context of the preferable number of parameters in a model and the interpretation of the terms in the models. This 'reversed' volume-pressure relationship has importance in the development of more complicated models involving these same relationships.

UR - http://www.scopus.com/inward/record.url?scp=0021736535&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0021736535&partnerID=8YFLogxK

M3 - Article

C2 - 6504284

AN - SCOPUS:0021736535

VL - 15

SP - 694

EP - 699

JO - Neurosurgery

JF - Neurosurgery

SN - 0148-396X

IS - 5

ER -