Accession Number:

ADA224680

Title:

Influence of Cold Exposure on Ventilation, Respiratory Heat Loss, and Pulmonary Deposition/Clearance

Descriptive Note:

Doctoral thesis

Corporate Author:

AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH

Personal Author(s):

Report Date:

1990-06-25

Pagination or Media Count:

170.0

Abstract:

Possible thermoregulatory benefits of cold-induced changes in breathing pattern hypoventilation and the mechanisms by which cold stimulates a change in breathing pattern were investigated in male Holstein calves 1-3 months old. Effects of ambient temperatures Ta between 4 and 18 C on ventilatory parameters and respiratory heat loss were determined in 4 calves. As Ta decreased, respiratory frequency decreased 29 while tidal volume increased 35. Total ventilation VE did not change significantly, but the ventilatory equivalent for O2 decreased with decreasing Ta. Calves were capable of conserving respiratory heat during cold exposure by decreasing expired air temperature and by decreasing dead space ventilation while increasing O2 extraction. hypoventilation is suggested as a mode of heat conservation in cold environments in animals which use panting as a means of increasing evaporative heat loss. The effect of cold-induced hypoventilation on pulmonary particle deposition was investigated in 10 calves. Deposition of nasally-instilled fluorescent Pasteurella haemolytica was significantly higher for cold-exposed calves. It is speculated that the cold-induced respiratory pattern change was responsible. Nasal mucus velocity NMV was measured in four unanesthetized calves at Ta 2-4 C and Ta 16-18 C, using a radiographic tracking technique. NMV was 24 lower during cold exposure. It is possible that cold-exposure decreases tracheal mucociliary clearance rate. It is speculated that mucociliary clearance rate may be partially genetically determined. Cold-induced decreases in particle clearance, and increases in deposition, may predispose calves to respiratory infection. Keyword Dissertations.

Subject Categories:

  • Biology

Distribution Statement:

APPROVED FOR PUBLIC RELEASE