Roland Close

Validation of impulse oscillometry in Friesian and Blue Belgian calves with respect to changes in extrathoracic upper airway resistance

Impulse oscillometry (IOS) was compared with conventional pulmonary function techniques (using oesophageal balloon and airflow measurements). Healthy Friesian (FR) and Blue Belgian (BB) calves were examined in different conditions of extrathoracic airway resistance (physiological and vertical head position). Higher resistance values were detected in BB calves compared with FR calves with both conventional and forced oscillation techniques in both head positions. Upper airway narrowing was characterised by increasing resistance values without changes in frequency dependence. Measuring input impedance in animals using a face mask, a considerable capacitive shunt of the upper airways (including the capacitive components of the mask) has to be taken into account. Even if the absolute value of this capacitive component is constant, its influence on the measurement results increases with growing frequency and with an increase in upper airway resistance. In conclusion, (1) impulse oscillometry is sensitive to upper airway resistance changes and (2) face mask capacitance is important and has frequency dependent effects on the respiratory impedance.

Validation of the monofrequency forced oscillation technique for pulmonary function investigation in calves: an in vitro and in vivo study

This study was to investigate whether the monofrequency forced oscillation (MFO) technique could be accurately used for pulmonary function testing in calves. The airflow resistance measured by this technique was compared to the resistance measured by the classical reference method by an in vitro study, using an artificial lung model, and by an in vivo study, using 11 healthy calves. The effect of the reference impedance of this oscillation equipment was also investigated. The results show linear relationships (r2 > 0.924, P < 0.001) in the resistance ranges 0 to 0.7 kPa litre-1 s and 0 to 1.0 kPa litre-1 s with a reference impedance of 1.0 kPa litre-1 s and 2.0 kPa litre-1 s, respectively. The MFO resistance values lower and higher than 0.4 kPa litre-1 s are slightly overestimated and underestimated, respectively. It was shown that, if some technical requirements are met, the MFO technique is a simple, reproducible, fast and accurate method which allows measurement of airflow resistance even in field conditions.

Monofrequency forced oscillation technique for the investigation of pulmonary function in calves: in vitro and in vivo studies

Parameters derived from the non-invasive and simple monofrequency forced oscillation technique were compared with classical parameters of ventilatory mechanics in order to assess its usefulness for the investigation of pulmonary function in calves. To facilitate this comparison, theoretical derivations were coupled with in vitro measurements, using an artificial lung model, and with in vivo studies. These studies compared the oscillatory resistance parameters (Ros and Re) and the respiratory system compliance (Crs) against the classical pulmonary resistance (RL) and the dynamic compliance (Cdyn), respectively. Ros and Re were highly correlated (r > or = 0.87) with RL and the comparison between Crs and Cdyn gave a similarly high correlation (r > or = 0.88). Given its simplicity, its correspondence with classical parameters and its rapidity and reproducibility, monofrequency forced oscillation technique seems well suited for the investigation of pulmonary function under field conditions.

Use of the monofrequency forced oscillation technique to measure changes in upper airway resistance in Friesian and blue Belgian calves

Monofrequency forced oscillometry (MFO) using a sinusoidal test signal of one frequency (10 Hz) was compared with the classical pulmonary function technique (using an oesophageal balloon with airflow measurements) in two breeds of cattle which differ in their respiratory physiology, particularly to assess changes in upper airway resistance. Six healthy male Friesian calves (mean [SD] bodyweight 131 [12] kg) and six healthy male blue Belgian calves (mean [SD] bodyweight 137 [13] kg) were examined successively with their heads either in a normal position or held vertically, using a cross-over study design. In the normal position, higher resistances, a higher respiratory impedance, and lower values of the dynamic lung compliance (Cdyn) were measured in the blue Belgian than in the Friesian calves. In the vertical head position, total pulmonary resistance (RL) increased and Cdyn decreased significantly (P < 0.05). The changes in MFO-derived parameters were in accordance with the changes in classical parameters, and for both methods, the percentage changes were markedly higher in the blue Belgian calves.

Physical Properties of Particles of Ipratropium and Clenbuterol Generated by Equipment Suitable for the Inhalation of Drugs by Calves

When solutions of ipratropium and clenbuterol were atomised at 300 kPa and 450 kPa in equipment suitable for the inhalation of drugs by calves, the numbers, velocities and diameters of the particles produced were similar. When the pressure was increased to 600 kPa more of the particles were less than 2 microns in diameter and fewer were more than 7 microns in diameter, the fractions of the total mass of the solution generated in these size ranges were similarly increased and decreased, and the velocities of the particles were increased. At any given pressure, the numbers of particles of different sizes, and the proportions of the total mass generated, were similar for the solutions of ipratropium and clenbuterol, but a solution of saline produced more particles with a diameter less than 3 microns. Particles from the solution of ipratropium had the highest velocity and particles from the solution of clenbuterol had the lowest velocity.

Deposition in the distal parts of the bovine respiratory tract: assessment of equipment suitable for drug inhalation

The efficiency of equipment suitable for the inhalation of drugs by calves was assessed in six animals which inhaled radioisotopically labelled particles while suffering from reversible diffuse bronchoconstriction induced experimentally with 5-hydroxytryptamine and while they were breathing normally. Respiratory rates and data from pulmonary function tests and scintiscans were recorded during both investigations. After the first investigation, a mean (se) wash-out period of 9.8 (3.2) days was allowed. Under diffuse bronchoconstriction, the respiratory rate, the oscillatory resistance and the compliance of the respiratory system reached 282.1 (22.0), 161.1 (10.8) and 68.8 (2.7) per cent of their respective baseline values. When the calves were breathing normally these parameters did not change over time. The ratios (Cp/Ct) of the counts of γ-disintegrations in the peripheral part (Cp) of the lungs and in the total lung area (Ct) were not significantly different when comparing the results from the two investigations. The ratios of Cp/Ct in the left lungs did not differ significantly from those in the right lungs.