Mechanics of the respiratory system in healthy newborn calves using impulse oscillometry

[Comparison of different resuscitation methods for newborn calves after dystocia]

OBJECTIVE

This study aimed to compare the use of hand-powered vacuum pumps and the suspension by the hind legs within the scope of resuscitating newborn dystocial calves.

MATERIAL AND METHODS

For this study, data were collected from 60 dystocial calves of different breeds. Various reanimation methods were employed to these calves immediately after birth. In group I (n=20), the hand-powered vacuum pump from HK-Rheintechnik (Neuwied, Deutschland) was used to remove mucus and amniotic fluid from the respiratory tract. In group II (n=20), the McCulloch Medical (Elmwood, England) hand-powered vacuum pump was used to remove mucus and amniotic fluid from the respiratory tract. In group III (n=20) 10 to 12 liters of cold water were poured over the neck of 20 calves immediately after birth. In addition, the calves were suspended by the hind legs via a gate or a pole, so that the head hung downwards vertically. The calves' Time to Sternal Recumbency (T-SR) of the calves was measured following the different resuscitation procedures in order to assess their vitality. In addition, the calves were examined segmentally at one-hour post natum. Furthermore, the calves were examined clinically on the seventh day of life. In addition, we investigated whether confounding variables such as calf sex, dam parity, obstetric intervention, and the season affected T-SR.

RESULTS

T-SR ranged from 1.5 to 10.5 minutes. There was no difference between the three initial treatment procedures (p=0.07). However, the T-SR of calves treated with a hand-powered vacuum pump tended to be shorter. No statistically significant difference between the pulse rates (p=0.73), respiratory rates (p=0.13), and rectal temperature (p=0.65) of the animals in the three groups on the first and seventh day of life was evident. There was no statistically significant difference in the incidence of the diseases up to the seventh day of life between the individual study groups.

CONCLUSION AND CLINICAL RELEVANCE

The present study was able to show that the use of hand-powered vacuum pumps is at least equivalent to suspending calves. When using hand-powered vacuum pumps, the girth of the muzzle must be taken into account, as this can limit their utility.

Assessment of Postnatal Pulmonary Adaption in Bovine Neonates Using Electric Impedance Tomography (EIT)

Several aspects of postnatal pulmonary adaption in the bovine neonate remain unclear, particularly the dynamics and regional ventilation of the lungs. We used electric impedance tomography (EIT) to measure changes in ventilation in the first 3 weeks of life in 20 non-sedated neonatal calves born without difficulty in sternal recumbency. Arterial blood gas variables were determined in the first 24 h after birth. Immediately after birth, dorsal parts of the lungs had 4.53% ± 2.82% nondependent silent spaces (NSS), and ventral parts had 5.23% ± 2.66% dependent silent spaces (DSS). The latter increased in the first hour, presumably because of gravity-driven ventral movement of residual amniotic fluid. The remaining lung regions had good ventilation immediately after birth, and the percentage of lung regions with high ventilation increased significantly during the study period. The centre of ventilation was always dorsal to and on the right of the theoretical centre of ventilation. The right lung was responsible for a significantly larger proportion of ventilation (63.84% ± 12.74%, p < 0.00001) compared with the left lung. In the right lung, the centrodorsal lung area was the most ventilated, whereas, in the left lung, it was the centroventral area. Tidal impedance changes, serving as a surrogate for tidal volume, increased in the first 3 weeks of life (p < 0.00001). This study shows the dynamic changes in lung ventilation in the bovine neonate according to EIT measurements. The findings form a basis for the recognition of structural and functional lung disorders in neonatal calves.

Evaluation of impulse oscillometry in pigs of unknown disease status originating from the field

The aim of this study was to assess impulse oscillometry as a method to characterise lung function in 58 German hybrid pigs from 29 different herds of unknown respiratory status. The variability of repeated lung function measurements increased significantly after the sixth run and therefore the average of the first six runs was used for analysis. The presence of peripheral respiratory alterations in some pigs was indicated by the negative frequency dependence of the 95th percentile of respiratory resistance (Rrs), with highest values at 3 Hz and the sharp drop of respiratory reactance (Xrs) across the whole frequency range (3-15 Hz). Respiratory resistance and reactance were negatively correlated. Reactance area was correlated with (1) Rrs at 3, 5 and 10 Hz; (2) Xrs at 3, 5, 10 and 15 Hz; (3) the frequency dependence of resistance compared between 3 and 5 Hz (R3-R5), 5 and 10 Hz (R5-R10), and 5 and 15 Hz (R5-R15); and (4) tidal volume. High repeatability and low intra-individual variability of impulse oscillometry indicate that this method is a promising tool for advanced characterisation of the pulmonary system of pigs and has potential for use for herd health monitoring.

Why Do So Many Calves Die on Modern Dairy Farms and What Can We Do about Calf Welfare in the Future?

Poor bovine neonatal survival rates are an international animal welfare issue. The key modifiable risk factors associated with such loss are age at first calving in primiparae, calf breed, gender and gestation length and calving management. The primary causes of mortality in the perinatal period are calving problems, in particular dystocia, defined as both difficult and abnormal calvings. Calf loss rates are rising on modern dairy farms in many countries internationally. High calf loss rates are often not recognised at national or at farm-level; recording needs to be improved. Improving bovine neonatal survival requires re-prioritization of this issue. Stakeholders need to be made cognisant of this prioritization. Actions to effect change need to occur at both national and farm-levels. National-level actions need firstly to address raising awareness of the issue. Farm-level actions need to focus on identifiable problem farms through targeted surveillance. Application of existing knowledge to alter modifiable risk factors is the key to improving calf welfare in the future. Research also has a role to play in filling knowledge gaps in particular about the 'unexplained stillbirth'.

Computer Tomographic Illustration of the Development of the Pulmonary Function in Bovine Neonates until the Twenty-First Day Postnatum

The aim of this study was to analyze the development of the lung in newborn calves. The sample consisted of 28 Holstein Friesians calves which were examined clinically, and their chest segment was measured with computed tomography. The tests were performed on the first, sixth, and twelfth hours of life and after the first, second, and third weeks. Also, blood gases and blood counts were determined. Besides Kolmogorov-Smirnov tests, analyses of variance, t-tests (on a significance level of P < 0.05), and correlation analyses were used. The most significant changes occurred between birth and the first hour. However, there were significant differences in the gas filling between cranial and caudal and between dorsal and ventral parenchyma segments. This difference remained over the entire study period. At the end of the first week between 85 and 93% were involved in gas exchange. Only after the completion of the second week of life, the air supply was achieved throughout the whole lung. The pO2, pCO2, and pH values confirmed this. This study shows that a healthy bovine neonate needs about 2 weeks before all lung units are integrated into the gas exchange. This explains why calves in unfavorable environments often suffer from pulmonary affections.

Measurement of respiratory function by impulse oscillometry in horses

REASONS FOR PERFORMING STUDY

Due to technical implementations and lack of sensitivity, pulmonary function tests are seldom used in clinical practice. Impulse oscillometry (IOS) could represent an alternative method.

OBJECTIVES

To define feasibility, methodology and repeatability of IOS, a forced oscillation technique that measures respiratory resistance (Rrs) and reactance (Xrs) from 5 to 35 Hz during spontaneous breathing, in horses.

METHODS

Using 38 healthy horses, Rrs and Xrs reference values were defined and influence of individual biometrical parameters was investigated. In addition, IOS measurements of 6 horses showing clinical signs of heaves were compared to those of 6 healthy horses.

RESULTS

Airtightness and minimal dead space in the facemask were prerequisites to IOS testing and standardisation of head position was necessary to avoid variations in Rrs due to modified upper airway geometry. In both healthy and diseased animals, measurements were repeatable. In standard-type breeds, the influence of the horse's size on IOS parameters was negligible. An increase in R5Hz greater than 0.10 kPa/l/sec and R5Hz>R10Hz, combined with negative values of Xrs between 5 and 20 Hz, was indicative of heaves crisis.

CONCLUSIONS

IOS is a quick, minimally invasive and informative method for pulmonary function testing in healthy and diseased horses.

POTENTIAL RELEVANCE

IOS is a promising method for routine and/or field respiratory clinical testing in the equine species.

The use of impulse oscillometry for separate analysis of inspiratory and expiratory impedance parameters in horses: effects of sedation with xylazine

AIM

To improve the outcome of parameters measured by the impulse oscillometry system (IOS) in horses by separate assessment of inspiratory and expiratory impedance spectra in the frequency range between 1 and 10 Hz. As basis for further studies, the influence of sedation with xylazine on respiratory impedance was also investigated.

METHODS

(i) The respiratory impedance of 11 horses was measured using IOS before and 6 min after sedation (xylazine; 0.6 mg/kg b.w.). (ii) The time course of impedance parameters in a period of 24 min after administration of xylazine was evaluated in 12 horses at regular intervals of 3 min. Resistance (R(rs)), reactance (X(rs)), and coherence (Co) were calculated as mean spectra (R(rs),X(rs),Co) of the entire measurement as well as separated into inspiration (Ri(rs),Xi(rs),Coi) and expiration (Re(rs),Xe(rs),Coe) at frequencies of 1, 5, and 10 Hz.

RESULTS

(i) R(rs), X(rs) as well as Re(rs) and Xe(rs) revealed no significant influence of sedation. However, separate analysis of inspiration and expiration revealed a significant influence of sedation on all inspiratory impedance parameters. (ii) During the 24 min period after sedation, almost all inspiratory parameters were found significantly dependent on the time course of sedation whereas expiratory parameters Re10, Xe1, and Xe5 were not influenced. These results indicate that confounding factors due to sedation act mainly during inspiration. Muscle relaxation in upper airways due to xylazine is suspected to be the main cause of these phenomena.

Comparative evaluation of ultrasonography and lung function testing with the clinical signs and pathology of calves inoculated experimentally with Pasteurella multocida

Seventeen calves were inoculated intratracheally with Pasteurella multocida 0 on three consecutive days with 10 ml of an inoculum containing 10(9) colony forming units/ml per day per calf. Before the first inoculation and 24 hours after the third, each calf was examined non-invasively by means of a clinical examination, chest ultrasonography, and impulse oscillometry to measure the impedance of the respiratory system. The inoculation of P multocida caused fever and a significant increase in respiratory rate and a decrease in tidal volume. There were also significant changes in the ultrasonographic results and in the impedance of the respiratory system. The percentage of the total surface area of the lungs showing pathological changes when the calves were euthanased 48 hours after the third inoculation ranged from 0.4 to 39 per cent. There were statistically significant correlations between the ultrasound scores and the pathological findings and between the ultrasound scores and the respiratory rate and tidal volume. The changes in the impedance of the respiratory system were not correlated with either the ultrasonographic or the pathological findings.

Effect of three resuscitation procedures on respiratory and metabolic adaptation to extra uterine life in newborn calves

The purpose of this study was to evaluate the effects of three resuscitation procedures on respiratory and metabolic adaptation to extra-uterine life during the first 24 h after birth in healthy newborn calves. Twenty-four newborn calves were randomly grouped into four categories: six calves did not receive any specific resuscitation procedure and were considered as controls (C); six received pharyngeal and nasal suctioning immediately after birth by use of a hand-powered vacuum pump (SUC); six received five litres of cold water poured over their heads immediately after birth (CW) and six were housed in a calf pen with an infrared radiant heater for 24 h after birth (IR). Calves were examined at birth, 5, 15, 30, 45 and 60 min, 2, 3, 6, 12 and 24 h after birth and the following measurements were recorded: physical and clinical examination, arterial blood gas analysis, pulmonary function tests using the oesophageal balloon catheter technique, arterial and venous blood acid-base balance analysis, jugular venous blood sampling for determination of metabolic, haematological and passive immune transfer variables. SUC was accompanied by improved pulmonary function efficiency and by a less pronounced decrease in body temperature. The "head shaking movement" and the subsequent temporary increase in total pulmonary resistance as well as the greater lactic acidosis due to CW were accompanied by more efficient, but statistically non-significant, pulmonary gas exchanges. IR allowed maintenance of higher body temperature without requiring increased catabolism of energetic stores. IR also caused a change in breathing pattern which contributed to better distribution of the ventilation and to slightly improved gas exchange. The results indicate that use of SUC, CW and IR modified respiratory and metabolic adaptation during the first 24 h after birth without side-effects. These resuscitation procedures should be recommended for their specific indication, i.e. cleansing of fetal fluid from upper airways, hypothermal stimulation of breathing and prevention of heat losses.