J . small Anim.Pract. (1977) 18, 535-541.
Blood oxygen and carbon dioxide tensions in normal dogs and in dogs with respiratory failure W. T . C L A R K , B. R. J O N E S
AND
J. C L A R K
Department of Veterinary Clinical Sciences, Massey University, Palmerston North, New Zealand
ABSTRACT Arterial blood samples were obtained from thirty normal conscious dogs breathing air. The mean values and standard deviations recorded were PaO, 101.3 f5.6 mmHg, PaCO, 34.013.9 mmHg, oxygen saturation 93.8 f 1-2%, oxygen content 19.3k 1.8 m1/100 ml. Ten dogs with respiratory problems were also examined and of these animals seven had lower than normal oxygen tensions while three had carbon dioxide levels higher than those found in healthy dogs. It was concluded that, in severe respiratory disease, measurement of arterial oxygen tension gives a useful assessment of respiratory failure in dogs. INTRODUCTION The usefulness of the measurement of arterial blood oxygen (Pao,) and carbon dioxide (Paco,) tensions has been established in the assessment of respiratory failure in man (Sykes, McNicol & Campbell, 1969). Nevertheless these measurements have not been widely utilized in the study of natural respiratory disease in dogs although they have been recorded while investigating experimentally induced changes in the canine respiratory tract (Gold et al., 1972). A range of normal values for oxygen and carbon dioxide tensions in arterial blood obtained from healthy, conscious dogs breathing air have been reported by Feigl & D’Alecy (1972), Wise (1973) and Mohammed (1974). There are differences in the results obtained by these authors, possibly due to the methods by which the blood samples were obtained, so in the first part of the present study values for blood from healthy animals were established using samples collected under conditions which occur in clinical practice. 535
536
W . T . C L A R K , B . R . JONES A N D J . CLARK
The second part of the study evaluated the usefulness of blood gas tension measurements in detecting respiratory failure in dogs and recording progress during therapy. Oxygen and carbon dioxide tensions were measured in arterial blood samples obtained from dogs with respiratory problems and the results compared with the values for normal animals. MATERIALS A N D METHODS Thirty adult dogs, mainly of the Collie type, and including both sexes were used to establish normal values. The animals had been purchased for student classes and were free from clinical signs of respiratory disease. They ranged in weight from 11-8 to 27.7 kg. For the second part of the study blood samples were obtained from ten adult dogs presented at the Veterinary Faculty hospital with histories and clinical signs of dyspnoea. Dogs which had fasted for 20 hours were restrained in lateral recumbency without sedation and care was taken to prevent respiratory obstruction. Several dogs were excited and panted while restrained. Blood samples were obtained from the femoral artery using twenty-two gauge needles and glass syringes with the dead-space filled with heparin at a concentration of 5000 units per ml. Local analgesia was not employed as the dogs did not unduly resent arterial puncture when a sharp needle was used. The haemoglobin content of the blood was measured by the cyanmethaemoglobin method. Samples were stored at 4°C and analysed within 30 minutes using oxygen, carbon dioxide and pH electrodes. Separation of cells and plasma by sedimentation was not a problem but the syringes were rotated to ensure mixture of cells and plasma prior to measurement. The oxygen electrode was routinely calibrated using water equilibrated with room air. The difference in readings between water and blood at the same gas tension was determined and a correction applied to the oxygen values. Determinations of oxygen and carbon dioxide tensions in blood were reproducible to within 2 mm Hg. Measurements were made at 37°C and the results corrected in accordance with the rectal temperature of the dog at the time of sampling, using the correction factors published by Pickrell & Schluter (1973). These workers also published formulae which were used to calculate the oxygen content of the blood and the saturation of blood with oxygen. RESULTS The values obtained from healthy dogs are given in Table 1 and in Table 2 the Pao, and Pacoz levels are compared with those reported in the literature by earlier workers. In the present study the oxygen tensions were significantly higher than the levels recorded by Feigl & D’Alecy (1972) and by Wise (1973) but when they were compared with the values obtained by Mohammed (1974) the differences were not statistically significant. The carbon dioxide tensions were significantly
537
BLOOD GASES I N R E S P I R A T O R Y F A I L U R E
TABLE1. Values recorded in arterial blood samples from normal dogs
Pao2 o2 saturation o2 content
Pacol Haemoglobin Body temperature
n
Mean
s.d.
95% confidence limits
30 30 30 30 30 30
101.3 mmHg 93.8 % 19.3 ml/lOOml 34.0mmHg 15.1 g/lOOml 38.8 “C
5.6 1.2 1.8 3.9 1.5 0.8
89.9-1 12.7 91.3- 96.4 15.5- 23.0 26.0- 41.9
TABLE2. Comparison of normal values found in this study with those recorded by other workers
Present study Feigl & D’Alecy (1972) Wise (1973) Mohammed (1974) ~~
Mean Pao2
s.d.
Mean Paco2
s.d.
n
101.3 89.5* 90.9* 105.4
5.6 4.4 5.7 15.3
34.0 36.8* 35.9 34.3
3.9 2.4 2.4 4.3
30 30 11 50
~
*
Values statistically significantly different from the present study ( p
Blood oxygen and carbon dioxide tensions in normal dogs and in dogs with respiratory failure W. T . C L A R K , B. R. J O N E S
AND
J. C L A R K
Department of Veterinary Clinical Sciences, Massey University, Palmerston North, New Zealand
ABSTRACT Arterial blood samples were obtained from thirty normal conscious dogs breathing air. The mean values and standard deviations recorded were PaO, 101.3 f5.6 mmHg, PaCO, 34.013.9 mmHg, oxygen saturation 93.8 f 1-2%, oxygen content 19.3k 1.8 m1/100 ml. Ten dogs with respiratory problems were also examined and of these animals seven had lower than normal oxygen tensions while three had carbon dioxide levels higher than those found in healthy dogs. It was concluded that, in severe respiratory disease, measurement of arterial oxygen tension gives a useful assessment of respiratory failure in dogs. INTRODUCTION The usefulness of the measurement of arterial blood oxygen (Pao,) and carbon dioxide (Paco,) tensions has been established in the assessment of respiratory failure in man (Sykes, McNicol & Campbell, 1969). Nevertheless these measurements have not been widely utilized in the study of natural respiratory disease in dogs although they have been recorded while investigating experimentally induced changes in the canine respiratory tract (Gold et al., 1972). A range of normal values for oxygen and carbon dioxide tensions in arterial blood obtained from healthy, conscious dogs breathing air have been reported by Feigl & D’Alecy (1972), Wise (1973) and Mohammed (1974). There are differences in the results obtained by these authors, possibly due to the methods by which the blood samples were obtained, so in the first part of the present study values for blood from healthy animals were established using samples collected under conditions which occur in clinical practice. 535
536
W . T . C L A R K , B . R . JONES A N D J . CLARK
The second part of the study evaluated the usefulness of blood gas tension measurements in detecting respiratory failure in dogs and recording progress during therapy. Oxygen and carbon dioxide tensions were measured in arterial blood samples obtained from dogs with respiratory problems and the results compared with the values for normal animals. MATERIALS A N D METHODS Thirty adult dogs, mainly of the Collie type, and including both sexes were used to establish normal values. The animals had been purchased for student classes and were free from clinical signs of respiratory disease. They ranged in weight from 11-8 to 27.7 kg. For the second part of the study blood samples were obtained from ten adult dogs presented at the Veterinary Faculty hospital with histories and clinical signs of dyspnoea. Dogs which had fasted for 20 hours were restrained in lateral recumbency without sedation and care was taken to prevent respiratory obstruction. Several dogs were excited and panted while restrained. Blood samples were obtained from the femoral artery using twenty-two gauge needles and glass syringes with the dead-space filled with heparin at a concentration of 5000 units per ml. Local analgesia was not employed as the dogs did not unduly resent arterial puncture when a sharp needle was used. The haemoglobin content of the blood was measured by the cyanmethaemoglobin method. Samples were stored at 4°C and analysed within 30 minutes using oxygen, carbon dioxide and pH electrodes. Separation of cells and plasma by sedimentation was not a problem but the syringes were rotated to ensure mixture of cells and plasma prior to measurement. The oxygen electrode was routinely calibrated using water equilibrated with room air. The difference in readings between water and blood at the same gas tension was determined and a correction applied to the oxygen values. Determinations of oxygen and carbon dioxide tensions in blood were reproducible to within 2 mm Hg. Measurements were made at 37°C and the results corrected in accordance with the rectal temperature of the dog at the time of sampling, using the correction factors published by Pickrell & Schluter (1973). These workers also published formulae which were used to calculate the oxygen content of the blood and the saturation of blood with oxygen. RESULTS The values obtained from healthy dogs are given in Table 1 and in Table 2 the Pao, and Pacoz levels are compared with those reported in the literature by earlier workers. In the present study the oxygen tensions were significantly higher than the levels recorded by Feigl & D’Alecy (1972) and by Wise (1973) but when they were compared with the values obtained by Mohammed (1974) the differences were not statistically significant. The carbon dioxide tensions were significantly
537
BLOOD GASES I N R E S P I R A T O R Y F A I L U R E
TABLE1. Values recorded in arterial blood samples from normal dogs
Pao2 o2 saturation o2 content
Pacol Haemoglobin Body temperature
n
Mean
s.d.
95% confidence limits
30 30 30 30 30 30
101.3 mmHg 93.8 % 19.3 ml/lOOml 34.0mmHg 15.1 g/lOOml 38.8 “C
5.6 1.2 1.8 3.9 1.5 0.8
89.9-1 12.7 91.3- 96.4 15.5- 23.0 26.0- 41.9
TABLE2. Comparison of normal values found in this study with those recorded by other workers
Present study Feigl & D’Alecy (1972) Wise (1973) Mohammed (1974) ~~
Mean Pao2
s.d.
Mean Paco2
s.d.
n
101.3 89.5* 90.9* 105.4
5.6 4.4 5.7 15.3
34.0 36.8* 35.9 34.3
3.9 2.4 2.4 4.3
30 30 11 50
~
*
Values statistically significantly different from the present study ( p
