DEMONSTRATION OF APNEA, DYSPNEA, AND ASPHYXIA 333 



ii. Demonstration of Apnea, Dyspnea, and Asphyxia. Produce 

 deep anesthesia, then disconnect the ether bottle and connect the tracheal 

 tube with a hand bellows. Produce deep and forced artificial respiration 

 for ten to twenty seconds. Stop artificial respiration; the animal will 

 remain quiet and without any effort at breathing. This is the condition 

 of apnea. Allow the animal to recover its normal respiratory rate and 

 again produce deep anesthesia. Now clamp off the tracheal tube so that 

 the animal can no longer receive air and leave it so until death. As the 

 blood becomes more and more venous there will first be a marked increase 

 in the respiration rate and depth. This is known as hyperpnea. This 

 stage is followed by one of increasing respiratory amplitude in which the 

 accessory respiratory muscles not previously active are brought into 

 forcible contractions, both inspiratory and expiratory phases are now 

 forced, dyspnea. The movements continue to increase, and the muscles 

 of the neck, larynx, mouth, and nostrils now take part. There is a 

 rather sudden decrease in the respiratory movements, an extension of the 

 limbs, and gasping movements, after which the animal remains quiet, 

 death being produced by asphyxia. 



12. Respiratory Exchange and Calorimetry. Indirect calorimetry is 

 made the basis for determining the metabolic rate in man and mammals. 

 Measurement of the oxygen intake and of the carbondioxide output under 

 standard conditions suffices for the computation from the data of the 

 metabolic rate of heat production per kilo or per square meter of surface 

 per hour. This principle is used in the rapid methods of human clinical 

 calorimetry. 



Generally a man is made to exhale into a large collecting chamber 

 (Tissot apparatus), or breathe through a closed chamber (rebreather) 

 provided with absorbers and either one-way valves or a pump to circulate 

 the air of the chamber. 



In man the test is made with the body at maximum rest. Test (i) 

 after a 12 hour fast; (2) measure the height in centimeters and weight 

 in kilos; (3) provide 20 to 30 minutes complete relaxation lying at rest; 

 (4) measure systolic and diastolic blood pressures and mouth tempera- 

 ture after the rest period; (5) Adjust the face mask and run the test of 

 oxygen consumption. Use a modified Henderson rebreather or a Bene- 

 dict filled with excess of pure oxygen, or a Tissot apparatus. Continue 

 the test for ten minutes or more. In the dog use a rebreather type of 

 apparatus of adapted size. Attach a face mask to a ten kilo dog trained 

 to the experiment. Record all rebreather movements. 



From the data for man, compute the metabolic rate per square meter 

 per hour for man by DuBois' formula. 



In man the surface area in sq. cm. = The Weight in kilos - 425 X the 

 Height in cm. - 725 X a constant 71.84. 



