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_
Capnometry during High-Frequency Oscillatory Ventilation· . Masaji Nishimura, M.D.; Hideaki lmanaka, M.D.; Chikara Tashiro, Nobuyuki Taenaka, M.D.; and lkuto ¥os!liya, M.D.
~/.D.;
We used capnometry during high-frequency oscillatory ventilation (HFOV), and compared COl measurements at the distal and proximal ends of an endotracheal tube with arterial COl values. Ten white rabbits (mean weight, 2.00±O.2 [SD] kg) underwent tracheostomy under anesthesia with pentobarbital. The trachea was intubated with an endotracheal tube with a second lumen for sampling respiratory gas at the distal tip. Capnometry was performed through the lumen (COld) and the proximal end of the endotracheal tube (C0sP). The internal carotid artery was cannulated to sample blood for measuring arterial blood
gases. The differences between COld, COlp, and PaCOI were measured. Ooly the relation between COld and PaCO. was good (r=O.915). We concluded that capnometry can be used during HFOV to estimate PaCOs provided that respiratory gas is sampled from the distal tip of the endotracheal tube. (Chest 1992; 101:1681-83)
Capnometry and pulse oximetry are rapidly becom-I ing standard procedures in monitoring critically ill children. Capnometry provides a measurement of the CO2 concentration in the patient's respiratory gas. However, its use during high-frequency oscillatory ventilation (HFOV) has never been reported. In the present study, we used capnometry during HFO~ and determined the relationships between the CO2 concentration at the distal end of an endotracheal tube (C02d), the CO2 concentration at the proximal end of an endotracheal tube (C02P), and PaC02 •
METHODS
=
CO.d CO. concentration at the distal end of the endotracheal tube; COd» CO. concentration at the proximal end of the endotracheal tube; HFOV = high-frequency oscillatory ventilation; r-CO. CO. concentration of respiratory gas
*From the Department of Anesthesiology, Osaka Medical Center and Researcli Institute for Maternal and Child Health (Drs Nishimura and Tashiro), and the Intensive Care Unit, Osaka University Hospital (Drs Imanaka, Taenaka, and Yoshiya), Osaka, Japan. Reprint requests: Dr. Nishimura, De]J!Jrlment of Anesthesiology, Osaka Institute for ~Iatemal and Child Health, Osaka, japan 59002
(
= =
The experiment was performed on ten white rabbits weighing 1.16 to 2.21 kg (mean, 2.0±O.2 [SD] kg). The rabbits were anesthetized with intravenous pentobarbital, with supplemental doses as needed to suppress the corneal reHex. After tracheostonlY, the animals were intubated with a 4-mm-internal-diameter tracheal tube with a second lumen for sampling respiratory gas (Mallinckrodt, Glens Falls, NY). The distal tip of the tube was positioned just above the carina under x-ray guidance. The internal carotid artery was cannulated for samplin~ blood to analyze PaC02 • The analysis was performed with an ABL2 blood gas analyzer (Radiometer, Copenhagen). The rabbit's lungs were ventilated by using the HFOV mode of a IIummingbird B~tO 20N olechanical ventilator (~tera, lhkyo). The operating L'Onditions were set as follows: stroke volunle, 4, 6, 8, 10, and 12 ml; frequency, 15 cyclesls; inspiration-expiration ratio, 1: 1; mean airway pressure, 3 cm H 20; fresh gas flow rate, 1 or 2 Umin. At each setting, the PaC02 and the CO2 concentration of the respiratory gas (r-COJ were oleasured simultaneously. The respiratory gas was sampled through the second lumen of the tracheal tube from just above the carina (r-C02d) and from the proximal end
IHummingbird
"--------........
SMO 20N
Nellcor N-1000 Three - way stopcocks
FIGURE 1. Experimental schema. Rabbits underwent tracheostomy and intubation with an endotrclcheal tube with a se
_
Capnometry during High-Frequency Oscillatory Ventilation· . Masaji Nishimura, M.D.; Hideaki lmanaka, M.D.; Chikara Tashiro, Nobuyuki Taenaka, M.D.; and lkuto ¥os!liya, M.D.
~/.D.;
We used capnometry during high-frequency oscillatory ventilation (HFOV), and compared COl measurements at the distal and proximal ends of an endotracheal tube with arterial COl values. Ten white rabbits (mean weight, 2.00±O.2 [SD] kg) underwent tracheostomy under anesthesia with pentobarbital. The trachea was intubated with an endotracheal tube with a second lumen for sampling respiratory gas at the distal tip. Capnometry was performed through the lumen (COld) and the proximal end of the endotracheal tube (C0sP). The internal carotid artery was cannulated to sample blood for measuring arterial blood
gases. The differences between COld, COlp, and PaCOI were measured. Ooly the relation between COld and PaCO. was good (r=O.915). We concluded that capnometry can be used during HFOV to estimate PaCOs provided that respiratory gas is sampled from the distal tip of the endotracheal tube. (Chest 1992; 101:1681-83)
Capnometry and pulse oximetry are rapidly becom-I ing standard procedures in monitoring critically ill children. Capnometry provides a measurement of the CO2 concentration in the patient's respiratory gas. However, its use during high-frequency oscillatory ventilation (HFOV) has never been reported. In the present study, we used capnometry during HFO~ and determined the relationships between the CO2 concentration at the distal end of an endotracheal tube (C02d), the CO2 concentration at the proximal end of an endotracheal tube (C02P), and PaC02 •
METHODS
=
CO.d CO. concentration at the distal end of the endotracheal tube; COd» CO. concentration at the proximal end of the endotracheal tube; HFOV = high-frequency oscillatory ventilation; r-CO. CO. concentration of respiratory gas
*From the Department of Anesthesiology, Osaka Medical Center and Researcli Institute for Maternal and Child Health (Drs Nishimura and Tashiro), and the Intensive Care Unit, Osaka University Hospital (Drs Imanaka, Taenaka, and Yoshiya), Osaka, Japan. Reprint requests: Dr. Nishimura, De]J!Jrlment of Anesthesiology, Osaka Institute for ~Iatemal and Child Health, Osaka, japan 59002
(
= =
The experiment was performed on ten white rabbits weighing 1.16 to 2.21 kg (mean, 2.0±O.2 [SD] kg). The rabbits were anesthetized with intravenous pentobarbital, with supplemental doses as needed to suppress the corneal reHex. After tracheostonlY, the animals were intubated with a 4-mm-internal-diameter tracheal tube with a second lumen for sampling respiratory gas (Mallinckrodt, Glens Falls, NY). The distal tip of the tube was positioned just above the carina under x-ray guidance. The internal carotid artery was cannulated for samplin~ blood to analyze PaC02 • The analysis was performed with an ABL2 blood gas analyzer (Radiometer, Copenhagen). The rabbit's lungs were ventilated by using the HFOV mode of a IIummingbird B~tO 20N olechanical ventilator (~tera, lhkyo). The operating L'Onditions were set as follows: stroke volunle, 4, 6, 8, 10, and 12 ml; frequency, 15 cyclesls; inspiration-expiration ratio, 1: 1; mean airway pressure, 3 cm H 20; fresh gas flow rate, 1 or 2 Umin. At each setting, the PaC02 and the CO2 concentration of the respiratory gas (r-COJ were oleasured simultaneously. The respiratory gas was sampled through the second lumen of the tracheal tube from just above the carina (r-C02d) and from the proximal end
IHummingbird
"--------........
SMO 20N
Nellcor N-1000 Three - way stopcocks
FIGURE 1. Experimental schema. Rabbits underwent tracheostomy and intubation with an endotrclcheal tube with a se
