Of the inhalation sedation techniques available, the following is the easiest, the most
flexible, and the least likely to cause surgery pollution. The control unit for the
Quantiflex MDM (Fig. 4.3) has a single control for the total flow of gases (Fig. 4.3
'1'), and a central, vertically placed, dial is turned to regulate simultaneously the
percentage flow of both gases (Fig. 4.3 '2'). Either of these controls can be changed
without altering the other. The actual percentage of gases being delivered is
monitored by observing the flow meters for oxygen and nitrous oxide, respectively
(Fig. 4.3: '3' & '4'). There are 15 steps for the technique:
- Check the machine.
- Select the appropriate size of nasal mask and clean it with alcohol.
- Connect up the scavenging pipe.
- Set the mixture dial to 100% oxygen. (Fig. 4.3 '2')
- Settle the patient in the dental chair.
- Turn the flow control (Fig. 4.3 '1') to 3 l/min and allow the reservoir bag to fill with
oxygen. - With the patient's help, position the nasal mask gently and comfortably to preclude
any leaks. If necessary explain the way the mask is used. - Turn the flow control knob to the left until the flow rate of oxygen (l/min) matches
the patient's tidal volume. This can be monitored by watching the reservoir bag, and
should take 15-20 s. When the patient inspires, the reservoir bag gets smaller. When
the patient breathes out the reservoir bag gets larger as it fills with the mixture of
gases emanating from the machine. - Simultaneously, reassure the patient about the sensations that will be felt.
Encourage the patient to concentrate on breathing gently through the nose. If the
reservoir bag appears to be getting too empty then the flow of oxygen should be
increased until the flow rate in l/min matches the patient's minute volume. - Turn the mixture dial vertically to 90% oxygen (10% nitrous oxide) (Fig. 4.3 '2').
Wait for 60 s. - Turn the mixture dial to 80% oxygen (20% nitrous oxide) (Fig. 4.3 '2'). Wait 60 s,
above this level the operator should exercise more caution and consider whether
further increments should be only 5%. With experience, operators will be able to
judge whether further increments are needed. - At the appropriate level of sedation dental treatment can be started.
- To bring about recovery turn the mixture dial to 100% oxygen and oxygenate the
patient for 2 min before removing the nasal mask. - Turn the flow control to zero and switch off the machine.