There are several reasons why the water may not bubble when the prongs are in the patient’s nose.
First, check the size of the prongs to make sure that the prongs completely fill the patient’s nostrils. If necessary, replace the prongs with the next largest prong size and make sure the prongs now completely fill the nostrils.
Second, make sure that the patient’s mouth is closed, so that the pressurized air isn’t lost out of the patient’s mouth. You can gently close the patient’s mouth, and encourage other caregivers/parents to monitor the patient’s mouth to make sure it stays closed.
Third, make sure all of the tubing is properly connected, including the bottle tubing, patient tubing, and any oxygen tubing. Make sure the fish elbows, nasal prongs, and end cap are securely connected. If you notice any loose connections, re-connect them and check for bubbling.
If none of the above steps generate bubbling, you may need to slightly increase the total flow to the patient. Larger/older patients with larger lungs may require a higher total flow to maintain the pressure in the system. You can increase the flow 0.5 L/min and see if the bubbling appears when the prongs are in the patient’s nose. If you don’t see bubbling, increase the total flow another 0.5 L/min. Be sure to increase the oxygen flow as well, if required. See Appendix A: Oxygen Blending Table on pg. 51 in the User & Repair Manual for details on oxygen flow and total flow settings.