Respiratory Monitoring Practices During Procedural Sedation and Analgesia in the Cardiac Catheterisation Lab Could Be Enhanced by Using Capnography to Assess Ventilation
Conway, Aaron W.
Rolley, John X.
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Purpose: Capnography is very effective in detecting depressed respiration during procedural sedation and analgesia (PSA) of non-ventilated patients. However, nurses do not routinely use this technology in the cardiac catheterisation lab (CCL). Accordingly, we sought to analyse current practices to ascertain the role that capnography may contribute to this setting. Methods: Retrospective medical record audit of procedures performed in the CCL of one private hospital in May and June 2010. Results: Nurses administered PSA during 154/397 (38.8%) procedures, consisting of: 53/211 (25.1%) coronary angiographies; 47/84 (56.0%) percutaneous coronary interventions; 7/15 (46.7%) electrophysiology study and radiofrequency ablations; 35/52 (%) cardiac pacemaker insertions; 8/16 (50%) implantable cardioverter defibrillator insertions; 1/2 (50%) cardiac resynchronisation therapy implants; 1/1 (100%) temporary pacing lead insertions; 1/1 (100%) structural heart procedures and 2/9 (22.2%) vascular procedures. Oxygen saturations were recorded during 140/154 (90.9%) procedures, while respiration rate was recorded in 16/154 (10.4%). It was documented that 36/154 (23.7%) patients received oxygen supplementation and 11/154 (7.1%; 95% CI=4.0%-12.3%) patients experienced a period of oxygen desaturation. Conclusion: Without concurrent observation of respiration, oxygen saturation monitoring will not detect respiratory depression because it measures oxygenation not ventilation. This audit revealed that in many cases nurses did not record respiration observations, possibly due to surgical draping, which obscures their view of the patient. In addition, nurses need to maximise their distance from the radiation source. Capnography could overcome these barriers to ventilation assessment as its accurate measurement of exhaled carbon dioxide coupled with the easily interpretable waveform output it produces, which displays a breath-by-breath account of ventilation, enables identification of respiratory depression in real-time. Therefore, it is feasible that periods of oxygen desaturation could be prevented if capnography is used because interventions, such as administration of supplemental oxygen, could be initiated earlier in the course of respiratory depression.