Oximetry is usually performed for patient monitoring during flexible bronchoscopy (FB) and medical thoracoscopy (MT). Monitoring of cutaneous carbon dioxide tension (PcCO2) may preceed severe hypoxemia by allowing intervention before the manifestation of severe hypoventilation. We examined the occurrence of hypoventilation during FB & MT by PcCO2 monitoring.
Following validation studies, PcCO2 was prospectively measured in 62 patients undergoing FB and 12 patients undergoing MT using a combined digital earlobe sensor measuring oxygen saturation (SpO2)(%) and PcCO2 (mm Hg) (Sentec, Therwil, Switzerland). All patients received supplemental oxygen.
Mean duration of FB was 17 minutes and MT was 47 minutes. Mean midazolam dose administered during FB was 0.07 mg/kg and MT was 5.4 mg. Mean baseline and peak PcCO2 levels during FB were 38 mm Hg and 49 mm Hg and MT were 38.8 mm Hg and 50.2 mm Hg respectively. Mean increases in PcCO2 during FB and MT were 11 mm Hg and 11.4 mm Hg respectively. Mean duration from baseline to peak PcCO2 was 14 minutes for FB and 35 minutes for MT. During FB, 15 patients had SpO2 drop to ≤ 90%. In 14 patients the SpO2 increased to > 90% with jaw support and in one patient a nasopharyngeal tube was inserted. Mean increase in PcCO2 in patients who did and did not manifest a lowest SpO2 ≤ 90% during FB was 14.2 mm Hg and 9.5 mm Hg respectively (p<0.05). Mean fall in SpO2 during FB and MT was 4% and 5.2% respectively. During FB excessive coughing led to a transient artifactual decrease in pulse rate often accompanied by an artifactual drop in SpO2 whilst PcCO2 remained unchanged.
Combined and continuous PcCO2 and SpO2 measurement permits monitoring of ventilation during FB and MT.
Monitoring of ventilation during FB & MT may allow to better guide the administration of sedation and thus might improve patient safety.
P.N. Chhajed, None.