November 1992, Volume 42, Issue 11

Original Article

OXYGEN DESATURATION DURING FIBEROPTIC BRONCHOSCOPY

Salahuddin Afsar  ( Department of Medicine, Dow Medical College and Civil Hospital, Karachi. )
Ali Nawaz Choudhri  ( Department of Medicine, Dow Medical College and Civil Hospital, Karachi. )
Abu Talib  ( Department of Medicine, Dow Medical College and Civil Hospital, Karachi. )
Tariq Farooqi  ( Department of Medicine, Dow Medical College and Civil Hospital, Karachi. )
Mohammed Javed Pasha  ( Department of Medicine, Dow Medical College and Civil Hospital, Karachi. )

ABSTRACT

Aprospective study was performed to detectoxygen saturation (Sa02) during and following fiberoptic bronchoscopy (FOB) in 50 patients. Twenty-five patients (group 1) underwent the procedure without and 25 (group 2) with supplemental oxygen. The SaO2 declined from the baseline value of 96.4% to 92.08% in group 1 and to 94.88% in group 2 after bronchoscopy alone. The decline was also noted when biopsy and broncho-alveolar lavage (BAL) were performed, the lowest values being recorded during BAL. The result showed that the fall in Sa02 in group 2 was significantly less than that in group 1 (P <0.05). SaO2 returned to baseline values after a mean time of 4.9 minutes in group 1 and 2.4 minutes in group 2, demonstrating the benefit of supplemental oxygen (JPMA 42: 263, 1992).

INTRODUCTION

Since its introduction by Ikeda in 19681, flexible fiberoptic bronchoscopy has been used extensively by respiratory physicians for diagnostic and therapeutic purposes2,3. FOB also has its hazards, the most common complications described include adverse reactions to the medications used for sedation or topical anaesthesia, local trauma to airways, haemorrhage, pneumothorax, bronchospasm, laryngospasm, cardiac dysrrhythmias and hypoxemia4-6. This study was done to determine the degree and duration of hypoxemia during bronchoscopy alone, during bronchial/transbronchial biopsies and bronchoalveolar lavage. The effects of supplemental oxygen during these procedures was also assessed.

MATERIALS AND METHODS

Fifty patients (45 males, 5 females) with various indications for diagnostic FOB were studied. Their ages ranged from 20-8Oyears (mean 53.3 years). Premedication was limited to atropine sulfate 0.5 mg intramuscularly given 30 minutes prior to procedure. Posterior pharynx and epiglottis were anaesthetized topically by spraying 2% lignocaine. A fiberoptic bronchoscope was introduced per orally and vocal cords, tracheaand airways anaesthetized (2% lignocaine) under direct vision; the patient being kept in supine position. Microspan 3040 pulse oximeter was applied to the index finger of the right hand and baseline SaO2 was recorded. Half the patients were assigned to receive supplemental oxygen (group 2) through a nasal cannula at a rate of 5L/min. Rest of the patients (group 1) were not given supplemental oxygen. The SaO2 was continuously monitored during the procedure and lowest readings were recorded during bronchoscopy. Bronchial biopsy was taken from 26 (group 1 = 14, group 2 = 12) and BAL was performed in 19 patients (group 1 = 10, group 2 = 19). After the procedures monitoring of SaO2 was continued till it returned to baseline levels.

RESULTS

Changes In oxygen saturation during fiberoptic bronchoscopy
Baseline arterial haemoglobin saturation (SaO2) in all 50 patients studied ranged from 84-98% (mean 96.4%, SD± 3.04). The changes which occurred in SaO2 during different procedures were as follows:
Bronchoscopy alone
Mean oxygen saturation in group 1 dropped to 92.08% (SD±3.8) and in group 2 to 94.88% (SD±3.25), Pc 0.05 (Figure 1).


Bronchoscopy and biopsy
Mean oxygen saturation in group 1 became 90. 46% (SD± 5.90), while in group 2 it was 92.88% (SD±6.13), P<0.05 (Figure 2).


Bronchoscopy with bronchoalveolar lavage
Mean oxygen saturation in group 1 fell to 90.2% (SD±6.62), while in group 2 it was 91.66% (SD± 5.12), PcO.05 (Figure 3).


Time taken for Sa02 to return to baseline values
After the FOB oxygen saturation in all patients returned to baseline values. Time taken in group 1 ranged from 1-32 minutes (mean 4.9 min) and in group 2, 0-14 minutes (mean 2.4 min).

DISCUSSION

This study shows that a decline in SaO2 is frequent­ly noted during FOB and this decline can be of a substantial degree and duration. However, the drop in SaO2 was reduced by the administration of supplemental oxygen. The drop in Sa02 reported by others7 has also been maximal in this study when bronchoscopy was associated with bronchial veolarlavage. In contrast Breuer et al8 did not find any significant change in oxygen saturation during different diagnostic procedures. In both studies supplemental oxygen was given. In this study the Sa02 returned to baseline within 32 minutes after completion of the procedure. This was to 30 minutes reported by others9,10. The decline in arterial P02 after FOB may be immediate11 or may range from one to more than four hours. The cause of hypoxemia during FOB is not clear. It could be reflex in nature. The subepithelial receptors in the trachea may be affected by mechanical stimulation of the instrument resulting in bronchoconstriction with a consequent mismatch of ventilation and perfusion11. The procedure may induce modest intrapulmonary shunt and zones of low ventilation:perfusion ratio due to loss of lavage fluid and bronchospasm by tracheal stimulation during the procedure1. Other causes include prolonged suction9 and haemorrhage from the biopsy site12. Hypoxemia can also be worsened if the patients are oversedated especially by opiates5,13,14. Hypoxia occur­ring due to any cause leads to its complications, car­diovascular rhythm disturbances being a major risk Many studies have documented a correlation between hypoxemia and dysrrhythmias15,16. The measurement of SaO2 rather than of Pa02 was obtained in this study. The rapid response time (2-3 sec) and self calibration make the pulse oximeter an efficient and accurate non-invasive monitoring device9. Fanconi et al17 reported pulse oximetry as a reliable technique for monitoring oxygenation. On the basis of the results of this study when performing FOB, pulse oximetry should be a routine, supplemental oxygen should be given to all patients and facilities for cardio-respiratory resuscitation should be at hand.

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