I

CUNICAL INVESTIGATIONS

Ventilation-Perfusion Alterations Induced by Fiberoptic Bronchoscopy* Bernard B. Brach, M.D.; 00 German G. Escano, M.D.; ]ames H. Harrell, M.D., F.C.C.P.; and Kenneth M. Moser, M.D., F.C.C.P.

Pulmonary perfusion (Q) and ventilation (V) scintiphotography was performed in 16 patients undergoing diagnostic fiberoptic bronchoscopic examinations. Regional VI Q did not change in the majority of the patients who developed hypoxemia after bronchoscopic studies. An improvement In VI Q was detectable In the patients with a rise in arterial oxygen pressure (Pa02) after bronchoscopic examination, and this rise was associated in most

Jn patients who undergo fiberoptic bronchoscopic

examination, a significant decrease in arterial has been documented, oxygen pressure (Pa~) which may persist for several hours. 1 Although simple methods for resolving this hypoxemia have been described, 2•3 the mechanisms responsible for this decline have not been elucidated. Severe bronchospasm inducing acute hypercapnia has been observed occasionally, 2 but this sequence is absent in the vast majority of patients. Lavage during fiberoptic bronchoscopic examination has been incriminated by some as a major determinant of hypoxemia;3 however, lavage-induced removal of mucous plugs from regional airways also has been associated with a rise in Pa02 after fiberoptic bronchoscopic studies.4 Thus, evidence to date has suggested that alterations in gas exchange after fiberoptic bronchoscopic examination are related to favorable or unfavorable modification in the relationships of ventilation ( V) to perfusion ( Q). In patients undergoing diagnostic fiberoptic bronchoscopic evaluation, we performed sequential pulmonary V.and Q scintiphotography with a scintilla°F ·'>m the Pulmonary Division, Deparbnent of Medicine, University of California School of Medicine, San Diego. Supported in part by Pulmonary SCOR grant HL-14169 from the National Heart and Lung Institute. 00 National Institutes of Health Postdoctoral Trainee in Pulmonary Disease Research (PHS HL00134). Manuscript received June 9; revision accepted September 29. Reprint requests: Dr. Moser, University Hospital, 225 West Dickinson, San Diego 92103

CHEST, 69: 3, MARCH, 1976

with the removal of mucous plugs or extensive secretions. The data indicate that the behavior of Pa02 after bronchoscopic study is dependent upon both the extent of lavage and the yield of the procedure in terms of secretions and plugs. The results also indicate that the removal of secretions or plugs can be associated with rapid return of regional V and Q.

tion camera, and arterial blood gas analyses in order to determine ( 1) whether the behavior of Pa~ after fiberoptic bronchoscopic studies could be related to regional. VI Q alterations detectable by the scintillation camera, and ( 2) the stability of VI Q patterns following this intervention. METHODS

Sixteen patients undergoing diagnostic fiberoptic bronchoscopic studies for a mass ( five patients), infiltrate ( six patients), nodule (three patients ) , atelectasis (one patient), and cavity (one patient) were selected for study. Prior to fiberoptic bronchoscopic examination, pulmonary Q and V scintiphotography was performed with a scintillation earner~ using 0.2 millicuries of intravenously injected wmtechnetiumlabelled albumin macroaggregates for the former and inhaled I33xenon for the latter. Following scintiphotography, an arterial blood sample was obtained while the patient was breathing room air. Each patient was then prepared with an intramuscular injection of 0.5 mg of atropine and tracheal instillation of 15 ml of a 0.45 percent solution of tetracaine. Oxygen was supplied to some patients by the modified Ventimask method described by Albertini et al.2 The bronchoscope was introduced transnasally. Segmental lavage with 30 to 50 ml of physiologic saline solution was performed in all patients, except one who received a 250 mllavage. Immediately after bronchoscopic examination, a repeat intravenous injection of 3.0 millicuries of 99mtechnetiumlabelled albumin macroaggregates was given, and the patient was placed on room air. Perfusion and ventilation scintiphotography was repeated, and an arterial blood sample was obtained within 10 to 15 minutes after fiberoptic bronchoscopic studies, just prior to scintiphotography. Ventilation and perfusion scintiphotographs were reviewed

FIBEROPTIC BRONCHOSCOPY-INDUCED VENTILATION-PERFUSION ALTERATIONS 335

PRE

Ventilation

POST

FIGURE 1. Ventilation and perfusion (posterior view) scintiphotoscans in same patient before (upper scans) and after (l()wer scans) fiberoptic bronchoscopic examination. Improvement is noted in right lower lobar disbibution of both V and

have improved gas exchange, namely, restoration of a more normal VIQ match in previously abnormal zones (Fig 1). Five of these six patients showed an increase in Pa02 after fiberoptic bronchoscopic studies (Table 1). The sixth patient showed an increase in Pa02 at two hours after fiberoptic bronchoscopic examination. The increment in Pa02 after fiberoptic bronchoscopic studies in group 1 averaged 7.0 + 8.4 mm Hg ( SD), while the alveolar-arterial oxygen pressure difference (P[A-a]02) decreased by 7.7 ± 2.4 mm Hg (SD) . Both changes were significant ( P < 0.01 ) . In four ·of these six patients, the bronchoscopist specifically noted removal of mucous plugs or thick secretions. The ten patients in group 2 showed either no change in VI Q pattern after fiberoptic bronchoscopic studies (nine patients) or the creation of a low VI Q zone (one patient) . All patients in group 2 showed a decrease in Pa02 after bronchoscopic examination. The mean decrement in Pa02 was 6.8 ± 5.4 mm Hg ( SD), a difference significant at the level of P < 0.01. All patients also showed an increase in their P(A-a)~ (mean, 7.7 ± 5.5 mm Hg [SD]). In none of these patients was the removal of mucous plugs or extensive secretions noted by the bronchoscopist. The one patient in whom a low VI Q

Q.

by two observers who had not participated in the fiberoptic bronchoscopic examination and were not aware of the arterial blood gas changes. Scintiphotographs were graded as unchanged, improved (restoration of more favorable V/Q relationships), or worse (creation of new low V /Q zones) . REsULTS

Analysis of the V and Q scintiphotographs disclosed that six patients (group 1) demonstrated a change in regional VI Q relationships which should Table I -Blood Ga. Meaurement• be/ore and a/ler Fiberoptic Broru:lw.eopk Studie• *

PaOz

PaCOt

P(A-a)Ot

Group 1 Before After Change

62.5 69.5 7.0

± ± ±

10.0 16.8 8.4

34.8 34.8 0

± 3.1 ± 4.8 ± 6.7

52.0 44.3 -7.7

± ± ±

13.0 12.2 2.4

Group 2 Before After Change

78.7 71.9 -6.8

± ± ±

11.7 4.8 5.4

35.6 33.9 1.7

±

± 2.3

35.8 43.5 7.7

± ± ±

12.3 12.3 5.5

±

2.9 1.6

*Table values are means ± SD. Group 1, six patients with change in regional V/Q relationships which should have improved gas exchange after fiberoptic bronchoscopic study; and group 2, ten patients with either no change in V/Q pattern or creation of low V/Q zone after bronchoscopic study.

33& BRACH ET AL

Perfusion

PRE

Ventilation

"t • . t , ; ·~ .. . . • '

·

. .

POST

Fie HE 2. Ventilation and perfusion t posterior view ) scintiphotoscans in same patient before (upper scans) and after (lower scans) fiberoptic bronchoscopic examination. Decrement in V without alteration in Q, creating low VI Q zone, is demonstrated in medial aspect of right lower lobe.

CHEST, 69: 3, MARCH, 1976

zone appeared after fiberoptic bronchoscopic study was the patient who received the large ( 250 ml) lavage during the bronchoscopic procedure (Fig 2). This patient also had the greatest widening of P( Aa) 02 in the series ( 18 mm Hg). In neither group were significant alterations in arterial carbon dioxide tension ( PaC02) observed after fiberoptic bronchoscopic studies. DISCUSSION

Prior studies have suggested·that in the absence of changes in PaC02, the alterations in Pa02 after fiberoptic bronchoscopic examination were related to modification of regional VIQ relationships. Hypoxemia would result from induction of low VI Q zones. Such zones might result from obstruction of regional airways by lavage fluid3 or airway constriction related to vagal reflexes secondary to tracheal irritation. 5 The resultant decrease in regional V, unmatched by a similar reduction of the regional blood flow to affected lung units, would lead to hypoxemia. This is known to occur in experimentally induced pneumonia, 6 and we have shown it to occur after extensive lobar lavage via the fiberoptic bronchoscope (unpublished data). In this series, we were unable to visualize regional VIQ decrement by scintiphotography in nine of the ten patients who developed hypoxemia after bronchoscopic study. Only in one patient who received more extensive lavage was a low VI Q zone clearly identified after bronchoscopic examination. Thus, while VIQ alterations did occur, they could not be identified with scintiphotographic techniques. This is not surprising because detection with the scintillation camera requires substantial regional alterations in relatively large zones of lung. Whether lavage or airway constriction or both are the culprits remains unsettled; but it is clear that more extensive lavage induces more marked hypoxemia when all other elements in the procedure are the same. Somewhat surprising to us was the readily detectable improvement in regional VIQ which occurred immediately after fiberoptic bronchoscopic studies in the six patients in group 1. Such improvement correlated not only with a rise in Pa02 after

CHEST, 69: 3, MARCH, 1976

bronchoscopic examination in five of these six (and a delayed rise in the sixth) but also with notation of Significant removal of mucous plugs or secretions in four of them. Thus, whatever the hypoxemic potential of fiberoptic bronchoscopic examination per se, it is more than balanced when the procedure achieves substantial removal of plugs or secretions. This potential beneficial effect of removing secretions provides a valid indication for proceeding with a therapeutic fiberoptic bronchoscopic study in a severely hypoxemic patient who might otherwise be considered at hypoxemic hazard by the procedure; however, in hypoxemic candidates for diagnostic bronchoscopic study in whom secretion removal is not anticipated, the risk of worsening hypoxemia persists. 7 In a broader context, the results show that abrupt alterations in sequential Q scintiphotoscanning studies can occur with relief of bronchial obstruction. Restoration of Q has been considered a helpful sign in confirming the diagnosis of pulmonary embolism. 8 Our studies once again emphasize that pulmonary disorders other than embolism, including retention and clearance of secretions, can lead to abrupt decrement in or return of regional pulmo-

nary¢..

REFERENCES

1 Albertini R, Harrell JH, Moser KM: Hypoxemia during fiberoptic bronchoscopy. Chest 65:117, 1974 2 Albertini RE, Harrell JH, Moser KM: Management of arterial hypoxemia induced by fiberoptio bronchoscopy. Chest 67:134-135, 1975 3 Dubrawsky C, Awe RJ, Jenkins DE: The effect of bronchofiberoptic examination on oxygenation status. Chest 67: 137140, 1975 4 Sackner MA: Bronchofiberscopy. Am Rev Respir Dis Ill: 62, 1975 5 Widdicombe JG: Regulation of tracheobronchial smooth muscle. Physiol Rev 43:1, 1963 6 Goldzimer EL, Konopka RG, Moser KM: Reversal of the perfusion defect in experimental canine lobar pneumococcal pneumonia. J Appl Physiol37 :85-91, 1974 7 Albertini RE, Harrell JH, Kurihara N, et al: Arterial hypoxemia induced by fiberoptic bronchoscopy. JAMA 230:1666, 1974 8 Deland FH, Wagner HN: Lung and Heart. Philadelphia, WB Saunders Co, 1970

FIBEROPTIC BRONCHOSCOPY-INDUCED VENTILATION-PERFUSION ALTERATIONS 337

Ventilation-perfusion alterations induced by fiberoptic bronchoscopy.

I CUNICAL INVESTIGATIONS Ventilation-Perfusion Alterations Induced by Fiberoptic Bronchoscopy* Bernard B. Brach, M.D.; 00 German G. Escano, M.D.; ]a...
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