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Effect of Body Position on Gas Exchange in Patients With Unilateral Central Airway Lesions
Effect of Body Position on Gas Exchange in Patients With Unilateral Central Airway Lesions* Down With the Good Lung? Shi-Chuan Chang, M. D . , Ph.D . , EC.C.E; Huei-lng Chang, B . S . ; Cuang-Ming Shiuo, M.B., EC.C.F!;and Reury-&rng Perng, M.D., Ph.D., EC.C.F! In this study, we evaluated the effect of body position (erect, supine, and two decubitus positions) on gas exchange (alveolar-arterial Po, difference [AaPOJ) in 35 patients who had various degrees of lung collapse roentgenographically caused by unilateral central airway lesions, with special reference to the difference in AaPO, between two lateral decubitus positions. The patients were divided into two groups. Group 1 was composed of 23 patients with FEV,I FVC >70 percent. In group 2, there were 12 patients with FEV,IFVC <70 percent. Our results showed that the mean AaPO, of group 1 patients was least in the lateral decubitus position with normal lung down (AaPO,N), followed by those in the supine position (AaPO,S), in the lateral decubitus position with lesioned lung down (AaPO,L), and in the erect position (AaP0,E). There was no significant difference in AaPO, obtained in four positions. However, a significantly negative correlation was found between AaP0,NL (AaP0,N minus AaP0,L) and patient's FEV,
B"
y position may affect lung volume and gas exchange by altering the matching of ventilation to perfusion within the In normal subjects breathing normally, both blood flow and ventilation are greater in the dependent lung zones. However, there is no significant change in gas exchange between right and left decubitus positions in normal subject^.^,^ Previous reports stated that a higher PaO, (arterial oxygen tension) or Sa02 (arterial oxygen saturation) was obtained in the patients with unilateral lung d i s ~ r d e r s ~or - ~ unilateral l pleural e £ F u s i o n ~when ~~,~~ they lay in the lateral decubitus position with normal side down than in the lateral decubitus position with lesioned side down. At variance with the results of previous report^,'^.^^ our previous study demonstrated that gas exchange improved when the lesioned side was placed in the dependent position in 8 of 21 patients with unilateral pleural e£Fusions.14Subsequent reports showed that in one patient with centrally located lung cancer and in two patients with unilateral
finical
'From the Chest De artment, Veterans General Hospital-Tai i, and the Institute of Medicine, ~ a t i o n a~l a n g - ~ i ~n eg & ? a l College, Taipei, Taiwan, Republic of China. Manuscript received May 1; revision accepted July 9. Reprint requests: Dr: Chang. Uterans General Hospital, Taipei, Shih-Poi, Taipei, Taiwan 112, Republic of China
(p<0.05). In group 2 patients, the mean AaP0,E was least, followed by AaPO,L, AaPO,N, and AaP0,S. The changes of body position did not significantly affect gas exchange in group 2 patients. Unlike previous reports, the present study showed that AaP0,N was not exclusively less than AaP0,L in our patients. AaP0,N was higher than AaP0,L in 11 of 23 in group 1 and in 5 of 12 in group 2 patients. In summary, our results indicated that positional changes did not significantly affect gas exchange in the patients with lung collapse roentgenographically caused by unilateral central airway lesions and the dogma "Down with the good lung" could not be applied to these patients flawlessly. (Chest 1993; 103:787-91) AaPO, = alveolar-arterial Po, difference; AaP0,E = AaPO, in erect position; AaPO,L=AaPO, with lesioned lung down; AaPO,N =AaPO, with normal lung down; AaP0,NL = AaPo,N minus AaPo,L; AaPO,S = AaPO, in supine position
pulmonary embolism, oxygenation improved when the "sick" lung was dependent and deteriorated when the "good" lung was in the dependent p o s i t i ~ n . ~ ~ . ~ ~ Based on the results of aforementioned studies, it is uncertain that the dogma "Down with the good lung" can also be applied to the patients with unilateral central airway lesions. Thus, in the present study, we intended to evaluate the effect of body position on gas exchange in the patients with various degrees of lung collapse roentgenographically caused by unilateral central airway lesions and to examine the relationship between this postural effect and the patient's pulmonary function, with special reference to the difference in alveolar-arterial Po, difference (AaPO,) between two lateral decubitus positions. Thirty-five m n s e c ~ ~ t i vpatients e who had various degrees of lung collapse rnentgenopphically caused by unilateral central airway lesions were enrolled in this study. All the patients underwent fiberoptic bronchoscopy and were proved to have an endobronchial lesion in a large airway such as a main bronchus, an intermediate bronchus, or a lobar bronchus of the lesioned lung. None had a pleural effusion that was evidenced by chest mentgenography andl or chest sonography. All the patients denied cardiac disease and had a normal electrocardiogram. The patients were divided into two groups based on FEV,/FVC. Group 1 was mrnpnsed of 23 patients with FEV,/FVC greater than 70 percent. In group 2, there CHEST 1 103 1 3 1 MARCH. 1993
787
Table 1 -Clinical and Pulmonary Function Data in 35 Pbtients With Unilateral Central A i q LesioM* Group 1, N =23 (FEV,/FVC >70%) -
Group2, N=12 (FEV,/FVC <7096)
Table 2-Distribution of Central A i m y L e h in 35 Patients* Location of Lesion
Group 1, N=23 (FEV,/FVC >70%)
Group 2, N = 12 (FEV,/FVC <70%)
LMB RMB RIMB LULB LLLB
9 7 5 2 -
6 2 2 1 1
-
Sex, M/F Age, yr Diagnosis, CA/TB Lesioned side, UR FEV,, L % of pred FVC, L % of pred FEV,/FVC
*LMB =left main bronchus; RMB= right main bronchus; RIMB= right intermediate bronchus; LULB=left upper lobe bronchus; LLLB = left lower lobe bronchus.
-
*Values of mean and SD are given. CA = cancer; TB = tuberculosis; L = left lung; R = right lung. were 12 patients with FEV,/FVC less than 70 percent. Spirometry was performed on the standard erect (seated) position in all patients with a minimum of three times (using a CPI 5000 IV, Could, Houston, Tex). The best values of FVC and FEV, were selected for analysis. Erect, supine, and two lateral decubitus positions were studied in random order. Samples of arterial blood were drawn anaerobically 20 min after assumption ofa new position with the patients breathing room air. Blood samples for PaO,, PaCO,, and pH values were analyzed immediately (using ABL 111, Radiometer, Copenhagen, Denmark). PaO, (alveolar oxygen tension) is calculated by the following equation. PAO,= (barometric pressure - 47) x FIo, - PaCOJR. R, an exchange ratio, is assumed as 0.8 in this study. The alveolararterial Po, difference (AaPOJ is calculated by subtraction of PaO, from PAO,. Statistical comparison of the data, including arterial blood gas and AaPO,, obtained in four positions was carried out by analysis of variance. The relationship between the alteration in AaPO, in different lateral decubitus positions and the patient's pulmonary function parameters (FEV, and FVC) or severity of gas exchange impairment (AaPOJ was examined by using the linear correlation coefficient. A p value less than 0.05 was considered statistically significant.
The clinical and pulmonary function data in groups 1 and 2 are summarized in Table 1. In group 1, there were 15 men and 8 women. The ages ranged from 30 to 80 years, with a mean of 60+ 15 years. The underlying disease was lung cancer in 16 and tuberculosis in 7 patients. The lesion was confined to the left lung in 11 and right lung in 12 patients. Pulmonary function data revealed the patients had normal ventilatory function to various degrees of restrictive ventilatory defect. FEV,/FVC was greater than 70 percent
in all. In group 2, there were 11 men and 1 woman. The ages ranged from 59 to 70 years, with a mean of 64 + 4 years. The underlying disease was lung cancer in all. The lesion was on the left lung in eight and on the right lung in four patients. All had various degrees of obstructive ventilatory defect (FEV,/FVC range, 48 to 68 percent). The distribution of central airway lesions in 35 patients is shown in Table 2. Main bronchus was the most commonly affected location, followed by intermediate bronchus and lobar bronchus. The arterial blood gas and AaPO, values obtained in four positions in group 1patients are shown in Table 3. The mean PaO, (79.4 + 10.0 mm Hg, mean + SD) was highest in the lateral decubitus position with normal lung down (PaO,N), followed by 79.0+ 10.9 mm Hg in the supine position (PaO,S), 78.62 11.0 mm Hg in the erect position (PaO,E), and 77.829.4 mm Hg in the lateral decubitus position with lesioned lung down (Pa0,L). Similar to the PaO, data, the mean AaPO, (28.37 2 13.86 mm Hg, mean 4 SD) was least in the lateral decubitus position with normal lung down (AaP02N),followed by 28.95 k 14.94 mm Hg in the supine position (AaP02S), 29.20+ 13.20 mm Hg in the lateral decubitus position with lesioned lung down (AaPO,L), and 29.21 2 14.18 mm Hg in the erect position (AaP0,E). However, there was no significant difference in the arterial blood gas and AaPO, values obtained in the four positions. In group 2 patients, the arterial blood gas and AaPO, values obtained in the four positions are shown in Table 4. The mean Pa0,E (80.4 + 14.5 mm Hg, mean + SD) was highest, followed by PaO,L (75.9 + 14.0 mm Hg), Pa0,N (75.9 2 13.0 mm Hg), and Pa0,S (75.0
Table 3 - A r t d Blood Gas and AaPO, Values in 23 Patient8 With Unilateral Central A i m y L e h * (FEV,IFVC >70%) E
S
L
N
PaO,, mm Hg 78.65 11.0 (51.8-96.2) 79.02 10.9 (54.8-98.0) 77.859.4 (58.7-95.1) 79.4+ 10.0 (55.7-98.7) (23.7-41.4) 34.224.4 (26.1-43.0) 33.624.1 (26.0-41.3) PaCO,,mmHg 33.654.1 (25.8-39.9) 33.454.1 PH 7.451 20.039 (7.380-7.526) 7.451 50.039 (7.369-7.534) 7.4492 0.036 (7.386-7.523) 7.45420.041 (7.386-7.538) AaPO,, mm Hg 29.21214.18 (3.65-56.93) 28.95514.94 (0.4860.93) 29.20+13.20 (3.75-58.41) 28.37213.86 (1.28-61.53)
p Value NS NS NS NS
*Values of mean and SD are given. The data in parentheses are range. E =erect position; S = supine position; L = lateral decubitus position with lesioned lung down; N =lateral decubitus position with normal lung down; NS = not significant.
788
Effectof Body P o & h on Gas Exchange (Cheng et a/)
Table 4-Arterial Blood Gas and AaPO, Values in 12 Patients With Unilateral Central A i m y Lesions* (FEV,IFVC <7W) E
S
L
N
p Value
80.42 14.5 (48.0-97.9) 75.0 + 12.9 (48.2-93.4) 75.9+ 14.0 (46.7-91.4) 75.9+ 13.0 (53.0-99.3) PaO,, mm Hg PaCO,,mmHg 34.023.3 (28.3-38.1) 34.924.4 (27.9-42.7) 35.523.7 (28.0-40.4) 35.125.1 (25.7-41.8) 7.448 2 0.054 (7.397-7.568) 7.454 + 0.048 (7.401-7.583) 7.448 +0.051 (7.388-7.590) 7.450+ 0.047 (7.394-7.569) pH AaPO,, mm Hg 26.742 12.53 (12.98-57.11) 31.10+ 10.53 (20.71-56.28) 29.46+ 12.14 (17.33-58.53) 29.955 12.27 (13.05-55.85)
NS NS NS NS
*Values of mean and SD are given. The data in parentheses are range. E = erect position; S = supine position; L = lateral decubitus position with lesioned lung down; N = lateral decubitus position with normal lung down; NS =not significant.
12.9 mm Hg). The mean AaP0,E (26.74 f 12.53 mm Hg, mean + SD) was least, followed by AaP0,L (29.46+ 12.14 mm Hg), AaP0,N (29.95+ 12.27 mm Hg), and AaP0,S (31.1 f 10.53 mm Hg). As in group 1 patients, there was no significant difference in the arterial blood gas and AaPaO, values obtained in the four positions. The Pa0,NL (Pa0,N minus Pa0,L) and AaP0,NL (AaP0,N minus AaP0,L) values in groups 1 and 2 are summarized in Table 5. Unlike previous reports, our data showed that Pa0,N was not exclusively higher than Pa0,L. In group 1patients, Pa0,NL ranged from - 9.0 to 14.0 mm Hg, with a mean of 1.68+ 6.56 mm Hg (mean f SD). In group 2 patients, Pa0,NL ranged from - 1 2 . 1 t o 1 5 . 0 mm H g , with a mean of -0.04 k8.18 mm Hg. Pa0,N was less than Pa0,L in 10 of 23 in group 1 and in 5 of 12 in group 2 patients. Our results also showed that AaP0,N was not exclusively less than AaP0,L. AaP0,NL ranged from - 13.26 to 9.37 mm Hg, with a mean of - 0.83 + 5.94 mm Hg (mean + SD) in group 1 patients. In group 2 patients, AaP0,NL ranged from - 12.5 to 13.85 mm Hg, with a mean of 0.49k9.34 mm Hg. AaP0,N was higher than AaP0,L in 11 of 23 in group 1 and five of 12 in group 2 patients. In group 1 patients, a significantly negative correlation was found between AaP0,NL and FEV, (p<0.05) (Fig 1). However, k
Table 5-Pa0,NL and AaP0,NL in 35 Patients With Unilateral Central A i m y Lesions* Group 1, N = 23 (FEV,/FVC>70%) PaO,NL, mm Hg Mean + S D Range >OO
1.6826.56 -9.0 to 14.0 n=13 n = 10 -0.8325.94 9.37 n = 11 n = 12
- 13.26 to
AaP0,NL did not correlate well with FVC or severity of gas exchange impairment. In group 2 patients, AaP0,NL did not significantly correlate with FEV,, FVC, and severity of gas exchange impairment. Our results showed that the changes ofbody position did not significantly affect gas exchange in the patients with various degrees of lung collapse roentgenographically caused by unilateral central airway lesions. Although mean Pa0,N was higher than mean Pa0,L and mean AaP0,N was less than AaP0,L in group 1 patients who had no obstructive ventilatory defect, the difference in the values of PaO, and AaPO, between two lateral decubitus positions showed no statistical significance. The PaO, and AaPO, values obtained in two lateral decubitus positions were quite similar in group 2 patients who had various degrees of obstructive ventilatory impairment. As in group 1 patients, there were no significant differences in the PaO, and AaPO, values obtained in two lateral decubitus positions. Furthermore, our results demonstrated that a favorable gas exchange was not exclusively present when the patients lay in the lateral decubitus position with normal lung down. Pa0,N was less than Pa0,L in 10 of 23 in group 1 and 5 of 12 in group 2. AaP0,N was higher than AaP0,L in 11 of 23 patients in group 1 and 5 of 12 patients in group 2. These findings were
Group 2, N = 12 (FEV,/FVC<70%)
-0.0428.18 15.0 n =7 n =5
- 12.1 to
0.49+ 9.34 13.85 n=5 n =7
- 12.50 to
*PaO,NL = Pa0,N - Pa0,L; AaP0,NL = AaP0,N - AaP0,L; Pa0,N = PaO, in lateral decubih~sposition with normal lung down; PaO,L=PaO, in lateral decubitus position with lesioned lung down; AaP0,N = AaPO, in lateral decubitus position with normal lung down; AaPO,L=AaPO, in lateral decubitus position with lesioned lung down.
FEV1 (% of Pred.) FIGURE 1. The AaPO, ditference (AaP0,NL = AaP0,N - AaP0,L) between two lateral decubitus positions was significantly correlated with FEV,. N =lateral decubitus position with normal lung down; L = lateral decubitus position with lesioned lung down. CHEST I 103 1 3 1 MARCH, 1993
789
at variance with the results of previous workers who stated that a favorable gas exchange could be obtained exclusively in the patients with unilateral lung disorders when they were positioned in the lateral decubitus position with normal lung d o ~ n . ~ - l ~ The reasons for these discrepancies may be explained by the following: (1) the aforementioned studies included a heterogeneous group of patients with different pulmonary pathologic processes and the cases of unilateral lung collapse were limited; (2) the impairment of gas exchange seemed more severe in the reported patients than ours; and (3) most of the reported-on patients required supplementary oxygen therapy and this may more or less mask and correct ventilation-perfusion mismatch and interfere with the effect of body position on gas exchange. Interestingly, our results showed that a significantly negative correlation was found between AaP0,NL and FEV, in group 1 patients (Fig 1). AaP0,N was higher than AaP0,L in the patients with moderate to severe reduction of FEV,, whereas the reverse applied in the patients with rather normal or mild-to-moderate reduction of FEV, . The most likely mechanism for the observed phenomenon involved positionally induced changes in the matching of ventilation to perfusion and/or shunting of venous blood between the two lateral decubitus positions. Lung collapse decreases lung volume, and thus, decreases ventilation to the lesioned lung. It may also relatively increase closing volume due to a decrease in expiratory reserve volume. The above effects of lung collapse may lower the overall ventilationperfusion ratios in the lesioned lung and cause widening of AaPO,. When the patients with lung collapse caused by unilateral central airway lesions lie in the lateral decubitus position with lesioned lung down, one may anticipate that a worsening of ventilationperfusion inequality will ensue because gravity increases the perfusion to the lesioned lung in which there is a low ventilation-perfusion ratio. However, when the patients are positioned in the lateral decubitus position with normal lung down, blood is shifted away from these areas to the better ventilated lung with an improvement in oxygenation. When lung collapse becomes more severe (reflected by FEV,), lung collapse may begin to have an impact on perfusion and decrease blood flow to the lesioned lung. The mechanisms responsible for this decrease in blood flow may be mechanical and/or due to hypoxic vasoconstriction resulting from local hypoxia in the lesioned lung. This effect may be more profound when the lesioned lung is in a dependent position. The above effects may shift both ventilation and perfusion to the contralateral normal lung. Accordingly, when the patients lie in the lesioned-lung-dependent position, there is no further worsening of gas exchange.
It is unclear why gas exchange deteriorated in group 1 patients who had moderate to severe reduction of FEV, when they lay in the lateral decubitus position with normal lung down. Possibly obstruction of the lesioned airway might become more severe when the patients were positioned in the lateral decubitus position with normal lung down. This will decrease ventilation to the lesioned lung and cause ventilationperfusion mismatch in the lesioned lung. Another reason may be movement of airway secretions from the lesioned lung to the normal lung when the patients lie in the normal-lung-dependent position. This may cause less ventilation to the n o r m a lung- and result in hypoxemia through ventilation-perfusion mismatch and/or shunting of venous blood. In conclusion, the present study demonstrated that positional changes did not significantly affect gas exchange in the patients with various degrees of lung collapse roentgenographically caused by unilateral central airway lesions. The dogma "Down with the good lung" could not be applied to these patients flawlessly. In addition, we found that there was a significantly negative correlation between AaP0,NL and FEV, in group 1 patients who had no obstructive ventilatory defect. AaP0,N was less than AaP0,L in the patients with almost normal and mild-to-moderate reduction of FEV,. The reverse applied in the patients with moderate-to-severe reduction in FEV,. T h e above findings may provide a guide for selecting the more favorable lateral decubitus position that maximizes gas exchange and adjusting the adequate inspired oxygen concentration if supplementary oxygen supply is needed.
REFERENCES
1 West JB, Dollery CT. Distribution of blood flow ventilationperfusion ratio in the lung, measured with radioactive CO,. J Appl Physiol 1960; 15:405-10 2 Blair E, Hickam JB. The effect of change in body position on lung volume and intrapulmonary gas mixing in normal subjects. J Clin Invest 1955; 34:383-89 3 Bryan AC, Bentivoglio LG, Beerel F, MacLeich H, Zidulka A, Bates DY Factors affecting regional distribution of ventilation and perfusion in the lung. J Appl Physiol 1964; 19:395-402 4 Kneko K, Milic-Emili J, Dolovich MB, Dawson A, Bates Y Regional distribution of ventilation and perfusion as a function of body position. J Appl Physiol 1966; 21:767-76 5 Craig DB, Wahba WM, Don HF, Couture JC, Becklake MR. Closing volume and its relationship to gas exchange in seated and supine positions. J Appl Physiol 1971; 31:717-21 6 Marti CH, Ulmer WT. Absence of effect of the body position on arterial blood gases. Respiration 1982; 4341-4 7 Zack MB, Pontoppidan H, Kazemi H. The effect of lateral position on gas exchange in pulmonary disease: a prospective evaluation. Am Rev Respir Dis 1974; 110:49-53 8 Remolina C , Khan AU, Santiago TV, Edelman NH. Positional hypoxemia in unilateral lung disease. N Engl J Med 1981; 304: 523-25 9 Fishman AF! Down with the good lung. N Engl J Med 1981; 304:537-38 10 Dhainaut JF, Bons J, Bricard C , Monsallier JF. Improved Effect of Body Position on Gas Exchange (Chang et al)
oxygenation in patients with extensive unilateral pneumonia using the lateral decubitus position. Thorax 1980; 35792-93 11 Cillespie DJ, Rehder K. Body position and ventilation-perfusion relationships in unilateral pulmonary disease. Chest 1987; 91: 75-9 12 Sonnenblick M, Melzer E, Rosin AJ. Body positional effect on gas exchange in unilateral pleural effusion. Chest 1983; 83:78486 13 Neagley SR, Zwillich CW. The effect of positional changes on oxygenation in patients with pleural effusions. Chest 1985; 88:
JUNE
13-18 1993
714-17 14 Chang SC, Shiao GM, Perng RI! Postural effect on gas exchange in the patients with unilateral pleural effusions. Chest 1989; 96: 60-3 15 Mahler DA, Snyder PE, Virgulto JA,Loke J. Positional dyspnea and oxygen desaturation related to carcinoma of the lung: up with the good lung. Chest 1983; 839326-27 16 Badr MS, Grossman JE. Positional changes in gas exchange after unilateral pulmonary embolism. Chest 1990; 98:1514-16
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CHEST 1 103 1 3 1 MARCH. 1993
791
B"
y position may affect lung volume and gas exchange by altering the matching of ventilation to perfusion within the In normal subjects breathing normally, both blood flow and ventilation are greater in the dependent lung zones. However, there is no significant change in gas exchange between right and left decubitus positions in normal subject^.^,^ Previous reports stated that a higher PaO, (arterial oxygen tension) or Sa02 (arterial oxygen saturation) was obtained in the patients with unilateral lung d i s ~ r d e r s ~or - ~ unilateral l pleural e £ F u s i o n ~when ~~,~~ they lay in the lateral decubitus position with normal side down than in the lateral decubitus position with lesioned side down. At variance with the results of previous report^,'^.^^ our previous study demonstrated that gas exchange improved when the lesioned side was placed in the dependent position in 8 of 21 patients with unilateral pleural e£Fusions.14Subsequent reports showed that in one patient with centrally located lung cancer and in two patients with unilateral
finical
'From the Chest De artment, Veterans General Hospital-Tai i, and the Institute of Medicine, ~ a t i o n a~l a n g - ~ i ~n eg & ? a l College, Taipei, Taiwan, Republic of China. Manuscript received May 1; revision accepted July 9. Reprint requests: Dr: Chang. Uterans General Hospital, Taipei, Shih-Poi, Taipei, Taiwan 112, Republic of China
(p<0.05). In group 2 patients, the mean AaP0,E was least, followed by AaPO,L, AaPO,N, and AaP0,S. The changes of body position did not significantly affect gas exchange in group 2 patients. Unlike previous reports, the present study showed that AaP0,N was not exclusively less than AaP0,L in our patients. AaP0,N was higher than AaP0,L in 11 of 23 in group 1 and in 5 of 12 in group 2 patients. In summary, our results indicated that positional changes did not significantly affect gas exchange in the patients with lung collapse roentgenographically caused by unilateral central airway lesions and the dogma "Down with the good lung" could not be applied to these patients flawlessly. (Chest 1993; 103:787-91) AaPO, = alveolar-arterial Po, difference; AaP0,E = AaPO, in erect position; AaPO,L=AaPO, with lesioned lung down; AaPO,N =AaPO, with normal lung down; AaP0,NL = AaPo,N minus AaPo,L; AaPO,S = AaPO, in supine position
pulmonary embolism, oxygenation improved when the "sick" lung was dependent and deteriorated when the "good" lung was in the dependent p o s i t i ~ n . ~ ~ . ~ ~ Based on the results of aforementioned studies, it is uncertain that the dogma "Down with the good lung" can also be applied to the patients with unilateral central airway lesions. Thus, in the present study, we intended to evaluate the effect of body position on gas exchange in the patients with various degrees of lung collapse roentgenographically caused by unilateral central airway lesions and to examine the relationship between this postural effect and the patient's pulmonary function, with special reference to the difference in alveolar-arterial Po, difference (AaPO,) between two lateral decubitus positions. Thirty-five m n s e c ~ ~ t i vpatients e who had various degrees of lung collapse rnentgenopphically caused by unilateral central airway lesions were enrolled in this study. All the patients underwent fiberoptic bronchoscopy and were proved to have an endobronchial lesion in a large airway such as a main bronchus, an intermediate bronchus, or a lobar bronchus of the lesioned lung. None had a pleural effusion that was evidenced by chest mentgenography andl or chest sonography. All the patients denied cardiac disease and had a normal electrocardiogram. The patients were divided into two groups based on FEV,/FVC. Group 1 was mrnpnsed of 23 patients with FEV,/FVC greater than 70 percent. In group 2, there CHEST 1 103 1 3 1 MARCH. 1993
787
Table 1 -Clinical and Pulmonary Function Data in 35 Pbtients With Unilateral Central A i q LesioM* Group 1, N =23 (FEV,/FVC >70%) -
Group2, N=12 (FEV,/FVC <7096)
Table 2-Distribution of Central A i m y L e h in 35 Patients* Location of Lesion
Group 1, N=23 (FEV,/FVC >70%)
Group 2, N = 12 (FEV,/FVC <70%)
LMB RMB RIMB LULB LLLB
9 7 5 2 -
6 2 2 1 1
-
Sex, M/F Age, yr Diagnosis, CA/TB Lesioned side, UR FEV,, L % of pred FVC, L % of pred FEV,/FVC
*LMB =left main bronchus; RMB= right main bronchus; RIMB= right intermediate bronchus; LULB=left upper lobe bronchus; LLLB = left lower lobe bronchus.
-
*Values of mean and SD are given. CA = cancer; TB = tuberculosis; L = left lung; R = right lung. were 12 patients with FEV,/FVC less than 70 percent. Spirometry was performed on the standard erect (seated) position in all patients with a minimum of three times (using a CPI 5000 IV, Could, Houston, Tex). The best values of FVC and FEV, were selected for analysis. Erect, supine, and two lateral decubitus positions were studied in random order. Samples of arterial blood were drawn anaerobically 20 min after assumption ofa new position with the patients breathing room air. Blood samples for PaO,, PaCO,, and pH values were analyzed immediately (using ABL 111, Radiometer, Copenhagen, Denmark). PaO, (alveolar oxygen tension) is calculated by the following equation. PAO,= (barometric pressure - 47) x FIo, - PaCOJR. R, an exchange ratio, is assumed as 0.8 in this study. The alveolararterial Po, difference (AaPOJ is calculated by subtraction of PaO, from PAO,. Statistical comparison of the data, including arterial blood gas and AaPO,, obtained in four positions was carried out by analysis of variance. The relationship between the alteration in AaPO, in different lateral decubitus positions and the patient's pulmonary function parameters (FEV, and FVC) or severity of gas exchange impairment (AaPOJ was examined by using the linear correlation coefficient. A p value less than 0.05 was considered statistically significant.
The clinical and pulmonary function data in groups 1 and 2 are summarized in Table 1. In group 1, there were 15 men and 8 women. The ages ranged from 30 to 80 years, with a mean of 60+ 15 years. The underlying disease was lung cancer in 16 and tuberculosis in 7 patients. The lesion was confined to the left lung in 11 and right lung in 12 patients. Pulmonary function data revealed the patients had normal ventilatory function to various degrees of restrictive ventilatory defect. FEV,/FVC was greater than 70 percent
in all. In group 2, there were 11 men and 1 woman. The ages ranged from 59 to 70 years, with a mean of 64 + 4 years. The underlying disease was lung cancer in all. The lesion was on the left lung in eight and on the right lung in four patients. All had various degrees of obstructive ventilatory defect (FEV,/FVC range, 48 to 68 percent). The distribution of central airway lesions in 35 patients is shown in Table 2. Main bronchus was the most commonly affected location, followed by intermediate bronchus and lobar bronchus. The arterial blood gas and AaPO, values obtained in four positions in group 1patients are shown in Table 3. The mean PaO, (79.4 + 10.0 mm Hg, mean + SD) was highest in the lateral decubitus position with normal lung down (PaO,N), followed by 79.0+ 10.9 mm Hg in the supine position (PaO,S), 78.62 11.0 mm Hg in the erect position (PaO,E), and 77.829.4 mm Hg in the lateral decubitus position with lesioned lung down (Pa0,L). Similar to the PaO, data, the mean AaPO, (28.37 2 13.86 mm Hg, mean 4 SD) was least in the lateral decubitus position with normal lung down (AaP02N),followed by 28.95 k 14.94 mm Hg in the supine position (AaP02S), 29.20+ 13.20 mm Hg in the lateral decubitus position with lesioned lung down (AaPO,L), and 29.21 2 14.18 mm Hg in the erect position (AaP0,E). However, there was no significant difference in the arterial blood gas and AaPO, values obtained in the four positions. In group 2 patients, the arterial blood gas and AaPO, values obtained in the four positions are shown in Table 4. The mean Pa0,E (80.4 + 14.5 mm Hg, mean + SD) was highest, followed by PaO,L (75.9 + 14.0 mm Hg), Pa0,N (75.9 2 13.0 mm Hg), and Pa0,S (75.0
Table 3 - A r t d Blood Gas and AaPO, Values in 23 Patient8 With Unilateral Central A i m y L e h * (FEV,IFVC >70%) E
S
L
N
PaO,, mm Hg 78.65 11.0 (51.8-96.2) 79.02 10.9 (54.8-98.0) 77.859.4 (58.7-95.1) 79.4+ 10.0 (55.7-98.7) (23.7-41.4) 34.224.4 (26.1-43.0) 33.624.1 (26.0-41.3) PaCO,,mmHg 33.654.1 (25.8-39.9) 33.454.1 PH 7.451 20.039 (7.380-7.526) 7.451 50.039 (7.369-7.534) 7.4492 0.036 (7.386-7.523) 7.45420.041 (7.386-7.538) AaPO,, mm Hg 29.21214.18 (3.65-56.93) 28.95514.94 (0.4860.93) 29.20+13.20 (3.75-58.41) 28.37213.86 (1.28-61.53)
p Value NS NS NS NS
*Values of mean and SD are given. The data in parentheses are range. E =erect position; S = supine position; L = lateral decubitus position with lesioned lung down; N =lateral decubitus position with normal lung down; NS = not significant.
788
Effectof Body P o & h on Gas Exchange (Cheng et a/)
Table 4-Arterial Blood Gas and AaPO, Values in 12 Patients With Unilateral Central A i m y Lesions* (FEV,IFVC <7W) E
S
L
N
p Value
80.42 14.5 (48.0-97.9) 75.0 + 12.9 (48.2-93.4) 75.9+ 14.0 (46.7-91.4) 75.9+ 13.0 (53.0-99.3) PaO,, mm Hg PaCO,,mmHg 34.023.3 (28.3-38.1) 34.924.4 (27.9-42.7) 35.523.7 (28.0-40.4) 35.125.1 (25.7-41.8) 7.448 2 0.054 (7.397-7.568) 7.454 + 0.048 (7.401-7.583) 7.448 +0.051 (7.388-7.590) 7.450+ 0.047 (7.394-7.569) pH AaPO,, mm Hg 26.742 12.53 (12.98-57.11) 31.10+ 10.53 (20.71-56.28) 29.46+ 12.14 (17.33-58.53) 29.955 12.27 (13.05-55.85)
NS NS NS NS
*Values of mean and SD are given. The data in parentheses are range. E = erect position; S = supine position; L = lateral decubitus position with lesioned lung down; N = lateral decubitus position with normal lung down; NS =not significant.
12.9 mm Hg). The mean AaP0,E (26.74 f 12.53 mm Hg, mean + SD) was least, followed by AaP0,L (29.46+ 12.14 mm Hg), AaP0,N (29.95+ 12.27 mm Hg), and AaP0,S (31.1 f 10.53 mm Hg). As in group 1 patients, there was no significant difference in the arterial blood gas and AaPaO, values obtained in the four positions. The Pa0,NL (Pa0,N minus Pa0,L) and AaP0,NL (AaP0,N minus AaP0,L) values in groups 1 and 2 are summarized in Table 5. Unlike previous reports, our data showed that Pa0,N was not exclusively higher than Pa0,L. In group 1patients, Pa0,NL ranged from - 9.0 to 14.0 mm Hg, with a mean of 1.68+ 6.56 mm Hg (mean f SD). In group 2 patients, Pa0,NL ranged from - 1 2 . 1 t o 1 5 . 0 mm H g , with a mean of -0.04 k8.18 mm Hg. Pa0,N was less than Pa0,L in 10 of 23 in group 1 and in 5 of 12 in group 2 patients. Our results also showed that AaP0,N was not exclusively less than AaP0,L. AaP0,NL ranged from - 13.26 to 9.37 mm Hg, with a mean of - 0.83 + 5.94 mm Hg (mean + SD) in group 1 patients. In group 2 patients, AaP0,NL ranged from - 12.5 to 13.85 mm Hg, with a mean of 0.49k9.34 mm Hg. AaP0,N was higher than AaP0,L in 11 of 23 in group 1 and five of 12 in group 2 patients. In group 1 patients, a significantly negative correlation was found between AaP0,NL and FEV, (p<0.05) (Fig 1). However, k
Table 5-Pa0,NL and AaP0,NL in 35 Patients With Unilateral Central A i m y Lesions* Group 1, N = 23 (FEV,/FVC>70%) PaO,NL, mm Hg Mean + S D Range >O
1.6826.56 -9.0 to 14.0 n=13 n = 10 -0.8325.94 9.37 n = 11 n = 12
- 13.26 to
AaP0,NL did not correlate well with FVC or severity of gas exchange impairment. In group 2 patients, AaP0,NL did not significantly correlate with FEV,, FVC, and severity of gas exchange impairment. Our results showed that the changes ofbody position did not significantly affect gas exchange in the patients with various degrees of lung collapse roentgenographically caused by unilateral central airway lesions. Although mean Pa0,N was higher than mean Pa0,L and mean AaP0,N was less than AaP0,L in group 1 patients who had no obstructive ventilatory defect, the difference in the values of PaO, and AaPO, between two lateral decubitus positions showed no statistical significance. The PaO, and AaPO, values obtained in two lateral decubitus positions were quite similar in group 2 patients who had various degrees of obstructive ventilatory impairment. As in group 1 patients, there were no significant differences in the PaO, and AaPO, values obtained in two lateral decubitus positions. Furthermore, our results demonstrated that a favorable gas exchange was not exclusively present when the patients lay in the lateral decubitus position with normal lung down. Pa0,N was less than Pa0,L in 10 of 23 in group 1 and 5 of 12 in group 2. AaP0,N was higher than AaP0,L in 11 of 23 patients in group 1 and 5 of 12 patients in group 2. These findings were
Group 2, N = 12 (FEV,/FVC<70%)
-0.0428.18 15.0 n =7 n =5
- 12.1 to
0.49+ 9.34 13.85 n=5 n =7
- 12.50 to
*PaO,NL = Pa0,N - Pa0,L; AaP0,NL = AaP0,N - AaP0,L; Pa0,N = PaO, in lateral decubih~sposition with normal lung down; PaO,L=PaO, in lateral decubitus position with lesioned lung down; AaP0,N = AaPO, in lateral decubitus position with normal lung down; AaPO,L=AaPO, in lateral decubitus position with lesioned lung down.
FEV1 (% of Pred.) FIGURE 1. The AaPO, ditference (AaP0,NL = AaP0,N - AaP0,L) between two lateral decubitus positions was significantly correlated with FEV,. N =lateral decubitus position with normal lung down; L = lateral decubitus position with lesioned lung down. CHEST I 103 1 3 1 MARCH, 1993
789
at variance with the results of previous workers who stated that a favorable gas exchange could be obtained exclusively in the patients with unilateral lung disorders when they were positioned in the lateral decubitus position with normal lung d o ~ n . ~ - l ~ The reasons for these discrepancies may be explained by the following: (1) the aforementioned studies included a heterogeneous group of patients with different pulmonary pathologic processes and the cases of unilateral lung collapse were limited; (2) the impairment of gas exchange seemed more severe in the reported patients than ours; and (3) most of the reported-on patients required supplementary oxygen therapy and this may more or less mask and correct ventilation-perfusion mismatch and interfere with the effect of body position on gas exchange. Interestingly, our results showed that a significantly negative correlation was found between AaP0,NL and FEV, in group 1 patients (Fig 1). AaP0,N was higher than AaP0,L in the patients with moderate to severe reduction of FEV,, whereas the reverse applied in the patients with rather normal or mild-to-moderate reduction of FEV, . The most likely mechanism for the observed phenomenon involved positionally induced changes in the matching of ventilation to perfusion and/or shunting of venous blood between the two lateral decubitus positions. Lung collapse decreases lung volume, and thus, decreases ventilation to the lesioned lung. It may also relatively increase closing volume due to a decrease in expiratory reserve volume. The above effects of lung collapse may lower the overall ventilationperfusion ratios in the lesioned lung and cause widening of AaPO,. When the patients with lung collapse caused by unilateral central airway lesions lie in the lateral decubitus position with lesioned lung down, one may anticipate that a worsening of ventilationperfusion inequality will ensue because gravity increases the perfusion to the lesioned lung in which there is a low ventilation-perfusion ratio. However, when the patients are positioned in the lateral decubitus position with normal lung down, blood is shifted away from these areas to the better ventilated lung with an improvement in oxygenation. When lung collapse becomes more severe (reflected by FEV,), lung collapse may begin to have an impact on perfusion and decrease blood flow to the lesioned lung. The mechanisms responsible for this decrease in blood flow may be mechanical and/or due to hypoxic vasoconstriction resulting from local hypoxia in the lesioned lung. This effect may be more profound when the lesioned lung is in a dependent position. The above effects may shift both ventilation and perfusion to the contralateral normal lung. Accordingly, when the patients lie in the lesioned-lung-dependent position, there is no further worsening of gas exchange.
It is unclear why gas exchange deteriorated in group 1 patients who had moderate to severe reduction of FEV, when they lay in the lateral decubitus position with normal lung down. Possibly obstruction of the lesioned airway might become more severe when the patients were positioned in the lateral decubitus position with normal lung down. This will decrease ventilation to the lesioned lung and cause ventilationperfusion mismatch in the lesioned lung. Another reason may be movement of airway secretions from the lesioned lung to the normal lung when the patients lie in the normal-lung-dependent position. This may cause less ventilation to the n o r m a lung- and result in hypoxemia through ventilation-perfusion mismatch and/or shunting of venous blood. In conclusion, the present study demonstrated that positional changes did not significantly affect gas exchange in the patients with various degrees of lung collapse roentgenographically caused by unilateral central airway lesions. The dogma "Down with the good lung" could not be applied to these patients flawlessly. In addition, we found that there was a significantly negative correlation between AaP0,NL and FEV, in group 1 patients who had no obstructive ventilatory defect. AaP0,N was less than AaP0,L in the patients with almost normal and mild-to-moderate reduction of FEV,. The reverse applied in the patients with moderate-to-severe reduction in FEV,. T h e above findings may provide a guide for selecting the more favorable lateral decubitus position that maximizes gas exchange and adjusting the adequate inspired oxygen concentration if supplementary oxygen supply is needed.
REFERENCES
1 West JB, Dollery CT. Distribution of blood flow ventilationperfusion ratio in the lung, measured with radioactive CO,. J Appl Physiol 1960; 15:405-10 2 Blair E, Hickam JB. The effect of change in body position on lung volume and intrapulmonary gas mixing in normal subjects. J Clin Invest 1955; 34:383-89 3 Bryan AC, Bentivoglio LG, Beerel F, MacLeich H, Zidulka A, Bates DY Factors affecting regional distribution of ventilation and perfusion in the lung. J Appl Physiol 1964; 19:395-402 4 Kneko K, Milic-Emili J, Dolovich MB, Dawson A, Bates Y Regional distribution of ventilation and perfusion as a function of body position. J Appl Physiol 1966; 21:767-76 5 Craig DB, Wahba WM, Don HF, Couture JC, Becklake MR. Closing volume and its relationship to gas exchange in seated and supine positions. J Appl Physiol 1971; 31:717-21 6 Marti CH, Ulmer WT. Absence of effect of the body position on arterial blood gases. Respiration 1982; 4341-4 7 Zack MB, Pontoppidan H, Kazemi H. The effect of lateral position on gas exchange in pulmonary disease: a prospective evaluation. Am Rev Respir Dis 1974; 110:49-53 8 Remolina C , Khan AU, Santiago TV, Edelman NH. Positional hypoxemia in unilateral lung disease. N Engl J Med 1981; 304: 523-25 9 Fishman AF! Down with the good lung. N Engl J Med 1981; 304:537-38 10 Dhainaut JF, Bons J, Bricard C , Monsallier JF. Improved Effect of Body Position on Gas Exchange (Chang et al)
oxygenation in patients with extensive unilateral pneumonia using the lateral decubitus position. Thorax 1980; 35792-93 11 Cillespie DJ, Rehder K. Body position and ventilation-perfusion relationships in unilateral pulmonary disease. Chest 1987; 91: 75-9 12 Sonnenblick M, Melzer E, Rosin AJ. Body positional effect on gas exchange in unilateral pleural effusion. Chest 1983; 83:78486 13 Neagley SR, Zwillich CW. The effect of positional changes on oxygenation in patients with pleural effusions. Chest 1985; 88:
JUNE
13-18 1993
714-17 14 Chang SC, Shiao GM, Perng RI! Postural effect on gas exchange in the patients with unilateral pleural effusions. Chest 1989; 96: 60-3 15 Mahler DA, Snyder PE, Virgulto JA,Loke J. Positional dyspnea and oxygen desaturation related to carcinoma of the lung: up with the good lung. Chest 1983; 839326-27 16 Badr MS, Grossman JE. Positional changes in gas exchange after unilateral pulmonary embolism. Chest 1990; 98:1514-16
Plan to Attend ACCP's
XVll World Congress on Diseases of the Chest
CHEST 1 103 1 3 1 MARCH. 1993
791