Physiologic Evaluation of Bullous Emphysema

----f

~1111.l----:p=----u_lm_on_a---=ry:.....-..=.p_hy=---s_io_log~ic_t_e_st_o_f t_h_em_o_n_th

_

Physiologic Evaluation of Bullous Emphysema* John F. Wade Ill, M.D.;t Rebecca Mortenson, M.D.;+ and Charles G. Irvin, Ph.D.§

(Chat 1991; 100:1151-54) Dco = diffusion capacity; Flo. = fraction of inspired oxygen; MVV maximum voluntary ventilation; RV residual volume; TLC total lung capa~ty;. VA alveolar volume; '=Vol VT = dead space ve~tiI~tion; VENco. = ventilatory equivalent for carbon dioxide; VElVo. = ventilatory equivalent for oxygen

= =

A

=

=

CASE HISTORY

61-year-old male smoker was referred for the evaluation of progressive dyspnea on exertion. The patient had noted slight dyspnea on exertion for several years. For his occasional exacerbations of chronic obstructive lung disease, he was treated with inhaled J:l-agonists and bursts of steroids. Five months prior to evaluation, he began noticing progressive exertional dyspnea mowing his grass or even climbing a single Bight of stairs. He denied fever, chills, weight loss, night sweats, hemoptysis, orthopnea, and pedal edema. He had a 90 pack-year smoking history, but quit 18 years ago. Results of cardiac c~theterization for exertional chest pain in 1985 were completely normal. Medications at the time of the current evaluation included aerosolized isoetharine, cromolyn, and beclomethasone, and nasally administered cromolyn. He reported no significant occupational exposures. Family history was remarkable for a mother and brother with ··pulmonary fibrosis." Physical examination revealed a well-developed man in no acute distress. Examination of the chest showed an increased anteroposterior diameter with diffusely diminished breath sounds without wheezes or rales. The veins of the neck were Bat and heart sounds were normal. The abdomen was benign and extremities were without edema or clubbing. A sample of blood showed a hematocrit of 47 percent, white blood cell count of 8,2OOIcu mm with normal differential, normal electrolytes, and normal indices of liver function. The chest roentgenogram showed bilateral upper lung-zone bullae that occupied at least one third to one half of each hemithorax (Fig 1). In addition, a chest computed tomographic (CIj scan clearly confirmed massive bullae, but also revealed compressed, relatively normal-appearing lower lobes (Fig 2). On the basis of these findings, a diagnosis of bullous emphysema was made. Further evaluation with pulmonary function tests was undertaken to help assess the feasibility of surgical therapy (bullectomy). ~operative Pulmonary

Function

Most lung volumes (Table 1) as determined by whole-body plethysmography were within normal limits; however, residual volume (RV) was elevated at 3.34 L (191 percent). Forced expiratory volume in 1 s (FEV J, forced vital capacity (FVCh and speci6c *From the Pulmonary Physiology Unit, Department of Medicine, National Jewish Center for Immunology anaRespiratory Medicine, and Pulmonary Sciences Division, University of Colorado, Health Sciences Center, Denver. tFellow in Pulmonary Medicine. tAssistant Professor of Medicine. §Associate Professor of Medicine.

conductance of the airway (SGaw) were all decreased (FEV/FYC = 62 percent). Heversible airway flow limitation was evident by an increase of 19 percent in FEV. and a 43 percent increase in FVC as detennined after bronchodilator. The flow.volume loop shown in (Fig 3, left panel) is consistent with a patient with airftow limitation. Diffusion capacity (Dco) as measured by single breath technique was low (60 percent predicted); however, it approached the normal range when corrected for alveolar volume (DcoIVA). VA is determined by the measurement of the inspired volume and the dilution of the helium during the breath hold and in normal persons VA is very similar to total lung capacity (TLC). If this measure of TLC is compared with the TLC by plethysmography, an estimation of trapped, noncommunicating gas can be made. In the present case, TLC (plethysmograph)-TLC (helium)=6.29-4.98=1.31 L of noncommunicating gas is determined. Preoperative Exercise Physiology

To evaluate the sources of the exertional dyspnea, multistaged maximum exercise was performed on a bicycle ergometer with measurements of cardiovascular, ventilatory, and gas exchange parameters (Table 2). Exercise was performed on room air (fraction of inspired oxygen, [FIoJ, 20.7 percent) with 15-W increments every minute until exhaustion. The patient achieved only 51 percent of the predicted maximum workload and 53 percent of predicted maximum oxygen consumption demonstrating an exercise limitation. This limitation was probably due to both ventilatory and gas exchange abnormalities. Measured maximum voluntary ventilation (MVV) was somewhat low at 89 Umin (79 percent predicted). The minute ventilation (65 Umin) was excessive for workload achieved, due to excessive frequency recroibnent (451min) and tidal volumes

Table 1- Pulmonary ft,nction Tat Baulta PreopertJtioely and Fioe Montlu after a Bilateral BulIectomy (BD) Preoperative

Postoperative

%

%

Baseline Pred Post-BD Baseline Pred Post-BD Volumes TLC (box) TLC (helium) FRC RV Spirometry FVC FEV. FEV/FVC (%) Diffusion

nco

DcoIVA Conductance SGaw

6.29 4.98 4.26 3.34 1.91 1.20

100

6.27

115 191

42 38

62

75

4.84

3.91 2.79

4.65 4.81 3.22 1.71

88 74

3.18 1.77

2.74 1.43

2.90 1.91

65 62

3.00 2.05

52

18.70 3.75

60 80

0.08

51

0.10

66

68

18.09 3.76

54

0.17

105

76

CHEST I 100 I 4 I OClOBER, 1991

0.33

1151

FIGURE la (left). Posteroanterior (PA) and lateral (lb, right), chest roentgenogram of the patient (61-yearold man) with bullous emphysema. Note increased lucency of the upper lobes.

(1,450 ml) less than 60 percent of vital capacity. Dead space ventilation (VoIVT) was normal at rest (33 percent), but it did not fall with exercise. At rest, blood gases revealed hypoxemia (PaO.=63 mm Hg; O. saturation, 91 percent; altitude, 5,260 ft) which became worse on exercise (PaO., 53 mm Hg; O. saturation, 86 percent) with a widening of the a1veo1aJ'.arterial O. gradient. The ventilatory equivalent for oxygen (VFiVoJ was abnormally high at rest and rose with exercise. The ventilatory equivalent for carbon dioxide (VFiVcoJ was elevated at rest and remained so. Anaerobic threshold was reduced at 28 percent of the predicted maximal Vo•. Heart rate was excessive for workload achieved and there was a mild hypertensive blood pressure response.

of apparently normal lung, and a moderately well-preserved FEV, after bronchodilator were determinants in the decision to proceed with a bullectomy. The patient underwent a median sternotomy with bilateral bullectomy. Operative findings revealed that approximately 75 percent of each hemithorax was filled with bullae. The postoperative course was unremarkable and he was discharged after a nine-day hospitalization. Repeated pulmonary and exercise function tests were performed approximately five months after surgery.

12

Surgical Procedure Progressive exercise limitation, bullous disease with compression

F L 0 W

Pre Operative

Post Operative

..... .•

8

~

•• ••

4

0

6

8

4

8

12

"Pred _ preBO "'. poet BO

Volume FIGURE 2. Computed tomography (Cf) scan of the patient with bullous emphysema. Section is through the lower thorax. Adjacent lung to the bullae appears relatively preserved but compressed.

1152

FIGURE 3. Maximal inspiratory and expiratory flow-volume loops. Lung volume was determined by Boyle's law using a volumedisplacement plethysmograph to fix the flows to absolute volume. Heavy dashed curve is the reference (predicted) flow volume relationship. Solid curve is prebronchodilative and lightly dashed curve is postbronchodilative. Left panel is the flow-volume relationship presurgery (bullectomy) and the right is five months postsurgery. Note the marked improvement in hyperinflation.

Table 2-MaDmal E%erciae Tolerance Eooluation* Postoperative

Preoperative Baseline Performance Max workload, W (% pred) VOl' mlImin (% pred) Cardiovascular UR, beats per minute (% pred)

90W

71 •. 114/74

Ventilation

90 9.2 12 760 33

M~Umin

7.4313~

19.2

130 (77%) 1901100

65 45

1,450 39

(91%)

40

49

54

48

28%

72 116170

145 (86%) 170190

166 (98%)

120 12.8 18 710

63 34 1,840

81 44 1,850

35

38

35

7.37fJ4153 (86%) 37

Max 120 (70%) 1560 (74%)

90 (51%) 1206 (53%)

B~mmHg

VE, Umin (at 90 W) Respiratory rate, beats per minute VT,ml VDlVT, % Gas exchange ABG (% saturation) A-a gradient, mm Hg VE BTPSNol STPD, % VE BTPSNcol STPD, % Anaerobic threshold (% pred max VoJ

Baseline

Max

7.49/33180 (95%) 3.0 44

53

7.36134/60 (90%) 28 48 44

190194

7.31fJI/60 (88%) 34

53 48

38%

*Patient was exercised on room air with a cycle ergometer to exhaustion.

PoatoperativePWmonary Function Postoperatively (1able 1), there was a significant fall in lung volumes as measured by plethysmography with a l.64-L drop in TLC to 4.65 L and a l.04-L fall in FRC to 3.22 L. Airflow improved with a 43 percent increase in FEV. to 2.05 L. Dco remained unchanged. TLC as measured by a by single breath dilution of helium (VA) was 4.81 L, which is essentially the same as the plethysmographic TLC of 4.65 L. Specific conductance normalized after surgery. The Bow-volume loop (Fig 3, right panel) is now suggestive of a mixed obstructive/restrictive process. The fact that TLC was normal (100 percent predicted) preoperatively and reduced (75 percent predicted) postoperatively is consistent with a coexistent restrictive process or with failure of the remaining lung to fully reexpand.

Postoperative Exercise Physiology Multistaged maximum exercise (Table 2) was again carried out. The patient now achieves 70 percent of predicted maximum workload and 74 percent of VOl maximum; a 20 percent increment in workload. MVV increased by 30 L to 120 Umin. Comparing the two exercise tests at workloads of90 ~ minute ventilation remained excessive (63 Umin); however, the breathing frequency response was significantly less (341min) and tidal volumes increased by approximately 400 ml to 1,840 mI. Physiologic deadspace still rose with exercise. Oxygenation was now normalized at rest (PaOI , 80 mm Hg; 0 1 saturation, 95 percent) and while hypoxemia still occurred with exercise, the fall was less (PaOI , 60 mm Hg; 0 1 saturation, 90 percent). Ventilatory equivalents for oxygen and carbon dioxide changed little and remained abnormal. Anaerobic threshold improved to 38 percent of the predicted maximal VOl and approached the lower range of normal. DISCUSSION

Progressive dyspnea on exertion is a common complaint of patients presenting to internists and pulmonologists. While a careful history and physical examination with chest roentgenogram often reveals the underlying abnormality, full pulmonary function and

exercise testing gives additional, useful information that may be used in planning and documenting efficacy of therapy: We present a case of progressive dyspnea on exertion secondary to bullous emphysema with the results of pulmonary physiology both preoperatively and postoperatively: Large emphysematous bullae may cause disability by (1) compression of functioning lung tissue causing an CCintrapulmonary pneumothorax"; (2) causing hyperinflation that may increase the work of breathing; and (3) in some cases increasing dead-space ventilation. 1 The goal of bullectomy is therefore to allow reexpansion of compressed lung and reduce hyperinflation. If this happens, both subjective and objective improvement in pulmonary function can be expected. While the history, physical examination, and chest roentgenogram (and in this case CT) clinch the diagnosis ofbullous emphysema, pulmonary function tests allow one to understand the pathophysiology of the resultant and frequently severe exercise intolerance and evaluate the effects of surgical resection. Patient selection for bullectomy can be difficult, with progressive exertional dyspnea being a main indication for bullectomy. Recurrent pneumothorax and exertional chest pain (related to bullous disease) are less common, but additional, reasons to operate. 2 Patients with the largest bullae stand to benefit most from surgery and in general, serious consideration is given to patients with bullae ~ one third of the hemithorax. Diffuse emphysema is believed by some to be a contraindication for surgery: However, if there is an appreciable amount of compressed, functioning lung adjacent to a giant bullae, even patients with severe airflow limitation may experience dramatic CHEST I 100 I 4 I OCTOBER. 1991

1153

improvement. 3,4 Indeed, some of the most impressive results in terms of functional improvement may be found in patients with an FEVI <1 L. Patients who have evidence ofchronic bronchitis or hypercapnia do less well. 2,s Bronchography; 6 tomograms, 7 angiography, 8 perfusion scans,2,S and cr scans9 have all been advocated in an attempt to better assess the extent and severity of emphysema. cr is increasingly being used to evaluate patients for bullectomy and is quite effective in defining diffuse vs localized disease as well as determining the condition of compressed lung tissue. Scans may also reveal bullae in "normal" areas that cannot be detected by roentgenograms. The reverse is also true in that the chest roentgenogram not uncommonly suggests bullae that cannot be confirmed as true discrete bullae on cr scan such as seen with severe, diffuse emphysema. lo Spirometry alone has not proved useful in distinguishing between surgical vs nonsurgical disease; however, determinations of lung volumes by both plethysmography and helium dilution are very useful in estimating the volume of trapped gas within the bullae. The larger the discrepancy between the two (box volume > helium dilution volume), the more likely surgery will be beneficial. I The role of exercise testing in the preoperative evaluation of these patients is unclear. Exercise limitation, since it is the presenting symptom, is common and typically involves ventilatory and gas exchange abnormalities. As in the present case, excessive ventilation for achieved workload is common and is usually due to an inordinate frequency recruitment with low tidal volumes. VDNT measurements are quite variable among patients and may be normal or elevated both at rest and with exercise. 11,12 Severe resting hypoxemia is uncommon due to reasonable V/Q matching of bullae and areas of compressed lung. However, exercise-induced desaturation, as in our patient, is typical. Outcome of bullectomy in properly selected patients is often dramatic. A significant increase in FEV I seems to correlate best with long-term improvement. I ,4,S,13 Vtg (or TLC) and RV by plethysmography also fall postoperatively and should approach values obtained by helium dilution as seen in our patient. The similar volumes by plethysmography and helium dilution in the present patient, as well as a stable, marginally reduced Dco, argues against any significant airtrapping and emphysema in remaining lung tissue. Improvement in Pa02 after bullectomy is a consistent Bnding in properly selected patients. 1 Although data

1154

on maximal exercise testing after surgery are scant, our patient demonstrated an impressive increase in exercise tolerance. Even though ventilation remained excessive, frequency response was less and tidal volumes were larger suggesting increased efficiency of respiration. Further improvement of exercise tolerance might be anticipated as the remaining lung remodels and reexpands. Long-term follow-up of patients who have undergone bullectomies reveals, in general, two groups of patients: first, those with more localized disease, single or few large bullae,S and who quit smoking,14 who tend to maintain the improved function ~ five to ten years after surgery; and secondly, patients with diffuse disease and/or multiple, smaller bullae and who continue to smoke, who tend to drift back toward their preoperative baseline pulmonary function. REFERENCES 1 Pride NB, Barter CE, Hugh-Jones I! The ventilation of bullae and the effect of their removal on thoracic gas volumes and tests ofoverall pulmonary function. Am Rev Respir Dis 1973; 107:8398 2 Gaensler EA, Cugell D~ Knudson RS, Fitzgerald MX. Surgical management of emphysema, Clio Chest Moo 1983; 4:443-63 3 Potgieter PD, Benatar SR, Hewitson R, Ferguson AD. Surgical treatment of bullous lung disease. Thorax 1981; 36:885-90 4 Fitzgerald MX, Keelan PJ, Cugell D~ Gaensler EA. Longterm results of surgery for bullous emphysema. J Thorac Cardiovasc Surg 1974; 68:566 5 Wesley JR, Macleod WM, Mullard KS. Evaluation and surgery of bullous emphysema. J Thorac Cardiovasc Surg 1972; 63:94555 6 Eschapasse H, Fabre J, Foffa R, Hassani M, Gaillard J, Duhan M. Interet de la pleurectomie comme complement des resections de bulles d'emphyseme. Rev Fr Mal Respir 1980; 8:155 7 Connolly JE, Wilson A. The current status ofsurgery for bullous emphysema. J Thorac Cardiovasc Surg 1989; 97:351-60 8 Fitzgerald MX, Keelan PJ, Gaensler EA. Surgery for bullous emphysema. Respiration 1973; 30: 187-200 9 Morgan NDL, Denison DM, Strickland B. Value of computed tomography for selecting patients with bullous lung disease for surgery. Thorax 1986; 41:855-62 10 Morgan NDL, Strickland B. Computed tomography in the assessment ofbuDous lung disease. Br J Dis Chest 1984; 78:1025 11 Stone DJ, Schwartz A, Feltman}A. BuDous emphysema: a longterm study of the natural history and the effects of therapy. Am Rev Respir Dis 1960; 82:493-507 12 Laurenzi GA, Turino GM, Fishman AI! Bullous disease of the lung. Am J Moo 1962; 32:361-78 13 Pearson MG, Ogilvie C. Surgical treatment of emphysematous bullae: late outcome. Thorax 1983; 38:134-37 14 Hughes }A, Macarthur AM, Hutchison DCS, Hugh-Jones I! Long term changes in lung function after surgical treatment of bullous emphysema in smokers and ex-smokers. Thorax 1984; 39:140-42

Physiologic Evaluation of Bullous Emphysema (NIde, Mortenaon,

'nnn)