Human heart-lung transplantation: physiologic aspects of the denervated lung and post-transplant obliterative bronchiolitis

Chronic Lung Allograft Dysfunction: Evolving Concepts and Therapies

The primary factor that limits long-term survival after lung transplantation is chronic lung allograft dysfunction (CLAD). CLAD also impairs quality of life and increases the costs of medical care. Our understanding of CLAD continues to evolve. Consensus definitions of CLAD and the major CLAD phenotypes were recently updated and clarified, but it remains to be seen whether the current definitions will lead to advances in management or impact care. Understanding the potential differences in pathogenesis for each CLAD phenotype may lead to novel therapeutic strategies, including precision medicine. Recognition of CLAD risk factors may lead to earlier interventions to mitigate risk, or to avoid risk factors all together, to prevent the development of CLAD. Unfortunately, currently available therapies for CLAD are usually not effective. However, novel therapeutics aimed at both prevention and treatment are currently under investigation. We provide an overview of the updates to CLAD-related terminology, clinical phenotypes and their diagnosis, natural history, pathogenesis, and potential strategies to treat and prevent CLAD.

New-onset asthma in a bilateral lung transplant patient

We present a case of new-onset asthma in a 35-year-old man who had undergone bilateral lung transplantation 11 years before due to idiopathic bronchiectasis and pulmonary hypertension. He presented with recurrent episodes of breathlessness, wheezing and coughing. Spirometry demonstrated severe airway obstruction. After treatment with systemic and inhaled corticosteroids and long-acting bronchodilators as well as short-acting beta-agonists as needed, his symptoms resolved and his spirometry normalised. A bronchial mannitol challenge test showed significant airway hyperresponsiveness and is thus consistent for a diagnosis of asthma. To our best knowledge, this is the first case of late new-onset asthma in a lung transplant recipient.

Effects of overground locomotor training on the ventilatory response to volitional treadmill walking in individuals with incomplete spinal cord injury: a pilot study

INTRODUCTION

Although there has been substantial emphasis on the neuromuscular and cardiovascular adaptations following rehabilitation, pulmonary adaptations in individuals with incomplete SCI (iSCI) in response to locomotor training have been less frequently studied. In healthy individuals, effective transition from rest to work is accomplished by a hyperpneic response, which exhibits an exponential curve with three phases. However, the degree to which our current understanding of exercise hyperpnea can be applied to individuals with iSCI is unknown. The purpose of this case series was to characterize exercise hyperpnea during a rest to constant work rate (CWR) transition before and after 12-15 weeks of overground locomotor training (OLT).

CASE PRESENTATION

Six subjects with cervical motor incomplete spinal cord injury participated in 12-15 weeks of OLT. Subjects were trained in 90-min sessions twice a week. All training activities were weight-bearing and under volitional control without the assistance of body-weight support harnesses, robotic devices or electrical stimulation. Six minutes of CWR treadmill walking was performed at self-selected pace with cardiorespiratory analysis throughout the tests before and after OLT. Averaged group data for tidal volume, breathing frequency or V_E showed no difference before and after training. V_E variability was decreased by 46.7% after OLT.

DISCUSSION

CWR V_E from rest to work was linear throughout the transition. Following OLT, there was a substantial reduction in V_E variability. Future research should investigate the lack of a phasic ventilatory response to exercise, as well as potential mechanisms of ventilatory variability and its implications for functional performance.

Neurologic Causes of Acute Respiratory Dysfunction

Many neurologic diseases can cause acute respiratory decompensation, therefore a familiarity with these diseases is critical for any clinician managing patients with respiratory dysfunction. In this article, we review the anatomy of the respiratory system, focusing on the neurologic control of respiration. We discuss general mechanisms by which diseases of the peripheral and central nervous systems can cause acute respiratory dysfunction, and review the neurologic diseases which can adversely affect respiration. Lastly, we discuss the diagnosis and general management of acute respiratory impairment due to neurologic disease.

Prevalence and correlates of a 'knee' pattern on the maximal expiratory flow-volume loop in young adults

BACKGROUND AND OBJECTIVE

Visual inspection of the maximal flow-volume curve is an important step in interpreting spirometry. Many young people have a convex inflection or 'knee' on the expiratory part of the loop. This is thought to be a normal variant, but this view is based on theoretical grounds, and the epidemiology of the knee pattern has never been reported.

METHODS

Flow-volume loops from an unselected birth cohort of 1037 individuals at ages 18, 26, 32 and 38 years were visually inspected for a knee pattern. Associations with asthma diagnoses, smoking history, body mass index (BMI) and spirometry were assessed.

RESULTS

The knee pattern was found in approximately two thirds of men and women at age 18. The prevalence decreased with age, but it was more likely to persist in women. The knee was more common after bronchodilator and was associated with higher forced expiratory volume in 1 s/forced vital capacity ratios and mid-expiratory flow rates. There was no association with smoking, except for an inverse correlation in men at age 18. No association was found with BMI. Women with asthma were less likely to have a knee at both ages 18 and 38, whereas men with asthma showed an inverse association at age 18.

CONCLUSIONS

A knee is a very common pattern on flow-volume loop in young adults. In accordance with theoretical predictions, the prevalence of the knee declines with age, but it is more likely to persist in women. It is associated with less airflow obstruction and is less common in people with asthma.

Tetraplegia is a risk factor for central sleep apnea

Sleep-disordered breathing (SDB) is highly prevalent in patients with spinal cord injury (SCI); the exact mechanism(s) or the predictors of disease are unknown. We hypothesized that patients with cervical SCI (C-SCI) are more susceptible to central apnea than patients with thoracic SCI (T-SCI) or able-bodied controls. Sixteen patients with chronic SCI, level T6 or above (8 C-SCI, 8 T-SCI; age 42.5 ± 15.5 years; body mass index 25.9 ± 4.9 kg/m(2)) and 16 matched controls were studied. The hypocapnic apneic threshold and CO2 reserve were determined using noninvasive ventilation. For participants with spontaneous central apnea, CO2 was administered until central apnea was abolished, and CO2 reserve was measured as the difference in end-tidal CO2 (PetCO2) before and after. Steady-state plant gain (PG) was calculated from PetCO2 and VE ratio during stable sleep. Controller gain (CG) was defined as the ratio of change in VE between control and hypopnea or apnea to the ΔPetCO2. Central SDB was more common in C-SCI than T-SCI (63% vs. 13%, respectively; P < 0.05). Mean CO2 reserve for all participants was narrower in C-SCI than in T-SCI or control group (-0.4 ± 2.9 vs.-2.9 ± 3.3 vs. -3.0 ± 1.2 l·min(-1)·mmHg(-1), respectively; P < 0.05). PG was higher in C-SCI than in T-SCI or control groups (10.5 ± 2.4 vs. 5.9 ± 2.4 vs. 6.3 ± 1.6 mmHg·l(-1)·min(-1), respectively; P < 0.05) and CG was not significantly different. The CO2 reserve was an independent predictor of apnea-hypopnea index. In conclusion, C-SCI had higher rates of central SDB, indicating that tetraplegia is a risk factor for central sleep apnea. Sleep-related hypoventilation may play a significant role in the mechanism of SDB in higher SCI levels.

Lung transplantation and lung volume reduction surgery

Since the publication of the last edition of the Handbook of Physiology, lung transplantation has become widely available, via specialized centers, for a variety of end-stage lung diseases. Lung volume reduction surgery, a procedure for emphysema first conceptualized in the 1950s, electrified the pulmonary medicine community when it was rediscovered in the 1990s. In parallel with their technical and clinical refinement, extensive investigation has explored the unique physiology of these procedures. In the case of lung transplantation, relevant issues include the discrepant mechanical function of the donor lungs and recipient thorax, the effects of surgical denervation, acute and chronic rejection, respiratory, chest wall, and limb muscle function, and response to exercise. For lung volume reduction surgery, there have been new insights into the counterintuitive observation that lung function in severe emphysema can be improved by resecting the most diseased portions of the lungs. For both procedures, insights from physiology have fed back to clinicians to refine patient selection and to scientists to design clinical trials. This section will first provide an overview of the clinical aspects of these procedures, including patient selection, surgical techniques, complications, and outcomes. It then reviews the extensive data on lung and muscle function following transplantation and its complications. Finally, it reviews the insights from the last 15 years on the mechanisms whereby removal of lung from an emphysema patient can improve the function of the lung left behind.

Supranormal expiratory airflow after bilateral lung transplantation is associated with improved survival

RATIONALE

flow volume loops (FVL) in some bilateral lung transplant (BLT) and heart-lung transplant (HLT) patients suggest variable extrathoracic obstruction in the absence of identifiable causes. These FVLs usually have supranormal expiratory and normal inspiratory flow rates (SUPRA pattern).

OBJECTIVES

characterize the relationship of the SUPRA pattern to predicted donor and recipient lung volumes, airway size, and survival.

METHODS

we performed a retrospective review of adult BLT/HLT patients. We defined the SUPRA FVL pattern as: (1) mid-vital capacity expiratory to inspiratory flow ratio (Ve50:Vi50) > 1.0, (2) absence of identifiable causes of extrathoracic obstruction, and (3) Ve50/FVC ≥ 1.5 s(-1). We calculated predicted total lung capacity (pTLC) ratio by dividing the donor pTLC by the recipient pTLC. We measured airway luminal areas on thoracic computer tomographic scans. We compared survival in patients with and without the SUPRA pattern.

MEASUREMENTS AND MAIN RESULTS

the SUPRA FVL pattern occurred in 56% of the 89 patients who qualified for the analysis. The pTLC ratio of SUPRA and non-SUPRA patients was 1.11 and 0.99, respectively (P = 0.004). A higher pTLC ratio was correlated with increased probability of the SUPRA pattern (P = 0.0072). Airway luminal areas were larger in SUPRA patients (P = 0.009). Survival was better in the SUPRA cohort (P = 0.009).

CONCLUSIONS

the SUPRA FVL pattern was frequent in BLT/HLT patients. High expiratory flows in SUPRA patients could result from increased lung elastic recoil or reduced airway resistance, both of which could be caused by the pTLC mismatch. Improved survival in the SUPRA cohort suggests potential therapeutic approaches to improve outcomes in BLT/HLT patients.

Electromyographic signal-activated functional electrical stimulation of abdominal muscles: the effect on pulmonary function in patients with tetraplegia

BACKGROUND

Paralysis of abdominal muscles is the main cause of respiratory dysfunctions in patients with lower cervical spinal cord lesion. Activation of the abdominal muscles using functional electrical stimulation (FES) improved respiratory function in these patients. But application of FES frequently requires a caregiver, and it may not be well synchronized with the patient's respiratory activity.

OBJECTIVE

To perform preliminary examination of electromyographic (EMG)-activated FES for caregiver-independent and synchronized cough and expiration induction in tetraplegia.

DESIGN

Self-controlled study.

SETTING

Loewenstein Rehabilitation Center, Raanana, Israel.

SUBJECTS

A total of 10 male patients with complete or almost complete tetraplegia.

MAIN OUTCOME MEASURES

Peak expiratory flow (PEF), forced vital capacity (FVC), and maximal voluntary ventilation (MVV).

METHODS

The outcome measures were examined with the abdominal muscles unassisted or assisted by various methods. These included manual assistance or application of FES, activated by a caregiver, by the patient, or by EMG signals elicited from the patient's muscle.

RESULTS

Manual assistance improved the mean PEF value by 36.7% (P<0.01) and the mean FVC value by 15.4% (P=0.01). FES did not significantly change most measurements, and patient-activated FES even reduced PEF (P<0.05). But following EMG-activated FES PEF and FVC values were higher than those following patient-activated FES (P<0.05 for PEF; P<0.01 for FVC), and their mean values were higher by 15.8 and 18.9%, respectively.

CONCLUSIONS

Abdominal FES failed to improve respiratory function in this study, but applying FES to abdominal muscles by EMG from the patient's muscle may promote caregiver-free respiration and coughing in persons with cervical SCL.

Monitoring the lung periphery of transplanted lungs

Lung transplantation is now accepted as a viable therapeutic option for patients with end-stage lung diseases, but long-term survival is threatened by bronchiolitis obliterans (BO), which is regarded as a manifestation of chronic allograft rejection. We have used studies of ventilation distribution for the early detection of this complication. In a prospective study of 57 bilateral-lung transplant recipients, we showed that the slope of phase III of the helium single-breath washout, which targets inhomogeneities of ventilation distribution in the terminal and respiratory bronchioles, was particularly sensitive to the development of BO. In a preliminary study using nitrogen multiple-breath washouts, we showed that S(acin) and S(cond), which reflect structural changes in the acinar and conductive lung zones, were both markedly increased in patients with BO. Taken together, these studies demonstrate that monitoring the function of the allograft by measuring the distribution of ventilation in the lung periphery may be a clinically valuable tool.

Simulation of Lung Function Evolution After Heart-Lung Transplantation Using a Numerical Model

A morphometry-based computational model for expiratory flow in humans was used to study the unusual configuration of the maximum expiratory flow-volume (MEFV) curve associated with alterations in lung function after heart-lung transplantation (HLT). The postoperative MEFV curve showed a peak, followed by a gently sloping plateau over the midvolume range, ending in a knee where the flow suddenly fell, instead of the usual observed uniform decrease in expiratory flow. We have tested several hypotheses about the relationship between the pattern of changes in the configuration of the MEFV curve and pathological changes in the airway mechanics through computer simulations. Principally, effects of lung denervation and airway obstruction, associated with the development of bronchiolitis obliterans in the lung periphery, have been investigated. The calculated curves are similar in appearance to the measured postoperative flow-volume curves and confirm reliability of the earlier hypotheses. We conclude that the plateau-knee configuration of the MEFV curve can result from flow limitation in one of the first airway generations, that this flow limitation coupled with an increase in peripheral airway resistance results in plateau shortening, and that flows exceeding predicted values during the second part of expiration may be produced by lung denervation. Additionally our results demonstrate that airways larger than the transitional and respiratory bronchioles can be involved in pulmonary function deterioration observed in patients affected with obliterative bronchiolitis. Our findings indicate that the computational model, based on a symmetrical dichotomous branching structure of the bronchial tree, along with pathological data, can be employed to evaluate the effects of heterogeneous changes in the lung periphery. Index Terms-Airway mechanics, forced expiration, lung transplantation, mathematical modeling, maximal expiratory flow-volume curve.

Effects of abdominal binding on breathing patterns during breathing exercises in persons with tetraplegia

STUDY DESIGN

Cross-sectional, experimental.

OBJECTIVES

To investigate and compare static lung volumes and breathing patterns in persons with a cervical spinal cord lesion during breathing at rest, ordinary deep breathing, positive expiratory pressure (PEP) and inspiratory resistance-positive expiratory pressure (IR-PEP) with and without an abdominal binder (AB).

SETTING

The outpatient clinic at the Spinal Unit at Sahlgrenska University Hospital, Goteborg, Sweden.

METHOD

The study group consisted of 20 persons with complete cervical cord lesion at C5-C8 level. Breathing patterns and static lung volumes with and without an AB were measured using a body plethysmograph.

RESULTS

: With an AB, static lung volumes decreased, vital capacity increased, breathing patterns changed only marginally and functional residual capacity remained unchanged during PEP and IR-PEP.

CONCLUSION

Evidence supporting the general use of an AB to prevent respiratory complications by means of respiratory training is questionable. However, the interindividual variation in our results indicates that we cannot rule out that some patients may benefit from the treatment.

Bronchiolar airflow impairment after lung transplantation: an early and common manifestation

BACKGROUND

Bronchiolitis obliterans syndrome (BOS) is the major limitation to long-term survival after lung transplantation (LT). In this study we investigate the extent and frequency of airflow limitation after LT and its value for the diagnosis of BOS.

METHODS

Flow-volume measurements were analyzed retrospectively in 36 recipients of a bilateral LT, with a median follow-up of 32.9 months. The prevalence and onset of a decline of FEV(1), FEF(25), FEF(50), FEF(75) and MMEF(75/25) were evaluated and subsequently related to the occurrence of Grade 1 BOS.

RESULTS

Grade 1 BOS was diagnosed in 16 recipients at a median of 218 (range 88 to 1,007) days after LT. A persistent and significant decrease in FEV(1), FEF(25), FEF(50), FEF(75) and MMEF(75/25) was observed in 23, 24, 30, 32 and 29 patients, respectively. In those patients developing BOS during follow-up this decrease was determined at 147 (55 to 657), 130 (78 to 932), 110 (21 to 573), 103 (32 to 657) and 121 (32 to 657) days after LT (p < 0.0005), respectively. The respective predictive values of these parameters for the occurrence of Grade 1 BOS (within 120 days) were 88%, 60%, 50%, 35% and 41%.

CONCLUSION

Bronchiolar dysfunction is a common and early finding after LT. The decrease of FEV(1) in BOS is often preceded by a decrease of bronchial airflow. Airflow markers may be used as an early warning sign for the development of BOS, although their predictive values are moderate.

Critical care of spinal cord injury

STUDY DESIGN

Review article.

OBJECTIVES

To review the pathophysiology and management of the pulmonary and hemodynamic derangements that occur after acute spinal cord injury.

SUMMARY OF BACKGROUND DATA

Acute spinal cord injury is often associated with alterations in pulmonary and cardiovascular function that require treatment in the intensive care unit.

METHODS

Review of published reports.

RESULTS/CONCLUSION

Careful attention to the support of the pulmonary and cardiovascular systems can reduce the morbidity associated with acute spinal cord injury. Pulmonary function decreases markedly in the immediate postinjury period but improves in the subsequent weeks, allowing most patients with injury levels at C4 and below to be weaned from ventilatory support. Bradycardia and hypotension often accompany acute spinal cord injury, and management strategies are reviewed. The prophylaxis and diagnosis of thromboembolic disease are reviewed.

Cervical spinal cord injury alters the pattern of breathing in anesthetized rats

The mechanisms by which chronic cervical spinal cord injury alters respiratory function and plasticity are not well understood. We speculated that spinal hemisection at C(2) would alter the respiratory pattern controlled by vagal mechanisms. Expired volume (V(E)) and respiratory rate (RR) were measured in anesthetized control and C(2)-hemisected rats at 1 and 2 mo postinjury. C(2) hemisection altered the pattern of breathing at both postinjury time intervals. Injured rats utilized a higher RR and lower V(E) to maintain the same minute ventilation as control rats. After bilateral vagotomy, the pattern of breathing in injured rats was not different from controls. The frequency of augmented breaths was higher in injured rats at 2 mo postinjury before vagotomy; however, the V(E) of augmented breaths was not different between groups. In conclusion, C(2) hemisection alters the pattern of breathing at 1 and 2 mo postinjury via vagal mechanisms.

Involvement of peripheral airways during methacholine-induced bronchoconstriction after lung transplantation

Previous studies have shown that the presence of nonspecific bronchial hyperreactivity (NSBHR) in transplanted subjects is associated with the development of bronchiolitis obliterans, which suggests that NSBHR in these subjects may involve the peripheral airways. We investigated this question by studying the effects of methacholine on the distribution of ventilation using single-breath washouts in 15 heart-lung transplant recipients; 17 nontransplanted subjects with NSBHR were studied for comparison. All subjects had normal baseline lung function, and seven transplanted subjects displayed NSBHR. Methacholine induced a similar decline in FEV1 and specific airway conductance in the two groups. In contrast, whereas methacholine produced similar increases in the slope of the alveolar plateau for SF6 (SSF6) and He (SHe) in the nontransplanted subjects, it always produced greater increases in SHe than SSF6 in the transplanted subjects. This suggests that in the latter, methacholine-induced bronchoconstriction made the distribution of ventilation more heterogeneous in peripheral airways. This involvement of small airways may help in understanding why assessing bronchial reactivity in transplanted subjects provides information on the presence of a pathologic process affecting the bronchioles, and hence on the risk of progression to bronchiolitis obliterans.

Lung mechanics in individuals with spinal cord injury: effects of injury level and posture

Individuals with spinal cord injury (SCI) exhibit reduced lung volumes and flow rates as a result of respiratory muscle weakness. These features have not, however, been investigated in relation to the combined effects of injury level and posture. Changes in forced vital capacity (FVC), forced expiratory volume in 1 s (FEV(1)), FEV(1)/FVC, forced expiratory flow at 50% vital capacity (FEF(50)), inspiratory capacity (IC), and expiratory reserve volume (ERV) were assessed by injury level in the seated and supine positions in 74 individuals with SCI. The main findings were 1) FVC, FEV(1), and IC increased with descending SCI level down to T(10), below which they tended to level off; 2) supine values of FVC and FEV(1) tended to be larger in the supine compared with the seated posture down to injury level T(1), caudad to which they were less than when seated; 3) IC increased proportionately more down to injury level L(1), below which it declined slightly and plateaued; 4) ERV was measurable even at high cervical injuries, was generally smaller in the supine position, reached peak values in both positions at T(10) injury level, and then rapidly declined at lower levels; 5) when subjects were separated according to current, former, and never smokers, only formerly smoking paraplegic individuals demonstrated spirometric values significantly less than paraplegic individuals who never smoked. Changes in spirometric measurements in SCI are dependent on injury level and posture. These findings support the concept that the increase in vital capacity in supine position is related to the effect of gravity on abdominal contents and increase in IC.

Healing of bronchial allografts in pigs

Our purpose was to investigate the healing of bronchial grafts in a porcine experimental model. Via left thoracotomy, a 2.5 cm long bronchial stump was anastomosed back to the same animal (autograft) or to another pig (allograft). Autotransplanted bronchi (six pigs) healed very well without infection. Allotransplantation without immunosuppression (eight pigs) was followed in all cases by rejection with formation of major bronchopleural fistula. After allotransplantation with triple-drug immunosuppressive medication (seven pigs), three pigs showed infection-free healing, but the anastomoses were slightly stenosed at the time of sacrifice (mean 30 d), while four had bronchopleural fistula. The study thus showed the healing ability of totally avascular bronchial graft in pigs to be very good when it is autotransplanted, but poor when allotransplanted without immunosuppressive treatment.

Effects of abdominal strapping on forced expiration in tetraplegic patients

Patients with traumatic transection of the lower segments of the cervical cord contract the clavicular portion of the pectoralis major during forced expiration and cough, and the rise in intrathoracic pressure resulting from this contraction produces dynamic airway compression in many patients. Because the abdominal muscles are paralyzed, however, there is paradoxical expansion of the abdomen, which may reduce the rise in intrathoracic pressure and the degree of airway collapse. To evaluate the magnitude of this effect, we measured expiratory flow rate (Vexp) and esophageal pressure (Pes) during a series of forced expiratory vital capacity maneuvers and constructed isovolume-pressure flow (IVPF) curves before and after abdominal strapping in eight C5-8 tetraplegic subjects. Strapping produced small and inconsistent changes in maximal Vexp and Pes and resulted in the development of small flow plateaus in only four patients. In tetraplegic subjects, abdominal strapping thus has small effects on forced expiration and is unlikely, therefore, to improve the efficiency of cough.

Lung transplantation for lymphangioleiomyomatosis

BACKGROUND

Lymphangioleiomyomatosis is a rare disease of unknown origin that usually leads to progressive deterioration of lung function and eventual death from respiratory failure. It occurs in women of reproductive age and people with tuberous sclerosis. Lung transplantation is a recent therapeutic approach.

METHODS

We conducted a retrospective study by questionnaire of 34 patients, treated at 16 transplantation centers, who underwent lung transplantation for end-stage lymphangioleiomyomatosis between 1983 and 1995.

RESULTS

Of the 34 patients, 27 received single-lung transplants; 6, bilateral transplants; and 1, a heart-lung transplant. As of August 31, 1995, the actuarial survival calculated by the Kaplan-Meier method was 69 percent after one year and 58 percent after two years. Eighteen patients were alive 33 +/- 20 months (range, 3 to 74) after transplantation. Forced expiratory volume in one second increased from 24 +/- 12 percent of the predicted value before transplantation to 48 +/- 16 percent six months after transplantation. Five early deaths (within one month) were due to hemorrhage (in one patient), acute lung injury (in three), and dehiscence of the bronchial anastomosis (in one). Eleven late deaths (after one month) were due to infections (in eight patients), bronchiolitis obliterans (in two), and metastatic nephroblastoma (in one). Disease-associated problems were extensive pleural adhesions in 18 patients, leading to moderate-to-severe intraoperative hemorrhage in 4; pneumothorax in the native lung after single-lung transplantation in 6 patients; postoperative chylothorax in 3; and recurrent lymphangioleiomyomatosis in the allograft in 1 patient, who died of disseminated aspergillosis.

CONCLUSIONS

Although disease-related complications are frequent, lung transplantation can be a valuable therapy for patients with end-stage lymphangioleiomyomatosis.

The effect of continuous positive airway pressures on lung volumes in tetraplegic patients

Continuous positive airway pressure (CPAP) is widely advocated for the treatment of respiratory complications. However the effects of CPAP on the respiratory function of tetraplegic patients have not yet been investigated. The purpose of this study was to examine the effects of breathing with different levels of CPAP on the relationship between closing volume (CV) and functional residual capacity (FRC) in ten recently injured, but otherwise healthy tetraplegic patients with lesions between the fourth and eighth cervical segments. Lung volumes were measured before, during and after 32 min of zero end-expiratory pressure and 5 and 10 cm H2O of CPAP. FRC was measured by the open-circuit nitrogen washout method and CV was measured by the single breath nitrogen washout method. FRC was unaffected by zero end-expiratory pressure, but both 5 cm H2O and 10 cm H2O of CPAP caused significant increases in FRC. FRC returned to pre-CPAP values by the first minute after removal of 5 and 10 cm H2O of CPAP. We were unable to measure CVs in any subjects. It was concluded that 5 and 10 cm H2O of CPAP increase FRC in healthy tetraplegic individuals, but that these increases are rapidly lost with the subsequent removal of CPAP. These results suggest that CPAP may have a role in the treatment and prevention of respiratory complications in tetraplegics.

[Ventilation pattern at rest and respiratory response to hypercapnic stimulation after lung transplantation]

We aimed to assess breathing pattern at rest by studying occlusion pressure after the first 100 miliseconds (P0.1) and ventilatory response to hypercapnia after lung transplantation. Seven transplanted patients were compared with a control group of 7 healthy subjects. The breathing pattern at rest after transplantation included a significant increase in minute volume (VE) at the expense of an increase in tidal volume (VT) and above all of mean inspiratory flow (VT/Ti). There were no significant differences in ventilatory response to hypercapnia between the 2 groups, although the response curves of both VE and VT to CO2 tended to slope downward. These results can be explained by the mechanics of ventilation in some subjects studied and by the effect of pulmonary denervation on ventilatory control.

Lung transplantation

Solid-organ transplantation has flourished during the last decade, with transplantation of heart and lungs becoming available to patients with end-stage cardiac or pulmonary diseases. The first lung transplant was performed in 1963 on a 58-year-old man with bronchogenic carcinoma. He survived for 18 days. During the next two decades, approximately 40 lung transplant procedures were attempted without success. These early attempts at lung transplantation were unsuccessful because of the development of lung rejection, anastomotic complications, or infection in the transplant recipients. In the early 1980s, human heart-lung transplantation was successfully performed for the treatment of pulmonary vascular disease. After this procedure, single-lung transplantation for the treatment of end-stage interstitial lung disease and obstructive lung disease was developed. More recently, the technique of double-lung transplantation has come into existence. This article reviews various aspects of lung transplantation, including immunosuppression, lung graft preservation, the various surgical techniques and types of lung transplant procedures available, recipient and donor selection criteria, and postoperative care of the transplant recipient. In addition, infectious and noninfectious complications seen in this particular patient population, including acute and chronic rejection, will be discussed.

Diagnosis of unilateral mainstem bronchial obstruction following single-lung transplantation with routine spirometry

Single-lung transplantation has become a treatment option for many patients with advanced pulmonary disease. Recent advances in surgical technique and refined immunosuppressive regimens have led to improvement in long-term outcomes, but postoperative complications, including airway disorders, remain problematic. Serial spirometry with flow-volume loops is sensitive in detecting early small-airway disease associated with lung allograft rejection or bronchiolitis obliterans, but its role in the diagnosis of large-airway disease in the posttransplantation setting has not been delineated. In this report, we describe a novel alteration in the configuration of the flow-volume loop in a patient who developed unilateral mainstem bronchial obstruction following single-lung transplantation for severe emphysema. Surveillance spirometry performed 6 weeks after transplantation demonstrated a new initial plateau in the maximal expiratory flow-volume curve suggestive of a variable intrathoracic airway obstruction. This unique aberration in the flow-volume curve sheds new insight into the physiologic abnormalities of spirometry in patients receiving lung transplants.

Single lung transplantation for primary pulmonary hypertension without cardiopulmonary bypass

We report the first case, to our knowledge, of single lung transplantation for primary pulmonary hypertension carried out without cardiopulmonary bypass. This operation seems to be possible even if the right ventricular ejection fraction is low (0.17) and the pulmonary vascular resistance very high (1,096 dynes.s.cm5). Since 1981, heart-lung transplantation has been successfully performed in patients with primary pulmonary hypertension. If heart-lung transplantation results in resolution of pulmonary hypertension, the incidence of obliterative bronchiolitis is significant in heart-lung transplantation recipients. Single lung transplantation has been performed for end-stage interstitial and obstructive lung disease but has not been considered a good option for primary pulmonary hypertension due to concerns that a single transplanted lung would be unable to cope with the entire blood flow. However, recently single lung transplantation has been performed for primary pulmonary hypertension, the risk of obliterative bronchiolitis remaining unknown. The purpose of this communication is to report one case of single lung transplantation for primary pulmonary hypertension and the feasibility of this operation without the use of cardiopulmonary bypass, if cardiopulmonary bypass is thought to be dangerous.

Breathing pattern adjustments during the first year following cervical spinal cord injury

The alterations in lung function and breathing pattern were examined in 6 quadriplegics at 3, 6 and greater than 12 months post injury, and were compared to 6 able bodied controls. Subjects were studied in both the seated and supine positions. Functional residual capacity (FRC), forced vital capacity (FVC), inspiratory capacity (IC), and maximum mouth pressure (Pimax) at FRC were measured. Total lung capacity (TLC) and residual volume (RV) were calculated. Resting breathing pattern was assessed for 20 minutes from a spirogram derived from summed rib cage and abdominal strain gauge signals. At 3 months in quadriplegics, TLC was reduced (p less than 0.05), RV increased (p less than 0.01) and FRC was normal in sitting; in supine, only TLC was reduced (p less than 0.05); Pimax was decreased (p less than 0.01) in both positions in quadriplegics at 3 months, but increased over the first year in the seated position (p less than 0.01). There were no alterations in breathing pattern at any time interval in quadriplegics in supine. In contrast, at 3 months post injury in sitting, expiratory time (Te) was shortened (p less than 0.05), tidal volume (Vt) was decreased, and heart rate elevated as compared to controls (p less than 0.05). Inspiratory time (Ti) was not significantly shortened at 3 months in quadriplegics, but a lengthening of Ti occurred between 3 and 6 months (p less than 0.025) resulting in increased Vt, and heart rate decreased to normal. Vt/Ti was reduced, and did not alter with time. The lengthening of Ti/Ttot observed in supine in control subjects (p less than 0.025), was not observed in quadriplegics. Quadriplegics sighed as frequently in supine as did controls at all stages post injury, whereas they decreased sighing frequency in sitting at 3 and 6 months post injury (p less than 0.05). The improvement in resting breathing pattern observed in quadriplegics in sitting with time, may be due to increased accessory muscle function, improved chest wall stability and thoracoabdominal coupling, or a combination of these factors. It is also possible that the alterations in breathing pattern were a response to cardiovascular adjustments occurring in the same time frame. Quadriplegics retain the sigh reflex, but do not take as many big breaths in sitting as they do in supine, probably due to the increased work of breathing in the seated posture.

Denervation of transplanted porcine lung causes airway obstruction

Lung transplantation can be complicated by a form of small airway obstruction known as bronchiolitis obliterans. We tested the hypothesis that lung denervation causes small airway obstruction in young pigs (10 +/- 1 weeks). Control pigs had an innervated native lobe, and study pigs had either a denervated native lobe or a denervated transplant lobe. Transplanted pigs received standard immunosuppression. At 10 weeks we measured isolated left lobe pulmonary mechanics. Dynamic resistance in both study groups was significantly higher than in the lobectomy group, whereas dynamic compliance in both study groups was significantly lower than in the lobectomy group. No significant difference in resistance or compliance was noted between the transplant and reimplant groups. Histologic changes consistent with rejection were noted in the transplant lobes. We conclude that the small airway obstruction noted in this model is due to operative denervation rather than to immunosuppression or rejection.

Single lung transplantation for primary pulmonary hypertension

Single lung transplantation has become a therapeutic option for end-stage interstitial lung disease and obstructive lung disease. Our group recently extended this treatment to three patients with primary pulmonary hypertension. All patients had marked decreases in pulmonary artery pressures and pulmonary vascular resistance and increases in cardiac output following single lung transplantation. Spirometry, lung volumes, and diffusion capacity were not different in comparison to preoperative studies. Quantitative ventilation-perfusion scans revealed the majority of perfusion distributed to the transplanted lung, with ventilation approximately equally divided between the native and the transplanted lung. Despite ventilation-perfusion imbalance, there was no resting hypoxemia and there was no arterial oxygen desaturation with exercise. One patient expired on the 30th postoperative day due to cytomegalovirus infection of the lungs. In the remaining two patients, maximum exercise capacity following transplantation was near normal in one recipient and reduced in the second recipient. Of note, there was no evidence of ventilatory limitation or impaired oxygenation during exercise in these two recipients. Although an exaggerated exercise ventilatory response was present, this did not limit exercise performance. This report supports the use of single lung transplantation for the treatment of primary pulmonary hypertension.

Bronchial responsiveness after human heart-lung transplantation

We evaluated bronchial responsiveness to inhaled albuterol (salbutamol), ipratropium bromide, methacholine, and propranolol in eight heart-lung transplant (HLT) recipients 2.3 +/- 1.5 months (mean +/- SD) (range, 1 to 4.5 months) after HLT. All patients had a restrictive ventilatory defect but none had airflow limitation (FEV1/FVC = 0.93 +/- 0.05) (range, 0.86 to 0.97). Specific airway conductance (sGaw) improved significantly with both albuterol (p less than 0.01) and ipratropium bromide (p less than 0.01) but FEV1 did not. Only one HLT patient had bronchoconstriction with propranolol, whereas all but one were hyperresponsive to methacholine. Prior inhalation of ipratropium bromide blocked the response to methacholine (p less than 0.005). Serial methacholine provocation tests performed in seven long-term survivors of HLT 24.6 +/- 16.0 months (range, 12 to 51 months) after HLT revealed no time-dependent evolution of bronchial hyperresponsiveness to methacholine. Limited maximal airway narrowing to methacholine was seen in five HLT recipients who showed a 29 +/- 4 percent (range, 23 to 35 percent) fall in FEV1 compared with two patients who did not achieve a plateau with a 47 percent and 63 percent fall in FEV1, respectively. These results further our understanding of bronchial responsiveness in the denervated transplanted lung. The findings of stable hyperresponsiveness to methacholine over a prolonged time interval, limited maximal airway narrowing to methacholine, and blockade of methacholine hyperresponsiveness by ipratropium bromide support the concept of denervation hypersensitivity of muscarinic receptors.

Ventilatory compensation for changes in posture after human heart-lung transplantation

We have studied the contribution of vagal pulmonary receptors to the stability of breathing during postural changes in humans. Quiet breathing was quantified in the seated and the supine postures in 10 patients with chronic pulmonary denervation due to heart-lung transplantation and 10 age and sex matched normal controls. In the vast majority of patients and normal subjects frequency histograms for tidal volume and mean inspiratory flow rate were virtually superimposed seated and supine. There were no significant differences in the mean levels of respiratory variables between postures in either group (except for mean inspiratory flow rate in the patients which was slightly greater seated than supine). Experiments performed on a tilt table in two additional patients showed that the ventilatory response to postural changes was immediate. In addition, the response was maintained after blockade of intact tracheal stretch receptors with aerosolized lidocaine. These results indicate that adequate ventilatory compensation during postural changes does not depend on vagal afferent information arising in intrapulmonary or tracheal airway stretch receptors. The appropriate receptors may be diaphragmatic Golgi tendon organs.