The art of interface. Tools for administering noninvasive ventilation

BACKGROUND

Since the choice of interface plays a large role in the effectiveness of noninvasive ventilation, there is a need for information about what is available, how to make a selection, what to do when a problem occurs, and how to provide proper care and monitoring.

MATERIAL AND METHODS

Here we will present some of the different types of interfaces available, different problems presented by each, and guidelines for making choices among them.

Chronotropic competence in endurance trained heart transplant recipients: heart rate is not a limiting factor for exercise capacity

OBJECTIVES

The purpose of this study was to show that the chronotropic potential of the well trained heart transplant recipient (HTR) does not limit exercise capacity.

BACKGROUND

Chronotropic incompetence is considered to be the main limiting factor of the functional capacity of heart transplant recipients. However, no systematic study had been published on patients who had spontaneously undergone heavy endurance training for several years.

METHODS

Heart rate (HR) and respiratory gas exchanges (VO2, VCO2, VE) were measured in 14 trained HTRs (T-HTRs) during exercise tests on a bicycle, on a treadmill and by Holter electrocardiography during a race.

RESULTS

Peak values observed in T-HTRs during the treadmill test were higher than those reached during the bicycle test (VO2peak: 39.8+/-6.9 vs. 32.5+/-7.8 ml x kg(-1) x min(-1), p < 0.001; HRpeak: 169+/-14 vs. 159+/-16 bpm, p < 0.01). During treadmill exercise VO2peak and HRpeak values observed were very close to the mean predicted VO2pmax and HRpmax. The maximum heart rate during the race (HRrace) was greater than HRpeak values during the treadmill test (179+/-14 vs 169+/-14 bpm, p < 0.01) and slightly above the mean predicted values (HRrace/HRpmax X 100 = 101+/-10%). The treadmill exercise test yields more reliable data than does the bicycle test.

CONCLUSIONS

Extensive endurance training enables heart transplant recipients to reach physical fitness levels similar to those of normal sedentary subjects; heart rate does not limit their exercise capacity.

[Intra-aortic covered endoprosthesis]

Because of the risk and complications related to surgery of the aorta, the development of new, less invasive endovascular techniques has resulted in a certain enthusiasm for these new treatments on the part of physicians and industry. The insertion of aortic stents allows the treatment of almost one half of aneurysm of the infrarenal abdominal aorta and descending aorta. The results appear to demonstrate the medium-term reliability and efficacy of these new techniques with a lower morbidity-mortality rate than that of conventional surgery. However, preoperative and intraoperative imaging plays an essential role in the success of these new methods. Finally, although the medium-term results are encouraging, the long-term outcome of these new materials is unknown, which justifies close surveillance of these patients and prospective comparative studies.

Heart retransplantation: a 23-year single-center clinical experience

BACKGROUND

The main causes of allograft failure after cardiac transplantation are primary graft dysfunction, intractable acute rejection, and coronary graft disease. Despite the important progress in the last several years in graft preservation, surgical techniques, immunosuppression, and treatment of coronary graft disease, retransplantation in selected cases is the only way to achieve long-term recipient survival.

METHODS

We compare here in a case-control study 24 retransplantations with 47 first transplants in patients matched for date of transplantation.

RESULTS

Between 1973 and 1996, 1,063 patients underwent cardiac transplantation in our institution. In this cohort, 22 patients had a total of 24 retransplantations (2 second-time retransplantations). The causes of retransplantations were primary graft failure (n=4), acute rejection (n=7), coronary graft disease (n=11), and miscellaneous (n=2). Survival at 1 and 5 years of patients with retransplantations is 45.5% and 31.2%, and survival of control patients is 59.4% and 38.8% (p=0.07). An interval between first transplantation and retransplantation shorter (n=11) or longer (n=13) than 1 year is associated with a 1-year survival of 27.3% and 61.5% and a 4-year survival of 27.3% and 46%, respectively (not significant). Intervals shorter than 1 year between first transplantation and retransplantation were exclusively secondary to primary graft failure or intractable acute rejection.

CONCLUSIONS

In the face of lack of donor grafts, these and other data indicate that retransplantation should be considered cautiously, especially when the interval between the first transplantation and retransplantation is short.

[The cardiowest total artificial heart: experience of 29 cases]

The authors studied the outcome of multi-organ failure in 29 patients with terminal cardiac failure and maintained with a Cardiotest total artificial heart whilst waiting for cardiac transplantation. Pre-implantation organ dysfunction was defined by the following criteria; assisted respiration of over 3 days, total billirubin and creatinine levels of over 2 mg/dL, a platelet count of less than 80,000/mL or a prothrombin ratio of less than 50% and central nervous system disturbances. Fourteen patients died during the period of circulatory assistance and 71% of deaths were due to multi-organ failure. Pre-implantation plasma total bilirubin levels were significantly higher in patients who died of multi-organ failure (p = 0.04). Eighty per cent of patients who died of multi-organ failure had at least 3 criteria of organ dysfunction before implantation of the artificial heart compared with only 37% in the other patients (p = 0.04). Finally, systemic vascular resistances before implantation were significantly lower in patients who died of multi-organ failure. The results of this study suggest that multi-organ failures does not develop during the period of circulatory assistance but represents an aggravation of a preexisting morbid condition. This observation should lead to a limitation of the indications of total circulatory assistance in some cases and, above all, to earlier intervention before multi-organ failure becomes irreversible.

Haemostatic system activation and prediction of vascular events in patients presenting with stable peripheral arterial disease of moderate severity. Royat Study Group

This study reports on the predictive value of some haemostatic factors [fibrinogen, factor VII and plasminogen activator inhibitor (PAI)], a marker of endothelial damage (soluble thrombomodulin) and several markers of haemostatic system activation (factor VIIa, prothrombin fragment 1+2, thrombin-antithrombin complexes and D-dimers) on the incidence of vascular events in male, non-diabetic patients with chronic ischaemia of the lower limbs. The patients (n=324) were recruited consecutively in the thermal resort of Royat, France. The low incidence of death from vascular causes during the 2-year survey period (two patients) and the high percentage of former smokers (71%) indicated that this population of patients was affected by an arteriopathy of moderate intensity. After 2 years' follow-up, vascular events had occurred in 51 patients. The clinical and biological profiles did not differ significantly between patients with and without vascular events. However, the risk of vascular events during the 2 years of follow-up was significantly higher in those with high levels of PAI antigen and thrombin-antithrombin complexes. Thus, even in a population of patients with only moderately severe arteriopathy, high levels of thrombin-antithrombin complexes and PAI are predictive of vascular complications.

Conduct disorder among children in an informal settlement. Evaluation of an intervention programme

OBJECTIVES

This study aimed to evaluate the effectiveness of a 12-week intervention programme for conduct-disordered boys aged 10-16 years.

DESIGN

A descriptive study comparing a group of boys who participated in an intervention programme with a non-participant group.

SETTING

All the participants were resident in Khayelitsha and the programme was conducted at Empilweni, a community mental health project in Site C, Khayelitsha.

SUBJECTS

Nine of the 15 boys who were referred to Empilweni for serious conduct problems participated in the intervention; the remaining 6 were non-participants.

OUTCOME MEASURES

The New York Teacher Rating Scale (NYTRS) and selected modules of the Diagnostic Interview Schedule for Children (DISC) were administered before and immediately after the treatment programme, and again after a 6-month interval.

RESULTS

Six months after the intervention, the treatment group showed a significant reduction in defiance, physical and delinquent aggression, as well as additional conduct problems. The non-treatment group only showed a significant reduction in defiance.

CONCLUSIONS

The study results suggest that short-term community-based group therapy may be effective in treating delinquent behaviour among boys in an informal settlement. The feasibility of promoting such interventions as part of national violence prevention programmes requires serious consideration.

Post-traumatic stress disorder in children exposed to violence

OBJECTIVES

To investigate to what extent local children exposed to community violence develop post-traumatic stress disorder (PTSD), whether the symptom profile is typical or atypical, and how detection can be improved.

DESIGN

A cross-sectional study of two samples of children with a high risk of past exposure to violence.

SETTING AND SUBJECTS

Sixty Xhosa-speaking children aged 10-16 years; 30 from the Children's Home which serves Khayelitsha, and 30 from a school in a violent area of Khayelitsha.

OUTCOME MEASURES

A shortened version of the Survey of Exposure to Community Violence (SECV) was administered to determine exposure to violence. Structured questionnaires and a clinical assessment were used to elicit symptoms and make psychiatric diagnoses.

RESULTS

All 60 children reported exposure to indirect violence, 57 (95%) had witnessed violence, and 34 (56%) had experienced violence themselves. Twenty-four (40%) met the criteria for on or more DSM-III-R diagnoses and 13 (21.7%) met the criteria for PTSD.

CONCLUSIONS

Community violence places children at a high risk of developing serious psychiatric disorders and many children develop PTSD. None of the children in the school sample had received intervention prior to the study, pointing towards an urgent need for increased community and professional awareness of children at risk.

[Cystic adventitial disease: importance of computed tomography in the diagnostic and therapeutic management]

PURPOSE

Popliteal artery entrapment and adventitial cystic disease are the main causes of claudication in young patients. Adventitial cystic disease is a rare vascular pathology mostly affecting the popliteal artery but other localisations have been reported. Diagnosis and therapeutic management of adventitial cystic disease and particularly percutaneous aspiration are presented.

MATERIALS AND METHODS

The authors report six cases (four men and two women; mean age: 55) of CAD of the popliteal artery (n = 4) and unusual cases in the femoral artery (n = 1) and in the femoral vein (n = 1) explored by sonography, computed tomography (CT), magnetic resonance imaging (MRI) and angiography. Five patients were initially treated by CT-guided aspiration and one with endoprosthesis.

RESULTS

Sonography, CT or MRI are more useful to establish the diagnosis because these techniques can directly visualize the arterial wall. All these patients but one have been treated by percutaneous method with a good functional outcome but surgical intervention was necessary for two of them because of cysts recurrence.

CONCLUSION

Our experience suggests that percutaneous CT-guided aspiration is the first treatment option for small cysts but close long-term follow-up is necessary to detect recurrence.

Accumulation of trimethoprim, sulfamethoxazole, and N-acetylsulfamethoxazole in fish and shrimp fed medicated Artemia franciscana

In a previous paper (H.J. Nelis, P. Léger, P. Sorgeloos, and A. P. De Leenheer, Antimicrob. Agents Chemother. 35:2486-2489, 1991) it was reported that two selected antibacterial agents, i.e., trimethoprim and sulfamethoxazole, can be efficiently bioencapsulated in nauplii of the brine shrimp Artemia franciscana for administration to fish. This follow-up study showed that larvae of the sea bass and the turbot as well as postlarvae of the white shrimp accumulate the therapeutic agents in high quantities when fed medicated A. franciscana. To monitor their levels as a function of time, the liquid chromatographic method originally developed for the analysis of A. franciscana was modified with respect to chromatography, internal standardization, and sample pretreatment. The levels of trimethoprim ranged from 1 to 7 micrograms/g (sea bass), 1 to 13 micrograms/g (turbot), and 4 to 38 micrograms/g (white shrimp). The corresponding values for sulfamethoxazole were 0.3 to 4 micrograms/g (sea bass), 1 to 42 micrograms/g (turbot), and 4 to 35 micrograms/g (white shrimp). Only the two fish species, unlike the shrimp, metabolized the latter to N-acetylsulfamethoxazole (concentration range, 1 to 10 micrograms/g). These data suggest the potential of the bioencapsulation of therapeutic agents in live food as a tool to control infectious diseases in aquaculture. A preliminary challenge test also confirmed the in vivo efficacy of this approach.

Long-term noninvasive ventilation for patients with thoracic cage abnormalities

Long-term noninvasive ventilation offers the patient with thoracovertebral deformities, including deformities that result from the severe skeletal and chest-wall sequelae of tuberculosis, what long-term oxygen therapy has offered patients with chronic obstructive pulmonary disease: improved survival and prevention or alleviation of cor pulmonale. Long-term noninvasive intermittent positive pressure ventilation, particularly nocturnal use, has little inconvenience, because ventilation during the night often suffices. Major advantages include correction of hypoventilation during autonomous breathing time that is usually sufficient to permit patients to resume their activities of daily living without need for ventilatory assistance during the day and efficacy comparable to that of intermittent positive pressure ventilation via an indwelling tracheostomy tube, without the inconveniences (tracheostomy is always available if necessary).

Heart transplant for the failing ischaemic ventricle

Clinical application of heart transplantation goes beyond 28 years experience. Ischaemic heart diseases remain, with idiopathic cardiomyopathies, the main indications for cardiac transplant. A combination of haemodynamic, contractile and viability measurements may be useful to choose between transplant and coronary revascularization for the failing ischaemic ventricle. Advances in the detection of early rejection, improved organ preservation procedures, and the introduction of new immunosuppressive therapy protocols have produced dramatic results in heart transplantation. Late graft atherosclerosis remains a serious threat despite retransplantation and, in some cases, mechanical circulatory support.

[Treatment with endoprosthesis of the pathology of the descending thoracic artery]

Surgery and medical treatment have been classically accepted as the therapy of choice in some diseases of the thoracic aorta. Recently, treatment with endoprosthesis has emerged as a useful technique in the pathology of the descending thoracic aorta. The type of endoprosthesis, indications and experimental and clinical results are discussed.

Physiology of univentricular versus biventricular support

Right ventricular failure unresponsive to pharmacologic treatment occurs in approximately 20% to 30% of patients supported with a left ventricular assist device (LVAD). The effect of the assistance on right ventricular function is highly controversial. Increased venous return produced by an LVAD can affect right ventricular function by increasing preload. On the other hand, an LVAD can improve the filling of the right ventricle by unloading the left ventricle, reducing its chamber size and shifting the septum back to the left. Right ventricular function is highly afterload dependent, the ventricular function depending on the pulmonary vascular resistance. With a normal pulmonary vascular bed, the LVAD can improve right ventricular function by reducing right ventricular afterload. If there is a fixed high pulmonary pressure, however, the LVAD can increase right ventricular afterload and volume. We conclude that the right ventricle is dispensable if the pulmonary vascular bed is normal.

[Aneurysms of the popliteal artery. Intravascular bypass using the internal saphenous vein]

We used the internal saphenous vein to create an intravascular bypass for the treatment of aneurysms of the popliteal artery. The saphenous vein was positioned within the lumen of the aneurysmal popliteal artery and in the superficial femoral artery at its origin. Two end-to-end anastomoses were made including the venous wall within the suture. This new surgical technique is based on 3 criteria. i) anatomic: the venous bypass follows the exact path as the artery since it is situated within the lumen; ii) haemodynamic: end-to-end anastomoses are used to avoid turbulence created with end-to-side sutures; iii) histologic: the venous endothelium protects better against thrombus formation ensuring good long-term permeability.

Clinical experience with a total artificial heart as a bridge for transplantation: the pitie experience

Since April 1986, 82 patients have received a pneumatic total artificial heart, 62 a JARVIK-7, and 20 a Cardiowest. The duration of support ranged from less than 1 day to 603 days (mean duration: 27 +/- 82). The indications were for acute shock (38 cases) or for chronic deterioration on the transplant waiting list (44 cases). The etiology was mainly due to idiopathic and ischemic cardiomyopathy. With the help of our scoring system, we divided our patients in three groups: Chronic Implantation, represented by two females staying on device for 6 and 19 months, respectively; a High-Risk group of 29 patients characterized by high-risk indications; graft failure, rejection, postcardiotomy patient, postpartum cardiomyopathy, and valvular and congenital reoperation. In addition, the dilated and ischemic cardiomyopathy patients with a score over 6 were included in this group; and an Elective Indication group (51 patients) represented all of the dilated and ischemic cardiomyopathy patients with a score under 6. Due to the shortage of donors, our criteria for transplantation are very strict. Transplants should be made only in cases of hemodynamic stability, on an extubated patient with normal renal and liver functions, without coagulation problems or infection. With such criteria, in the high-risk group, only four patients could be transplanted and of these two are still alive. In contrast, in the elective group, 31 were transplanted (61%), and 71% of these patients were discharged. The rate is improved in the most recent cases, with 90% of the Cardiowest patients being survivors.

Sleep fragmentation in kyphoscoliotic individuals with alveolar hypoventilation treated by NIPPV

Intermittent positive pressure ventilation (IPPV) delivered via nasal access can normalize alveolar ventilation for individuals with chronic alveolar hypoventilation (CAH) due to neuromuscular disease, spinal cord injury, or skeletal deformity. The purpose of this study was to evaluate the effect of nasal IPPV (NIPPV) air leakage-associated oxyhemoglobin desaturations (dSATs) on the sleep efficiency of kyphoscoliotic individuals with severe pretreatment nocturnal dSATs. Only individuals using nocturnal NIPPV without supplemental oxygen therapy were studied. Seven such individuals were able to maintain PaO2 greater than 60 mm Hg without supplemental oxygen therapy (five had been using oxygen therapy in the pretreatment period), had fewer hospitalizations, and had improvements in symptoms, arterial blood gas values, and nocturnal oxyhemoglobin saturation (SAT) by nocturnal NIPPV. This occurred despite polysomnographically observed sleep disruption and sleep stage changes associated with frequent transient dSATs and massive insufflation leakage. Arousals and dSATs were most frequent during rapid eye movement (REM) sleep with the latter occurring at a frequency of 10/h. The dSATs resulted in brief arousals or lightening of sleep stage 76% of the time. With or without arousal, central nervous system mediated reflex muscular activity occurred to diminish leak and normalize SAT. We conclude that the effectiveness of nocturnal NIPPV is dependent in part on central mediated muscular activity.

Side effects of nasal continuous positive airway pressure in sleep apnea syndrome. Study of 193 patients in two French sleep centers

Nasal continuous positive airway pressure (N-CPAP) is now the treatment of choice for patients with sleep apnea syndrome (SAS). Side effects and adverse reactions have been described with this device. We have therefore systematically studied side effects of N-CPAP in 193 patients recruited consecutively from two French sleep centers (Lyon and Grenoble). Patients were followed up with repeated polysomnography, clinical assessment, and a formal questionnaire about subjective benefits and side effects of treatment. The patients (mean age, 59 +/- 12 years) were obese (body mass index, 32 +/- 7 kg/m2) and had been using N-CPAP for 19 +/- 17 months for moderate to severe SAS (respiratory disturbance index [RDI] = 53 +/- 25/h). The clinical presentation was the same in the two sleep centers. Fifty percent of the patients complained of at least one side effect due to the nasal mask (allergy to the face, air leaks, abrasions of the ridge of the nose). Using individually molded masks, the patients exhibited fewer abrasions of the bridge of the nose (p < 0.01) and had red eyes every morning in only 9% of cases vs 24% for the patients using industrial silicone nasal masks (p < 0.025). Patients with silicone nasal masks also had more allergic reaction to the face (13% vs 5%), but this difference did not reach significance. Dry nose or mouth in the morning affected 65% of the patients. Sneezing and nasal drip were present in more than 35% of the subjects and nasal congestion in 25%. When the patients were separated in two groups, whether or not using a humidifier, no difference was found for any of the side effects described. The clinical presentation as to the clinical benefits obtained from N-CPAP were different when comparing mild vs moderate-to-severe SAS. However, no differences were shown in the two subgroups regarding the side effects due to the nasal mask. The discomfort of the N-CPAP apparatus in terms of noise was described more frequently in the subgroup with mild SAS. We did not observe any correlation between the side effects and the level of pressure used during N-CPAP. The rate of compliance remains high with a daily use of 6.5 +/- 3 h, with 88% of the patients using their device every night. This could be explained by the clinical benefit obtained: only 1% of the patients had no subjective benefit induced by their therapy.(ABSTRACT TRUNCATED AT 400 WORDS)