TRANSLATION AND DETERMINATION OF THE COMPREHENSIBILITY OF A LUGANDA VERSION OF ORAL MUCOSITIS DAILY QUESTIONNAIRE

OBJECTIVE

This study aimed to translate, determine the comprehensibility and examine the linguistic equivalence of a Luganda Oral Mucositis Daily Questionnaire (OMDQ MTS) among patients undergoing chemotherapy.

DESIGN

This was a validation study design in which bilingual patients who were receiving chemotherapy at Uganda cancer institute and had experienced some sort of oral discomfort after the start of their treatment were asked to complete OMDQ MTS Luganda followed by the English version on the same visit. The tools were administered at least two hours apart and had different item order.

RESULTS AND CONCLUSIONS

Fifty participants accepted to take part by completing both versions of OMDQ MTS data. All item mean score differences between the two versions were less than ±0.25. The Cronbach's α for the Luganda and English versions were 0.78 and 0.86 based on standardized items while Guttman's lambada 2 and 3 were 0.89 and 0.79 respectively. A translated Luganda version of OMDQ MTS is reliable and easy to understand. Thus, it has the potential in being used to monitor mucositis among patients undergoing chemotherapy.

Immune response to the hepatitis B vaccine among HIV-infected adults in Uganda

BACKGROUND

Co-infection with hepatitis B virus (HBV) and human immunodeficiency virus (HIV) is common in sub-Saharan Africa (SSA) and can rapidly progress to cirrhosis and hepatocellular carcinoma. Recent data demonstrate ongoing HBV transmission among HIV-infected adults in SSA, suggesting that complications of HIV/HBV co-infection could be prevented with HBV vaccination. Because HBV vaccine efficacy is poorly understood among HIV-infected persons in SSA, we sought to characterize the humoral response to the HBV vaccine in HIV-seropositive Ugandan adults.

METHODS

We enrolled HIV-infected adults in Kampala, Uganda without serologic evidence of prior HBV infection. Three HBV vaccine doses were administered at 0, 1 and 6 months. Anti-HBs levels were measured 4 weeks after the third vaccine dose. "Response" to vaccination was defined as anti-HBs levels ≥ 10 IU/L and "high response" as ≥ 100 IU/L. Regression analysis was used to determine predictors of response.

RESULTS

Of 251 HIV-positive adults screened, 132 (53%) had no prior HBV infection or immunity and were enrolled. Most participants were women [89 (67%)]; median (IQR) age was 32 years (27-41), and 68 (52%) had received antiretroviral therapy (ART) for > 3 months. Median (IQR) CD4 count was 426 (261-583), and 64 (94%) of the 68 receiving ART had undetectable plasma HIV RNA. Overall, 117 (92%) participants seroconverted to the vaccine (anti-HBs ≥ 10 IU/L), with 109 (86%) participants having high-level response (anti-HBs ≥ 100 IU/L). In multivariate analysis, only baseline CD4 > 200 cells/mm3 was associated with response [OR = 6.97 (1.34-34.71), p = 0.02] and high-level response [OR = 4.25 (1.15-15.69)], p = 0.03].

CONCLUSION

HBV vaccination was effective in eliciting a protective humoral response, particularly among those with higher CD4 counts. Half of the screened patients did not have immunity to HBV infection, suggesting a large at-risk population for HBV infection among HIV-positive adults in Uganda. Our findings support including HBV vaccination as part of routine care among HIV-positive adults.

Challenges of Building and Sustaining Radiation Therapy Capacity in Low-Resource Settings: A Case of the Breakdown of Cobalt 60 Teletherapy in Uganda and Lessons Learned

Background and context: The use of radiotherapy in developing countries is slowly gaining momentum but the gains are accompanied by some pitfalls. The breakdown of a teletherapy (cobalt 60) machine in Uganda is an example of the challenges to be considered while expanding access to treatment. It was a major test for the country and the Uganda Cancer Institute the agency of government responsible for provision of cancer services. It attracted a national and international outcry. This unprecedented response was based on the importance a seemingly old equipment in Kampala was playing in the entire region (Kenya, Tanzania, Rwanda, Burundi, Democratic Republic of Congo and southern Sudan). However, the manner in which the crisis was handled demonstrated clearly how to turn a misfortune into an opportunity given the many lessons learnt. Aim: In this paper we aim to highlight how the breakdown of the equipment triggered a major crisis and the response to the crisis resulting in the restoration of services within a reasonable time frame. We also want to show the long-term service modernization and expansion drive this has triggered within Uganda and the entire region. Strategy/Tactics: The restoration process comprised planning, decommissioning, renovation, security and safety systems, procurement of new machine, installation and commissioning. As this was ongoing there was the need for care provision for patient in need. Concurrently undertaken was public reassurance through building confidence and trust in the capacity for speedy restoration of services. Program/Policy process: All these steps were taken collaboratively within country, region and internationally. In the region there was support from the Aga Khan University Hospital Nairobi and internationally, technical support from the IAEA. Outcomes: Service has been fully restored, a new teletherapy cobalt machines installed and commissioned. The machine has modern capabilities compared with the previous. So far more than 200 patients have been treated. The numbers of patients are steadily increasing hence the government has embarked on modernization and expansion of the radiotherapy services in the country. What was learned: The breakdown of Uganda's radiotherapy machines has provided lessons that are important for handling health system operational crisis which may occur as we try to build complex delivery systems. It provided lessons that are important in the drive for expansion of radiotherapy services in developing countries. In particular that benefit of investments in modern equipment transcends national boundaries. Secondly how to limit potential impact of major crisis through regional and international collaboration. Further that the needs of patients is central in crisis management. Finally need to consider pooling infrastructure investments in tackling NCD's such as the East Africa's centre of excellence for skills and tertiary education project of the East African community.

The Role of South-to-South Partnerships in Developing Cancer Services in Africa

Background and context: Despite being a growing public health concern in Africa, access to effective cancer treatment and pain relief is still limited in sub-Saharan Africa. The African Palliative Care Association (APCA) in collaboration with the American Cancer Society and the Ministry of Health of Swaziland have successfully implemented a South-to-South partnership which has facilitated the development and operation of a cancer unit in Mbabane National Hospital. Although the cancer burden continues to rise in Africa, many countries do not have established oncology services. They rely on cancer treatment, care and support through referral to neighboring countries or overseas, which is costly for governments and poses multiple challenges for patients and their families. Until recently, Swaziland has relied on cancer treatment and care in South Africa. This paper presents a model where the Uganda Cancer Institute (UCI) in Uganda has been facilitated to support the establishment of a cancer unit in Swaziland. Aim: The intervention aimed at providing technical assistance to the Ministry of Health of Swaziland to initiate and operate a cancer unit in Mbabane Government Hospital through a formal arrangement with the UCI. Strategy/Tactics: The planning and execution of activities was done by a tripartite of APCA, Uganda Cancer Institute a government entity and the Swazi Ministry of Health. Program/Policy process: Over a period of one year (Decemeber 2016 to December 2017) APCA, through a grant from the ACS formerly engaged the UCI to support the initiation and operation of a cancer unit in Swaziland. This was through expert exchange visits through which on-job training and mentorship was provided to a team of staff at Mbabane Government Hospital, with coordination by the Swaziland Ministry of Health. Experiential visits to Uganda were also organized for the lead pharmacist in Swaziland and a doctor to enable them set up and run a cancer unit in their country. The exchange visits provided a forum for both observation and application of knowledge and skills. Outcomes: A cancer unit was successfully established at Mbabane Government Hospital in Swaziland, which now provides services for patients, with breast cancer and expanding to include other cancers. The Swaziland Ministry of Health has been key to the success of this development and continues to identify human, financial and other resources to sustain the cancer unit. To date 69 patients have successfully undergone chemotherapy: 43 breast cancer, 22 Kaposi sarcoma, 2 colorectal cancer, 1 bladder cancer, 1 multiple myeloma. 21 health care workers were trained on cancer management; 9 doctors, 7 nurses and 5 pharmacists. What was learned: There are many opportunities for South-to-South partnership to support the establishment or improvement of cancer care. This model implemented in Swaziland can be replicated in other African countries. Documenting the model for replication in other countries is recommended.

Little Hands Beating Cancer: Building Resource Capacity for Cancer Control in Sub-Saharan Africa

Background and context: Uganda Child Cancer Foundation (UCCF) is a nongovernmental organization that was formed in 2006, as an in-house fundraising charity for Uganda Cancer Institute (UCI). UCCF mobilizes treatment and social support for vulnerable children battling cancer and advocates for cancer control in Uganda. It is mainly managed by childhood cancer survivors/volunteers and individuals directly affected by cancer. Children Caring about Cancer (3C) program is a strategic approach through which UCCF supports children in schools to start cancer clubs which are called 3C clubs. Aim: The main aim is to create a platform through which school going children are empowered with knowledge and experiences to enable them appreciate the cancer burden and create opportunities for them to develop and implement interventions addressing the burden of cancer at their level. Strategy/Tactics: UCCF works closely with UCI in cancer control, UCI is a Uganda Ministry of Health national technical arm of government. UCCF was formed to raise awareness about cancer in the communities and public especially with the young people and also to support children with cancer, UCCF reaches high school students and teachers with cancer education and awareness through the ministry of education and school administration structures. UCCF runs a social media campaign dabbed #3ChildrenCaringAboutCancer which uses activities done by the clubs as posts targeting children, policy makers and the community. In addition, UCCF launched a national children cancer conference in 2016 as a unique platform for stakeholder engagements and for highlighting work the children are doing in cancer control. Program/Policy process: The UCCF-3C recruits and works with children in schools by establishing cancer clubs. The clubs run activities geared toward cancer awareness, patient support and community outreach/advocacy. The clubs are headed by patrons and student-led club executives. The executive is responsible for leadership and recruitment of fellow young people through a child to child process. The patrons are trained to act as mentors to the executive to support various 3C programs in school. The patrons have an interschool committee that enables them to network and plan to support the children and club needs. UCCF works with the UCI to coordinate 3C club activities, patrons, and students leaders in sustaining the clubs in schools. Outcomes: In 85 3C school clubs formed, the program has reached; 85,000 children, 3000 teachers and over 170,000 guardians. Young people have been able to contribute to cancer control in Uganda through cancer awareness, advocacy and patient support. What was learned: Children Caring about Cancer (3C) program is strategic for building resource capacity for sustainable cancer control in Uganda.

Feasibility study of serial lumbar puncture and acetazolamide combination in the management of elevated cerebrospinal fluid pressure in AIDS patients with cryptococcal meningitis in Uganda

A feasibility study of serial lumbar puncture and acetazolamide combination in managing raised cerebrospinal fluid pressure was undertaken in 18 patients with AIDS and cryptococcal meningitis in Uganda. There were no adverse events related to the intervention and improvement in minimental status score, performance score, symptoms and a reduction in intracranial opening pressure were observed. This method is therefore feasible in AIDS-associated cryptococcal meningitis in a resource-poor setting given the observed safety and possible effectiveness, a larger study is warranted.

A comparative investigation of methods for longitudinal data with limits of detection through a case study

The statistical analysis of continuous longitudinal data may be complicated since quantitative levels of bioassay cannot always be determined. Values beyond the limits of detection (LOD) in the assays may not be observed and thus censored, rendering complexity to the analysis of such data. This article examines how both left-censoring and right censoring of HIV-1 plasma RNA measurements, collected for the study on AIDS-related Non-Hodgkin’s lymphoma (AR-NHL) in East Africa, affects the quantification of viral load and explores the natural history of viral load measurements over time in AR-NHL patients receiving anticancer chemotherapy. Data analyses using Monte Carlo EM algorithm (MCEM) are compared to analyses where the LOD or LOD/2 (left censoring) value is substituted for the censored observations, and also to other methods such as multiple imputation, and maximum likelihood estimation for censored data (generalized Tobit regression). Simulations are used to explore the sensitivity of the results to changes in the model parameters. In conclusion, the antiretroviral treatment was associated with a significant decrease in viral load after controlling the effects of other covariates. A simulation study with finite sample size shows MCEM is the least biased method and the estimates are least sensitive to the censoring mechanism.

Dose-modified oral chemotherapy for AIDS-related non-Hodgkin’s lymphoma (AR-NHL) in East Africa

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Background: Dose-modified chemotherapy for AR-NHL in the pre-HAART era has been shown to be equally efficacious and less myelotoxic [N Engl J Med 1997;336:1641 (mBACOD); J Clin Oncol 2001;19:2171 (mCHOP)]. In resource-constrained settings, intravenous chemotherapy and supportive care of the AIDS/cancer patient are challenging (J Natl Cancer Inst 2002;94:718). Methods: We embarked on a pilot feasibility trial of dose-modified oral chemotherapy [lomustine 50 mg/m2 D1 (C1 only); VP-16 100 mg/m2 D1–3; and cyclophosphamide/procarbazine 50 mg/m2 each D22–26 at 6-week intervals (1 cycle) for 2 cycles] in HIV-infected patients with biopsy-proven AR-NHL in East Africa. Results: A total of 52 pts (23 Uganda; 29 Kenya) were registered to study. The majority of pts were female (56%) with median age 39 yrs (range 18–64); poor PS (2 or 3) - 62%; high grade lymphoma (65%); advanced stage (III or IV) - 67%; and B symptoms (79%). At study entry median CD4 count was 207/μL and HIV-1 viral load 98,857 copies/ml. Nineteen pts (37%) had access to ARV. A total of 74.5 cycles of therapy were administered to 49 pts (median 2; range 0.5–2). The regimen was well tolerated. There were 4 episodes of febrile neutropenia and 3 treatment-related deaths (6% mortality rate). Overall objective response rate is 67% (CR/uCR 49%); median survival 8.2 months (range <1.0 to 52.5+ mos.); and 22 patients remain alive as of 10/7/05. Conclusions: Dose-modified oral chemotherapy is efficacious, has comparable outcome to that in the US in pre-HAART era, an acceptable safety profile, and is pragmatic in the resource-limited setting. Further investigation of the oral regimen vs. mCHOP is warranted. [Supported in part by NIH grants: CA83528, AI36219, CA70081, and TW00011. Bristol-Myers Squibb and Sigma Tau Pharmaceuticals provided the chemotherapy drugs for this trial.] (J. Black, PhD, formerly DCTD, NCI, Bethesda, MD, USA).

No significant financial relationships to disclose.

Strategies to overcome myelotoxic therapy for the treatment of Burkitt's and AIDS-related non-Hodgkin's lymphoma

BACKGROUND

Strategies to circumvent or lessen the myelotoxicity associated with combination chemotherapy may improve the overall outcome of the management of patients particularly in resource poor settings.

OBJECTIVES

To develop effective non-myelotoxic therapies for Burkitt's Lymphoma (BL) and AIDS-related non-Hodgkin's lymphoma.

DATA SOURCES

Publications, original and review articles, conference abstracts searched mainly on Pubmed indexed for medline.

DATA EXTRACTION

A systematic review of the clinical problem of combination chemotherapy. Identification of clinical strategies that circumvent or lessen the myelotoxicity of combination cytotoxic chemotherapy. Length of survival, lack of clinically significant (> grade 3) myelosuppression and weight loss were used as markers of myelotoxicity.

DATA SYNTHESIS

Review of published experience with some of these strategies including dose-modification of multi-agent chemotherapy; rationale for targeted therapies, and the preclinical development of a mouse model exploring the role of metronomic scheduling substantiate pragmatism and feasibility of these approaches.

CONCLUSION

Myelotoxic death rates using multi-agent induction chemotherapy approach 25% for endemic Burkitt's lymphoma and range between 20% to 60% for AIDS-related malignancy. This is mostly explained by the paucity of supportive care compounded by wasting and inanition attributable to advanced cancer and HIV infection making patients more susceptible to myelosuppressive side effects of cytotoxic chemotherapy. Investigations and alternative approaches that lessen or circumvent myelotoxicity of traditional cytotoxic chemotherapy for the management of Burkitt's lymphoma and AIDS-related non-Hodgkin's lymphoma in the resource-constrained setting are warranted. Pertinent pre-clinical and clinical data are emerging to support the need for abrograting the myelosuppressive effects of traditional cytotoxic chemotherapy. This can be achieved by developing targeted anti-viral and other strategies, such as the use of bryostatin 1 and vincristine, and by developing a preclinical mouse model to frame the clinical rationale for a pilot trial of metronomic therapy for the treatment of Burkitt's and AIDS-related lymphoma. Implementation of these investigational approaches must be encouraged as viable anti-cancer therapeutic strategies particularly in the resource-constrained settings.

Oral combination chemotherapy in the treatment of AIDS-associated Hodgkin's disease

OBJECTIVES

To determine the effectiveness of an oral combination chemotherapy regimen administered to patients with AIDS-associated Hodgkin's disease.

DESIGN

Prospective, pilot phase II clinical trial.

SETTING

Consecutive patient recruitment occurred at two medical centers in the United States: Albany Medical Center, Albany, New York, where patients were recruited prior to December 31, 1996 (pre-HAART era); and University Hospitals of Cleveland, Cleveland, Ohio, where patients were recruited after January 1, 1997 (HAART era).

INTERVENTION

Oral chemotherapy consisted of lomustine (100 mg/m2 day I for cycle one and odd cycles thereafter); etoposide (200 mg/m2 days 1 through 3); and cyclophosphamide and procarbazine (each 100 mg/m2 days 22 through 31). Cycles were repeated every six weeks. Colony-stimulating factor support (G-CSF in all instances) was allowed.

MAIN OUTCOME MEASURES

Clinical demographic variables, peripheral blood counts, serum chemistries, CD4 lymphocyte count, histopathological subtype of Hodgkin's disease were identified for all patients, who were staged according to Ann Arbor criteria.

DATA ANALYSIS

Common Toxicity Criteria were utilized to assess safety; response was assessed using ECOG criteria; and survival was analyzed by Kaplan-Meier methods and difference of survival between pre-HAART and HARART era was compared using log-rank test.

RESULTS

Eleven patients (six in pre-HAART era), all but one male, with a median age of 36 years, excellent performance status and advanced International Prognostic Score were treated. Myelosuppression was the major side effect and there were minimal other grade 3 or greater toxicity all of which were promptly reversible. An overall objective response rate of 82% (with 18% complete responses) and median survival duration of 24 months (range 2.5 +/- 68) were observed. Survival was markedly improved in patients treated in the HAART era (median not reached versus 7.25 months, p = 0.034).

CONCLUSIONS

This feasibility study demonstrates acceptable tolerance and excellent clinical activity of oral combination chemotherapy in patients with AIDS-associated Hodgkin's disease. Improved survival is observed in combination with HAART therapy. Dose-modification of this regimen would be suitable to evaluate in the resource constrained setting and larger confirmatory studies are encouraged.

Clinical characteristics of Burkitt's lymphoma from three regions in Kenya

OBJECTIVES

To describe the clinical characteristics of Burkitt's lymphoma (BL) from three regions in Kenya at different altitudes with a view towards understanding the contribution of local environmental factors.

DESIGN

Prospective cross-sectional study.

SETTING

Kenyatta National Hospital and seven provincial hospitals in Kenya.

METHOD

Histologically proven cases of Burkitt's lymphoma in patients less than 16 years of age were clinically examined and investigated.

MAIN OUTCOME MEASURES

For every case the following parameters were documented: chief complaint(s); physical examination, specifically pallor, jaundice, oedema, lymphadenopathy, presence of masses, splenomegaly and hepatomegaly. Reports of evaluation of chest radiograph, abdominal ultrasound/scan, bone marrow aspiration, cerebral spinal fluid cytology, liver and kidney function tests, urinalysis, stool occult blood and full blood count results. Stage of disease was assigned A, B, C or D. Cases of BL from three provinces of Kenya with diverse geographical features were analysed: Central, Coast, and Western.

RESULTS

This study documented 471 BL cases distributed as follows: Central 61 (males 39 and 22 females), M:F ratio 1.8:1; Coast 169 (111 males and 58 females), M:F ratio 1.9:1; and Western 241 (140 males and 101 females), M:F ratio 1.4:1. The major presenting complaints were: abdominal swelling--Central 36%, Coast 4% and Western 26%; swelling on the face--Central 31%, Coast 81% and Western 64%; and proptosis--Central 3%, Coast 1% and Western 9%. The mean duration of these complaints in weeks were Central 6.9, Coast 6.08, and Western 5.05. The initial physical finding was a tumour mass in 39%, 72% and 54% of cases for Central, Coast and Western respectively. Tumour stage at diagnosis was: stage A--Central 21%, Coast 43% and Western 34%; stage B--Central 10%, Coast 5% and Western 10%; stage C--Central 41%, Coast 34% and Western 30%; and stage D--Central 28%, Coast 17% and Western 26%. For the age and sex matched cases the results show that commonly involved sites were: abdomen--Central 35%, Coast 9% and Western 14%; jaw (mandible)--Central 24%, Coast 22% and Western 31%; maxilla--Central 6%, Coast 24% and Western 11%; and lymph nodes--Central 10%, Coast 4% and Western 8%. The disease stage was A--Central 33%, Coast 44% and Western 36%; stage B--Central 11%, Coast 10% and Western 27%; stage C--Central 39%, Coast 34% and Western 27%; and stage D--Central 21%, Coast 13% and Western 37%.

CONCLUSION

This study shows that clinical features of childhood BL vary with geographical region. The variations are documented in proportion of jaw, maxilla, abdominal and lymph nodal sites involvement. The differences observed are potentially due to the local environmental factors within these provinces. BL cases from Western province had features, intermediate between endemic and sporadic. Coastal province BL cases were similar to endemic BL, while BL cases from Central province resembled more or less sporadic BL subtypes. Strategies to explain and investigate the local environmental factors associated with the observed differences may certainly contribute towards improved understanding and clinical management of BL.

Anatomical site predilections of non-Hodgkin's lymphoma in human immunodeficiency virus infection: a report on 54 cases

OBJECTIVE

To identify and describe the primary anatomic sites of non-Hodgkin's lymphoma arising in the setting of Human Immunodeficiency Virus infection.

DESIGN

Prospective (ongoing) study.

SETTING

Kenyatta National Hospital a referral and teaching hospital in Kenya.

SUBJECTS AND METHODS

Patients (n=54) with human immunodeficiency virus with associated non-Hodgkin's lymphoma managed at the Kenyatta National hospital from January 2001 to December 2003. Relevant clinical information obtained by medical history, physical examination and investigations.

RESULTS

Of the 54 patients studied 29(54%) were males and 25(46%) females with median age 36 and range 20 to 61 years. Fifty (93%) had high grade and four (7%) intermediate grade lymphoma, the former had 15 (30%) Burkitt's and the rest large cell lymphoma. The stages at diagnosis were IV 35(65%), III 14(26%) and II 5(9%) and all had B symptoms. The primary sites at presentation to the hospital were peripheral nodes 16(30%), abdominal 15(28%), pectoral/chest wall 11(20%), central nervous system eight (15%) and systemic/generalised, four (7%).

CONCLUSION

This study demonstrates that there were preferred anatomical sites of involvement by HIV associated non-Hodgkin's lymphomas and the finding of pectoral/ chest involvement in this series may not be coincidental. Further, this study suggests that anatomical sites predilection may be due to the tendency of viral associated malignancies to home to specific anatomic sites and also due to the anatomy of the lymphoreticular system. Studying virus pathogenesis in malignancies should consider also the anatomic sites involved.

Endogenous excitatory drive to the respiratory system in rapid eye movement sleep in cats

A putative endogenous excitatory drive to the respiratory system in rapid eye movement (REM) sleep may explain many characteristics of breathing in that state, e.g. its irregularity and variable ventilatory responses to chemical stimuli. This drive is hypothetical, and determinations of its existence and character are complicated by control of the respiratory system by the oscillator and its feedback mechanisms. In the present study, endogenous drive was studied during apnoea caused by mechanical hyperventilation. We reasoned that if there was a REM-dependent drive to the respiratory system, then respiratory activity should emerge out of the background apnoea as a manifestation of the drive. Diaphragmatic muscle or medullary respiratory neuronal activity was studied in five intact, unanaesthetized adult cats who were either mechanically hyperventilated or breathed spontaneously in more than 100 REM sleep periods. Diaphragmatic activity emerged out of a background apnoea caused by mechanical hyperventilation an average of 34 s after the onset of REM sleep. Emergent activity occurred in 60 % of 10 s epochs in REM sleep and the amount of activity per unit time averaged approximately 40 % of eupnoeic activity. The activity occurred in episodes and was poorly related to pontogeniculo-occipital waves. At low CO2 levels, this activity was non-rhythmic. At higher CO2 levels (less than 0.5 % below eupnoeic end-tidal percentage CO2 levels in non-REM (NREM) sleep), activity became rhythmic. Medullary respiratory neurons were recorded in one of the five animals. Nineteen of twenty-seven medullary respiratory neurons were excited in REM sleep during apnoea. Excited neurons included inspiratory, expiratory and phase-spanning neurons. Excitation began about 43 s after the onset of REM sleep. Activity increased from an average of 6 impulses s-1 in NREM sleep to 15.5 impulses s-1 in REM sleep. Neuronal activity was non-rhythmic at low CO2 levels and became rhythmic when levels were less than 0.5 % below eupnoeic end-tidal levels in NREM sleep. The level of CO2 at which rhythmic neuronal activity developed corresponded to eupnoeic end-tidal CO2 levels in REM sleep. These results demonstrate an endogenous excitatory drive to the respiratory system in REM sleep and account for rapid and irregular breathing and the lower set-point to CO2 in that state.

Survival by AIDS defining condition in rural Uganda

OBJECTIVES

To report the initial AIDS defining conditions, CD4 lymphocyte counts around the time of AIDS diagnosis, and survival by AIDS defining condition in a population based cohort in rural Uganda.

METHODS

Participants in an HIV natural history cohort in rural Uganda were reviewed every 3 months at routine visits and at other times when they were ill. The date and nature of the first AIDS defining condition in participants developing AIDS during follow up between the start of the cohort in 1990 and the end of 1998 were noted. The CD4 count at, or within, 3 months of this time was recorded for those participants who developed AIDS (WHO stage 4) after 1993.

RESULTS

The median survival from developing AIDS to death was 9.3 months and the median CD4 lymphocyte count around the time of developing AIDS was 150 cells x 10(6)/l. The most frequent AIDS defining conditions were wasting syndrome, oesophageal candidiasis, and mucocutaneous herpes simplex virus infection (HSV) for more than 1 month. The median survival with wasting syndrome, Kaposi's sarcoma, and oesophageal candidiasis was less than 3.5 months; however, survival with cryptosporidial diarrhoea, chronic HSV, and extrapulmonary tuberculosis was greater than 20 months. There was little relation between CD4 count around the time of development of the AIDS defining condition and the median survival with that condition.

CONCLUSIONS

The survival for most AIDS defining conditions was generally shorter and the median CD4 lymphocyte count higher than studies reported from developed countries. However, the conditions with the longest survival (cryptosporidial diarrhoea, chronic HSV, and extrapulmonary tuberculosis) had a similar survival to that in developed countries and these conditions have a high background level in this population.

Augmenting expiratory neuronal activity in sleep and wakefulness and in relation to duration of expiration

Augmenting expiratory cells (n = 23) were recorded in the rostral medulla of five cats in sleep and wakefulness. The objective was to determine the relationship of their activity to the duration of expiration (TE) and, particularly, to TE in rapid-eye-movement (REM) sleep, when expirations are short and may even cause fractionated breathing. Correlation analysis (Kendall's tau) showed no consistent relationship in any state between the breath-by-breath mean activity of augmenting expiratory cells and TE. This result contradicts predications of an inverse relationship between augmenting expiratory activity and TE. Some cells (11 of 23) were more active in REM than in non-REM sleep and were active during fractionated breathing. This suggests that fractionated breathing in REM sleep is caused by short expiratory phases and not by intermittent inhibition of an ongoing inspiration.

Disseminated aspergillus fumigatus infection: case report

A case of disseminated aspergillus fumigatus infection is reported in a 43 year old Ugandan female with no known immune system disorder(not neutropenic and HIV-1 sero negative). She presented with multiple cutaneous ulcers, recurrent empyema thoracis, a past history of intra-abdominal abscess and bowel infarction. Empirical treatment for tuberculosis was previously given without improvement. A diagnosis of aspergillus fumigatus based on a combination of tissue wet potassium hydroxide preparation, fungal culture and tissue histologic typing was made. Despite antifungal therapy with intravenous amphotericin B infusion in 5% dextrose, after a normal baseline renal function test, the patient died in the second week of admission. Autopsy showed disseminated aspergillosis involving the pleural space, pericardium, spleen, and meningitis in addition to the cutaneous sites. Disseminated aspergillus fumigatus infection in a non-immunocompromised is rare antemortem diagnosis. This case highlights the difficulty in making a diagnosis in the face of many endemic conditions with similar presentation.

Activity of medullary respiratory neurons during ventilator-induced apnea in sleep and wakefulness

Mechanical ventilation of cats in sleep and wakefulness causes apnea, often within two to three cycles of the ventilator. We recorded 137 medullary respiratory neurons in four adult cats during eupnea and during apnea caused by mechanical ventilation. We hypothesized that the residual activity of respiratory neurons during apnea might reveal its cause(s). The results showed that residual activity depended on 1) the amount of nonrespiratory inputs to the cell (cells with more nonrespiratory inputs had greater amounts of residual activity); 2) the cell type (expiratory cells had more residual activity than inspiratory cells); and 3) the state of consciousness (more residual activity in wakefulness and rapid-eye-movement sleep than in non-rapid-eye-movement sleep). None of the cells showed an activation during ventilation that could explain the apnea. Residual activity of approximately one-half of the cells was modulated in phase with the ventilator. The strength of this modulation was quantified by using an effect-size statistic and was found to be weak. The patterns of modulation did not support the idea that mechanoreceptors excite some respiratory cells that, in turn, inhibit others. Indeed, most cells, inspiratory and expiratory, discharged during the deflation-inflation transition of ventilation. Residual activity failed to reveal the cause of apnea but showed that during apnea respiratory neurons act as if they were disinhibited and disfacilitated.

Renal glycosuria treated as diabetes mellitus: case report

A case of renal glycosuria is reported. A 55 year old female was diagnosed and treated in an upcountry hospital for diabetes mellitus. She developed symptoms of hypoglycaemia while on an oral hypoglycaemic agent, leading to her admission in Mulago Hospital. Persistent glycosuria was noted despite treatment and normal serum glucose. Oral glucose tolerance test and timed urine glucose showed a normal curve but high urine sugar. A diagnosis of renal glycosuria was made, oral hypoglycaemic therapy was stopped, patient improved and was discharged. Though renal glycosuria is a benign condition, mistaken diagnosis for diabetes mellitus puts patients at risk of hypoglycaemia due to treatment. Diagnosis of the condition requires physicians' awareness of its existence in our community and the use of Marbles' criteria obviates confusion with diabetes mellitus though it does not absolutely exclude Fanconi syndrome.

Excitatory drive to the respiratory system in REM sleep

REM sleep is sometimes divided into tonic and phasic stages. Tonic REM sleep processes are both excitatory and inhibitory to the respiratory system. Inhibitory effects arise from the atonic processes of the REM state and include atonia of thoracoabdominal and extrathoracic airway muscles. Excitatory effects include increases in respiratory rate, central respiratory drive and rate of rise of diaphragmatic activity. The combination of these varying antagonistic effects determines the level of ventilation.

Diaphragmatic activity during REM sleep in the adult cat

Diaphragmatic electromyograms from five adult cats were studied to determine whether diaphragmatic activity, like central respiratory activity, increases in rapid-eye-movement (REM) sleep. Breaths with inspiratory durations between 250 and 2,000 ms were analyzed. 1) There was a greater slope of the moving time average of diaphragmatic activity in REM than in non-REM (NREM) sleep. These greater slopes occurred whether the route of breathing was through the upper airways or through an endotracheal tube and may have resulted from early recruitment of motor units. 2) Mean diaphragmatic activity was also greater, but other variables (peak activity, the area under the curve of diaphragmatic activity, mean intratracheal pressures, inspiratory airflow rates, and tidal volumes) were not greater in REM than in NREM sleep. 3) Diaphragmatic activity was similar in REM sleep and active wakefulness. 4) Across states, slope of the moving time average varied with the duration of inspiration: greater slopes were associated with shorter breaths. These results are consistent with an increase in central respiratory drive in REM sleep that increases the rate of rise of diaphragmatic activity.

Respiratory responses to tracheobronchial stimulation during sleep and wakefulness in the adult cat

The response to tracheal stimulation (50 microliters of tap water) during wakefulness, non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep was investigated in adult cats. In wakefulness, repetitive coughing occurred on 80% of the trials. In NREM and REM sleep, the most frequent response (approximately 69% and 58% of the trials, respectively) was arousal, followed by coughing. Apneas occurred following the stimulus and before arousal in 11% and 24% of the trials in NREM and REM sleep, respectively. In NREM sleep, the tracheal stimulus sometimes evoked expiratory efforts following a normal inspiratory effort (11% of the trials). These were much weaker than the expiratory efforts during coughing in wakefulness. In REM sleep, stimulation in 11% of the trials elicited increased inspiratory efforts. Although these may have been diminutive preparatory inspirations for coughing, they were much smaller than preparatory inspirations associated with coughing in wakefulness, and they were never followed by active expiratory efforts. Arousal from either NREM or REM sleep in response to tracheal stimulation was sometimes associated with an augmented breath. This response, which is common upon spontaneous arousal, may lead to deeper aspiration of the tracheal fluid. We conclude that in cats coughing requires wakefulness and that airway stimuli in sleep cause a variety of respiratory responses, some of which may be maladaptive.

Swallowing in sleep and wakefulness in adult cats

Clinical evidence indicates that swallowing, a vital function, may be impaired in sleep. To address this issue, we elicited swallows in awake and sleeping adult cats by injecting water through a nasopharyngeal tube. Our results indicate that swallowing occurs not only in non-rapid eye movement (NREM) sleep, but also in rapid eye movement (REM) sleep. In NREM sleep, the injections often caused arousal followed by swallowing, but, in the majority of cases, swallowing occurred in NREM sleep before arousal. These swallows in NREM sleep were entirely comparable to swallows in wakefulness. In contrast, the injections in REM sleep were less likely to cause arousal, and the swallows occurred as hypotonic events. Furthermore, apneas were sometimes elicited by the injections in REM sleep, and there was repetitive swallowing upon arousal. These results suggest that the hypotonic swallows of REM sleep were ineffective.

Central respiratory activity in rapid eye movement sleep: augmenting and late inspiratory cells [corrected]

The activities of 15 augmenting and 11 late inspiratory cells were studied in wakefulness, nonrapid eye movement (NREM) and rapid eye movement (REM) sleep in adult cats. All but one of each cell type were significantly more active in REM than in NREM sleep or relaxed wakefulness, indicating that central respiratory drive is increased in REM sleep. A negative correlation between the discharge rates of augmenting and late inspiratory cells and the durations of inspirations was characteristic of REM sleep. Although augmenting and late inspiratory activity increased in REM sleep, respiratory efforts in REM sleep were as likely to be lower than those in NREM sleep as they were to be greater. Thus, unknown factors can counteract the increased central drive. There was a positive correlation between the discharge rate of a cell on breath n and on breath n + 1, indicating that processes with a long time constant control respiratory drive in REM sleep. It is proposed that REM-specific reticular cells drive the respiratory oscillator and its output cells to produce the patterns of breathing in REM sleep.

Behavioral Control in Breathing

Cats trained to stop inspiration do so by inactivating inspiratory cells of the automatic brain stem control system. The cells causing this inactivation are not those that stop inspiration during normal breathing;rather, they may be peculiar cells with both respiratory and nonrespiratory properties.

Medullary respiratory neuronal activity during augmented breaths in intact unanesthetized cats

In intact unanesthetized cats, we studied the behavior of five medullary respiratory cell types during augmented breaths: 1) decrementing, 2) augmenting, and 3) late-onset inspiratory cells and 4) decrementing and 5) augmenting expiratory cells. Certain features of their behavior were inconsistent with either their proposed role in rhythmogenesis or the proposed nature of augmented breaths. For example, decrementing inspiratory cells switched to an augmenting pattern during the second part of the augmented breath. This behavior is inconsistent with mechanisms proposed to account for their decrementing pattern and with their postulated inhibitory actions on augmenting inspiratory cells, which are intensely active at the same time. In addition, augmenting expiratory cells discharged intensely at the end of inspiration and then throughout expiration, indicating that their discharge profiles (and, therefore, their inhibitory actions) are more labile than previously assumed. The behavior of inspiratory cells gave mixed evidence of the idea that the augmented breath comprises two inspiratory phases: decrementing and late-onset inspiratory cells discharged in two bursts during the inspiratory phase, but other inspiratory cells discharged without interruption throughout it. These results reveal that current theories do not account for the behavior of medullary respiratory cells during augmented breaths.

Postinspiratory neuronal activities during behavioral control, sleep, and wakefulness

Cells that discharge in early expiration and inhibit other respiratory cells purportedly cause a separate phase of the respiratory cycle that has been named "postinspiration." Our objective was to study these postinspiratory cells in the intact unanesthetized cat during sleep, wakefulness, and behavioral inhibition of inspiration, but we were unable to find cells with strong and consistent activity confined to early expiration. Instead, we found that various cell types were active in early expiration. They included inspiratory-expiratory phase-spanning cells, retrofacial augmenting expiratory cells with bursts in early expiration, retrofacial decrementing expiratory cells, tonic expiratory cells, and cells with variable activity in the early part of expiration. Just as the cell types active during early expiration were heterogeneous so too were their activities during behavioral inhibition of inspiration and during sleep. These results suggest that the state of early expiration is determined by many different cell types rather than a single class of postinspiratory cells.

Behavioral inspiratory inhibition: inactivated and activated respiratory cells

1. Eleven adult cats were trained to stop inspiration in response to a conditioning stimulus. The conditioning stimuli were presented at the onset of inspiration at intervals of approximately 20-30 s. Intratracheal pressures, diaphragmatic activity, and the extracellular activity of single medullary respiratory neurons were recorded while the animals performed this response. 2. Inactivation of the diaphragm to the conditioning stimuli occurred at latencies that varied from 40 to 110 ms and averaged 74 +/- 32 (SD) ms. 3. The subjects of this report are 38 inspiratory neurons that were inactivated and 19 cells that were activated when inspiration was stopped behaviorally. These cells were located in the region of n. ambiguus and the ventrolateral n. of tractus solitarius. 4. The inspiratory cells that were inactivated behaviorally had the following characteristics: 1) Most had an augmenting inspiratory profile with (n = 14) or without (n = 9) postinspiratory activity. Other types were inspiratory throughout (n = 5), decrementing inspiratory (n = 3), tonic inspiratory (n = 4), early inspiratory (n = 2), and expiratory-inspiratory (n = 1). 2) Their mean discharge rate was 39 +/- 2.7 (SE) Hz. 3) The latency of their inactivation in response to the task averaged 81 +/- 4.9 (SE) ms, and 4) Their activity corresponded closely to breathing not only during the behavioral response but also during eupnea (eta 2 = 0.62 +/- 0.04, mean +/- SE) and respiratory acts such as sneezing, sniffing, meowing, and purring. 5. The cells that were activated when inspiration was stopped behaviorally had the following characteristics. 1) As a group, they had discharge profiles related to every phase of the respiratory cycle. 2) They were recorded in the same region as, and often simultaneously with, respiratory cells that were inactivated. 3) Their activity patterns were highly variable such that the signal strength and consistency of the respiratory component of that activity were weak (eta 2 = 0.27 +/- 0.03, mean +/- SE). 4) The latency of their activation in response to the task averaged 58 +/- 2.7 (SE) ms and was significantly shorter than the latency of inactivation of the high eta 2-valued inspiratory cells. 5) This activation was intense and prolonged. 6. It is hypothesized that the activated cells integrate nonrespiratory and respiratory inputs and act to inhibit other respiratory cells during the behavioral inhibition of inspiration.

The activity of late inspiratory cells during the behavioral inhibition of inspiration

Cats can be trained to stop inspiration behaviorally--a response mediated by inactivation of brainstem inspiratory neurons. Neurons that discharge late in the inspiratory phase of the respiratory cycle may terminate that phase; therefore, such cells may be activated behaviorally to inhibit inspiration. To test this hypothesis, we studied the activity of late-onset inspiratory neurons located in the dorsal and ventral medullary respiratory groups in cats trained to stop inspiration behaviorally. Twenty-eight of 112 respiratory neurons were classified as late-onset inspiratory neurons. They had an average eta 2 value of 0.58 (+/- 0.13, S.D.) and an average maximal discharge rate of 42 Hz (+/- 18, S.D.). For most cells, the period of activity varied under different conditions: some extended their activity into early inspiration; others, into early expiration. Eighteen of these late-onset inspiratory neurons were completely silent when the animals stopped inspiration behaviorally, and 10 discharged only a few action potentials. The latter response was weak and inconsistent, and we conclude that late inspiratory cells do not inhibit other brainstem inspiratory cells when animals stop inspiration behaviorally.

Inspiratory neurons that are activated when inspiration is inhibited behaviorally

Respiration can be automatic or controlled behaviorally. Behavioral control in the cat occurs, at least in part, through control of the brainstem respiratory neurons that constitute the automatic system. Thus, when inspiration is inhibited behaviorally, inspiratory neurons in the medulla are inactivated. Reported herein are data on inspiratory cells, located in both the dorsal and ventral respiratory groups, that were activated when other inspiratory cells there were inhibited behaviorally. During spontaneous breathing, their activity showed much variability unattributable to the respiratory cycle--indicating that they receive a considerable non-respiratory input. These cells might act as the interface through which behavioral inhibition of inspiration occurs.

The activity of retrofacial expiratory cells during behavioral respiratory responses and active expiration

The activity of retrofacial expiratory cells was recorded from cats trained to inhibit inspiration in response to a tone. Because retrofacial expiratory cells inhibit inspiratory cells, we thought they might mediate this response. We found, however, that these cells were inactive during the response and thus could not be the mediators thereof. Moreover, retrofacial expiratory cells were inactive also during sneezing and thus were not acting as expiratory upper motoneurons during these active expirations. We propose that they act to promote and synchronize inspiratory activity.

Behavioral control of breathing in the cat

Respiration depends upon brainstem neuronal circuits that produce the respiratory rhythm and relay it, via the ventrolateral columns, to motor neurons in the spinal cord. This brainstem system produces respiration automatically, i.e. without conscious effort, and is responsive to chemical and mechanical stimuli that signal imbalances in respiratory homeostasis. In addition to this automatic/metabolic respiratory system, there is a voluntary/behavioral system that controls the respiratory muscles during speaking, breath holding, and other voluntary respiratory acts. It has been proposed that this behavioral system involves corticofugal fibers that bypass the automatic system, course in the dorsolateral columns, and end at the level of the respiratory motor neurons. According to this scheme, the integration of behavioral control with automatic/metabolic control occurs at the level of the motor neurons and not within the automatic system. This proposed scheme has not been investigated experimentally. In the present study, we trained cats to control their respiration and recorded the activity of cells within the automatic system in the medulla during this behavioral control. We trained the animals to terminate inspiration and prolong expiration when a tone sounded. Microelectrode recordings from 40 medullary respiratory neurons showed that most cells, inspiratory and expiratory, became inactive during the behavioral apneic response. The exceptions were some expiratory cells that were activated during the task. These results suggest that the integration of behavioral influences occurs within the automatic system.

Activity of respiratory neurons during NREM sleep

The purpose of this study was to analyze differences in the activity of medullary respiratory neurons in the unanesthetized, intact cat during wakefulness and non-rapid-eye-movement (NREM) sleep. We studied single respiratory neurons located within a 1-2 mm deep, 8-10 mm long zone that followed, and included in its dorsal aspect, the retrofacial and ambiguus nuclei. The analysis of variance was used to detect respiratory activity, and cycle-triggered histograms were plotted. The respiratory signal strength and consistency of the respiratory activity were quantified with the eta 2 statistic. We determined for each breath in wakefulness and NREM sleep the average discharge rate during the active phase of the cell, the number of action potentials during the active phase of the cell, and durations of both the cycle and inspiration. Differences in discharge rates and in the number of discharges between wakefulness and NREM sleep were tested with the t test. A bimodal distribution of eta 2 values for the population of neurons indicated there were two groups of respiratory cells: those with eta 2 values less than 0.3 and those with values greater than 0.3. The former we call weak respiratory cells; the latter, strong respiratory cells. Strong and weak cells were classified further as inspiratory or noninspiratory on the basis of the shape of their cycle-triggered histograms. Within the class of strong inspiratory cells, those with the highest eta 2 values 1) reached their peak discharge rate early, 2) discharged at high rates throughout inspiration, and 3) were inactive during expiration. The values of these variables diminished progressively in inspiratory cell groups with lower eta 2 values. Most cells were less active in NREM sleep than in wakefulness. Similar proportions of weak and strong cells and inspiratory and noninspiratory cells were affected by sleep. The reduction in sleep of the activity of strong inspiratory cells was consistent with a general relationship between this activity and the duration of inspiration. Lower discharge rates were associated with longer breaths; higher rates with shorter breaths. This relationship existed within both NREM sleep and wakefulness, and the plot of the relationship across these states formed a continuous function. The reduction in discharge rate in sleep was greater for weak than for strong inspiratory cells: the correlation coefficient between percent change in rate and eta 2 values was -0.636 for inspiratory cells, but it was not significant (-0.265) for noninspiratory cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Consistency and signal strength of respiratory neuronal activity

The concerns of this study are taxonomic. We demonstrate a defining characteristic of respiratory neuronal activity. This characteristic is the degree or size of the respiratory component in the activity of a respiratory cell. The essential feature of respiratory activity is that it occurs in phase with some portion of the respiratory cycle. Therefore, neuronal activity can be arranged within a matrix in which the columns are fractions of the respiratory cycle and the rows are breaths and, as Netick and Orem (10) have shown, this matrix can be analyzed with an analysis of variance to determine whether the activity contains a respiratory component. However, the analysis of variance indicates nothing about the size of a statistically significant respiratory component. We hypothesized that the size of the respiratory component in the activity of different respiratory cells differed among cells but was a stable characteristic of any given cell. The index used to quantify the degree of respiratory activity was eta 2, the proportion of the total variance of the activity of a respiratory neuron consisting of the variance occurring across fractions of the respiratory cycle. This index theoretically depends on a) the range of activity levels across a respiratory cycle and the dispersion of activity levels over this range (parameters signifying the strength of the respiratory signal) and b) the variability in the activity of the cell across breaths (a parameter signifying the consistency of the respiratory activity). Theoretically, eta 2 values can vary from 0.0 to 1.0 indicating, respectively, that none or all of the variability in the activity of a cell across breaths is accounted for by a respiratory effect. eta 2 was used to analyze the size of the respiratory component in the activity of 32 medullary respiratory neurons recorded during nonrapid eye movement (NREM) sleep in chronic cats. These different respiratory cells had activity patterns with eta 2 values ranging from 0.1 to 0.9. However, the activity of a given cell produced eta 2 values that were consistent from sample to sample. Therefore, the eta 2 value of the activity of a cell was a defining, stable characteristic of that cell. The eta 2 values of the activity of the cells were strongly correlated with the consistency of their discharge pattern from breath to breath (r x,y = 0.975).(ABSTRACT TRUNCATED AT 400 WORDS)

Intercostal muscle activity during sleep in the cat: an augmentation of expiratory activity

Intercostal-muscle activity (I-EMG) was studied in sleep and wakefulness in ten adult cats. The animals were implanted with electrodes for recording the electroencephalogram (EEG), electrooculogram (EOG), and pontogeniculooccipital (PGO) waves as well as intercostal- and neck-muscle activity. A small-animal pneumotachograph connected to a tracheal cannula was used to monitor respiration. The data were obtained in 87 recording sessions, each lasting 5-6 h. Total EEG power (fast Fourier analysis) and integrated I-EMG activity were computed over consecutive 5.12-sec periods of wakefulness and nonrapid eye movement (NREM) sleep. Cycle-triggered histograms based on 50 breaths were computed also in wakefulness and NREM sleep. I-EMG was classified as expiratory or inspiratory according to when the activity was maximal during the respiratory cycle. Expiratory I-EMG augmented progressively during NREM sleep with the maximal activity occurring just before rapid eye movement (REM) sleep. The mean correlation between total EEG power and expiratory I-EMG for all expiratory muscles was 0.441 (+/- 0.16 SD; n=24). In contrast to the consistent augmentation of expiratory I-EMG, inspiratory I-EMG changes from wakefulness to deep NREM sleep varied within and between muscle groups: in 21% of the cases, activity decreased from wakefulness to NREM sleep; in 16% of the cases, activity increased; in 56% of the cases, activity did not change; and in 7% of the cases, activity increased in only the expiratory phase. We conclude the consistent augmentation of expiratory intercostal muscle indicates an active, NREM sleep-specific respiratory process that may have important implications for lung mechanics in that state.

Characteristics of midbrain respiratory neurons in sleep and wakefulness in the cat

Midbrain neurons were recorded in sleep and wakefulness in chronic cats. In the first phase of this study, we attempted to detect respiratory neurons by observing neuronal activity on an oscilloscope and listening to it after audioamplification. We studied 780 neurons in this non-quantitative way and failed to detect any respiratory activity. In the second phase, 203 neurons were analyzed statistically: 15% of these had activity patterns significantly related to the respiratory cycle. In the third and final phase, we studied the details of the activity of midbrain respiratory neurons. Sixteen of 281 single neurons had discharge patterns significantly related to the respiratory cycle, but only 3 of the 16 were related to breathing with a consistency that essentially excluded the possibility of a false positive error. All 3 of these cells were only intermittently respiratory, and the intermittency varied from cell to cell and tended to depend upon the state of consciousness. These results differ substantially from reports that more than 30% of midbrain and diencephalic cells are respiratory neurons. The differences may be explained by the previous authors' use of a statistic, the respiratory nodulation index, that, as shown here and in a previous stimulation study, produces a large number of false positive errors.

Erroneous classification of neuronal activity by the respiratory modulation index

Failure to record respiratory activity in the mesencephalon of the chronic cat led us to analyze the formula (the respiratory modulation index, RMI) used by Hugelin and his colleagues to discriminate respiratory neurons. Using computer simulations, we compared RMI with the analysis of variance (F) and the non-parametric Friedman's test (chi 2). Samples were drawn repeatedly from simulated distributions of neuronal activity and were allocated to successive bins representing the respiratory cycle. Allocations of bins were made randomly so that only a chance relationship existed between the simulated activity and respiratory cycle. These simulations revealed that the RMI erroneously yields values indicative of a respiratory relationship and does so as a function of sample size and the variability and shape of the distribution of non-respiratory activity. Although some of the simulated conditions violated assumptions of the F test and, to a lesser degree, the chi 2, these statistics erred at rates close to the chosen 5% level. When respiratory activity was stimulated, chi 2 and F were more sensitive than RMI in detecting the relationship. We conclude that the high incidence of respiratory activity reported by the Hugelin group is based upon a faulty statistic and is highly questionable.

Laryngeal and diaphragmatic responses to airway occlusion in sleep and wakefulness

Under anesthesia, electrodes were implanted in 5 adult cats for chronically recording sleep parameters. In the same operation, a tracheal fistula was created that allowed tracheal intubations for recordings of breathing (pneumotachography) and tracheal occlusions in subsequent experiments conducted during the spontaneous sleep-waking cycle. After a recovery period of at least 3 months, electrodes were placed, under ether anesthesia, in the laryngeal abductors. Two days later, electrodes were inserted into the diaphragm, and the responses of the diaphragm and laryngeal abductor muscles to airway occlusion in sleep and wakefulness were studied. Total airway occlusion at end-expiration in NREM sleep caused a progressive augmentation of both laryngeal adductor and diaphragmatic activity. Increases in laryngeal abductor activity exceeded for increases in diaphragmatic activity. The greatest augmentations between one breath and the next were seen when occluded breath "n" occurred in sleep and occluded breath "n + 1" occurred in wakefulness. This augmentation of activity at the transition from sleep to wakefulness was greater for the laryngeal abductors than for the diaphragm, and it signifies an immediate wakefulness stimulus to the response to an occlusion. Occlusions in REM sleep caused a variable augmentation in laryngeal inspiratory activity, but, across animals, there was no clear augmentation of either tonic (expiratory) laryngeal abductor or diaphragmatic activity. In addition, arousal in response to occulusion was delayed in REM sleep.

Medullary respiratory neuron activity: relationship to tonic and phasic REM sleep

This study analyzes the relationship of brain stem respiratory neuron activity to the tonic and phasic events of rapid-eye-movement (REM) sleep. Dorsal and ventral medullary respiratory neurons were recorded in sleeping cats. Discharges of inspiratory and expiratory cells increased in number and frequency with increases in pontogeniculooccipital (PGO) spiking (phasic REM activity). Across neurons the correlations between PGO wave frequency and respiratory neuron activity were positively related to the discharge levels of the neurons: the more active the cell, the greater the relationship to PGO activity. Tonic REM influences on respiratory neurons were calculated by extrapolating from the regression line relating PGO frequency and neuron activity to the hypothetical state of no PGO activity. These calculated levels, when compared to non-REM sleep levels, showed that tonic REM mechanisms reduced the activity of some neurons and activated others. Ventral medullary respiratory activity generally was decreased during tonic rem, whereas dorsal respiratory group cells were variously activated and inactivated. These results demonstrate an association of brain stem respiratory activity to nonrespiratory REM sleep variables.

Respiratory neurons of the pneumotaxic center during sleep and wakefulness

Extracellular recordings were made from respiratory related units (RRUs) in the pneumotaxic center (PNC) of unanesthetized cats across states of consciousness: wakefulness, NREM and REM sleep. Contrary to expectations from results in acute preparations, well-modulated respiratory activity was detected in chronic animals with vagi intact. Pontine RRU activity decreased during sleep in 75% of the cells studied. The greatest reduction occurred during REM sleep.

Experimental control of the diaphragm and laryngeal abductor muscles by brain stem arousal systems

The effect of mesencephalic central tegmental field (FTC) stimulation in barbiturate anesthetized cats on the activity of the diaphragm and the laryngeal abductors was studied. With brief stimulus trains, two effects were observed: (1) a short latency, stimulus-specific activation of these muscles and (2) phase-switching of the respiratory cycle. The characteristics of short latency driving were as follows: (1) the latency and threshold for activation of the laryngeal abductors was less than for activation of the diaphragm; (2) driving continued for the duration of the stimulus only; and (3) during expiration, the threshold for short latency driving was lowest in the early part of the phase and progressively increased throughout it. Phase-switching had these characteristics: (1) expiration-to-inspiration (E-to-I) phase-switching was obtained in all cases and, in 17% of the cases, stimulation of the same FTC site also produced I-to-E phase-switching; (2) phase-switching was a function of stimulus intensity and the time of stimulation; and (3) during expiration, phase-switching showed a threshold profile opposite to that for short latency driving. These effects could be obtained after bilateral dorsolateral pontine lesions, bilateral vagotomy, and transection at the C8 level. It was concluded that the FTC could influence breathing by two systems. One is relatively direct to respiratory motoneurons and the other engages the oscillator.