Risk of Aerosol Formation During High-Flow Nasal Cannula Treatment in Critically Ill Subjects

BACKGROUND

There is a persistent concern over the risk of respiratory pathogen transmission, including SARS-CoV-2, via the formation of aerosols (ie, a suspension of microdroplets and residual microparticles after evaporation) generated during high-flow nasal cannula (HFNC) oxygen therapy in critically ill patients. This concern is fueled by limited available studies on this subject. In this study, we tested our hypothesis that HFNC treatment is not associated with increased aerosol formation as compared to conventional oxygen therapy.

METHODS

We used laser light scattering and a handheld particle counter to detect and quantify aerosols in healthy subjects and in adults with acute respiratory disease, including COVID-19, during HFNC or conventional oxygen therapy.

RESULTS

The use of HFNC was not associated with increased formation of aerosols as compared to conventional oxygen therapy in both healthy subjects (n = 3) and subjects with acute respiratory disease, including COVID-19 (n = 17).

CONCLUSIONS

In line with scarce previous clinical and experimental findings, our results indicate that HFNC itself does not result in overall increased aerosol formation as compared to conventional oxygen therapy. This suggests there is no increased risk of respiratory pathogen transmission to health care workers during HFNC.

Gender differences in clinical manifestations before AIDS diagnosis among injecting drug users

We compared incidence rates of self-reported HIV-related symptoms and illnesses, verified clinical manifestations and findings on physical examination between female and male injecting drug users (IDU) stratified by HIV serostatus in the Amsterdam cohort study on the natural history of HIV infection. HIV-positive female IDU (n = 100) reported a higher frequency of several symptoms and illnesses than male IDU (n = 139). Symptoms were reported more chronically by women compared to men, while clinical manifestations were reported by a greater proportion of women affected by these illnesses compared to men. In HIV-negative IDU (163 women and 232 men) the incidence rates were lower compared to HIV-positives, and a similar gender effect on reported symptoms and illnesses was found. Adjusting for biological, behavioral, demographic and study related variables did not change the gender effect on clinical manifestations substantially. We conclude that the gender effect among HIV-positive IDU was not caused by a differential impact of HIV infection on the incidence of the studied clinical manifestations among female and male IDU, but reflects a higher morbidity of female IDU compared to male IDU.

Early and late HIV-1 RNA level and its association with other markers and disease progression in long-term AIDS-free homosexual men

OBJECTIVE

To study the association between virological markers and clinical progression in individuals with long-term AIDS-free HIV infection.

DESIGN

Seventy-seven HIV-infected participants in the Amsterdam cohort study who remained AIDS-free for at least 8 years were prospectively followed during that time and during a subsequent period in which 15 developed AIDS.

METHODS

Serum HIV-1 RNA levels were evaluated at 1 and 8 years after study entry. Progression to AIDS following the 8 AIDS-free years was studied using Kaplan-Meier estimates and Cox proportional hazard analysis.

RESULTS

HIV-1 RNA increased over time in a large proportion of these long-term AIDS-free men. Most subjects showed progressive immune system damage and/or clinical manifestations of HIV disease at year 8. High RNA levels at year 8 were significantly associated with symptomatic HIV Infection, low CD4+ T-cell count, p24 antigenaemia, low T-cell reactivity at year 8 as well as rapid annual CD4+ T-cell decline. High RNA level at year 1 was associated with high RNA levels at year 8 and low CD4+ T-cell count at year 1. In univariate analysis, RNA was associated with progression to AIDS after 8 years. In multivariate analysis, only the CD4+ T-cell count at year 8 remained significantly associated with progression to AIDS.

CONCLUSIONS

In later stages of HIV infection, measures of immune deficiency may be more powerful prognostic markers than serum HIV-1 RNA level, indicating that optimal staging of the HIV-infected patient requires the combined use of RNA levels, CD4+ T-cell counts, and T-cell reactivity instead of RNA levels alone.

Summary of track C: epidemiology and public health

AIM

To review Track C on epidemiology and public health.

DESCRIPTIVE EPIDEMIOLOGY

Recent trends in the descriptive epidemiology are reported, for example, the rapid spread of HIV in certain Asian countries and the more precise insights in the spread thanks to subtyping of HIV-1 (and HIV-2).

TRANSMISSION

There is now ample evidence that sexually transmitted diseases enhance the rate of transmission. Viral load in the plasma of the mother is highly predictive for perinatal transmission.

PROGRESSION

Natural history studies have shown that true non-progressors are probably rare. Preliminary evidence indicates that the progression rate to AIDS and death does not differ by HIV-1 subtype. Some genetic factors are associated with the rate of disease progression and a few with susceptibility to HIV infection.

INTERVENTIONS AND PREVENTION

Needle-exchange programmes as an intervention measure for injecting drug users were hotly debated and so were HIV (home) testing and counselling. Successes in prevention were reported from Thailand and Uganda, and also from small scale programmes.

Differences in progression to AIDS between injection drug users and homosexual men with documented dates of seroconversion

We compared rates of progression to AIDS for 99 injection drug users and 120 homosexual men with documented dates of HIV-1 seroconversion. The crude risk of developing AIDS was higher among homosexual men than injection drug users [relative hazard (RH) = 2.4; 95% confidence interval (CI) = 1.3-4.4]. The relative hazard was slightly smaller among participants with a seroconversion interval of < or = 1 year (RH = 2.2; 95% CI = 1.0-5.2). The effect was partially explained by the inclusion of Kaposi's sarcoma in the AIDS case definition. Excluding those with Kaposi's sarcoma, the relative hazard was 2.0 (95% CI = 1.1-3.8). Using the 1993 AIDS case definition decreased the effect (RH = 1.9; 95% CI = 1.1-3.4). Finally, the high pre-AIDS mortality among injection drug users could partially explain the difference in progression rate between injection drug users and homosexual men. Combining the effect of the above-mentioned factors resulted in a relative hazard of 1.3 (95% CI = 0.7-2.6). Thus, the slower progression to AIDS among injection drug users compared with homosexual men was largely explained by differences in the spectrum of AIDS-defining illnesses, pre-AIDS mortality, and length of seroconversion interval.

Human immunodeficiency virus infection and other risk factors for skin abscesses and endocarditis among injection drug users

OBJECTIVE

To study incidence rates of and risk factors for skin abscesses at the site of injection and episodes of endocarditis among injection drug users (IDU).

DESIGN

A comprehensive, open cohort study of drug users on the natural history of human immunodeficiency virus (HIV) infection.

METHODS

From 1986 to 1994, injection drug users in Amsterdam were included in the study. Incidence rates of self-reported skin abscesses and verified episodes of endocarditis were calculated. In uni- and multivariate Poisson regression analysis, risk factors for skin abscesses and endocarditis were determined.

RESULTS

521 HIV-seronegative and 237 HIV-seropositive IDU were followed for 1640 person-years. A total of 545 skin abscesses were reported by 269 IDU (incidence 33/100 person-years). HIV infection, female gender, prostitution among females, foreign nationality, injection of heroin and cocaine, a high frequency of injecting, and obtaining syringes through the needle exchange program were independently and positively associated with skin abscesses. During follow-up, 17 verified episodes of endocarditis were observed (incidence 1.3/100 person-years). Endocarditis was independently associated with HIV infection and a previous history of endocarditis. Furthermore, women and IDU with a skin abscess appeared to be at an increased risk for endocarditis.

CONCLUSIONS

HIV infection is an independent risk factor for skin abscesses and endocarditis. Also, women are at an increased risk for these injection-related infections. Prevention activities, like promotion of skin cleaning, should be directed at those IDU in whom one or more risk factors have been identified.

Incidence and risk factors for pneumonia in HIV infected and non-infected drug users

OBJECTIVE

To study the incidence and risk factors for pneumonia in a cohort of HIV infected and non-infected drug users (DU).

DESIGN

A prospective epidemiological study.

SETTING AND PATIENTS

Injecting and non-injecting DU who attended the Municipal Health Service in Amsterdam for follow-up visits in the study.

MAIN RESULTS

203 HIV infected and 437 non-infected DU were followed for a total of 1749 person-years. HIV infected DU reported 111 episodes of pneumonia, which required hospitalization in 29 cases, and HIV negative DU reported 55 episodes, which required hospitalization in nine cases. The incidences among HIV positive and HIV negative DU were 0.19 and 0.05 per person-year respectively. With multivariate Poisson regression current injecting (RR 2.13), recent seroconversion (RR 3.92), asthmatic constitution (RR 2.72), CD4+ cell count between 200-500 (RR 1.67 compared to > 500), CD4+ cell count less than 200 (RR 2.23 compared to > 500) and a previous history of pneumonia (RR 2.43) were independently associated with self-reported pneumonia among HIV infected DU. Among HIV negative DU heroin smoking (RR 1.87), asthmatic constitution (RR 3.62) and a previous history of pneumonia (RR 2.84) were independently associated with self-reported pneumonia. Also a higher Quetelet Index (QI) appeared to be protective (QI > or = 21 RR 0.42, QI 19-21 RR 0.82 compared to QI < 19) among HIV negative DU. Risk factors for reported and hospitalized cases of pneumonia were comparable among HIV positive DU.

CONCLUSIONS

HIV infected DU are at increased risk for pneumonia and the rate increases with lower CD4 cell counts. Also behavioural characteristics, such as injecting drug use and smoking heroin, and clinical history variables, such as a history of pneumonia or an asthmatic constitution, are risk factors for pneumonia among DU. Pneumococcal vaccination should not only be focused on HIV positive DU but also on the identified risk groups among HIV negative DU.

Lower prevalence and incidence of HIV-1 syncytium-inducing phenotype among injecting drug users compared with homosexual men

OBJECTIVE

To study the prevalence, incidence and predictive value for progression to AIDS of the HIV-1 syncytium-inducing (SI) phenotype in HIV-infected injecting drug users (IDU) compared with HIV-infected homosexual men.

DESIGN

Two prospective cohort studies on HIV-1 infection among IDU and homosexual men.

METHODS

HIV-infected IDU (n = 225) and homosexual men (n = 366) without AIDS were studied from March 1989 through December 1993. Data on laboratory markers, including the presence of SI variants, demographics, behavioural characteristics and clinical events were collected at every visit.

RESULTS

At baseline, SI variants were detected in 4% of IDU and 17% of homosexual men. During the study period 18 IDU and 68 homosexual men switched from non-SI to SI phenotype (4-year cumulative incidence, 14.6 and 28.4%, respectively) before AIDS diagnosis. Among participants with a documented date of HIV infection the cumulative incidence of SI was lower among IDU than homosexual men (4-year cumulative incidence, 6.2 and 20.7%, respectively). At AIDS diagnosis, 21% of all AIDS cases among IDU had the SI phenotype compared with 54% among homosexual men. In both risk groups an accelerated CD4 decline was found after the non-SI-to-SI switch. The SI phenotype appeared to be a predictor of AIDS (multivariate relative hazard, 5.33), independent of CD4 cell count and p24 antigen at baseline. In the multivariate time-dependent analysis, the relative hazard of SI phenotype decreased considerably, which is consistent with the hypothesis that the effect of SI phenotype on progression to AIDS is mediated by CD4 cell count.

CONCLUSION

The SI phenotype is associated with accelerated CD4 decline and progression to AIDS in both risk groups. The remarkable lower prevalence and incidence of the SI phenotype among IDU may implicate a difference in pathogenesis and natural history of HIV infection linked to transmission group.