Respective effects of end-expiratory and end-inspiratory pressures on alveolar recruitment in acute lung injury

OBJECTIVE: A low tidal volume can induce alveolar derecruitment in patients with acute lung injury. This study was undertaken to evaluate whether this resulted mainly from the decrease in tidal volume or from the reduction in end-inspiratory plateau pressure and whether there is any benefit in raising the level of positive end-expiratory pressure (PEEP) while plateau pressure is kept constant. DESIGN: Prospective crossover study. SETTING: Medical intensive care unit of a university teaching hospital. PATIENTS: Fifteen adult patients ventilated for acute lung injury (PaO2/FiO2, 158 +/- 34 mm Hg; lung injury score, 2.7 +/- 0.6). INTERVENTIONS: Three combinations were tested: PEEP at the lower inflection point with 6 mL/kg tidal volume, PEEP at the lower inflection point with 10 mL/kg tidal volume, and high PEEP with tidal volume at 6 mL/kg, keeping the plateau pressure similar to the preceding condition. MEASUREMENTS AND MAIN RESULTS: Pressure-volume curves at zero PEEP and at set PEEP were recorded, and recruitment was calculated as the volume difference between both curves for pressures ranging from 15 to 30 cm H2O. Arterial blood gases were measured for all patients. For a similar PEEP at the lower inflection point (10 +/- 3 cm H2O), tidal volume reduction (10 to 6 mL/kg) led to a significant derecruitment. A low tidal volume (6 mL/kg) with high PEEP (14 +/- 3 cm H2O), however, induced a significantly greater recruitment and a higher Pao than the two other strategies. CONCLUSION: At a given plateau pressure (i.e., similar end-inspiratory distension), lowering tidal volume and increasing PEEP increase recruitment and PaO2.     

Regional V˙A/Q˙ ratios in man using 133Xe and single photon emission computed tomography (SPECT) corrected for attenuation

We describe a technique to obtain non-invasively regional pulmonary ventilation–perfusion ratios (V˙_A/Q˙) using single photon emission computed tomography (SPECT) and continuous infusion of ¹³³Xe. Single photon transmission tomography was used for attenuation correction, for delineation of the lungs and for V˙_A/Q˙ calculations. Data are presented for six normal subjects and compared to those for two patients with moderate chronic obstructive pulmonary disease (COPD). The mean V˙_A/Q˙ for the whole lung of the normal subjects ranged from 0·49 to 0·65, group mean 0·56 ± 0·07 (1 SD), and there was no significant difference between the right and left lung. The consistently too low V˙_A/Q˙ values are related to the inability to measure regional blood volume and the low resolution of the scintillation camera, giving an under-estimation of tracer input. For the normal subjects, the dispersion of V˙_A/Q˙, as defined by the standard deviation of the individual distribution functions, ranged from 0·12 to 0·19. One of the patients was characterized by a low mean V˙_A/Q˙ of 0·35, and the other patient had a wide dispersion (SD) of V˙_A/Q˙ of 0·37. In the normal subjects, a consistent V˙_A/Q˙ gradient was found only in the ventrodorsal direction. ¹³³Xe and SPECT can be used to obtain meaningful biological information regarding ventilation/perfusion relationships of potential clinical value.     

A prospective, randomized trial of integrative medicine for women with ovarian cancer

Objectives

Despite increased use of integrative medicine in cancer therapy, little data exist on its efficacy. This prospective, randomized, pilot trial sought to evaluate the feasibility of combined modality integrative medicine (CM-IM) in women with ovarian cancer (OvCA) and evaluate its effects on quality of life (QoL), chemotherapy toxicity and immunologic profiles.

Methods

Women with newly diagnosed OvCA requiring chemotherapy were offered enrollment. Those randomized to the experimental arm received hypnosis, therapeutic massage and healing touch with each cycle of chemotherapy. The control arm received chemotherapy without CM-IM. All patients completed QoL questionnaires prior to cycles 1, 3 and 6, and 6-months after chemotherapy. Immunologic profiles were measured. Statistical analysis was based on intent-to-treat. Student's t-test and Fischer's exact-test were used to determine differences.

Results

Forty-three women enrolled. All women randomized to CM-IM were successfully treated. There were no statistical differences between the groups in age, stage, grade, histologic cell type, CA125 levels, or surgical cytoreductive status. There was no difference in overall QoL measurements. Re-hospitalization rates, treatment delays, anti-emetic use, and infection rates were similar. Immunologic profiles revealed no difference between arms for WBC or salivary IgA levels. Women receiving CM-IM had consistently higher levels of CD4, CD8 and NK cells, although this did not reach statistical significance.

Conclusions

Prospective clinical evaluation of integrative medicine for women with gynecologic malignancy is feasible. This first, pilot study of CM-IM in gynecologic oncology demonstrated no improvement in QoL or chemotherapy toxicity. Integrative medicine-associated improvements in immunologic profiles warrant further investigation.     

A nonlinear model of the arterial vessels within a limb segment

The relationship between the arterial blood pressure and the volume of the arteries within a segment of an extremity is nonlinear. The present paper shows how the flow and volume pulsations of the arteries within a limb segment can be simulated taking this property into account. An electrical model was constructed comprising one resistor and two voltage dependent ‘capacitors’, the latter corresponding to the pressure dependent elasticity, or compliance, of the arteries. Adequate simulations were obtained over a wide pressure range, which is impossible with linear models. The nonlinear, i.e. pressure dependent, relationship between the volume and pressure of arteries, observed under static conditions, must also be taken into consideration when studying pulsatile events with models whether mathematical or physical.     

Long-term exposure to urban air pollution and myocardial infarction

BACKGROUND: Cohort studies have reported increased risks of cardiopulmonary mortality from long-term air pollution exposure, but the evidence is limited and inconclusive. We studied the association between long-term exposure to source-specific air pollution and myocardial infarction (MI) in a case-control study of first-time MI cases and population controls age 45 to 70 years in Stockholm county in 1992 to 1994. METHODS: Home addresses during several decades were combined with historical emission databases and dispersion models to obtain annual mean levels of pollutants from traffic and heating during 30 years for 1397 cases and 1870 controls. Nitrogen dioxide (NO2), carbon monoxide (CO), and particulate matter with an aerodynamic diameter less than 10 microm (PM10) were used as indicators of traffic emissions and sulfur dioxide (SO2) as an indicator of emissions from residential heating. RESULTS: There was no association between long-term average air pollution exposure and overall MI, but an increased risk of fatal MI was suggested, especially for out-of-hospital death. After adjustment for cardiovascular risk factors, the odds ratio for fatal MI associated with a 5th to 95th percentile difference in 30-year average exposure was 1.51 (95% confidence interval = 0.96-2.16) for NO2, 1.22 (0.98-1.52) for CO, 1.39 (0.94-2.07) for PM10, and 1.24 (0.77-2.02) for SO2. For out-of-hospital death, the odds ratio related to NO2 exposure was 2.17 (1.05-4.51). CONCLUSIONS: This study provides some support for an association between long-term air pollution exposure and fatal cardiovascular disease.     

Nowcasting (Short-Term Forecasting) of COVID-19 Hospitalizations Using Syndromic Healthcare Data,Sweden, 2020

We report on local nowcasting (short-term forecasting) of coronavirus disease (COVID-19) hospitalizations based on syndromic (symptom) data recorded in regular healthcare routines in Östergötland County (population ≈465,000), Sweden, early in the pandemic, when broad laboratory testing was unavailable. Daily nowcasts were supplied to the local healthcare management based on analyses of the time lag between telenursing calls with the chief complaints (cough by adult or fever by adult) and COVID-19 hospitalization. The complaint cough by adult showed satisfactory performance (Pearson correlation coefficient r>0.80; mean absolute percentage error <20%) in nowcasting the incidence of daily COVID-19 hospitalizations 14 days in advance until the incidence decreased to <1.5/100,000 population, whereas the corresponding performance for fever by adult was unsatisfactory. Our results support local nowcasting of hospitalizations on the basis of symptom data recorded in routine healthcare during the initial stage of a pandemic.     

Fatigue fracture morphology in human lumbar motion segments

The fatigue behavior of 17 fresh lumbar spine motion segments was examined during cyclic, axial, compressive loading. The loading frequency and magnitude were chosen to simulate vigorous physiological loading conditions. The average failure occurred after 318 such loading cycles. Two main types of failure occurred and both involved the endplate and the adjacent subchondral spongy bone of the vertebral body. A tendency was observed toward a relation between the degree of disk degeneration and fracture type. Location of the fatigue fractures corresponded to the location of earlier detected microcalluses of the spongy trabeculae in the vertebral body. The findings further demonstrated that, under repetitive physiological loading, the weakest part of the lumbar motion segment was the endplate and the adjacent spongy bone.     

Enhanced insulin absorption in the rabbit airways and lung by sodium dioctyl sulfosuccinate.

The objective of this investigation was to study regional absorption of inhaled insulin together with an enhancer (sodium di-octyl-sulfosuccinate [DOSS]) in the rabbit airways and lung. Insulin was administered with or without DOSS by aerosol inhalation, intratracheal infusion, intranasally, sublingually, and without DOSS intravenously. Blood glucose and plasma levels of insulin were measured during 100 min from the start of administration. Inhalation of insulin (3 U) with 0.25% or 1% DOSS decreased average blood glucose levels significantly more than inhalation of insulin (3 U) without DOSS. Intratracheal administration of 1.5 U of insulin with 0.25% DOSS in 0.3 mL of vehicle decreased the average blood glucose level significantly compared with intratracheal administration of 1.5 U of insulin and no DOSS in 0.3 mL of vehicle and compared with 1.5 U of insulin with 0.25% DOSS in 0.15 mL of vehicle. Intravenous insulin (1.5 U) and inhaled (1.5 U) insulin in 0.25% DOSS decreased average blood glucose levels significantly compared with intratracheal (0.15 mL), intranasal, and sublingual administration of 1.5 U of insulin with 0.25% DOSS. The bioavailability of inhaled insulin (1.5 U) with 0.25% DOSS was estimated to be 16% in comparison with 7% for intratracheally (0.15 mL), 1% intranasally, and 0.8% sublingually administered insulin (1.5 U with 0.25% DOSS), respectively. Inhaled insulin together with the absorption enhancer DOSS decreased the blood glucose level more effectively than insulin given intratracheally, intranasally, or sublingually. The effect on blood glucose reflected the difference in plasma insulin concentration for the different routes of administration.     

Measurement of pulmonary density by means of X-ray computerized tomography. Relation to pulmonary mechanics in normal subjects

We examined the relationship between pulmonary density, measured with computerized tomography, and pulmonary mechanics (static pulmonary volume; pulmonary resistance) in 39 normal subjects (20 nonsmokers and 19 smokers). Pulmonary density decreased with increasing static elastic recoil pressure, and smokers consistently showed higher pulmonary density than nonsmokers. Pulmonary density, measured at full inspiration, correlated inversely with total lung capacity. Pulmonary density showed a ventrodorsal gradient, which was greater at low elastic recoil pressure than at high recoil pressure. The study shows that pulmonary density is related to the mechanical properties of the lung in normal subjects. Increased pulmonary density appears to be a sensitive indicator of pulmonary damage induced by smoking. Further studies of the relationship between pulmonary density and pulmonary mechanics in disease seem warranted.     

Diagnosis of pulmonary embolism based upon alveolar dead space analysis

Pulmonary embolism (PE) leads to an abnormal alveolar deadspace that is expired in synchrony with gas from normally perfused alveoli. This feature of PE separates it from pulmonary diseases affecting the airways, which are characterized by nonsynchronous emptying of compartments with an uneven ventilation/perfusion relationship. An analysis of the single breath test (SBT) for CO2, SBT-CO2, focusing on the late tidal expirate, was made in order to evaluate the feasibility to use the SBT-CO2 for the diagnosis of PE. The test was evaluated in 38 patients with suspected PE where pulmonary angiography showed that nine had PE and 29 did not. It was also tested in a reference population consisting of patients with normal lung function, obstructive lung disease and interstitial lung disease. Previously suggested gas exchange measurements for the diagnosis of PE, ie, the physiologic deadspace fraction, VDphys/VT, and the arterial-to-end-tidal CO2 gradient, P(a-E')CO2, were also evaluated in the groups. SBT-CO2 achieved a nearly complete separation between the patients with PE and those without. The other measurements, however, showed a substantial overlap between patients with PE and those with obstructive or interstitial lung disease. The SBT-CO2 is simple and potentially widely available and warrants further study as a routine technique for the diagnosis of PE.