Research design, period and location
The study adopted a cross-sectional analytical design with quantitative techniques in data collection, analysis and presentation . The design was suitable in establishing associations between total energy, protein, carbohydrate, fat, zinc and selenium intakes and their nutrient adequacy among adult patients receiving total naso-gastric tube feedings. The study was conducted from August to November 2015.
The study was conducted at a referral hospital in the Copperbelt province in Ndola district of Zambia. It is the second largest public tertiary level hospital in Zambia with 851 bed capacity located in Ndola District . The hospital offers curative services for adults through in-patient departments (medical wards, intensive care unit [ICU], surgical wards, emergency/ambulatory, and obstetrics /gynecology wards) and out-patient departments .
The study targeted adult inpatients 20 to 65 years of age receiving hospital prepared total naso-gastric blended tube feeding admitted to the hospital. The sampling frame was estimated at 150 patients for the three months (14 weeks) period that the study would be undertaken, based on the estimated average of 50 patients per month on total naso-gastric tube feeding as reported by the Health Information Office (HIO) of Ndola Central Hospital . All of the study participants were non-ambulant and drawn from two female medical wards, two male medical wards, as well as the ICU.
Consenting adult patients, 20 to 65 years of age receiving hospital prepared total naso-gastric blended tube feeding in the previous 24 h and admitted to medical wards, and the intensive care unit, were eligible to participate in the study. The study’s exclusion criteria were patients receiving naso-gastric tube feeds prepared from outside the hospital kitchen. This is because feeds prepared from outside the hospital would not be analysed for nutrient content and could have affected the results if included.
Sampling technique and sample size
The referral hospital was purposively sampled among the four main tertiary hospitals in the country because of its speciality in treating adult illnesses. Further, medical wards and the intensive care unit were purposively sampled because they admitted the most participants receiving naso-gastric tube feedings .
For selection of individual study participants, comprehensive sampling was adopted, where all adult patients who satisfied the inclusion criteria and consented to participate were included [25, 26]. A total of 123 patients were eligible to participate in the study and 117 patients provided consent. Four participants had missing data and were subsequently excluded from the analysis. A total of 113 patients had information fully collected and comprised the sample size of the study.
Socio-economic and medical characteristics of adult inpatients receiving total naso-gastric tube feeding
One time face-to-face interviews were conducted at the wards with participants to obtain information on socio-economic characteristics. These interviews were guided by a researcher-administered questionnaire. For those patients who could not speak, only close relative who lived with them in the same household answered on their behalf.
A researcher-administered questionnaire was also used to collect medical characteristics on participants. Provisional admission diagnosis and length of stay data were collected by the researcher from individual medical files to the researcher-administered questionnaire. Clinicians attending to patients determined individual Glasgow Coma Scale (GCS) scores for participants and recorded them in the researcher-administered questionnaire.
Naso-gastric tube feeds collection, tracking and analysis
Fourteen (14) pairs of NGTF samples were collected every Wednesday, for 14 weeks (3 months, 1 week). Uniquely coded 20 ml transparent sterile vacutainer trace elements tubes (Vacutainer Systems Europe B.P No. 37–38241 Meylan Cedex-France, Becton Dickson) were used to collect these samples from the hospital kitchen’s preparation vessel. The samples were stored temporarily on dry ice at 0 °C then transferred to a freezer for longer storage at less than −20 °C within 3 h of collection time and finally transported to the laboratory for analysis below 0 °C . A laboratory form was used to record and track the samples. The form had information on time of food sampling, time of storage and volume collected. On the same form, results of nutrient content were reported for each sample. The volume of NGTF provided to the participants in the previous 24 h were calculated from the patients’ feeding charts in the medical files. The volumes aggregated per individual patient were used to determine the individual’s energy, zinc and selenium intakes.
Fourteen paired samples of naso-gastric feeds were analysed at ARC-Irene Analytical Services laboratory in South Africa to determine nutrient content. Nutrient analyses were conducted using the official analytical methods of Association of Analytical Chemists (AOAC): Kjeldahl for protein, acid hydrolysis for fat, computation of difference for carbohydrate, and inductively coupled plasma-atomic emission spectrometry for zinc and selenium .
The researcher-administered questionnaire and data collection procedures were pre-tested at a similar referral hospital, prior to the main study. The researcher-administered questionnaire was used to collect information on socio-economic and medical characteristics. The questions used to determine the socio-economic characteristics were adopted from the validated Zambia Demographic and Health Survey questionnaires (ZDHS) . Medical characteristics were developed after an intensive discussion with the clinicians for the facility. To enhance validity, the NGTF samples were collected and tested using an accredited laboratory in South Africa (ARC-Irene Analytical Laboratory).
The procedures employed in pre-testing the instruments were identical to those used in the main study, with participants of similar characteristics. A total of 10 patients participated in the pre-test and they were not included in the main study. The test and re-test method was used to evaluate the reliability of the researcher- administered questionnaire. During the pretest, data were collected twice from the same participants within an interval of three days and analysed. A correlation coefficient of 0.88 (95 % C.I; 0.78–0.95) was achieved between the two sets of data. A correlation coefficient of above 0.7 is usually considered adequate . By obtaining two random samples, the reliability of the NGTFs was also enhanced.
Statistical Package for Social Sciences (SPSS) version 20.0 was used for data entry, cleaning, and analysis. Descriptive statistics such as frequencies, means and standard deviations were used to describe the study population in terms of socio-economic and medical characteristics as well as the mean nutrient (total energy, fat, carbohydrate, protein, zinc and selenium) content of the naso-gastric tube feeds.
The naso-gastric feeds samples were analyzed for their variation using two way t-test, while nutrient adequacy was determined by comparing nutrient intake to the two standards using paired t-test.
To determine the individual energy requirement of each participant, the Harris-Benedict equations (HBE) (for females; Basal Energy Expenditure (BEE) = 655.1+ [9.6weight] + [1.8height] - [4.7age] and males; BEE = 66.5 + [13.8weight] + [5height] - [6.8age]) with individual stress factor) were applied . Energy intakes of 90 to 110 % of the calculated requirements was considered adequate . For zinc and selenium, the ESPEN minimum daily requirements (Zinc [11–19 mg/day] and Selenium [20–70 μg/day]) of adults on enteral nutrition were compared to participants’ intake during the previous 24 h .