Gastroenteric tube feeding plays a major role in the management of patients with poor voluntary intake, chronic neurological or mechanical dysphagia or gut dysfunction, and patients who are critically ill [1]. But tube feeding is a risk indicator of aspiration pneumonia [2] and diarrhea is a common and problematic complication of enteral nutrition [3].

In order to reduce the incidence of aspiration pneumonia and/or diarrhea in tube feeding, modification of the volume and administration method of tube feeding [4], measurement of gastric residual volumes at monitoring intervals of 4 hours [5], placement of feeding tubes postpylorically [6] and use of feeding pump with a continuous infusion for 20 hours adjusting infusion rate based on gastric residual volume [7] have been considered.

Semi-solid enteral formula has been demonstrated to reduce the incidence of aspiration pneumonia but is difficult to administer via the nasogastric tube [8]. We investigated the effects of changing liquid enteral formula to semi-solid enteral formula in patients with aspiration pneumonia and/or diarrhea in whom liquid enteral formula had been infused via the nasogastric tube or PEG tube.

Patients with liquid enteral formula who showed aspiration pneumonia and/or diarrhea in our hospital were asked to participate in our study. Thirty-one patients agreed to participate but one patient withdrew from our study because symptoms of reflux esophagitis were aggravated not by semi-solid enteral formula but by 16Fr nasogastric tube. All patients were on total enteral nutrition.

The mean age of the 30 patients was 79.5 years (youngest 49, oldest 97 years), female:male ratio was 21:9 and the mean body weight was 47.4 kg. Twenty-five patients showed aspiration pneumonia and 10 patients showed diarrhea (five patients showed both aspiration pneumonia and diarrhea). The enteral formula was infused via the nasogastric tube in 26 patients and via the PEG tube in four patients. The underlining diseases were cerebral infarction, cerebral hemorrhage, subarachnoid hemorrhage, Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, lung cancer, liver cancer, malignant lymphoma, etc.

This study was approved by the ethics committee of our hospital and we got the informed consent from the patients and/or their family. We changed the liquid enteral formula to semi-solid enteral formula (PG Soft® EJ) and infused via the nasogastric tube (16Fr) or PEG tube (20Fr). We infused 300 - 400 kcal of PG Soft® EJ for 30 minutes using a pressurized bag (Figure 1) three times a day. One hundred mL of water was injected 30 minutes before the infusion of PG Soft® EJ and 50 mL of water was injected after the infusion of PG Soft® EJ via the nasogastric tube or PEG tube. The liquid enteral formula was Isocal® Bag 2K in 25 cases, Peptamen® in 3 cases, Isocal® Support Bag in 1 case and Renalen® D in 1 case.

Diarrhea was defined as having loose or watery stools at least three times per day, or more frequently than normal for an individual [9]. The effects of PG Soft® EJ were classified into improvement, worsening, and no effects.

Table 1 shows the effects of changing liquid enteral formula to PG Soft® EJ. Eighteen out of the 25 cases of aspiration pneumonia and 8 out of the 10 cases of diarrhea showed improvement. None of the 30 cases showed worsening. A case

of aspiration pneumonia developed constipation which was controlled with magnesium oxide. Besides that, no adverse effects were noted.

Liquid formula syndrome is various complications of liquid enteral formula which are due to low viscosity [10]. Some clinical complications that can occur with enteral nutrition, such as diarrhea and gastroesophageal reflux, are observed after administration of a liquid enteral formula and thickened enteral formula has been reported to be able to prevent these complications [11]. Thickened enteral formula is also referred to as semi-solid enteral formula [12]. Aspiration pneumonia is presumably due to severe gastroesophageal reflux and semi-solid enteral formula has been demonstrated to reduce the incidence of aspiration pneumonia [8].

The positive effects of thickened enteral formula are considered to be based on its high viscosity, which reduces the outflow rate of gastric contents and thereby helps to prevent diarrhea and gastroesophageal reflux [12]. Thickened enteral formula is a formula in which viscosity is intentionally increased to prevent enteral nutrition-related complications, such as aspiration pneumonia and diarrhea [12] and has been used mainly in Japan [11]. It has been more than a decade since semi-solid enteral formula was developed but there is limited published literature on this topic despite the wide usage of semi-solid enteral formula in Japan [13]. Semi-solid enteral formula is considered to be more physiologic because swallowed food does not enter the stomach in the liquid form [13].

Semi-solid enteral nutrients have high viscosity and, therefore, are typically administered through a large-diameter tube [11] [14]. We used 12Fr nasogastric tube and 20Fr PEG tube for liquid enteral formula and 16Fr nasogastric tube and 20Fr PEG tube for PG Soft® EJ. One patient withdrew from the study because symptoms of reflux esophagitis were aggravated not by semi-solid enteral formula but by 16Fr nasogastric tube. We could infuse PG Soft® EJ for 30 minutes with the use of a pressurized bag.

Table 2 shows the difference between Isocal® Bag 2K (400 kcal) and PG Soft® EJ (400 kcal). The viscosity is the biggest difference between the two [13]. Several studies examining thickened enteral formula with viscosity ranging from 900 to 20,000 mPa·s have shown the efficacy of thickened enteral formula in preventing gastroesophageal reflux in this range [12]. Several clinical case studies have been published on prevention of diarrhea using thickened enteral formula with viscosity ranging from 3000 to 20,000 mPa·s [12]. The viscosity of Isocal® Bag 2K is 20,000 mPa·s and this viscosity is considered to be effective for prevention of both aspiration pneumonia and diarrhea. We used PG Soft® EJ because of its high viscosity but the other semi-solid enteral formulas with viscosity ranging from 3000 to 20,000 mPa·s [12] are considered to be also effective.

In the case of liquid enteral formula we administered 150 mL of water simultaneously with the liquid enteral formula and 50 mL of water was injected after the infusion of liquid enteral formula to flush the nasogastric tube or PEG tube. But in the case of semi-solid enteral formula, simultaneous administration of water decreases its viscosity. So, we injected 100 mL of water 30 minutes before and 50 mL of water after the infusion of PG Soft® EJ via the nasogastric tube or PEG tube.

We got an approval to use the photograph from the patient and her family.

The authors declare no conflicts of interest regarding the publication of this paper.

Oishi, M., Yasuda, M., Chikamatsu, M., Akiyama, R., Yamamoto, M., Terakawa, K., Suzuki, Y., Ando, M., Shimada, M., Kumagai, T. and Nakayama, A. (2020) Effects of Semi-Solid Enteral Formula on Aspiration Pneumonia and Diarrhea. International Journal of Clinical Medicine, 11, 193-198. https://doi.org/10.4236/ijcm.2020.114019