Load management on the operating table

Mattresses made of flexible polyurethane foam, offering a broad range of physical, mechanical, and functional features, are common in hospital preventive treatment. These features determine their durability and clinical performance – both in terms of prevention and therapy.

polyurethane foamThe history of polyurethane encompasses several generations. Hard foams production technology was the first to be used. They are characterized by the lowest thermal conductivity coefficient, good mechanical properties, and poor damping of stresses occurring due to the patient’s body weight. When we talk about the models made of foam, various technical terms allow us to determine foam properties and quality. The second half of the 1950s marked the introduction of flexible foam. In only five years, these foams proved to be useful as the filling of operating table mattresses. The major benefit of soft foam is good flexibility and resistance to abrasion and tearing [1].

Foam mattresses adjust properly to user’s shapes, ensuring perfect support for the body. Operating table mattresses from ALVO are produced using two types of polyurethane foam – high resilience HR foam and viscoelastic shape memory foam. The entire mattress is covered with thermoplastic polyurethane material on a knitted fabric substrate.

The HR polyurethane foam ensures proper body cushioning, while its perfect point flexibility guarantees optimum anatomical fitting. High resilience foam restores its original shape twice as fast as standard foams [2,3].

Memory foam also referred to as the viscoelastic or low resilience polyurethane foam, has a higher density than regular polyurethane foams. It does not press the contact points of the body but adjusts to its shape. Memory foam provides perfect cushioning for a patient’s body movements. It is made mainly of polyurethanes with compound additives to increase its viscosity and density. The bubble foam structure forms a matrix that allows free air movement. Memory foam is sensitive to temperature changes. As the body heats it, the foam softens to fit perfectly the patient’s body shape [4].

Foams used in the production of ALVO mattresses perform various functions. Viscoelastic foam spreads evenly a load of bone protrusions (elbows, head, heels). Body parts vulnerable to bedsores go deeper in the soft mattress surface that adjusts its shape to the patient’s body. The flexible polyurethane foam layer responds faster than memory foam. The polyurethane layer has been designed to support heavier body areas without causing the sinking sensation.

three layers of ALVO mattresses

The chart below contains a summary of test results comparing the pressure generated on different types of mattresses.

The test has been conducted with a patient 175 cm tall patient weighing 90.72 kg, The test consisted of 20-minutes’ loading of:

  • standard mattress with the thickness of 50.8 mm, made entirely of HR foam and covered with a thermoplastic polyurethane layer,
  • three-layered Soft-Care mattress made of memory foam with a thickness of 8 mm and HR polyurethane foam with a thickness of 69.9 mm, covered with a thermoplastic polyurethane layer,

SUMMARY OF TEST RESULTS

1) Surgical product pads thickness 80 mm

2) Standard foam pads thickness 50 mm

STRESS MAPPING DURATION: 20 minutes

The test has been performed with a 175 cm tall male patient weighing 90.72 kg.

1)  Surgical product pads thickness 80 mm
2) Standard foam pads thickness 50 mm
HEAD
maximum pressure [mmHg]
65,00
172,54
average pressure [mmHg]
30,50
52,12
SHOULDERS
maximum pressure [mmHg]
38,70
60,78
average pressure [mmHg]
30,10
34,94
SACRUM
maximum pressure [mmHg]
43,80
46,60
average pressure [mmHg]
35,90
40,95
HEELS
maximum pressure [mmHg]
51,30
92,33
average pressure [mmHg]
25,00
41,05
GENERAL RESULTS
maximum pressure [mmHg]
65,00
172,54
average pressure [mmHg]
22,00
27,80
pressure

The use of a standard double-layer mattress generates approximately 38% higher maximum pressure as compared to three-layer mattresses. The average pressure is proportional in all two cases, but the lowest value, reaching 22 mmHg, has been recorded for a 90 mm thick mattress, which is 21% less than in a standard double-layer mattress.

Mattresses are categorized in terms of dynamics and capability to maintain specific pressure values in time. Properly selected mattresses may reduce excessive pressure load on the tissues, which is a resultant of a patient’s body weight and the area on which it acts. Considering the fact that material properties of foams used as hospital mattress filling have not been included in harmonized standards specified by the Ministry of Health, manufacturers usually refer to the CertiPUR standard guidelines concerning the components in use, limits of quantities and the list of prohibited substances [2].

Źródła:
[1] Historia poliuretanów http://www.polyurethanes.org/pl_PL/co-to-wlasciwie-jest/historia-2 (dostęp z dn. 18.04.2020 r.)
[2] Poliuretany http://wiedza.revita.pl/poradnik_uzytkownika/materace/Wpisy/2013/6/27_Wpis_1.html (dostęp z dn. 18.04.2020 r.)
[3] Swinarew B., „Poliuretany – nowoczesne wszechstronne materiały” Przetwórstwo tworzyw sztucznych, 2014, s.252 -259
[4] Wszystko o piance Visco https://www.dogsfavorite-hundebett.de/visco (dostęp z dn. 18.04.2020 r.)