View/Open

More documents

Recommendations

Info

6.1 Introduction Chapter 6 Discussion and Conclusions The outputs from the models validated in chapter 5 are discussed in this chapter. The discussion is focused on the conditions where reverse flow occurs and the consequent influence on exhaled air re-inhalation, condensation and humidity level in inhaled air. For better understanding of the situation, the related phenomena such as fluctuation amplitude, influences from ambient conditions and mask capacity are also discussed. The discussion is separated into two sections namely, fluid dynamics and thermodynamics. For simplification, the models do not include the influence of pressure setting on breath load. All models use a normal breath load with a 6 seconds breath cycle [37]. 6.2 Fluid dynamics Reverse flow and re-inhalation of exhaled air are discussed in this section. 6.2.1 Reverse flow Three factors are considered in this section, the breath load, pressure setting and mask capacity. 6.2.1.1 Breath load and pressure setting In general, under normal breathing, there is no reverse flow. However, when the breath load is increased by 1.5, 2 and 2.5 times of normal breathing under different CPAP pressure settings, the reverse flow outputs from the model are shown in Figure 6.1. It is indicated that there is almost no reverse flow at 1.5 times normal breathing. Reverse flow is cut off at 8 cmH2O and 13 cmH2O for 2 and 2.5 times respectively. Overall, when breathe load increases, reverse flow increases and when the pressure setting increases, the reverse flow drops. 146
Figure 6.1 Reverse flow under different combinations of breath load and CPAP pressure setting 6.2.1.2 Mask capacity vs. reverse flow The mask capacity in the model is adjustable. However, the model output shows that the distance of reverse flow is the same when mask capacity changes. This is because of the assumption of air incompressibility which means the distance of reverse flow is not influenced by the mask capacity. 6.2.2 Exhaled air re-inhalation In this section, the breath load, pressure setting, the resulted reverse flow and mask capacity are discussed with respect to their influences on the exhaled air re-breathing. 6.2.2.1 Exhaled air re-inhalation vs. breath load and pressure setting The percentage of exhaled air in inhalation vs. combination of breath load and pressure settings using the nasal mask is shown in Figure 6.2. 147
Page 1 and 2:
The Effects of CPAP Tube Reverse Fl
Page 3 and 4:
Acknowledgement First of all, I wou
Page 5 and 6:
When deep breathing induced reverse
Page 7 and 8:
2.4.1 Reverse flow calculation ....
Page 9 and 10:
5.3.1 Thermal dynamic model under s
Page 11 and 12:
XI.3 Steady state mask thermal bala
Page 13 and 14:
List of Figures Figure 1.1 Obstruct
Page 15 and 16:
Figure 5.10 Comparison between expe
Page 17 and 18:
Figure 6.13 Fluctuation of airflow
Page 19 and 20:
Table 5.3 Comparison of condensatio
Page 21 and 22:
Nomenclature Symbol Meaning of the
Page 23 and 24:
CMFeO CMFet C O C t Concentration o
Page 25 and 26:
m C 23 m Ca m cv m Cw m store m i m
Page 27 and 28:
Nu Cp Nu dir Nu Ti Nu To Nuwsn Nuws
Page 29 and 30:
QMor QMwst QTastn QTicn QTin Q
Page 31 and 32:
R Mic R Moc R Ticn R Toc R Torn Mas
Page 33 and 34:
V Capacity of the container m 3 V C
Page 35 and 36:
1.1 Background Chapter 1 Introducti
Page 37 and 38:
The MRD is worn in user’s mouth w
Page 39 and 40:
Figure 1.4 CPAP machine Figure 1.5
Page 41 and 42:
1.3 Literature survey A literature
Page 43 and 44:
CPAP fluid dynamic performance with
Page 45 and 46:
Chapter 2 Mathematical Modelling of
Page 47 and 48:
2.3 Fluid dynamic analysis This sec
Page 49 and 50:
If there are minor pressure drops,
Page 51 and 52:
Figure 2.6 Pressure sensor - Honeyw
Page 53 and 54:
The pressure readings were taken af
Page 55 and 56:
Figure 2.12 Experimental set up for
Page 57 and 58:
2.3.4 Chamber air space mass balanc
Page 59 and 60:
From the above analysis, the pressu
Page 61 and 62:
Figure 2.18 Full face mask and the
Page 63 and 64:
Inserting Eq. (2.26) and Eq. (2.27)
Page 65 and 66:
Where n( ) t is the airflow proper
Page 67 and 68:
However in reality, mixing turns ou
Page 69 and 70:
Chapter 3 Mathematical Modelling of
Page 71 and 72:
An Environment Control Chamber (Vö
Page 73 and 74:
Figure 3.4 Thermal enthalpy gain of
Page 75 and 76:
Figure 3.6 Heating element beneath
Page 77 and 78:
Figure 3.8 Chamber water heat balan
Page 79 and 80:
Table 3.1 Thermal resistance from h
Page 81 and 82:
3.3.1.2 Heat balance at the outer s
Page 83 and 84:
3.3.2 Heat flow from chamber water
Page 85 and 86:
through ADU which is a function of
Page 87 and 88:
It is assumed that the direct impac
Page 89 and 90:
Sc a a (3.47) Dwa Analogous to th
Page 91 and 92:
and keep them in gaseous status. On
Page 93 and 94:
through the walls and natural conve
Page 95 and 96:
Where d Ca is the specific humidity
Page 97 and 98:
TTa ( n1) is also considered as inl
Page 99 and 100:
R Torn 2 2 ATlor ( TTWn T )( TTWn
Page 101 and 102:
condensation severity but cannot ca
Page 103 and 104:
condensation has occurred at all or
Page 105 and 106:
The inlet is the air from HADT duri
Page 107 and 108:
3.9 Average temperature of inhaled
Page 109 and 110:
Table 4.1 Inputs to the fluid dynam
Page 111 and 112:
Figure 4.2 Simulink TM model for fl
Page 113 and 114:
Table 4.4 Outputs from the overall
Page 115 and 116:
Gain block after input 1 is to conv
Page 117 and 118:
Figure 4.7 Varying Transport Delay
Page 119 and 120:
4.2.5 Mask mixing calculation subsy
Page 121 and 122:
4.3 Computational model of thermal
Page 123 and 124:
Figure 4.11 Block diagram of CPAP t
Page 125 and 126:
Figure 4.13 Simulink TM model for t
Page 127 and 128:
The outputs are listed in Table 4.1
Page 129 and 130: The outputs are listed in Table 4.1
Page 131 and 132: Figure 4.16 Dynamic chamber-air the
Page 133 and 134: Figure 4.17 HADT lump thermal balan
Page 135 and 136: Figure 4.18 Steady state HADT lump
Page 137 and 138: Figure 4.19 HADT lump air dynamic f
Page 139 and 140: The outputs are listed in Table 4.2
Page 141 and 142: Figure 4.21Steady state mask full t
Page 143 and 144: 4 Temperature of airflow from HADT
Page 145 and 146: Average evaporation rate subsystem
Page 147 and 148: HADT and connects those upstream se
Page 149 and 150: The experiment was also carried out
Page 151 and 152: air flowing through the elbow, a ce
Page 153 and 154: expansion from the elbow to the mas
Page 155 and 156: Figure 5.12 Environmental control r
Page 157 and 158: Table 5.1 shows the combinations of
Page 159 and 160: Figure 5.17 Comparison of model out
Page 161 and 162: The comparison of experimental resu
Page 167 and 168: 5.3.1.4 Airflow temperature at the
Page 169 and 170: flow rate had been even further inc
Page 171 and 172: Figure 5.31 Comparison of condensat
Page 173 and 174: Table 5.3 Comparison of condensatio
Page 175 and 176: 3. The corrugated grooves on the HA
Page 177 and 178: 5.3.2.1 Validation of evaporation r
Page 179: The experiment observation showed t
Page 183 and 184: It can also be seen in Figure 6.2 t
Page 185 and 186: within the same period. However, wh
Page 187 and 188: Figure 6.6 Comparison of evaporatio
Page 189 and 190: Figure 6.8 Airflow velocity in HADT
Page 191 and 192: Figure 6.11 Airflow velocity in HAD
Page 193 and 194: In Figure 6.14 the blue curve repre
Page 195 and 196: 6.3.3.1.2 Comparison when heating e
Page 197 and 198: This vaporization potentiality (coi
Page 199 and 200: Figure 6.20 In-tube condensation of
Page 201 and 202: When using different sized masks, t
Page 203 and 204: Figure 6.23 Average specific humidi
Page 205 and 206: The average specific humidity in an
Page 207 and 208: Table 6.5 Comparison of average spe
Page 209 and 210: 6. The deep breathing and reverse f
Page 211 and 212: Appendices Appendix I Regression of
Page 213 and 214: Appendix I. Regression of the press
Page 215 and 216: Figure I. 1 Tested results and the
Page 217 and 218: Appendix II. Regression of the pres
Page 219 and 220: Table III. 2 Airflow temperature an
Page 221 and 222: Appendix IV. The corrugated HADT ou
Page 223 and 224: The total area of the complicated c
Page 225 and 226: Figure V. 1 Regression of saturated
Page 227 and 228: This ratio can be regressed against
Page 229 and 230: Appendix VII. Details of the CPAP f
Page 231 and 232:
VII.4 The mask pressure subsystem F
Page 233 and 234:
Inputs to this water-centred subsys
Page 235 and 236:
Input port number Input Unit 1 Heat
Page 237 and 238:
input 4 is the portion of impact ar
Page 239 and 240:
VIII.2.3 Water surface mass transfe
Page 241 and 242:
This subsystem also contains two su
Page 243 and 244:
VIII.2.5 Chamber wall 1 heat transf
Page 245 and 246:
Figure VIII. 13 Wall 1 outer surfac
Page 247 and 248:
Wall 2 and 3 inner surface temperat
Page 249 and 250:
Figure VIII. 17 Chamber wall 2 and
Page 251 and 252:
Inputs to this subsystem are listed
Page 253 and 254:
Appendix IX. Details of steady stat
Page 255 and 256:
Figure IX. 3 The HADT lump wall out
Page 257 and 258:
Appendix X. Details of HADT lump ai
Page 259 and 260:
2 Absolute value of airflow velocit
Page 261 and 262:
Figure X. 5 HADT lump inlet absolut
Page 263 and 264:
Figure XI. 2 Steady state mask mixi
Page 265 and 266:
Figure XI. 4 Steady state mask wall
Page 267 and 268:
Input port number Input Unit 1 Aver
Page 269 and 270:
Appendix XII. Details of mask air d
Page 271 and 272:
4 Length of the triangular plate in
Page 273 and 274:
8 Length of the triangular plate in
Page 275 and 276:
Appendix XIII. Details of the auxil
Page 277 and 278:
XIII.3 Breath load average subsyste
Page 279 and 280:
Figure XIII. 7 Average evaporation
Page 281 and 282:
XIV.1.2 Under normal ambient temper
Page 283 and 284:
XIV.2.3 Under high ambient temperat
Page 285 and 286:
XIV.4 Airflow temperature at the en
Page 287 and 288:
XIV.5.2 Under normal ambient temper
Page 289 and 290:
XIV.6.3 Under high ambient temperat
Page 291 and 292:
Appendix XVI. Regression of kinetic
Page 293 and 294:
Figure XVII. 2 Condensation/evapora
Page 295 and 296:
Figure XVIII. 2 Condensation/evapor
Page 297 and 298:
at point C. Right after that, here
Page 299 and 300:
Appendix XIX. Coefficient and param
Page 301 and 302:
Average water thermal conductivity
Page 303 and 304:
Appendix XXI. Fluid dynamic and the
Page 305 and 306:
The lung simulator drives the air.
Page 307 and 308:
Appendix XXII. Model user instructi
Page 309 and 310:
The input blocks and their values a
Page 311 and 312:
Dynamically fluctuating air tempera
Page 313 and 314:
References [1] Good sleep advice. W
Page 315 and 316:
[28] Schettino GPP, Chatmongkolchar
Page 317:
[60] Marek R, Straub J. Analysis of
show all

View/Open

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?