why is there type 1 respiratory failure in asthma whereas dlco is raised?
Dlco tells you about diffusion of gas across alveolar membrane and it is normal in asthma so DLCO is either Normal or Increased. Reason of increase in DLCO is:
• Eosinophil release NO which cause pulm vasculature Dilatation
• Also to compensate hypoxic state, asthmatic pt tries to inhale deeply by creating excess negative intra thoracic press so that he can take extra air inside lungs. This increase preload so increases pulm blood flow, ultimately increases perfusion to all areas of lungs: this explains increased dlco. This can not happen in case of chronic bronchitis patient as they are already bloated(Blue bloaters) so diaphragmatic movement is limited so they cant ventilate properly so land up in T2 RF but asthmatic patient can easily Hyperventilate and washout all CO2 so land up mostly in T1 RF
just one more doubt if alveolar membrane is normal then along with co2 oxygen can also move through the alveolar membrane but in type 1 respi failure o2 doesn’t cross the membrane. so why exactly type 1 respiratory failure occurs here?
Group member because solubility of CO2 is more than that of O2 so to increase spo2 from hypoxic state to normal it takes time if he is ventilating by himself but by that time all CO2 gets diffused so you get low paO2 and low paCO2.
thank you so much