Area under curve for dynamic points on x-axis

Hi, I am trying to find the area under the curve from the start of the volume increase to one second after the start (example below with red, sorry its crude!). This is sensor data, so the points will be constantly changing, i.e. sometimes volume will start increasing at 5 seconds, other tests it will be 1 second. All the examples I have seen in the question are static points, whereas this will not be. Code below. Thank you.

ii = 0;
%q = zeros(1,1);
%t = zeros(1,1);
tic 
while toc < 10
    ii = ii + 1;
    
    v = readVoltage(a,'A0'); % Read voltage from sensor
    if v < 0.22, v = 0; % This is the 0 pressure outpur of sensor
    
    end
    
    v = v - 0.21; % Subtracting 0 pressure output from voltage output 
   
    p = (v/5)/0.09 - 0.04; % Converting to Kpa as per data sheet 
    if p < 0, p = 0; %Zeroing pressure if there is none and not letting it be a negative 
    
    end
    p = p * 1000; % Converting Kpa to pa
    a1 = 0.000415476; % Cross sectional Area of the first part of the Tube 
    a2 = 0.000028274; % Cross sectional Area of the second part of the Tube 
    r = 1.225; %Density of air
    c = a1/a2; % Ratio of Areas
    vf = a1 * sqrt( (2/r) * p/((c^2 -1) )); %Calculating Volumetric flow rate in M^3/s
    q(ii) = vf * 1000; %converting to Liters/s
    t(ii) = toc;
end 
q = q(1:ii);
t = t(1:ii);
   
Ar = trapz(t,q); %Calculating area under curve = total volume exhaled 
figure %Plotting curve and graph 
plot(t,q,'-o')
xlabel('Elapsed time(sec)')
ylabel('Volume Flow Rate (L/s)')
set(gca,'xlim',[t(1) t(ii)])
hold on
ha1 = area(t(t>0), q(t>0), 'FaceColor', 'g' )
Arstr = sprintf('Forced Volume = %0.5f Liters', Ar)
legend([ha1], Arstr)